JP7593633B2 - Aqueous dispersions, laminates, gas barrier agents, gas barrier films, coating agents, coating films, adhesives, and heat sealants - Google Patents

Description

The present invention relates to an aqueous dispersion, a laminate, a gas barrier agent, a gas barrier film, a coating agent, a coating film, an adhesive, and a heat sealant.

Industrial clays are used in a wide range of fields, including as thickeners, binders, rheology modifiers, inorganic binders, civil engineering muds, waterproofing materials, and cosmetic ingredients.
Smectite is known as a type of industrial clay. The general crystal structure of smectite consists of a 2:1 layer structure of unit crystal layers, in which alumina octahedron sheets are sandwiched between silicic acid tetrahedron sheets, in which a silicic acid network spreads. In many cases, part of the aluminum, which is the central atom of the alumina octahedron sheet, is replaced by magnesium in this crystal layer, which makes the crystal layer negatively charged, and cations are incorporated between the layers to neutralize this negative charge. In addition, since these cations can be exchanged, smectite exhibits cation exchangeability. The amount of exchangeable cations is called the cation exchange capacity (CEC) and is one of the indicators of smectite's properties.

It is known that when smectite is subjected to a heat treatment, the interlayer cations (protons, sodium ions, potassium ions, lithium ions, cesium ions, ammonium ions, calcium ions, magnesium ions, etc.) are fixed as a result of dehydration. When the cations are fixed, the basic properties of the smectite, such as dispersion stability in water, viscosity, swelling, and cation exchangeability, decrease. In particular, lithium ions are firmly fixed by applying a temperature of about 200°C or higher. Therefore, smectite containing a certain amount or more of lithium ions between the layers has a significant decrease in cation exchangeability due to the above heat treatment, and does not return to its original state even when water is added, resulting in a significant decrease in water dispersibility. It is believed that the fixation of lithium ions by the above heat treatment occurs when lithium ions present between the layers move to vacant sites in the octahedral sheets of the smectite crystal. This phenomenon is called the Hofmann-Klemen effect and is used to control the layer charge density (see, for example, Non-Patent Document 1). Lithium smectite, in which lithium ions are fixed (lithium fixed smectite), has a significantly lower affinity for water and is actually water repellent, so its use as a material for forming highly water-resistant films is being considered.

Since lithium-fixed smectite has extremely low water dispersibility, it is difficult to form a clay film using its aqueous dispersion (slurry). On the other hand, if the water dispersibility of lithium-fixed smectite can be increased, it becomes possible to prepare a slurry of the lithium-fixed smectite, and a clay film with excellent water resistance can be formed simply by applying and drying the slurry. In fact, several techniques for increasing the water dispersibility of lithium-fixed smectite have been reported.
For example, Patent Document 1 describes that a slurry containing specific amounts of lithium-loaded montmorillonite having a cation exchange capacity of 50 meq/100 g or less, ammonia, water, and a polar organic solvent having a formamide group has excellent dispersion stability of the lithium-loaded montmorillonite. Patent Document 2 describes that a slurry containing specific amounts of lithium-loaded montmorillonite having a cation exchange capacity of 50 meq/100 g or less, ammonia, water, and an organic solvent selected from at least acetonitrile and methyl ethyl ketone has excellent dispersion stability of the lithium-loaded montmorillonite.
On the other hand, when forming a clay film, a film formed from a clay mineral alone is inferior in flexibility and is prone to film defects due to impact, etc., and its industrial range of use is limited. Therefore, a composite film combining a clay mineral such as smectite with a resin has been proposed. For example, Patent Document 3 describes a laminated film with excellent oxygen barrier properties obtained by coating a substrate with a liquid resin composition containing a neutralized product of a polyester polyol having a carboxyl group, which is a polycondensation product of a polycarboxylic acid such as an ortho-oriented aromatic dicarboxylic acid and a polyhydric alcohol, and lithium-fixed smectite.

JP 2015-147300 A JP 2018-83728 A JP 2020-7420 A

"Clay Handbook", Third Edition, Edited by the Clay Science Society of Japan, May 2009, p. 125

In order to maintain or stabilize the functions of the products and electronic components inside, packaging materials for industrial products, etc., and housings for various electronic components, oxygen barrier properties, water vapor barrier properties, etc. are required. Lithium-fixed smectite is suitable as a material for forming a film with such barrier properties. On the other hand, in order to form a film that is industrially versatile and reliable, it is considered to combine lithium-fixed smectite with resin, etc., as described above. However, after extensive research by the present inventors, it has become clear that it is difficult to fully bring out the gas barrier properties of lithium-fixed smectite and achieve the desired gas barrier properties in a film formed by combining lithium-fixed smectite with a resin.

The present invention aims to provide an aqueous dispersion containing lithium-fixed smectite and a polymer, which, when used as a film-forming material, can produce a film that is excellent in mechanical properties such as flexibility and impact resistance while fully utilizing the gas barrier properties inherent to lithium-fixed smectite. The present invention also aims to provide a laminate having a layer formed using the aqueous dispersion, a gas barrier agent made of the aqueous dispersion, a gas barrier film having a layer formed using the aqueous dispersion, a coating agent made of the aqueous dispersion, a coating film having a layer formed using the aqueous dispersion, an adhesive made of the aqueous dispersion, and a heat seal agent made of the aqueous dispersion.

The above-mentioned object of the present invention has been achieved by the following means.
[1]
An aqueous dispersion comprising particles of a polymer having a polyolefin structure and having a polar group, and a lithium-fixed smectite.
[2]
The aqueous dispersion according to [1], wherein the lithium-fixed smectite has a cation exchange capacity of 1 to 70 meq/100 g.
[3]
The aqueous dispersion according to [1] or [2], wherein the polar group is an acidic group or a salt thereof.
[4]
The aqueous dispersion according to any one of [1] to [3], wherein the content of the lithium-fixed smectite in the solid content of the aqueous dispersion is 3 to 80 mass %.
[5]
A laminate having a layer formed using the aqueous dispersion according to any one of [1] to [4].
[6]
A laminate having a layer containing a complex of a polymer having a polyolefin structure and a polar group, and a lithium-fixed smectite.
[7]
A gas barrier agent comprising the aqueous dispersion according to any one of [1] to [4].
[8]
A gas barrier film having a layer formed using the aqueous dispersion according to any one of [1] to [4].
[9]
A coating agent comprising the aqueous dispersion according to any one of [1] to [4].
[10]
A coating film having a layer formed using the aqueous dispersion according to any one of [1] to [4].
[11]
An adhesive comprising the aqueous dispersion according to any one of [1] to [4].
[12]
A heat-sealing agent comprising the aqueous dispersion according to any one of [1] to [4].

The aqueous dispersion of the present invention contains lithium-fixed smectite and a polymer, and by using the aqueous dispersion as a film-forming material, the resulting film can be excellent in mechanical properties such as flexibility and impact resistance while fully bringing out the gas barrier properties inherent to lithium-fixed smectite. The laminate, gas barrier film, and coating film of the present invention are excellent in mechanical properties such as flexibility and impact resistance while fully bringing out the gas barrier properties inherent to lithium-fixed smectite. In addition, the gas barrier agent, coating agent, adhesive, and heat sealant of the present invention are suitable as gas barrier films, coating films, binding materials, or sealing materials that are excellent in mechanical properties such as flexibility and impact resistance while fully bringing out the gas barrier properties inherent to lithium-fixed smectite.

Preferred embodiments of the present invention are described below, but the present invention is not limited to these embodiments except as specified in the present invention.

[Aqueous Dispersion]
The aqueous dispersion of the present invention contains particles of a polymer having a polyolefin structure and a polar group (hereinafter referred to as polymer particles), and lithium-fixed smectite.
Each component constituting the aqueous dispersion of the present invention will be described in detail below.

<Polymer Particles>
The polymer particles contained in the aqueous dispersion of the present invention have a constituent polymer that has a polyolefin structure and has a polar group. The fact that the polymer has a polyolefin structure means that a part of the polymer has a structure consisting of a homopolymer of an olefin (an unsaturated hydrocarbon having an ethylenically unsaturated group) or a copolymer of two or more kinds of olefins. The proportion of the polyolefin structure in the polymer is preferably 30% by mass or more, more preferably 50% by mass or more, and also preferably 70% by mass or more. Examples of the polyolefin structure include structures obtained by polymerization of α-olefins, such as a polyethylene structure, a polypropylene structure, and a polybutene structure, and a polyethylene structure is preferred.

The polar group of the polymer means a group containing one or more heteroatoms (atoms other than carbon atoms). Among them, a group consisting of an acidic group or a salt thereof is preferred. Examples of the acidic group include a carboxy group, a sulfo group, a phosphate group, and a phosphite group, and among them, a carboxy group is preferred. Examples of the salt of the acidic group include salts of alkali metals such as lithium, sodium, and potassium, salts of alkaline earth metals such as magnesium, calcium, strontium, and barium, and salts of basic compounds such as ammonia, monomethylamine, dimethylamine, trimethylamine, monophenylamine, diphenylamine, ethylenediamine, and ethanolamine. Among them, the salt of the acidic group is preferably an ammonium salt, and particularly preferably an ammonium salt of a carboxy group.
Examples of polar groups other than the "acidic group or a salt thereof" include an ester group, an epoxy group, an amide group, a carbonyl group, an acid anhydride group, a thiol group, an aldehyde group, a hydroxyl group, a cyano group, an amino group, a nitro group, and a halogen atom.
The above polymer particles have affinity for aqueous solvents due to the polar groups, and it is believed that these polar groups also contribute to the interaction with the lithium-fixed smectite.

In order to further enhance dispersibility in an aqueous medium, the above polymer has acidic groups, and it is preferable that at least a portion of the acidic groups are in the form of a salt. More specifically, the proportion of salts of acidic groups in the total molar amount of acidic groups and their salts contained in the above polymer is preferably 30 mol % or more, more preferably 50 mol % or more, and even more preferably 70 mol % or more.

The method for producing the above polymer is not limited to a specific method. The above polymer can be obtained by a normal polymerization reaction such as solution polymerization, interfacial polymerization, or emulsion polymerization using an α-olefin and an unsaturated monomer having a polar group as raw materials. The above polymer can also be obtained by graft polymerization of an unsaturated monomer having a polar group onto a polymer having a polyolefin structure.

The polar group is preferably introduced into the polymer by using a monomer having a polar group in addition to olefin in the synthesis of the polymer.For example, when incorporating a carboxyl group as a polar group, for example, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, butene tricarboxylic acid, etc., as a monomer, a polymerization reaction is carried out, and a carboxyl group can be introduced into the polymer.
When an acidic group is introduced as a polar group, the acidic group can be neutralized to form a salt by adding a neutralizing agent such as an alkali metal hydroxide after the polymerization reaction.

There is no particular restriction on the weight average molecular weight of the polymer. For example, it can be adjusted appropriately within the range of about 2,000 to 200,000.

The polymer particles may be derived from an aqueous dispersion in which the polymer particles are dispersed. That is, the aqueous dispersion of the present invention may contain polymer particles by blending an aqueous polyolefin dispersion (aqueous polyolefin dispersion). Such aqueous polyolefin dispersions are themselves known and are commercially available. An example of a commercially available product is ZAIXXEN A manufactured by Sumitomo Seika Chemicals.

The particle size of the polymer particles in the aqueous dispersion of the present invention is not limited to a specific range. The preferred particle size of the polymer particles in the aqueous dispersion of the present invention is 10 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less. The lower limit of the particle size of the polymer particles in the aqueous dispersion of the present invention is usually 0.1 μm. In the present invention, the particle size means the median size based on volume. This median size can be determined, for example, by a laser diffraction/scattering type particle size distribution measuring device (LA-950V2, manufactured by HORIBA).

The content of polymer particles in the solids content (components excluding the aqueous medium) of the aqueous dispersion of the present invention is preferably 20 to 97% by mass, more preferably 30 to 95% by mass, and even more preferably 35 to 95% by mass.

<Lithium-fixed smectite>
Smectite is a phyllosilicate mineral (layered clay mineral) having a layer structure. Specific examples of smectite include montmorillonite, beidellite, nontronite, saponite, hectorite, stevensite, and sauconite. The lithium-fixed smectite used in the present invention is preferably lithium-fixed montmorillonite.

Smectite that has lithium ions as the main cation is called lithium-type smectite. Methods for exchanging the cations of smectite with lithium ions include, for example, a method of adding lithium salts such as lithium hydroxide and lithium chloride to a dispersion of natural sodium-type smectite or calcium-type smectite to carry out cation exchange, and a method of passing a dispersion of sodium-type or calcium-type smectite through a cation exchange resin capable of ion-exchanging lithium. By adjusting the amount of lithium contained in the dispersion, the amount of lithium ions in the amount of leached cations in the obtained lithium-type smectite can be appropriately adjusted.
In the present invention and the specification, "lithium-type smectite" refers to smectite in which the amount of lithium ions (i.e., amount of leached lithium ions, unit: meq/100 g, the same applies below) in the amount of leached cations (i.e., total amount of leached cations, unit: meq/100 g, the same applies below) is 60% or more, preferably smectite in which the amount of leached lithium ions in the amount of leached cations is 70% or more, more preferably 80% or more. The amount of leached lithium ions in the amount of leached cations in lithium-type smectite may be 100%, but is usually 99% or less.
Lithium-type montmorillonite is also commercially available, for example, Kunipia-M (trade name, manufactured by Kunimine Kogyo Co., Ltd.).

Lithium-fixed smectite is a smectite in which some of the lithium ions in the lithium smectite are fixed to vacant sites in the octahedral sheets. Lithium-fixed smectite can be obtained, for example, by high-temperature treatment of lithium smectite, in which the interlayer lithium ions are fixed to vacant sites in the octahedral sheets or tetrahedrons. Fixing the lithium ions results in a closed structure between the crystal layers of the smectite, and the hydrophilicity is greatly reduced. This is thought to be because the lithium ions move to and are fixed in the vacant sites of the octahedral sheets of the clay crystals, electrically neutralizing the clay crystals and causing the layers to be tightly closed, making it difficult for water molecules to enter (hydration of the interlayer cations is difficult to occur).

There is no particular restriction on the temperature conditions of the high-temperature treatment for fixing lithium, so long as the lithium ions can be at least partially fixed. As described later, the smaller the cation exchange capacity (CEC), the more the water vapor barrier property and oxygen barrier property of the layer formed using the aqueous dispersion containing lithium-fixed smectite tend to improve. Therefore, from the viewpoint of efficiently fixing lithium ions and reducing the cation exchange capacity, it is preferable to heat at 150°C or higher. The temperature of the above heat treatment is more preferably 150 to 600°C, even more preferably 180 to 600°C, particularly preferably 200 to 500°C, and most preferably 250 to 500°C. By heating within the above temperature range, the CEC can be more efficiently reduced, and at the same time, the dehydration reaction of the hydroxyl groups in the smectite can be suppressed. The above heat treatment is preferably carried out in an open electric furnace. In this case, the relative humidity during heating is 5% or less, and the pressure is normal pressure. There is no particular restriction on the time of the above heat treatment, so long as the lithium can be fixed. From the viewpoint of production efficiency, the heat treatment time is preferably 0.5 to 48 hours, and more preferably 1 to 24 hours.

Whether or not a smectite is a lithium-fixed type can be determined by X-ray photoelectron spectroscopy (XPS). Specifically, the peak position of the binding energy derived from lithium ions in the XPS spectrum measured by XPS analysis is confirmed. For example, by converting lithium-type montmorillonite into lithium-fixed type montmorillonite by heat treatment or the like, the peak position of the binding energy derived from lithium ions in the XPS spectrum shifts from 57.0 ev to 55.4 ev. Therefore, whether or not a smectite is a fixed type can be determined by whether or not it has a binding energy peak at 55.4 ev.

The CEC of the lithium-fixed smectite is preferably 70 meq/100g or less, more preferably 65 meq/100g or less, from the viewpoint of improving the water vapor barrier property and oxygen barrier property (for example, oxygen barrier property under high humidity) of the layer formed using the aqueous dispersion of the present invention. The CEC of the lithium-fixed smectite is usually 1 meq/100g or more, may be 5 meq/100g or more, or may be 7 meq/100g or more. The CEC of the lithium-fixed smectite is preferably 1 to 70 meq/100g, more preferably 5 to 70 meq/100g, even more preferably 7 to 65 meq/100g, and even more preferably 7 to 63 meq/100g.
For example, lithium smectite usually has a CEC of about 80 to 150 meq/100 g, but the CEC can be reduced to 70 meq/100 g or less by immobilizing at least a portion of the lithium ions through high-temperature treatment.
In the present invention, the CEC of the lithium-loaded smectite means the CEC of the lithium-loaded smectite in an aqueous dispersion.

In this specification, the term "lithium-fixed smectite" refers to a lithium-fixed smectite in which the difference (unit: meq/100 g) between the amount of leached lithium ions in the lithium-fixed smectite used as a raw material in its preparation (as described above, the lithium-fixed smectite is obtained by subjecting lithium-fixed smectite to a heat treatment described below) and the amount of leached lithium ions in the lithium-fixed smectite is preferably 60% or more, more preferably 60 to 99%, and even more preferably 65 to 95% of the cation exchange capacity (unit: meq/100 g) of the lithium-fixed smectite used as the raw material.
The lithium-loaded smectite usually contains, in addition to lithium ions, sodium ions (Na ⁺ ), potassium ions (K ⁺ ), magnesium ions (Mg ²⁺ ), calcium ions (Ca ²⁺ ), etc. as leached cations. In the lithium-loaded montmorillonite used in the present invention, the total amount of leached ions of Na ⁺ , K ⁺ , Mg ²⁺ and Ca ²⁺ is preferably 1 to 30 meq/100 g, more preferably 1 to 20 meq/100 g, and even more preferably 1 to 10 meq/100 g.

The CEC of smectite can be determined in accordance with the Schollenberger method (Clay Handbook, Third Edition, edited by the Clay Science Society of Japan, May 2009, pp. 453-454). More specifically, the CEC can be measured by the method described in the Japan Bentonite Industry Association Standard Test Method JBAS-106-77.
The amount of leached cations in smectite can be calculated by leaching interlayer cations in smectite using 100 mL of 1 M ammonium acetate aqueous solution per 0.5 g of smectite for 4 hours or more, and measuring the concentrations of various cations in the resulting solution by ICP emission spectrometry, atomic absorption spectrometry, or the like.

In the aqueous dispersion of the present invention, the lithium-fixed smectite is preferably dispersed in a state in which its particle diameter is preferably 10 μm or less. From the viewpoint of preventing defects in the layer formed using the aqueous dispersion of the present invention and further enhancing functionality such as water vapor barrier property and oxygen barrier property, the particle diameter is more preferably 9.0 μm or less, even more preferably 8.0 μm or less, particularly preferably 7.0 μm or less, and most preferably 6.0 μm or less. The particle diameter is preferably 5.0 μm or less, more preferably 4.0 μm or less, and can also be 3.0 μm or less. In the slurry of the present invention, the lower limit of the particle diameter of the lithium-fixed montmorillonite is not particularly limited, and is usually 1.0 μm or more, and may be 1.2 μm or more, 1.5 μm or more, or 1.8 μm or more.
In the present invention, the "particle size" of the lithium-loaded montmorillonite in the slurry is a volume-based median size, as described above.

The ratio of the particle size of the lithium-fixed smectite to the particle size of the polymer particles contained in the aqueous dispersion of the present invention is preferably 0.05≦[particle size of lithium-fixed smectite]/[particle size of polymer particles]≦20, more preferably 0.075≦[particle size of lithium-fixed smectite]/[particle size of polymer particles]≦15, and even more preferably 0.1≦[particle size of lithium-fixed smectite]/[particle size of polymer particles]≦10. By achieving such a particle size relationship, the stacking arrangement of the lithium-fixed smectite can be made more uniform and smooth, and the layer formed using the aqueous dispersion of the present invention can exhibit high barrier performance.

The content of lithium-fixed smectite in the solid content of the aqueous dispersion of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and particularly preferably 10% by mass or more, from the viewpoint of improving the gas barrier properties of the layer formed using the aqueous dispersion of the present invention. The upper limit of the content is preferably 80% by mass, more preferably 60% by mass, even more preferably 40% by mass, and particularly preferably 30% by mass, from the viewpoint of the coating properties of the aqueous dispersion of the present invention and adhesion to the substrate. The content is preferably 5 to 50% by mass, and more preferably 10 to 20% by mass.

<Aqueous medium>
The aqueous medium constituting the aqueous dispersion of the present invention includes water. In addition, the aqueous medium constituting the aqueous dispersion of the present invention may or may not contain an organic medium (water-soluble organic solvent) compatible with water. The ratio of the organic medium to the total amount of the organic medium and water is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and also preferably 10% by mass or less. When the aqueous dispersion of the present invention is prepared by blending the polyolefin aqueous dispersion, the aqueous medium in the polyolefin aqueous dispersion constitutes the aqueous medium in the aqueous dispersion of the present invention. In addition, the aqueous medium in the aqueous dispersion of the present invention may contain at least one liquid medium of water and an organic solvent mixed separately.
The proportion of water in the aqueous medium contained in the aqueous dispersion of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and also preferably 90% by mass or more. It is also preferable that the entire aqueous medium is water.

Examples of the organic medium include lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, diacetone alcohol, and methoxypropanol; ketones such as acetone, methyl ethyl ketone, 2-butanone, methyl isobutyl ketone, and cyclohexanone; acetates such as methyl acetate, propyl acetate, and butyl acetate; N,N-dimethylformamide, N-methylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, acetonitrile, tetrahydrofuran, propylene carbonate, methyl cellosolve, ethyl glycol acetate, propylene glycol monomethyl ether acetate, and mixed solvents of one or more of these.

<Various additives>
The aqueous dispersion of the present invention may contain various additives other than the above-mentioned components. Examples of the various additives include a crosslinking agent, an organic filler such as a polymer other than the above-mentioned polymer, an inorganic filler other than lithium-fixed smectite, a stabilizer (antioxidant, heat stabilizer, ultraviolet absorber, etc.), a plasticizer, an antistatic agent, a lubricant, an antiblocking agent, a colorant, a crystal nucleating agent, an oxygen scavenger (a compound having an oxygen scavenging function), a tackifier, an emulsifier, a surfactant, etc.
Further, various additives include dispersants, coupling agents, leveling agents, defoamers, wetting agents, etc. These additives improve the wettability of the lithium-fixed smectite and improve the dispersibility of the lithium-fixed smectite in the aqueous dispersion of the present invention. They also improve the smoothness of the film formed by using the aqueous dispersion of the present invention and suppress bubbles in the aqueous dispersion of the present invention, thereby improving the uniformity of the film.
The above various additives may be used alone or in combination of two or more.

When the aqueous dispersion of the present invention is prepared using the above-mentioned polyolefin aqueous dispersion, the above-mentioned additives may be contained in the polyolefin aqueous dispersion. Also, the above-mentioned additives may be mixed separately.

The crosslinking agent forms a crosslinked network structure between the polymer chains. This suppresses swelling of the polymer particles in the aqueous dispersion of the present invention caused by water clusters, and may increase the water resistance of the layer formed using the aqueous dispersion of the present invention, resulting in improved water vapor barrier properties. There are no particular limitations on the crosslinking agent, so long as it is a compound that reacts with the polar group of the polymer. For example, when the polymer has a carboxy group, a carbodiimide compound or an oxazoline compound is preferably used as the crosslinking agent.

There is no particular limitation on the content of the crosslinking agent in the aqueous dispersion of the present invention. It is preferable that the number of moles of the polar groups in the polymer is close to the number of moles of the functional groups in the crosslinking agent that react with the polar groups. The polar groups generally have high reactivity or hydrophilicity with water, but if there are many polar groups that have reacted with the crosslinking agent, the reactivity or hydrophilicity of the polymer particles with water decreases, and it is believed that the water vapor barrier properties of the layer formed using the aqueous dispersion of the present invention are improved.

Inorganic fillers other than lithium-fixed smectite include inorganic substances such as metals, metal oxides, and minerals, and composites thereof. Specific examples of inorganic fillers include silica, alumina, titanium, zirconia, copper, iron, silver, mica, talc, aluminum flakes, glass flakes, and clay minerals other than lithium-fixed smectite. Among these, from the viewpoint of improving the water vapor barrier property and oxygen barrier property of the layer formed using the aqueous dispersion of the present invention, clay minerals other than lithium-fixed smectite are preferred, and swellable inorganic layered compounds are more preferred.

The above-mentioned swelling inorganic layered compounds include hydrous silicates (such as phyllosilicate minerals), kaolinite clay minerals (such as halloysite), smectite clay minerals other than lithium-fixed smectite (such as montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite), and vermiculite clay minerals (such as vermiculite). These minerals may be natural clay minerals or synthetic clay minerals. The above-mentioned swelling inorganic layered compounds may be used alone or in combination of two or more kinds.

Examples of tackifiers include xylene resins, terpene resins, and rosin resins. Tackifiers improve the adhesion of the layer formed using the aqueous dispersion of the present invention. The amount of tackifier added is preferably 0.01 to 5 parts by mass per 100 parts by mass of the aqueous dispersion of the present invention.

[pH of aqueous dispersion]
The pH of the aqueous dispersion of the present invention and the above-mentioned aqueous polyolefin dispersion is preferably 7 or more and less than 12, from the viewpoint of improving the dispersion stability of the lithium-fixed smectite.

[Method of preparing aqueous dispersion]
The preparation method of the aqueous dispersion of the present invention is not limited to a specific method. The aqueous dispersion of the present invention can be obtained by dispersing at least the above-mentioned polymer particles and the lithium-fixed smectite in an aqueous medium. The aqueous dispersion of the present invention may be obtained by dispersing or emulsifying the above-mentioned polymer using a surfactant, an emulsifier, or the like, and then mixing the lithium-fixed smectite and, if necessary, the above-mentioned additives. Furthermore, the aqueous dispersion of the present invention may be obtained by mixing a polyolefin aqueous dispersion containing the above-mentioned polymer particles, an aqueous dispersion or paste containing the lithium-fixed smectite, and, if necessary, the above-mentioned additives or aqueous medium.

[Uses of aqueous dispersions]
A laminate can be obtained by forming a layer on a substrate using the aqueous dispersion of the present invention. The laminate has a layer containing a composite of a polymer having a polyolefin structure and a polar group, and lithium-fixed smectite. The composite exhibits water vapor barrier properties and oxygen barrier properties by integrating the polymer with the lithium-fixed smectite.
The material of the substrate is not particularly limited. Examples of the substrate include wood, metal, polymer (resin), paper, silicon, or modified silicon. The substrate may be a substrate obtained by bonding different materials. The shape of the substrate is not particularly limited. The substrate may be any shape according to the purpose, such as a flat plate, a sheet, or a three-dimensional shape having a curvature on the entire surface or part. In addition, there is no limitation on the hardness and thickness of the substrate.

There is no limitation on the method of forming a layer on the substrate using the aqueous dispersion of the present invention. The formation method may be a direct coating method or a direct molding method. Examples of direct coating methods include spraying, spin coating, dip coating, roll coating, blade coating, doctor roll, doctor blade, curtain coating, slit coating, screen printing, and inkjet methods. Examples of direct molding methods include in-mold molding, insert molding, vacuum molding, extrusion lamination molding, and press molding. In the direct molding method, a layer of the uncured (undried) or semi-cured (semi-dried) aqueous dispersion of the present invention may be laminated on the substrate and then cured (dried), or a cured layer obtained by curing (drying) the aqueous dispersion of the present invention may be laminated on the substrate.

The laminate of the present invention may be obtained by applying a substrate precursor to a cured product of the aqueous dispersion of the present invention and curing the coating, or by adhering the substrate precursor and the aqueous dispersion of the present invention in an uncured or semi-cured state and then curing both of them. The substrate precursor is not particularly limited, and examples thereof include various curable resin compositions. The laminate may also be produced by using the aqueous dispersion of the present invention as an adhesive.

The layer formed using the aqueous dispersion of the present invention has excellent water vapor barrier properties and oxygen barrier properties, so the aqueous dispersion of the present invention can be suitably used as a gas barrier agent to form a gas barrier film.

The aqueous dispersion of the present invention can also be suitably used as a coating agent. The coating agent of the present invention is composed of the aqueous dispersion of the present invention. There is no particular limitation on the coating method of the coating agent of the present invention. Examples of the coating method include roll coating and gravure coating. The coating device is also not particularly limited. The coating film obtained by coating the aqueous dispersion of the present invention has excellent gas barrier properties such as water vapor barrier properties and oxygen barrier properties. Therefore, a coating film having excellent gas barrier properties can be formed using the aqueous dispersion of the present invention.

The aqueous dispersion of the present invention is also suitable as an adhesive. The form of the adhesive of the present invention is not particularly limited. The adhesive of the present invention may be in a liquid or paste form, or may be in a solid form. By bonding or fixing members, etc. using the adhesive of the present invention, gas barrier properties can be imparted to the bonded portion.

The aqueous dispersion of the present invention is also suitable as a heat sealant. The form of the heat sealant of the present invention is not particularly limited. The heat sealant of the present invention may be in a liquid or paste form, or may be in a solid form. Since the layer formed using the aqueous dispersion of the present invention has excellent gas barrier properties, gas barrier properties can be imparted to the heat-sealed portion by adhering or fixing a member or the like using the heat sealant of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In the examples, "parts" and "%" are by weight unless otherwise specified.

Example 1
Into a plastic container having a volume of 50 ml, 10 parts by mass of an aqueous dispersion of lithium-fixed montmorillonite (manufactured by Kunimine Kogyo Co., Ltd., product name RC-E, CEC 30 meq/100 g, content of lithium-fixed montmorillonite in the aqueous dispersion 10 mass %, particle size of lithium-fixed montmorillonite in the aqueous dispersion 2.0 μm, hereinafter referred to as "dispersion A") and 16 parts by mass of an aqueous dispersion of polyolefin in which carboxyl groups have been neutralized with ammonia (manufactured by Sumitomo Seika Chemicals Co., Ltd., product name ZAIXXEN A, content of polymer particles in the aqueous dispersion of polyolefin 25 mass %, particle size of polymer particles 7.0 μm, polymer constituting the polymer particles contains 70 mass % or more of a polyethylene structure and has carboxy groups, and 70 mol % or more of the carboxy groups are in the form of ammonium salts) were added and stirred for 8 hours with a magnetic stirrer to obtain an aqueous dispersion containing polymer particles and lithium-fixed montmorillonite. The obtained aqueous dispersion was applied to a 12 μm thick PET film (manufactured by Teijin DuPont Films Co., Ltd., product name Ester NS) using a bar coater so that the coating thickness after drying would be 2 μm, and the PET film coated with the aqueous dispersion was immediately heated and dried in a dryer at 120° C. for 10 minutes to obtain a laminated film. The oxygen permeability and water vapor permeability of the laminated film were measured by the methods described below. The results are shown in Table 1.

Example 2
A laminate film was obtained in the same manner as in Example 1, except that an aqueous dispersion of lithium-loaded montmorillonite (manufactured by Kunimine Kogyo Co., Ltd., CEC 9 meq/100 g, content of lithium-loaded montmorillonite in the aqueous dispersion 10 mass %, particle size of lithium-loaded montmorillonite in the aqueous dispersion 2.3 μm, hereinafter referred to as "Dispersion B") was used instead of Dispersion A, and the oxygen permeability and water vapor permeability of the laminate film were measured. The results are shown in Table 1.

Example 3
A laminate film was obtained in the same manner as in Example 1, except that an aqueous dispersion of lithium-loaded montmorillonite (manufactured by Kunimine Kogyo Co., Ltd., CEC 62 meq/100 g, content of lithium-loaded montmorillonite in the aqueous dispersion 10 mass %, particle size of lithium-loaded montmorillonite in the aqueous dispersion 1.8 μm, hereinafter referred to as "Dispersion C") was used instead of Dispersion A, and the oxygen permeability and water vapor permeability of the laminate film were measured. The results are shown in Table 1.

Example 4
A laminate film was obtained in the same manner as in Example 1, except that the amount of Dispersion A used was changed from 10 parts by mass to 30 parts by mass, and the amount of the polyolefin aqueous dispersion used was changed from 16 parts by mass to 8 parts by mass, and the oxygen permeability and water vapor permeability of the laminate film were measured. The results are shown in Table 1.

(Example 5)
A laminated film was obtained in the same manner as in Example 1, except that the amount of Dispersion A was changed from 10 parts by mass to 2.5 parts by mass, and the amount of the polyolefin aqueous dispersion was changed from 16 parts by mass to 19 parts by mass, and the oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 1.

(Comparative Example 1)
In a plastic container with a volume of 50 ml, 1 part by mass of a refined natural montmorillonite product with sodium interlayer ions (Kunipia F, CEC 108 meq/100 g, manufactured by Kunimine Industries Co., Ltd.) and 9 parts by mass of distilled water were added in this order, and then 16 parts by mass of the above-mentioned polyolefin aqueous dispersion was added and stirred with a magnetic stirrer for 8 hours to obtain an aqueous dispersion containing polymer particles and sodium-type montmorillonite. The obtained aqueous dispersion was applied to the above-mentioned PET film with a thickness of 12 μm using a bar coater so that the coating thickness after drying was 2 μm. Next, it was immediately heated and dried in a dryer at 120° C. for 10 minutes to obtain a laminated film, and the oxygen permeation rate and water vapor permeation rate of the laminated film were measured. The results are shown in Table 2.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Comparative Example 1, except that an ion-exchanged product of natural montmorillonite (Kunipia M, CEC 110 meq/100 g, manufactured by Kunimine Industries Co., Ltd.) in which the interlayer ions of Kunipia F were ion-exchanged with lithium was used instead of Kunipia F, and the oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 2.

(Comparative Example 3)
A laminated film was obtained in the same manner as in Example 1, except that distilled water was used instead of the dispersion A, and the oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 2.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 1, except that 8 parts by mass of an aqueous dispersion of acrylic polymer particles (Esdyne #7110 manufactured by Sekisui Chemical Co., Ltd., the content of polymer particles in the aqueous dispersion was 50% by mass, and the constituent polymer of the polymer particles does not have a polyolefin structure) was used instead of 16 parts by mass of the polyolefin aqueous dispersion, and distilled water was used in the amount shown in Table 2. The oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 2.

(Comparative Example 5)
A laminated film was obtained in the same manner as in Example 1, except that 11.4 parts by mass of an aqueous polyurethane emulsion (Eukoat UX-485 manufactured by Sanyo Chemical Industries, Ltd., the content of polyurethane particles in the aqueous polyurethane emulsion was 35% by mass, and the constituent polymer of the polyurethane particles does not have a polyolefin structure) was used instead of 16 parts by mass of the above-mentioned polyolefin aqueous dispersion, and distilled water was used in the amounts shown in Table 2. The oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 2.

(Comparative Example 6)
A laminated film was obtained in the same manner as in Example 1, except that 13.3 parts by mass of an aqueous polyester emulsion (Aronmelt 1055A30 manufactured by Toagosei Co., Ltd., the content of polyester particles in the aqueous polyester emulsion is 30% by mass, and the constituent polymer of the polyester particles does not have a polyolefin structure) was used instead of 16 parts by mass of the above-mentioned polyolefin aqueous dispersion, and distilled water was used in the amount shown in Table 2. The oxygen permeability and water vapor permeability of the laminated film were measured. The results are shown in Table 2.

(Reference example)
Table 2 shows the oxygen permeability and water vapor permeability of the PET film used above.

<Method for measuring oxygen transmission rate>
The oxygen transmission rate of each laminate film was measured at 23° C. and 90% RH in accordance with JIS-K7126 (constant pressure method) using an oxygen transmission rate measuring device OX-TRANI/50 manufactured by Mocon Corporation.

<Method for measuring water vapor transmission rate>
The water vapor transmission rate of each laminate film was measured at 40° C. and 90% RH using a moisture permeability cup in accordance with JIS Z 0208 "Test method for moisture transmission of moisture-proof packaging materials."

In Tables 1 and 2, the smectite content (%) in the solid content of the aqueous dispersion = (smectite content in aqueous dispersion) / (smectite content in aqueous dispersion + polymer particle content in aqueous dispersion) x 100.
The laminated films of Comparative Examples 1 to 3, which did not contain lithium-fixed smectite, had high oxygen and water vapor permeation rates, resulting in poor gas barrier properties. Sodium and lithium smectites have high swelling properties, and when they are blended in an amount of 1 part by mass or more, film formation is difficult. The laminated films of Comparative Examples 4 to 6, which blended polymer particles other than those specified in the present invention, also had high oxygen and water vapor permeation rates and poor gas barrier properties.
On the other hand, the oxygen permeation rate and water vapor permeation rate of the laminated films of Examples 1 to 6 were very small, and the gas barrier properties were excellent.

Claims (11)

The present invention relates to a method for producing a lithium-fixed smectite particles, the method comprising:
The proportion of the polyolefin structure in the polymer is 70 mass% or more,
The aqueous dispersion, wherein the polymer is a polymer having a structure obtained by neutralizing a polymer obtained by polymerizing an α-olefin and an unsaturated monomer having an acidic group, or a polymer having a structure obtained by graft polymerizing a polyolefin with an unsaturated monomer having an acidic group , The aqueous dispersion according to claim 1, wherein the cation exchange capacity of the lithium-fixed smectite is 1 to 70 meq/100 g. 3. The aqueous dispersion according to claim 1 , wherein the content of the lithium-fixed smectite in the solid content of the aqueous dispersion is 3 to 80 mass %. A laminate having a layer formed using the aqueous dispersion according to any one of claims 1 to 3 . The present invention has a layer containing a complex of a polymer having a polyolefin structure and an acidic group and a salt thereof , and a lithium-fixed smectite ,
The proportion of the polyolefin structure in the polymer is 70 mass% or more,
The laminate, wherein the polymer is a polymer having a structure obtained by neutralizing a polymer obtained by polymerizing an α-olefin and an unsaturated monomer having an acidic group, or a polymer having a structure obtained by graft polymerizing a polyolefin with an unsaturated monomer having an acidic group , A gas barrier agent comprising the aqueous dispersion according to any one of claims 1 to 3 . A gas barrier film having a layer formed using the aqueous dispersion according to any one of claims 1 to 3 . A coating agent comprising the aqueous dispersion according to any one of claims 1 to 3 . A coating film having a layer formed using the aqueous dispersion according to any one of claims 1 to 3 . An adhesive comprising the aqueous dispersion according to any one of claims 1 to 3 . A heat-sealing agent comprising the aqueous dispersion according to any one of claims 1 to 3 .