Aqueous dispersion and method for producing laminate

Abstract

An aqueous dispersion contains: particles containing a hot-melt tetrafluoroethylene polymer, a poly (meth) acrylic acid having a weight average molecular weight of 200,000 or more; a pH buffer having a pH optimum range of 4-10, and water; wherein the aqueous dispersion has a pH of 4-10.

Description

Aqueous dispersion and method for producing laminate

[0001] The present disclosure relates to an aqueous dispersion and a method for producing a laminate.

[0002] Fluorine resins have excellent physical properties such as electrical properties, water and oil repellency, chemical resistance, and heat resistance, and are used in a variety of fields. In particular, tetrafluoroethylene-based polymers have excellent physical properties such as mold releasability, electrical insulation, water and oil repellency, chemical resistance, weather resistance, and heat resistance, and are processed into various molded products for use. For example, Patent Document 1 describes a fluororesin aqueous dispersion containing fluororesin particles having a volume average particle size within a specific range. It is stated that this fluororesin aqueous dispersion preferably contains a water-soluble thickener in terms of improving dispersibility and redispersibility and suppressing sedimentation.

[0003] Japanese Patent Application Laid-Open No. 2019-052211

[0004] In Patent Document 1, the addition of a water-soluble thickener improves the dispersibility of the fluororesin particles and suppresses sedimentation, but it has been found that even with this configuration, the fluororesin particles still sediment over time, causing a change in viscosity. When the viscosity of the aqueous dispersion changes, it becomes difficult to handle.

[0005] In view of the above circumstances, one embodiment of the present disclosure relates to providing an aqueous dispersion in which change in viscosity over time is suppressed, and a method for producing a laminate using the aqueous dispersion.

[0006] The present disclosure includes the following aspects. <1> An aqueous dispersion having a pH of 4 to 10, comprising particles containing a heat-fusible tetrafluoroethylene-based polymer, poly(meth)acrylic acid having a weight-average molecular weight of 200,000 or more, a pH buffer having an optimum pH range of 4 to 10, and water. <2> The aqueous dispersion according to <1>, having a viscosity of 500 mPa·s or more at 25°C. <3> The aqueous dispersion according to <1> or <2>, wherein the heat-fusible tetrafluoroethylene-based polymer contains units based on tetrafluoroethylene and at least one of units based on perfluoro(alkyl vinyl ether) and units based on hexafluoropropylene. <4> The aqueous dispersion according to any one of <1> to <3>, wherein the heat-fusible tetrafluoroethylene-based polymer has a carbonyl group-containing group. <5> The heat-fusible tetrafluoroethylene-based polymer has a main chain carbon number of 1×10 ６ The aqueous dispersion according to any one of <1> to <4>, wherein the particles containing a heat-fusible tetrafluoroethylene-based polymer have 10 to 5,000 carbonyl group-containing groups per particle. <6> The aqueous dispersion according to any one of <1> to <5>, wherein the particles containing a heat-fusible tetrafluoroethylene-based polymer have an average particle size of 10 μm or less. <7> The particles containing a heat-fusible tetrafluoroethylene-based polymer have a specific surface area of ​​6 m ２ / g or more. <8> The aqueous dispersion according to any one of <1> to <7>, wherein the content of particles containing the heat-fusible tetrafluoroethylene-based polymer is 60 mass% or less. <9> The aqueous dispersion according to any one of <1> to <8>, wherein the weight-average molecular weight of the poly(meth)acrylic acid is 500,000 to 1,500,000. <10> The aqueous dispersion according to any one of <1> to <7>, wherein the poly(meth)acrylic acid has at least one unit selected from the group consisting of units based on a compound represented by the following general formula (I) and units based on a compound represented by the following general formula (II): In general formula (I), R １ represents a hydrogen atom or a methyl group, R ２represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, a trialkylsilyl group having 3 to 9 carbon atoms, a group represented by the following general formula (IA) or a group represented by the following general formula (IB): In general formula (IA), R ３ represents an alkylene group having 1 to 4 carbon atoms, and R ４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 2 to 20. In general formula (IB), R ５ ~R ７ each independently represents an alkyl group having 1 to 3 carbon atoms, R ８ represents an alkylene group having 1 to 3 carbon atoms. In general formula (II), R １１ represents a hydrogen atom or a methyl group, R １２ and R １３ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. <11> The aqueous dispersion according to any one of <1> to <10>, wherein the pH buffer contains at least one selected from the group consisting of carbonic acid, phosphoric acid, boric acid, formic acid, oxalic acid, acetic acid, citric acid, isocitric acid, lactic acid, and ammonium salts thereof, as well as sulfonic acids and amino acids. <12> The aqueous dispersion according to any one of <1> to <11>, wherein the viscosity at 25°C is 10,000 mPa s or less. <13> The aqueous dispersion according to any one of <1> to <12>, further containing a surfactant having no fluorine atoms. <14> A method for producing a laminate, comprising applying the aqueous dispersion according to any one of <1> to <13> to a substrate, heating to remove the water, and further heating to melt and sinter the particles containing the heat-fusible tetrafluoroethylene-based polymer.

[0007] According to one embodiment of the present disclosure, there are provided an aqueous dispersion in which change in viscosity over time is suppressed, and a method for producing a laminate using the aqueous dispersion.

[0008] Hereinafter, modes for carrying out embodiments of the present disclosure will be described in detail. However, the embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and they do not limit the embodiments of the present disclosure.

[0009] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In this disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In this disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the aqueous dispersion, the content or amount of each component means the total content or amount of the multiple substances present in the aqueous dispersion, unless otherwise specified. In this disclosure, multiple types of particles corresponding to each component may be contained. When multiple types of particles corresponding to each component are present in the aqueous dispersion, the particle size of each component means the value for a mixture of the multiple types of particles present in the aqueous dispersion, unless otherwise specified. In this disclosure, the terms "layer" and "film" include cases where the layer or film is formed over the entire area when the area where the layer or film is present is observed, as well as cases where the layer or film is formed only in a portion of the area. In this disclosure, the term "lamination" refers to stacking layers, and two or more layers may be bonded together, or two or more layers may be detachable. In this disclosure, a "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 formed directly by a polymerization reaction, or may be a unit in which a portion of the unit is converted into a different structure by treating the polymer. Hereinafter, a unit based on monomer a will also be simply referred to as a "monomer a unit."

[0010] In this disclosure, the "melting temperature" of a tetrafluoroethylene-based polymer is the temperature corresponding to the maximum value of the melting peak of the polymer measured by differential scanning calorimetry (DSC). In this disclosure, the "melt flow rate" of a tetrafluoroethylene-based polymer means the melt mass-flow rate of the polymer as defined in JIS K 7210-1:2014 (ISO1133-1:2011). In this disclosure, the "glass transition temperature (Tg)" of a tetrafluoroethylene-based polymer is a value measured by analyzing the polymer by dynamic mechanical analysis (DMA).

[0011] In the present disclosure, the "weight average molecular weight" of poly(meth)acrylic acid is determined as a polystyrene-equivalent weight average molecular weight in gel permeation chromatography (GPC) analysis. In the present disclosure, the average particle size of particles refers to the volume average particle size (D50), which is the volume-based cumulative 50% diameter of particles determined by laser diffraction / scattering. That is, the particle size distribution is measured by laser diffraction / scattering, a cumulative curve is calculated with the total volume of the particle population as 100%, and the particle size is the point on the cumulative curve where the cumulative volume is 50%. The D50 of particles is determined by dispersing the particles in water and analyzing them by laser diffraction / scattering using a laser diffraction / scattering particle size distribution analyzer (for example, the laser diffraction / scattering particle size distribution analyzer "LS-13 320" manufactured by Beckman Coulter).

[0012] In the present disclosure, the "specific surface area" is a value calculated by measuring particles using a gas adsorption (constant volume) BET multipoint method, and is determined using a BET specific surface area measuring device (for example, NOVA4200e (manufactured by Quantachrome Instruments)).

[0013] In the present disclosure, the "viscosity" of an aqueous dispersion is determined by measuring the aqueous dispersion using a Brookfield viscometer at 25°C and a rotation speed of 30 rpm. The measurement is repeated three times, and the average value of the three measured values ​​is used. In the present disclosure, the "thixotropy ratio" of an aqueous dispersion is the viscosity η of the aqueous dispersion measured at a rotation speed of 30 rpm. １ The viscosity η measured at a rotation speed of 60 rpm ２Each viscosity measurement is repeated three times, and the average of the three measurements is used.

[0014] <Aqueous Dispersion> The aqueous dispersion of the present disclosure contains particles containing a heat-fusible tetrafluoroethylene-based polymer, poly(meth)acrylic acid having a weight-average molecular weight of 200,000 or more, a pH buffer having an optimum pH range of 4 to 10, and water. Hereinafter, the heat-fusible tetrafluoroethylene-based polymer will also be referred to as "F polymer," and particles containing the heat-fusible tetrafluoroethylene-based polymer will also be referred to as "F particles." Furthermore, poly(meth)acrylic acid having a weight-average molecular weight of 200,000 or more will also be referred to as "specific poly(meth)acrylic acid." Furthermore, a pH buffer having an optimum pH range of 4 to 10 will also be referred to as "pH buffer." In the aqueous dispersion with the above-described configuration, sedimentation of the F particles is suppressed, and viscosity changes over time are suppressed. The reason for this is not clear, but is presumed to be as follows.

[0015] Aqueous dispersions containing F particles tend to decrease in pH over time. While poly(meth)acrylic acid is a substance that exhibits a high degree of thickening function due to its functional groups, it is also prone to denaturation due to changes in the pH of aqueous dispersions over time. Furthermore, when poly(meth)acrylic acid contains units based on (meth)acrylate as a copolymer component, hydrolysis of the ester moieties is likely to proceed. This is thought to result in a decrease in the thickening function of poly(meth)acrylic acid over time. Therefore, it is speculated that the thickening function of poly(meth)acrylic acid can be maintained over time by setting the weight-average molecular weight of poly(meth)acrylic acid to 200,000 or more, increasing the number of constituent units to increase the absolute number of functional groups that exhibit thickening function, and using a pH buffer with an optimal pH range of 4 to 10 in combination to maintain the pH of the aqueous dispersion within the range of 4 to 10. The present inventors have found that this effect is more pronounced when the average particle size of the F particles is small or the specific surface area of ​​the F particles is large, resulting in a strong interaction between the F particles and water, or when the content of the F particles in the aqueous dispersion is within a certain range, the liquid viscosity of the aqueous dispersion is low, and the F particles themselves have a high degree of freedom. Each component contained in the aqueous dispersion will be described below.

[0016] (F particle) The F polymer contained in F particle is a polymer that comprises units (hereinafter also referred to as "TFE unit") based on tetrafluoroethylene (hereinafter also referred to as "TFE unit").From the viewpoint of favorably expressing the properties of TFE unit, the content of TFE unit in F polymer is preferably 50 mol% or more, more preferably 90 mol% or more, based on the total units in F polymer.The content may be 99 mol% or less, or may be 98 mol% or less.

[0017] The F polymer is heat-meltable. A heat-meltable polymer means a polymer that has a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. From the viewpoint of heat resistance, the melting temperature of the F polymer is preferably 200°C or higher, more preferably 260°C or higher. From the viewpoint of ease of processing, the melting temperature of the F polymer is preferably 325°C or lower, more preferably 320°C or lower.

[0018] From the viewpoint of heat resistance, the glass transition point of the F polymer is preferably 50°C or higher, more preferably 75°C or higher. From the viewpoint of ease of processing, the glass transition point of the F polymer is preferably 150°C or lower, more preferably 125°C or lower. From the viewpoint of favorable expression of properties due to fluorine atoms, such as electrical properties and heat resistance, the fluorine content of the F polymer is preferably 70% by mass or higher, more preferably 72 to 76% by mass. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of a wettability index reagent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) on a flat plate made of the F polymer.

[0019] F polymer is preferably polytetrafluoroethylene (PTFE), the polymer comprising TFE unit and unit based on ethylene, the polymer comprising TFE unit and unit based on propylene, the polymer comprising TFE unit and unit based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE unit) (PFA), and the polymer comprising TFE unit and unit based on hexafluoropropylene (FEP), more preferably the polymer comprising TFE unit and at least one of PAVE unit and unit based on hexafluoropropylene, more preferably the polymer comprising TFE unit and at least one of PAVE unit and unit based on hexafluoropropylene, from the viewpoint of properties such as adhesiveness, processability, etc., PFA and FEP are more preferred, and PFA is more preferred.These polymers may further comprise unit based on other comonomer. PAVE is CF ２ = CFOCF ３ , C.F. ２ = CFOCF ２ CF ３ and CF ２ = CFOCF ２ CF ２ CF ３ (hereinafter also referred to as "PPVE") is preferred, and PPVE is more preferred.

[0020] In particular, from the viewpoint of obtaining an aqueous dispersion with high uniformity and improving the adhesiveness of molded articles obtained therefrom, the F polymer preferably has an oxygen-containing polar group, more preferably has a hydroxyl group-containing group or a carbonyl group-containing group, and even more preferably has a carbonyl group-containing group.

[0021] The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, such as —CF ２ CH ２ OH and -C(CF ３ ) ２ OH is more preferred. The carbonyl group-containing group is a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (—OC(O)NH ２ ), acid anhydride residue (—C(O)OC(O)—), imide residue (—C(O)NHC(O)—, etc.) and carbonate group (—OC(O)O—), and acid anhydride residue is more preferred.

[0022] When the F polymer has a carbonyl group-containing group, the number of carbonyl group-containing groups in the F polymer is 1×10 ６ Preferably, 10 to 5,000 groups per unit, more preferably 100 to 3,000 groups. The number of carbonyl group-containing groups in an F polymer can be quantified by the composition of the polymer or the method described in WO 2020 / 145133. The carbonyl group-containing group may be contained in a unit based on a monomer in the F polymer, or may be contained in a terminal group of the main chain of the F polymer, the former being preferred. Examples of the latter include an F polymer having a carbonyl group-containing group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment.

[0023] The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0024] The F polymer is preferably a polymer having a carbonyl group-containing group containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on a monomer having a carbonyl group-containing group, and more preferably a polymer containing these units in the following order, based on the total units: 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%. Specific examples of such F polymers include the polymers described in WO 2018 / 016644.

[0025] The F particles are particles containing an F polymer, and preferably contain an F polymer as the main component, and preferably consist of an F polymer. The term "containing an F polymer as the main component" means that the content of the F polymer is relatively high compared to the content of each of the other components on a volume basis.

[0026] From the viewpoint of dispersion stability, the D50 of the F particles is preferably 0.1 μm or more, more preferably more than 0.3 μm, and even more preferably 1 μm or more. From the viewpoint of dispersion stability, the D50 of the F particles is preferably 25 μm or less, more preferably 10 μm or less, even more preferably 8 μm or less, and particularly preferably 5 μm or less.

[0027] The specific surface area of ​​F particles is 1 to 50 m ２ / g is preferred, and 1 to 25m ２ The specific surface area of ​​the F particles is preferably 6 m / g. ２ / g or more is more preferable, and 7m ２ / g or more is more preferable, and 8m ２ The specific surface area of ​​the F particles is particularly preferably 25 m / g or more. ２ In this case, the above-mentioned mechanism of action is more likely to be exhibited.

[0028] The F particles may be used alone or in combination of two or more types. When two or more types of F particles are used in combination, different F particles refer to F particles that differ in average particle size, type of F polymer, content of F polymer, presence or absence of other components other than the F polymer, content of other components, or a combination thereof.

[0029] The content of F particles in the aqueous dispersion is preferably 10% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The content of F particles in the aqueous dispersion is preferably 75% by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less. From the viewpoint of further facilitating the development of the above-described mechanism of action, the content of F particles in the aqueous dispersion is preferably 30 to 60% by mass.

[0030] (Specific poly(meth)acrylic acid) The specific poly(meth)acrylic acid has a weight-average molecular weight of 200,000 or more. From the viewpoint of further suppressing viscosity changes over time, the weight-average molecular weight of the specific poly(meth)acrylic acid is preferably 500,000 or more, more preferably 750,000 or more. Furthermore, from the viewpoint of dispersibility of the specific poly(meth)acrylic acid, the weight-average molecular weight of the specific poly(meth)acrylic acid is preferably 1,500,000 or less, more preferably 1,250,000 or less.

[0031] The specific poly(meth)acrylic acid may be at least one selected from the group consisting of a homopolymer, a copolymer, and a crosslinked product of the homopolymer or copolymer. The specific poly(meth)acrylic acid preferably has at least one unit selected from the group consisting of a unit based on a compound represented by the following general formula (I) and a unit based on a compound represented by the following general formula (II):

[0032] In general formula (I), R １ represents a hydrogen atom or a methyl group, R ２ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, a trialkylsilyl group having 3 to 9 carbon atoms, a group represented by the following general formula (IA) or a group represented by the following general formula (IB):

[0033] In general formula (IA), R ３ represents an alkylene group having 1 to 4 carbon atoms, and R ４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 2 to 20.

[0034] In general formula (IB), R ５ ~R ７ each independently represents an alkyl group having 1 to 3 carbon atoms, R ８ represents an alkylene group having 1 to 3 carbon atoms.

[0035] In general formula (II), R １１ represents a hydrogen atom or a methyl group, R １２ and R １３ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0036] R in general formula (I) ２ The alkyl group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 10 carbon atoms.

[0037] R in general formula (IA) ３The alkylene group in the general formula (IA) is preferably an ethylene group, a trimethylene group, a propylene group, or a tetramethylene group, more preferably an ethylene group or a propylene group, and particularly preferably an ethylene group. ４ In general formula (IA), n is preferably an integer of 2 to 10, and more preferably an integer of 4 to 10.

[0038] Among the above, R represented by general formula (I) ２ is preferably a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a group represented by the general formula (IA).

[0039] R in general formula (II) １１ is preferably a hydrogen atom. １２ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom. １３ is more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0040] The specific poly(meth)acrylic acid may have one or more units based on the compound represented by general formula (I). The specific poly(meth)acrylic acid may have one or more units based on the compound represented by general formula (II). The specific poly(meth)acrylic acid may be a homopolymer composed of units based on the compound represented by general formula (I) or a homopolymer composed of units based on the compound represented by general formula (II), or a copolymer having units based on the compound represented by general formula (I) and units based on the compound represented by general formula (II), or may be a crosslinked product of these homopolymers or copolymers.

[0041] The crosslinked product is preferably crosslinked with a (meth)acrylate compound having 2 to 4 (meth)acryloyl groups or a (meth)acrylamide compound having 2 to 4 (meth)acryloyl groups.

[0042] The specific poly(meth)acrylic acid may be neutralized, that is, some or all of the carboxy groups may be in the form of salts, and it is preferred that all of the carboxy groups are in the form of salts.

[0043] The content of the specific poly(meth)acrylic acid in the aqueous dispersion is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, from the viewpoint of effectively suppressing a change in viscosity of the aqueous dispersion over time, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of preventing the viscosity of the aqueous dispersion from becoming too high and workability.

[0044] (pH Buffer) The pH buffer has an optimum pH range of 4 to 10. The optimum pH range refers to the range in which the pH buffer can exhibit its buffering function. The pH buffer according to the present disclosure may have an optimum pH range that falls within at least a portion of the range of 4 to 10. The optimum pH range of the pH buffer is preferably 7 to 10. The pH buffer preferably contains at least one selected from the group consisting of carbonic acid (approximately 5.4 to 7.4), phosphoric acid (approximately 5.4 to 7.4), boric acid (approximately 8.2 to 10.2), formic acid (approximately 2.6 to 4.6), oxalic acid (2.8 to 4.8), acetic acid (approximately 3.8 to 5.8), citric acid (approximately 3.8 to 5.8), isocitric acid (approximately 3.8 to 5.8), lactic acid (approximately 2.7 to 4.7), and ammonium salts thereof, as well as sulfonic acids and amino acids. The numbers in parentheses indicate the optimum pH range.

[0045] Examples of sulfonic acids and amino acids include 2-morpholinoethanesulfonic acid, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, N-(2-acetamido)-2-aminoethanesulfonic acid, 2-hydroxy-3-morpholinopropanesulfonic acid, 2-hydroxy-N-tris(hydroxymethyl)methyl-3-aminopropanoic acid, N-tris(hydroxymethyl)methyl-3-aminopropanoic acid, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 3-morpholinopropanesulfonic acid, N- Examples include tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, N-[tris(hydroxymethyl)methyl]glycine, tris(hydroxymethyl)aminomethane, N,N-bis(2-hydroxyethyl)glycine, glycylglycine, N-cyclohexyl-2-aminoethanesulfonic acid, N-cyclohexyl-3-aminopropanesulfonic acid, and ethylenediaminetetraacetic acid.

[0046] The pH buffer is preferably an ammonium salt of a compound selected from the group consisting of carbonic acid, phosphoric acid, boric acid, formic acid, oxalic acid, acetic acid, citric acid, and lactic acid, more preferably ammonium formate, ammonium oxalate, ammonium acetate, triammonium citrate, diammonium hydrogen phosphate, triammonium phosphate, ammonium borate, ammonium hydrogen carbonate, or ammonium carbonate, and even more preferably ammonium hydrogen carbonate, ammonium carbonate, or ammonium acetate.

[0047] From the viewpoint of effectively suppressing viscosity change of the aqueous dispersion over time, the content of the pH buffer agent in the aqueous dispersion is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and the content of the pH buffer agent is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0048] (Water) The aqueous dispersion of the present disclosure uses water as a dispersion medium. The water content can be appropriately adjusted taking into consideration the coating method, the thickness of the molded product to be produced, and the like. For example, the water content is preferably more than 40% by mass, more preferably 50% by mass or more, and even more preferably 55% by mass or more, relative to the total volume of the aqueous dispersion. The water content is preferably 90% by mass or less, more preferably 80% by mass or less, relative to the total volume of the aqueous dispersion. Specifically, the water content in the aqueous dispersion is preferably 40 to 65% by mass. In this case, the above-mentioned mechanism of action is more easily exhibited.

[0049] The aqueous dispersion of the present disclosure may further contain a water-soluble dispersion medium other than water. The water-soluble dispersion medium is preferably a water-soluble compound that is liquid at 25°C under atmospheric pressure and is classified as polar, such as N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and N-methyl-2-pyrrolidone.

[0050] The solid content concentration in the aqueous dispersion is preferably 20% by volume or more, more preferably 40% by volume or more, based on the total volume of the aqueous dispersion. The solid content concentration is preferably 80% by volume or less. The solid content refers to the total amount of substances that form the solid content in a molded product formed from the aqueous dispersion. Specifically, the F particles, the specific poly(meth)acrylic acid, and the pH buffer are included in the solid content, and if the aqueous dispersion contains other resins, the other resins are also included in the solid content.

[0051] (Surfactant) The aqueous dispersion may further contain a surfactant, preferably a surfactant having no fluorine atoms. When the aqueous dispersion contains a surfactant, the surfactant is nonionic, and the hydrophobic portion of the surfactant preferably has an acetylene group or a polysiloxane group, and the hydrophilic portion preferably has an oxyalkylene group or an alcoholic hydroxyl group. That is, when the aqueous dispersion further contains a surfactant, a nonionic surfactant is preferred, and a polyoxyalkylene alkyl ether, an acetylene-based surfactant, or a silicone-based surfactant is more preferred. These surfactants preferably have an alcoholic hydroxyl group. These surfactants may be used alone or in combination of two or more. From the viewpoint that the polyoxyalkylene alkyl ether stabilizes the long-term dispersibility of the F particles and improves the liquid properties such as the viscosity of the aqueous dispersion, and the silicone surfactant improves the initial dispersibility of the F particles, it is preferable to use a polyoxyalkylene alkyl ether and a silicone-based surfactant in combination. When the aqueous dispersion further contains a surfactant, the amount thereof is preferably 1 to 15% by mass relative to the total mass of the aqueous dispersion, which enhances the affinity between the components and tends to further improve the dispersion stability of the aqueous dispersion.

[0052] Specific examples of silicone surfactants include "BYK-347," "BYK-349," "BYK-378," "BYK-3450," "BYK-3451," "BYK-3455," and "BYK-3456" (all manufactured by BYK Japan KK), "KF-6011," and "KF-6043" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0053] Specific examples of polyoxyalkylene alkyl ethers include "Tergitol TMN-100X" (manufactured by The Dow Chemical Company), "Lutensol TO8", "Lutensol XL70", "Lutensol XL80", "Lutensol XL90", "Lutensol XP80", and "Lutensol M5" (all manufactured by BASF), "Newcol 1305", "Newcol 1308FA", and "Newcol 1310" (all manufactured by Nippon Nyukazai Co., Ltd.), "Leocol TDN-90-80", and "Leocol SC-90" (all manufactured by Lion Specialty Chemicals Co., Ltd.).

[0054] The aqueous dispersion may further contain at least one nonionic water-soluble polymer selected from the group consisting of polyvinyl alcohol-based polymers, polyvinylpyrrolidone-based polymers, and polysaccharides. In this case, not only the dispersion stability but also the rheological properties of the aqueous dispersion are improved, and the handling properties of the aqueous dispersion, such as film-forming properties, are likely to be further improved. As a result, it is easier to form thick molded products or molded products of any shape from the aqueous dispersion. This tendency is particularly pronounced when the water-soluble polymer has nonionic hydroxyl groups. The polyvinyl alcohol-based polymer may be partially acetylated or partially acetalized polyvinyl alcohol.

[0055] Examples of polysaccharides include glycogens, amicropectins, dextrins, glucans, fructans, chitins, amyloses, agaroses, amicropectins, and celluloses. Examples of celluloses include methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. The nonionic water-soluble polymer is preferably a nonionic polysaccharide, more preferably a nonionic cellulose, and even more preferably hydroxymethyl cellulose, hydroxyethyl cellulose, or hydroxypropyl cellulose. Specific examples of such nonionic polysaccharides include the "Sunrose (registered trademark)" series (manufactured by Nippon Paper Industries Co., Ltd.), the "Metolose (registered trademark)" series (manufactured by Shin-Etsu Chemical Co., Ltd.), and "HEC CF Grade" (manufactured by Sumitomo Seika Chemicals Co., Ltd.).

[0056] When the aqueous dispersion further contains a nonionic water-soluble polymer, the content of the nonionic water-soluble polymer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, relative to the total amount of the aqueous dispersion. The content is preferably less than 1% by mass. The ratio of the mass of the water-soluble polymer to the mass of the F particles in the aqueous dispersion is preferably 0.001 or more, more preferably 0.01 or more. The ratio is preferably less than 0.1.

[0057] (Other Components) The aqueous dispersion may contain particles of other fluororesins other than F polymers (hereinafter also referred to as "other F particles"). Examples of other fluororesins include melt processable fluororesins other than F polymers and non-melt processable fluororesins, and from the viewpoint of moldability, melt processable fluororesins other than F polymers are preferred. The melt processable fluororesins other than F polymers are melt processable fluororesins that do not contain TFE units. When F particles and other F particles are used in combination, the proportion of the other F particles in the total amount of the F particles and the other F particles is preferably less than 50% by mass, more preferably 25% by mass or less. Moreover, the proportion is preferably 0.1% by mass or more, more preferably 1% by mass or more.

[0058] The aqueous dispersion may contain a resin other than the fluororesin. The other resin may be contained in the aqueous dispersion as powder particles or dissolved or dispersed in water. Examples of the other resin include polyester resins such as liquid crystalline aromatic polyesters, imide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. The other resin is preferably an aromatic polymer, and more preferably at least one aromatic imide polymer selected from the group consisting of aromatic polyimides, aromatic polyamic acids, aromatic polyamideimides, and aromatic polyamideimide precursors. The aromatic polymer is preferably contained in the aqueous dispersion as a varnish dissolved in water. Specific examples of aromatic imide polymers include the "UPIA-AT" series (manufactured by Ube Industries, Ltd.), the "NEOPLIM (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company, Inc.), the "SPIXERIA (registered trademark)" series (manufactured by Somar), the "Q-PILON (registered trademark)" series (manufactured by PI Technical Research Institute), the "WINGO" series (manufactured by Wingo Technology Co., Ltd.), the "TOMAID (registered trademark)" series (manufactured by T&K TOKA Corporation), the "KPI-MX" series (manufactured by Kawamura Sangyo Co., Ltd.), "HPC-1000" and "HPC-2100D" (all manufactured by Resonac Corporation).

[0059] When the aqueous dispersion contains other resins, the content of the other resins relative to the F particles is preferably 0.1% by volume or more, more preferably 1% by volume or more, and is preferably 15% by volume or less, more preferably 10% by volume or less.

[0060] The aqueous dispersion may further contain an inorganic filler. In this case, a molded product produced from the aqueous dispersion is likely to have excellent electrical properties and low linear expansion. The inorganic filler is preferably a nitride filler or an inorganic oxide filler, more preferably a boron nitride filler, a beryllia filler (a beryllium oxide filler), a silicate filler (a silica filler, a wollastonite filler, a talc filler), or a metal oxide filler (such as cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, or titanium oxide), and even more preferably a silica filler.

[0061] It is preferable that at least a portion of the surface of the inorganic filler is surface-treated with a silane coupling agent (3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, etc.).

[0062] The D50 of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less. The D50 is preferably 0.01 μm or more, more preferably 0.1 μm or more. The shape of the inorganic filler may be any of granular, needle-like (fibrous), and plate-like. Specific shapes of the inorganic filler include spherical, scale-like, layer-like, leaf-like, apricot-like, columnar, cockscomb-like, equiaxed, leaf-like, mica-like, block-like, flat-plate-like, wedge-like, rosette-like, net-like, and prismatic.

[0063] The inorganic filler may be used alone or in combination of two or more. When the aqueous dispersion further contains an inorganic filler, the content of the inorganic filler is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, based on the total mass of the aqueous dispersion.

[0064] Specific examples of suitable inorganic fillers include silica fillers (such as the "Admafine (registered trademark)" series manufactured by Admatechs Co., Ltd.), zinc oxide surface-treated with an ester such as propylene glycol dicaprate (such as the "FINEX (registered trademark)" series manufactured by Sakai Chemical Industry Co., Ltd.), spherical fused silica fillers (such as the "SFP (registered trademark)" series manufactured by Denka Co., Ltd.), titanium oxide fillers coated with polyhydric alcohol and inorganic substances (such as the "Tipaque (registered trademark)" series manufactured by Ishihara Sangyo Kaisha, Ltd.), and rutile-type titanium oxide fillers surface-treated with alkylsilane (such as the "Tepaque (registered trademark)" series manufactured by Ishihara Sangyo Kaisha, Ltd.). Examples of fillers include the "JMT (registered trademark)" series manufactured by Ika Corporation, hollow silica fillers (the "E-SPHERES" series manufactured by Taiheiyo Cement Corporation, the "Silinax" series manufactured by Nittetsu Mining Co., Ltd., and the "Ecocospher" series manufactured by Emerson & Cumming Co., Ltd.), talc fillers (the "SG" series manufactured by Nippon Talc Co., Ltd., and the like), steatite fillers (the "BST" series manufactured by Nippon Talc Co., Ltd., and the like), and boron nitride fillers (the "UHP" series manufactured by Showa Denko KK, and the "Denka Boron Nitride" series ("GP" and "HGP" grades) manufactured by Denka Company, Ltd., and the like).

[0065] The aqueous dispersion may further contain a silane coupling agent in order to further improve the miscibility between the F polymer and the inorganic filler. Examples of the silane coupling agent include the same silane coupling agents as those that may be used for the surface treatment of the inorganic filler, and the preferred ranges are also the same. When the aqueous dispersion contains a silane coupling agent, the content of the silane coupling agent in the aqueous dispersion (excluding the silane coupling agent used for the surface treatment of the inorganic filler) is preferably 1 to 10% by volume relative to the total volume of the aqueous dispersion.

[0066] The aqueous dispersion may further contain additives such as a thixotropic agent, a viscosity modifier, an antifoaming 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 material, a release agent, a surface treatment agent, a flame retardant, a conductive filler, or a preservative.

[0067] (Physical Properties of Aqueous Dispersion) The pH of the aqueous dispersion is 4 to 10, more preferably 7 to 10, and even more preferably 8 to 10. When preparing the aqueous dispersion, in addition to the above-mentioned pH buffer, another basic compound such as ammonia or an amine may be used in combination. The viscosity of the aqueous dispersion at 25°C is preferably 10,000 mPa·s or less, more preferably 3,000 mPa·s or less. The viscosity of the aqueous dispersion at 25°C is preferably 500 mPa·s or more, more preferably 600 mPa·s or more. When the aqueous dispersion is stored in a container at 25°C for one month, the rate of change in viscosity before and after storage (hereinafter also referred to as "viscosity retention rate") expressed by the following formula is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more. Viscosity retention rate = viscosity after storage (mPa·s) / viscosity before storage (mPa·s) × 100

[0068] The thixotropy ratio of the aqueous dispersion is preferably equal to or less than 6, more preferably equal to or less than 5, and even more preferably equal to or less than 4. The thixotropy ratio of the aqueous dispersion is preferably equal to or greater than 1, and more preferably equal to or greater than 2. When the thixotropy ratio of the aqueous dispersion is within the above range, sedimentation of the F particles is more easily suppressed.

[0069] <Method for producing aqueous dispersion> The aqueous dispersion of the present disclosure can be obtained by mixing F particles, a specific poly(meth)acrylic acid, a pH buffer, and water, and, if necessary, other additives such as other resins, surfactants, silane coupling agents, etc. The order of mixing is not particularly limited, and the mixing method may be either simultaneous mixing or multiple divided mixing.

[0070] Examples of mixing devices for obtaining the aqueous dispersion of the present disclosure include stirring devices equipped with blades, such as a Henschel mixer, a pressure kneader, a Banbury mixer, and a planetary mixer; grinding devices equipped with media, such as a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC mill, a spike mill, and an agitator mill; and dispersing devices equipped with other mechanisms, such as a microfluidizer, a nanomizer, an ultimizer, an ultrasonic homogenizer, a dissolver, a disper, a high-speed impeller, a thin film rotation-type high-speed mixer, a planetary mixer, and a V-type mixer.

[0071] <Applications of aqueous dispersion> The applications of the aqueous dispersion of the present disclosure are not particularly limited, and can be used, for example, for producing molded articles. In particular, the aqueous dispersion of the present disclosure is suitable for applications in which it is desired to favorably exhibit the properties of the F polymer contained in the aqueous dispersion.

[0072] Aqueous dispersions are useful as materials for imparting insulation, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and the like. Specifically, aqueous dispersions can be used in printed wiring boards, thermal interface materials, power module substrates, coils used in power devices such as motors, automotive engines, heat exchangers, vials, syringes, ampoules, medical wires, secondary batteries such as lithium ion batteries, primary batteries such as lithium batteries, radical batteries, solar cells, fuel cells, lithium ion capacitors, hybrid capacitors, capacitors (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical switching elements, electrode binders, electrode separators, electrodes (positive electrodes, negative electrodes), and the like. Furthermore, aqueous dispersions are also useful as adhesives for bonding parts. Specifically, aqueous dispersions can be used for bonding ceramic parts, metal parts, electronic parts such as IC chips, resistors, and capacitors on semiconductor element and module component substrates, bonding circuit boards and heat sinks, and bonding LED chips to substrates.

[0073] <Laminate and method for producing laminate> The method for producing a laminate of the present disclosure involves applying the aqueous dispersion of the present disclosure to a substrate, heating to remove the water, and further heating to melt and sinter the F particles.

[0074] Examples of the substrate include metal substrates (metal foils such as copper, nickel, aluminum, titanium, and alloys thereof), heat-resistant resin films (heat-resistant resin films such as polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyaryl ether ketone, polyamideimide, liquid crystalline polyester, and tetrafluoroethylene-based polymers), prepreg substrates (precursors of fiber-reinforced resin substrates), ceramic substrates (ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride), and glass substrates.

[0075] The shape of the substrate may be flat, curved, or uneven. The substrate may be in the form of a foil, plate, film, or fiber (woven fabric, nonwoven fabric, etc.). The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm. The substrate surface may be surface-treated with a silane coupling agent or may be plasma-treated. Examples of such silane coupling agents include those similar to those used for surface treatment of inorganic fillers. The peel strength between the fluororesin layer and the substrate is preferably 10 N / cm or more, more preferably 15 N / cm or more. The peel strength is preferably 100 N / cm or less.

[0076] Methods for applying the aqueous dispersion include coating, droplet ejection, and immersion, with roll coating, knife coating, bar coating, die coating, and spraying being preferred. Heating to remove water is preferably performed at 100 to 200°C for 0.1 to 30 minutes. During heating, water does not need to be completely removed; it is sufficient to remove water to the extent that the layer formed by the packing of F particles and composite particles can maintain a self-supporting film. During heating, air may be blown to promote water removal by air drying. Heating to bake the F polymer is preferably performed at a temperature equal to or higher than the baking temperature of the F polymer, more preferably at 360 to 400°C for 0.1 to 30 minutes. Examples of heating devices for each heating method include ovens and forced-air drying furnaces. The heat source in the device may be a contact-type heat source (hot air, hot plate, etc.) or a non-contact-type heat source (infrared, etc.). Each heating method may be performed under normal pressure or reduced pressure. The atmosphere during each heating step may be either an air atmosphere or an inert gas atmosphere (helium gas, neon gas, argon gas, nitrogen gas, etc.).

[0077] The fluororesin layer is formed through the steps of applying an aqueous dispersion and heating. These steps may be performed once each, or may be repeated two or more times. For example, an aqueous dispersion may be applied to the surface of a substrate and heated to form a fluororesin layer, and then an aqueous dispersion may be applied to the surface of the fluororesin layer and heated to form a second fluororesin layer. Alternatively, an aqueous dispersion may be applied to the surface of a substrate and heated to remove water, and then an aqueous dispersion may be applied to the surface and heated to form a fluororesin layer. The aqueous dispersion may be applied to only one surface of the substrate, or may be applied to both surfaces of the substrate. In the former case, a laminate having a substrate layer and a fluororesin layer on one surface of the substrate layer is obtained, and in the latter case, a laminate having a substrate layer and a fluororesin layer on both surfaces of the substrate layer is obtained.

[0078] The thickness of the fluororesin layer can be appropriately selected depending on the application, and may be, for example, 25 μm or more, 30 μm or more, or 40 μm or more, or may be 200 μm or less.

[0079] Suitable specific examples of the laminate include a metal-clad laminate having a metal foil and a fluororesin layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and a fluororesin layer on both surfaces of the polyimide film.

[0080] Laminates formed from aqueous dispersions are useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, heat dissipation parts, etc. Specific examples include electric wire coating materials (aircraft electric wires, etc.), enameled wire coating materials used in motors of electric vehicles, etc., electrical insulating tapes, insulating tapes for oil drilling, oil transport hoses, hydrogen tanks, materials for printed circuit boards, separation membranes (microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode binders (for lithium secondary batteries, for fuel cells, etc.), copy rolls, furniture, automobile dashboards, covers for home appliances, etc., sliding members (load bearings, yaw bearings, sliding shafts, valves, bearings, bushings, seals, thrust washers, wear rings, etc.), and the like. useful in applications such as: pins, pistons, slide switches, gears, cams, conveyor belts, food transport belts, etc.), tension ropes, wear pads, wear strips, tube lamps, test sockets, wafer guides, wear parts for centrifugal pumps, chemical and water supply pumps, tools (shovels, files, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, dies, toilets, container coating materials, heat dissipation substrates for mounting power devices, heat dissipation components for wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat dissipation fins, metal heat sinks, blades for windmills, wind power generation equipment, aircraft, etc., housings for personal computers and displays, electronic device materials, interior and exterior parts of automobiles, sealing materials for processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, plasma processing equipment, etc., heat dissipation components in processing units for sputtering and various dry etching equipment, electromagnetic wave shielding, etc.

[0081] Laminates formed from the aqueous dispersion of the present disclosure are useful as electronic substrate materials such as flexible printed wiring boards and rigid printed wiring boards, protective films, and heat dissipation substrates, particularly heat dissipation substrates for automobiles.

[0082] Next, embodiments of the present disclosure will be specifically described using examples, but the embodiments of the present disclosure are not limited to these examples.

[0083] The following F particles were prepared: F particles 1: containing TFE units, NAH units, and PPVE units, and having a carbonyl group-containing group with a main chain carbon number of 1×10 ６ Tetrafluoroethylene polymer particles (melting temperature: 300°C) with 1000 particles per particle (D50: 2.1 μm, specific surface area: 8 m ２ / g) F particle 2: containing TFE units and PPVE units, and having a carbonyl group-containing group with a main chain carbon number of 1 × 10 ６ Tetrafluoroethylene polymer particles (melting temperature: 300°C) with 250 particles per particle (D50: 1.6 μm, specific surface area: 16 m ２ / g) F particle 3: containing TFE units and PPVE units, and having a carbonyl group-containing group with a main chain carbon number of 1 × 10 ６ Tetrafluoroethylene polymer particles (melting temperature: 300°C) with 250 particles per particle (D50: 3.6 μm, specific surface area: 6 m ２ / g)

[0084] The following polyacrylic acids were prepared: PAA1: a copolymer of acrylic acid and 2-hydroxyethyl acrylate in a molar ratio of 1:1, crosslinked with polyethylene glycol diacrylate, and having a weight-average molecular weight Mw of 1,000,000; PAA2: a copolymer of acrylic acid and 2-hydroxyethyl acrylate in a molar ratio of 1:1, not crosslinked with polyethylene glycol diacrylate, and having a weight-average molecular weight Mw of 250,000; PAA3: a copolymer of acrylic acid and 2-hydroxyethyl acrylate in a molar ratio of 1:1, not crosslinked with polyethylene glycol diacrylate, and having a weight-average molecular weight Mw of 150,000.

[0085] Example 1 An aqueous dispersion 1 containing 40% by mass of F particles 1, 0.1% by mass of PAA1, and ammonium bicarbonate (optimal pH range: 9.0 to 10.0) and adjusted to pH 9 with ammonia was prepared by shear stirring.

[0086] Example 2 Aqueous dispersion 2 was prepared in the same manner as in Example 1, except that PAA1 was replaced with PAA2 having a Mw of 250,000.

[0087] Example 3 Aqueous dispersion 3 was prepared in the same manner as in Example 1, except that PAA1 was replaced with PAA3 having a Mw of 150,000.

[0088] Example 4 Aqueous dispersion 4 was prepared in the same manner as in Example 1, except that only ammonia was used instead of the combined use of ammonium bicarbonate and ammonia.

[0089] Example 5 Aqueous dispersion 5 was prepared in the same manner as in Example 1, except that ammonium bicarbonate and ammonia were not added.

[0090] <Evaluation (Part 1)> The pH of the obtained aqueous dispersions 1 to 5 was measured. In addition, the obtained aqueous dispersions 1 to 5 were stored in a container at 25°C for 1 month, and the viscosity was measured before and after storage. The results are shown in Table 1.

[0091]

[0092] <Evaluation (Part 2)> Aqueous dispersions 6 to 12 were prepared in the same manner as in Example 1, except that the type and content of F particles were changed as shown in Table 2 below. Each of aqueous dispersions 1 and 6 to 12 was stored at 25°C for one month, and the viscosity was measured before and after storage. The viscosity change rate (viscosity after storage / viscosity before storage x 100) was evaluated as "A" if it was 90% or more and less than 90%, as "B" if it was 80% or more and less than 90%, and as "C" if it was 50% or more and less than 80%. The results are summarized in Table 2. The viscosity of each aqueous dispersion before storage was 500 to 2000 mPa s.

[0093]

[0094] The disclosure of Japanese Patent Application No. 2023-131640 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. An aqueous dispersion having a pH of 4 to 10, comprising particles containing a heat-fusible tetrafluoroethylene polymer, poly(meth)acrylic acid having a weight-average molecular weight of 200,000 or more, a pH buffer having an optimum pH range of 4 to 10, and water.

2. The aqueous dispersion according to claim 1, having a viscosity of 500 mPa·s or more at 25°C.

3. The aqueous dispersion according to claim 1 or 2, wherein the heat-fusible tetrafluoroethylene polymer contains a unit based on tetrafluoroethylene and at least one of a unit based on perfluoro(alkyl vinyl ether) and a unit based on hexafluoropropylene.

4. The aqueous dispersion according to claim 1 or 2, wherein the heat-fusible tetrafluoroethylene polymer has a carbonyl group-containing group.

5. The heat-meltable tetrafluoroethylene polymer has a main chain carbon number of 1×10 ６ 3. The aqueous dispersion according to claim 1, wherein each of the aqueous dispersion particles has 10 to 5,000 carbonyl-containing groups.

6. The aqueous dispersion according to claim 1 or 2, wherein the particles containing the heat-fusible tetrafluoroethylene polymer have an average particle size of 10 μm or less.

7. The particles containing the heat-fusible tetrafluoroethylene polymer have a specific surface area of ​​6 m ２ The aqueous dispersion according to claim 1 or 2, wherein the viscosity is greater than 1 / g.

8. The aqueous dispersion according to claim 1 or 2, wherein the content of particles containing the heat-fusible tetrafluoroethylene polymer is 60 mass % or less.

9. The aqueous dispersion according to claim 1 or 2, wherein the weight average molecular weight of the poly(meth)acrylic acid is 500,000 to 1,500,000.

10. The aqueous dispersion according to claim 1 or 2, wherein the poly(meth)acrylic acid has at least one unit selected from the group consisting of units based on a compound represented by the following general formula (I) and units based on a compound represented by the following general formula (II): In general formula (I), R １ represents a hydrogen atom or a methyl group, R ２ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, a trialkylsilyl group having 3 to 9 carbon atoms, a group represented by the following general formula (IA) or a group represented by the following general formula (IB), In general formula (IA), R ３ represents an alkylene group having 1 to 4 carbon atoms; R ４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 2 to 20. In general formula (IB), R ５ ~R ７ each independently represents an alkyl group having 1 to 3 carbon atoms; R ８ represents an alkylene group having 1 to 3 carbon atoms. In general formula (II), R １１ represents a hydrogen atom or a methyl group, R １２ and R １３ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

11. The aqueous dispersion according to claim 1 or 2, wherein the pH buffer comprises at least one selected from the group consisting of carbonic acid, phosphoric acid, boric acid, formic acid, oxalic acid, acetic acid, citric acid, isocitric acid, lactic acid, and ammonium salts thereof, as well as sulfonic acids and amino acids.

12. The aqueous dispersion according to claim 1 or 2, having a viscosity at 25° C. of 10,000 mPa·s or less.

13. The aqueous dispersion according to claim 1 or 2, further comprising a surfactant having no fluorine atom.

14. A method for producing a laminate, comprising applying the aqueous dispersion according to claim 1 or 2 to a substrate, heating to remove the water, and further heating to melt and sinter the particles containing the heat-fusible tetrafluoroethylene-based polymer.

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