Method for manufacturing a viscoelastic body and viscoelastic body

Abstract

[Problem] To provide: a method for manufacturing a viscoelastic body including particles of a tetrafluoroethylene-based polymer and having excellent physical properties such as dispersibility and homogeneity; a method for manufacturing a dispersion solution that is obtained from said viscoelastic body and that has excellent liquid physical properties such as dispersion stability, homogeneity, rheology, coatability, and storage stability; and such a viscoelastic body. [Solution] This viscoelastic body manufacturing method comprises: dry-disintegrating a powder of a thermomeltable tetrafluoroethylene-based polymer to obtain particles of the tetrafluoroethylene-based polymer; wet-mixing the particles with a liquid composition containing an organic resin and / or inorganic particles to obtain a viscoelastic body containing the particles and the organic resin and / or the inorganic particles.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a viscoelastic material containing particles of a heat-meltable tetrafluoroethylene polymer, and to the viscoelastic material itself. The present invention also relates to a method for producing a dispersion using the viscoelastic material. [Background technology]

[0002] Tetrafluoroethylene polymers such as polytetrafluoroethylene (hereinafter also referred to as "PTFE") have excellent physical properties such as electrical properties, water and oil repellency, chemical resistance, and heat resistance, and are used in various industrial applications such as printed circuit boards. Dispersions containing particles of tetrafluoroethylene polymers are known as coating agents used to impart these physical properties to the surface of a substrate. In recent years, the frequency of signals has increased, requiring materials with electrical properties such as low dielectric constant and low dielectric loss tangent, and excellent insulating performance. Therefore, dispersions containing tetrafluoroethylene polymer particles are attracting attention as materials that have excellent electrical properties such as low dielectric constant and low dielectric loss tangent, and that form dielectric layers for printed circuit boards that can handle high-frequency bands. Patent Document 1 describes a dispersion of resist ink containing tetrafluoroethylene polymer particles. Patent Document 2 discloses a dispersion containing PTFE particles and a ceramic inorganic filler. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-90923 [Patent Document 2] Japanese Patent Publication No. 2016-194017 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Due to their low surface tension, tetrafluoroethylene polymers have extremely low affinity for other components. Therefore, dispersions containing tetrafluoroethylene polymer particles along with other resins and inorganic fillers suffer from problems such as thickening and particle aggregation. The dispersions described in Patent Documents 1 and 2 still do not exhibit satisfactory liquid properties. As a result of diligent research, the present inventors have found that by dry crushing a heat-meltable tetrafluoroethylene polymer powder and wet mixing it with a liquid composition containing organic resin or inorganic particles, a viscoelastic material with excellent physical properties such as dispersibility and uniformity can be obtained. Furthermore, a dispersion with excellent liquid properties such as dispersion stability, uniformity, viscosity, thixotropy, rheology, coating properties, and storage stability can be obtained from such a viscoelastic material. The object of the present invention is to provide a method for producing a viscoelastic body containing tetrafluoroethylene polymer particles and having excellent physical properties such as dispersibility and uniformity, a method for producing a dispersion obtained from such a viscoelastic body that has excellent liquid properties such as dispersion stability, uniformity, rheology, coating properties, and storage stability, and such a viscoelastic body. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A method for producing a viscoelastic body, comprising: dry crushing a powder of a heat-meltable tetrafluoroethylene polymer to obtain particles of the tetrafluoroethylene polymer; and wet mixing the particles with at least one of an organic resin and inorganic particles in the presence of a liquid substance to obtain a viscoelastic body containing the particles and at least one of the organic resin and inorganic particles. [2] The manufacturing method according to [1], wherein the dry crushing is carried out using at least one mixer selected from the group consisting of a Henschel mixer, a pressure kneader, a Banbury mixer, a rotational mixer, a planetary mixer, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, a spike mill, an agitator mill, a microfluidizer, a nanomizer, an ultimateizer, a dissolver, a disper, and a high-speed impeller. [3] The manufacturing method according to [1] or [2], wherein the dry crushing is carried out at a temperature below the glass transition temperature of the tetrafluoroethylene polymer. [4] The manufacturing method according to any one of [1] to [3], wherein the wet mixing is carried out using at least one mixer selected from the group consisting of a Henschel mixer, a pressurized kneader, a Banbury mixer, a rotational mixer, a planetary mixer, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, a spike mill, an agitator mill, a microfluidizer, a nanomizer, an ultimateizer, an ultrasonic homogenizer, a dissolver, a disper, a high-speed impeller, and a thin-film swirling high-speed mixer. [5] The manufacturing method according to any one of [1] to [4], wherein the wet mixing is carried out at a temperature above the glass transition temperature of the tetrafluoroethylene polymer. [6] The manufacturing method according to any one of [1] to [5], wherein the glass transition temperature of the tetrafluoroethylene polymer is 60 to 150°C. [7] The manufacturing method according to any one of [1] to [6] above, wherein the organic resin is a thermosetting resin. [8] The manufacturing method according to any one of [1] to [7], wherein the organic resin is at least one aromatic resin selected from the group consisting of aromatic epoxy resins, phenolic resins, aromatic polyimide resins, precursors of aromatic polyimide resins, aromatic polyamideimide resins, and precursors of aromatic polyamideimide resins. [9] The manufacturing method according to any one of [1] to [8], wherein the wet mixing is performed by wet mixing the particles and the inorganic particles in the presence of a liquid substance, and then wet mixing the organic resin.

[10] The manufacturing method according to any one of [1] to [9], wherein the wet mixing is performed by wet mixing the particles with a liquid composition containing at least one of an organic resin and inorganic particles.

[11] The manufacturing method according to

[10] , wherein the liquid composition contains at least an organic resin, the ratio of the mass of the organic resin to the mass of the tetrafluoroethylene polymer in the wet mixing is 0.1 or more, and the total content of the tetrafluoroethylene polymer and the organic resin in the viscoelastic body is 40% by mass or more.

[12] A method for producing a viscoelastic body, comprising: dry crushing a powder of a heat-meltable tetrafluoroethylene polymer to obtain particles of the tetrafluoroethylene polymer; and wet mixing the particles with a thermosetting resin varnish, such that the ratio of the mass of the thermosetting resin to the mass of the tetrafluoroethylene polymer is 0.1 or more, to obtain a viscoelastic body containing the particles and the thermosetting resin.

[13] A method for producing a dispersion, comprising further diluting a viscoelastic body obtained by the manufacturing method described in any of [1] to

[12] above with water or a non-aqueous solvent to obtain a dispersion with a viscosity of 10,000 mPa·s or less.

[14] A method for producing a dispersion, comprising further mixing a viscoelastic body obtained by any of the manufacturing methods described in [1] to

[12] above with an organic resin or inorganic particles to obtain a dispersion.

[15] A viscoelastic body comprising particles of a heat-meltable tetrafluoroethylene polymer and a thermosetting resin, wherein the ratio of the mass of the thermosetting resin to the mass of the tetrafluoroethylene polymer is 0.1 or more, and the total content of the tetrafluoroethylene polymer and the thermosetting resin is 40% by mass or more. [Effects of the Invention]

[0006] The present invention provides a method for producing a viscoelastic body containing particles of a heat-meltable tetrafluoroethylene polymer and at least one of an organic resin and inorganic particles, and a dispersion liquid formed from such a viscoelastic body that has excellent liquid properties such as dispersibility. Furthermore, the present invention provides a viscoelastic body containing particles of a heat-meltable tetrafluoroethylene polymer and at least one of an organic resin and inorganic particles in a predetermined ratio.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] The following terms have the following meanings. The "thermally fusible tetrafluoroethylene-based polymer" is a polymer containing units based on tetrafluoroethylene (hereinafter also referred to as "TFE"), and means a polymer having melt fluidity such that there is a temperature at which the melt flow rate is from 1 to 1000 g / 10 min under the condition of a load of 49 N. The "glass transition point (Tg) of the polymer" is a value measured by analyzing the polymer by the dynamic viscoelasticity measurement (DMA) method. The "melting temperature (melting point) of the polymer" is the temperature corresponding to the maximum value of the melting peak measured by the differential scanning calorimetry (DSC) method. "D50" is the average particle diameter of the particles, and is the volume-based cumulative 50% diameter of the particles determined by the laser diffraction / scattering method. That is, the particle size distribution of the particles is measured by the laser diffraction / scattering method, a cumulative curve is obtained with the total volume of the particle population as 100%, and it is the particle diameter at the point where the cumulative volume becomes 50% on the cumulative curve. "D90" is the cumulative volume particle diameter of the particles, and is the volume-based cumulative 90% diameter of the particles determined in the same manner as "D50". "Viscosity" is a value measured for the dispersion at room temperature (25 °C) under the condition of a rotation speed of 30 rpm using a B-type viscometer, unless otherwise specified. The measurement is repeated 3 times, and the average value of the 3 measurement values is taken. The "thixotropy ratio" is a value calculated by dividing the viscosity obtained by measuring the dispersion under the condition of a rotation speed of 30 rpm by the viscosity obtained by measuring under the condition of a rotation speed of 60 rpm. The "unit based on the monomer" means an atomic group based on the monomer formed by the polymerization of the monomer. The unit may be a unit directly formed by the polymerization reaction, or may be a unit in which a part of the unit is converted to another structure by treating the polymer. Hereinafter, the unit based on monomer a is also simply referred to as "monomer a unit".

[0008] The manufacturing method of the present invention (hereinafter also referred to as "this method") is to dry-crush the powder of a heat-meltable tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") to obtain particles of the F polymer (hereinafter also referred to as "F particles"), and in the presence of a liquid substance, wet-mix the F particles with at least one of an organic resin and inorganic particles to obtain a viscoelastic body (hereinafter also referred to as "this viscoelastic body") containing the F particles and at least one of the organic resin and inorganic particles. This viscoelastic body is excellent in dispersibility and uniformity, and a dispersion liquid excellent in liquid physical properties such as dispersion stability can be obtained from this viscoelastic body. The reason is not necessarily clear, but it is presumed as follows, for example.

[0009] Since tetrafluoroethylene-based polymers have a low surface tension and are prone to fibrillation, their particles are prone to aggregation or adhesion, and are in a state where they are prone to deterioration themselves. Therefore, when mixing with other materials such as organic resins and inorganic particles while dispersing the particles in a liquid, aggregation and deterioration of the particles of the tetrafluoroethylene-based polymer are induced, and it is difficult to obtain a dispersion liquid having sufficient liquid physical properties. In this method, first, the powder, which can also be said to be an aggregate of F particles, is dry-crushed. Since the F polymer is heat-meltable and excellent in shape stability such as fibril resistance, the powder of the F polymer is highly crushed while suppressing deterioration. That is, by dry-crushing, the powder of the F polymer becomes F particles in a state close to an aggregate of primary particles in which aggregation and adhesion are eliminated. When such F particles and at least one of an organic resin and inorganic particles are wet-mixed in the presence of a liquid substance, the fine F particles and the organic resin or inorganic particles are more likely to interact. And it is considered that making the mixture into a viscoelastic body by wet-mixing enhances this interaction and promotes the formation of a composite in which the surface of the F particles is coated with an organic resin or inorganic particles, or a composition in which one material is highly dispersed in the other material. Due to such an action mechanism, it is considered that this viscoelastic body is excellent in dispersibility and uniformity, and thus a dispersion liquid excellent in liquid physical properties such as dispersion stability can be obtained from it.

[0010] The melting temperature of the F polymer is preferably 200°C or higher, and more preferably 260°C or higher. The melting temperature of the F polymer is preferably 325°C or lower, and more preferably 320°C or lower. The glass transition temperature of the F polymer is preferably 60°C or higher, and more preferably 75°C or higher. The glass transition temperature of the F polymer is preferably 150°C or lower, and more preferably 125°C or lower. If the glass transition temperature of the F polymer is within this range, the F polymer tends to exhibit excellent shape stability, and the affinity between the F polymer and the organic resin or inorganic particles described later tends to improve, resulting in a viscoelastic material and a dispersion of the F polymer that tend to exhibit excellent dispersibility. The fluorine content of the F polymer is preferably 70% by mass or more, and more preferably 72 to 76% by mass. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of wetting index reagent (manufactured by Wako Pure Chemical Industries, Ltd.) on a flat plate made of the F polymer.

[0011] The F polymer is preferably PTFE, a polymer containing TFE units and ethylene-based units, a polymer containing TFE units and propylene-based units, a polymer containing TFE units and perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE")-based units (hereinafter also referred to as "PAVE units") (hereinafter also referred to as "PFA"), or a polymer containing TFE units and hexafluoropropylene-based units (hereinafter also referred to as "FEP"), with PFA and FEP being more preferred, and PFA being even more preferred. These polymers may further contain units based on other comonomers. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, and CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), with PPVE being more preferred.

[0012] The F polymer preferably has an oxygen-containing polar group, more preferably a hydroxyl group-containing group or a carbonyl group-containing group, and even more preferably a carbonyl group-containing group. When the F polymer has such a functional group, the affinity between the F polymer and the organic resin or inorganic particles described later, and the dispersion stability of the F particles tend to improve. In addition, molded products formed from this viscoelastic material tend to have excellent adhesion. The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, and -CF2CH2OH and -C(CF3)2OH are more preferred. The carbonyl group-containing groups are preferably carboxyl groups, alkoxycarbonyl groups, amide groups, isocyanate groups, carbamate groups (-OC(O)NH2), acid anhydride residues (-C(O)OC(O)-), imide residues (-C(O)NHC(O)-, etc.), and carbonate groups (-OC(O)O-), with acid anhydride residues being more preferred.

[0013] If the F polymer has oxygen-containing polar groups, the number of oxygen-containing polar groups in the F polymer is 1 × 10⁶ carbon atoms in the main chain. 6 The number of oxygen-containing polar groups per polymer is preferably 10 to 5000, and more preferably 100 to 3000. The number of oxygen-containing polar groups in polymer F can be quantified by the polymer composition or by the method described in International Publication No. 2020 / 145133. The oxygen-containing polar group may be included in the monomer-based units in the F polymer, or it may be included in the terminal groups of the main chain of the F polymer, with the former being preferred. 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 obtained by plasma treatment or ionization treatment of the F polymer.

[0014] The monomers having a carbonyl group are preferably itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic acid anhydride (hereinafter also referred to as "NAH"), with NAH being more preferred. The F polymer is preferably a polymer having carbonyl group-containing groups, including TFE units and PAVE units, and more preferably a polymer containing TFE units, PAVE units, and units based on monomers having carbonyl group-containing groups, with these units present in the following proportions of 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol% relative to the total number of units. A specific example of such an F polymer is the polymer described in International Publication No. 2018 / 16644.

[0015] F polymer powder is an aggregate of F particles. As mentioned above, F particles tend to aggregate, so F polymer powder usually exists as aggregates of F particles. The average particle size D50 of the F particles constituting the F polymer powder is preferably 0.1 μm or more, more preferably greater than 0.3 μm, and even more preferably 1 μm or more. The D50 of the F particles is preferably 25 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The specific surface area of ​​the F particles constituting the F polymer powder ranges from 1 to 25 m². 2 / g is preferable.

[0016] The F polymer powder may consist of one type of F particle or two or more types of F particles. The F polymer powder may also be dry-crushed in a mixture containing particles of other resins or inorganic particles. Examples of other resins include particles of resins similar to those of the organic resins described later, or inorganic particles similar to those of the inorganic particles described later. PTFE particles are preferred as the particles of the other resins. Such particles may be included as a powder aggregate of particles, in which case the F polymer powder and PTFE powder can be crushed while suppressing the modification of the PTFE particles. When F particles and PTFE particles are included, the proportion of the former particles in the mixture is preferably 50% by mass or less, more preferably 25% by mass or less. Furthermore, the aforementioned proportion is preferably 5% by mass or more, and more preferably 10% by mass or more. In this case, it is preferable that the D50 of the F particles is 1 to 4 μm, and the D50 of the PTFE particles is 0.1 to 1 μm.

[0017] F particles are particles containing F polymer, and it is preferable that they consist of F polymer. The F particles may contain resins or inorganic compounds other than the F polymer, and may form a core-shell structure with the F polymer as the core and a resin or inorganic compound other than the F polymer as the shell, or may form a core-shell structure with the F polymer as the shell and a resin or inorganic compound other than the F polymer as the core.

[0018] Examples of resins other than F polymers include aromatic polyesters, polyamide-imides, polyimides, and maleimides. Examples of inorganic compounds include silica and boron nitride.

[0019] As described above, the powder of the F polymer, which is an aggregate of F particles, is dry-crushed to obtain F particles that are close to an aggregate of primary particles. Dry crushing should be performed without adding any liquid substance such as a solvent, so as to crush the aggregate of F particles and eliminate aggregation or sticking of the F particles. The shear force applied to the powder of the F polymer during dry crushing should be applied so that the powder of the F polymer is crushed and returned to the state of individual particles.

[0020] Examples of equipment used to achieve the aforementioned dry crushing include at least one mixer selected from the group consisting of Henschel mixers, pressure kneaders, Banbury mixers, rotational mixers, planetary mixers, ball mills, attritors, basket mills, sand mills, sand grinders, dyno mills, disper mats, SC mills, spike mills, agitator mills, microfluidizers, nanomizers, ultimateizers, dissolvers, dispersers, and high-speed impellers. By using these mixers, the powder of the F polymer is highly crushed into fine F particles while suppressing the alteration of the F polymer. Dry crushing may be carried out using one type of mixer or multiple types of mixers. When multiple types of mixers are used, dry crushing may be carried out by sequentially using different types of mixers, or the powder may be divided into multiple parts, each of which may be dry crushed in a different mixer, and then combined into one. Among these mixers, the rotational / orbital mixer is preferred.

[0021] Dry crushing may be performed at room temperature or while heating or cooling, but it is preferable to perform it at a temperature below the glass transition temperature of the F polymer. By performing dry crushing at a temperature below the glass transition temperature of the F polymer, the softening of the F polymer can be suppressed while maintaining the rigidity of the F particles, thus the F polymer is less likely to denature and the shape of the F particles can be maintained during crushing. The process is usually carried out at a temperature of 10°C or higher, and does not need to be constant. Due to heat generation from shearing, the temperature may rise, or dry crushing may be performed at a constant temperature while cooling to suppress the temperature rise. Heating may also be used if necessary. Dry crushing is preferably carried out at a temperature 20°C or lower than the glass transition temperature of the F polymer, and more preferably at a temperature 30°C or lower than the glass transition temperature of the F polymer.

[0022] The dry crushing time is preferably 5 minutes or more, and more preferably 10 minutes or more. The end of the dry crushing should be when the F polymer powder becomes individual F particles, which is usually 20 hours or less.

[0023] Under the aforementioned conditions, the F polymer powder is dry-crushed to form F particles. The D50 and specific surface area of ​​the F particles after dry crushing may be the same as those of the F particles constituting the F polymer powder, but they may also be finer, and the specific surface area may change. The D50 of the F particles after dry crushing is preferably 0.1 μm or more, more preferably greater than 0.3 μm, and even more preferably 1 μm or more. The D50 of the F particles after dry crushing is preferably 25 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The specific surface area of ​​the F particles after dry crushing is 1 to 25 μm. 2 / g is preferable. Except for D50 and specific surface area after dry crushing, the F particles that make up the F polymer powder are the same.

[0024] In this method, the F particles after dry crushing are wet-mixed with at least one of an organic resin and inorganic particles in the presence of a liquid substance. The liquid component is a component that is liquid at 25°C, and examples include solvents described later. If the organic resin described later is liquid at 25°C, such organic resin may be used as the liquid substance in the wet mixing. In wet mixing in the presence of a liquid substance, it is preferable to use a liquid composition having at least one of an organic resin and inorganic particles (hereinafter also referred to as the "mixed component") from the viewpoint of interaction between the F particles and the organic resin or inorganic particles.

[0025] In wet mixing, a liquid composition containing the mixed components may be prepared in advance and mixed with the F particles, or the F particles may be mixed with the mixed components and the solvent. The liquid composition may be any of the following: a composition containing a liquid organic resin as described above, a composition containing the mixed components and the solvent, or a composition containing a liquid organic resin as described above and the solvent. The mixed components may be either an organic resin or an inorganic resin, or both.

[0026] The organic resin (hereinafter also referred to as "this organic resin"), which is one of the aforementioned mixed components, is a different resin from F polymer. The organic resin may be thermosetting, photocurable, or thermoplastic, but a thermosetting resin is preferred. When the organic resin is a thermosetting resin, during wet mixing, the thermosetting resin partially hardens and thickens due to the heat generated during mixing, and is mixed with the F particles. As a result, the surface of the F particles is effectively covered with the thermosetting resin and is easily stabilized, making it easier to obtain the viscoelastic material and the dispersion described later, which have excellent uniformity and dispersibility. Furthermore, by performing wet mixing above the glass transition temperature of the F polymer, the F polymer can be softened while the thermosetting resin can be partially cured. This allows for a high degree of interaction between the F particles and the thermosetting resin, making it easier to obtain this viscoelastic material with excellent uniformity and dispersibility.

[0027] Examples of organic resins include polyester resins such as liquid crystalline aromatic polyesters and polyarylate resins, amide resins, imide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, polyphenylene sulfide resins, polyolefin resins, polycarbonate resins, polyacetal resins, aromatic resins, and fluororesins other than F polymers. Aromatic resins are preferred as the organic resin. When the organic resin is an aromatic resin, it readily interacts with the F polymer, resulting in a viscoelastic material that exhibits excellent uniformity and dispersibility. Furthermore, molded products formed from this viscoelastic material tend to have excellent adhesion and UV absorption properties. Examples of aromatic resins include aromatic epoxy resins, phenolic resins, aromatic polyimide resins, precursors of aromatic polyimide resins, aromatic polyamideimide resins, and precursors of aromatic polyamideimide resins. Preferably, at least one aromatic resin selected from the group consisting of aromatic epoxy resins, phenolic resins, aromatic polyimide resins, precursors of aromatic polyimide resins, aromatic polyamideimide resins, and aromatic polyamideimide resins is used.

[0028] Examples of aromatic epoxy resins include biphenyl novolac type epoxy resins, phenol novolac type epoxy resins, o-cresol novolac type epoxy resins, novolac type epoxy resins such as p-tert-butylphenol novolac type, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins, trisphenol type epoxy resins, tert-butylcatechol type epoxy resins, aminophenol type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, and phenyl aralkyl type epoxy resins. These epoxy resins may be solid, semi-solid, or liquid. The term "solid" refers to a state of solidity at 40°C, "semi-solid" refers to a state of solidity at 20°C and liquidity at 40°C, and "liquid" refers to a state of liquidity at 20°C.

[0029] Examples of phenolic resins include phenol novolac resins, alkyl phenol volac resins, bisphenol A novolac resins, dicyclopentadiene type phenolic resins, Xylok type phenolic resins, terpene-modified phenolic resins, cresol resins or naphthol resins, polyvinylphenol resins, α-naphthol skeleton-containing phenolic resins, triazine skeleton-containing cresol novolac resins, biphenyl aralkyl type phenolic resins, and Xylok type phenol novolac resins. These phenolic resins may also be used in combination as curing agents for thermosetting resins such as aromatic epoxy resins.

[0030] Examples of precursors for aromatic polyimide resins include polyamic acids and their salts, which are obtained by polymerizing tetracarboxylic dianhydrides and diamines. Aromatic polyamide-imide resins or their precursors include polyamide-imide resins or their precursors obtained by reacting at least one of diisocyanate or diamine with a tribasic acid anhydride. Examples of tetracarboxylic dianhydrides include pyromellitic anhydride and biphenyltetracarboxylic anhydride. Examples of diamines include phenylenediamine, 3,3'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl ether. Examples of diisocyanates include 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, and 3,3'-diphenylmethane diisocyanate. Specific examples of aromatic polyimide resins, aromatic polyamide resins, or their precursors include the "Yupia-AT" series (manufactured by Ube Industries, Ltd.), the "Neoprim®" series (manufactured by Mitsubishi Gas Chemical Company, Ltd.), the "Spixeria®" series (manufactured by Somar Corporation), the "Q-PILON®" series (manufactured by PI Technical Research Institute, Ltd.), the "WINGO" series (manufactured by Wingo Technology Co., Ltd.), the "Tomide®" series (manufactured by T&K TOKA Corporation), the "KPI-MX" series (manufactured by Kawamura Industries Co., Ltd.), and "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.).

[0031] Furthermore, the aromatic resin may be a modified aromatic resin having a carboxyl group and an ethylenically unsaturated double bond derived from a (meth)acryloyloxy group in its molecule. In this specification, (meth)acryloyloxy group is a general term referring to acryloyloxy group, methacryloyloxy group, and both. Such modified aromatic resins are photosensitive resins with good photocurability and developability, and are alkali-soluble resins. Carboxyl group-containing phenolic resins are preferred as modified aromatic resins, and carboxyl group-containing phenolic resins are more preferred, which are obtained by reacting a polyfunctional phenolic resin such as a polyfunctional novolac-type epoxy resin with (meth)acrylic acid, and then adding an organic polybasic acid anhydride to the hydroxyl groups present in the side chain.

[0032] The number-average molecular weight (Mn) of the aromatic resin is preferably between 5,000 and 50,000, and the acid value of the aromatic resin is preferably between 20 and 100 mg / KOH. The acid value of the aromatic resin is determined by titrating a mixed solution of 0.5 g of the aromatic resin, 0.15 g of 1,4-diazabicyclo[2.2.2]octane, 60 g of N-methyl-2-pyrrolidone, and 1 mL of deionized water using a potentiometric titrator with a 0.05 mol / L ethanolic potassium hydroxide solution. If the aromatic resin has an acid anhydride group, the acid value obtained when the acid anhydride group is ring-opened is used as the acid value of the aromatic resin.

[0033] The organic resin may be a cyanate ester resin. Examples of cyanate ester resins include phenol novolac type cyanate ester resin, alkylphenol novolac type cyanate ester resin, dicyclopentadiene type cyanate ester resin, bisphenol A type cyanate ester resin, bisphenol F type cyanate ester resin, and bisphenol S type cyanate ester resin. It may also be a prepolymer that is partially triazined. These cyanate ester resins may be used in combination as curing agents for thermosetting resins such as the aromatic epoxy resin.

[0034] The organic resin may be a non-thermally fused tetrafluoroethylene polymer, and is preferably PTFE. The PTFE is preferably in particulate form, and more preferably in particulate form with a D50 of 0.1 to 1 μm. When the organic resin is PTFE, it is preferable to use an aqueous dispersion of PTFE particles, and more preferably to use a liquid composition containing an aqueous dispersion of PTFE particles.

[0035] The organic resin comprising this organic resin may be one type or two or more types. If this organic resin includes a thermosetting resin, this organic resin may be used in combination with an organic resin that functions as a curing agent for the thermosetting resin.

[0036] If one of the aforementioned mixed components is the organic resin, its content is preferably 10% by mass or more, and more preferably 20% by mass or more, with the total mass including the liquid substance, the organic resin, and, if present, the inorganic particles, being 100% by mass. Its content is preferably 80% by mass or less, and more preferably 60% by mass or less.

[0037] The inorganic particles (hereinafter also referred to as "the inorganic particles"), which are one of the aforementioned mixed components, are preferably spherical, needle-shaped, fibrous, or plate-shaped, preferably spherical, flaky, or layered, and more preferably spherical or flaky. The inorganic particles, which are spherical, are preferably nearly spherical. Nearly spherical means that, when the inorganic particles are observed using a scanning electron microscope (SEM), 95% or more of them have a ratio of minor axis to major axis of 0.7 or greater. The aspect ratio of these non-spherical inorganic particles is preferably 2 or greater, and more preferably 5 or greater. An aspect ratio of 10000 or less is also preferred.

[0038] The inorganic particles are preferably carbon fillers, inorganic nitride fillers, or inorganic oxide fillers, more preferably carbon fiber fillers, boron nitride fillers, aluminum nitride fillers, beryllia fillers, silica fillers, wollastonite fillers, talc fillers, cerium oxide fillers, aluminum oxide fillers, magnesium oxide fillers, zinc oxide fillers, or titanium oxide fillers, and even more preferably boron nitride fillers or silica fillers. The D50 of these inorganic particles is preferably 20 μm or less, more preferably 10 μm or less. The D50 is preferably 0.01 μm or more, more preferably 0.1 μm or more. The specific surface area of ​​these inorganic particles ranges from 1 to 20 m². 2 / g is preferable.

[0039] The surface of these inorganic particles may be surface-treated with a silane coupling agent. The preferred silane coupling agent is one having a functional group such as 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, or 3-isocyanatetopropyltriethoxysilane.

[0040] Specific examples of silica fillers include the "AdmaFine" series (manufactured by Admatex Co., Ltd.), the "SFP" series (manufactured by Denka Co., Ltd.), and the "E-SPHERES" series (manufactured by Taiheiyo Cement Corporation). A specific example of zinc oxide filler is the "FINEX" series (manufactured by Sakai Chemical Industry Co., Ltd.). Specific examples of titanium dioxide fillers include the "Typeque" series (manufactured by Ishihara Sangyo Co., Ltd.) and the "JMT" series (manufactured by Teika Co., Ltd.). A concrete example of talc filler is the "SG" series (manufactured by Nippon Talc Co., Ltd.). A specific example of steatite filler is the "BST" series (manufactured by Nippon Talc Co., Ltd.). Specific examples of boron nitride fillers include the "UHP" series (manufactured by Showa Denko Corporation) and the "GP" and "HGP" grades of the "Denka Boron Nitride" series (manufactured by Denka Corporation). If one of the mixed components is the inorganic particles, the content thereof is preferably 10% by mass or more, and more preferably 20% by mass or more, with the total mass including the liquid substance, the inorganic particles, and the organic resin (if present) being 100% by mass. The content thereof is preferably 80% by mass or less, and more preferably 60% by mass or less.

[0041] It is preferable to use a liquid composition having at least one of the aforementioned organic resin and inorganic particles. A liquid state is defined as a state in which the viscosity is 10,000 mPa·s or less at 25°C, and may or may not contain a solvent. Examples of solvent-free liquid compositions include liquid compositions containing the organic resin in liquid form and without a solvent.

[0042] When a solvent is used as the liquid substance, the solvent is preferably a compound that is liquid at atmospheric pressure and 25°C, and has a boiling point of 50 to 240°C. One type of solvent may be used, or two or more types may be used. When two types of solvents are used, it is preferable that the two solvents are mutually compatible. The solvent may be either water or a non-aqueous solvent, and examples of non-aqueous solvents include amides, ketones, esters, (meth)acrylates, and glycol compounds. In this specification, (meth)acrylate is a general term encompassing acrylate, methacrylate, and both. When water or a non-aqueous solvent is used as the liquid substance, the F particles and the organic resin or inorganic particles can interact via the water or non-aqueous solvent, making it easier to obtain a viscoelastic material with excellent uniformity and dispersibility.

[0043] Examples of amides include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-diethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone. Ketones include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, and cycloheptanone. Examples of esters include methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, ethyl 3-ethoxypropionate, γ-butyrolactone, and γ-valerolactone.

[0044] The viscosity of the (meth)acrylate is preferably 1 to 1000 mPa·s, and more preferably 5 to 300 mPa·s. The molecular weight of the (meth)acrylate is preferably between 100 and 1000. The (meth)acrylate is preferably a polyfunctional (meth)acrylate or a mono(meth)acrylate having a hydroxyl group or an oxyalkylene group, and more preferably a polyfunctional (meth)acrylate. Preferred polyfunctional (meth)acrylates include glycol (meth)acrylate, alkylene glycol (meth)acrylate, glycerol (meth)acrylate, trimethylolpropane (meth)acrylate, ditrimethylolpropane (meth)acrylate, pentaerythritol (meth)acrylate, dipentaerythritol (meth)acrylate, erythritol (meth)acrylate, and dierythritol (meth)acrylate.

[0045] (Meth)acrylates are also available commercially. Specifically, these include "A-DPH" (dipentaerythritol polyacrylate, 7500 mPa·s (25℃)) and "A-9550" (dipentaerythritol polyacrylate, 6500 mPa·s (25℃)) manufactured by Shin Nakamura Kogyo Co., Ltd.<NKエステル> A series is one example.

[0046] Glycol compounds are preferably liquid at 25°C. Examples of glycol-based liquid compounds include glycols, glycol ethers, glycol esters, and glycol derivatives such as glycol amides. Suitable glycol-based liquid compounds include 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, tripropylene glycol monobutyl ether, propylene glycol monophenyl ether, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0047] Glycol-based liquid compounds are also available commercially. Specifically, these include "Tergitol TMN-100X" (manufactured by Dow Chemical), "Lutensol T08", "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 Emulsifier Co., Ltd.), "Leocol TDN-90-80" and "Leocol SC-90" (both manufactured by Lion Specialty Chemicals), and "Palmless NOB-25", "Palmless NOB-30", and "Palmless NOB-50" (all manufactured by Three Palmless P&A).

[0048] When the liquid composition contains the solvent, the F particles and the organic resin or inorganic particles can interact to a high degree through the solvent, making it easier to obtain a viscoelastic material with excellent uniformity and dispersibility.

[0049] The liquid substance or liquid composition may contain a nonionic surfactant. The nonionic surfactant is preferably a glycol-based surfactant, acetylene-based surfactant, silicone-based surfactant, or fluorine-based surfactant, with silicone-based surfactant being more preferred. One nonionic surfactant may be used, or two or more may be used. When two nonionic surfactants are used, it is preferable that the nonionic surfactants be a silicone-based surfactant and a glycol-based surfactant. Specific examples of nonionic surfactants include the "Futergent" series (manufactured by Neos Co., Ltd.), the "Surflon" series (manufactured by AGC Seimi Chemical Co., Ltd.), the "Megafac" series (manufactured by DIC Corporation), the "Unidyne" series (manufactured by Daikin Industries, Ltd.), "BYK-347", "BYK-349", "BYK-378", "BYK-3450", "BYK-3451", "BYK-3455", "BYK-3456" (manufactured by Bic Chemie Japan Co., Ltd.), and "KF-6011" and "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.). If the liquid substance or liquid composition contains a nonionic surfactant, the content of the nonionic surfactant is preferably 1 to 15% by mass.

[0050] Furthermore, when using the aforementioned thermosetting resin as a mixed component, the mixed component may also include a curing agent other than the resin. The curing agent is appropriately selected in combination with the thermosetting resin. If the F polymer has the carbonyl group-containing group, the curing agent may react with the F polymer in a thermosetting reaction. Examples of curing agents include amines, imidazoles, phenols, acid anhydrides, and compounds having a maleimide group. When using the thermosetting resin as a mixed component, it is preferable to select a curing agent such that the curing start temperature of the curable resin is between 120 and 200°C. The curing start temperature is determined by differential scanning calorimetry (DSC) and is the temperature at which the curable resin first exhibits exothermic reaction when heated.

[0051] Examples of amines include aliphatic polyamines such as alkylenediamines, polyalkylene polyamines, and aliphatic polyamines having aromatic rings, and their adduct compounds; alicyclic polyamines such as isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and laromine, and their adduct compounds. Specific examples of amines include the "Fujicure FXR" series (both manufactured by Fuji Chemical Industries Co., Ltd.), the "Ankamin" series and the "Sanmide" series (both manufactured by Air Products Co., Ltd.), jER Cure 113 (manufactured by Mitsubishi Chemical Corporation), and Laromin C-260 (manufactured by BASF).

[0052] Examples of imidazoles include 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, azine compounds of imidazole, isocyanurates of imidazole, hydroxymethyl imidazoles, or adduct compounds thereof.

[0053] Examples of phenols include hydroquinone, resorcinol, and bisphenol A. Examples of acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, and benzophenonetetracarboxylic acid.

[0054] Examples of compounds having a maleimide group include 4,4'-diphenylmethanebismaleimide, phenylmethanebismaleimide, m-phenylenebismaleimide, 3,3'-dimethyl-5,5'-dimethyl-4,4'-diphenylmethanebismaleimide, 4-methyl-1,3,-phenylenebismaleimide, (1,6-bismaleimide-2,2,4-trimethyl)hexane, their oligomers, and diamine condensates having a maleimide skeleton.

[0055] The viscoelastic material is obtained by wet mixing the F particles and the mixed components. The wet mixing is performed by applying shear to ensure that the F particles and the mixed components, which are the organic resin or inorganic particles, are uniformly mixed.

[0056] Examples of equipment used for wet mixing include the mixers exemplified in the dry grinding section. In addition to the mixers, ultrasonic homogenizers and thin-film swirling high-speed mixers can also be used for wet mixing. Wet mixing is preferably carried out using at least one mixer selected from the group consisting of Henschel mixers, pressure kneaders, Banbury mixers, rotational mixers, planetary mixers, ball mills, attritors, basket mills, sand mills, sand grinders, dyno mills, disper mats, SC mills, spike mills, agitator mills, microfluidizers, nanomizers, ultimateizers, ultrasonic homogenizers, desolvers, dispersers, high-speed impellers, and thin-film swirling high-speed mixers. Using these mixers is preferable because it allows for good mixing of F particles and organic resins or inorganic particles while suppressing the modification of the F polymer. Wet mixing may be performed using one type of mixer or multiple types of mixers. When multiple types of mixers are used, wet mixing may be performed using different types of mixers sequentially, or the mixtures may be wet-mixed in multiple separate batches using different mixers and then combined into one batch. Among these mixers, the rotational / orbital mixer is preferred.

[0057] Wet mixing may be carried out at room temperature or while heating or cooling, but it is preferable to carry it out at a temperature above the glass transition point of the F polymer. Wet mixing at a temperature above the glass transition point of the F polymer softens the F polymer, reducing the rigidity of the F particles, which increases interactions such as adhesion with organic resins or inorganic particles, resulting in a viscoelastic material that tends to have excellent dispersibility and uniformity. The mixing is usually carried out at a temperature of 10°C or higher, and does not need to be constant. Due to heat generation from shearing, the temperature may rise, or wet mixing may be performed at a constant temperature while cooling to suppress the temperature rise. Heating may also be used if necessary. Wet mixing is preferably carried out at a temperature above the glass transition temperature of the F polymer, and more preferably at a temperature of 10°C or higher above the glass transition temperature of the F polymer. Wet mixing is preferably carried out at a temperature of 120°C or lower, and more preferably at a temperature of 100°C or lower.

[0058] The wet mixing time is preferably 5 minutes or more, and more preferably 10 minutes or more. The end of wet mixing may be considered to be when the load on the mixer becomes constant, which is usually 20 hours or less. The surfactant or curing agent may be added during wet mixing.

[0059] When wet-mixing F particles, organic resin, and inorganic particles, it is preferable to wet-mix the F particles and inorganic particles first, and then wet-mix the organic resin. In this case, the viscosity increase and foaming of the viscoelastic material and the dispersion obtained therefrom are more easily suppressed.

[0060] The viscosity of this viscoelastic material, as measured by capillography, is preferably greater than 100 Pa·s, more preferably 1000 Pa·s or greater, and even more preferably 3000 Pa·s or greater. The viscosity of this viscoelastic material, as measured by capillography, is preferably 50000 Pa·s or less, more preferably 10000 Pa·s or less, and even more preferably 8000 Pa·s or less. Note that the viscosity measured by capillography is calculated using a capillary with a capillary length of 10 mm and a capillary radius of 1 mm, with a furnace diameter of 9.55 mm, a load cell capacity of 2 t, a temperature of 25°C, and a shear rate of 100 s. -1 This is the value measured as such. The compressive modulus of this viscoelastic material is preferably 0.4 MPa or higher, and more preferably 0.5 MPa or higher. The compressive modulus of this viscoelastic material is preferably 1 MPa or lower, and more preferably 0.8 MPa or lower. The compressive modulus is the maximum load when this viscoelastic material is compressed at 1 mm / min using a Strograph (manufactured by Toyo Seiki Co., Ltd.). When the viscosity and compressive modulus of this viscoelastic material are within the range measured by a capillograph, the interaction between the F particles and the organic resin or inorganic particles is enhanced, which is preferable.

[0061] When the viscoelastic material contains the inorganic particles, the mass ratio of the F polymer to the inorganic particles is preferably 0.05 or more, and more preferably 0.1 or more, with the mass of the F polymer being 1. The above ratio is preferably 20 or less, more preferably 10 or less, and even more preferably 1 or less.

[0062] When the viscoelastic material contains the organic resin, the mass ratio of the F polymer to the organic resin is preferably 0.05 or more, and more preferably 0.1 or more, with the mass of the F polymer being 1. The above ratio is preferably 20 or less, more preferably 10 or less, and even more preferably 1 or less.

[0063] The solid content in this viscoelastic material refers to the total amount of substances that form solids in the molded product formed from this viscoelastic material or the dispersion described later. For example, if this viscoelastic material contains F polymer and the aforementioned organic resin and / or inorganic particles, the total content of these components will be the solid content in this viscoelastic material. The solid content of this viscoelastic material is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. The solid content is 100% by mass or less, and more preferably 80% by mass or less.

[0064] In this viscoelastic material, the content of F particles in the solid content is preferably 20% by mass or more, and more preferably 40% by mass or more. Furthermore, the content of F particles is preferably 90% by mass or less, and more preferably 80% by mass or less. When this viscoelastic material contains these inorganic particles, the content of these inorganic particles in the solid content is preferably 10% by mass or more, and more preferably 20% by mass or more. The content of these inorganic particles is preferably 80% by mass or less, and more preferably 60% by mass or less.

[0065] When this viscoelastic material contains this organic resin, the content of this organic resin in relation to the solid content is preferably 10% by mass or more, and more preferably 20% by mass or more. The content of this organic resin is preferably 80% by mass or less, and more preferably 60% by mass or less. When the viscoelastic material contains both the inorganic particles and the organic resin, it is preferable that at least one of the inorganic particles or the organic resin falls within the specified range, and it is more preferable that both fall within the specified range. For example, the content of F particles, the inorganic particles, and the organic resin in the solid content is preferably such that, with a solid content of 100% by mass, the content of F particles is 40% by mass or more, the content of the inorganic particles is 10% by mass or more, or the content of the organic resin is 10% by mass or more. More preferably, with a solid content of 100% by mass, the content of F particles is 40% by mass or more, the content of the inorganic particles is 10% by mass or more, and the content of the organic resin is 10% by mass or more. For example, the ratio of F particles to the inorganic particles and the organic resin in the viscoelastic material is preferably such that the content of the inorganic particles is 0.05 to 1, or the content of the organic resin is 0.05 to 1, with the content of F particles being 1. It is more preferable that the content of the inorganic particles is 0.05 to 1, and the content of the organic resin is 0.05 to 1, with the content of F particles being 1. To obtain a viscoelastic material with viscosity and composition within the aforementioned range, the composition of the mixed components and, if necessary, the addition of components required during the wet mixing process should be adjusted accordingly. When the viscosity and composition fall within a specified range, this viscoelastic material tends to exhibit excellent liquid properties such as dispersibility and uniformity.

[0066] This viscoelastic material may further contain additives such as thixotropic agents, viscosity modifiers, defoamers, dehydrators, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, conductive agents, mold release agents, surface treatment agents, flame retardants, and various fillers. These additives may be present in the aforementioned mixed components, or they may be added during the wet mixing process.

[0067] In this method, it is preferable that the mixture contains at least the organic resin, the ratio of the mass of the organic resin to the mass of the F polymer in the wet mixing is 0.1 or more, and the total content of the F polymer and the organic resin in the resulting viscoelastic body is 40% by mass or more. When the proportion of this organic resin is within the specified range, the F particles are less likely to re-aggregate, making it easier to obtain this viscoelastic material with excellent uniformity and dispersibility. Furthermore, when the total mass content of the F polymer and organic resin is within the specified range, the viscosity during wet mixing tends to increase, allowing the F particles and organic resin to mix well, making it easier to obtain this viscoelastic material with excellent uniformity and dispersibility.

[0068] Furthermore, in this method, it is preferable to dry-crush the powder of the F polymer to obtain the F particles, and then wet-mix the particles with a thermosetting resin varnish, such that the ratio of the mass of the thermosetting resin to the mass of the F polymer is 0.1 or more. When a thermosetting resin varnish is used as the organic resin, the thermosetting resin and F particles readily interact through the solvent. During wet mixing, the thermosetting resin partially hardens and thickens due to the heat generated during mixing, and mixes with the F particles. Furthermore, when the ratio of the mass of the thermosetting resin to the mass of the F polymer is within a certain range, this viscoelastic material contains a sufficient amount of thermosetting resin relative to the F particles. As a result, the surface of the F particles is effectively covered with the thermosetting resin and is easily stabilized, and this viscoelastic material tends to have excellent uniformity and dispersibility.

[0069] The viscoelastic material of the present invention comprises the F particles and the thermosetting resin, which is the organic resin, wherein the ratio of the mass of the thermosetting resin to the mass of the F polymer is 0.1 or more, and the total content of the F polymer and the thermosetting resin is 40% by mass or more. Such viscoelastic materials contain a high proportion of F particles and thermosetting resin in a fixed amount, have high viscosity, and the thermosetting resin effectively covers the surface of the F particles, making aggregation of F particles less likely, resulting in excellent uniformity and dispersibility. The definitions and ranges of F polymers, F particles, organic resins, and other components that may be contained in such viscoelastic materials are the same as those in the present Act. However, the ratio of the mass of the thermosetting resin to the mass of the F polymer is preferably 0.2 or more. The ratio is preferably 20 or less, more preferably 10 or less, and even more preferably 1 or less. The total content of F polymer and thermosetting resin is preferably 60% by mass or more. The total content is 100% by mass or less, and preferably 80% by mass or less. Such viscoelastic materials can be suitably manufactured by the method described above.

[0070] By further diluting the aforementioned viscoelastic material with water or a non-aqueous solvent, a dispersion with a viscosity of 10,000 mPa·s or less can be obtained. Because the viscoelastic material has excellent uniformity and dispersibility, diluting it yields a dispersion (hereinafter also referred to as "this dispersion") with excellent liquid properties such as dispersion stability, uniformity, rheology, coating properties, and storage stability. Furthermore, by setting the viscosity of the obtained dispersion within this range, particularly excellent dispersion stability can be achieved, and a thick layer can be formed by using the obtained dispersion to form a layer containing the F polymer. The non-aqueous solvent can be the same as the non-aqueous solvent used in the wet mixing described above, and the preferred non-aqueous solvent is also the same.

[0071] Furthermore, this viscoelastic material may be mixed with an organic resin or inorganic particles to form this dispersion. Because this viscoelastic material has excellent uniformity and dispersibility, even when further mixed with an organic resin or inorganic particles, the F particles are less likely to re-aggregate, resulting in a dispersion with excellent liquid properties such as dispersion stability, uniformity, rheology, coating properties, and storage stability. The organic resin and inorganic particles mentioned above are the same as the organic resin and inorganic particles mentioned above, and the preferred organic resin and inorganic particles are also the same. The organic resin and inorganic resin mixed with the viscoelastic body may be the same as or different from the organic resin and inorganic particles contained in the viscoelastic body. The content of F particles in the resulting dispersion is preferably 10% by mass or more, and more preferably 20% by mass or more. The content of F particles is preferably 60% by mass or less, and more preferably 50% by mass or less.

[0072] When diluting the viscoelastic material with water or a non-aqueous solvent, or when mixing it with an organic resin or inorganic particles, the same mixer as described above may be used for dilution or mixing. A rotary-orbit mixer or a thin-film swirling high-speed mixer is preferred as the mixer to be used.

[0073] The viscosity of this dispersion is preferably 10 mPa·s or higher, and more preferably 100 mPa·s or higher. The viscosity of this dispersion is preferably 5000 mPa·s or lower, and more preferably 3000 mPa·s or lower. The thixotropic ratio of this dispersion is preferably 1.0 to 3.0.

[0074] If the dispersion contains water, the pH of the dispersion is preferably 5 to 10, and more preferably 8 to 10. To adjust the pH of this dispersion, a pH adjuster or pH buffer may be added to the viscoelastic material or during the preparation of the dispersion. Examples of pH adjusters include amines, ammonia, and citric acid. Examples of pH buffers include tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium bicarbonate, ammonium carbonate, and ammonium acetate.

[0075] When preparing the dispersion from the viscoelastic material, the surfactant, curing agent, or additive may be added further.

[0076] The viscoelastic material and dispersion obtained by the above method are useful as coating materials for imparting insulating properties, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and thermal conductivity. This viscoelastic material and dispersion can be used specifically in printed circuit boards, thermal interface materials, substrates for power modules, coils used in power devices such as motors, automotive engines, heat exchangers, vials, syringes, ampoules, medical wires, secondary batteries such as lithium-ion batteries, primary batteries such as lithium batteries, radical batteries, solar cells, fuel cells, lithium-ion capacitors, hybrid capacitors, capacitors, capacitors such as aluminum electrolytic capacitors or tantalum electrolytic capacitors, electrochromic elements, electrochemical switching elements, electrode binders, electrode separators, and positive or negative electrodes.

[0077] Furthermore, this viscoelastic material and dispersion are also useful as adhesives for bonding components. Specifically, this viscoelastic material and dispersion can be used for bonding ceramic components, metal components, electronic components such as IC chips, resistors, and capacitors on substrates of semiconductor elements and module components, bonding circuit boards to heat sinks, and bonding LED chips to substrates. Furthermore, this viscoelastic material and dispersion, which also contain conductive fillers, can be suitably used in applications requiring conductivity, such as in the field of printed electronics. Specifically, it can be used in the manufacture of conductive elements in printed circuit boards, sensor electrodes, and the like.

[0078] This viscoelastic material and dispersion can be suitably used as a negative-type resist composition. The resist composition can be applied to the surface of a substrate by coating methods such as screen printing, bar coating, or blade coating. After coating, the coating film is dried, and the resulting dried film is exposed to light using an exposure mask having a predetermined exposure pattern. The dried film after exposure is developed with a developer solution, and then cured by irradiation with ultraviolet light to obtain a laminate having a substrate and a cured film on the substrate surface. Furthermore, this viscoelastic material and dispersion can also be suitably used as a filler material for filling through-holes or recesses in multilayer printed circuit boards. The viscoelastic material and dispersion can be filled into through-holes or recesses by screen printing, roll coating, die coating, or vacuum printing. It is preferable to fill the through-holes or recesses with the composition to the extent that it slightly overflows.

[0079] From this viscoelastic material or dispersion, a laminate having a base layer and a layer containing F polymer on the surface of the base layer (hereinafter also referred to as the "F layer") can be suitably produced. One method for manufacturing the laminate is to coat the surface of a substrate with the dispersion, heat it as needed to remove the solvent, and then heat it further to bake the F polymer and form the F layer. Alternatively, if the organic resin in the dispersion is a thermosetting resin or a photocurable resin, the dispersion may be coated on the surface of a substrate, heat it as needed to remove the solvent, and then heat it further or irradiate it with light to cure the organic resin and form the F layer. Examples of substrates include metal substrates such as metal foils made of copper, nickel, aluminum, titanium, and their alloys; heat-resistant resin films such as polyimide, polyamide, polyetheramide, polyphenylene sulfide, polyallyl ether ketone, polyamide-imide, liquid crystalline polyester, and tetrafluoroethylene polymers; prepreg substrates, which are precursors to fiber-reinforced resin substrates; ceramic substrates such as silicon carbide, aluminum nitride, and silicon nitride; and glass substrates.

[0080] The substrate can take the shape of a flat, curved, or uneven surface. Furthermore, the substrate may be in the form of a foil, plate, film, or fiber. The ten-point average roughness of the substrate surface is preferably 0.01 to 0.05 μm. The substrate surface may be surface-treated with a silane coupling agent or plasma-treated.

[0081] Coating methods for the viscoelastic material and dispersion include coating, droplet dispensing, and immersion, with roll coating, knife coating, bar coating, die coating, or spraying being preferred. When removing the solvent, heating is preferably carried out at 50 to 200°C for 0.1 to 30 minutes. During this heating, it is not necessary to completely remove the solvent; it is sufficient to remove it to the extent that the formed layer can maintain its self-supporting film structure. In addition, during heating, air may be blown in to promote the removal of the liquid dispersion medium by air drying.

[0082] When heating the F polymer for firing, it is preferable to do so at a temperature higher than the firing temperature of the F polymer, and more preferably at 360 to 400°C for 0.1 to 30 minutes. Examples of heating devices for each heating process include ovens and forced-air drying ovens. The heat source in the device may be a contact-type heat source such as hot air or a hot plate, or a non-contact heat source such as infrared radiation. Furthermore, each heating process may be carried out under normal pressure or under reduced pressure. Furthermore, the atmosphere used for each heating process may be any of the following: an air atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a nitrogen gas atmosphere, or any other inert gas atmosphere.

[0083] If the viscoelastic material or dispersion contains a thermosetting resin or a photocurable resin as the organic resin, the organic resin may be cured by a method appropriate to the resin to form the F layer.

[0084] The F layer is formed by coating the substrate with the viscoelastic material or dispersion, heating, or light irradiation. These steps may be performed once or repeated two or more times. For example, the viscoelastic material or dispersion may be coated onto the surface of the substrate and heated to form the F layer, and then the viscoelastic material or dispersion may be coated onto the surface of the F layer and heated or light-irradiated to form a second F layer. Alternatively, the viscoelastic material or dispersion may be coated onto the surface of the substrate, heated to remove the solvent, and then the viscoelastic material or dispersion may be coated onto the surface again and heated or light-irradiated to form the F layer.

[0085] The viscoelastic material and the dispersion may be coated on only one surface of the substrate, or on both surfaces of the substrate. In the former case, a laminate is obtained having a substrate layer and an F layer on one surface of the substrate layer, and in the latter case, a laminate is obtained having a substrate layer and an F layer on both surfaces of the substrate layer. Suitable examples of laminates include a metal-clad laminate having a metal foil and an F layer on at least one surface of the metal foil, and a polyimide film and a multilayer film having an F layer on both surfaces of the polyimide film. The thickness of the F layer is preferably 0.1 to 200 μm, and more preferably 1 to 50 μm. The peel strength between the F layer and the substrate layer is preferably 10 to 100 N / cm. Furthermore, the substrate layer may be removed from the laminate to obtain a film containing the F polymer.

[0086] The laminate of the F layer and the substrate is useful as an antenna component, printed circuit board, aircraft component, automobile component, sports equipment, food industry product, heat dissipation component, paint, cosmetic, etc. Specifically, this includes wire insulation materials for aircraft and other applications, enameled wire insulation materials used in motors for electric vehicles and other applications, electrical insulation tapes, insulating tapes for oil drilling, oil transport hoses, hydrogen tanks, printed circuit board materials, separation membranes such as microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, and gas separation membranes, electrode binders for lithium secondary batteries and fuel cells, copy rolls, furniture, car dashboards, covers for home appliances, load bearings, yaw bearings, sliding shafts, valves, bearings, bushings, seals, thrust washers, etc. It is useful for sliding components such as wear rings, pistons, slide switches, gears, cams, belt conveyors and food transport belts, tension ropes, wear pads, wear strips, tube lamps, test sockets, wafer guides, wear parts for centrifugal pumps, chemical and water supply pumps, tools such as shovels, files, drills and saws, boilers, hoppers, pipes, ovens, baking molds, chutes, racket strings, dies, toilets, container coverings, power devices, transistors, thyristors, rectifiers, transformers, power MOS FETs, CPUs, heat sinks, metal heat sinks, blades for wind turbines and wind power generation equipment and aircraft, casings for personal computers and displays, electronic device materials, interior and exterior parts for automobiles, sealing materials for processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, plasma processing equipment, heat dissipation components in processing units such as sputtering and various dry etching equipment, and as electromagnetic shielding.

[0087] When this viscoelastic material and its dispersion are impregnated into a woven fabric and heated, a woven fabric impregnated with F polymer is obtained. The resulting woven fabric can also be described as a coated woven fabric, in which the woven fabric is covered with an F layer. The woven fabric is preferably a glass fiber woven fabric, a carbon fiber woven fabric, an aramid fiber woven fabric, or a metal fiber woven fabric. The woven fabric may be surface-treated with a silane coupling agent. The content of F polymer in the resulting woven fabric is preferably 30 to 80% by mass. When impregnating the woven fabric with the viscoelastic material and dispersion, the woven fabric may be immersed in the viscoelastic material and dispersion, or the viscoelastic material and dispersion may be applied to the woven fabric. A drying method for the woven fabric coated with this viscoelastic material and dispersion is the same as the heating method used to obtain the laminate. The resulting woven fabric and the base material may be placed facing each other and heat-pressed together to form a laminate in which the base material and the woven fabric are stacked in this order. The resulting woven fabric can be used for similar purposes as laminates. Furthermore, this woven fabric is also useful as a lining material for the inner walls of components such as tanks, pipes, and containers.

[0088] Although the present method, the present viscoelastic material, the viscoelastic material of the present invention, and a method for obtaining a dispersion from the viscoelastic material obtained by the present method have been described above, the present invention is not limited to the configuration of the embodiments described above. For example, the present method and the method for obtaining the dispersion from the viscoelastic material obtained by this method may have additional steps in the configuration of the above embodiment, or may be replaced with any other steps that produce a similar effect. Furthermore, the present viscoelastic material and the viscoelastic material of the present invention may have additional components in the configuration of the above embodiment, or may be replaced with any other components that perform a similar function. [Examples]

[0089] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1. Preparation of each component [powder] Powder 1: Contains TFE units, NAH units, and PPVE units in the following proportions: 97.9 mol%, 0.1 mol%, and 2.0 mol%, respectively, with carbonyl groups in a main chain of 1 × 10¹⁶ carbon atoms. 6 A powder consisting of particles (D50: 2.1 μm) of a heat-meltable polymer (glass transition temperature: 80°C; hereinafter also referred to as "F polymer 1") having 1000 particles per unit. Powder 2: Contains 98.7 mol% and 1.3 mol% of TFE units and PPVE units, respectively, with carbonyl groups having a main chain of 1 × 10¹⁶ carbon atoms. 6 Powder consisting of polymer particles (D50: 1.8 μm) having 40 molecules per particle (glass transition temperature: 80°C; hereinafter also referred to as "F polymer 2").

[0090] [Mixed ingredients] Mixed component 1: A liquid composition of resin varnish containing a carboxyl group-containing phenol resin (acid value: 80 mg KOH / g; a photocurable and thermocurable resin; hereinafter also referred to as "aromatic resin 1") and toluene as a solvent. Mixed component 2: A slurry-like liquid composition containing silica particles (D50: 1.0 μm) with toluene as the solvent.

[0091] 2. Preparation of viscoelastic materials and dispersions [Example 1] Powder 1 was placed in a rotary-orbit mixer, and the mixer was operated for 5 minutes at a rotation speed of 2000 rpm and a temperature of 50°C to perform dry crushing. Further, mixed component 1 was placed in the rotary-orbit mixer, and the mixer was operated for 5 minutes at a rotation speed of 2000 rpm and a temperature of 100°C to perform wet mixing, obtaining a viscoelastic body 1 (viscosity measured by capillograph: 5000 Pa·s, compressive modulus: 0.6 MPa) containing 60 parts by mass of F polymer 1 particles and 40 parts by mass of aromatic resin 1. A viscoelastic material 1 and an aromatic resin varnish 1 were placed in a rotary-revolving mixer, and the mixer was then operated at a rotation speed of 2000 rpm for 5 minutes to obtain a dispersion 1 (viscosity: 300 mPa·s) containing 20 parts by mass of powder 1 and 80 parts by mass of aromatic resin 1.

[0092] [Example 2] Except for changing powder 1 to powder 2, viscoelastic material 2 (viscosity measured by capillography: 7000 Pa·s, compressive modulus: 0.7 MPa) and dispersion 2 (viscosity: 500 mPa·s) were obtained in the same manner as in Example 1. [Example 3] Except for performing dry crushing at 90°C, a viscoelastic body 3 (viscosity measured by capillography: 9000 Pa·s, compressive modulus: 0.9 MPa) and a dispersion 3 (viscosity: 800 mPa·s) were obtained in the same manner as in Example 1. [Example 4] Except for performing wet mixing at 70°C, a viscoelastic body 4 (viscosity measured by capillography: 10,000 Pa·s, compressive modulus: 0.9 MPa) and a dispersion 4 (viscosity: 800 mPa·s) were obtained in the same manner as in Example 1. [Example 5] Powder 2 and mixed component 1 were placed in a rotary-orbit mixer, and the mixer was operated at a rotation speed of 2000 rpm for 5 minutes to mix, obtaining a viscoelastic body 5 containing 60 parts by mass of powder 2 and 40 parts by mass of aromatic resin 1. Due to the low homogeneity of the viscoelastic body 5, the viscosity and compressive modulus measured by capillography were not measured. Viscoelastic body 5 and aromatic resin 1 were placed in a rotary-orbit mixer, and the mixer was operated at a rotation speed of 2000 rpm for 5 minutes to obtain a dispersion 5 (viscosity: 1200 mPa·s) containing 20 parts by mass of powder 2 and 80 parts by mass of aromatic resin 1.

[0093] 3. Evaluation 3-1. Homogeneity of viscoelastic materials The homogeneity of each viscoelastic material was visually confirmed and evaluated according to the following criteria. [Evaluation Criteria] ○: It is in a uniform state and does not crack when pressed. △: Although uniform in appearance, cracks appear when pressed. ×: A granular material is visible on the surface, and it crumbles when pressed.

[0094] 3-2. Dispersibility of the dispersion The dispersion state of each dispersion was visually inspected and evaluated according to the following criteria. ○: No aggregates are formed even when left standing at 25°C for 7 days. △: Aggregates are formed when left standing at 25°C for 7 days, but can be easily redispersed. ×: Aggregates are formed when left standing at 25°C for 7 days and cannot be easily redispersed.

[0095] 3-3. Smoothness of the surface of the convex part In a laminate of a film of F-polymer 1 and an electrolytic copper foil (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., "CF-T49A-DS-HD2"), each dispersion liquid was applied to the surface of the electrolytic copper foil opposite to the film of F-polymer 1 to form a coating film on the laminate. This coating film was dried at 80°C for 10 minutes to obtain a dried film with a thickness of 50 μm. Next, using an exposure mask having openings in a predetermined pattern, ultraviolet rays were irradiated onto the dried film. The integrated light amount of the ultraviolet rays was 150 mJ / cm 2 as specified. Next, the dried film after ultraviolet irradiation was developed with a 1.0 mass% aqueous sodium carbonate solution. Next, the developed dried film was heated and cured at 150°C for 50 minutes to form convex parts.

[0096] The formed convex parts were confirmed with an optical microscope and evaluated according to the following criteria. [Evaluation criteria] ○: No voids are generated on the surface of the convex part △: Voids are generated in a part of the surface of the convex part ×: Voids are generated on the entire surface of the convex part

[0097] 3-4. Adhesion of the polymer layer Each dispersion liquid was applied to an electrolytic copper foil (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., "CF-T49A-DS-HD2") to form a coating film, and this coating film was dried at 80°C for 10 minutes to obtain a dried film (thickness: 50 μm). Next, without using an exposure mask, ultraviolet rays were irradiated onto the entire dried film, and further, the dried film was heated and cured at 150°C for 50 minutes to form a polymer layer, and a copper-clad laminate having a polymer layer on the surface of the electrolytic copper foil was obtained. The integrated light amount of the ultraviolet rays was 150 mJ / cm 2 as specified. From the obtained copper-clad laminate, a rectangular test specimen measuring 100 mm in length and 10 mm in width was cut out. Subsequently, the polymer layer and copper foil were peeled off from one end of the specimen to a position 50 mm from the longitudinal end. Then, with the 50 mm position from the longitudinal end of the specimen as the center, a tensile testing machine (manufactured by Orientec Co., Ltd.) was used to peel the specimen at a tensile speed of 50 mm / min at a 90-degree angle. The maximum load was defined as the peel strength (N / cm) and evaluated according to the following criteria.

[0098] [Evaluation Criteria] ○: Peel strength is 10 N / cm or higher. △: Peel strength is 5 N / cm or more and less than 10 N / cm ×: Peel strength is less than 5 N / cm

[0099] 3-5. Electrical properties of the polymer layer The electrolytic copper foil of each copper-clad laminate obtained in the same manner as in 3-4 was etched with an aqueous ferric chloride solution to obtain individual polymer layers. A sample measuring 10 cm in length and 5 cm in width was cut from the obtained individual polymer layers, and the dielectric loss tangent (measurement frequency: 10 GHz) was measured using the SPDR (Split Post Dielectric Resonance) method and evaluated according to the following criteria.

[0100] [Evaluation Criteria] ○: The dielectric constant is 3.5 or less. △: Dielectric constant is greater than 3.5 and less than or equal to 4.0 ×: The dielectric constant is greater than 4.0 These evaluation results are summarized in Table 1 below.

[0101] [Table 1]

[0102] 4. Preparation of viscoelastic materials and dispersions (Part 2) [Example 6] Powder 1 was placed in a rotary-orbit mixer, and the mixer was operated for 5 minutes at a rotation speed of 2000 rpm and a temperature of 50°C to perform dry crushing. Mixing component 2 was then placed in the rotary-orbit mixer, and the mixer was operated for 5 minutes at a rotation speed of 2000 rpm and a temperature of 100°C to perform wet mixing. Mixing component 1 was then placed in the mixer, and the mixer was operated for 5 minutes under the same conditions to perform wet mixing, thereby obtaining a viscoelastic body 6 containing 34 parts by mass of F polymer 1 particles, 33 parts by mass of silica particles, and 33 parts by mass of aromatic resin 1. The viscoelastic body 6 was mixed with toluene to obtain a dispersion 6 containing 15% by mass of F polymer 1 particles.

[0103] [Example 7] A viscoelastic body 7 and a dispersion 7 were obtained in the same manner as in Example 6, except that mixing component 1 was added first to the rotational mixer, and then mixing component 2 was added later. Both dispersion 6 and dispersion 7 had low viscosity, suppressed foaming, and offered excellent handling properties. However, when comparing dispersion 6 and dispersion 7, dispersion 6 had even lower viscosity and suppressed foaming more effectively. Dispersion 6 also offered superior handling properties. [Industrial applicability]

[0104] As is clear from the results above, the viscoelastic material obtained by this method provides a dispersion with excellent liquid properties such as dispersion stability. Thus, the dispersion obtained from the viscoelastic material has excellent dispersibility, and the polymer layer of the resulting laminate has excellent smoothness, adhesion, and electrical properties.

Claims

1. A method for producing a dispersion, comprising: dry crushing a powder of a heat-meltable tetrafluoroethylene polymer to obtain particles of the tetrafluoroethylene polymer; wet mixing the particles with at least one of an organic resin and inorganic particles in the presence of a liquid substance to obtain a viscoelastic body containing the particles and at least one of the organic resin and inorganic particles; and further mixing the viscoelastic body with the organic resin or inorganic particles to obtain a dispersion.

2. The manufacturing method according to claim 1, wherein the dry crushing is carried out using at least one mixer selected from the group consisting of a Henschel mixer, a pressure kneader, a Banbury mixer, a rotational mixer, a planetary mixer, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a dispermat, an SC mill, a spike mill, an agitator mill, a microfluidizer, a nanomizer, an ultimateizer, a dissolver, a disper, and a high-speed impeller.

3. The manufacturing method according to claim 1, wherein the dry crushing is performed at a temperature below the glass transition temperature of the tetrafluoroethylene polymer.

4. The manufacturing method according to claim 1, wherein the wet mixing is performed using at least one mixer selected from the group consisting of a Henschel mixer, a pressure kneader, a Banbury mixer, a rotational mixer, a planetary mixer, a ball mill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, a spike mill, an agitator mill, a microfluidizer, a nanomizer, an ultimateizer, an ultrasonic homogenizer, a dissolver, a disper, a high-speed impeller, and a thin-film swirling high-speed mixer.

5. The manufacturing method according to claim 1, wherein the wet mixing is carried out at a temperature above the glass transition temperature of the tetrafluoroethylene polymer.

6. The manufacturing method according to claim 1, wherein the glass transition temperature of the tetrafluoroethylene polymer is 60 to 150°C.

7. The manufacturing method according to claim 1, wherein the organic resin is a thermosetting resin.

8. The manufacturing method according to claim 1, wherein the organic resin is at least one aromatic resin selected from the group consisting of aromatic epoxy resins, phenolic resins, aromatic polyimide resins, precursors of aromatic polyimide resins, aromatic polyamideimide resins, and precursors of aromatic polyamideimide resins.

9. The manufacturing method according to claim 1, wherein the wet mixing is performed by wet mixing the particles and the inorganic particles in the presence of a liquid substance, and then wet mixing in the organic resin.

10. The manufacturing method according to claim 1, wherein the wet mixing is performed by wet mixing the particles with a liquid composition containing at least one of an organic resin and inorganic particles.

11. The manufacturing method according to claim 10, wherein the liquid composition contains at least an organic resin, the ratio of the mass of the organic resin to the mass of the tetrafluoroethylene polymer in the wet mixing is 0.1 or more, and the total content of the tetrafluoroethylene polymer and the organic resin in the viscoelastic body is 40% by mass or more.

12. A method for producing a dispersion, comprising: dry crushing a powder of a heat-meltable tetrafluoroethylene polymer to obtain particles of the tetrafluoroethylene polymer; wet mixing the particles with a thermosetting resin varnish, with the ratio of the mass of the thermosetting resin to the mass of the tetrafluoroethylene polymer being 0.1 or more, to obtain a viscoelastic body containing the particles and the thermosetting resin; and further mixing the viscoelastic body with an organic resin or inorganic particles to obtain a dispersion.

13. A method for producing a dispersion, comprising further diluting a dispersion obtained by the production method described in any one of claims 1 to 12 with water or a non-aqueous solvent to obtain a dispersion with a viscosity of 10,000 mPa·s or less.

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