Resin compositions, films, and multilayer structures

Abstract

To provide a resin composition having excellent gas barrier property, particularly oxygen barrier property under high humidity.SOLUTION: A resin composition contains a hydrophilic resin and a metal compound and has a peak at 2θ=2 to 15° when measured by wide-angle X-ray diffraction using CuKα rays.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, and more particularly to a resin composition that can produce a film having high gas barrier properties under high humidity conditions. [Background technology]

[0002] Hydrophilic resins such as polyvinyl alcohol-based resins are widely used as packaging materials for various products, particularly foods and pharmaceuticals, where oxygen degradation must be suppressed, due to their excellent strength, transparency, and gas barrier properties. However, because hydrophilic resins have many hydroxyl groups, they are highly susceptible to the effects of humidity, and their gas barrier properties are significantly reduced in high-humidity environments.

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

[0004] Furthermore, Patent Document 2 describes a water-soluble polymer, a metal alkoxide, its hydrolysate, and at least one of the following: and a general formula (R 1 Si(OR 2 )3)n(However, R 1 R is an organic functional group. 2 A gas barrier layer forming composition is disclosed, which includes a compound represented as CH3, C2H5, or C2H4OCH3.

[0005] Furthermore, in Patent Document 3, a method for manufacturing a gas barrier laminate includes a step of forming a coating film containing zinc ions, at least one of a metal alkoxide and its hydrolyzate, and a water-soluble polymer on the surface of a base film or a laminate containing the same, and a step of forming a gas barrier layer on the above surface.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Disclosure of the Invention

Problems to be Solved by the Invention

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

[0008] Therefore, in the present invention, under such a background, an object is to provide a resin composition having excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

Means for Solving the Problems

[0009] However, the present inventors have found that a resin composition containing a hydrophilic resin and a metal compound and having an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα radiation has excellent gas barrier properties under high humidity conditions.

[0010] That is, the first gist of the present invention is a resin composition containing a hydrophilic resin and a metal compound, and having an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα radiation. Further, the second gist of the present invention is a film containing the resin composition of the first gist, and the third gist is a multilayer structure having at least one layer made of the film of the second gist.

Effects of the Invention

[0011] The resin composition of the present invention contains a hydrophilic resin and a metal compound, and has an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα radiation. Therefore, a film containing this resin composition has excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

Modes for Carrying Out the Invention

[0012] Hereinafter, the modes for carrying out the present invention will be specifically described, but the present invention is not limited thereto.

[0013] The resin composition of the present invention contains a hydrophilic resin and a metal compound, and has a peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα radiation. Hereinafter, each constituent will be described.

[0014] <Hydrophilic Resin> Specific examples of the hydrophilic resin used in the present invention include, for example, water-soluble resins such as vinyl alcohol-based resins, polysaccharides, acrylic resins, and polyether-based resins. The above hydrophilic resins may be used alone or in combination of two or more.

[0015] Further, the above hydrophilic resin preferably has the following characteristics when formed into a film, for example. Using the above hydrophilic resin, a film with a thickness of 30 μm was prepared, and when immersed in water at 25°C for 2 hours, the area change rate was 105% or more. The above area change rate can be calculated using the following formula. Area change rate (%) = Film area after immersion / Film area before immersion × 100 The following provides a detailed description of specific hydrophilic resins.

[0016] [Vinyl alcohol-based resin] The vinyl alcohol-based resins mentioned above exclude resins commonly known as ethylene-vinyl alcohol copolymer resins (ethylene content 20-60 mol%), and include, for example, polyvinyl alcohol (hereinafter referred to as "PVA")-based resins.

[0017] The above-mentioned PVA-based resin is usually preferably an unmodified PVA resin, but a modified PVA-based resin may also be used.

[0018] The above-mentioned unmodified PVA resin can usually be produced by polymerizing vinyl ester monomers and then saponifying them. Furthermore, the above-mentioned modified PVA resin can be produced by saponifying a polymer of vinyl ester monomers and other unsaturated monomers, or by post-modifying an unmodified PVA resin.

[0019] Examples of the vinyl ester monomers mentioned above 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 especially preferred. These are usually used individually, but multiple types may be used simultaneously as needed.

[0020] Other unsaturated monomers include, for example, 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 dialkyl 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 methallyl sulfonic acid, or their salts; alkyl vinyl ethers; N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, and polio Examples include polyoxyalkylene (meth)allyl ethers such as xyethylene (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 can be used individually or in combination of two or more. In addition, "(meth)allyl" means allyl or methallyl, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acrylic" means acrylic or methacrylic.

[0021] The above-mentioned PVA-based resin can be obtained by any known polymerization, saponification, and post-modification method.

[0022] The amount of other unsaturated monomers introduced and the amount of modification due to post-modification are set appropriately depending on the type of monomer, but are usually 15 mol% or less, and especially 10 mol% or less. If the amount introduced and the amount of modification are too high, the crystallinity of the PVA resin tends to decrease, and the gas barrier properties when it is made into a film tend to decrease.

[0023] The average degree of saponification of the above-mentioned PVA resin is typically 70-100 mol%, preferably 80-100 mol%, particularly preferably 85-100 mol%, and even more preferably 90-99.99 mol%. If the average degree of saponification is less than 70 mol%, the oxygen permeability under high humidity tends to increase. The above-mentioned average degree of saponification is measured in accordance with JIS K 6726 3.5.

[0024] The average degree of polymerization of the above-mentioned PVA resin is typically 100 to 4,000, preferably 200 to 3,000, and particularly preferably 300 to 2,500. If the average degree of polymerization is too low, mechanical properties such as film strength tend to decrease, and if it is too high, it tends to become difficult to handle, such as difficulty in creating an aqueous solution. The above-mentioned average degree of polymerization is measured in accordance with JIS K 6726.

[0025] Furthermore, two or more PVA-based resins with different characteristics such as modified species, modification amount, average degree of saponification, and average degree of polymerization may be used in combination.

[0026] The hydrophilic resin described above is preferably the main component of the resin composition of the present invention, and the content of the hydrophilic resin relative to the total resin composition is usually 80% by weight or more, preferably 90% by weight or more, and particularly preferably 95% by weight or more. The upper limit is usually 99.99% by weight.

[0027] [Polysaccharide] Examples of the polysaccharides mentioned above include starch and cellulose. Examples of the above-mentioned starches include natural starches such as corn starch and potato starch, etherified starch, esterified starch, cross-linked starch, grafted starch, roasted dextrin, enzyme-modified dextrin, pregelatinized starch, oxidized starch, and other modified starches. Examples of the cellulose mentioned above include carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, nitrocellulose, cationized cellulose, and metal salts thereof such as their sodium salts.

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

[0029] [Polyether resin] Examples of the polyether-based resins mentioned above include polyethylene glycol and polypropylene glycol.

[0030] Among the hydrophilic resins mentioned above, vinyl alcohol-based resins and polysaccharides are preferred due to their excellent gas barrier properties under high humidity, particularly their oxygen barrier properties. PVA-based resins and cellulose are especially preferred, and unmodified PVA resin is the most preferred.

[0031] <Metal compounds> The metal compounds used in this invention have a structure in which metal complexes are layered with specific interplanar spacings. Examples include metal-containing layered compounds such as layered compounds containing Zn as a metal species.

[0032] Examples of metal species contained in the above-mentioned metal compound include Zn, Co, Ni, and Si. These metal species may be present individually or in combination of two or more. Among these, Zn is preferred due to its excellent gas barrier properties, particularly its oxygen barrier properties, under high humidity conditions.

[0033] The above-mentioned metal compound consists of, for example, a compound having at least one metal selected from Zn, Co, Ni, and Si (hereinafter referred to as "metal-containing compound"), and is obtained by the method described later. Examples of the metal-containing compounds mentioned above include organic salts of metals and inorganic salts of metals.

[0034] Examples of organic acids that constitute the organic salts of the above metals include monovalent carboxylic acids such as acetic acid, divalent carboxylic acids such as succinic acid, oxalic acid, and tartaric acid, and trivalent or higher carboxylic acids such as citric acid and ethylenediaminetetraacetic acid. These may be used individually or in combination of two or more. Furthermore, the organic acid salt of the above metal may be a hydrate or an anhydrous form. As for the organic acid salts of the above metals, monovalent carboxylates of metals are preferred, and Zn acetate or its hydrate is particularly preferred, due to their excellent gas barrier properties under high humidity, especially oxygen barrier properties.

[0035] Examples of inorganic salts of the above-mentioned metals include metal fluorides, chlorides, bromides, and iodides. These may be used individually or in combination of two or more. As the inorganic salt of the above metal, metal chlorides are preferred, and Zn chloride or its hydrate is particularly preferred, due to their excellent gas barrier properties under high humidity, especially oxygen barrier properties.

[0036] As described above, the metal compound used in this invention has a structure in which the metal complex is layered with specific interplanar spacings. Therefore, when hydrophilic resin molecules or water molecules are present around the metal compound, the layers of the metal compound are separated, and it is presumed that these separated fine metal complex molecules interact with the hydrophilic resin at the molecular level, resulting in excellent gas barrier properties, particularly oxygen barrier properties.

[0037] The interlayer distance (distance between layers) of the above metal compound is preferably 0.01 to 50 nm, and more preferably 0.1 to 30 nm, from the viewpoint of interaction with the molecules of the hydrophilic resin and water molecules.

[0038] The molecular weight of the metal complex exfoliated from the above metal compound is preferably 100 to 10,000, and particularly preferably 200 to 2,000, in order to enable interaction at the molecular level with the hydrophilic resin.

[0039] Furthermore, from the standpoint of interaction with the molecules of the hydrophilic resin, it is preferable that the metal complex is hydrophilic. Furthermore, it is preferable that the above-mentioned metal complex does not decompose even after being left standing for 1,000 hours in an environment of 23°C and 80 RH%.

[0040] The metal content of the above-mentioned metal-containing compound is preferably 0.01 to 20% by weight, more preferably 0.1 to 8% by weight, and particularly preferably 0.2 to 5% by weight, relative to the resin composition. If the content of the metal compound is too low, the gas barrier properties, especially the oxygen barrier properties, tend to decrease under high humidity conditions. If the content of the metal compound is too high, the material tends to whiten and lose transparency when made into a film or the like. If the resin composition contains multiple metal compounds of different metal types, the total amount of metal compounds contained in the resin composition shall be considered as the content. Furthermore, the content of the above-mentioned metal compounds can be determined by a standard addition method using ICP-MS.

[0041] [Other ingredients] The resin composition of the present invention may contain additives commonly used in hydrophilic resins, such as heat stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, drying agents, antiblocking agents, flame retardants, crosslinking agents, curing agents, foaming agents, nucleating agents, antifogging agents, biodegradable additives, silane coupling agents, oxygen absorbers, etc., to the extent that they do not impair the effects of the present invention. These can be used individually or in combination of two or more.

[0042] <<Resin composition>> The resin composition of the present invention contains the above-mentioned hydrophilic resin and a metal compound, and exhibits an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα rays. The peak appearing at the low angle of 2θ = 2 to 15° is due to the added metal-containing compound being converted into a metal compound, and the peak originating from that metal compound.

[0043] In this invention, due to its excellent gas barrier properties under high humidity, particularly its oxygen barrier properties, the X-ray diffraction peak is present at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα rays. Furthermore, it is preferable that the peak is present at 2θ = 2 to 9°, and particularly preferable that the peak is present at 2θ = 3 to 8°.

[0044] The presence of X-ray diffraction peaks at 2θ = 2 to 15° when measured using CuKα radiation suggests the formation of a layered metal compound. Furthermore, it is presumed that the layered structure of this metal compound interacts with the hydrophilic resin, increasing the polarity of the resin composition, which in turn provides excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

[0045] The above 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 Total time: 30 minutes Wavelength: CuKα line (Kα1 and Kα2 are not separated) Detector position: 2θ = 10° X-ray incident angle: θ=0.3° Condition for one-dimensionalization in the 2θ direction: 2θ = 1 to 35°, azimuth angle (chi) = -95 to -85°; Condition for one-dimensionalization in the azimuth angle direction: 2θ = 3.5 to 4.5°, azimuth angle (chi) = -180 to 0°. As the sample used for the wide-angle X-ray diffraction, the resin composition in the form of a film may be used as it is. Also, when the resin composition is laminated with other substrates, if the resin composition layer can be peeled off, the resin composition layer is peeled off for measurement, and if it cannot be peeled off, measurement may be performed in the state laminated with other substrates. In addition, at the time of measurement, the thickness of the peeled resin composition layer (film) is preferably 30 μm or more, and if the film thickness is insufficient, the film may be laminated.

[0046] Also, the resin composition of the present invention preferably satisfies the following formula (1) with respect to the difference between the second virial coefficient (A2) of the resin composition obtained from static light scattering measurement and the second virial coefficient (A 2,0 ) of the hydrophilic resin in the resin composition. ΔA2 = A2 - A 2,0 > 0 ···(1)

[0047] The difference (A2 - A 2,0 ) between the second virial coefficient (A2) of the resin composition and the second virial coefficient (A 2,0 ) of the hydrophilic resin in the resin composition is preferably greater than 0, more preferably A2 - A 2,0 > 0.00005, particularly preferably A2 - A 2,0 > 0.0001, and especially preferably A2 - A 2,0 > 0.0005. The upper limit is usually 0.01 and preferably 0.1. When A2 - A 2,0 is 0 or less, the gas barrier property, particularly the oxygen barrier property, tends to decrease under high humidity.

[0048] The above A2 and A 2,0 are obtained as follows. Using the resin composition as a solvent, 5 levels of measurement solutions were prepared with solid content concentrations ranging from 0.1 to 1 mg / mL using hexafluoroisopropanol. Static light scattering measurements were performed at a temperature of 25°C, and the second virial coefficient A2 and weight-average molecular weight Mw of the resin composition were obtained from the Zimm plot. b We seek. Furthermore, the second virial coefficient A of the hydrophilic resin can be determined using the same method. x and weight-average molecular weight Mw a We seek. Furthermore, the hydrophilic resin mentioned above is the same as the hydrophilic resin contained in the resin composition; that is, it is the hydrophilic resin before the resin composition contained the metal compound. Since the resin composition of the present invention contains a hydrophilic resin and a metal compound, the weight-average molecular weight of the hydrophilic resin in the resin composition is equal to the apparent weight-average molecular weight (Mw) of the hydrophilic resin. a Unlike the first method, the second virial coefficient A obtained by static light scattering measurement of hydrophilic resins is different. x The second virial coefficient A of the hydrophilic resin in the resin composition 2,0 This cannot be done. Therefore, the second virial coefficient A of the hydrophilic resin in the resin composition is determined by the following procedure. 2,0 We seek. 1) Find the constant q from equation (2) below. q=A X / Mw a ν ...(2) A x : Second virial coefficient obtained by static light scattering measurement of hydrophilic resin Mw a Weight-average molecular weight obtained by static light scattering measurement of hydrophilic resins ν :-0.25 Here, since ν in a good solvent is usually -0.25, we perform the calculation using ν = -0.25. 2) The obtained constant q and the weight-average molecular weight Mw obtained by static light scattering measurement of the resin composition b Using the following formula (3), the second virial coefficient A of the hydrophilic resin is obtained. 2,0 We will find the value of ν below, using -0.25 as in equation (2). A 2,0 =q × Mwb ν ...(3)

[0049] The resin composition of the present invention having the above-described characteristics can be obtained, for example, by the following preparation method (i).

[0050] <Preparation method (i)> (i-1) A step of blending a hydrophilic resin, a metal-containing compound, and a solvent, and then heating and stirring the mixture. (i-2) After heating the above solution, a film is formed and then dried to obtain a film. (i-3) A step of leaving the above film standing under high humidity. The following details each step.

[0051] [Step (i-1)] In step (i-1) above, the metal-containing compound reacts in the solvent and undergoes a structural change, thereby generating the metal compound.

[0052] The amount of the above-mentioned metal-containing compound blended is typically 0.01 to 20 parts by weight, preferably 0.1 to 8 parts by weight, and particularly preferably 0.2 to 5 parts by weight, in terms of metal, per 100 parts by weight of hydrophilic resin.

[0053] The solvent mentioned above is not particularly limited as long as it is a solvent that dissolves the hydrophilic resin, but water is usually used. In addition, in order to shorten the drying time after film formation, for example, lower alcohols with 1 to 5 carbon atoms such as methanol, ethanol, propanol, n-butanol, and isopropanol may be used within a range in which the hydrophilic resin can dissolve. The amount of the above solvent is typically 100 to 9,900 parts by weight, preferably 400 to 1,900 parts by weight, per 100 parts by weight of the hydrophilic resin.

[0054] Furthermore, the order in which the hydrophilic resin, metal-containing compound, and solvent are blended is not particularly limited; they may all be blended together at once or sequentially. Among these, blending the hydrophilic resin and metal-containing compound with the solvent is preferable from the viewpoint of reactivity.

[0055] Furthermore, the heating temperature is typically 20 to 100°C, preferably 40 to 95°C, and particularly preferably 80 to 95°C. If the heating temperature is too low, the hydrophilic resin tends not to dissolve completely, and if the heating temperature is too high, the metal-containing compound tends to decompose.

[0056] The reaction time is usually 0.5 to 5 hours, preferably 1 to 4 hours, and particularly preferably 2 to 3 hours. If the reaction time is too short, the reaction tends not to proceed sufficiently, and if the reaction time is too long, the reaction yield does not improve and economic efficiency tends to decrease. Furthermore, heating should be done at atmospheric pressure.

[0057] The metal compound is obtained through the process described in (i-1) above. It is presumed that the hydrogen bonding between the hydroxyl groups of this metal compound and the hydroxyl groups of the hydrophilic resin, or the interaction between the metal species of the metal compound and the hydrophilic resin, results in excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions.

[0058] [Step (i-2)] The above step (i-2) is a step of forming a film by forming a solution containing a hydrophilic resin and a metal compound.

[0059] The solid content concentration of the solution containing the hydrophilic resin and metal compound used for film formation is typically 0.5 to 30% by weight, preferably 5 to 20% by weight.

[0060] As for the film formation method described above, known methods such as melt extrusion, casting, and coating can be used, and a method suitable for forming the film of the hydrophilic resin used should be adopted. For example, if the hydrophilic resin is a PVA-based resin, coating or casting methods are preferred in terms of accuracy of film thickness. Furthermore, the film after the above-mentioned film formation process may be subjected to stretching operations such as uniaxial stretching or biaxial stretching, as needed.

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

[0062] The above film may be a single-layer film or a multilayer structure. The multilayer structure preferably has at least one layer made of the above film. Furthermore, the multilayer structure may be formed by laminating the manufactured films or by laminating them with other base resins.

[0063] Examples of the above-mentioned base resins include polyethylene resins such as linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymers; polypropylene resins such as polypropylene and propylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymers; (unmodified) polyolefin resins such as polybutene, polypentene, and polycyclic olefin resins (polymers having a cyclic olefin structure in at least one of the main chain and side chains); and these polyolefins can be modified with unsaturated carboxylic acids or Examples include polyolefin resins in a broad sense, such as modified olefin resins including unsaturated carboxylic acid-modified polyolefin resins grafted with esters, 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, aromatic or aliphatic polyketones, etc. Furthermore, these base resins may be subjected to surface treatments such as corona treatment.

[0064] The thickness of the above-mentioned film is typically 1 to 200 μm, preferably 1 to 100 μm, and particularly preferably 1 to 50 μm. If the prepared film is a multilayer structure, the total thickness of all films obtained by preparing a solution containing a hydrophilic resin and a metal compound is considered the film thickness.

[0065] [Step (i-3)] Step (i-3) above involves leaving the film obtained above to stand under high humidity. By going through this step, a film with excellent gas barrier properties, particularly oxygen barrier properties, under high humidity can be obtained. The principle by which such an effect is obtained is not clear, but it is presumed that by leaving the film to stand under high humidity, the metal compounds dispersed in the film interact with the hydrophilic resin or become localized on the surface of the film.

[0066] In this invention, high humidity means 20±5℃ and 90±10%RH. Furthermore, the standing time is usually 70 hours or more, preferably 300 hours or more, and more preferably 600 hours or more. The upper limit for the standing time is usually 1,000 hours.

[0067] By following the above steps, the resin composition (film made of the resin composition) of the present invention is obtained, which has an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα rays. Furthermore, the method for preparing the resin composition is not limited to the above preparation method (i). For example, in step (i-1), a metal organic acid salt may be reacted with a strong base (e.g., hydroxides of alkali metals or alkaline earth metals) to first produce a metal compound, and then this compound may be blended with a hydrophilic resin.

[0068] The oxygen permeability of the film containing the obtained resin composition is 80 cc·3 μm / m² from the viewpoint of gas barrier properties, particularly oxygen barrier properties. 2 It is preferable that the pressure be less than or equal to 70cc·3μm / m². 2It is more preferable that the pressure be less than or equal to day·atm, and 55cc·3μm / m² 2 It is even more preferable that the temperature is less than or equal to 40cc·3μm / m². 2 It is even more preferable that the pressure be less than or equal to 35cc·3μm / m². 2 It is even more preferable that the temperature is less than or equal to 30cc·3μm / m². 2 It is even more preferable that the pressure be less than or equal to day·atm, which is 25cc·3μm / m². 2 It is even more preferable that the temperature is less than or equal to 20cc·3μm / m². 2 It is even more preferable that the pressure be less than or equal to 10cc·3μm / m². 2 It is particularly preferable that the oxygen permeability is less than or equal to 0.day·atm. Note that the above oxygen permeability was measured under conditions of 23°C and 80% RH, and the lower limit of oxygen permeability is usually 0cc·3μm / m 2 The oxygen permeability is ・day·atm. Furthermore, the above oxygen permeability can be determined using an oxygen permeability measuring device.

[0069] Films containing the resin composition of the present invention exhibit excellent transparency, which is significantly superior to that of 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 the HAZE value measured in accordance with the JIS K7361-1 standard. For example, ten 50mm x 50mm test pieces are cut from the film, measured using a haze meter (NDH-4000, manufactured by Nippon Denshoku Co., Ltd.), and the average value of the ten pieces is taken as the haze (%).

[0070] The resin composition and film containing the resin composition of the present invention are useful as packaging materials, and can be suitably used as packaging materials for food, pharmaceuticals, and the like. [Examples]

[0071] 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 unless it exceeds the gist of the invention. Hereinafter, "parts" means by weight.

[0072] Prior to the examples, the following hydrophilic resins were prepared.

[0073] [Hydrophilic resin] • PVA-1 (unmodified PVA resin, average degree of polymerization 300, average degree of saponification 99 mol%)

[0074] <Example 1> 100 parts of PVA-1 and 0.3 parts of Zn acetate (in terms of metal equivalent) were added to 900 parts of water, and the mixture was heated to 90°C while stirring to dissolve. After that, the mixture was stirred for 3 hours while maintaining 90°C, and then cooled to room temperature (23°C) to prepare a solution containing a hydrophilic resin and a metal compound. The solution prepared above was applied to a 38 μm thick corona-treated PET film using a bar coater and dried in a hot air dryer at 120°C for 5 minutes. The resulting coated film was then left to stand for 72 hours at 23°C and 80% RH to obtain the resin composition film (3 μm thick) of Example 1.

[0075] The resin composition film obtained above was peeled from the PET film and laminated to a thickness of 30 μm or more to obtain the sample. X-ray diffraction measurements were performed on this sample under the following conditions. The results are shown in Table 1 below. [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 Total 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 = 1 to 35°, Chi = -95 to -85° One-dimensionalization in the azimuth direction: 2θ = 3.5~4.5°, azimuth angle (chi) = -180~0°. If a peak was observed in the range of 2θ = 3~10° when one-dimensionalized in the 2θ direction, one-dimensionalization in the azimuth direction was not performed. If no peak was observed when one-dimensionalized in the 2θ direction, one-dimensionalization was performed in the range of -180~0° in the azimuth direction within the range of 2θ = 3.5~4.5°, and the azimuth dependence of the diffraction intensity was checked. In this case, if a diffraction peak was observed at an azimuth angle of -90°, it was determined that a complex was present in the resin composition.

[0076] [Oxygen barrier properties] The oxygen permeability of the obtained resin composition film was measured using an oxygen permeability meter (OX-TRAN100A, MOCON Corporation) under conditions of 23°C and 80% RH. The results are shown in Table 1 below.

[0077] <Example 2> In Example 1, the resin composition film of Example 2 was obtained in the same manner as in Example 1, except that the amount of Zn acetate added was adjusted to 1 part in terms of metal equivalent. Subsequently, the X-ray diffraction of the obtained resin composition film was measured in the same manner as in Example 1. The oxygen barrier properties were also evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[0078] <Example 3> In Example 1, the resin composition film of Example 3 was obtained in the same manner as in Example 1, except that the amount of Zn acetate added was 5 parts in terms of metal equivalent. Subsequently, the X-ray diffraction of the obtained resin composition film was measured in the same manner as in Example 1. The oxygen barrier properties were also evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[0079] <Comparative Example 1> A hydrophilic resin film of Comparative Example 1 was obtained in the same manner as in Example 1, except that Zn acetate was not added. Subsequently, the X-ray diffraction of the obtained hydrophilic resin film was measured in the same manner as in Example 1. The oxygen barrier properties were also evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[0080] <Comparative Example 2> A resin composition film of Comparative Example 2 was obtained in the same manner as in Example 1, except that zinc oxide was added in the same manner as in Example 1, in the same manner as in Example 1, except that zinc acetate was replaced with zinc oxide in the same manner as in Example 1. Subsequently, the X-ray diffraction of the obtained resin composition film was measured in the same manner as in Example 1. The oxygen barrier properties were also evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[0081] <Comparative Example 3> A resin composition film of Comparative Example 3 was obtained in the same manner as in Example 1, except that zinc chloride was added in the same manner as in Example 1, in the same manner as in Example 1, except that zinc acetate was replaced with zinc chloride in the same manner as in Example 1. Subsequently, the X-ray diffraction of the obtained resin composition was measured in the same manner as in Example 1. The oxygen barrier properties were also evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[0082] [Table 1]

[0083] As can be seen from Table 1 above, Examples 1 to 3, which contained a hydrophilic resin and a metal compound and showed a peak at low angles (2θ = 2 to 15°) in X-ray diffraction measurements, exhibited excellent oxygen barrier properties under high humidity conditions. On the other hand, Comparative Examples 1-3, which did not have a peak at low angles in X-ray diffraction measurements, all exhibited inferior oxygen barrier properties. [Industrial applicability]

[0084] The resin composition of the present invention is useful as a packaging material because it has excellent gas barrier properties, particularly oxygen barrier properties, under high humidity conditions, and can be suitably used as a packaging material for food, pharmaceuticals, and the like.

Claims

1. A resin composition comprising a hydrophilic resin and a metal-containing layered compound, wherein the metal-equivalent content of the metal-containing layered compound is 0.01 to 20% by weight relative to the resin composition, the metal species of the metal-containing layered compound is at least one selected from Zn, Co, and Ni, and the resin composition is characterized in that it has an X-ray diffraction peak at 2θ = 2 to 15° when measured by wide-angle X-ray diffraction using CuKα rays.

2. The resin composition according to claim 1, characterized in that the hydrophilic resin is a polyvinyl alcohol-based resin (excluding polyvinyl alcohol-based resins containing carboxyl groups).

3. The resin composition according to claim 1 or 2, characterized in that the metal content of the metal-containing layered compound is 0.1 to 8% by weight relative to the resin composition.

4. A film characterized by containing the resin composition described in any one of claims 1 to 3.

5. The oxygen permeability of the above film under conditions of 23°C and 80% RH is 80 cc / 3 μm / m². 2 The film according to claim 4, characterized in that it is less than or equal to day atm.

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

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