Aqueous dispersion

Abstract

Provided is an aqueous dispersion containing a tetrafluoroethylene-based polymer, which is capable of forming a molded article having excellent physical properties such as heat resistance, electrical characteristics (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent), and excellent surface appearance, and which has excellent dispersion stability and workability. An aqueous dispersion containing particles of a tetrafluoroethylene polymer, a water-soluble polymer having a polar functional group, and water, the water-soluble polymer being at least one type selected from the group consisting of vinyl alcohol polymers, acrylic polymers, polyvinylpyrrolidone, polypyrrole, polythiophene, polyethylene oxide, polyethyleneimine, and cellulose ethers, the concentration of at least one cation selected from the group consisting of alkali metal ions and alkaline earth metal ions in the aqueous dispersion is 0.1-1000 ppm.

Description

Technical Field

[0001] The present invention relates to an aqueous dispersion containing particles of a tetrafluoroethylene-based polymer. Background Art

[0002] In recent years, in order to cope with the high speed and high frequency of mobile communication equipment such as mobile phones, the insulating layer of the printed circuit board of the communication equipment requires a material with low dielectric constant and low dielectric loss tangent, and tetrafluoroethylene polymers have attracted much attention. As a material for forming an insulating layer comprising such a polymer, a dispersion comprising tetrafluoroethylene polymer particles and a liquid dispersion medium is known. Among them, the versatility of the equipment required for the aqueous dispersion when it is used, the selectivity of the substrate as the object of coating, etc. is high, and people are exploring the use of various additives to improve its liquid properties. Patent document 1 proposes an aqueous dispersion whose pH value at 25°C and solid content concentration of tetrafluoroethylene polymer are within specified ranges, and whose metal ion content is less than 100 ppm relative to the total aqueous dispersion. Patent document 2 proposes a dispersion comprising polyvinylidene fluoride particles, a specific nonionic surfactant, a specific polymer surfactant and a dispersion medium, and whose contents of sodium ions, potassium ions and ammonium ions are respectively below specified amounts. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-070741 Patent Document 2: Japanese Patent Application Publication No. 2016-222801 Summary of the invention Technical problem to be solved by the invention

[0004] Because the dispersibility of tetrafluoroethylene polymer particles in water is low, its aqueous dispersion is easy to foam, so the operability such as the fluidity of the aqueous dispersion is difficult to be said to be sufficient. If a viscosity modifier such as a water-soluble polymer is added, the viscosity and thixotropy (thixotropy) of the aqueous dispersion can be improved, but there is room for improvement in suppressing foaming. On the other hand, with patent documentation 1 or patent documentation 2 as a representative, the cation contained in the aqueous dispersion is considered to be a component that should be removed as much as possible as the main cause of the device pollution caused by the coloring or decomposition of tetrafluoroethylene polymers. The inventors have found that the aqueous dispersion containing tetrafluoroethylene polymers, specific water-soluble polymers and water, in which the concentration of alkali metal ions and alkaline earth metal ions in the liquid is controlled within a specific range, has excellent dispersion stability, suppressed foaming and is easy to operate. It is also found that the polymer layer and other formed objects formed by this dispersion have excellent properties such as heat resistance, electrical properties (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent) brought by tetrafluoroethylene polymers, and excellent surface appearance, thereby reaching the present invention. An object of the present invention is to provide an aqueous dispersion containing a tetrafluoroethylene polymer, which can form a molded product having excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent) and excellent surface appearance, and has excellent dispersion stability and handleability. Technical solutions adopted to solve technical problems

[0005] The present invention has the following technical contents. (1) An aqueous dispersion comprising particles of a tetrafluoroethylene polymer, a water-soluble polymer having a polar functional group, and water, wherein the water-soluble polymer is at least one selected from the group consisting of a vinyl alcohol polymer, an acrylic polymer, polyvinyl pyrrolidone, polypyrrole, polythiophene, polyethylene oxide, polyethyleneimine, and cellulose ether, wherein the concentration of at least one cation selected from the group consisting of an alkali metal ion and an alkaline earth metal ion in the aqueous dispersion is 0.1 to 1000 ppm. (2) The aqueous dispersion according to (1), wherein the tetrafluoroethylene polymer is thermally soluble and contains an oxygen-containing polar group. (3) The aqueous dispersion according to (1) or (2), wherein the average particle size of the tetrafluoroethylene polymer particles is 1 μm or more and less than 10 μm. (4) The aqueous dispersion according to any one of (1) to (3), wherein the content of the tetrafluoroethylene polymer particles is 25% by mass or more. (5) The aqueous dispersion according to any one of (1) to (4), wherein the content of the water-soluble polymer relative to the particles of the tetrafluoroethylene polymer is 5% by mass or less. (6) The aqueous dispersion according to any one of (1) to (5), wherein the water-soluble polymer is a vinyl alcohol-based polymer. (7) The aqueous dispersion according to any one of (1) to (5), wherein the water-soluble polymer is cellulose ether. (8) The aqueous dispersion according to (7), wherein the cellulose ether is carboxyalkyl cellulose, hydroxyalkyl cellulose or hydroxyalkyl alkyl cellulose. (9) The aqueous dispersion according to any one of (1) to (8), further comprising a silicone-based surfactant. (10) The aqueous dispersion according to any one of (1) to (9), further comprising an alcohol having 1 to 6 carbon atoms. (11) The aqueous dispersion according to any one of (1) to (10), which has a viscosity of 500 to 10,000 mPa·s. (12) The aqueous dispersion according to any one of (1) to (11), wherein the thixotropic ratio is 1.0 to 2.5. (13) The aqueous dispersion according to any one of (1) to (12), wherein the cation is at least one of a sodium ion and a potassium ion. (14) The aqueous dispersion according to any one of (1) to (13), wherein the pH value is greater than 8 and less than 11. (15) A method for producing a laminate, comprising placing the aqueous dispersion according to any one of (1) to (14) on a substrate surface and heating the dispersion to form a polymer layer containing the tetrafluoroethylene polymer, thereby obtaining a laminate having a substrate layer composed of the substrate and the polymer layer in this order. Effects of the Invention

[0006] According to the present invention, an aqueous dispersion having excellent dispersion stability and operability can be provided, and a molded product such as a coating film (polymer layer) having excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent) brought by a tetrafluoroethylene polymer and excellent surface appearance can be formed from the dispersion. DETAILED DESCRIPTION

[0007] The following terms have the following meanings. The average particle size (D50) is the volume-based cumulative 50% diameter of particles or fillers obtained by laser diffraction and scattering. That is, the particle size distribution is measured by laser diffraction and scattering, and the cumulative curve is obtained with the total volume of the particle group as 100%, and the particle size at the point where the cumulative volume reaches 50% on the cumulative curve. The D50 of particles or fillers is determined by dispersing the particles in water and analyzing the particles using a laser diffraction / scattering particle size distribution analyzer (LA-920 analyzer manufactured by Horiba, Ltd.). The “average particle size (D90)” is a volume-based cumulative 90% diameter of particles obtained in the same manner as D50. The “specific surface area of ​​particles or fillers” is a value calculated by measuring particles using a gas adsorption (constant volume method) BET multipoint method, and is obtained using a gas adsorption pore distribution measuring instrument (product name NOVA4200e, manufactured by Quantachrome Instruments). The "melting temperature" refers to the temperature corresponding to the maximum value of the melting peak of a polymer measured by differential scanning calorimetry (DSC). The “glass transition temperature (Tg)” is a value measured by analyzing a polymer using a dynamic viscoelasticity measurement (DMA) method. The "viscosity" was determined by measuring the dispersion using a B-type viscometer at 25°C and a rotation speed of 30 rpm. The measurement was repeated three times, and the average of the three measured values ​​was taken. The "thixotropic ratio" is a value calculated by dividing the viscosity η1 of the dispersion measured at a rotation speed of 30 rpm by the viscosity η2 measured at a rotation speed of 60 rpm. Each viscosity measurement was repeated 3 times, and the average of the 3 measured values ​​was taken. The "surface tension" of a solvent or solution is a value measured by the Wilhelmy method at 25°C using a surface tension meter. The "HLB (Hydrophilic-Lipophilic Balance) value" of a surfactant is a value determined by the Griffin method and defined by the following calculation formula. HLB value = 20 x [sum of chemical formula weights of hydrophilic moieties] / molecular weight The "degree of substitution" of cellulose ether is also called the degree of etherification, which indicates the number (average value) of hydroxyl groups substituted by alkoxy groups among the three hydroxyl groups on the glucose ring of cellulose. Theoretically, the degree of substitution can have a value between 0 and 3. Generally speaking, the higher the substituent, the more hydrophilic it is. The degree of substitution is calculated from the value measured by the degree of substitution analysis method of hydroxypropyl methylcellulose described in the 18th revised edition of the Japanese Pharmacopoeia. The "cation concentration" of the aqueous dispersion is the content of cations contained in a measurement sample obtained by ashing a dried product of the aqueous dispersion at 1000° C. for 4 minutes, and is determined by FLAAS (flame atomic absorption spectrometry), and is a value obtained from the value and the mass of the aqueous dispersion. The "unit" in a polymer refers to an atomic group based on a monomer formed by polymerization of the monomer. The unit may be a unit directly formed by a polymerization reaction, or a unit in which a part of the unit is converted into another structure by treating the polymer. Hereinafter, the unit based on monomer a is also referred to as "monomer a unit".

[0008] The aqueous dispersion of the present invention (hereinafter also referred to as "the present dispersion") comprises: particles (hereinafter also referred to as "F particles") of a tetrafluoroethylene polymer (hereinafter also referred to as "F polymer"), at least one water-soluble polymer having a polar functional group selected from vinyl alcohol polymers, acrylic polymers, polyvinyl pyrrolidone, polypyrrole, polythiophene, polyethylene oxide, polyethyleneimine and cellulose ether (hereinafter also referred to as "water-soluble polymer"), and water. In the present dispersion, the concentration of at least one cation selected from alkali metal ions and alkaline earth metal ions (hereinafter also referred to as "cation concentration") is 0.1 to 1000 ppm. The dispersion liquid has excellent dispersion stability and operability, and the formed products such as the coating film (polymer layer) formed from the dispersion liquid have excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent) brought by the tetrafluoroethylene polymer, and its surface appearance is excellent. In addition, in this specification, the so-called "excellent surface appearance" includes excellent surface smoothness such as "less surface roughness" or "no streaks, cracks or defects on the surface" and other excellent appearance observed by visual recognition or analysis equipment. Although the reason why the present dispersion liquid is excellent in dispersion stability, foaming is suppressed, and workability is excellent is not clear, the following reason is considered.

[0009] If a water-soluble polymer is added to an aqueous dispersion containing F particles, the viscosity of the aqueous dispersion can be increased, and the thixotropy and other liquid properties can be improved. In addition, when the aqueous dispersion forms a coating or other processed product, it also acts as a binder for the F particles. However, on the other hand, the aqueous dispersion becomes prone to foaming, the workability is deteriorated, and the transparency of the formed product tends to decrease, making it difficult to select a suitable water-soluble polymer. In this dispersion, the cation concentration is controlled within a specific range of 0.1 to 1000 ppm. That is, it is believed that by not excessively reducing the cation concentration in the dispersion, the aggregation (salting out) of the water-soluble polymer produced by the cations is slowly promoted, so that the thickening effect and the foaming inhibition effect are balanced. In addition, it is believed that by not excessively increasing the cation concentration, the transparency and dispersion stability of the dispersion caused by excessive aggregation of the water-soluble polymer are suppressed. Further, it is believed that in the molded product formed by the dispersion, the decrease in physical properties such as electrical properties caused by the cations remaining as salts is suppressed. This mechanism of action is particularly significant when the present dispersion contains an organosilicon surfactant or an alcohol having 1 to 6 carbon atoms. In particular, although such an alcohol improves the dispersibility of the F particles in the liquid, it also promotes the dissolution or swelling of the water-soluble polymer, thereby increasing the viscosity of the dispersion. Therefore, it is considered to be more important to control the cation concentration within the range of the present invention.

[0010] In this dispersion, the concentration of at least one cation selected from alkali metal ions and alkaline earth metal ions (hereinafter also referred to as "cation concentration") is 0.1 to 1000 ppm. This cation concentration is preferably 0.2 ppm or more, more preferably 0.5 ppm or more, and further preferably greater than 1 ppm. In addition, the cation concentration is preferably 100 ppm or less, more preferably 10 ppm or less, and further preferably 5 ppm or less. In this case, the above-mentioned mechanism of action is easily manifested. In addition, the binder function of the water-soluble polymer contained in this dispersion is further improved. When this dispersion is arranged on the surface of the substrate and heated to form a polymer layer containing F polymer, it is easy to suppress the powdering of F particles and highly prevent the occurrence of defects. It is also easy to maintain the hue of the resulting polymer layer well. Examples of the cation include alkali metal ions such as lithium ion, sodium ion, potassium ion, rubidium ion, and cesium ion, and alkaline earth metal ions such as beryllium ion, magnesium ion, calcium ion, strontium ion, and barium ion. Among them, the cation is preferably at least one of sodium ion and potassium ion.

[0011] The above-mentioned cations may be derived from the respective components and contained in the present dispersion. Examples of the cations include cations derived from polymer F. Examples of such cations include cations derived from metal hydroxides such as sodium hydroxide and potassium hydroxide used as a pH adjuster in a post-polymerization step to obtain polymer F. In addition, the cations mentioned above may be cations derived from water-soluble polymers. For example, cellulose ethers can be obtained by a production method in which refined pulp is brought into contact with an alkaline solution such as sodium hydroxide or potassium hydroxide and an etherifying agent is used to convert the hydroxyl groups contained in cellulose into ethers, and thus may contain cations derived from the alkaline solution. Vinyl alcohol polymers may contain cations derived from metal hydroxides such as sodium hydroxide or potassium hydroxide used as saponifying agents in the saponification step after vinyl ester polymerization. Furthermore, when natural water sources or groundwater are used as water directly, or when suspended matter or halogen components are removed by a filtration material such as a hollow fiber membrane or activated carbon and sterilized by heating as necessary, cations as mineral components may be contained.

[0012] In order to control and adjust the cation concentration of the present dispersion to fall within the above range, for example, the amount of cations derived from each component constituting the present dispersion may be controlled in advance. Specifically, desalination treatments such as a method of washing the F polymer with water in advance to control its cation concentration, a method of washing a water-soluble polymer with a washing liquid to control its cation concentration, and a method of controlling the cation concentration of the water used in advance may be mentioned. Furthermore, the prepared dispersion may be treated with an ion exchange resin to control and adjust the cation concentration within the above range.

[0013] The F polymer of the present invention is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The polymer F may be heat-fusible or non-heat-fusible. Here, the heat-fusible polymer refers to a polymer having a temperature at which the melt flow rate is 1 to 1000 g / 10 minutes under a load of 49 N. The melting temperature of the heat-melting polymer F is preferably 180° C. or higher, more preferably 200° C. or higher. The melting temperature of the polymer F is preferably 325° C. or lower, more preferably 320° C. or lower. In this case, a molded product such as a coating film (polymer layer) formed from the present dispersion tends to have excellent heat resistance.

[0014] The glass transition temperature of the F polymer is preferably 50° C. or higher, more preferably 75° C. or higher. The glass transition temperature of the F polymer is preferably 150° C. or lower, more preferably 125° C. or lower. The fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72 to 76% by mass.

[0015] The F polymer is preferably polytetrafluoroethylene (PTFE), a polymer containing TFE units and ethylene-based units (ETFE), a polymer containing TFE units and propylene-based units, a polymer containing TFE units and perfluoro(alkyl vinyl ether) (PAVE)-based units (PAVE units) (PFA), a polymer containing TFE units and hexafluoropropylene-based units (FEP), more preferably PFA and FEP, and further preferably PFA. These polymers may further contain units based on other comonomers. Examples of PTFE include low molecular weight PTFE and modified PTFE. The number average molecular weight of the low molecular weight PTFE is preferably 200,000 or less, more preferably 100,000 or less, and further preferably 50,000 or less. The number average molecular weight of the above PTFE is preferably 10,000 or more. In addition, the number average molecular weight is a value calculated based on the following formula (1). Mn=2.1×10 10 ×ΔHc -5.16 ···(1) In formula (1), Mn represents the number average molecular weight of low molecular weight PTFE, and ΔHc represents the heat of crystallization (cal / g) of low molecular weight PTFE measured by differential scanning calorimetry. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3 and CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and PPVE is more preferred.

[0016] F polymer preferably has oxygen-containing polar group, more preferably has hydroxyl-containing group or carbonyl-containing group, further preferably has carbonyl-containing group.In this case, in this dispersion liquid, the above-mentioned mechanism of action with its cation concentration controlled within the scope of the present invention is more likely to manifest, and dispersion stability and operability are excellent.In addition, the formed articles such as the coating (polymer layer) formed by this dispersion liquid are excellent in physical properties and surface appearance thereof such as heat resistance, electrical characteristics (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent). The hydroxyl-containing group is preferably an alcoholic hydroxyl-containing group, more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl-containing group is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH2), an anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) and a carbonate group (-OC(O)O-), and an anhydride residue is more preferred. In the case where the F polymer has an oxygen-containing polar group, the number of oxygen-containing polar groups in the F polymer is preferably 1×10 carbon atoms per 1×10 carbon atoms in the main chain. 6 The number of oxygen-containing polar groups in the polymer F is preferably 10 to 5000, and more preferably 100 to 3000. In addition, the number of oxygen-containing polar groups in the polymer F can be quantified based on the composition of the polymer or the method described in International Publication No. 2020 / 145133.

[0017] The oxygen-containing polar group may be contained in the monomer-based unit in the F polymer or in the terminal group of the F polymer main chain, and the former form is preferred. As the latter form, there can be mentioned F polymers having oxygen-containing polar groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., and F polymers obtained by subjecting F polymers to plasma treatment or ionizing radiation treatment.

[0018] The F polymer is preferably a polymer containing TFE units and PAVE units and containing units based on monomers having carbonyl groups, and more preferably a polymer containing TFE units, PAVE units and units based on monomers having carbonyl groups and containing 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol% of these units in order relative to all units. As a specific example of such a F polymer, a polymer described in International Publication No. 2018 / 16644 can be cited. The monomer having a carbonyl group is preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0019] In the present invention, the D50 of the F particles is preferably 1 μm or more and less than 10 μm. The F particles may be solid particles or non-hollow particles. The F particles may also be secondary particles formed by nanometer-level microparticles. The D50 of the F particles is preferably 1.0 μm or more, more preferably 1.5 μm or more. The D50 of the F particles is preferably 6 μm or less, more preferably 5 μm or less. Furthermore, D90 of the F particles is preferably 8 μm or less, more preferably 6 μm or less. When D90 of the F particles is below the above range, the above-mentioned mechanism of action is more likely to be manifested, and the present dispersion having a small number of coarse particles is more likely to be obtained. The specific surface area of ​​the F particles is preferably 1 to 25 m 2 / g, more preferably 6 to 15 m 2 / g.

[0020] The F particles are particles containing an F polymer, and preferably consist of an F polymer. The F particles are more preferably particles of a hot-melt F polymer having an oxygen-containing polar group with a melting temperature of 200 to 325° C. In this case, the above-mentioned action mechanism is more likely to be manifested, and aggregation of the F particles is also easily suppressed. The F particles may further contain a resin or inorganic compound other than the F polymer, and may form a core-shell structure with the F polymer as the core and the resin or inorganic compound other than the F polymer as the shell, or may form a core-shell structure with the F polymer as the shell and the resin or inorganic compound other than the F polymer as the core. Here, examples of the resin other than the F polymer include aromatic polyester, polyamideimide, polyimide, and maleimide, and examples of the inorganic compound include silicon dioxide and boron nitride. The F particles may be used alone or in combination of two or more.

[0021] The water-soluble polymer contained in the present dispersion is a water-soluble polymer having a polar functional group selected from at least one of vinyl alcohol polymers, acrylic polymers, polyvinyl pyrrolidone, polypyrrole, polythiophene, polyethylene oxide, polyethyleneimine and cellulose ether. In addition, in this specification, "water-soluble polymer" refers to a polymer having a solubility in water of 20 g / L or more. From the viewpoint of making it easier to manifest the above-mentioned mechanism of action, improving the rheological properties of the present dispersion, and improving the operability such as film-forming property, the polar functional group is preferably an ether bond, an ester bond, an amide bond, an imide bond, a thioether bond, a sulfide bond, a disulfide bond, a carbonyl-containing group, a hydroxyl-containing group, a thiol group, a sulfide group, a sulfonyl group, a sulfonyloxy group, an amino group, and an amide group, more preferably a hydroxyl-containing group, and further preferably a nonionic hydroxyl group. The polar functional group may be present in either the main chain or the side chain of the polymer. When polyvinyl pyrrolidone, polypyrrole, polythiophene, polyethylene oxide, or polyethyleneimine further has a hydroxyl group, the polymer preferably has a hydroxyl group at a main chain terminal.

[0022] Examples of the vinyl alcohol-based polymer include polyvinyl alcohol, polyvinyl acetate, partially acetylated or partially acetalized polyvinyl alcohol, and copolymers of vinyl alcohol, vinyl butyral, and vinyl acetate. Specific examples of vinyl alcohol polymers include the "S-LEC (registered trademark) B" series, the "S-LEC (registered trademark) K (KS)" series, the "S-LEC (registered trademark) SV" series (all manufactured by Sekisui Chemical Co., Ltd.) and the "MOWITAL (registered trademark)" series (manufactured by Kuraray Co., Ltd.). Examples of acrylic polymers include polyacrylic acid, sodium polyacrylate, acrylic acid / maleic acid copolymer sodium salt, acrylic acid / sulfonic acid monomer copolymer sodium salt and other polyacrylic acid salts, polyacrylates such as polymethyl acrylate and polyethyl acrylate, poly-α-haloacrylate, poly-α-cyanoacrylate, and polyacrylamide.

[0023] Examples of the cellulose ether include alkyl cellulose, carboxyalkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkyl alkyl cellulose. Examples of the carboxyalkyl cellulose include carboxymethyl cellulose and the like. Examples of the hydroxyalkyl cellulose include hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Examples of the hydroxyalkyl alkyl cellulose include hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl ethyl cellulose, and hydroxyethyl ethyl methyl cellulose, etc. These may be used alone or in combination of two or more. Among them, carboxyalkyl cellulose, hydroxyalkyl cellulose or hydroxyalkyl alkyl cellulose is preferred, hydroxyalkyl cellulose is more preferred, and hydroxyethyl cellulose is further preferred.

[0024] The degree of substitution of cellulose ether is preferably 1.4 or more, more preferably 1.9 or more, and further preferably 2.1 or more. In addition, the degree of substitution of cellulose ether is preferably 2.9 or less, and more preferably 2.7 or less. When the degree of substitution of cellulose ether satisfies the above range, the thickening effect and the interaction with F particles are balanced with the nonionic surfactant described later, especially the silicone surfactant, and the above mechanism of action is easy to manifest.

[0025] The weight average molecular weight of the cellulose ether is preferably 1000 to 10000. The weight average molecular weight can be measured, for example, by gel permeation chromatography (GPC) using a differential refractive index detector. Specific examples of cellulose ether include "SUNROSE (registered trademark)" series (produced by Nippon Paper Industries, Ltd.), "METOLOSE (registered trademark)" series (produced by Shin-Etsu Chemical Co., Ltd.), and "HEC CF grade" (produced by Sumitomo Seika Chemicals, Ltd.).

[0026] As the water-soluble polymer, among the above-mentioned substances, at least one selected from vinyl alcohol polymers and cellulose ethers is preferred. The weight average molecular weight of the water-soluble polymer is preferably 1000 or more, more preferably 10000 or more, further preferably 100000 or more, and particularly preferably 300000 or more. The weight average molecular weight of the water-soluble polymer is preferably 1000000 or less, more preferably 500000 or less. In this case, the dispersion liquid tends to have excellent physical properties such as dispersion stability. The present dispersion may further contain a viscosity modifier other than the above-mentioned water-soluble polymer from the viewpoint of adjusting the viscosity and thixotropic ratio.

[0027] As the water-soluble polymer, among the above substances, at least one selected from vinyl alcohol polymers and cellulose ethers is preferred. The weight average molecular weight of the water-soluble polymer is preferably 1,000 or more, more preferably 10,000 or more, further preferably 100,000 or more, and particularly preferably 300,000 or more. The weight average molecular weight of the water-soluble polymer is preferably 1,000,000 or less, more preferably 500,000 or less. In this case, the physical properties of the present dispersion such as dispersion stability are likely to be excellent. The present dispersion may further contain a viscosity modifier other than the above-mentioned water-soluble polymer from the viewpoint of adjusting the viscosity and thixotropic ratio.

[0028] The present dispersion may further contain a nonionic surfactant. Examples of the nonionic surfactant include glycol surfactants, acetylene surfactants, silicone surfactants, and fluorine surfactants. One or more nonionic surfactants may be used. Among them, silicone surfactants are preferred, and polyoxyalkylene-modified dimethylsiloxanes having a polyoxyalkylene structure as a hydrophilic portion and a polydimethylsiloxane structure as a hydrophobic portion are more preferred.

[0029] The polyoxyalkylene-modified dimethylsiloxane may have a polydimethylsiloxane unit (-(CH3)2SiO 2 / 2 -), may have a polydimethylsiloxane unit in the side chain, or may have a polydimethylsiloxane unit in both the main chain and the side chain. The polyoxyalkylene-modified polydimethylsiloxane is preferably a polyoxyalkylene-modified polydimethylsiloxane having a main chain containing a dimethylsiloxane unit and an oxyalkylene group in the side chain, or a polyoxyalkylene-modified polydimethylsiloxane having a main chain containing a dimethylsiloxane unit and an oxyalkylene group at the end of the main chain. The oxyalkylene groups contained in the polyoxyalkylene-modified dimethylsiloxane may be composed of only one type of oxyalkylene groups or may be composed of two or more types of oxyalkylene groups. In the latter case, different types of oxyalkylene groups may be connected randomly or in blocks.

[0030] The HLB value of the silicone surfactant is preferably greater than 10. Examples of such silicone surfactants include "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", and "BYK-3456" (manufactured by BYK Chemical Japan Co., Ltd.), and "KF-6011" and "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0031] When the present dispersion further contains a nonionic surfactant, preferably a silicone-based surfactant, the content thereof is preferably in the range of 1 to 15% by mass, more preferably in the range of 3 to 10% by mass, based on the F particles in the present dispersion.

[0032] The present dispersion may further contain an alcohol having 1 to 6 carbon atoms. Such an alcohol having 1 to 6 carbon atoms is a compound that is liquid at 25°C under atmospheric pressure and has a boiling point of preferably 160°C or less, more preferably 120°C or less.

[0033] Examples of alcohols having 1 to 6 carbon atoms include methanol (23 mN / m), ethanol (23 mN / m), 1-propanol (24 mN / m), 2-propanol (22 mN / m), 1-butanol (25 mN / m), 2-butanol (24 mN / m), isobutanol (23 mN / m), 1-methoxy-2-propanol (26 mN / m), 2-propoxy-ethanol (27 mN / m), 1-propoxy-2-propanol (25 mN / m), 2-ethoxyethanol (26 mN / m), ethylene glycol (48 mN / m), propylene glycol (25 mN / m), and glycerol (63 mN / m). The numerical values ​​in parentheses are surface tensions of the respective alcohols. These alcohols may be used alone or in combination of two or more. When two or more alcohols are used, they are preferably compatible with each other.

[0034] When the present dispersion contains an alcohol having 1 to 6 carbon atoms, the content thereof is preferably 0.1% by mass or more, more preferably 1% by mass or more relative to the present dispersion. The content of the alcohol having 1 to 6 carbon atoms is preferably 10% by mass or less, more preferably 5% by mass or less. From the viewpoint of the dispersion stability of the F particles, it is believed that even when a large amount of an organosilicon-based surfactant is contained, the alcohol having 1 to 6 carbon atoms acts as a defoaming agent such as a foam suppressing effect or a foam breaking effect.

[0035] In addition to the alcohol and water, other dispersion media may be used in the present dispersion liquid within the range that does not impair the effect of the present invention. Such other dispersion media are preferably mixed with the alcohol and water. As other dispersion media, amides such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, N,N-diethylformamide, hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolidinone; ketones such as acetone and methyl ethyl ketone may be cited.

[0036] The present dispersion may further contain an inorganic filler. In this case, a molded product such as a coating film (polymer layer) formed from the present dispersion tends to be excellent in electrical properties and low linear expansion properties. The shape of the inorganic filler can be any of spherical, needle-shaped (fibrous), and plate-shaped. Specifically, it can be spherical, flaky, layered, leaf-shaped, almond-shaped, columnar, cockscomb-shaped, equiaxed, leaf-shaped, mica-shaped, blocky, flat, wedge-shaped, rosette-shaped, mesh-shaped, and prism-shaped. Examples of the inorganic filler include silicon compounds such as quartz powder, silica, wollastonite, talc, silicon nitride, silicon carbide, and mica; nitrogen compounds such as boron nitride and aluminum nitride; metal oxides such as aluminum oxide, zinc oxide, titanium oxide, cerium oxide, beryllium oxide, magnesium oxide, nickel oxide, vanadium oxide, copper oxide, iron oxide, and silver oxide; carbon fibers; allotropes of carbon such as graphite, graphene, and carbon nanotubes; and metals such as silver and copper. The inorganic filler may be used alone or in combination of two or more. The D50 of the inorganic filler is preferably 0.1 to 50 μm. The surface of the inorganic filler may be surface treated with a silane coupling agent.

[0037] Specific examples of suitable inorganic fillers include silica fillers ("admafin (registered trademark)" series (produced by Yaduma Technology Co., Ltd.), "SFP (registered trademark)" series (produced by Denka Co., Ltd.), "E-SPHERES" series (produced by Pacific Cement Co., Ltd.)), zinc oxide fillers ("FINEX (registered trademark)" series (produced by Sakai Chemical Industry Co., Ltd.)), titanium oxide fillers ("TIPAQUE (registered trademark)" series (produced by Nissan)), and the like. series (produced by Ishihara Sangyo Co., Ltd.), "JMT (registered trademark)" series (produced by Teika Co., Ltd.), talc fillers ("SG" series (produced by Nippon Talc Co., Ltd.)), block talc fillers ("BST" series (produced by Nippon Talc Co., Ltd.)), boron nitride fillers ("UP40MF" series, "UP40" series (both produced by JFE Mining Co., Ltd.), "UHP" series (produced by Showa Denko K.K.), "Denka Boron Nitride" series of "GP", "HGP" grades (produced by Denka Co., Ltd.)), etc.). When the present dispersion contains an inorganic filler, the content of the inorganic filler in the present dispersion is preferably 1 to 25% by mass.

[0038] The present dispersion may further contain other resins different from the polymer F. Such other resins may be contained in the present dispersion in the form of non-hollow particles, or may be contained in the form of dissolved or dispersed in a liquid dispersion medium such as water constituting the present dispersion or an alcohol having 1 to 6 carbon atoms and other dispersion mediums as required (hereinafter, water, alcohol having 1 to 6 carbon atoms, other dispersion mediums, etc. are collectively referred to as "liquid dispersion medium") . Examples of other resins include polyester resins such as liquid crystalline aromatic polyesters, polyimide resins, polyamideimide resins, epoxy resins, maleimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene ether resins, and polyphenylene sulfide resins. The other resin is preferably an aromatic polymer, more preferably at least one aromatic imide polymer selected from aromatic polyimide, aromatic polyamic acid, aromatic polyamideimide and aromatic polyamideimide precursor. In the present dispersion, the aromatic polymer is preferably contained in the form of a varnish dissolved in a liquid dispersion medium.

[0039] Specific examples of aromatic imide polymers include the "UPIA-AT" series (manufactured by UBE Corporation), the "Neopulim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Co., Ltd.), the "SPIXAREA (registered trademark)" series (manufactured by Somaron Corporation), the "Q-PILON (registered trademark)" series (manufactured by PI Technology Laboratory), the "WINGO" series (manufactured by WINGO Technology Co., Ltd.), the "Tohmide (registered trademark)" series (manufactured by DICK TOKA CO., LTD.), the "KPI-MX" series (manufactured by Kawamura Sangyo Co., Ltd.), and "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.). When the present dispersion further contains other resins, the content of the other resins relative to the F particles is preferably 1 to 25% by mass.

[0040] The present dispersion may further contain additives such as a thixotropy-imparting agent, a defoaming agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a release agent, and a flame retardant.

[0041] The present dispersion can be obtained by mixing F particles, a water-soluble polymer and water, and, if necessary, the above-mentioned silicone-based surfactant, an alcohol having 1 to 6 carbon atoms, other dispersion media, an inorganic filler, other resins, additives and the like. The present dispersion can be obtained by mixing F particles, water-soluble polymer and water together, or by mixing them separately in sequence, or by making a masterbatch of these substances in advance and mixing them with the remaining ingredients. The mixing order is not particularly limited, and the mixing method can also be mixing all at once or in multiple times.

[0042] For example, from the viewpoint of improving dispersibility, it is preferred to disperse the F particles in a part of water in advance, then add a water-soluble polymer and mix, and then add the obtained mixture to the remaining water to obtain the present dispersion. When cellulose ether is used as the water-soluble polymer, it may be added in the form of a powder or an aqueous solution thereof, or may be added in a state of being dispersed or dissolved in a liquid defoamer or the like. When a silicone surfactant is also mixed, it can be added directly or in the form of an aqueous solution. In addition, when the alcohol having 1 to 6 carbon atoms, other dispersion media, inorganic fillers, other resins, additives, etc. are also mixed as needed, they can be mixed when the F particles are mixed with water, or when the mixture is added to water.

[0043] Examples of the mixing device used to obtain the present dispersion include stirring devices equipped with blades such as Henschel mixers, pressure kneaders, Banbury mixers, and planetary mixers; pulverizing devices equipped with media such as ball mills, pulverizers, basket mills, sand mills, sand mills, DYNO mills, DISPERMAT dispersers, SC mills, Spike mills, and stirred mills; and dispersing devices equipped with other mechanisms such as microfluidizers, nanometers, Ultimaizer dispersers, ultrasonic homogenizers, dissolvers, dispersers, high-speed impeller dispersers, thin film gyratory high-speed mixers, rotational revolution mixers, and V-type mixers.

[0044] The content of the F particles in the present dispersion is preferably 25% by mass or more, more preferably 35% by mass, and the content of the F particles is preferably 75% by mass or less, more preferably 60% by mass or less.

[0045] The content of the water-soluble polymer in the present dispersion is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and preferably 1% by mass or less, more preferably 0.1% by mass or less, relative to the total mass of the present dispersion. The content ratio of the water-soluble polymer to the content of the F particles in the present dispersion is preferably 0.001 or more, more preferably 0.003 or more, and preferably 0.05 or less, more preferably 0.03 or less, and further preferably 0.01 or less.

[0046] The water content in the present dispersion is preferably 25% by mass or more, more preferably 40% by mass. The water content is preferably less than 70% by mass, more preferably 65% ​​by mass or less. In addition, the water content in the present dispersion is preferably 60 to 180% by mass relative to the content of the F particles.

[0047] The viscosity of the present dispersion is preferably 500 mPa·s or more, more preferably 1000 mPa·s or more. The viscosity of the present dispersion is preferably 10000 mPa·s or less, more preferably 5000 mPa·s or less. In this case, the present dispersion has excellent coating properties and is easy to form a molded product such as a coating film (polymer layer) with any thickness. In addition, in the molded product obtained from the present dispersion within the viscosity range of this range, the physical properties of the F polymer are easily highly presented. The thixotropic ratio of the present dispersion is preferably 1.0 to 2.5. In this case, the present dispersion has excellent coating properties and homogeneity, and a denser molded product can be easily produced.

[0048] The pH value of the present dispersion is preferably 8 or more, more preferably greater than 8, and further preferably 8.1 or more. In addition, the pH value of the present dispersion is preferably 11 or less, more preferably 10 or less. In this case, the above-mentioned mechanism of action is easy to manifest. In particular, for the present dispersion in which the water-soluble polymer is a vinyl alcohol polymer or a cellulose ether and is within this pH value range, the modification of the water-soluble polymer in the liquid is easily promoted appropriately, and the liquid properties such as the foaming property of the liquid are easily improved. Furthermore, in the case of forming a fired molded product therefrom, since the low-temperature decomposition of the water-soluble polymer in the heating area is promoted, the water-soluble polymer is less likely to remain, and therefore the physical properties of the fired molded product are easily further improved. The pH of the present dispersion can be adjusted by a pH adjuster (amines such as ethanolamine, ammonia, citric acid, etc.) or a pH buffer (tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate, ammonium acetate, etc.).

[0049] The dielectric constant of the molded product formed from the present dispersion is preferably 2.4 or less, more preferably 2.0 or less. In addition, the dielectric constant is preferably greater than 1.0. The dielectric loss tangent of the molded product is preferably 0.0022 or less, more preferably 0.0020 or less. In addition, the dielectric loss tangent is preferably greater than 0.0010. The thermal conductivity of the molded product is preferably 1 W / m·K or more, more preferably 3 W / m·K or more.

[0050] If the present dispersion is subjected to a forming method such as extrusion into a sheet, a formed product such as a sheet containing the F polymer can be formed. The extruded sheet can be further cast by pressure forming, calendaring, etc. The sheet is preferably further heated to remove the liquid dispersion medium and calender the F polymer.

[0051] The thickness of the sheet formed from the present dispersion is preferably 1 to 1000 μm. The suitable ranges of the dielectric constant, dielectric loss tangent and thermal conductivity of the sheet are respectively the same as those of the above-mentioned molded product. In addition, the thermal conductivity of the sheet refers to the thermal conductivity in the in-plane direction of the sheet. The linear expansion coefficient of the sheet is preferably 100 ppm / °C or less, more preferably 80 ppm / °C or less. The lower limit of the linear expansion coefficient of the sheet is 30 ppm / °C. The linear expansion coefficient is a value obtained by measuring the linear expansion coefficient of a test piece in the range of 25°C to 260°C according to the measurement method specified in JIS C 6471:1995.

[0052] When such a sheet is laminated on a substrate, a laminate can be formed. Examples of a method for producing the laminate include a method of extruding the present dispersion on the substrate, a method of thermocompression bonding a sheet and the substrate, and the like. Examples of the substrate include: metal substrates such as metal foils of copper, nickel, aluminum, titanium, and alloys thereof; films of heat-resistant resins such as polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyallyl ether ketone, polyamideimide, liquid crystalline polyester, and tetrafluoroethylene polymers; prepreg substrates (precursors of fiber-reinforced resin substrates), ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride; and glass substrates.

[0053] Examples of the shape of the substrate include a flat surface, a curved surface, and a concave-convex shape. In addition, the substrate may be in any of a foil, a plate, a film, and a fiber. The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm. The substrate surface can be surface treated with a silane coupling agent or plasma treated. As such silane coupling agents, preferably silane coupling agents with functional groups such as 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-isocyanatepropyltriethoxysilane. The peel strength between the sheet and the substrate is preferably 10 to 100 N / cm.

[0054] Furthermore, when the present dispersion is placed on the surface of a substrate and heated to form a polymer layer containing F polymer (hereinafter also referred to as "F layer"), a laminate having a substrate layer composed of a substrate and the F layer in this order can be obtained. Preferably, the present dispersion is placed on the surface of the substrate, heated to remove the liquid dispersion medium, and further heated to calcine the F polymer to form the F layer. When the substrate is separated from the laminate, a sheet containing the F polymer can be obtained. Examples of the substrate include the same substrates as those which can be laminated on the above-mentioned sheet, and the preferred embodiments thereof are also the same.

[0055] Examples of a method for preparing the present dispersion include a coating method, a droplet spraying method, and a dipping method, and a roll coating method, a doctor blade coating method, a bar coating method, a die coating method, or a spray coating method is preferred. The heating for removing the liquid dispersion medium is preferably carried out at 100 to 200° C. for 0.1 to 30 minutes. During the heating at this time, the liquid dispersion medium does not need to be completely removed, as long as it is removed to the extent that the layer formed by the accumulation of F particles can maintain a self-supporting film. In addition, air can be blown during heating to promote the removal of the liquid dispersion medium by air drying.

[0056] The heating for calcining the F polymer is preferably performed at a temperature equal to or higher than the melting temperature of the F polymer, more preferably at 360 to 400° C. for 0.1 to 30 minutes. Examples of the heating device in each heating process include an oven and a ventilation drying furnace. The heat source in the device may be a contact heat source (hot air, a heating plate, etc.) or a non-contact heat source (infrared rays, etc.). In addition, each heating may be performed under normal pressure or under reduced pressure. In addition, the atmosphere during each heating may be any of an air atmosphere and an inert gas (helium, neon, argon, nitrogen, etc.) atmosphere.

[0057] The F layer is formed by the configuration and heating steps of the present dispersion. These steps may be performed once or repeated twice or more. For example, the present dispersion may be configured on the surface of the substrate and heated to form the F layer, and the present dispersion may be further configured on the surface of the F layer and heated to form the second F layer. The present dispersion may also be further configured on the surface of the substrate and heated to remove the liquid dispersion medium in the stage of removing the liquid dispersion medium. The present dispersion can be disposed on only one surface of the substrate or on both surfaces of the substrate. In the former case, a laminate having a substrate layer and an F layer on a single surface of the substrate layer can be obtained, and in the latter case, a laminate having a substrate layer and F layers on both surfaces of the substrate layer can be obtained. The thickness of the F layer varies depending on the application of the laminate, but is preferably in the range of 1 to 1000 μm.

[0058] Specific suitable examples of the laminate include a metal-clad laminate having a metal foil and an F layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and F layers on both surfaces of the polyimide film. The suitable ranges of the thickness, dielectric constant, dielectric loss tangent, thermal conductivity, linear expansion coefficient, and peel strength between the F layer and the substrate layer are the same as the suitable ranges of the thickness, dielectric constant, dielectric loss tangent, thermal conductivity, linear expansion coefficient, and peel strength between the sheet formed by the present dispersion as described above.

[0059] The present dispersion can be used as a material for imparting insulation, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and thermal conductivity. Specifically, the dispersion can be used for printed wiring boards, thermal interface materials, substrates for power modules, coils used in power devices such as motors, vehicle engines, heat exchangers, vials, syringes (syringes), ampoules, medical wires, secondary batteries such as lithium ion batteries, primary batteries such as lithium batteries, free radical batteries, solar cells, fuel cells, lithium ion capacitors, hybrid capacitors, capacitors, capacitors (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical conversion elements, electrode adhesives, electrode separators, and electrodes (positive and negative electrodes). In addition, the dispersion can also be used as an adhesive for bonding parts. Specifically, the dispersion can be used for bonding ceramic parts, bonding metal parts, bonding IC chips or electronic parts such as resistors and capacitors on substrates of semiconductor elements or module parts, bonding circuit substrates and heat sinks, and bonding LED chips on substrates.

[0060] Formed products such as sheets and laminates formed from the present dispersion can be used as antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, heat dissipation parts, and the like. Specifically, it can be used as a wire coating material (wire for aircraft, etc.), an enameled wire coating material used in motors of electric vehicles, etc., an electrical insulating tape, an insulating tape for oil drilling, an oil pipeline, a hydrogen tank, a printed circuit board material, a separation membrane (precision filtration membrane, ultrafiltration membrane, reverse osmosis membrane, ion exchange membrane, dialysis membrane, gas separation membrane, etc.), an electrode binder (for lithium secondary batteries, fuel cells, etc.), a copy roller, a cover for furniture, an automobile dashboard, home appliances, etc., a sliding member (load bearing, yaw bearing, sliding shaft, valve, bearing, bushing sleeves, seals, thrust washers, mounting rings, pistons, slide switches, gears, cams, belt conveyors, food conveyor belts, etc.), tension ropes, wear pads, wear strips, tube lights, test sockets, wafer guides, wear parts of centrifugal pumps, chemical and water supply pumps, tools (shovels, files, awls, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, molds, toilets, container covering materials, heat dissipation substrates for power devices, heat dissipation components of wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat sinks, metal heat sinks, blades of windmills or wind power generation equipment or aircraft, etc., computer or display housings, electronic device materials, automotive interior and exterior trim, processing machines or vacuum furnaces that perform heat treatment under low oxygen, sealing materials for plasma processing devices, etc., heat dissipation components in processing units such as sputtering or various dry etching devices, and electromagnetic wave shielding bodies.

[0061] Formed products such as sheets and laminates formed from the present dispersion can be used as electronic substrate materials such as flexible printed circuit boards and rigid printed circuit boards, protective films, or heat dissipation substrates, particularly heat dissipation substrates for automobiles.

[0062] Furthermore, the present dispersion can also be used as a coating agent for coating a feedthrough with F polymer, wherein the feedthrough penetrates the casing of a battery or capacitor made of a light metal such as aluminum, magnesium, titanium, silicon carbide, or alloys thereof. As such a feedthrough, there is mentioned a feedthrough in which a housing has an opening and a conductor is passed through the housing with a glass material that seals the opening. The glass material may be a glass ceramic material, and specifically, the material described in Japanese Patent Application Laid-Open No. 2018-502417 may be mentioned. As the conductor, materials suitable for electrode materials of batteries or capacitors can be cited, for example, in the case of the cathode of a battery, copper and copper alloys can be cited. The conductor can be composed of different materials on the inside and outside of the housing.

[0063] The F polymer of the present dispersion, especially the F polymer that is hot-melting and contains an oxygen-containing polar group, has excellent adhesion. If used to cover such a feedthrough, the glass material and the housing can be highly bonded. In addition, since the F polymer has excellent chemical resistance, the corrosion of the glass material can be highly suppressed. For example, a battery having a feedthrough coated with the F polymer of the present dispersion and using an electrolyte containing a lithium fluoride salt not only has excellent airtightness, but also has excellent durability because the corrosion of the glass material in the feedthrough accompanied by the generation of hydrofluoric acid is suppressed. Example

[0064] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. 1. Preparation of Ingredients [F polymer] F particles 1: each containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units, respectively. 6 Particles of tetrafluoroethylene polymer (melting temperature: 300°C) with 1000 carbonyl groups in the main chain (D50: 2.0 μm, specific surface area: 7 m 2 / g) F particles 2: particles composed of a polymer having no oxygen-containing polar group (melting temperature: 305°C) containing 97.5 mol% and 2.5 mol% of TFE units and PPVE units in that order (D50: 1.8 μm, specific surface area: 9 m 2 / g)

[0065] 2. Example of Preparation of Aqueous Dispersion [Example 1] After desalting each component and adjusting the salt content of each component, F particles 1, hydroxyethyl cellulose (substitution degree: 2.5), nonionic silicone surfactant (having a polysiloxane chain on the main chain and a polyoxyethylene on the side chain, HLB value = 13), water, ethanol and ethanolamine were added to the tank, and zirconium oxide balls were added. After that, the tank was rolled at 150 rpm for 1 hour to obtain a dispersion 1 (viscosity: 1000 mPa·s, pH value: 8.4) containing F particles 1 (35 parts by mass), hydroxyethyl cellulose (0.1 parts by mass), silicone surfactant (5 parts by mass), water (50 parts by mass), ethanol (10 parts by mass) and ethanolamine and having a cation concentration of 2 ppm. In addition, the cation concentration is the total concentration of sodium ions and potassium ions (the same applies below).

[0066] [Example 2] In the same manner as in Example 1, except that ethanol was not added, a dispersion 2 (viscosity: 2000 mPa·s) containing F particles 1 (35 parts by mass), hydroxyethyl cellulose (0.1 parts by mass), a silicone surfactant (5 parts by mass) and water (60 parts by mass) and having a cation concentration of 1 ppm was obtained. [Example 3] In the same manner as in Example 1, except that ethanol was not added and the salt content of each component was not adjusted, a dispersion 3 (viscosity: 2000 mPa·s) containing F particles 1 (35 parts by mass), hydroxyethyl cellulose (0.1 parts by mass), a silicone surfactant (5 parts by mass) and water (60 parts by mass) and having a cation concentration of 1100 ppm was obtained.

[0067] [Example 4] After desalting each component and adjusting the salt content of each component, F particles 2, polyvinyl alcohol and water were added to the tank, and zirconium oxide balls were added. Thereafter, the tank was rolled at 150 rpm for 1 hour to obtain a dispersion 4 containing F particles 2 (35 parts by mass), polyvinyl alcohol (0.1 parts by mass) and water (64.9 parts by mass) and having a cation concentration of 3 ppm. [Example 5] In the same manner as in Example 4, a dispersion 5 containing F particles 2 (35 parts by mass), polyvinyl alcohol (0.1 parts by mass), a silicone surfactant (5 parts by mass) and water (59.9 parts by mass) and having a cation concentration of 0.04 ppm was obtained. [Example 6] Except that the salt content of each component is not adjusted, a dispersion 6 containing F particles 2 (35 parts by mass), polyvinyl alcohol (0.1 parts by mass), a silicone surfactant (5 parts by mass) and water (59.9 parts by mass) and having a cation concentration of 2000 ppm is obtained in the same manner as Example 4.

[0068] [Example 7] A dispersion 7 (viscosity: 950 mPa·s, pH: 7.7) having a cation concentration of 2 ppm was obtained in the same manner as in Example 1 except that the amount of ethanolamine used was adjusted. [Example 8] In the same manner as in Example 1 except that ethanolamine was not used, a dispersion 8 (viscosity: 1100 mPa·s, pH: 11.1) having a cation concentration of 2 ppm was obtained.

[0069] 3. Evaluation 3-1. Dispersibility of dispersion containing inorganic filler Using each of the dispersions 4 to 6, the properties when a dispersion further containing an inorganic filler was prepared and the dispersibility of the obtained dispersion were evaluated. Specifically, 100 parts by mass of dispersion 4 and 50 parts by mass of silica filler (D50: 0.6 μm) were added to a tank, and zirconium oxide balls were added. The tank was then rolled at 150 rpm for 1 hour to prepare dispersion 4' containing silica filler. After standing, the dispersion was visually evaluated to show that no sediment was generated and the dispersion was good. In the dispersion 5' prepared in the same manner as above using the dispersion 5, a part of the sediment was generated and the dispersibility was deteriorated. Furthermore, the dispersion 6' prepared in the same manner as above using the dispersion 6 had a significantly increased viscosity and a portion thereof was gelled.

[0070] 3-2. Evaluation of fluidity of dispersion and production of laminate (Part 1) Dispersions 1 to 3 were used to manufacture a laminate, and the operability and the polymer layer formed at this time were evaluated. Specifically, using a roll-to-roll process, each dispersion was applied to one surface of a substrate (polyimide film (PI Advanced Materials "FG-100": thickness 25 μm) by a small-diameter gravure reverse method to form a coating layer, and it was passed through a ventilated drying furnace (furnace temperature: 150°C) for 3 minutes to remove water to form a dry film. In addition, each dispersion was applied to the other surface of the substrate in the same manner to form a coating layer, and dried to form a dry film. Next, the substrate with dry films formed on both sides was passed through a far-infrared furnace (furnace temperature of 300°C near the inlet and outlet of the furnace, and furnace temperature of 360°C near the center) for 5 minutes to melt and sinter the F particles to obtain a laminate having a polymer layer (thickness 25 μm) on both sides of the substrate. Dispersion 1 provided a coating layer having no bubbles on the surface, a transparent layer, and a smooth polymer layer without surface defects or streaks. In the case of dispersion 2, a polymer layer was obtained in which slight bubbles were observed on the surface of the coating layer and the coloring resulted in a slightly deteriorated transparency. The coating layer obtained by dispersion 3 had bubbles on the surface, and the polymer layer was colored and had surface defects.

[0071] 3-3. Evaluation of fluidity of dispersion and production of laminate (Part 2) A laminate was produced in the same manner as in 3-1 above using each of the dispersions 1, 7, and 8, and the handleability and the polymer layer formed were evaluated. Dispersion 1 provided a coating layer having no bubbles on the surface, a transparent layer, and a smooth polymer layer without surface defects or streaks. Dispersions 7 and 8 gave polymer layers with slight bubbles on the surface of the coating layer and slightly reduced transparency. Possibility of industrial application

[0072] The dispersion of the present invention is excellent in dispersion stability and handling properties. In addition, it can form a molded product such as a coating film (polymer layer) that highly exhibits the physical properties of the F polymer and has an excellent surface appearance.

[0073] In addition, the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2022-159851 filed on October 3, 2022 are cited here as a disclosure of the specification of the present invention.

Claims

1. An aqueous dispersion comprising particles of a tetrafluoroethylene polymer, a water-soluble polymer having a polar functional group, and water, wherein the water-soluble polymer is at least one selected from the group consisting of vinyl alcohol polymers, acrylic polymers, polyvinyl pyrrolidone, polypyrrole, polythiophene, polyethylene oxide, polyethyleneimine, and cellulose ether, wherein the concentration of at least one cation selected from the group consisting of alkali metal ions and alkaline earth metal ions in the aqueous dispersion is 0.1 to 1000 ppm.

2. The aqueous dispersion according to claim 1, wherein The tetrafluoroethylene polymer is heat soluble and contains oxygen-containing polar groups.

3. The aqueous dispersion according to claim 1, wherein The average particle size of the tetrafluoroethylene polymer particles is greater than or equal to 1 μm and less than 10 μm.

4. The aqueous dispersion according to claim 1, wherein The content of the tetrafluoroethylene polymer particles is 25% by mass or more.

5. The aqueous dispersion according to claim 1, wherein The content of the water-soluble polymer relative to the tetrafluoroethylene polymer particles is 5% by mass or less.

6. The aqueous dispersion according to claim 1, wherein The water-soluble polymer is a vinyl alcohol polymer.

7. The aqueous dispersion according to claim 1, wherein The water-soluble polymer is cellulose ether.

8. The aqueous dispersion according to claim 7, wherein The cellulose ether is carboxyalkyl cellulose, hydroxyalkyl cellulose or hydroxyalkyl alkyl cellulose. 9 . The aqueous dispersion according to claim 1 , further comprising a silicone surfactant. 10 . The aqueous dispersion according to claim 1 , further comprising an alcohol having 1 to 6 carbon atoms.

11. The aqueous dispersion according to claim 1, which has a viscosity of 500 to 10000 mPa·s.

12. The aqueous dispersion according to claim 1, which has a thixotropic ratio of 1.0 to 2.

5.

13. The aqueous dispersion according to claim 1, wherein The cation is at least one of a sodium ion and a potassium ion.

14. The aqueous dispersion according to claim 1, wherein The pH value is greater than 8 and below 11.

15. A method for producing a laminate, comprising placing the aqueous dispersion according to any one of claims 1 to 14 on a substrate surface and heating the dispersion to form a polymer layer containing the tetrafluoroethylene polymer, thereby obtaining a laminate having a substrate layer composed of the substrate and the polymer layer in this order.