JP4620945B2 - Coating liquid and film production method using the same - Google Patents

Description

The present invention relates to a gas barrier film which is a dry coating film of a coating liquid containing a carboxyl group-containing polymer and polyvalent metal compound particles, and more particularly, gelation due to early reaction is suppressed, and the polyvalent metal compound The present invention relates to a gas barrier film which is a dry coating film of a coating liquid having excellent dispersion stability of particles. The coating liquid of the present invention is suitable for film formation. By applying the coating liquid of the present invention onto a substrate and drying, it is excellent in gas barrier properties, moisture resistance, water resistance, hot water resistance, and water vapor resistance, and gas barrier properties under high humidity conditions as well as under low humidity conditions It is possible to produce a gas barrier film (hereinafter also referred to as “film”) having excellent resistance .

  The polyvinyl alcohol film is excellent in gas barrier properties, but has insufficient moisture resistance and water resistance, and the humidity dependency of the gas barrier properties is large, and the oxygen gas barrier property is likely to be remarkably lowered by moisture absorption. Although the ethylene-vinyl alcohol copolymer film has relatively good gas barrier properties and water resistance, the humidity dependency of the gas barrier properties is large. Poly (meth) acrylic acid film exhibits excellent gas barrier properties under dry conditions such as 0% relative humidity, but is inferior in moisture resistance, water resistance, hot water resistance, and water vapor resistance. Remarkably deteriorates.

  Conventionally, by heat-treating a coating film formed from a mixture of poly (meth) acrylic acid or a partially neutralized product thereof and polyvinyl alcohol or saccharide, it has excellent gas barrier properties, water resistance, hot water resistance, and humidity dependence of gas barrier properties A method for obtaining a film having low properties has been proposed (see, for example, Patent Documents 1-4). However, in these methods, in order to obtain a gas barrier film, it is generally necessary to heat-treat the coating film made of the mixture at a high temperature of 100 ° C. or higher for a relatively long time. Moreover, the said film produces | generates the ester bond between the said polymers by heat processing, As a result, it is highly bridge | crosslinked and it is difficult to discard and reuse after use.

  A coating film made of a mixture of poly (meth) acrylic acid and polyvinyl alcohol or saccharide is heat-treated to produce a film, and then the film is immersed in a medium containing an alkali metal or an alkaline earth metal, There has been proposed a method for producing a gas barrier film with improved hot water resistance and water vapor resistance by introducing an ionic bond between (meth) acrylic acid and a metal (see, for example, Patent Document 5).

  Further, a metal compound layer is formed on the surface of a coating film formed from a mixture of poly (meth) acrylic acid or a partially neutralized product thereof and polyvinyl alcohol or saccharide, and ions are transferred by the migration of the metal compound into the coating film. There has been proposed a method of forming a bond to produce a film excellent in gas barrier properties, hot water resistance, and water vapor resistance (see, for example, Patent Document 6).

  In each of the films disclosed in Patent Documents 5 and 6, an ionic cross-linking (also referred to as metal cross-linking) structure including ionic bonds is introduced in addition to a cross-linking structure including ester bonds generated by heat treatment.

  However, the method for introducing ionic bonds using the metal compounds disclosed in Patent Documents 5 and 6 also requires that the coating film having the above composition be heat-treated under high temperature conditions, in addition to the crosslinked structure by ester bonds. Therefore, it is difficult to dispose of and recycle the film.

  On the other hand, in the technical field of dispersants for pigments for coated paper, calcium (co) polymers of α, β-monoethylenically unsaturated carboxylic acids and / or their alkali metal salts or ammonium salts A dispersing agent for coated paper pigments has been proposed, which comprises an aqueous solution obtained by reacting a polyvalent metal compound such as an alkali metal salt or ammonia and maintaining the pH at 4 or higher (see, for example, Patent Document 7). However, this aqueous solution is used as a pigment dispersant and is not used for forming a film.

  Also proposed is an alkali-soluble film comprising a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl monomer, and a polyvalent metal. (For example, refer to Patent Document 8). This alkali-soluble film is produced by an extrusion method or a coating method using a coating agent prepared by mixing a solution in which the polymer is dissolved in a solvent such as alcohol or water and a solution of a polyvalent metal compound. can do. However, in this method, gelation due to the reaction between the polymer and the polyvalent metal compound is likely to occur, and it is difficult to prepare a coating solution having excellent temporal stability, and the homogeneity of the resulting film is also impaired. easy.

Japanese Patent No. 2736600 Japanese Patent No. 2811540 Japanese Patent No. 3203287 Japanese Patent No. 3340780 Japanese Patent Laid-Open No. 10-237180 JP 2000-931 A JP 54-82416 A JP-A-8-176316

  The object of the present invention is excellent in gas barrier properties, moisture resistance, water resistance, hot water resistance, and water vapor resistance obtained by ion-crosslinking a carboxyl group-containing polymer with a polyvalent metal, and not only in low humidity conditions but also in high humidity conditions. An object of the present invention is to provide a coating liquid capable of forming a film having excellent gas barrier properties.

  In particular, an object of the present invention is to provide the coating liquid that is suppressed in gelation due to early reaction and is excellent in stability over time and uniform film formability.

  Another object of the present invention is to provide a method for producing a film having excellent properties by applying the coating liquid onto a substrate and drying it.

  As a result of diligent research to achieve the above object, the present inventors have carried out ion-crosslinking of a carboxyl group-containing polymer such as poly (meth) acrylic acid with a polyvalent metal, thereby providing gas barrier properties, moisture resistance, and water resistance. It has been found that a film excellent in heat resistance, hot water resistance and water vapor resistance can be obtained.

  However, since the carboxyl group-containing polymer and the polyvalent metal compound are gelated when melt-kneaded, they cannot be melt-molded into a film. Moreover, since the carboxyl group-containing polymer and the polyvalent metal compound react immediately in the state of an aqueous solution to gel or precipitate, it is possible to obtain a stable coating solution that can form a film by a coating method. It is extremely difficult.

  Addition of a volatile base such as ammonia to an aqueous solution containing a carboxyl group-containing polymer and a polyvalent metal compound can suppress gelation due to early reaction to some extent, but generation of ammonia during the coating and drying processes. Problems such as environmental pollution due to odor and residual ammonia odor on the produced film occur. The same problem occurs when a volatile amine compound is used instead of ammonia.

  Even when an organic solvent is used instead of water as the medium, the carboxyl group-containing polymer and the polyvalent metal compound react with each other due to the presence of a small amount of water, causing gelation or precipitation. And uniformity are easily lost. This tendency becomes stronger when a coating solution is prepared by mixing a solution of a carboxyl group-containing polymer and a solution of a polyvalent metal compound.

  Therefore, as a result of further research, the present inventors uniformly dissolved the carboxyl group-containing polymer in an organic solvent in which the polymer can be dissolved, while dispersing the polyvalent metal compound as particles in the organic solvent. In this case, by adding a surfactant to increase the dispersion stability of the polyvalent metal compound particles and reducing the water content until the water content becomes 1,000 ppm or less, the occurrence of gelation and precipitation is suppressed. The inventors have found that a coating liquid in which polyvalent metal compound particles are finely and stably dispersed can be obtained.

  When the coating liquid of the present invention is applied onto a substrate and dried, a film having excellent gas barrier properties, moisture resistance, water resistance, hot water resistance, water vapor resistance, and excellent gas barrier properties even under high humidity conditions can be obtained. Can do. Formation of the film of the present invention does not require heat treatment for a long time at a high temperature required for the formation of the ester bond. Moreover, since the film of the present invention is ion-crosslinked (metal-crosslinked), it can be discarded and reused by solubilization. The present invention has been completed based on these findings.

According to the present invention, it contains a carboxyl group-containing polymer (A), polyvalent metal compound particles (B), a surfactant (C), and an organic solvent (D), and has a water content of 1,000 ppm or less. A gas barrier film which is a dry coating film of a coating liquid , wherein the thickness of the gas barrier film is 0.01 to 100 μm, and the gas barrier film has a temperature of 30 ° C. and a relative humidity of 80%. A gas barrier film having a measured oxygen permeability of 1,000 cm ³ / (m ² · day · MPa) or less is provided. Further, according to the present invention, the polymer contains a carboxyl group-containing polymer (A), polyvalent metal compound particles (B), a surfactant (C), and an organic solvent (D), and has a water content of 1,000 ppm or less. The coating liquid which is is apply | coated on a base material, and the manufacturing method of the gas-barrier film which dries is provided.

  According to the present invention, the occurrence of gelation and precipitation due to the early crosslinking reaction between a carboxyl group-containing polymer and a polyvalent metal compound is suppressed, and a stable coating liquid in which polyvalent metal compound particles are uniformly dispersed is obtained. be able to. In addition, by using the coating liquid of the present invention, a film having excellent gas barrier properties, moisture resistance, water resistance, hot water resistance, water vapor resistance and excellent gas barrier properties even under high humidity conditions can be obtained.

1. Carboxyl group-containing polymer (A) :
The carboxyl group-containing polymer used in the present invention is a polymer having two or more carboxyl groups in the molecule, and is sometimes referred to as a “polycarboxylic acid polymer”. As the carboxyl group-containing polymer, a homopolymer of a carboxyl group-containing unsaturated monomer, a copolymer of a carboxyl group-containing unsaturated monomer, a carboxyl group-containing unsaturated monomer and other polymerizable monomers And a polysaccharide containing a carboxyl group in the molecule (also referred to as “acidic polysaccharide”).

  The carboxyl group includes not only a free carboxyl group but also an acid anhydride group (specifically, a dicarboxylic acid anhydride group). The acid anhydride group may be partially opened to be a carboxyl group. A part of the carboxyl group may be neutralized with an alkali. In this case, the degree of neutralization is preferably 20% or less.

  Further, a graft polymer obtained by graft polymerization of a carboxyl group-containing unsaturated monomer to a polymer such as polyolefin that does not contain a carboxyl group can also be used as the carboxyl group-containing polymer. A polymer obtained by hydrolyzing a polymer having a hydrolyzable ester group such as an alkoxycarbonyl group (for example, methoxycarbonyl group) and converting it to a carboxyl group can also be used.

  As the carboxyl group-containing unsaturated monomer, α, β-monoethylenically unsaturated carboxylic acid is preferable. Accordingly, the carboxyl group-containing polymer includes an α, β-monoethylenically unsaturated carboxylic acid homopolymer, a copolymer of two or more α, β-monoethylenically unsaturated carboxylic acids, and α, β. -Copolymers of monoethylenically unsaturated carboxylic acids and other polymerizable monomers are included. The other polymerizable monomer is typically an ethylenically unsaturated monomer.

  Examples of the α, β-monoethylenically unsaturated carboxylic acid include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; maleic anhydride Unsaturated dicarboxylic anhydrides such as itaconic anhydride; mixtures of two or more of these. Among these, at least one α, β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid is preferable. More preferred is at least one α, β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acids and maleic acid.

  Examples of other polymerizable monomers copolymerizable with α, β-monoethylenically unsaturated carboxylic acid, particularly ethylenically unsaturated monomers include, for example, ethylene; propylene, 1-butene, 1-pentene, 1 Α-olefins such as hexene and 1-octene; saturated carboxylic acid vinyl esters such as vinyl acetate; alkyl acrylates such as methyl acrylate and ethyl acrylate; alkyl methacrylates such as methyl methacrylate and ethyl methacrylate Esters; Chlorine-containing vinyl monomers such as vinyl chloride and vinylidene chloride; Fluorine-containing vinyl monomers such as vinyl fluoride and vinylidene fluoride; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Styrene, α-methyl Aromatic vinyl monomers such as styrene; alkyl itaconic esters; It can gel. These ethylenically unsaturated monomers can be used alone or in combination of two or more. When the carboxyl group-containing polymer is a copolymer of an α, β-monoethylenically unsaturated carboxylic acid and a saturated carboxylic acid vinyl ester such as vinyl acetate, the copolymer is saponified to form a saturated carboxylic acid. Copolymers obtained by converting acid vinyl ester units into vinyl alcohol units can also be used.

  Examples of the carboxyl group-containing polysaccharide include acidic polysaccharides having a carboxyl group in the molecule such as alginic acid, carboxymethylcellulose, and pectin. These acidic polysaccharides can be used alone or in combination of two or more. Acidic polysaccharides can also be used in combination with (co) polymers of α, β-monoethylenically unsaturated carboxylic acids.

  When the carboxyl group-containing polymer used in the present invention is a copolymer of an α, β-monoethylenically unsaturated carboxylic acid and another ethylenically unsaturated monomer, the gas barrier property of the resulting film, From the viewpoint of hot water resistance and water vapor resistance, the copolymer composition is preferably such that the α, β-monoethylenically unsaturated carboxylic acid monomer composition is 60 mol% or more, and 80 mol% or more. More preferably, it is particularly preferably 90 mol% or more.

  The carboxyl group-containing polymer is excellent in gas barrier properties, moisture resistance, water resistance, hot water resistance, water vapor resistance, and is easy to obtain a film excellent in gas barrier properties under high humidity conditions. A homopolymer or copolymer obtained by polymerization of only ethylenically unsaturated carboxylic acid is preferred. When the carboxyl group-containing polymer is a (co) polymer consisting only of α, β-monoethylenically unsaturated carboxylic acid, preferred specific examples thereof are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and A homopolymer, a copolymer, and a mixture of two or more thereof obtained by polymerization of at least one α, β-monoethylenically unsaturated carboxylic acid selected from the group consisting of itaconic acid. Among these, a homopolymer and a copolymer of at least one α, β-monoethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, and maleic acid are more preferable.

  As the carboxyl group-containing polymer, polyacrylic acid, polymethacrylic acid, polymaleic acid, and a mixture of two or more thereof are particularly preferable. As the acidic polysaccharide, alginic acid is preferred. Among these, polyacrylic acid is particularly preferable because it is relatively easy to obtain and a film having excellent physical properties can be easily obtained.

  The molecular weight of the carboxyl group-containing polymer is not particularly limited, but the number average molecular weight is preferably in the range of 2,000 to 10,000,000 from the viewpoint of film formability and film properties, and is preferably 5,000 to 1. More preferably, it is in the range of 1,000,000, more preferably in the range of 10,000 to 500,000. The number average molecular weight can be measured by gel permeation chromatography (GPC). In GPC measurement, the number average molecular weight of a polymer is generally measured in terms of standard polystyrene.

  As the polymer constituting the film of the present invention, in addition to the carboxyl group-containing polymer, other polymers are mixed and used as long as the properties of the film such as gas barrier properties, hot water resistance, and water vapor resistance are not impaired. be able to. In many cases, it is preferable to use only carboxyl group-containing polymers.

The carboxyl group-containing polymer used as a raw material preferably has an oxygen permeability coefficient of 1000 cm ³ · μm / (m ²⁾ measured under dry conditions of 30 ° C. and 0% relative humidity with respect to a film formed using the polymer alone. · Day · MPa) or less, more preferably 500 cm ³ · µm / (m ² · day · MPa) or less, particularly preferably 100 cm ³ · µm / (m ² · day · MPa) or less. If the oxygen permeability coefficient of the carboxyl group-containing polymer used as a raw material is too low, the film obtained using the coating liquid of the present invention has poor gas barrier properties, stability against hot water or water vapor (hot water resistance, water vapor resistance). It tends to be enough.

  The oxygen permeability coefficient of the carboxyl group-containing polymer used as a raw material can be determined by the following method. A carboxyl group-containing polymer is dissolved in water to prepare an aqueous solution having a concentration of 10% by weight. This aqueous solution is applied onto a plastic film substrate using a bar coater and dried to prepare a coating film on which a carboxyl group-containing polymer layer having a dry thickness of 1 μm is formed. The resulting coating film is measured for oxygen permeability under conditions of 30 ° C. and 0% relative humidity. A plastic film having a relatively large oxygen permeability is used as the plastic film substrate. If the oxygen permeability of the coating film having a dry coating film of the obtained carboxyl group-containing polymer is 1/10 or less of the oxygen permeability of the plastic film alone used as the substrate, the oxygen permeation The measured value of the degree can be regarded substantially as the oxygen permeability of the carboxyl group-containing polymer layer alone.

Since the measured value obtained as described above is the oxygen permeability of the carboxyl group-containing polymer layer having a thickness of 1 μm, it can be converted into an oxygen permeability coefficient by multiplying the measured value by 1 μm. The oxygen permeability can be measured using, for example, an oxygen transmission tester OXTRAN TM2 / 20 manufactured by Modern Control. The method for measuring oxygen permeability is carried out in accordance with B method (isobaric method) defined in JIS K 7126 and ASTM D 3985-81. The measured value can be expressed in the unit cm ³ (STP) / (m ² · day · MPa), but STP means standard conditions (0 ° C., 1 atm) for defining the volume of oxygen. Therefore, normally, STP is omitted.

2. Multivalent metal compound particles (B) :
The polyvalent metal compound particles used in the present invention are particles of a polyvalent metal atom having a metal ion valence of 2 or more and a polyvalent metal compound. Therefore, the polyvalent metal compound used in the present invention includes a polyvalent metal atom alone. Specific examples of the polyvalent metal include metals of Group 2A of the periodic table such as beryllium, magnesium, and calcium; transition metals such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, and zinc; and aluminum. Although it can, it is not limited to these.

  Specific examples of the polyvalent metal compound include, but are not limited to, oxides, hydroxides, carbonates, organic acid salts, and inorganic acid salts of polyvalent metals. Examples of organic acid salts include acetate, oxalate, citrate, lactate, phosphate, phosphite, hypophosphite, stearate, and monoethylenically unsaturated carboxylate. For example, but not limited to. Examples of inorganic acid salts include, but are not limited to, chlorides, sulfates, and nitrates. Alkyl alkoxides of polyvalent metals can also be used as polyvalent metal compounds. These polyvalent metal compounds can be used alone or in combination of two or more.

  Among polyvalent metal compounds, compounds of beryllium, magnesium, calcium, copper, cobalt, nickel, zinc, aluminum, and zirconium are preferable from the viewpoint of dispersion stability of the coating liquid and gas barrier properties of the film formed from the coating liquid. More preferred are compounds of divalent metals such as beryllium, magnesium, calcium, copper, zinc, cobalt, and nickel.

  Preferred divalent metal compounds include, for example, oxides such as zinc oxide, magnesium oxide, copper oxide, nickel oxide and cobalt oxide; carbonates such as calcium carbonate; organic acid salts such as calcium lactate, zinc lactate and calcium acrylate Alkoxides such as magnesium methoxide; but are not limited thereto.

  The polyvalent metal compound is used as particles, and the particle shape is maintained even in the coating liquid. The average particle diameter of the polyvalent metal compound particles is 10 nm to 10 μm (10,000 nm) as the average particle diameter in the coating liquid from the viewpoint of dispersion stability of the coating liquid and gas barrier properties of the film formed from the coating liquid. The range is preferably 12 nm to 1 μm (1,000 nm), more preferably 15 to 500 nm, and particularly preferably 15 to 50 nm.

  If the average particle size of the polyvalent metal compound particles in the coating solution is too large, the film thickness uniformity, surface flatness, and ion crosslinking reactivity with the carboxyl group-containing polymer will be insufficient. easy. If the average particle diameter of the polyvalent metal compound particles is too small, the ion crosslinking reaction with the carboxyl group-containing polymer may proceed at an early stage, and it is difficult to uniformly disperse ultrafine particles of less than 10 nm in that state. It is.

  In the case of a dry solid, the average particle diameter of the polyvalent metal compound particles can be measured by measuring and counting using a scanning electron microscope or a transmission electron microscope. The average particle diameter of the polyvalent metal compound particles in the coating liquid can be measured by a light scattering method [Reference: “Fine Particle Engineering System”, Volume I, pages 362-365, Fuji Techno System (2001)]. .

  The polyvalent metal compound particles in the coating liquid exist as primary particles, secondary particles, or a mixture thereof. In many cases, it is presumed that they exist as secondary particles in view of the average particle diameter.

3. Surfactant (C) :
In the present invention, a surfactant is used to enhance the dispersibility of the polyvalent metal compound particles. The surfactant is a compound having both a hydrophilic group and a lipophilic group in the molecule, and includes anionic, cationic and amphoteric ionic surfactants and nonionic surfactants. Then, any surfactant can be used.

  Examples of the anionic surfactant include a carboxylic acid type, a sulfonic acid type, a sulfate ester type, and a phosphate ester type. Examples of the carboxylic acid type include aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acyl sarcosinates, and N-acyl glutamates. Examples of the sulfonic acid type include dialkyl sulfosuccinate, alkane sulfonate, alpha olefin sulfonate, linear alkyl benzene sulfonate, alkyl (branched) benzene sulfonate, naphthalene sulfonate-formaldehyde condensate, Examples thereof include alkylnaphthalene sulfonate and N-methyl-N-acyl taurate. Examples of the sulfate ester type include alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fat and oil sulfate esters. Examples of the phosphate ester type include an alkyl phosphate type, a polyoxyethylene alkyl ether phosphate, and a polyoxyethylene alkylphenyl ether phosphate.

  Examples of the cationic surfactant include an alkylamine salt type and a quaternary ammonium salt type. Examples of the alkylamine salt type include monoalkylamine salts, dialkylamine salts, and trialkylamine salts. Examples of the quaternary ammonium salt type include halogenated (chloride, bromide or iodide) alkyltrimethylammonium salts and alkylbenzalkonium chloride.

  Examples of the amphoteric surfactant include a carboxybetaine type, a 2-alkylimidazoline derivative type, a glycine type, and an amine oxide type. Examples of the carboxybetaine type include alkyl betaines and fatty acid amidopropyl betaines. Examples of the derivative type of 2-alkylimidazoline include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine. Examples of the glycine type include alkyl or dialkyldiethylenetriaminoacetic acid. Examples of the amino oxide type include alkyl amine oxide.

  Examples of the nonionic surfactant include an ester type, an ether type, an ester ether type, and an alkanolamide type. Examples of the ester type include glycerin fatty acid ester, sorbitan fatty acid ester, and sucrose fatty acid ester. Examples of the ether type include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene polyoxypropylene glycol. Examples of the ester ether type include fatty acid polyethylene glycol and fatty acid polyoxyethylene sorbitan. Examples of the alkanolamide type include fatty acid alkanolamides.

  A surfactant having a polymer skeleton such as a styrene-acrylic acid copolymer can also be used.

  Among these surfactants, anionic surfactants such as phosphate esters and surfactants having a polymer skeleton such as styrene-acrylic acid copolymer are preferable.

4). Organic solvent (D) :
In the present invention, an organic solvent is used as a medium for the coating liquid. Generally, a polar organic solvent that dissolves a carboxyl group-containing polymer is used as the organic solvent, but an organic solvent that does not have a polar group (a hetero atom or an atomic group having a hetero atom) is used in combination with the polar organic solvent. May be.

  Examples of the organic solvent that can be preferably used in the present invention include alcohols such as methanol, ethanol, isopropanol, n-propanol, and n-butanol; dimethyl sulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide. And polar organic solvents such as N-methyl-2-pyrrolidone, tetramethylurea, hexamethylphosphoric triamide, and γ-butyrolactone.

  In addition to the polar organic solvent, hydrocarbons such as benzene, toluene, xylene, hexane, heptane, and octane; ketones such as acetone and methyl ethyl ketone; halogenated hydrocarbons such as dichloromethane; esters such as methyl acetate; Ethers such as diethyl ether; etc. can be used as appropriate. Generally, hydrocarbons such as benzene having no polar group are used in combination with a polar organic solvent.

5. Composition:
The coating liquid of the present invention contains a carboxyl group-containing polymer (A), polyvalent metal compound particles (B), a surfactant (C), and an organic solvent (D), and the polyvalent metal compound particles are dispersed. It is a dispersion liquid.

  The ratio of the polyvalent metal compound particles (B) to the carboxyl group-containing polymer (A) is the sum of the polyvalent metal compound particles (B) with respect to the total carboxyl groups (At) of the carboxyl group-containing polymer (A) (Bt It is preferable that the chemical equivalent of This chemical equivalent is more preferably 0.8 or more, particularly preferably 1.0 or more. The upper limit of this chemical equivalent is usually 10.0, preferably 2.0. If the chemical equivalent of the polyvalent metal compound particles (B) with respect to the carboxyl groups of the carboxyl group-containing polymer (A) is too small, various properties such as gas barrier properties, hot water resistance, and water vapor resistance of the film formed from the coating solution will be obtained. Shows a downward trend.

  The chemical equivalent can be determined as follows, for example. The case where the carboxyl group-containing polymer is polyacrylic acid and the polyvalent metal compound is magnesium oxide will be described as an example. When the mass of polyacrylic acid is 100 g, the molecular weight of the monomer unit of polyacrylic acid is 72, and since it has one carboxyl group per molecule of monomer, the carboxyl group in 100 g of polyacrylic acid The amount is 1.39 mol. At this time, 1.0 chemical equivalent with respect to 100 g of polyacrylic acid is the quantity of the base which neutralizes 1.39 mol. When 0.6 chemical equivalent of magnesium oxide is mixed with 100 g of polyacrylic acid, it is sufficient to add magnesium oxide to neutralize 0.834 mol of carboxyl groups. Since the valence of magnesium is divalent and the molecular weight of magnesium oxide is 40, 0.6 chemical equivalent of magnesium oxide to 100 g of polyacrylic acid is 16.68 g (0.417 mol).

  The organic solvent is used in an amount sufficient to uniformly dissolve the carboxyl group-containing polymer and to uniformly disperse the polyvalent metal compound particles. Therefore, as the organic solvent, those capable of dissolving the carboxyl group-containing polymer but not substantially dissolving the polyvalent metal compound and dispersing it in the form of particles are used.

  The surfactant is used in an amount sufficient to stably disperse the polyvalent metal compound particles, and is generally 0.0001 to 70% by weight, preferably 0.001 to 60% by weight, based on the total amount of the coating liquid. More preferably, it is contained in a proportion of 0.1 to 50% by weight.

  If the surfactant is not added, it becomes difficult to disperse the polyvalent metal compound particles in the coating solution so that the average particle diameter is sufficiently small. As a result, the polyvalent metal compound particles are uniformly dispersed. It is difficult to obtain a coating liquid, and it becomes difficult to form a coating film having a uniform film thickness when applied onto a substrate.

6). Moisture content in coating solution :
The water content in the coating solution of the present invention is adjusted to be 1,000 ppm or less from the viewpoint of dispersion stability of the coating solution. The water content of the coating liquid is preferably 500 ppm or less, more preferably 200 ppm or less, and particularly preferably 100 ppm or less.

  If the water content of the coating solution is too high, an ionic crosslinking reaction between the carboxyl group-containing polymer and the polyvalent metal compound particles will occur early, the entire coating solution will gel, or a precipitate resulting from the early reaction will be generated. To do. When gelation occurs or precipitates are formed, it becomes impossible to apply a coating solution to form a coating film, or to form a coating film having a uniform film thickness and composition. As a result, even if a film is obtained, the uniformity of the film thickness is impaired, and various physical properties such as gas barrier properties and mechanical physical properties are likely to vary depending on the location.

  The water content of the coating solution was measured by a moisture measurement method by the Karl Fischer method according to a conventional method [Reference: “Analytical Chemistry Handbook” Maruzen Co., Ltd., published in 1981, page 37].

7). Manufacturing method of coating solution :
In many cases, the carboxyl group-containing polymer can be made into a high-concentration solution by using water as a medium. For example, polyacrylic acid is generally marketed in the form of an aqueous solution. In addition, the carboxyl group-containing polymer solution obtained by polymerization in a non-aqueous solvent such as alcohol often contains water having a concentration exceeding 1,000 ppm.

  Therefore, in order to produce a coating solution having a low water content, it is first necessary to prepare an organic solvent solution of a carboxyl group-containing polymer having a low water content. For example, when a commercially available polyacrylic acid aqueous solution is used as a starting material, water is removed together with the alcohol by adding an alcohol such as isopropanol to the polyacrylic acid aqueous solution and concentrating under reduced pressure. An acid alcohol solution is prepared. In the case of using an organic solvent other than alcohol, moisture can be removed by the same treatment.

  On the other hand, the polyvalent metal compound particles are used as an organic solvent dispersion having a low water content. It is preferable that an appropriate amount of a surfactant is present in the dispersion to increase the dispersibility and dispersion stability of the polyvalent metal compound particles. By mixing an organic solvent solution of a carboxyl group-containing polymer and an organic solvent dispersion of a polyvalent metal compound, a coating solution having a low water content can be prepared. A surfactant may be added during the preparation of the coating solution.

  In the coating liquid of the present invention, the total concentration of components other than the organic solvent is preferably in the range of 0.1 to 60% by weight, more preferably 0.5 to 25% by weight, and particularly preferably 1 to 10% by weight. It is preferable to obtain a coating film and a film having a desired film thickness with good workability.

  In the coating liquid of the present invention, other polymers, thickeners, stabilizers, ultraviolet absorbers, antiblocking agents, softening agents, inorganic layered compounds (for example, montmorillonite), colorants (dyes, Various additives such as pigments) can be contained.

8). Film production method :
In order to produce a film using the coating liquid of the present invention, the coating liquid may be applied on a substrate and dried. The material of the substrate is not particularly limited, and examples thereof include plastic, metal, paper, glass, and ceramics. The form of the substrate generally has a flat surface such as a film or sheet (hereinafter simply referred to as “film”) or a plate, but if desired, a container such as a bottle, cup, tray or bag; It may have a three-dimensional structure.

  As the substrate, a plastic film is preferably used. The type of plastic constituting the plastic film is not particularly limited. For example, olefins such as high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, poly-4-methylpentene, and cyclic polyolefin are used. Polymers and acid-modified products thereof; polyvinyl acetate, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, and vinyl acetate polymers such as polyvinyl alcohol and modified products thereof; polyethylene terephthalate, polybutylene Polyesters such as terephthalate and polyethylene naphthalate; Aliphatic polyesters such as poly ε-caprolactone, polyhydroxybutyrate, and polyhydroxyvalerate; Nylon 6, nylon 66, nylon 12, Niro Polyamides such as 6/66 copolymer, nylon 6/12 copolymer, metaxylene adipamide / nylon 6 copolymer; polyethers such as polyethylene glycol, polyethersulfone, polyphenylene sulfide, polyphenylene oxide; poly Halogenated polymers such as vinyl chloride, polyvinylidene chloride, polyvinyl fluoride, and polyvinylidene fluoride; acrylic polymers such as polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, and polyacrylonitrile; polyimide resin; Other binder resins for paints such as alkyd resin, melamine resin, acrylic resin, nitrified cotton, urethane resin, polyester resin, phenol resin, amino resin, fluorine resin, epoxy resin; cellulose, starch And natural polymer compounds such as flour, pullulan, chitin, chitosan, glucomannan, agarose, and gelatin.

  As the substrate, unstretched films and stretched films made of these plastics are preferable, but containers such as bottles, cups, trays, and bags made of these plastics can be used if desired.

  In addition, a thin film made of an inorganic compound such as silicon oxide, aluminum oxide, aluminum, or silicon nitride; a metal compound; or the like is formed on a surface of a film (including a sheet) or a container made of plastics. What was formed by the plating method can be used as a base material. In general, thin films made of these inorganic compounds and metal compounds are used for the purpose of providing gas barrier properties.

  The coating liquid of the present invention is applied to the surface of the substrate as described above. As a coating method, a spray method, a dipping method, a coating method using a coater, a printing method using a printing machine, and the like are arbitrary. When applying using a coater or printer, gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure and offset gravure; reverse roll coater, micro gravure coater, air knife coater, dip coater, bar coater Various systems such as a comma coater and a die coater can be employed.

  The drying of the coating film is not particularly limited as long as it is a method capable of obtaining a solid film by evaporating an organic solvent, for example, a method of natural drying in an atmospheric environment, in an oven set to a predetermined temperature. Examples thereof include a drying method and a method using other arbitrary drying means. As other drying methods, dryers such as arch dryers, floating dryers, drum dryers and infrared dryers attached to various coaters are typical.

  The drying conditions can be arbitrarily set as long as the coating film, film, substrate and the like are not damaged by heat. Drying is performed until the organic solvent in the coating film is substantially removed.

  It is estimated that the carboxyl group-containing polymer contained in the film reacts with the polyvalent metal compound particles during or after drying to introduce an ionic cross-linked structure. In order to allow the ionic crosslinking reaction to proceed sufficiently, after drying, the film is preferably at least 20%, more preferably 40-100% relative humidity, and preferably a temperature of 5-200 ° C, more preferably 20-150 ° C. It is preferable to make it age | cure | ripen about 1 second to 10 days on these conditions.

  The film can be used by being peeled from the substrate, but can also be used as a multilayer structure integrated with the substrate if desired. For example, a multilayer film can be obtained by using a plastic film as a base material, applying the coating liquid of the present invention thereon and drying it to form a film.

The thickness of the full Irumu is not particularly limited, moldability at the time of film formation, in view of handling of the film, preferably 0.001Myuemu～1mm, more preferably 0.01 to 100 [mu] m, particularly preferably 0. It is in the range of 1 to 10 μm. The thickness of the film of the present invention is in the range of 0.01 to 100 μm.

Since the film obtained by the production method of the present invention is ionically crosslinked, it is excellent in moisture resistance, water resistance, hot water resistance, and water vapor resistance. The film of the present invention is excellent in gas barrier properties not only under low humidity conditions but also under high humidity conditions. The film of the present invention preferably has an oxygen permeability measured under conditions of 30 ° C. and a relative humidity of 80%, preferably 1,000 cm ³ / (m ² · day · MPa) or less, more preferably 500 cm ³ / (m ² · day · MPa) or less, particularly preferably 100 cm ³ / (m ² · day · MPa) or less.

  Since the film of the present invention exhibits solubility under strongly acidic or strongly alkaline conditions, it can be easily discarded and reused.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Measurement methods and evaluation methods for physical properties and characteristics in the present invention are as follows.

(1) Average particle diameter of polyvalent metal compound particles:
The average particle diameter of the polyvalent metal compound particles in the coating solution was measured by a light scattering method.

(2) Moisture content:
The water content was measured by a moisture measurement method using the Karl Fischer method.

(3) Oxygen permeability of the film:
The oxygen permeability of the film was measured in an atmosphere at a temperature of 30 ° C. and a relative humidity of 80% using an oxygen permeation tester (manufactured by Modern control, OXTRAN 2/20).

(4) Coating liquid properties:
When the coating liquid is visually observed, gelation occurs when it is gelled, when the polyvalent metal compound is poorly dispersible and does not form a uniform dispersion, it is “bad”. The case where there was no dispersion failure and a uniform dispersion was formed was evaluated as “good”.

[Example 1]
400 g of polyacrylic acid aqueous solution (manufactured by Toagosei Co., Ltd., concentration 25% by weight, number average molecular weight 200,000) was concentrated under reduced pressure to 110 g, and further reduced in pressure while adding isopropanol (hereinafter abbreviated as “IPA”). Concentration was performed. The concentrate was heated and dissolved in IPA to prepare a polyacrylic acid solution having a concentration of 10% by weight (water content 50 ppm). The oxygen permeability coefficient measured for the film formed using this polyacrylic acid alone at 30 ° C. and a relative humidity of 0% was 50 cm ³ · μm / (m ² · day · MPa). It was.

  100 g of zinc oxide (ZnO) dispersion (manufactured by Sumitomo Osaka Cement Co., Ltd., solvent toluene, concentration 30% by weight, average particle diameter 20 nm, phosphoric acid ester 3% by weight) diluted with 400 g of IPA, ZnO concentration 6% by weight A dispersion was prepared.

  470 g of ZnO dispersion was added to 500 g of the polyacrylic acid solution and mixed to obtain a coating solution containing polyacrylic acid, ZnO, phosphate ester (surfactant), IPA, and toluene. The equivalent of ZnO to polyacrylic acid in this coating solution was 1.0. The water content in the coating solution was 50 ppm.

  The coating solution thus obtained was applied to a polyethylene terephthalate (PET) film having a thickness of 12 μm using a tabletop coater (manufactured by RK PRINT-COAT instruments, K303PROFERR), and the solvent was evaporated using a dryer. The film was obtained by drying. The oxygen permeability of the obtained film was measured. The results are shown in Table 1.

[Example 2]
A coating solution was prepared in the same manner as in Example 1 except that ethanol was used instead of isopropanol (IPA) in Example 1. The equivalent of ZnO to polyacrylic acid was 1.0. The water content in the coating solution was 50 ppm. Using this coating solution, a film was formed on a PET film in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
400 g of polyacrylic acid aqueous solution (manufactured by Toagosei Co., Ltd., concentration 25% by weight, number average molecular weight 200,000) was concentrated under reduced pressure to 110 g, and further reduced in pressure while adding isopropanol (hereinafter abbreviated as “IPA”). Concentration was performed. The concentrate was heated and dissolved in IPA to prepare a polyacrylic acid solution having a concentration of 10% by weight (water content 50 ppm).

  Calcium carbonate fine particles (manufactured by Shiraishi Kogyo Co., Ltd., Shirahika O) were dispersed in IPA using a styrene-acrylic acid copolymer [manufactured by Dainichi Seika Kogyo Co., Ltd.] as a surfactant (calcium carbonate 10 wt. %, 10% by weight of surfactant). The average particle size of calcium carbonate was 100 nm.

  A coating solution was prepared by adding 350 g of calcium carbonate dispersion to 500 g of the polyacrylic acid solution and mixing them. The equivalent of calcium carbonate to polyacrylic acid was 1.0. The water content in the coating solution was 70 ppm.

  The obtained coating liquid was applied onto a PET film having a thickness of 12 μm using a tabletop coater (manufactured by RK PRINT-COAT instruments, K303PROFERR), and the solvent was evaporated and dried using a dryer to obtain a film. . The results are shown in Table 1.

[Comparative Example 1]
In order to observe the influence of the water content, a coating liquid was prepared in the same manner as in Example 1 except that water was added to the coating liquid prepared in Example 1 to adjust the water content to 2,000 ppm. . When the polyacrylic acid solution and the ZnO dispersion were mixed, the mixture immediately gelled. This coating solution could not be applied because the gel was deposited. The results are shown in Table 1.

[Comparative Example 2]
In Example 3, a coating solution was prepared in the same manner except that a styrene-acrylic acid copolymer [manufactured by Dainichi Seika Kogyo Co., Ltd.] was not used as the surfactant. The average particle size of calcium carbonate in the coating solution was 2,000 nm. The coating liquid had poor uniform dispersibility of calcium carbonate, and the oxygen gas permeability of the obtained film was the same level as that of the PET film of the substrate, and the gas barrier property was poor.

  The film of the present invention is excellent in gas barrier properties, moisture resistance, water resistance, hot water resistance, and water vapor resistance, and is excellent in gas barrier properties under high humidity conditions as well as under low humidity conditions. And can be suitably used in fields such as packaging materials.

Claims (8)

Dry coating film of coating liquid containing carboxyl group-containing polymer (A), polyvalent metal compound particles (B), surfactant (C), and organic solvent (D), and having a water content of 1,000 ppm or less The gas barrier film has a thickness of 0.01 to 100 μm, and the oxygen permeability measured under the conditions of 30 ° C. and 80% relative humidity of the gas barrier film. A gas barrier film that is 1,000 cm ³ / (m ² · day · MPa) or less . The ratio of the polyvalent metal compound particles (B) to the carboxyl group-containing polymer (A) in the coating liquid is such that the polyvalent metal compound particles (B) with respect to the total carboxyl group (At) of the carboxyl group-containing polymer (A). The gas barrier film according to claim 1, wherein the chemical equivalent of the total (Bt) is 0.6 or more. The carboxyl group-containing polymer (A) in the coating solution is a homopolymer of a carboxyl group-containing unsaturated monomer, a copolymer of a carboxyl group-containing unsaturated monomer, a carboxyl group-containing unsaturated monomer, and others. The gas barrier film according to claim 1 or 2, which is a copolymer with a polymerizable monomer, a carboxyl group-containing polysaccharide, or a mixture of two or more thereof. The carboxyl group-containing unsaturated monomer constituting the carboxyl group-containing polymer (A) in the coating liquid is at least selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. The gas barrier film according to claim 3, which is one kind of α, β-monoethylenically unsaturated carboxylic acid. The gas barrier film according to any one of claims 1 to 4, wherein the polyvalent metal compound particles (B) in the coating liquid are dispersed as particles having an average particle diameter of 10 nm to 10 µm. The gas barrier film according to any one of claims 1 to 5, wherein the polyvalent metal compound particles (B) in the coating liquid are divalent metal compound particles. A coating solution containing a carboxyl group-containing polymer (A), polyvalent metal compound particles (B), a surfactant (C), and an organic solvent (D) and having a water content of 1,000 ppm or less is formed on the substrate. The method for producing a gas barrier film according to claim 1, wherein the gas barrier film is applied to and dried. A gas barrier multilayer film comprising a multilayer structure in which the gas barrier film according to claim 1 is integrated with a plastic film as a substrate.