Aqueous dispersion, and method for producing laminate

Abstract

The 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 an optimum pH range of 4 to 10, and water, and has a pH value of 4 to 10.

Description

Technical Field

[0001] This disclosure relates to aqueous dispersions and methods for manufacturing laminates. Background Technology

[0002] Fluoropolymers possess excellent electrical properties, water and oil repellency, chemical resistance, and heat resistance, making them suitable for various applications. In particular, tetrafluoroethylene polymers, due to their superior mold release properties, electrical insulation, water and oil repellency, chemical resistance, weather resistance, and heat resistance, are processed into various molded products for application.

[0003] For example, Patent Document 1 describes an aqueous dispersion of fluorinated resin containing fluorinated resin particles with a specific range of volume average particle size. From the viewpoints of improving dispersibility and redispersibility and suppressing sedimentation, this aqueous dispersion of fluorinated resin preferably contains a water-soluble thickener.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-052211 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] Patent Document 1 achieves improved dispersibility and sedimentation suppression of fluoropolymer particles by adding a water-soluble thickener. However, even with this configuration, it has been found that fluoropolymer particles will still settle over time, resulting in viscosity changes. If the viscosity of the aqueous dispersion changes, its operation becomes difficult.

[0009] In light of this situation, one embodiment of this disclosure relates to providing an aqueous dispersion in which viscosity changes over time are suppressed, and a method for manufacturing a laminate using the aqueous dispersion.

[0010] Technical solutions adopted to solve technical problems

[0011] This disclosure includes the following forms.

[0012] <1> An aqueous dispersion containing particles comprising a hot-melt tetrafluoroethylene polymer, poly(meth)acrylic acid with a weight-average molecular weight of 200,000 or more, a pH buffer with an optimal pH range of 4 to 10, and water, wherein the pH value is 4 to 10.

[0013] <2> The aqueous dispersion as described in <1> has a viscosity of 500 mPa·s or higher at 25°C.

[0014] <3> The aqueous dispersion as described in <1> or <2>, wherein the hot-melt tetrafluoroethylene polymer comprises: a tetrafluoroethylene-based unit, a perfluoro(alkyl vinyl ether)-based unit, and a hexafluoropropylene-based unit.

[0015] <4> An aqueous dispersion as described in any one of <1> to <3>, wherein the hot-melt tetrafluoroethylene polymer has a carbonyl group.

[0016] <5> An aqueous dispersion as described in any one of <1> to <4>, wherein the hot-melt tetrafluoroethylene polymer per 1×10 6 Each main chain has 10 to 5000 carbon atoms containing carbonyl groups.

[0017] <6> An aqueous dispersion as described in any one of <1> to <5>, wherein the average particle size of the particles comprising the hot-melt tetrafluoroethylene polymer is less than 10 μm.

[0018] <7> An aqueous dispersion as described in any one of <1> to <6>, wherein the particles comprising a thermoplastic tetrafluoroethylene polymer have a specific surface area greater than 6 m². 6 / g.

[0019] <8> An aqueous dispersion as described in any one of <1> to <7>, wherein the content of particles comprising a hot-melt tetrafluoroethylene polymer is less than 60% by mass.

[0020] <9> An aqueous dispersion as described in any one of <1> to <8>, wherein the poly(meth)acrylic acid has a weight-average molecular weight of 500,000 to 1,500,000.

[0021] <10> An aqueous dispersion as described in any one of <1> to <7>, wherein the poly(meth)acrylic acid has at least one unit selected from units of compounds represented by general formula (I) and units of compounds represented by general formula (II):

Chemical Formula 1

[0022] In general formula (I), R 1 R represents a hydrogen atom or a methyl group. 2 The group 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). [Chemical Formula 2]

[0023] In the general formula (IA), R3 R represents an alkylene group having 1 to 4 carbon atoms. 4 This indicates a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, where n represents an integer from 2 to 20.

Chemical Formula 3

[0024] In the general formula (IB), R 5 ~R 7 Each of the alkyl groups having 1 to 3 carbon atoms is represented independently, R 8 Indicates alkylene groups having 1 to 3 carbon atoms. [Chemical Formula 4]

[0025] In general formula (II), R 11 R represents a hydrogen atom or a methyl group. 12 and R 13 Each can be independently represented by a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0026] <11> An aqueous dispersion as described in any one of <1> to <10>, wherein the pH buffer comprises at least one selected from carbonic acid, phosphoric acid, boric acid, formic acid, oxalic acid, acetic acid, citric acid, isocitric acid, lactic acid, and ammonium salts of these acids, as well as sulfonic acids and amino acids.

[0027] <12> An aqueous dispersion as described in any one of <1> to <11>, wherein its viscosity at 25°C is less than 10000 mPa·s.

[0028] <13> An aqueous dispersion as described in any one of <1> to <12>, further comprising a surfactant that does not have fluorine atoms.

[0029] <14> A method for manufacturing a laminate, wherein an aqueous dispersion of any one of <1> to <13> is applied to a substrate, the water is removed by heating, and the particles comprising a thermoplastic tetrafluoroethylene polymer are further heated to melt and sinter.

[0030] Invention Effects

[0031] According to one embodiment of the present disclosure, an aqueous dispersion in which viscosity changes over time are suppressed and a method for manufacturing a laminate using the aqueous dispersion can be provided. Detailed Implementation

[0032] The embodiments of this disclosure will now be described in detail. However, this disclosure is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless otherwise specified. Similarly, numerical values ​​and their ranges are not intended to limit the embodiments of this disclosure.

[0033] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes whose purpose can be achieved when they cannot be clearly distinguished from other processes.

[0034] In this disclosure, the numerical range represented by “~” includes the values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0035] In this disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the aqueous dispersion, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the aqueous dispersion.

[0036] In this disclosure, the particles corresponding to each component may include multiple types. In the case where multiple particles corresponding to each component are present in the aqueous dispersion, unless otherwise specified, the particle size of each component refers to the value of a mixture of the multiple particles present in the aqueous dispersion.

[0037] In this disclosure, the terms "layer" or "film" include, in addition to the case where the layer or film is formed throughout the region in which it is observed, the case where it is formed only in a part of the region.

[0038] In this disclosure, the term "stacked" refers to stacking layers together, which can be two or more layers combined together, or two or more layers that can be detached.

[0039] In this disclosure, a "unit" in a polymer refers to a group of atoms based on a monomer formed by the polymerization of the monomer. A unit can be formed directly through a polymerization reaction, or it can be obtained by processing the polymer to convert a portion of the unit into another structure. Hereinafter, a unit based on monomer a will also be referred to as a "monomer a unit".

[0040] In this disclosure, the “melting temperature” of tetrafluoroethylene polymers refers to the temperature corresponding to the maximum value of the polymer’s melting peak as determined by differential scanning calorimetry (DSC).

[0041] In this disclosure, the “melt flow rate” of tetrafluoroethylene polymers refers to the melt flow rate of polymers specified in JIS K 7210-1:2014 (ISO 1133-1:2011).

[0042] In this disclosure, the "glass transition temperature (Tg)" of tetrafluoroethylene polymers is a value determined by analyzing the polymer using the dynamic viscoelasticity assay (DMA).

[0043] In this disclosure, the "weight-average molecular weight" of poly(meth)acrylic acid is obtained by converting it into the weight-average molecular weight of polystyrene in gel permeation chromatography (GPC) analysis.

[0044] In this disclosure, the average particle size refers to the volume average particle size (D50), which is the cumulative 50% diameter of the particle's volume as determined by laser diffraction and scattering. That is, the particle size distribution is determined by laser diffraction and scattering, and a cumulative curve is obtained with the total volume of the particle group as 100%. The particle D50 is obtained by dispersing the particles in water and analyzing them using a laser diffraction and scattering particle size distribution measuring device (e.g., the BECKMAN COULTER laser diffraction and scattering particle size distribution measuring device "LS-13 320").

[0045] In this disclosure, the "specific surface area" is a value obtained by measuring and calculating the particles using the gas adsorption (constant volume method) BET multi-point method, and is obtained using a BET specific surface area measuring device (e.g., NOVA4200e (manufactured by Quanta Chromium Instruments Co., Ltd.)).

[0046] In this disclosure, the viscosity of the aqueous dispersion was determined by measuring the aqueous dispersion using a type B viscometer at 25°C and 30 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0047] In this disclosure, the "thixotropic ratio" of the aqueous dispersion refers to the value calculated by dividing the viscosity η1 measured at 30 rpm by the viscosity η2 measured at 60 rpm. Each viscosity measurement was repeated three times, and the average of the three measurements was taken.

[0048] <Aqueous Dispersion>

[0049] The aqueous dispersion disclosed herein contains particles comprising a hot-melt tetrafluoroethylene polymer, poly(meth)acrylic acid with a weight-average molecular weight of 200,000 or more, a pH buffer with an optimal pH range of 4 to 10, and water.

[0050] Hereinafter, hot-melt tetrafluoroethylene polymers are also referred to as "F polymers," and particles containing hot-melt tetrafluoroethylene polymers are also referred to as "F particles." Furthermore, poly(meth)acrylic acid with a weight-average molecular weight of 200,000 or more is also referred to as "specific poly(meth)acrylic acid." Additionally, pH buffers with an optimal pH range of 4 to 10 are also simply referred to as "pH buffers."

[0051] In the aqueous dispersion described above, the sedimentation of F particles is suppressed, as is the viscosity change over time. The reason for this is not yet clear, but it is speculated as follows.

[0052] Aqueous dispersions containing F particles tend to have a decreased pH over time. Although poly(meth)acrylic acid (PMA) exhibits high thickening properties due to its functional groups, it is prone to denaturation due to pH changes in aqueous dispersions over time. Furthermore, when PMA contains methacrylate-based units as copolymer components, ester hydrolysis is readily observed. Therefore, it is believed that the thickening properties of PMA decrease over time.

[0053] Based on this, it is believed that by increasing the weight average molecular weight of poly(meth)acrylic acid to above 200,000, increasing the number of structural units to increase the absolute number of functional groups that play a thickening role, and by using a pH buffer with an optimal pH range of 4 to 10 to maintain the pH value of the aqueous dispersion within the range of 4 to 10, the thickening function brought by poly(meth)acrylic acid can be maintained over time.

[0054] Furthermore, the inventors have discovered that this effect is more likely to be significant when the average particle size of F particles is small, the specific surface area of ​​F particles is large, the interaction between F particles and water is large, or when the content of F particles in the aqueous dispersion is within a certain range, the liquid viscosity of the aqueous dispersion is low, and the degree of freedom of the F particles themselves is high.

[0055] The following describes the components contained in the aqueous dispersion.

[0056] (F particle)

[0057] The F polymer contained in the F particles is a polymer containing tetrafluoroethylene (hereinafter also referred to as "TFE unit")-based units (hereinafter also referred to as "TFE units"). From the viewpoint of advantageously exhibiting the properties brought about by the TFE units, the content of TFE units in the F polymer is preferably 50 mol% or more, more preferably 90 mol% or more, relative to all units in the F polymer. The above-mentioned content can be 99 mol% or less, or 98 mol% or less.

[0058] Polymer F is thermomeltable. Thermomeltable polymers are polymers that exhibit a melt flow rate of 1–1000 g / 10 minutes under a load of 49 N.

[0059] From the viewpoint of heat resistance, the melting temperature of polymer F is preferably above 200°C, more preferably above 260°C. From the viewpoint of ease of processing, the melting temperature of polymer F is preferably below 325°C, more preferably below 320°C.

[0060] From the viewpoint of heat resistance, the glass transition temperature of polymer F is preferably 50°C or higher, more preferably 75°C or higher. From the viewpoint of ease of processing, the glass transition temperature of polymer F is preferably 150°C or lower, more preferably 125°C or lower.

[0061] From the viewpoint of advantageously exhibiting the properties brought about by fluorine atoms, such as electrical properties and heat resistance, the fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72% to 76% by mass.

[0062] The surface tension of polymer F is preferably 16–26 mN / m. Furthermore, the surface tension of polymer F can be determined by placing droplets of a wetting index reagent (manufactured by Fujifilm and Wakamitsu Pharmaceutical Co., Ltd.) onto a plate made of polymer F.

[0063] Polymer F is preferably polytetrafluoroethylene (PTFE), polymers containing TFE units and ethylene-based units, polymers containing TFE units and propylene-based units, polymers containing TFE units and perfluoro(alkyl vinyl ether) (PAVE)-based units (PAVE units) (PFA), and polymers containing TFE units and hexafluoropropylene-based units (FEP). Polymers containing at least one of TFE units, PAVE units, and hexafluoropropylene-based units are more preferred. From the viewpoint of properties such as adhesion and processability, PFA and FEP are further preferred, and PFA is more preferred. These polymers may also contain units based on other comonomers.

[0064] PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3 and CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and more preferably PPVE.

[0065] In particular, from the viewpoint of obtaining an aqueous dispersion with high uniformity and improving the adhesion of the resulting molded product, polymer F preferably has oxygen-containing polar groups, more preferably has hydroxyl groups or carbonyl groups, and even more preferably has carbonyl groups.

[0066] The hydroxyl group is preferably an alcohol hydroxyl group, more preferably -CF2CH2OH and -C(CF3)2OH.

[0067] The carbonyl group is preferably a carboxyl group, alkoxycarbonyl group, amide group, isocyanate group, urethane group (-OC(O)NH2), acid anhydride residue (-C(O)OC(O)-), imide residue (-C(O)NHC(O)-, etc.) and carbonate group (-OC(O)O-), and more preferably an acid anhydride residue.

[0068] When polymer F contains carbonyl groups, the preferred number of carbonyl groups in polymer F is 1 × 10⁻⁶. 6 The number of carbon atoms in the main chain ranges from 10 to 5000, more preferably from 100 to 3000. Furthermore, the number of carbonyl groups in the F polymer can be quantified according to the polymer composition or the method described in International Publication No. 2020 / 145133.

[0069] The carbonyl group can be contained in the monomer-based unit of the F polymer or in the terminal group of the F polymer backbone, with the former being preferred. Examples of the latter include F polymers having carbonyl groups as terminal groups derived from polymerization initiators, chain transfer agents, etc., and F polymers obtained by plasma treatment or ionizing radiation treatment of F polymers.

[0070] Monomers containing carbonyl groups are preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), with NAH being more preferred.

[0071] The F polymer is preferably a polymer containing carbonyl groups, comprising TFE units and PAVE units, and more preferably a polymer comprising TFE units, PAVE units, and units based on monomers containing carbonyl groups, and comprising, in sequence, 90-99 mol%, 0.99-9.97 mol%, and 0.01-3 mol% of these units relative to all units. A specific example of such an F polymer is the polymer described in International Publication No. 2018 / 016644.

[0072] F particles are particles containing F polymer, preferably with F polymer as the main component, and more preferably composed of F polymer. F polymer as the main component means that, on a volume basis, the content of F polymer is relatively higher than that of other components.

[0073] From the viewpoint of dispersion stability, the D50 of the F particles is preferably 0.1 μm or more, more preferably greater 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.

[0074] The preferred specific surface area of ​​F particles is 1–50 m². 2 / g, preferably 1-25m 2 / g. The specific surface area of ​​F particles is more preferably greater than 6m². 2 / g, further optimized 7m 2 / g or more, with 8m being the preferred choice 2 / g or more. Furthermore, the specific surface area of ​​the F particles is preferably 25m². 2 Below / g. In this case, the above-mentioned mechanism of action is more easily manifested.

[0075] F particles can 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 with different average particle sizes, different types of F polymers, different contents of F polymers, different presence or absence of other components besides F polymers, different contents of other components, or different combinations of these.

[0076] 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. Furthermore, 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 that the above-mentioned mechanism of action is more readily apparent, the content of F particles in the aqueous dispersion is preferably 30% to 60% by mass.

[0077] (Specific poly(meth)acrylic acid)

[0078] 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 specific poly(meth)acrylic acid preferably has a weight-average molecular weight of 500,000 or more, more preferably 750,000 or more. Furthermore, from the viewpoint of the dispersibility of the specific poly(meth)acrylic acid, the specific poly(meth)acrylic acid preferably has a weight-average molecular weight of 1,500,000 or less, more preferably 1,250,000 or less.

[0079] The specific poly(meth)acrylic acid can be at least one selected from homopolymers, copolymers, and crosslinks of homopolymers or copolymers.

[0080] The specific poly(meth)acrylic acid preferably has at least one unit selected from the units of compounds represented by general formula (I) and compounds represented by general formula (II).

[0081] [Chemical Formula 5]

[0082] In general formula (I), R 1 R represents a hydrogen atom or a methyl group. 2The group 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).

Chemical Formula 6

[0083] In the general formula (IA), R 3 R represents an alkylene group having 1 to 4 carbon atoms. 4 It represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer from 2 to 20.

[0084] [Chemical Formula 7]

[0085] In the general formula (IB), R 5 ~R 7 Each of the alkyl groups having 1 to 3 carbon atoms is represented independently, R 8 Indicates an alkylene group having 1 to 3 carbon atoms.

[0086] [Chemical Formula 8]

[0087] In general formula (II), R 11 R represents a hydrogen atom or a methyl group. 12 and R 13 Each can be independently represented by a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0088] R as general formula (I) 2 Alkyl groups having 1 to 20 carbon atoms, preferably having 1 to 10 carbon atoms.

[0089] R of general formula (IA) 3 The alkylene group is preferably ethylene, trimethylene, propylene, or tetramethylene, more preferably ethylene or propylene, and particularly preferably ethylene.

[0090] R as general formula (IA) 4 Preferably, hydrogen atoms or methyl groups are used.

[0091] In the general formula (IA), n is preferably an integer from 2 to 10, and more preferably an integer from 4 to 10.

[0092] In the above, R is represented by general formula (I). 2 Preferably, it contains hydrogen atoms, alkyl groups having 1 to 20 carbon atoms, or groups represented by general formula (IA).

[0093] R as general formula (II) 11 Hydrogen atoms are preferred.

[0094] R as general formula (II)12 Preferably, it contains hydrogen atoms or alkyl groups having 1 to 3 carbon atoms, and more preferably hydrogen atoms.

[0095] R as general formula (II) 13 Further preferred are hydrogen atoms or alkyl groups having 1 to 3 carbon atoms.

[0096] A specific poly(meth)acrylic acid may have only one unit based on a compound represented by general formula (I), or it may have two or more units. Furthermore, a specific poly(meth)acrylic acid may have only one unit based on a compound represented by general formula (II), or it may have two or more units.

[0097] A specific poly(meth)acrylic acid may be a homopolymer composed of units based on compounds represented by general formula (I) or units based on compounds represented by general formula (II), or a copolymer having units based on compounds represented by general formula (I) and units based on compounds represented by general formula (II), or a crosslinked product of these homopolymers or copolymers.

[0098] The crosslinking compound is preferably formed by crosslinking a (meth)acrylate compound having 2 to 4 (meth)acryloyl groups or a (meth)acrylamide compound having 2 to 4 (meth)acryloyl groups.

[0099] Certain poly(meth)acrylic acids can be neutralized, meaning that some or all of the carboxyl groups can form salts, preferably all of the carboxyl groups form salts.

[0100] From the viewpoint of effectively suppressing viscosity changes of the aqueous dispersion over time, 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 suppressing excessively high viscosity of the aqueous dispersion and operability, the above-mentioned content of the specific poly(meth)acrylic acid is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0101] (pH buffer)

[0102] The optimal pH range for a pH buffer is between 4 and 10. The optimal pH range refers to the range within which a pH buffer can exert its buffering function. Furthermore, the optimal pH range of the pH buffer disclosed herein only needs to be at least a portion of the range of 4 to 10. Preferably, the optimal pH range for the pH buffer is between 7 and 10.

[0103] pH buffers preferably comprise at least one selected from carbonic acid (about 5.4–7.4), phosphoric acid (about 5.4–7.4), boric acid (about 8.2–10.2), formic acid (about 2.6–4.6), oxalic acid (2.8–4.8), acetic acid (about 3.8–5.8), citric acid (about 3.8–5.8), isocitric acid (about 3.8–5.8), lactic acid (about 2.7–4.7), and ammonium salts of these acids, as well as sulfonic acids and amino acids. The values ​​in parentheses indicate the optimal pH range.

[0104] Examples of sulfonic acids and amino acids include 2-morpholinoethanesulfonic acid, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, N-(2-acetamide)-2-aminoethanesulfonic acid, 2-hydroxy-3-morpholinopropanesulfonic acid, 2-hydroxy-N-tris(hydroxymethyl)methyl-3-aminopropionic acid, N-tris(hydroxymethyl)methyl-3-aminopropionic acid, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, and 3-morpholinopropanesulfonic acid. Acids, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazine propanesulfonic 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.

[0105] The pH buffer is preferably an ammonium salt of a compound selected from 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 bicarbonate, or ammonium carbonate, and even more preferably ammonium bicarbonate, ammonium carbonate, or ammonium acetate.

[0106] From the viewpoint of effectively suppressing the viscosity change of the aqueous dispersion over time, the content of pH buffer 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. The above-mentioned content of pH buffer is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0107] (water)

[0108] The aqueous dispersion disclosed herein uses water as the dispersion medium. The water content can be appropriately adjusted considering factors such as the coating method and the thickness of the prepared molded product; for example, it is preferably greater than 40% by volume relative to the total volume of the aqueous dispersion, more preferably 50% by volume or more, and even more preferably 55% by volume or more. The water content relative to the total volume of the aqueous dispersion is preferably 90% by mass or less, more preferably 80% by mass or less. Furthermore, specifically, the water content in the aqueous dispersion is preferably 40 to 65% by mass. In this case, the aforementioned mechanism of action is more easily manifested.

[0109] The aqueous dispersion disclosed herein may further include a water-soluble dispersion medium other than water as the dispersion medium. Preferably, the water-soluble dispersion medium is a water-soluble compound that is polar at atmospheric pressure and liquid at 25°C, such as N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, and N-methyl-2-pyrrolidone.

[0110] The concentration of solids in the aqueous dispersion is preferably 20% by volume or more, more preferably 40% by volume or more, relative to the total volume of the aqueous dispersion. The concentration of solids is preferably 80% by volume or less. Here, solids refer to the total amount of substances forming solid components in the shaped article formed from the aqueous dispersion. Specifically, F particles, specific poly(meth)acrylic acid, and pH buffers are considered solids; if the aqueous dispersion contains other resins, those other resins are also considered solids.

[0111] (surfactant)

[0112] The aqueous dispersion may further contain a surfactant, preferably a surfactant without fluorine atoms. When the aqueous dispersion contains a surfactant, the surfactant is nonionic, and the hydrophobic portion of the surfactant preferably has an ethynyl group or a polysiloxane group, and the hydrophilic portion preferably has an alkylene group or an alcohol hydroxyl group.

[0113] That is, when the aqueous dispersion further contains a surfactant, a nonionic surfactant is preferred, and a polyoxyalkylene alkyl ether, an acetylene surfactant, or a silicone surfactant is more preferred. These surfactants preferably have an alcohol hydroxyl group. Furthermore, these surfactants can be used alone or in combination of two or more. From the viewpoint that polyoxyalkylene alkyl ethers stabilize the long-term dispersion of F particles and improve the viscosity and other liquid properties of the aqueous dispersion, and from the viewpoint that silicone surfactants improve the initial dispersion of F particles, it is preferable to use a combination of polyoxyalkylene alkyl ethers and silicone surfactants.

[0114] When the aqueous dispersion further contains a surfactant, its amount is preferably 1 to 15% by mass relative to the total mass of the aqueous dispersion. In this case, the affinity between the components is enhanced, and the dispersion stability of the aqueous dispersion is easily further improved.

[0115] Specific examples of organosilicon surfactants include "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", and "BYK-3456" (all of which are from BYK Chemicals Japan). Manufactured by Japan Co., Ltd., "KF-6011" and "KF-6043" (both manufactured by Shin-Etsu Chemical Co., Ltd.).

[0116] Specific examples of polyoxyalkylene alkyl ethers include "Tergitol TMN-100X" (manufactured by Dow Chemical Company), "Lutensol T08", "Lutensol XL70", "Lutensol XL80", "Lutensol XL90", "Lutensol XP80", "Lutensol M5" (all manufactured by BASF SE), "Newcol 1305", "Newcol 1308FA", "Newcol 1310" (all manufactured by Nippon Emulsifier Co., Ltd.), "LEOCOL TDN-90-80" and "LEOCOL SC-90" (both manufactured by Lion Specialty Chemicals Co., Ltd.). Specialty Chemicals Co., Ltd.).

[0117] The aqueous dispersion may further contain at least one nonionic water-soluble polymer selected from polyvinyl alcohol polymers, polyvinylpyrrolidone polymers, and polysaccharides. In this case, in addition to the dispersion stability of the aqueous dispersion, its rheological properties are improved, and the film-forming properties and other operability of the aqueous dispersion are more easily improved. As a result, it is easier to form a thick or shaped article of any shape from the aqueous dispersion. In particular, if the water-soluble polymer has a nonionic hydroxyl group, this tendency is likely to become significant.

[0118] The polyvinyl alcohol polymer may be a partially acetylated or partially acetalized polyvinyl alcohol.

[0119] Examples of polysaccharides include glycogen, amylopectin, dextrin, glucan, fructan, chitin, amylose, agarose, amylopectin, and cellulose. Examples of cellulose include methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0120] The nonionic water-soluble polymer is preferably a nonionic polysaccharide, more preferably a nonionic cellulose, and further preferably hydroxymethyl cellulose, hydroxyethyl cellulose, or hydroxypropyl cellulose.

[0121] Specific examples of 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.).

[0122] When the aqueous dispersion further contains a nonionic water-soluble polymer, the content of the nonionic water-soluble polymer relative to the total amount of the aqueous dispersion is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. Furthermore, this content is preferably less than 1% by mass. The ratio of the mass of the water-soluble polymer to the mass of F particles in the aqueous dispersion is preferably 0.001 or more, more preferably 0.01 or more. Furthermore, this ratio is preferably less than 0.1.

[0123] (Other ingredients)

[0124] Aqueous dispersions can be used in combination with particles of other fluoropolymers besides F polymers (hereinafter also referred to as "other F particles"). Examples of other fluoropolymers include hot-melt fluoropolymers other than F polymers and non-hot-melt fluoropolymers; from a formability viewpoint, hot-melt fluoropolymers other than F polymers are preferred. Hot-melt fluoropolymers other than F polymers are hot-melt fluoropolymers that do not contain TFE units.

[0125] When F particles are used in combination with other F particles, the proportion of the other F particles in the total amount of F particles and other F particles is preferably less than 50% by mass, more preferably less than 25% by mass. Furthermore, the above proportion is preferably more than 0.1% by mass, more preferably more than 1% by mass.

[0126] Aqueous dispersions may contain resins other than fluoropolymers. These other resins may be included in the aqueous dispersion in the form of powder particles, or they may be included by dissolving or dispersing in water.

[0127] Examples of other resins include liquid crystal aromatic polyesters and other polyester resins, imide resins, epoxy resins, maleimide resins, polyurethane resins, polyphenylene ether resins, polyphenylene ether resins, and polyphenylene sulfide resins. As other resins, aromatic polymers are preferred, and at least one aromatic imide polymer selected from aromatic polyimides, aromatic polyamic acids, aromatic polyamide imides, and precursors of aromatic polyamide imides is more preferred. In aqueous dispersions, the aromatic polymers are preferably contained in the form of a varnish dissolved in water.

[0128] Specific examples of aromatic imide polymers include the "UPIA-AT" series (manufactured by Ube Industries, Ltd.), the "Neopulim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Co., Ltd.), the "SPIXAREA (registered trademark)" series (manufactured by Somalon Corporation), the "Q-PILON (registered trademark)" series (manufactured by PI Technology Research Institute), 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 RESONAC Co., Ltd.).

[0129] 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. The above-mentioned content is preferably 15% by volume or less, more preferably 10% by volume or less.

[0130] Aqueous dispersions can further contain inorganic fillers. In this case, the electrical properties and low linear expansion of the molded articles formed from the aqueous dispersions tend to be excellent.

[0131] Inorganic fillers are preferably nitride fillers or inorganic oxide fillers, more preferably boron nitride fillers, beryllium oxide fillers (beryllium oxide fillers), silicate fillers (silica fillers, wollastonite fillers, talc fillers), or metal oxide fillers (cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.), and even more preferably silica fillers.

[0132] The inorganic filler preferably has at least a portion of its surface treated with a silane coupling agent (such as 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, or 3-isocyanatepropyltriethoxysilane).

[0133] The D50 of the inorganic filler is preferably less than 20 μm, more preferably less than 10 μm. The D50 is preferably greater than 0.01 μm, more preferably greater than 0.1 μm.

[0134] Inorganic fillers can be granular, needle-like (fibrous), or plate-like in shape. Specific shapes of inorganic fillers include spherical, scaly, layered, leaf-like, almond-shaped, columnar, cockscomb-shaped, equiaxed, leaf-like, mica-like, blocky, flat, wedge-shaped, rosette-shaped, mesh-like, and square columnar.

[0135] Inorganic fillers can be used alone or in combination of two or more. When the aqueous dispersion further contains inorganic fillers, the content of inorganic fillers relative to the total aqueous dispersion is preferably 1 to 50% by mass, more preferably 5 to 40% by mass.

[0136] Suitable examples of inorganic fillers include silica fillers (such as the "admafin" series manufactured by Admatech Co., Ltd.), zinc oxide surface-treated with esters such as propylene glycol didecanoate (such as the "FINEX" series manufactured by Sakai Chemical Industry Co., Ltd.), spherical fused silica fillers (such as the "SFP" series manufactured by Denka Co., Ltd.), and fillers made with polyols and... Inorganic zinc oxide fillers with coating treatment (such as the "TIPAQUE" series manufactured by Ishihara Sangyo Co., Ltd.), rutile titanium oxide fillers with alkylsilane surface treatment (such as the "JMT" series manufactured by Teika Co., Ltd.), hollow silica fillers (such as the "E-SPHERES" series manufactured by Pacific Cement Co., Ltd., the "SILINA X" series manufactured by Nippon Steel Mining Co., Ltd., and Emerson Cummins Co., Ltd.) アンド Examples of fillers include: Eccospheres series (manufactured by Caming Co., Ltd.), talc fillers (SG series (manufactured by Nippon Talc Co., Ltd.), block talc fillers (BST series (manufactured by Nippon Talc Co., Ltd.), boron nitride fillers (UHP series (manufactured by Showa Denko Co., Ltd.), and Denka Boron Nitride series (GP, HGP grade) (manufactured by Denka Co., Ltd.).

[0137] From the perspective of further improving the miscibility of F polymer with inorganic fillers, aqueous dispersions can further include silane coupling agents.

[0138] As silane coupling agents, the same types as those that can be used for surface treatment of inorganic fillers can be listed, and their preferred range is also the same.

[0139] When the aqueous dispersion contains a silane coupling agent, the content of the silane coupling agent in the aqueous dispersion (except for those used for surface treatment of inorganic fillers) is preferably 1 to 10% of the total volume of the aqueous dispersion.

[0140] Aqueous dispersions may further contain additives such as thixotropic agents, viscosity modifiers, defoamers, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive materials, mold release agents, surface treatment agents, flame retardants, conductive fillers, and preservatives.

[0141] (Physical properties of aqueous dispersions)

[0142] The pH value 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 pH buffer mentioned above, other alkaline compounds such as ammonia and amines may be used in combination.

[0143] The viscosity of the aqueous dispersion at 25°C is preferably below 10,000 mPa·s, more preferably below 3,000 mPa·s. The viscosity of the aqueous dispersion at 25°C is preferably above 500 mPa·s, more preferably above 600 mPa·s.

[0144] After storing the aqueous dispersion in a container at 25°C for one month, the viscosity change rate 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, further preferably 85% or more, and particularly preferably 90% or more.

[0145] Viscosity retention rate = Viscosity after storage (mPa·s) / Viscosity before storage (mPa·s) × 100

[0146] The thixotropic ratio of the aqueous dispersion is preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less. Furthermore, the thixotropic ratio of the aqueous dispersion is preferably 1 or more, more preferably 2 or more. If the thixotropic ratio of the aqueous dispersion is within the above range, it is easier to suppress the sedimentation of F particles.

[0147] <Method for manufacturing aqueous dispersions>

[0148] The aqueous dispersion disclosed herein can be obtained by mixing F particles, specific poly(meth)acrylic acid, pH buffer, and water, as well as other additives such as resins, surfactants, and silane coupling agents as needed. The mixing order is not particularly limited, and the mixing method can be either simultaneous mixing or multiple mixing steps.

[0149] Examples of mixing devices for obtaining the aqueous dispersions disclosed herein include: agitators with blades such as Henschel mixers, pressure kneaders, Banbury mixers, and planetary mixers; pulverizing devices with media such as ball mills, pulverizers, basket mills, sand mills, sand grinders, DYNO mills, DISPERMAT dispersers, SC mills, Spike mills, and stirred mills; and dispersing devices with other mechanisms such as microfluidizers, nano-dispersers, Ultimaizer dispersers, ultrasonic homogenizers, dissolvers, dispersers, high-speed impeller dispersers, thin-film gyratory high-speed mixers, self-rotating and revolution-rotating mixers, and V-type mixers.

[0150] <Applications of Aqueous Dispersions>

[0151] The uses of the aqueous dispersions disclosed herein are not particularly limited; for example, they can be used in the manufacture of molded articles. In particular, the aqueous dispersions of this disclosure are suitable for applications where it is desirable to advantageously exhibit the properties of the F polymer contained in the aqueous dispersion.

[0152] Aqueous dispersions can be used as materials that impart insulation, heat resistance, corrosion resistance, chemical resistance, water resistance, and impact resistance.

[0153] Specifically, aqueous dispersions can be used in printed wiring boards, thermal interface materials, power module substrates, coils used in power devices such as motors, vehicle engines, heat exchangers, tubing, syringes, ampoules, medical wiring, 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 switching elements, electrode adhesives, electrode diaphragms, electrodes (positive and negative electrodes), etc.

[0154] In addition, aqueous dispersions can also be used as adhesives for bonding components. Specifically, aqueous dispersions can be used for: bonding ceramic components, bonding metal components, bonding IC chips or electronic components such as resistors and capacitors on the substrate of semiconductor elements or module components, bonding circuit boards to heat sinks, and bonding LED chips to substrates, etc.

[0155] <Laminated bodies and methods for manufacturing laminated bodies>

[0156] The method for manufacturing the laminate disclosed herein involves applying the aqueous dispersion of the present invention onto a substrate, heating to remove the water, and further heating to melt and sinter the F particles.

[0157] Examples of substrates include: metal substrates (metal foils made of copper, nickel, aluminum, titanium, and alloys of these metals), heat-resistant resin films (heat-resistant resin films made of polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamide-imide, liquid crystal polyester, tetrafluoroethylene polymers, etc.), prepreg substrates (precursors to fiber-reinforced resin substrates), ceramic substrates (ceramic substrates made of silicon carbide, aluminum nitride, silicon nitride, etc.), and glass substrates.

[0158] The shapes of substrates can include planar, curved, and uneven. Furthermore, the properties of the substrate can be any of the following: foil, plate, film, and fibrous (woven fabric, nonwoven fabric, etc.).

[0159] The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm.

[0160] The substrate surface can be surface-treated with a silane coupling agent or subjected to plasma treatment. Examples of such silane coupling agents include those used for surface treatment of inorganic fillers.

[0161] The peel strength between the fluoropolymer 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.

[0162] Methods for applying aqueous dispersions include coating, droplet spraying, and dipping, with roller coating, blade coating, rod coating, mold coating, or spraying being preferred.

[0163] Heating for water removal is preferably performed at 100–200°C for 0.1–30 minutes. During this heating, water does not need to be completely removed; it is sufficient to remove enough water to maintain the self-supporting membrane structure of the layer formed by the accumulation of F particles and composite particles. Furthermore, air can be blown during heating to promote water removal through air drying.

[0164] The heating during the firing of polymer F is preferably carried out at a temperature above the firing temperature of polymer F, and more preferably at 360 to 400°C for 0.1 to 30 minutes.

[0165] Examples of heating devices used in various heating processes include ovens and ventilated drying furnaces. The heat source in these devices can be a contact heat source (hot air, heating plate, etc.) or a non-contact heat source (infrared rays, etc.).

[0166] Furthermore, each heating can be performed under normal pressure or under reduced pressure.

[0167] In addition, the atmosphere in each heating process can be any of the following: air atmosphere or inert gas atmosphere (helium, neon, argon, nitrogen, etc.).

[0168] The fluoropolymer layer is formed through a process of applying an aqueous dispersion and heating. These processes can be performed once or repeated more than once. For example, an aqueous dispersion can be applied to the surface of a substrate and heated to form a fluoropolymer layer, followed by applying an aqueous dispersion to the surface of the fluoropolymer layer and heating to form a second fluoropolymer layer. Alternatively, an aqueous dispersion can be applied to the surface of the substrate and heated to remove water, followed by heating to form a second fluoropolymer layer.

[0169] The aqueous dispersion can be applied to only one surface of the substrate or to both surfaces of the substrate. The former results in a laminate having a substrate layer and a fluoropolymer layer on a single surface of the substrate layer, while the latter results in a laminate having a substrate layer and fluoropolymer layers on both surfaces of the substrate layer.

[0170] The thickness of the fluoropolymer layer can be appropriately selected according to the application; for example, it can be above 25 μm, above 30 μm, or above 40 μm. Furthermore, the thickness of the fluoropolymer layer can be below 200 μm.

[0171] Suitable examples of laminates include metal-coated laminates having a metal foil and a fluoropolymer layer on at least one surface of the metal foil, and multilayer films having a polyimide film and fluoropolymer layers on both surfaces of the polyimide film.

[0172] Laminated structures formed from aqueous dispersions can be used as antenna components, printed circuit boards, aircraft components, automotive components, sports equipment, food industry supplies, heat dissipation components, etc.

[0173] Specifically, it can be used as a material for electrical wire sheathing (aircraft wires, etc.), enameled wire sheathing material for motors in electric vehicles, electrical insulating tape, insulating tape for oil drilling, oil pipelines, hydrogen tanks, materials for printed circuit boards, separation membranes (precision filtration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode adhesives (for lithium secondary batteries, fuel cells, etc.), photocopier rollers, covers for furniture, automotive dashboards, and household appliances, and sliding components (load bearings, yaw bearings, sliding shafts, valves, bearings). Bushings, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, conveyor belts, food conveyor belts, 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, chisels, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, plastic molds, toilets, container covering materials, heat dissipation substrates for power devices, heat dissipation components for wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOSFETs, CPUs, heat sinks, metal heat sinks, blades for windmills or wind power generation equipment or aircraft, casings for computers or monitors, electronic device materials, automotive interior and exterior trim, sealing materials for processing machines or vacuum furnaces that perform heat treatment under low oxygen conditions, plasma processing equipment, heat dissipation components in processing units of sputtering or various dry etching equipment, electromagnetic wave shielding, etc.

[0174] The laminate formed from the aqueous dispersion of this disclosure can be used as electronic substrate materials such as flexible printed circuit boards and rigid printed circuit boards, protective films or heat dissipation substrates, especially heat dissipation substrates for automobiles.

[0175] Example

[0176] The following examples illustrate the implementation of this disclosure, but the implementation of this disclosure is not limited to these examples.

[0177] Prepare the following F particles.

[0178] F-particle 1: Each 1×10 of TFE units, NAH units, and PPVE units 6 Particles of tetrafluoroethylene polymers (melting temperature: 300℃) with 1000 carbon atoms in the main chain and containing carbonyl groups (D50: 2.1μm, specific surface area: 8m²) 2 / g)

[0179] F-particle 2: Each 1×10 of TFE and PPVE units 6 Particles of tetrafluoroethylene polymers (melting temperature: 300℃) with 250 carbon atoms in the main chain and carbonyl groups (D50: 1.6μm, specific surface area: 16m²) 2 / g)

[0180] F-particle 3: Each 1×10 of TFE and PPVE units 6 Particles of tetrafluoroethylene polymers (melting temperature: 300℃) with 250 carbonyl groups in the main chain (D50: 3.6μm, specific surface area: 6m²) 2 / g)

[0181] Prepare the following polyacrylic acid.

[0182] PAA1: A copolymer of acrylic acid and 2-hydroxyethyl acrylate in a 1:1 molar ratio, crosslinked with polyethylene glycol diacrylate, containing a weight-average molecular weight (Mw) of 1 million for polyacrylic acid.

[0183] PAA2: A copolymer of acrylic acid and 2-hydroxyethyl acrylate in a 1:1 molar ratio, containing polyacrylic acid with a weight-average molecular weight of 250,000 that is not crosslinked with polyethylene glycol diacrylate.

[0184] PAA3: A copolymer of acrylic acid and 2-hydroxyethyl acrylate in a 1:1 molar ratio, containing polyacrylic acid with a weight-average molecular weight (Mw) of 150,000 that is not crosslinked with polyethylene glycol diacrylate.

[0185] (Example 1)

[0186] An aqueous dispersion 1 containing 40% by mass F particles 1, 0.1% by mass PAA1 and ammonium bicarbonate (optimal pH range: 9.0–10.0) and adjusted to pH 9 with ammonia was prepared by shearing and stirring.

[0187] (Example 2)

[0188] The same method as in Example 1 was used, but PAA2 with a Mw of 250,000 was used instead of PAA1 to prepare aqueous dispersion 2.

[0189] (Example 3)

[0190] The same method as in Example 1 was used, but PAA3 with a Mw of 150,000 was used instead of PAA1 to prepare aqueous dispersion 3.

[0191] (Example 4)

[0192] The same method as in Example 1 was used, but ammonia was used instead of ammonium bicarbonate and ammonium ammonia were used to prepare aqueous dispersion 4.

[0193] (Example 5)

[0194] The same method as in Example 1 was used, but without adding ammonium bicarbonate and ammonia, to prepare aqueous dispersion 5.

[0195] <Evaluation (Part 1)>

[0196] The pH values ​​of the obtained aqueous dispersions 1–5 were measured.

[0197] In addition, the obtained aqueous dispersions 1–5 were stored in containers at 25°C for one month, and the viscosity before and after storage was measured. The results are shown in Table 1.

[0198] [Table 1]

[0199] <Evaluation (Part 2)>

[0200] Except for changing the types and contents of F particles as shown in Table 2 below, aqueous dispersions 6-12 were prepared in the same manner as in Example 1. Aqueous dispersions 1, 6-12 were stored at 25°C for one month, and the viscosity before and after storage was measured. A viscosity change rate (viscosity after storage / viscosity before storage × 100) of 90% or more was denoted as "A", 80% or more but less than 90% as "B", and 50% or more but less than 80% as "C". The results are summarized in Table 2. Furthermore, the viscosity of the aqueous dispersions before storage was 500-2000 mPa·s.

[0201] [Table 2]

[0202] The disclosure of Japanese Patent Application No. 2023-131640 is incorporated herein by reference in its entirety. All documents, patent applications and technical specifications described herein are incorporated herein by reference to the extent that each document, patent application and technical specification is specifically and separately described therein.

Claims

1. An aqueous dispersion comprising particles of a thermoplastic tetrafluoroethylene polymer, poly(meth)acrylic acid with a weight-average molecular weight of 200,000 or more, a pH buffer with an optimal pH range of 4 to 10, and water, wherein the pH value is 4 to 10.

2. The aqueous dispersion as described in claim 1, wherein, Its viscosity at 25°C is above 500 mPa·s.

3. The aqueous dispersion as described in claim 1 or 2, wherein, The hot-melt tetrafluoroethylene polymer comprises at least one of tetrafluoroethylene-based units, perfluoro(alkyl vinyl ether)-based units, and hexafluoropropylene-based units.

4. The aqueous dispersion as described in claim 1 or 2, wherein, The hot-melt tetrafluoroethylene polymer has a carbonyl group.

5. The aqueous dispersion as described in claim 1 or 2, wherein, The hot-melt tetrafluoroethylene polymer per 1×10 6 Each main chain has 10 to 5000 carbon atoms containing carbonyl groups.

6. The aqueous dispersion as described in claim 1 or 2, wherein, The average particle size of the particles containing the hot-melt tetrafluoroethylene polymer is less than 10 μm.

7. The aqueous dispersion as described in claim 1 or 2, wherein, The particles containing thermoplastic tetrafluoroethylene polymers have a specific surface area greater than 6 m². 2 / g.

8. The aqueous dispersion as described in claim 1 or 2, wherein, The content of particles containing hot-melt tetrafluoroethylene polymers is less than 60% by mass.

9. The aqueous dispersion as described in claim 1 or 2, wherein, The poly(meth)acrylic acid has a weight-average molecular weight of 500,000 to 1,500,000.

10. The aqueous dispersion as described in claim 1 or 2, wherein, The poly(meth)acrylic acid has at least one unit selected from units based on compounds represented by general formula (I) and units based on compounds represented by general formula (II): 【Chemical Formula 1】 In general formula (I), R 1 R represents a hydrogen atom or a methyl group. 2 The group 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). 【Chemical Formula 2】 In the general formula (IA), R 3 R represents an alkylene group having 1 to 4 carbon atoms. 4 This indicates a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, where n represents an integer from 2 to 20. 【Chemical Formula 3】 In the general formula (IB), R 5 ~R 7 Each of the alkyl groups having 1 to 3 carbon atoms is represented independently, R 8 Indicates alkylene groups having 1 to 3 carbon atoms. [Chemical Formula 4] In general formula (II), R 11 R represents a hydrogen atom or a methyl group. 12 and R 13 Each can be independently represented by a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

11. The aqueous dispersion as described in claim 1 or 2, wherein, The pH buffer comprises at least one selected from carbonic acid, phosphoric acid, boric acid, formic acid, oxalic acid, acetic acid, citric acid, isocitrate, lactic acid, and ammonium salts of these acids, as well as sulfonic acids and amino acids.

12. The aqueous dispersion as described in claim 1 or 2, wherein, Its viscosity at 25°C is below 10000 mPa·s.

13. The aqueous dispersion of claim 1 or 2, further comprising a surfactant that does not have fluorine atoms.

14. A method for manufacturing a laminate, comprising applying the aqueous dispersion of claim 1 or 2 onto a substrate, heating to remove the water, and further heating to melt and sinter the particles comprising a thermoplastic tetrafluoroethylene polymer.

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