Aqueous dispersion and method for producing same

Abstract

[Problem] To provide an aqueous dispersion which contains particles of a tetrafluoroethylene polymer and exhibits excellent dispersion stability, while being capable of forming a molded body that is excellent in terms of electrical characteristics such as low dielectric loss tangent and low transmission loss, flexibility such as bending resistance, UV absorption, and bondability / adhesion to resin films such as polyimide films. [Solution] An aqueous dispersion which contains particles of a tetrafluoroethylene polymer, an aromatic imide resin that has an acid value of from 20 mg / KOH to 100 mg / KOH, and water, and which has a pH of from 5 to 10.

Description

[Technical Field]

[0001] The present invention relates to an aqueous dispersion containing particles of a tetrafluoroethylene-based polymer and a specific aromatic imide-based resin, and to a method for producing such an aqueous dispersion. [Background technology]

[0002] Tetrafluoroethylene-based polymers such as polytetrafluoroethylene (PTFE) have excellent physical properties such as electrical properties, water and oil repellency, chemical resistance, and heat resistance, and are used in a variety of industrial applications (Patent Document 1). Dispersions containing tetrafluoroethylene-based polymer particles are known as coating agents used to impart the above physical properties to the surface of a substrate. In particular, in recent years, dispersions containing particles of tetrafluoroethylene-based polymers have been attracting attention as materials with excellent electrical properties such as low dielectric constant and low dielectric loss tangent, which are used to form dielectric layers for printed circuit boards that are compatible with high-frequency bands.

[0003] From the viewpoint of ease of handling, it is preferable that the dispersion is aqueous. Patent Document 2 discloses a laminate formed by applying an aqueous dispersion of a fluororesin to one or both sides of a resin film and heating the applied film. Patent Document 3 discloses a composition containing an aqueous polyimide precursor, a fluororesin, and water, which are uniformly mixed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-218484 [Patent Document 2] Japanese Patent Application Publication No. 09-157418 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-20488 Summary of the Invention [Problem to be solved by the invention]

[0005] However, aqueous dispersions of tetrafluoroethylene-based polymers generally have poorer dispersion states than non-aqueous dispersions. Therefore, during coating and baking on a substrate, the packing of tetrafluoroethylene-based polymer particles becomes loose, which can easily cause problems with the density of the formed polymer layer. Specifically, when the polymer layer is formed on a substrate such as a resin film using a continuous production process such as roll-to-roll, cracks and pinholes are likely to occur in the polymer layer. The inventors' investigations have revealed that these tendencies become more pronounced when the aqueous dispersions described in the prior art documents are used.

[0006] As a result of extensive research, the present inventors have found that a dispersion containing tetrafluoroethylene polymer particles, a specific aromatic imide resin, and water, and having a pH within a specific range, has excellent dispersion stability. Furthermore, they have found that molded articles obtained from such dispersions are dense and have excellent properties such as a low dielectric loss tangent and a low coefficient of linear expansion, as well as improved flexibility such as flex resistance, UV absorption, and adhesion to plastic films such as polyimide films. An object of the present invention is to provide an aqueous dispersion which has excellent dispersion stability and which provides a molded product having excellent flexibility such as flex resistance, UV absorption, and adhesiveness and adhesion to resin films such as polyimide films. [Means for solving the problem]

[0007] The present invention has the following aspects. <1> An aqueous dispersion having a pH of 5-10, comprising particles of a tetrafluoroethylene polymer, an aromatic imide resin having an acid value of 20-100 mg / KOH, and water. <2> The tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer having an oxygen-containing polar group containing a unit based on perfluoro(alkyl vinyl ether). <1> Aqueous dispersion of. <3> the tetrafluoroethylene-based polymer particles include particles of a non-thermofusible tetrafluoroethylene-based polymer and particles of a thermofusible tetrafluoroethylene-based polymer; <1> or <2> Aqueous dispersion of. <4> the aromatic imide resin is a precursor of a water-soluble aromatic polyamideimide or a precursor of a water-soluble aromatic polyimide; <1> ~ <3> an aqueous dispersion of either <5> Further, the composition contains an inorganic filler. <1> ~ <4> an aqueous dispersion of either <6> Further, a nonionic surfactant is contained. <1> ~ <5> an aqueous dispersion of either <7> Further, the composition contains at least one nonionic polymer selected from the group consisting of polyvinyl alcohol-based polymers, polyvinylpyrrolidone-based polymers, and polysaccharides. <1> ~ <6> an aqueous dispersion of either <8> containing amines or ammonia, <1> ~ <7> an aqueous dispersion of either <9> the ratio of the mass of the aromatic imide resin to the mass of the tetrafluoroethylene polymer particles is in the range of 0.001 to 0.1; <1> ~ <8> an aqueous dispersion of either <10> the total content of the particles and the aromatic imide resin in the aqueous dispersion is 20% by mass or more with respect to the total mass of the aqueous dispersion; <1> ~ <9> an aqueous dispersion of either <11> Viscosity is 50 to 3000 mPa·s. <1> ~ <10> an aqueous dispersion of either <12> It is used to form a polymer layer containing a tetrafluoroethylene-based polymer by applying it to at least one surface of a resin film and heating it. <1> ~ <11> an aqueous dispersion of either <13> The resin constituting the resin film is a polyimide resin. <1> ~ <12> an aqueous dispersion of either <14> kneading a composition containing the tetrafluoroethylene-based polymer particles, the aromatic imide-based resin, and water to obtain a kneaded mixture, and mixing the kneaded mixture with water to obtain the aqueous dispersion. <1> ~ <13> A method for producing any one of the aqueous dispersions described above. <15> <1> ~ <13> a resin film having a base layer made of the resin film and a polymer layer containing a tetrafluoroethylene-based polymer, the base layer having the polymer layer on both sides of the base layer being formed by applying any one of the aqueous dispersions described above to both surfaces of the resin film and heating the applied aqueous dispersion. [Effects of the Invention]

[0008] According to the present invention, there are provided an aqueous dispersion of a tetrafluoroethylene-based polymer having excellent dispersion stability, and a method for producing such an aqueous dispersion. The aqueous dispersion of the present invention can be used to form a molded article having excellent physical properties, such as low dielectric tangent and low transmission loss, as well as excellent flexibility, such as flex resistance, UV absorption, and adhesiveness and adhesion to resin films, such as polyimide films. Therefore, the aqueous dispersion of the present invention is useful, for example, as a constituent material for printed circuit boards. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following terms have the following meanings: "Average particle size (D50)" is the volume-based cumulative 50% diameter of the target object (particles and fillers) determined by laser diffraction / scattering. In other words, particle size distribution is measured by laser diffraction / scattering, and a cumulative curve is calculated with the total volume of the target object (particles and fillers) group as 100%, and the particle size is the point on that cumulative curve where the cumulative volume is 50%. The D50 of the target material (particles and fillers) is determined by dispersing the target material (particles and fillers) in water and analyzing it by the laser diffraction / scattering method using a laser diffraction / scattering particle size distribution analyzer (LA-920 measuring instrument, manufactured by Horiba, Ltd.). The "melting temperature" is the temperature corresponding to the maximum value of the melting peak of a polymer as measured by differential scanning calorimetry (DSC). The "viscosity" is determined by measuring the object (dispersion liquid and kneaded product) 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. The "thixotropy ratio" is a value calculated by dividing the viscosity η1 of the object (dispersion liquid and kneaded material) measured at a rotation speed of 30 rpm by the viscosity η2 measured at a rotation speed of 60 rpm. Each viscosity measurement is repeated three times, and the average value of the three measurements is used. The "HLB value of polyoxyalkylene-modified polydimethylsiloxane" is a value calculated using the Griffin equation, and is found by multiplying the molecular weight of the polyoxyalkylene portion in the molecule by the molecular weight of the organopolysiloxane by 20. The "static surface tension" is determined by the Wilhelmy method using an automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) and a 0.1% by mass aqueous solution of polyoxyalkylene-modified polydimethylsiloxane. "Dynamic surface tension" refers to the dynamic surface tension of a 0.1% by mass aqueous solution of polyoxyalkylene-modified polydimethylsiloxane at 25°C with a bubble generation frequency of 6 Hz according to the maximum bubble pressure method, and is the value measured by the maximum bubble pressure method at 25°C by immersing the sensor of a dynamic surface tensiometer Theta T60 manufactured by Eiko Instruments Co., Ltd. in the aqueous solution containing 0.1% by mass of polyoxyalkylene-modified polydimethylsiloxane. The measurement is performed with the bubble generation frequency of the aqueous solution set to 6 Hz. The term "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 processing the polymer. Hereinafter, a unit based on monomer a will also be referred to simply as a "monomer a unit."

[0010] The aqueous dispersion of the present invention (hereinafter also referred to as "the present dispersion") contains particles (hereinafter also referred to as "F particles") of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer"), an aromatic imide-based resin (hereinafter also referred to as "imide-based resin P") having an acid value of 20 to 100 mg / KOH, and water, and has a pH of 5 to 10.

[0011] This dispersion has excellent dispersion stability. In addition, the molded product (baked product) formed from this dispersion has excellent physical properties based on tetrafluoroethylene polymers, such as electrical properties, and has excellent surface smoothness, as well as flexibility such as bending resistance, UV absorption, and excellent adhesiveness and adhesion to resin films such as polyimide films. The reason why the dispersion stability of the present dispersion is improved is not entirely clear, but is presumed to be, for example, as follows. The imide-based resin P in the present invention has a specific acid value, which facilitates interaction with F particles and water. It not only acts as a dispersant for the F particles in the dispersion, but also as a viscosity modifier for the dispersion, presumably improving the dispersion stability of the dispersion. Furthermore, the specific pH range of the dispersion not only enhances this effect, but also enhances the reactivity of the imide-based resin P when the dispersion is heated to form a molded product. This enhances the interaction between the imide-based resin P and the F polymer and substrate, presumably improving the flexibility and adhesiveness / cohesion (binding ability) of the resulting molded product. As a result, the dispersion exhibits excellent dispersion stability, and it is believed that molded products with excellent electrical properties, flex resistance, UV absorption, etc. can be formed from the dispersion using a continuous production process such as roll-to-roll.

[0012] The F polymer in this dispersion is a polymer containing units (TFE units) based on tetrafluoroethylene (TFE). One type of F polymer may be used, or two or more types may be used. The F polymer may be either heat-fusible or non-heat-fusible, but it is preferable that at least one type of F polymer is heat-fusible. In this case, molded articles formed from this dispersion tend to have excellent flexibility and excellent adhesiveness and adhesion to resin films such as polyimide films. Note that heat-fusible refers to a polymer with melt flowability that exhibits a melt flow rate of 0.1 to 1,000 g / 10 min at a temperature 20°C or more higher than the melting temperature of the polymer under a load of 49 N. When the F polymer is heat-meltable, the melting temperature is preferably 200 to 320° C., more preferably 260 to 320° C. In such a case, the molded article formed from the dispersion tends to have excellent heat resistance.

[0013] The fluorine atom content in the F polymer is preferably 70% by mass or more, more preferably 70 to 76% by mass. Due to the above-mentioned mechanism of action, the present dispersion particularly tends to improve the water dispersibility of particles of such an F polymer with a high fluorine atom content. The glass transition point of the F polymer is preferably from 75 to 125°C, more preferably from 80 to 100°C.

[0014] Examples of F polymers include polytetrafluoroethylene (PTFE), polymers containing TFE units and units based on ethylene (ETFE), polymers containing TFE units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units) (PFA), and polymers containing TFE units and units based on hexafluoropropene (HFP) (FEP). ETFE, PFA, and FEP may each further contain other units. Preferred PAVEs are CF₂=CFOCF₃, CF₂=CFOCF₂CF₃, and CF₂=CFOCF₂CF₂CF₃ (PPVE), with PPVE being more preferred. The F polymer is preferably PFA or FEP, more preferably PFA.

[0015] At least one of the F polymers preferably has an oxygen-containing polar group. In this case, the affinity of the F polymer with the imide-based resin P and water is improved, and the dispersion is likely to have excellent dispersion stability. Furthermore, in this case, it is believed that when the dispersion is baked, the F polymer reacts with the imide-based resin P to form crosslinks. As a result, the baked product (polymer layer, etc.) obtained from the dispersion is believed to have even better physical properties, such as electrical properties, surface smoothness, and adhesiveness / adhesion to resin films such as polyimide films. The oxygen-containing polar group may be contained in a unit in the F polymer or in a terminal group of the main chain of the F polymer. Examples of the latter include an F polymer having an oxygen-containing polar group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer having an oxygen-containing polar group obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment. The oxygen-containing polar group is preferably a hydroxyl group-containing group, a carbonyl group-containing group, or a phosphono group-containing group. From the viewpoint of the dispersion stability of the present dispersion, a hydroxyl group-containing group or a carbonyl group-containing group is more preferred, and a carbonyl group-containing group is even more preferred.

[0016] The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, and more preferably -CF2CH2OH, -C(CF3)2OH, or a 1,2-glycol group (-CH(OH)CH2OH). The carbonyl group-containing group is a group containing a carbonyl group (>C(O)), and is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) or a carbonate group (-OC(O)O-), more preferably an acid anhydride residue. 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 The number per unit is preferably 10 to 5000, more preferably 100 to 3000, and further preferably 800 to 1500. The number of carbonyl group-containing groups in the F polymer can be quantified by the composition of the polymer or the method described in WO 2020 / 145133.

[0017] The F polymer is preferably a polymer having an oxygen-containing polar group containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on a monomer having an oxygen-containing polar group, and even more preferably a polymer containing these units in the following amounts, in that order, relative to all units. The monomer having an oxygen-containing polar group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"). Specific examples of such polymers include the polymers described in WO 2018 / 16644. These F polymers not only have excellent dispersion stability, but also tend to be more densely and uniformly distributed in molded products (polymer layers, etc.) obtained from the dispersion. Furthermore, they tend to form microspherulites in the molded products, which tends to enhance adhesion with other components. As a result, molded products with excellent physical properties, such as electrical properties, are more likely to be obtained.

[0018] Non-thermofusible F polymers include non-thermofusible PTFE. The number average molecular weight of the non-thermofusible PTFE is preferably 1,000,000 to 100,000,000. The number average molecular weight of the non-thermofusible PTFE is a value calculated based on the following formula (1). Mn = 2.1 × 10 10 ×ΔHc -5.16 ··· (1) In formula (1), Mn represents the number average molecular weight of the non-thermofusible PTFE, and ΔHc represents the heat of crystallization (cal / g) of the non-thermofusible PTFE measured by differential scanning calorimetry. When the number average molecular weight is within this range, the F polymer is less likely to fibrillate, and the dispersion tends to have excellent dispersion stability.

[0019] In the present dispersion, the D50 of the F particles is preferably 0.1 to 25 μm. The D50 of the F particles is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The D50 of the F particles is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. With a D50 in this range, the F particles tend to have good fluidity and dispersibility.

[0020] From the viewpoint of dispersion stability of this dispersion, the bulk density of F particles is set to 0.15 g / m 2 More than 0.20 g / m is preferable. 2The bulk density of the F particles is preferably 0.50 g / m or more. 2 Less than 0.35 g / m 2 The following is more preferred: The specific surface area of ​​F particles is 1 to 8 m 2 / g is preferred, and 1 to 3m 2 / g is more preferred.

[0021] One type of F particles may be used, or two or more types may be used. When two types of F particles are used, it is preferable to include particles of a non-thermofusible F polymer and particles of a heat-fusible F polymer, and it is more preferable to include particles of a non-thermofusible PTFE (preferably the above-mentioned PTFE having a number average molecular weight of 1,000,000 to 100,000,000) and particles of an F polymer having a melting temperature of 200 to 320°C (preferably the above-mentioned polymer having an oxygen-containing polar group containing TFE units and PAVE units).

[0022] In this case, the ratio of the mass content of the two particles may be such that the mass content of the former particles is greater than the mass content of the latter particles, or may be such that the mass content of the former particles is less than the mass content of the latter particles. It is more preferable that the mass content of the former particles is greater than the mass content of the latter particles. In this case, the proportion of the latter particles in the total of the former particles and the latter particles is preferably 25% by mass or less, more preferably 15% by mass or less, and in this case, the proportion is preferably 0.1% by mass or more, more preferably 1% by mass or more. Such a dispersion of the present invention not only tends to have excellent dispersion stability, ease of handling, and long-term storage stability, but also tends to form adhesive molded articles having excellent physical properties based on PTFE.

[0023] Furthermore, it is preferable that the content by mass of the former particles is less than the content by mass of the latter particles, since it is easy to form a molded product having excellent adhesiveness and surface smoothness. In this case, the proportion of the former particles in the total of the former and latter particles is preferably less than 50% by mass, more preferably 25% by mass or less, and is preferably 5% by mass or more, more preferably 10% by mass or more.

[0024] When particles of a non-thermofusible F polymer and particles of an F polymer having a melting temperature of 200 to 320°C are used, a preferred embodiment is one in which the D50 of the non-thermofusible PTFE particles is 0.1 to 1 μm and the D50 of the F polymer particles having a melting temperature of 200 to 320°C is 0.1 to 1 μm, and a preferred embodiment is one in which the D50 of the non-thermofusible PTFE particles is 0.1 to 1 μm and the D50 of the F polymer particles having a melting temperature of 200 to 320°C is 1 to 4 μm.

[0025] The F particles may contain resins other than the F polymer or inorganic fillers, but preferably contain the F polymer as the main component. The content of the F polymer in the F particles is preferably 80% by mass or more, more preferably 100% by mass. Examples of the resin include heat-resistant resins such as aromatic polyester, polyamideimide, (thermoplastic) polyimide, polyphenylene ether, polyphenylene oxide, and maleimide. Examples of the inorganic filler include silicon oxide (silica), metal oxides (beryllium oxide, cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide, titanium oxide, etc.), boron nitride, and magnesium metasilicate (steatite). At least a portion of the surface of the inorganic filler may be surface-treated. F particles containing a resin other than an F polymer or an inorganic filler may have a core-shell structure with an F polymer as the core and a resin other than an F polymer or an inorganic filler as the shell, or may have a core-shell structure with an F polymer as the shell and a resin other than an F polymer or an inorganic filler as the core. Such F particles can be obtained, for example, by coalescence (collision, aggregation, etc.) of particles of an F polymer with particles of a resin other than an F polymer or an inorganic filler.

[0026] The imide-based resin P constituting this dispersion not only improves the dispersion stability of this dispersion but also imparts flexibility, such as flex resistance, and UV absorption properties to molded articles obtained from this dispersion. Furthermore, when this dispersion is applied to the surface of a resin film such as a polyimide film to form a polymer layer containing F polymer, this resin imparts properties such as adhesiveness and adhesion to the resin film to the polymer layer.

[0027] Examples of the imide-based resin P include aromatic polyimides, aromatic polyimide precursors (polyamic acids or salts thereof), aromatic polyamideimides, aromatic polyamideimide precursors, modified aromatic polyimides having polar functional groups such as carboxylic acid groups, modified aromatic polyimide precursors, modified aromatic polyamideimides, modified aromatic polyamideimide precursors, aromatic polyetherimides, and aromatic polyetherimide precursors. Among these, aromatic polyimides or precursors thereof (polyamic acids or salts thereof), and aromatic polyamideimides or precursors thereof are preferred, with water-soluble aromatic polyimide precursors and water-soluble aromatic polyamideimide precursors being more preferred, and water-soluble aromatic polyamideimide precursors being even more preferred.

[0028] Examples of water-soluble aromatic polyimide precursors include polyamic acids obtained by polymerizing tetracarboxylic dianhydrides and diamines in a solvent, and polyamic acid salts obtained by reacting such polyamic acids with aqueous ammonia or organic amines. An aqueous solution of polyamic acid can be prepared by dissolving the polyamic acid salt in water. Examples of tetracarboxylic dianhydrides include pyromellitic anhydride and biphenyltetracarboxylic anhydride. Examples of diamines include N,N'-diaminodiphenyl ether and p-diaminobenzene. Examples of solvents include N-methylpyrrolidone and N,N-dimethylformamide. Examples of organic amines include primary amines such as methylamine, ethylamine, n-propylamine, 2-ethanolamine, and 2-amino-2-methyl-1-propanol; secondary amines such as dimethylamine, 2-(methylamino)ethanol, and 2-(ethylamino)ethanol; tertiary amines such as 2-dimethylaminoethanol, 2-diethylaminoethanol, and 1-dimethylamino-2-propanol; and quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0029] Examples of the water-soluble aromatic polyamideimide resin or its precursor include a polyamideimide resin or its precursor obtained by reacting a diisocyanate and / or a diamine with a tribasic acid anhydride (or tribasic acid chloride) as an acid component. Examples of diisocyanates include 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-diphenylmethane diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, paraphenylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, tolylene diisocyanate, and isophorone diisocyanate. These diisocyanates may be used alone or in combination of two or more. In order to improve the stability of the aromatic polyamide-imide resin, the diisocyanate may be a blocked isocyanate in which the isocyanate group is stabilized with a blocking agent, such as alcohol, phenol, or oxime.

[0030] Examples of diamines include 3,3'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, xylylenediamine, phenylenediamine, and isophoronediamine. These diamines may be used alone or in combination of two or more.

[0031] An example of the tribasic acid anhydride is trimellitic anhydride, and an example of the tribasic acid chloride is trimellitic anhydride chloride. As the tribasic acid anhydride, trimellitic anhydride is preferred from the viewpoint of reducing the burden on the environment.

[0032] When producing an aromatic polyamideimide resin, in addition to the above-mentioned tribasic acid anhydride (or tribasic acid chloride), a dicarboxylic acid, a tetracarboxylic acid dianhydride, or the like may be used as an acid component within a range that does not impair the properties of the polyamideimide resin. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. Examples of tetracarboxylic dianhydrides include pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and biphenyltetracarboxylic dianhydride. These may be used alone or in combination of two or more. The total amount of carboxylic acids other than tribasic acids (dicarboxylic acids and tetracarboxylic acids) is preferably in the range of 0 to 30 mol % of the total carboxylic acids, from the viewpoint of maintaining the properties of the polyamideimide resin.

[0033] The ratio of diisocyanate and / or diamine to acid component (total amount of tribasic acid anhydride or tribasic acid anhydride chloride and dicarboxylic acid and tetracarboxylic acid dianhydride used as needed) used is preferably 0.8 to 1.1 mol, more preferably 0.95 to 1.08 mol, and even more preferably 1.0 to 1.08 mol, of diisocyanate compound and / or diamine compound per 1.0 mol of total amount of acid component, from the viewpoint of molecular weight and degree of crosslinking of the polyamideimide resin produced.

[0034] The water-soluble aromatic polyamide-imide resin or its precursor can be obtained by copolymerizing the above-mentioned diisocyanate and / or diamine with the above-mentioned acid component in a polar solvent. Examples of polar solvents include N-methyl-2-pyrrolidone, N-formylmorpholine, N-acetylmorpholine, N,N'-dimethylethyleneurea, N,N-dimethylacetamide, N,N-dimethylformamide, and γ-butyrolactone. From the viewpoint of carrying out the amide-imidization reaction at high temperature in a short time, a high-boiling point solvent is preferred, and N-methyl-2-pyrrolidone is generally used from the viewpoint of solubility. N-formylmorpholine is also preferred from the viewpoints of the working environment and ease of safety management. The amount of polar solvent used is usually preferably 50 to 500 parts by mass per 100 parts by mass of the total amount of diisocyanate or diamine and acid component, from the viewpoint of the solubility of the resulting aromatic polyamideimide resin or precursor thereof. The polymerization temperature is usually in the range of 80 to 180° C., and in order to reduce the influence of moisture in the air, it is preferable to carry out the polymerization in an atmosphere such as nitrogen.

[0035] Water-soluble aromatic polyamide-imide resins or their precursors can be produced by, for example, (1) a method of using and reacting an acid component and a diisocyanate component and / or a diamine component at the same time; (2) a method of reacting an acid component with an excess of a diisocyanate component and / or a diamine component to synthesize an amide-imide oligomer having an isocyanate group or an amino group at the terminal, and then adding an acid component to react with the terminal isocyanate group and / or amino group; or (3) a method of reacting an excess of an acid component with a diisocyanate component and / or a diamine component to synthesize an amide-imide oligomer having an acid or acid anhydride group at the terminal, and then adding a diisocyanate component and / or a diamine component to react with the terminal acid or acid anhydride group.

[0036] The number average molecular weight (Mn) of the water-soluble aromatic polyamideimide resin or its precursor is preferably at least 5,000, more preferably at least 10,000, and even more preferably at least 15,000. On the other hand, Mn is preferably at most 50,000, more preferably at most 30,000, and even more preferably at most 25,000. When Mn is within this range, the solubility of the aromatic polyamideimide resin or its precursor in water and the mechanical properties such as flex resistance of the molded product obtained from this dispersion can be ensured. The Mn of the aromatic polyamide-imide resin or its precursor can be controlled within the above range by appropriately sampling the reaction solution during polymerization, measuring the sample by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene, and continuing polymerization until the desired Mn is reached.

[0037] Examples of aromatic polyetherimides include amorphous polymers having imide bonds and ether bonds in the main chain, and a polycondensate of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane and m-phenylenediamine is preferred. Commercially available aromatic polyetherimides include "Ultem 1000F3SP" (manufactured by SABIC).

[0038] The acid value of the imide-based resin P is 20 to 100 mg / KOH. In this dispersion, the acid value of the imide-based resin P is adjusted within this range to balance its functions. That is, if the acid value of the imide-based resin P is less than 20 mg / KOH, the reaction rate of the imide-based resin P when forming a molded product from the dispersion is improved, improving the physical properties of the molded product, but its dispersing effect is reduced, resulting in a decrease in the dispersion stability of the dispersion. On the other hand, if the acid value of the imide-based resin P is more than 100 mg / KOH, the dispersing effect of the imide-based resin P in the dispersion is enhanced, but the reaction rate of the imide-based resin P when forming a molded product from the dispersion is reduced, resulting in a decrease in the physical properties of the molded product. More specifically, when the acid value is 20 mgKOH / g or more, the imide-based resin P has many acidic groups, which tends to make it easier to make it water-soluble, to facilitate interactions between the imide-based resin P, the F particles, and water, and to facilitate adhesion of molded articles formed from the dispersion to substrates. Furthermore, when the acid value is 100 mgKOH / g or less, the storage stability of the dispersion tends to improve. From these viewpoints, the acid value of the imide resin P is preferably 35 to 70 mgKOH / g. When the imide resin P has an acid anhydride group, the acid value when the acid anhydride group is ring-opened is defined as the acid value of the imide resin P.

[0039] The acid value can be measured by taking approximately 0.5 g of imide resin P, adding approximately 0.15 g of 1,4-diazabicyclo[2.2.2]octane, and then adding approximately 60 g of N-methyl-2-pyrrolidone and approximately 1 ml of ion-exchanged water, and stirring until the imide resin P is completely dissolved. The acid value can be measured by titrating the mixture with a 0.05 mol / L ethanolic potassium hydroxide solution using a potentiometric titrator.

[0040] Suitable specific examples of the imide resin P include "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.).

[0041] The content of F particles in the dispersion is preferably 10% by mass or more, more preferably 25% by mass or more, based on the total mass of the dispersion. The content of F particles is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the dispersion. The content of imide-based resin P in the dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the total mass of the dispersion. The content of imide-based resin P is preferably 30% by mass or less, more preferably 10% by mass or less.

[0042] The total content of the F particles and the imide-based resin P in the dispersion is preferably 20% by mass or more relative to the total mass of the dispersion. The total content is more preferably 30% by mass or more, and even more preferably 40% by mass or more. The total content is preferably 80% by mass or less. A specific example of a suitable range for the total content is 30 to 80% by mass. In this case, a molded product such as a coating film can be formed from the dispersion with high uniformity, and the physical properties of the F polymer and the imide-based resin P are easily exhibited to a high degree. That is, even when the content of the polymer component is in such a high range, the dispersion has excellent dispersion stability due to the above-mentioned mechanism of action, and the physical properties of the molded product can be improved.

[0043] Furthermore, the ratio of the mass of the imide resin P to the mass of the F particles in the dispersion is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.01 or more. This ratio is preferably 0.1 or less, more preferably 0.09 or less, and even more preferably 0.05 or less. Specific examples of suitable ranges for this ratio include 0.001 to 0.1. When the ratio is in this low range, the dispersion stability of the F particles is improved, and the physical properties of the molded article obtained from this dispersion are particularly likely to be improved. The reason for this is not entirely clear, but it is thought that in this dispersion, in which the acid value of the imide-based resin P and the pH of the aqueous dispersion are within a predetermined range and the imide-based resin P is a minor component relative to the F particles, the imide-based resin P is more likely to function highly as a dispersant and binder for the low-hydrophilic F particles. In other words, the imide-based resin P adheres to the surfaces of the F particles and promotes dense sintering of the F particles during the formation of the molded article.

[0044] The water content in the present dispersion is preferably 40% by mass or more, more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less. Within this range, the dispersion stability of the present dispersion is more likely to be improved due to the above-mentioned mechanism of action.

[0045] The dispersion may further contain a water-soluble dispersion medium other than water, which 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.

[0046] The dispersion may further contain a surfactant. When the 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 present dispersion further contains a surfactant, a nonionic surfactant having an alcoholic hydroxyl group is preferred, and a polyoxyalkylene alkyl ether, an acetylene surfactant, or a silicone surfactant is more preferred. 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 viscosity of the present dispersion, and the silicone surfactant improves the initial dispersibility of the F particles, it is preferable to use a polyoxyalkylene alkyl ether in combination with a silicone surfactant. When the present dispersion further contains a surfactant, the amount thereof is preferably 1 to 15% by mass relative to the total mass of the present dispersion, which enhances the affinity between the components and tends to further improve the dispersion stability of the present dispersion.

[0047] The silicone surfactant is preferably a polyoxyalkylene-modified polydimethylsiloxane having a weight-average molecular weight of 3000 or less and an HLB value of 1 to 18 calculated by the Griffin equation, from the viewpoint of reducing the burden on the environment and from the viewpoint of stability in the dispersion.

[0048] The polyoxyalkylene-modified polydimethylsiloxane (hereinafter also referred to as "modified polydimethylsiloxane") is an organopolysiloxane having a polyoxyalkylene structure as a hydrophilic group and a polydimethylsiloxane structure as a hydrophobic group, and is preferably a linear polymer.

[0049] The weight average molecular weight of the modified polydimethylsiloxane is 3000 or less, preferably 2500 or less, and more preferably 2000 or less. The weight average molecular weight is preferably 100 or more, and more preferably 500 or more. The number average molecular weight of the modified polydimethylsiloxane is preferably 3000 or less, more preferably 1500 or less, and is preferably 100 or more, more preferably 500 or more. The molecular weight dispersity of the modified polydimethylsiloxane is preferably less than 2.0, more preferably 1.8 or less, and the lower limit of the molecular weight dispersity is preferably more than 1.0.

[0050] The HLB value of the modified polydimethylsiloxane is 1 to 18, preferably 3 or more, more preferably 6 or more, even more preferably 10 or more, and particularly preferably 12 or more. The HLB value is preferably 16 or less, more preferably 15 or less.

[0051] The static surface tension of the modified polydimethylsiloxane is preferably 28 mN / m or less, more preferably 26 mN / m or less, and is preferably 15 mN / m or more, more preferably 20 mN / m or more. The dynamic surface tension of the modified polydimethylsiloxane is preferably 40 mN / m or less, more preferably 35 mN / m or less, and preferably 20 mN / m or more.

[0052] Modified polydimethylsiloxane has dimethylsiloxane units (-(CH3)2SiO) in the main chain. 2 / 2 -), may have dimethylsiloxane units in the side chain, or may have dimethylsiloxane units in both the main chain and the side chain. The modified polydimethylsiloxane is preferably a modified polydimethylsiloxane containing dimethylsiloxane units in the main chain and oxyalkylene groups in the side chains, or a modified polydimethylsiloxane containing dimethylsiloxane units in the main chain and oxyalkylene groups at the main chain terminals.

[0053] Specific examples of modified polydimethylsiloxanes include "BYK-347," "BYK-349," "BYK-378," "BYK-3450," "BYK-3451," "BYK-3455," and "BYK-3456" (all manufactured by BYK Japan); and "KF-6011" and "KF-6043" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0054] The modified polydimethylsiloxane has a low weight-average molecular weight and an HLB value within a specific range, and therefore its hydrophobic and hydrophilic properties are well balanced. Such modified polydimethylsiloxane is thought to easily enhance interactions with F particles, which is thought to result in improved dispersion stability of the present dispersion. Furthermore, since modified dimethylsiloxane has excellent thermal decomposition properties, it is easily decomposed when the dispersion is heated to form a baked product, and as a result, the baked product is likely to have a high degree of physical properties based on the F polymer.

[0055] The polyoxyalkylene alkyl ether is preferably polyoxyethylene decyl ether, polyoxyethylene undecyl ether, polyoxyethylene dodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene tetradecyl ether, triethylene glycol monomethyl ether, polyethylene glycol trimethylnonyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether acetate, or diethylene glycol monobutyl ether acetate, and more preferably polyoxyethylene decyl ether, polyoxyethylene undecyl ether, polyoxyethylene dodecyl ether, polyoxyethylene tridecyl ether, or polyoxyethylene tetradecyl ether.

[0056] Polyoxyalkylene alkyl ethers are commercially available, and specific examples 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.); and "Leocol TDN-90-80" and "Leocol SC-90" (all manufactured by Lion Specialty Chemicals).

[0057] When the dispersion contains a surfactant, the polyoxyalkylene alkyl ether is available as a commercially available product, and specific examples include "Tergitol TMN-100X" (manufactured by The Dow Chemical Company) and "Lutensol TO8." When the dispersion further contains a surfactant, the amount of the surfactant is preferably 0.1% by mass or more, more preferably 0.1% by mass or more, and preferably 15% by mass or less, based on the total mass of the dispersion.

[0058] The present dispersion may further contain at least one nonionic polymer selected from the group consisting of polyvinyl alcohol-based polymers, polyvinylpyrrolidone-based polymers, and polysaccharides. It is highly preferable that such a nonionic polymer be a water-soluble polymer. In this case, the interaction between the water-soluble polymer and the imide-based resin P improves not only the dispersion stability but also the rheological properties of the present dispersion, further improving the handling properties of the present dispersion, such as film-forming properties. As a result, the present dispersion is more likely to be used to form thick molded products or molded products of any shape. This tendency is particularly pronounced when the water-soluble polymer has nonionic hydroxyl groups. The polyvinyl alcohol polymer may be a partially acetylated or partially acetalized polyvinyl alcohol. Examples of polysaccharides include glycogens, amicropectins, dextrins, glucans, fructans, chitins, amyloses, agaroses, amicropectins, and celluloses, such as methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose.

[0059] The water-soluble nonionic 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.).

[0060] Furthermore, when the present dispersion further contains a water-soluble nonionic polymer, the amount thereof is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, relative to the total mass of the present dispersion. The amount is preferably less than 1% by mass. The ratio of the mass of the water-soluble nonionic polymer to the mass of the F particles in the present dispersion is preferably 0.001 or more, more preferably 0.01 or more. The ratio is preferably less than 0.1. As described above, the interaction between the water-soluble polymer and the imide-based resin P facilitates the improvement of the liquid properties and film-forming properties of the dispersion by adding a small amount of the water-soluble polymer. As a result, the amount of the water-soluble polymer remaining in the molded product obtained from the dispersion is reduced, and molded products with superior physical properties, such as electrical properties, are easily obtained from the dispersion. This tendency is particularly pronounced when the water-soluble polymer has a nonionic hydroxyl group.

[0061] The present dispersion may further contain an amine or ammonia. The amine or ammonia also functions as a pH adjuster, and is thought to contribute to improving the dispersion stability and storage stability of the present dispersion. When the present dispersion further contains an amine or ammonia, the amount thereof may be such that the pH of the present dispersion is 5 to 10.

[0062] Examples of the amine include dimethylamine, diethylamine, diisopropylamine, diethanolamine, triethanolamine, tripropanolamine, triethylamine, triamylamine, pyridine, and N-methylmorpholine. In this case, a pH buffer may be further added to stabilize the pH of the liquid composition. Examples of pH buffers include tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium hydrogen carbonate, ammonium carbonate, and ammonium acetate.

[0063] From the viewpoint of improving the adhesiveness and low linear expansion of a molded article formed from the dispersion, the dispersion may further contain a resin material other than the F polymer and the imide-based resin P. Such a resin material may be thermosetting or thermoplastic, may be modified, and may be dissolved in the dispersion or may be dispersed without being dissolved. Examples of such resin materials include acrylic resins, phenolic resins, liquid crystalline polyesters, liquid crystalline polyesteramides, polyolefin resins, modified polyphenylene ethers, polyfunctional cyanate ester resins, polyfunctional maleimide-cyanate ester resins, polyfunctional maleimides, aromatic elastomers such as styrene elastomers, vinyl ester resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, melamine-urea co-condensation resins, polycarbonates, polyarylates, polysulfones, polyarylsulfones, aromatic polyamides, aromatic polyetheramides, polyphenylene sulfides, polyaryl ether ketones, polyphenylene ethers, and epoxy resins. When the present dispersion further contains a resin material, the content thereof is preferably 40% by mass or less relative to the mass of the entire present dispersion.

[0064] A preferred embodiment of the resin material is an aromatic polymer. The aromatic polymer is preferably polyphenylene ether or an aromatic elastomer (such as a styrene elastomer). In this case, not only is the adhesiveness and low linear expansion of the molded article formed from the dispersion further improved, but the liquid properties (viscosity, thixotropy ratio, etc.) of the dispersion are well balanced, which makes the article easier to handle. Here, examples of styrene elastomers include copolymers of styrene and conjugated dienes or (meth)acrylic acid esters (styrene-butadiene rubber, styrene-based core-shell copolymers, styrene-based block copolymers, etc.), and styrene elastomers that have the properties of both rubber and plastic and become plasticized by heating to exhibit flexibility are preferred.

[0065] The present dispersion may further contain an inorganic filler. In this case, the molded product produced from the present dispersion is likely to have excellent electrical properties and low linear expansion. Furthermore, even if the present dispersion contains an inorganic filler, the above-mentioned mechanism of action allows the excellent dispersion stability, making it easy to obtain a dense molded product. Therefore, the present dispersion containing an inorganic filler can easily produce a molded product that has high levels of the physical properties of the F polymer, the imide-based resin P, and the inorganic filler. The inorganic filler is preferably a nitride filler or an inorganic oxide filler, more preferably a boron nitride filler, aluminum nitride filler, beryllia filler (beryllium oxide filler), silicate filler (silica filler, wollastonite filler, talc filler), or metal oxide (cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.) filler, and even more preferably a silica filler. 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.).

[0066] The inorganic filler preferably has a D50 of 20 μm or less, more preferably 10 μm or less, and preferably has a D50 of 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, micaceous, block-like, flat, wedge-like, rosette-like, net-like, and prismatic shapes. The inorganic filler may be used alone or in combination of two or more. When the present dispersion further contains an inorganic filler, the amount thereof is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, based on the total mass of the present dispersion.

[0067] 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 (such as the "SFP (registered trademark)" series manufactured by Denka Co., Ltd.), titanium oxide coated with a polyhydric alcohol and an inorganic substance (such as the "Tipaque (registered trademark)" series manufactured by Ishihara Sangyo Kaisha, Ltd.), and rutile-type titanium oxide surface-treated with alkylsilane (such as the "Tipaque (registered trademark)" series manufactured by Teika Co., Ltd.). JMT (registered trademark) series, etc.), hollow silica fillers (the E-SPHERES series manufactured by Taiheiyo Cement Corporation, the Silinax series manufactured by Nittetsu Mining Co., Ltd., the Ecocosfire series manufactured by Emerson & Cumming Co., Ltd., etc.), talc fillers (the SG series manufactured by Nippon Talc Co., Ltd., etc.), steatite fillers (the BST series manufactured by Nippon Talc Co., Ltd., etc.), boron nitride fillers (the UHP series manufactured by Showa Denko KK, the Denka Boron Nitride series (GP, HGP grades), etc.) manufactured by Denka Co., Ltd.

[0068] In addition to the above components, the present dispersion may further contain other components such as a thixotropy-imparting agent, a viscosity modifier, an antifoaming agent, a silane coupling agent, a dehydrating agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a brightener, a colorant, a conductive agent, a release agent, a surface treatment agent, a flame retardant, and various fillers, as long as the effects of the present invention are not impaired.

[0069] The viscosity of the dispersion is preferably 10 mPa·s or more, more preferably 30 mPa·s or more, and even more preferably 50 mPa·s or more. The viscosity of the dispersion is preferably 3000 mPa·s or less, more preferably 1000 mPa·s or less, and even more preferably 800 mPa·s or less. The viscosity of the dispersion is preferably 50 to 3000 mPa·s, and more preferably 50 to 1000 mPa·s.

[0070] The thixotropy ratio of the present dispersion is preferably 1.0 or more. The thixotropy ratio of the present dispersion is preferably 3.0 or less, more preferably 2.0 or less. In this case, the present dispersion has excellent coatability and homogeneity, and is likely to form a denser molded product (polymer layer, etc.). The pH of the dispersion is 5 to 10. By adjusting the pH within this range, the functions of the imide resin P are balanced. That is, if the pH of the dispersion is less than 5, the reactivity of the imide resin P increases, but its dispersing action decreases, resulting in a decrease in the dispersion stability of the dispersion. On the other hand, if the pH of the dispersion is more than 10, the dispersing action of the imide resin P increases, but its reactivity decreases, resulting in a decrease in the physical properties of the molded product obtained from the dispersion. The pH of the dispersion is preferably 7 to 9. In this case, the hue and long-term storage stability of the dispersion tend to be excellent.

[0071] In this dispersion, the dispersion layer ratio is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. Here, the dispersion layer ratio is a value calculated by the following formula when the dispersion (18 mL) is placed in a screw tube (internal volume: 30 mL) and left to stand at 25°C for 14 days, from the height of the entire dispersion in the screw tube and the height of the sedimentation layer (dispersion layer). Note that if no sedimentation layer is observed after standing and there is no change in the state, it is assumed that there is no change in the height of the entire dispersion, and the dispersion layer ratio is 100%. Dispersion layer rate (%) = (height of sedimentation layer) / (height of total dispersion liquid) × 100

[0072] Due to the above-mentioned mechanism of action, the present dispersion has excellent dispersion stability, particularly long-term storage stability. When the present dispersion is allowed to stand at 25°C for 30 days, the fluctuation range (absolute value) of the thixotropy ratio of the present dispersion before and after standing is preferably 3 or less, and preferably less than 1.

[0073] The dispersion can be prepared by mixing F particles, imide-based resin P, and water as a dispersion medium. Examples of mixing methods include adding the F particles and imide-based resin P to water all at once or sequentially and mixing; premixing the F particles with water, and the imide-based resin P with water, and then further mixing the resulting mixtures. The dispersion can be prepared by pre-dispersing the F particles in water and then adding the imide-based resin P directly or after mixing with water, or by pre-mixing the imide-based resin P in water and then adding the F particles directly or after mixing with water, which is advantageous and preferable from the perspective of more uniform dispersion of the F particles. If surfactants, other resin materials, or inorganic fillers are further added to the dispersion, they are preferably added simultaneously with the pre-dispersion of the F particles in water or before the F particles are dispersed.

[0074] Examples of mixing methods for preparing the dispersion include stirring using a stirring device equipped with uniaxial or multiaxial blades (stirring blades) such as propeller blades, turbine blades, paddle blades, and shell-shaped blades, or a Henschel mixer, pressure kneader, Banbury mixer, or planetary mixer; mixing using a disperser that uses media such as a ball mill, attritor, basket mill, sand mill, sand grinder, Dyno Mill (a bead mill that uses grinding media such as glass beads or zirconium oxide beads), Dispermat, SC mill, spike mill, or agitator mill; and mixing using a disperser that does not use media, such as a high-pressure homogenizer such as a Microfluidizer, Nanomizer, or Ultimizer, an ultrasonic homogenizer, a Dissolver, a Disper, a high-speed impeller disperser, a planetary mixer, or a thin-film swirling high-speed mixer.

[0075] A preferred embodiment of the method for producing the dispersion liquid includes kneading a composition containing F particles and water to obtain a kneaded product, and then further mixing the kneaded product with water. In this case, the imide-based resin P may be added to the composition, or may be added when further mixing the kneaded product with water, with the former being preferred. That is, a preferred embodiment is kneading a composition containing F particles, imide-based resin P, and water to obtain a kneaded product, and then further mixing the kneaded product with water. The kneading can be carried out by the above-mentioned mixing method, preferably using a Henschel mixer, a pressure kneader, a Banbury mixer, a planetary mixer, or a planetary mixer, more preferably using a planetary mixer. A planetary mixer has two agitating blades that rotate and revolve around each other, allowing it to mix and knead the mixture in the mixing vessel. This minimizes dead space in the mixing vessel where the agitating blades cannot reach, reducing the load on the blades and enabling the composition to be kneaded to a high degree. In other words, the F particles can be kneaded while suppressing aggregation, wetting the F particles with water, and allowing the F particles and imide-based resin P to interact highly. When the kneaded mixture is further mixed with water, it is easy to obtain a dispersion with excellent dispersion stability. Furthermore, the component concentrations of the dispersion can be easily adjusted, making it easy to obtain a dispersion that can be used to form thick molded products (e.g., polymer layers) with excellent surface smoothness and uniformity.

[0076] The content of F particles in the composition is preferably 20% by mass or more, more preferably 40% by mass or more, based on the total mass of the composition. The content of F particles is preferably 90% by mass or less. The content of imide-based resin P in the composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the total mass of the composition. The content of imide-based resin P is preferably 10% by mass or less. The total content of the F particles and the imide-based resin P in the composition is preferably 40% by mass or more, more preferably 60% by mass or more, based on the total mass of the composition, and is preferably 90% by mass or less.

[0077] The ratio of the mass of the imide resin P to the mass of the F particles in the composition is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.01 or more, and is preferably 0.1 or less, more preferably 0.09 or less, and even more preferably 0.05 or less. If the content of the F particles, the content of the imide-based resin P, or the ratio is within such a low range, the composition can be kneaded while allowing a high degree of interaction between the F particles and the imide-based resin P. Therefore, when the kneaded mixture is further mixed with water, it is easy to obtain a dispersion liquid having excellent dispersion stability, in which the ratio of the mass of the imide-based resin P to the mass of the F particles is in the range of 0.001 to 0.1.

[0078] The kneaded product is a semi-solid or solid kneaded product, and is preferably a kneaded paste or a kneaded powder. Note that the kneaded paste is a kneaded product in a state of fluidity and viscosity, and the kneaded powder is a kneaded product in a lump-like, clay-like state. The viscosity of the kneaded paste is preferably 800 to 100,000 mPa·s, and more preferably 1,000 to 10,000 mPa·s or more. The moisture content of the dough is preferably 50% by mass or less, more preferably 40% by mass or less, and more preferably 20% by mass or more, more preferably 25% by mass or more.

[0079] In this embodiment, when the dispersion further contains a surfactant, other resin material, or inorganic filler, these may be added to the composition or may be added when the kneaded material is mixed with water. The present dispersion containing other resin materials or inorganic fillers may be obtained by kneading a composition containing F particles, other resin materials or inorganic fillers, and water to obtain a kneaded mixture, and then mixing the kneaded mixture with a mixture containing the imide-based resin P and water. In this case, the dispersion stability and long-term storage stability of the present dispersion are likely to be improved.

[0080] The dispersion has excellent dispersion stability and long-term storage stability, and can form molded articles that have excellent flexibility such as bending resistance, i.e., crack resistance, and exhibit strong adhesion to substrates. This dispersion is applied to at least one surface of a substrate to form a liquid coating, and this liquid coating is heated to remove the dispersant to form a dry coating. The dry coating is then heated to bake the F polymer, thereby obtaining a laminate (hereinafter also referred to as "this laminate") having a polymer layer (hereinafter also referred to as "F layer") containing the F polymer and the imide-based resin P on the surface of the substrate. Furthermore, if the dispersion is applied to both surfaces of a substrate and heated to bake the F polymer, a laminate having an F layer on both sides of a substrate layer made of the substrate can be obtained.

[0081] Examples of the substrate include metal substrates (metal foils such as copper, nickel, aluminum, titanium, and alloys thereof), resin films (heat-resistant resin films containing one or more heat-resistant resins such as tetrafluoroethylene polymers, polyimides, polyarylates, polysulfones, polyarylsulfones, polyamides, polyetheramides, polyphenylene sulfide, polyaryletherketones, polyamideimides, liquid crystalline polyesters, and liquid crystalline polyesteramides, and may be single-layer or multilayer films), prepregs (precursors of fiber-reinforced resin substrates), ceramic substrates (ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride), and glass substrates. Among these, resin films are preferred, and it is more preferred that the resin constituting the resin film is a polyimide-based resin. This dispersion is suitably used to form an F layer by applying it to at least one surface of a resin film and drying it. The shape of the substrate may be flat, curved, or uneven, and may be any of foil, plate, film, and fiber.

[0082] The method for applying the present dispersion to the surface of a substrate may be any method that forms a stable liquid coating (wet film) of the present dispersion on the surface of a resin film (substrate), and examples thereof include a coating method, a droplet ejection method, and a dipping method, with the coating method being preferred. The coating method allows for efficient formation of a liquid coating on the surface of a resin film using simple equipment. Examples of the coating method include spraying, roll coating, spin coating, gravure coating, microgravure coating, gravure offset, knife coating, kiss coating, bar coating, die coating, fountain-meyer bar coating, slit coating, slot die coating, and dip coating.

[0083] When drying the liquid coating, the liquid coating is heated to a temperature at which the dispersion medium (water) volatilizes, and a dry coating is formed on the surface of the resin film. The heating temperature for such drying is preferably 100 to 200° C. Air may be blown in the step of removing the dispersion medium. During drying, the dispersion medium does not necessarily have to be completely evaporated, but it is sufficient to evaporate it to an extent that the layer shape after holding is stable and a free-standing film can be maintained.

[0084] When baking the F polymer, it is preferable to heat the dried coating to a temperature equal to or higher than the melting point of the F polymer, and the heating temperature is preferably 380°C or lower. Examples of heating methods include a method using an oven, a method using a ventilation drying furnace, and a method using heat rays such as infrared rays. Heating may be performed under either normal pressure or reduced pressure. The heating atmosphere may be any of an oxidizing gas atmosphere (oxygen gas, etc.), a reducing gas atmosphere (hydrogen gas, etc.), or an inert gas atmosphere (helium gas, neon gas, argon gas, nitrogen gas, etc.). The heating time is preferably 0.1 to 30 minutes, more preferably 0.5 to 20 minutes. By heating under the above conditions, the F layer can be suitably formed while maintaining high productivity.

[0085] The thickness of the F layer is preferably 0.1 to 150 μm, more preferably 10 μm or more. When the base layer is a metal foil, the thickness of the F layer is preferably 10 to 30 μm. When the base layer is a resin film, the thickness of the F layer is preferably 10 to 150 μm, more preferably 15 to 50 μm. The peel strength between the F layer and the base layer is preferably 10 N / cm or more, more preferably 15 N / cm or more. The peel strength is preferably 100 N / cm or less. By using the present dispersion, the present laminate can be easily formed without impairing the physical properties of the F polymer in the F layer.

[0086] The porosity of the F layer is preferably 30% or less, more preferably 20% or less. The porosity is preferably 0.1% or more, more preferably 1% or more. From this dispersion, it is easy to form an F layer with such a low porosity. In particular, even when the porosity of the dried coating is 1% or more, it is easy to form an F layer with a low porosity. The porosity is determined by determining the void areas of the F layer through image processing from an SEM photograph of the cross section of a molded product observed using a scanning electron microscope (SEM), and then dividing the area occupied by the void areas by the area of ​​the F layer (%). The area occupied by the void areas can be determined by approximating the void areas as circles.

[0087] The present 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, the present laminate is obtained, which has a substrate layer made of the substrate and an F layer on one surface of the substrate layer, while in the latter case, the present laminate is obtained, which has a substrate layer made of the substrate and an F layer on both surfaces of the substrate layer. The latter present laminate is less likely to warp, and therefore is easier to handle during processing. Specific examples of the present laminate include a metal-clad laminate having a metal foil and an F layer on at least one surface of the metal foil, and a multilayer film having a polyimide film and an F layer on both surfaces of the polyimide film. These present laminates are suitable as printed circuit board materials and can be used to manufacture flexible printed circuit boards and rigid printed circuit boards because they have excellent physical properties such as electrical properties.

[0088] The present laminate having F layers on both sides of the substrate layer is preferably obtained by applying the present dispersion to one surface of the substrate, heating to remove the liquid dispersion medium, applying the present dispersion to the other surface of the substrate, heating to remove the liquid dispersion medium, and further heating to bake the F polymer, thereby forming each F layer.

[0089] Alternatively, the present laminate having F layers on both sides of the substrate layer may be obtained by applying the present dispersion to both surfaces of the substrate, heating to remove the liquid dispersion medium, and further heating to bake the F polymer, thereby simultaneously forming F layers on both surfaces. In this case, the present laminate having the F layer on both sides of the substrate layer is preferably obtained by immersing the substrate in the present dispersion, applying the present dispersion to both surfaces of the substrate, and then passing through a firing furnace and heating. Specifically, it is more preferable to obtain the laminate by immersing the substrate in the present dispersion, and then passing through a firing furnace and heating the substrate while lifting it out of the present dispersion. The substrate is preferably pulled up vertically and passed through the firing furnace in an upward direction. In this case, a smooth F layer is easily formed. After the substrate is pulled up vertically, it may be further heated while being pulled down vertically, or it may be pulled down vertically without being heated. The amount of the present dispersion applied to the substrate can be adjusted by passing the substrate, to which the present dispersion has been applied, between a pair of rolls. The laminate can be suitably produced using an apparatus having a dip coater and a firing furnace, such as a vertical firing furnace or a glass cloth coating machine manufactured by Tabata Kikai Kogyo Co., Ltd.

[0090] Here, the outermost surface of the substrate may be further surface-treated in order to further improve its low linear expansion property and adhesiveness. Examples of the surface treatment method include annealing treatment, corona treatment, plasma treatment, ozone treatment, excimer treatment, and silane coupling treatment. The annealing conditions are preferably a temperature of 120 to 180° C., a pressure of 0.005 to 0.015 MPa, and a time of 30 to 120 minutes. Gases used in the plasma treatment include oxygen gas, nitrogen gas, rare gas (argon, etc.), hydrogen gas, ammonia gas, and vinyl acetate. These gases may be used alone or in combination of two or more. The ten-point average roughness of the surface of the substrate is preferably 0.01 to 0.05 μm.

[0091] The laminate, whose base layer is a resin film (preferably a polyimide film), is useful as a release film or carrier film. The laminate has excellent adhesion between the F layer and the base layer, making it difficult for delamination to occur, allowing it to be used repeatedly as a carrier film. Furthermore, the F layer has excellent heat resistance, so its release properties are unlikely to deteriorate even after repeated use.

[0092] Specifically, a dispersion or varnish containing a resin or inorganic filler is applied to the surface of the F layer of the present laminate, dried to form a coating film, and then the present laminate is peeled off from the coating film to obtain an independent coating film. For example, after forming the coating film on the surface of the F layer of the present laminate, the coating film side of the present laminate having such a coating film is attached to another substrate, and the present laminate is peeled off to obtain a laminate of the other substrate and the coating film. When forming a coating film on the surface of the F layer of the present laminate, for example, heating may be performed at a temperature below the melting point of the F polymer during drying. The present laminate has excellent heat resistance and is therefore resistant to deformation even after repeated heat treatments.

[0093] Specifically, the present laminate is useful as a carrier film for forming ceramic green sheets, a carrier film for forming secondary batteries, a carrier film for forming solid polymer electrolyte membranes, and a carrier film for forming catalysts for solid polymer electrolyte membranes. When the present laminate is used as a carrier film, from the viewpoint of obtaining a coating film with a uniform thickness, the ratio of the thickness of the edge portion to the thickness of the center portion of the present laminate is preferably 1.1 or less, more preferably 1.07 or less, and even more preferably 1.04 or less. The thickness ratio is 1 or more.

[0094] Another substrate may be further laminated on the outermost surface of this laminate. Other substrates include metal substrates, heat-resistant resin films, prepregs which are precursors of fiber-reinforced resin plates, laminates having a heat-resistant resin film layer, and laminates having a prepreg layer. The prepreg is a sheet-like substrate in which a base material (tow, woven fabric, etc.) of reinforcing fibers (glass fiber, carbon fiber, etc.) is impregnated with a thermosetting resin or a thermoplastic resin. The metal substrate may be any of the metal substrates described above. The heat-resistant resin film is a film containing one or more heat-resistant resins, and examples of the heat-resistant resin include the resins described above.

[0095] As a lamination method, there is a method in which the present laminate and another substrate are heat-pressed. When the other substrate is a prepreg, the heat pressing conditions are preferably a temperature of 120 to 400°C, a vacuum atmosphere of 20 kPa or less, and a pressing pressure of 0.2 to 10 MPa. Because this laminate has an F layer with excellent electrical properties, it is suitable as a printed circuit board material, and specifically can be used as a flexible metal-clad laminate or a rigid metal-clad laminate to manufacture printed circuit boards, and can be particularly suitable as a flexible metal-clad laminate to manufacture flexible printed circuit boards.

[0096] A printed circuit board can be obtained by etching the metal foil of this laminate (metal foil with F layer), which has a metal foil base layer, or a metal-clad laminate (resin film and metal foil with F layer), which has a resin film base layer and an F layer, and further laminated with metal foil, to form a transmission circuit. Specifically, printed circuit boards can be manufactured by etching the metal foil to process it into the desired transmission circuit, or by processing the metal foil into the desired transmission circuit using an electrolytic plating method (semi-additive method (SAP method), MSAP method, etc.). A printed circuit board manufactured from metal foil with an F layer, and a resin film and metal foil with an F layer, has a transmission circuit formed from metal foil and an F layer, in this order. Specific examples of the configuration of the printed circuit board include transmission circuit / F layer / prepreg layer, transmission circuit / F layer / prepreg layer / F layer / transmission circuit, transmission circuit / F layer / polyimide film layer, and transmission circuit / F layer / polyimide film layer / F layer / transmission circuit. In the manufacture of such a printed circuit board, an interlayer insulating film may be formed on a transmission circuit, a solder resist may be laminated on the transmission circuit, or a coverlay film may be laminated on the transmission circuit. These interlayer insulating films, solder resists, and coverlay films may be formed using the present dispersion.

[0097] The present laminate, in which the base layer is a metal substrate, is excellent in insulation and heat dissipation properties, and is therefore useful as a heat dissipation substrate, and can be particularly suitably used as a substrate for mounting power semiconductors. In such a case, the substrate is preferably in the form of a plate, and the substrate is preferably a copper plate or an aluminum plate, and the thickness of the substrate is preferably 0.1 to 3 mm. In the production of the present laminate in such a case, the method for applying the present dispersion to the substrate is preferably a slit coating method. In such a case, the F polymer is preferably an F polymer having a melting temperature of 200 to 320° C., and more preferably a polymer having an oxygen-containing polar group containing the above-mentioned TFE unit and PAVE unit.

[0098] In such a case, the imide resin P is preferably an aromatic polyimide, an aromatic polyimide precursor, an aromatic polyamideimide, or an aromatic polyamideimide precursor. In such a case, it is preferable that the F layer further contains an inorganic filler, preferably a boron nitride filler, an aluminum nitride filler, or an aluminum oxide filler. In other words, in the present laminate used as a heat dissipation substrate, the F polymer is preferably a polymer having an oxygen-containing polar group containing the above-mentioned TFE unit and PAVE unit, the imide-based resin P is preferably an aromatic polyimide, an aromatic polyimide precursor, an aromatic polyamideimide, or an aromatic polyamideimide precursor, and the F layer preferably contains a boron nitride filler, an aluminum nitride filler, or an aluminum oxide filler. In this case, the insulating property and heat dissipation property of the present laminate as a heat dissipation substrate are particularly likely to be improved.

[0099] When the present laminate is used as a heat dissipation substrate, it is preferable to process the present laminate into a laminate having a metal layer, an F layer, and another metal layer in this order. Such a laminate may be obtained by thermocompression bonding a metal substrate to the surface of the F layer of the present laminate, or by stacking two present laminates with their F layers facing each other and then thermocompression bonding the F layers, the latter being preferred. As a method for thermocompression bonding, heat pressing is preferred. The thicknesses of the two metal layers in such a laminate may be the same or different, and the metals in the two metal layers may be the same or different. For example, if the F layer of this laminate, which has an F layer on the surface of a 1 mm thick aluminum plate, and the F layer of this laminate, which has an F layer on the surface of a 0.5 mm thick copper plate, are hot-pressed and thermocompressed together, a laminate having an aluminum plate, an F layer, and a copper plate in that order, with the two metal layers having different thicknesses, is obtained.

[0100] The present laminate and laminates of the present laminate with other substrates are useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sporting goods, food industry supplies, paints, heat dissipation parts, cosmetics, etc., and specific examples include electric wire coating materials (aircraft electric wires, etc.), electrical insulating tape, insulating tape for oil drilling, 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 parts (load bearings, sliding shafts, valves, bearings, gears, cams, belt conveyors, food transport belts, etc.), tools (shovels, files, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, dies, toilets, container coating materials, heat dissipation substrates for mounting power devices, transistors, thyristors, rectifiers, transformers, power MOS These materials are useful as FETs, CPUs, heat dissipation fins, metal heat sinks, blades for wind turbines, wind power generation equipment, aircraft, etc., housings for personal computers and displays, electronic device components, interior and exterior components for automobiles, sealing materials for processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, plasma processing equipment, etc., heat dissipation parts in processing units for sputtering and various dry etching equipment, etc., and electromagnetic wave shielding materials.

[0101] The present dispersion, the method for producing the present dispersion, and the present laminate have been described above, but the present invention is not limited to the configurations of the above-mentioned embodiments. For example, the present dispersion and the present laminate may have any other configuration added to the configurations of the above-mentioned embodiments, or may be replaced with any configuration that exhibits a similar function. Furthermore, the method for producing the present dispersion may have any other additional step added to the configurations of the above-mentioned embodiments, or may be replaced with any step that produces a similar effect. [Example]

[0102] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1.Details of each ingredient [F particle] F particle 1: Contains 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units, in that order, and has a carbonyl group-containing group with a main chain carbon number of 1×10 6 Particles (D50: 2.1 μm) made of polymer (melting temperature: 300°C) with 1000 particles per particle F particle 2: Contains 97.5 mol% TFE units and 2.5 mol% PPVE units, in that order, and has a carbonyl group-containing group with a main chain carbon number of 1×10 6 Particles (D50: 1.8 μm) made of polymer (melting temperature 305°C) with 25 particles per particle F Particle 3: Particles made of non-thermoplastic PTFE (D50: 0.2 μm) [F dispersion] F dispersion 1: Aqueous dispersion containing 60% by mass of F particles 3 (AGC "AD-911E") [Imide resin varnish] Varnish 1: Water varnish containing a precursor of aromatic polyamide-imide (PAI1) (acid value: 50 mg KOH / g) [Surfactants] Surfactant 1: Polyoxyalkylene-modified polydimethylsiloxane having dimethylsiloxane units in the main chain and oxyethylene groups at the main chain end or side chain (weight average molecular weight: 1600, dispersity: 1.5, HLB value: 13, static surface tension: 25 mN / m, dynamic surface tension of 0.1% by mass aqueous solution: 30 mN / m) [pH adjuster] Amine 1: Triethanolamine Acid 1: Formic acid [Nonionic polymer] Polysaccharide 1: Hydroxyethyl cellulose (Sumitomo Seika Chemicals "HEC CF-Y") [a nonionic water-soluble polymer with hydroxyl groups] [Resin film (base material)] Polyimide film 1: Aromatic polyimide film (PI Advanced Materials "FG-100") with a thickness of 25 μm

[0103] 2. Preparation and evaluation of dispersion [Example 1-1] F Particles 1, Varnish 1, Surfactant 1, and water were placed in a pot, followed by the addition of zirconia balls. The pot was then rolled at 150 rpm for 1 hour, and Amine 1 was added to obtain Dispersion 1, containing F Particles 1 (60 parts by mass), PAI 1 (0.6 parts by mass), Surfactant 1 (3 parts by mass), and water (46.4 parts by mass). The viscosity of the resulting Dispersion 1 was 1000 mPa s, and the pH was 8.0. Dispersion 1 had excellent dispersibility, with no visible aggregates even after long-term storage at 25°C.

[0104] [Example 1-2] A composition was prepared by adding F particles 1, varnish 1, surfactant 1, and water to a pot and mixing them. This composition was kneaded in a planetary mixer and then removed to obtain a dough 1 containing F particles 1 (60 parts by mass), PAI 1 (0.6 parts by mass), surfactant 1 (3 parts by mass), and water (20 parts by mass). Water was added to the dough 1 in several batches while stirring at 2000 rpm with a planetary centrifugal mixer, degassing the mixture. Water was further added in several batches while stirring, and amine 1 was added to obtain dispersion 2 containing F particles 1 (60 parts by mass), PAI 1 (0.6 parts by mass), surfactant 1 (3 parts by mass), and water (46.4 parts by mass). The viscosity of the resulting dispersion 2 was 800 mPa s, and the pH was 8.0.

[0105] [Example 1-3]~[Example 1-6] Dispersions 3 to 6 were obtained in the same manner as in Example 1-2, except that the types or amounts of F particles, varnish, pH adjuster, and water were changed as shown in Table 1.

[0106] [Example 1-7] A composition was prepared by adding F particles 1, varnish 1, surfactant 1, and water to a pot and mixing them. This composition was kneaded in a planetary mixer and then removed to obtain dough 7 containing F particles 1 (50 parts by mass), PAI (0.6 parts by mass), surfactant 1 (3 parts by mass), and water (20 parts by mass). F Dispersion 1 was added to dough 7, and water was added in several batches while stirring at 2000 rpm with a planetary centrifugal mixer, degassing. Water was then added in several batches while stirring, and amine 1 was added to obtain Dispersion 7, which contained F Particles 1 (50 parts by mass), F Particles 3 (10 parts by mass), PAI 1 (0.6 parts by mass), Surfactant 1 (3 parts by mass), and water (46.4 parts by mass). The viscosity of the resulting Dispersion 7 was 700 mPa s, and the pH was 8.0.

[0107] [Example 1-8] A composition was prepared by adding F particles 1, varnish 1, surfactant 1, polysaccharide 1, and water to a pot and mixing them. This composition was kneaded in a planetary mixer and then removed to obtain dough 8 containing F particles 1 (50 parts by mass), PAI (0.6 parts by mass), surfactant 1 (3 parts by mass), polysaccharide 1 (0.3 parts by mass), and water (20 parts by mass). F Dispersion 1 was added to dough 8, and water was added in several batches while stirring at 2000 rpm with a planetary centrifugal mixer, degassing the mixture. Water was then added in several batches while stirring, and amine 1 was added to obtain Dispersion 8, which contained F Particles 1 (50 parts by mass), F Particles 3 (10 parts by mass), PAI 1 (0.6 parts by mass), Surfactant 1 (3 parts by mass), Polysaccharide 1 (0.3 parts by mass), and water (46.1 parts by mass). The viscosity of the resulting Dispersion 8 was 3000 mPa s, and the pH was 8.0.

[0108] [Table 1]

[0109] 3. Manufacture and evaluation of laminates [Example 2-1] Dispersion 1 obtained in Example 1-1 was applied to one side of polyimide film 1 by a roll-to-roll process using a small-diameter gravure reverse method, and the film was passed through a ventilation drying oven (oven temperature: 150°C) for 3 minutes to remove water and form a dry film. Dispersion 1 was also applied to the other side of polyimide film 1 in the same manner, and the film was dried to form a dry film. Next, the polyimide film 1 with the dry coating formed on both sides was passed through a far-infrared furnace (furnace temperature 300°C near the entrance and exit, 360°C near the center) for 5 minutes to melt and bake the F particles 1. As a result, polymer layers containing the fused and baked product of F particles 1 and PAI 1 were formed on both sides of polyimide film 1, and a laminate (multilayer film 1) in which a polymer layer, a polyimide film layer, and a polymer layer were directly formed in this order was obtained by a roll-to-roll process. The thickness of the polymer layer in multilayer film 1 was 25 μm.

[0110] [Example 2-2]~[Example 2-8] Multilayer films 2 to 7 were obtained in the same manner as in Example 2-1, except that dispersions 2 to 8 were used instead of dispersion 1. The porosity of the polymer layer of each multilayer film decreased in the order of multilayer film 2, multilayer film 1, multilayer films 3 and 4, and multilayer films 5 and 6, with the polymer layer of multilayer film 2 being the densest.

[0111] 4. Evaluation 4-1. Evaluation of dispersion layer ratio of dispersion liquid Each dispersion (18 mL) was placed in a screw tube (internal volume: 30 mL) and allowed to stand for 14 days at 25° C. After standing, the dispersion layer ratio was calculated from the height of the entire dispersion in the screw tube and the height of the sedimentation layer (dispersion layer) using the following formula, and the dispersion stability was evaluated according to the following criteria. [Evaluation criteria] ○: The dispersion layer rate is 80% or more. △: The dispersion layer rate is 60% or more and less than 80%. ×: The dispersion layer rate is less than 60%.

[0112] 4-2. Variation range of thixotropy ratio of dispersion liquid Each dispersion was stored in a container at 25°C for 30 days, and the range of change in the thixotropy ratio before and after storage was measured, and the thixotropy stability was evaluated according to the following criteria. [Evaluation criteria] ○: The fluctuation range (absolute value) of the thixotropy ratio is less than 1 △: The fluctuation range (absolute value) of the thixotropy ratio is 1 or more and 3 or less ×: The fluctuation range (absolute value) of the thixotropy ratio is more than 3

[0113] 4-3. Evaluation of surface smoothness of multilayer films The surface of the polymer layer of each multilayer film was visually inspected and the surface smoothness was evaluated according to the following criteria. [Evaluation criteria] ◯: No pinholes on the surface of the polymer layer. ×: Pinholes are present on the surface of the polymer layer.

[0114] 4-4. Evaluation of interlayer adhesion in multilayer films A rectangular test piece (100 mm long, 10 mm wide) was cut from each multilayer film, and the test piece was fixed at a position 50 mm from one end in the longitudinal direction. The polymer layer and the polyimide film layer were peeled from one end in the longitudinal direction at a 90° angle to the test piece at a pulling rate of 50 mm / min. The maximum load applied at this time was taken as the peel strength, and the interlayer adhesion was evaluated according to the following criteria. [Evaluation criteria] ◯: Peel strength is 15 N / cm or more. △: Peel strength is 10 N / cm or more and less than 15 N / cm. ×: The peel strength is less than 10 N / cm. The evaluation results are summarized in Table 2 below.

[0115] [Table 2]

[0116] The dielectric loss tangent of each multilayer film was measured by the SPDR (split post dielectric resonance) method (measurement frequency: 10 GHz), and the dielectric loss tangent of multilayer films 7 and 8 was the lowest, indicating that both multilayer films had superior electrical properties. Furthermore, the thickness of the polymer layer with surface smoothness and interlayer adhesion that could be formed in a single laminate manufacturing process was greatest when dispersion 8 was used. [Industrial Applicability]

[0117] The aqueous dispersion of the present invention has excellent dispersion stability and can be easily processed into films, fiber-reinforced films, prepregs, and metal laminates (resin-coated metal foils). The resulting processed articles can be used as materials for antenna components, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, sliding bearings, and the like. Furthermore, the laminate of the present invention has excellent heat resistance and releasability, and can therefore also be used as a carrier film for molding ceramic green sheets, a carrier film for forming secondary battery electrode films, a carrier film for forming solid polymer electrolyte membranes, and a carrier film for forming catalysts for solid polymer electrolyte membranes.

Claims

1. An aqueous dispersion comprising particles of a tetrafluoroethylene-based polymer, an aromatic imide-based resin having an acid value of 20 to 100 mg / KOH, and water, the aqueous dispersion having a pH of 5 to 10, a ratio of the mass of the aromatic imide-based resin to the mass of the tetrafluoroethylene-based polymer particles being in the range of 0.001 to 0.1, and a total content of the particles and the aromatic imide-based resin being 30 to 80 mass% based on the total mass.

2. 2. The aqueous dispersion of claim 1, wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer having oxygen-containing polar groups that include units based on perfluoro(alkyl vinyl ether).

3. 3. The aqueous dispersion according to claim 1, wherein the tetrafluoroethylene-based polymer particles comprise particles of a non-thermofusible tetrafluoroethylene-based polymer and particles of a thermofusible tetrafluoroethylene-based polymer.

4. The aqueous dispersion according to any one of claims 1 to 3, wherein the aromatic imide resin is a precursor of a water-soluble aromatic polyamideimide or a precursor of a water-soluble aromatic polyimide.

5. The aqueous dispersion according to any one of claims 1 to 4, further comprising an inorganic filler.

6. The aqueous dispersion according to any one of claims 1 to 5, further comprising a nonionic surfactant.

7. 7. The aqueous dispersion according to claim 1, further comprising at least one nonionic polymer selected from the group consisting of polyvinyl alcohol-based polymers, polyvinylpyrrolidone-based polymers, and polysaccharides.

8. The aqueous dispersion according to any one of claims 1 to 7, comprising an amine or ammonia.

9. The aqueous dispersion according to any one of claims 1 to 8, having a viscosity of 50 to 3000 mPa·s.

10. The aqueous dispersion according to any one of claims 1 to 9, which is used to form a polymer layer containing a tetrafluoroethylene-based polymer by applying it to at least one surface of a resin film and heating it.

11. The aqueous dispersion according to claim 10 , wherein the resin constituting the resin film is a polyimide resin.

12. The method for producing the aqueous dispersion according to any one of claims 1 to 11, comprising kneading a composition containing particles of the tetrafluoroethylene-based polymer, the aromatic imide-based resin, and water to obtain a kneaded mixture, and mixing the kneaded mixture with water to obtain the aqueous dispersion.

13. 12. A laminate having a base layer made of a resin film and a polymer layer containing a tetrafluoroethylene-based polymer on both sides thereof, the laminate comprising the resin film and the base layer being formed by applying the aqueous dispersion according to claim 10 or 11 to both surfaces of the resin film and heating the applied polymer layer.

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