Electrodeposition dispersion, method for producing insulating film, and conductor with insulating film

Abstract

To provide an electrodeposition liquid containing a tetrafluoroethylene polymer, excellent in dispersion stability and handleability, and capable of forming an insulating film excellent in physical properties such as heat resistance and electric characteristics (low linear expansion coefficient, low dielectric constant and low dielectric loss tangent), and further excellent in surface appearance and film thickness uniformity on a conductor as an electrodeposition film.SOLUTION: An electrodeposition dispersion comprising: a resin component in which a proportion of particles of a tetrafluoroethylene polymer is 30% by mass or more; a nonionic surfactant having a hydroxyl group; and a liquid medium in which a proportion of water is 50% by mass or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrodeposition solution containing particles of a tetrafluoroethylene-based polymer, a method for producing an insulating coating using the electrodeposition solution, and a conductor with an insulating coating. [Background technology]

[0002] Insulated conductors, which are conductors coated with an insulating film made of insulating resin, are widely used as conductive materials and heat dissipation materials in various electrical devices. Electrodeposition is a known method for forming an insulating film on the surface of a conductor. The electrodeposition method involves immersing a conductor and a counter electrode in an electrodeposition solution containing an insulating resin, and applying a voltage between the conductor and the counter electrode to deposit an insulating film on the surface of the conductor. Patent Documents 1 to 3 propose forming an insulating coating containing a tetrafluoroethylene-based polymer and a polyimide-based resin on the surface of a conductor by electrodeposition using an electrodeposition solution containing particles of a tetrafluoroethylene-based polymer and a polyimide-based resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-298674 [Patent Document 2] Japanese Patent Application Publication No. 2018-131562 [Patent Document 3] International Publication No. 2022 / 108653 Summary of the Invention [Problem to be solved by the invention]

[0004] Because tetrafluoroethylene-based polymers have low surface tension and poor dispersibility in liquid, electrodeposition solutions containing these particles have low dispersion stability and are not easily handled, such as in terms of fluidity. This problem is likely to become more pronounced in aqueous electrodeposition solutions containing tetrafluoroethylene-based polymer particles, as in Patent Documents 1 to 3, particularly in electrodeposition solutions with a high particle content, and coating defects are likely to occur during electrodeposition. Furthermore, the surface appearance of the formed insulating coating is likely to be impaired, and the insulating coating is likely to chip off at the end faces of the conductor. The present inventors have found that an aqueous electrodeposition solution containing tetrafluoroethylene-based polymer particles, a specific nonionic surfactant, and water stabilizes the state of the particles in the solution, has excellent dispersion stability, and is easy to handle. They have also found that an electrodeposition film formed from such an electrodeposition solution has excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent) based on the tetrafluoroethylene-based polymer, and also has excellent surface appearance and film thickness uniformity, which led to the present invention. An object of the present invention is to provide an electrodeposition solution containing a tetrafluoroethylene-based polymer, which is capable of forming an insulating coating on a conductor as an electrodeposited film, which has excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric dissipation factor), and further has excellent surface appearance and film thickness uniformity, and which has excellent dispersion stability and handleability. Another object of the present invention is to provide a method for producing an insulating coating using the electrodeposition solution to form an insulating coating having the above-mentioned excellent properties on a conductor as an electrodeposited film, and to provide a conductor with an insulating coating. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] An electrodeposition solution comprising a resin component having a ratio of tetrafluoroethylene-based polymer particles of 30% by mass or more, a nonionic surfactant having a hydroxyl group, and a liquid medium having a ratio of water of 50% by mass or more. [2] The electrodeposition solution according to [1], wherein the tetrafluoroethylene-based polymer is heat-fusible and contains an oxygen-containing polar group. [3] The electrodeposition solution according to [1] or [2], wherein the average particle size of the tetrafluoroethylene polymer particles is 1 μm or more and less than 10 μm. [4] The electrodeposition solution according to any one of [1] to [3], wherein the proportion of the tetrafluoroethylene polymer particles in the resin component is 30 to 100 mass %. [5] The electrodeposition solution according to any one of [1] to [4], wherein the content of the tetrafluoroethylene polymer particles is 30 to 90 mass %. [6] The electrodeposition solution according to any one of [1] to [5], wherein the content of the nonionic surfactant having a hydroxyl group is in the range of 1 to 15 mass % relative to the particles of the tetrafluoroethylene-based polymer. [7] The electrodeposition solution according to any one of [1] to [6], wherein the nonionic surfactant having a hydroxyl group has an HLB value of 3 to 16 as calculated by the Griffin equation. [8] The electrodeposition solution according to any one of [1] to [7], wherein the nonionic surfactant having a hydroxyl group is a silicone-based surfactant or an acetylene diol-based surfactant. [9] The electrodeposition solution according to any one of [1] to [8], wherein the nonionic surfactant having a hydroxyl group is a nonionic surfactant containing no fluorine atoms.

[10] The electrodeposition solution according to any one of [1] to [9], wherein the proportion of water in the liquid medium is 80 to 100 mass %.

[11] The electrodeposition solution according to any one of [1] to

[10] , further containing an electrodeposition auxiliary.

[12] An electrodeposition solution according to any one of [1] to

[11] , having a viscosity of 10 to 10,000 mPa·s.

[13] A method for producing an insulating coating, comprising immersing a conductor and a counter electrode in the electrodeposition solution according to any one of [1] to

[12] , applying a voltage between the conductor and the counter electrode, and forming an insulating coating on the conductor.

[14] A conductor with an insulating coating, comprising a conductor and an insulating coating that covers at least a part of the conductor, wherein the insulating coating is formed using the electrodeposition solution according to any one of [1] to

[12] and contains 30% by mass or more of a tetrafluoroethylene-based polymer. [Effects of the Invention]

[0006] The present invention provides an electrodeposition solution with excellent dispersion stability and ease of handling. From such an electrodeposition solution, an insulating coating can be formed on a conductor, which has excellent physical properties based on the tetrafluoroethylene polymer, such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent), as well as excellent surface appearance and film thickness uniformity. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following terms have the following meanings: "Average particle size (D50)" is the volume-based cumulative 50% diameter of particles or 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 particle group as 100%. The "average particle size (D50)" is the particle size at the point on the cumulative curve where the cumulative volume is 50%. The D50 of particles or fillers can be determined by dispersing the particles in water and analyzing them by a laser diffraction / scattering method using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). The "average particle size (D90)" is the volume-based cumulative 90% diameter of particles, which is determined in the same manner as D50. The specific surface area of ​​particles or fillers is a value calculated by measuring particles by gas adsorption (constant volume method) BET multipoint method, and is determined using NOVA4200e (manufactured by Quantachrome Instruments). 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 "glass transition temperature (Tg)" is a value measured by analyzing a polymer using the dynamic mechanical analysis (DMA) method. The "viscosity" is determined by measuring the electrodeposition solution 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 electrodeposition solution 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 (Hydrophilic-Lipophilic Balance) value" of a nonionic surfactant is a value defined by the following calculation formula (Griffin formula) according to the Griffin method. HLB value = 20 x [total chemical formula weight of hydrophilic parts] / molecular weight 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."

[0008] The electrodeposition liquid of the present invention (hereinafter also referred to as "the present electrodeposition liquid") contains a resin component in which the proportion of particles (hereinafter also referred to as "F particles") of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") is 30% by mass or more, a nonionic surfactant having a hydroxyl group, and a liquid medium in which the proportion of water is 50% by mass or more. This electrodeposition liquid has dispersion stability and fluidity, is suppressed in foaming, and is easy to handle, and the electrodeposition film formed from this electrodeposition liquid has excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric tangent) based on the F polymer, and also has excellent surface appearance and film thickness uniformity. In this specification, "excellent surface appearance" includes both excellent surface smoothness such as "little surface roughness" and excellent appearance observed visually or with an analytical instrument such as "no streaks, cracks, defects, etc. on the surface." The reason why the present electrodeposition solution has such excellent handling properties is not entirely clear, but is thought to be as follows.

[0009] The surfactant contained in this electrodeposition solution is believed to adsorb to the F particle surface, stably dispersing the low-surface-tension F particles in water and improving the solution's fluidity, viscosity, thixotropy, and other liquid properties. Meanwhile, this specific surfactant itself is nonionic and is less susceptible to the effects of current flow during the formation of the electrodeposition film. Therefore, it not only does not interfere with the electrodeposition of F particles onto the conductor surface, but may even promote electrodeposition by improving the liquid properties. As a result, the state of the F particles in the solution is stabilized, including the suppression of the formation of coarse particles, and foaming is also suppressed, resulting in an easy-to-handle electrodeposition solution. Furthermore, the electrodeposition film formed is believed to have excellent physical properties based on the F polymer, as well as excellent surface appearance and film thickness uniformity. This mechanism of action becomes even more pronounced when the electrodeposition solution contains an electrodeposition aid, or when the F polymer in the electrodeposition solution has an oxygen-containing polar group and exhibits ionic properties, due to interaction with the F particles.

[0010] The F polymer in the present invention is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The polymer F may be either heat-fusible or non-heat-fusible. Here, a heat-fusible polymer means a polymer that has a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. The melting temperature of the heat-fusible F polymer is preferably 180° C. or higher, more preferably 200° C. or higher. The melting temperature of the F polymer is preferably 325° C. or lower, more preferably 320° C. or lower. In this case, the electrodeposition film formed from the electrodeposition solution tends to have excellent heat resistance.

[0011] The glass transition point of the F polymer is preferably 50° C. or higher, more preferably 75° C. or higher. The glass transition point of the F polymer is preferably 150° C. or lower, more preferably 125° C. or lower. The fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72 to 76% by mass. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of a mixture for wetting tension testing (manufactured by Wako Pure Chemical Industries, Ltd.) specified in JIS K 6768 on a flat plate made of the F polymer.

[0012] The F polymer is preferably polytetrafluoroethylene (PTFE), a polymer containing TFE units and units based on ethylene (ETFE), a polymer containing TFE units and units based on propylene, a polymer containing TFE units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units) (PFA), or a polymer containing TFE units and units based on hexafluoropropylene (FEP), with PFA and FEP being more preferred, and PFA being even more preferred. These polymers may further contain units based on other comonomers. Examples of PTFE include low molecular weight PTFE and modified PTFE. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3, or CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and PPVE is more preferred.

[0013] The F polymer preferably has an oxygen-containing polar group, more preferably has a hydroxyl-containing group or a carbonyl-containing group, and even more preferably has a carbonyl-containing group. In this case, the electrodeposition solution tends to have excellent dispersion stability and ease of handling, and the electrodeposition film formed from the electrodeposition solution tends to have excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric loss tangent), as well as excellent surface appearance. The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH and -C(CF3)2OH. The carbonyl group-containing group 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-), and more preferably an acid anhydride residue. When the F polymer has an oxygen-containing polar group, the number of oxygen-containing polar groups in the F polymer is 1×10 6 The number per unit is preferably 10 to 5000, more preferably 100 to 3000. The number of oxygen-containing polar groups in the F polymer can be quantified based on the polymer composition or the method described in WO 2020 / 145133.

[0014] The oxygen-containing polar group may be contained in a unit derived from a monomer in the F polymer, or may be contained in a terminal group of the main chain of the F polymer, the former being preferred. Examples of the latter include an F polymer having 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 subjecting an F polymer to plasma treatment or ionizing radiation treatment.

[0015] The F polymer is preferably a polymer having a carbonyl group-containing group containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on a monomer having a carbonyl group-containing group, in which the total units contain 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%, respectively, in that order. Specific examples of such F polymers include the polymers described in WO 2018 / 16644. The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0016] In the present invention, the D50 of the F particles is preferably 1 μm or more and less than 10 μm. The F particles may be solid particles or non-hollow particles. The F particles may be secondary particles formed from nanometer-order fine particles. The D50 of the F particles is preferably 1.0 μm or more, more preferably 1.5 μm or more. The D50 of the F particles is preferably 6 μm or less, more preferably 5 μm or less. Furthermore, the D90 of the F particles is preferably 8 μm or less, more preferably 6 μm or less. When the D90 of the F particles is within the above range, the above-mentioned mechanism of action is more easily realized, and the present electrodeposition solution with a small number of coarse particles is more likely to be obtained.

[0017] The specific surface area of ​​F particles is 1 to 25 m 2 / g, and 6 to 15m 2 / g is more preferable. In this case, the electrodeposition liquid is likely to have excellent dispersion stability and handleability, and also to have good electrodeposition coating properties. In addition, the electrodeposition film formed from the electrodeposition liquid is likely to have excellent physical properties such as heat resistance and electrical properties (low linear expansion coefficient, low dielectric constant, and low dielectric dissipation factor), as well as excellent surface appearance.

[0018] The F particles are particles containing an F polymer, and preferably consist of an F polymer. The F particles may contain a resin or an inorganic compound other than the F polymer, may form a core-shell structure with an F polymer as the core and a resin other than the F polymer or an inorganic compound as the shell, or may form a core-shell structure with an F polymer as the shell and a resin other than the F polymer or an inorganic compound as the core. Here, examples of resins other than F polymer include aromatic polyester, polyamideimide, polyimide, and maleimide, and examples of inorganic compounds include silica and boron nitride.

[0019] One type of F particle may be used, or two or more types may be used. The F particles may also be used in combination with particles of a non-thermofusible tetrafluoroethylene-based polymer. The F particles are preferably particles of a heat-fusible F polymer having a melting temperature of 200 to 325°C, more preferably particles of a heat-fusible F polymer having a melting temperature of 200 to 325°C and containing oxygen-containing polar groups, and the non-thermofusible tetrafluoroethylene-based polymer particles are preferably particles of non-thermofusible PTFE. In this case, the aggregation-inhibiting effect of the heat-fusible F polymer particles and the retention effect due to fibrillation of the non-thermofusible tetrafluoroethylene-based polymer are balanced, which tends to improve the dispersibility of the electrodeposition solution. Furthermore, the electrical properties of the non-thermofusible tetrafluoroethylene-based polymer are likely to be highly exhibited in the electrodeposition film formed therefrom.

[0020] The electrodeposition liquid may further contain, as a resin component, another resin different from the F polymer. Such another resin may be contained in the electrodeposition liquid as solid particles, or may be dissolved or dispersed in water or a liquid medium other than water (hereinafter, water and liquid medium other than water are collectively referred to as "liquid dispersion medium") that constitutes the electrodeposition liquid. Examples of other resins include heat-resistant resins such as polyester resins such as liquid crystalline aromatic polyesters, polyimide resins, polyamide-imide resins, epoxy resins, maleimide resins, urethane resins, polyphenylene ether resins, polyphenylene oxide resins, and polyphenylene sulfide resins. The other resin is preferably an aromatic polymer, more preferably at least one aromatic imide polymer selected from the group consisting of aromatic polyimide, aromatic polyamic acid, aromatic polyamideimide, and a precursor of aromatic polyamideimide. The aromatic polymer is preferably contained in the electrodeposition solution as a varnish dissolved in a liquid dispersion medium.

[0021] Specific examples of aromatic imide polymers include the "UPIA-AT" series (manufactured by UBE), the "NEOPLIM (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company, Inc.), the "SPIXERIA (registered trademark)" series (manufactured by Somar), the "Q-PILON (registered trademark)" series (manufactured by PI Technical Research Institute), the "WINGO" series (manufactured by Wingo Technology Co., Ltd.), the "TOMAID (registered trademark)" series (manufactured by T&K TOKA Corporation), the "KPI-MX" series (manufactured by Kawamura Sangyo Co., Ltd.), and "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.). The other resins preferably have a mass loss rate of 5% by mass / °C or less at 200 to 300°C, more preferably 5% by mass / °C or less from the viewpoint of improving the heat resistance, surface appearance, and film thickness uniformity of the resulting electrodeposited film. The "mass loss rate at 200 to 300°C" refers to the mass loss obtained by heating a 10 mg sample from 200 to 300°C at a heating rate of 10°C / min in a mixed gas atmosphere of 90% by volume of helium and 10% by volume of oxygen using a thermogravimetric analyzer (TG) and a thermogravimetric differential thermal analyzer (TG-DTA), divided by the heating time (10 minutes) and the sample size (10 mg).

[0022] The proportion of F particles in the resin component contained in the electrodeposition solution is 30% by mass or more, preferably more than 50% by mass, more preferably 75% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass. The proportion of F particles in the resin component is preferably 30 to 100% by mass, more preferably 75 to 100% by mass.

[0023] The content of F particles in the electrodeposition solution is preferably 30% by mass or more, more preferably 35% by mass or more, and is preferably 90% by mass or less, more preferably 75% by mass or less, and even more preferably 60% by mass or less.

[0024] Examples of the nonionic surfactant having a hydroxyl group contained in the electrodeposition liquid include glycol surfactants, acetylene diol surfactants, silicone surfactants, and fluorine surfactants. Among these, silicone surfactants and acetylene diol surfactants are preferred. In the present invention, the nonionic surfactant having a hydroxyl group is more preferably a nonionic surfactant that does not contain a fluorine atom.

[0025] As the silicone surfactant, a polyoxyalkylene-modified dimethylsiloxane having a polyoxyalkylene structure as the hydrophilic moiety and a polydimethylsiloxane structure as the hydrophobic moiety is more preferred. Polyoxyalkylene-modified dimethylsiloxane has a polydimethylsiloxane unit (-(CH3)2SiO 2 / 2 The polyoxyalkylene-modified polydimethylsiloxane may have a dimethylsiloxane unit in the main chain, or may have a polydimethylsiloxane unit in both the main chain and the side chain. The polyoxyalkylene-modified polydimethylsiloxane is preferably a polyoxyalkylene-modified polydimethylsiloxane containing a dimethylsiloxane unit in the main chain and an oxyalkylene group in the side chain, or a polyoxyalkylene-modified polydimethylsiloxane containing a dimethylsiloxane unit in the main chain and an oxyalkylene group at the end of the main chain. The oxyalkylene groups contained in the polyoxyalkylene-modified dimethylsiloxane may consist of only one type of oxyalkylene group, or may consist of two or more types of oxyalkylene groups. In the latter case, the different types of oxyalkylene groups may be linked randomly or in blocks. Examples of such silicone surfactants include "BYK-347," "BYK-349," "BYK-378," "BYK-3450," "BYK-3451," "BYK-3455," and "BYK-3456" (manufactured by BYK Japan), and "KF-6011" and "KF-6043" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0026] Acetylene diol surfactants are surfactants that have a carbon-carbon triple bond in the molecule, and examples include acetylene diol surfactants (which have an acetylene bond and two hydroxyl groups in the same molecule) and surfactants in which alkylene oxides such as ethylene oxide and propylene oxide are added to acetylene diol. Examples of such acetylene diol surfactants include the "Surfynol (registered trademark)" series and the "Olfine (registered trademark)" series (both manufactured by Nissin Chemical Industry Co., Ltd.); and the "Acetylenol (registered trademark)" series (manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0027] The HLB value of a nonionic surfactant having a hydroxyl group, calculated by the Griffin equation, is from 1 to 18, preferably 3 or more, more preferably 6 or more, and even more preferably 10 or more. The HLB value is preferably 16 or less. The HLB value of the nonionic surfactant having a hydroxyl group is preferably 3 to 16 as calculated by the Griffin equation.

[0028] The content of the nonionic surfactant having a hydroxyl group is preferably in the range of 1 to 15% by mass, more preferably 3 to 10% by mass, relative to the F particles in the electrodeposition liquid. One type of nonionic surfactant may be used, or two or more types may be used.

[0029] The proportion of water in the liquid medium constituting the present electrodeposition liquid is 50% by mass or more. The proportion of water in the liquid medium is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 98% by mass or more, and may be 100% by mass. The proportion of water in the liquid medium is preferably 80 to 100% by mass. In the present electrodeposition liquid, even when the proportion of water in the liquid medium is high, the dispersion stability of the F particles is excellent due to the mechanism described above. Therefore, an electrodeposition film with excellent surface appearance and film thickness uniformity is easily obtained. The liquid medium other than water is preferably a compound that is liquid at atmospheric pressure and 25°C and is miscible with water. Examples of such compounds include amides such as 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; and ketones such as acetone and methyl ethyl ketone. These compounds may be used alone or in combination of two or more. When two or more of the above-mentioned compounds are used as the liquid medium other than water, they are preferably mutually miscible.

[0030] The water content in the electrodeposition solution is preferably 25% by mass or more, more preferably 40% by mass or more. The water content is preferably less than 70% by mass, more preferably 65% ​​by mass or less. The water content in the electrodeposition solution is preferably 10 to 250% by mass, more preferably 60 to 180% by mass, relative to the F particle content.

[0031] The electrodeposition solution may further contain an electrodeposition aid, and preferably does. Examples of the electrodeposition aid include basic compounds such as tripropylamine, dibutylamine, piperidine, and triethylamine; amino derivatives of (meth)acrylic acid such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, (meth)acryloyloxyethyl trimethylammonium chloride, N-tert-butylaminoethyl (meth)acrylate, and morpholinoethyl (meth)acrylate; hydroxy derivatives of (meth)acrylic acid such as 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate; and (co)polymers thereof. In this specification, "(meth)acrylic" is a general term that refers to acrylic, methacrylic, and both. "(Meth)acryloyloxy" is a term that collectively refers to acryloyloxy, methacryloyloxy, and both. When an electrodeposition auxiliary is contained, the amount thereof is preferably 0.1 to 3 mass % based on the total amount of the electrodeposition solution.

[0032] The electrodeposition solution may further contain a cellulose ether. Examples of cellulose ethers include carboxyalkyl celluloses such as carboxymethyl cellulose; hydroxyalkyl celluloses such as hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; and hydroxyalkyl alkyl celluloses such as hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl ethyl cellulose, and hydroxyethyl ethyl methyl cellulose. These may be used alone or in combination of two or more. Among these, hydroxyalkyl cellulose or hydroxyalkyl alkyl cellulose is preferred, hydroxyalkyl cellulose is more preferred, and hydroxyethyl cellulose is even more preferred.

[0033] The degree of substitution of the cellulose ether is preferably 1.4 or more, more preferably 2.1 or more. The degree of substitution of the cellulose ether is preferably 2.9 or less, more preferably 2.7 or less. The "degree of substitution" of the cellulose ether, also referred to as the degree of etherification, represents the average number of hydroxyl groups substituted with alkoxyl groups among the three hydroxyl groups on the glucose ring of cellulose. The degree of substitution is calculated by converting the value measured by the method for analyzing the degree of substitution of hydroxypropyl methylcellulose described in the 18th edition of the Japanese Pharmacopoeia. The weight average molecular weight of the cellulose ether is preferably 1,000 to 10,000. Specific examples of cellulose ethers 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.). When the present electrodeposition liquid further contains cellulose ether, the content thereof is preferably 0.01 to 0.1 mass % relative to the present electrodeposition liquid, from the viewpoint of improving the fluidity of the present electrodeposition liquid.

[0034] The present electrodeposition liquid may further contain an inorganic filler, in which case the electrodeposition film formed from the present electrodeposition liquid is likely to have excellent electrical properties and low linear expansion. The shape of the inorganic filler may be any of spherical, needle-like (fibrous), and plate-like, and specifically may be 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. Examples of inorganic fillers include silicon compounds such as quartz powder, silica, wollastonite, talc, silicon nitride, silicon carbide, and mica; nitrogen compounds such as boron nitride and aluminum nitride; metal oxides such as aluminum oxide, zinc oxide, titanium oxide, cerium oxide, beryllium oxide, magnesium oxide, nickel oxide, vanadium oxide, copper oxide, iron oxide, and silver oxide; carbon fibers; carbon allotropes such as graphite, graphene, and carbon nanotubes; and metals such as silver and copper. One type of inorganic filler may be used, or two or more types may be used in combination. The D50 of the inorganic filler is preferably 0.1 to 50 μm. The surface of the inorganic filler may be surface-treated with a silane coupling agent. When the present electrodeposition liquid contains an inorganic filler, the content of the inorganic filler in the present electrodeposition liquid is preferably 1 to 25 mass %.

[0035] The electrodeposition solution may further contain additives such as a thixotropic agent, a viscosity modifier, an antifoaming 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, and a flame retardant.

[0036] This electrodeposition solution is obtained by mixing F particles, a nonionic surfactant having a hydroxyl group, water, and, if necessary, other liquid media, other resins, cellulose ether, inorganic fillers, additives, etc., as described above. The electrodeposition solution may be obtained by mixing the F particles, the nonionic surfactant having a hydroxyl group, and water all at once, or by mixing them separately one by one, or by preparing a master batch of these components in advance and mixing this with the remaining components. There are no particular restrictions on the order of mixing, and the mixing method may be either mixing all at once or mixing in multiple batches. For example, it is preferable from the viewpoint of improving dispersibility to preliminarily disperse the F particles in a portion of the water, then sequentially add and mix a nonionic surfactant having a hydroxyl group, and then add the resulting mixture to the remaining water to obtain the present electrodeposition solution. The nonionic surfactant having a hydroxyl group may be added as it is or in the form of an aqueous solution. The cellulose ether may be added as a powder or an aqueous solution thereof, or may be added in a state dispersed or dissolved in a liquid defoaming agent or the like. Furthermore, when other liquid media, other resins, cellulose ethers, inorganic fillers, additives, etc. are further mixed as needed, they may be mixed when the F particles are mixed with water, or they may be mixed when the mixture is added to water.

[0037] Examples of mixing devices for obtaining the present electrodeposition solution include agitators equipped with blades such as a Henschel mixer, pressure kneader, Banbury mixer, and planetary mixer; grinding devices equipped with media such as a ball mill, attritor, basket mill, sand mill, sand grinder, Dyno Mill, Dispermat, SC Mill, spike mill, and agitator mill; and dispersing devices equipped with other mechanisms such as a microfluidizer, nanomizer, ultimizer, ultrasonic homogenizer, dissolver, disper, high-speed impeller, thin film swirling high-speed mixer, planetary mixer, and V-type mixer.

[0038] The viscosity of the electrodeposition solution is preferably 10 to 10,000 mPa·s, more preferably 100 to 3,000 mPa·s. In this case, the electrodeposition solution can easily form an electrodeposited film of any desired thickness. Furthermore, when the electrodeposition solution has a viscosity in this range, the physical properties of the F polymer are likely to be highly expressed in the electrodeposited film formed from the solution. The thixotropy ratio of the present electrodeposition solution is preferably 1.0 to 3.0, in which case the present electrodeposition solution has excellent homogeneity and is likely to produce a denser electrodeposition film.

[0039] From the viewpoints of improving long-term storage stability and accelerating electrodeposition, the pH of the present electrodeposition solution is more preferably 8 to 10. The pH of the present electrodeposition solution can be adjusted with a pH adjuster (ammonia, citric acid, etc.) or a pH buffer (tris(hydroxymethyl)aminomethane, ethylenediaminetetraacetic acid, ammonium hydrogencarbonate, ammonium carbonate, ammonium acetate, etc.).

[0040] An insulating coating containing an F polymer can be produced by immersing a conductor and a counter electrode in this electrodeposition solution, applying a voltage between the conductor and the counter electrode, and forming an insulating coating on the conductor as an electrodeposited film. In other words, it is preferable to form an electrodeposited film on the surface of a conductor using this electrodeposition solution by electrodeposition, and then dry and bake the resulting film to form an insulating coating containing an F polymer on the surface of the conductor. The electrodeposition method may be either anionic electrodeposition or cationic electrodeposition.

[0041] Examples of conductors include conductive metal materials such as metal foils of copper, nickel, aluminum, titanium, alloys thereof, etc. The shape of the conductor may be linear, flat, curved, or irregular. The shape of the conductor may be any of foil, plate, film, and fiber, or may be a circular, flat, or rectangular metal wire (such as a rectangular copper wire), a flat conductive plate, or other metal plate. The ten-point average roughness of the surface of the conductor is preferably 0.01 to 0.05 μm. It is preferable to remove oil and grease and oxide film from the surface of the conductor in advance using an organic solvent, a surfactant, or the like.

[0042] For example, when forming an electrodeposited film on the surface of a conductor by an anionic electrodeposition method, the conductor and a counter electrode are immersed in the electrodeposition solution, and a DC voltage is applied between the conductor as the anode and the counter electrode as the cathode. The temperature of the electrodeposition solution (liquid temperature) is preferably adjusted to a range of 5 to 40°C from the viewpoints of preventing condensation and maintaining storage stability. The voltage applied between the conductor (anode) and the counter electrode (cathode) is preferably in the range of 0.5 V to 600 V, from the viewpoints of the electrodeposition rate, suppressing the generation of bubbles on the conductor surface, and easily obtaining an insulating coating with excellent surface appearance and film thickness uniformity. The voltage application time varies depending on the thickness of the electrodeposited film to be formed, and can usually be appropriately selected in the range of 0.01 to 300 seconds.

[0043] The conductor with the electrodeposited film formed on its surface is dried to remove the water-containing liquid medium, and then baked to form an insulating film containing an F polymer on the conductor. The heating for removing the water-containing liquid medium is preferably carried out at 100 to 200°C for 0.1 to 30 minutes. The water-containing liquid medium does not need to be completely removed during heating; it is sufficient to remove it to the extent that the layer formed by packing of the F particles can maintain a self-supporting film. Furthermore, during heating, air may be blown onto the surface to aid in the removal of the liquid dispersion medium by air drying. The heating for baking the F polymer is preferably carried out at a temperature equal to or higher than the melting point of the F polymer, more preferably at 360 to 400° C. for 0.1 to 30 minutes. Heating devices for each heating method include ovens and ventilation drying furnaces. The heat source in the device may be a contact type heat source (hot air, hot plate, etc.) or a non-contact type heat source (infrared rays, etc.). The heating may be carried out under normal pressure or under reduced pressure. The atmosphere during each heating step may be either an air atmosphere or an inert gas atmosphere (helium gas, neon gas, argon gas, nitrogen gas, etc.).

[0044] The thickness of the electrodeposited film formed from the present electrodeposition solution is preferably 1 to 100 μm. The dielectric constant of the electrodeposited film formed from this electrodeposition solution is preferably 2.4 or less, more preferably 2.0 or less. The dielectric constant is preferably greater than 1.0, and the relative dielectric constant is preferably 1.1 to 2.4. The dielectric dissipation factor of the electrodeposited film is preferably 0.0022 or less, more preferably 0.0020 or less. The dielectric dissipation factor is preferably greater than 0.0010. The thermal conductivity of the electrodeposited film is preferably 1 W / m K or more, more preferably 3 W / m K or more. By this method, a conductor with an insulating coating can be obtained, which has a conductor and an insulating coating that is an electrodeposited film containing 30% by mass or more of an F polymer and that covers at least a portion of the conductor.

[0045] The present invention also relates to a conductor with an insulating coating, which comprises a conductor and an insulating coating that covers at least a portion of the conductor, and the insulating coating is an electrodeposited film formed using the present electrodeposition liquid and containing 30% by mass or more of an F polymer. The details of the conductor, the insulating coating, and the method for forming the insulating coating using the electrodeposition liquid are the same as those of the conductor, the insulating coating, and the method for forming the insulating coating described above.

[0046] The electrodeposition solution is useful as a material capable of forming an insulating coating having insulating properties, heat resistance, corrosion resistance, chemical resistance, water resistance, impact resistance, and thermal conductivity. Specifically, this electrodeposition solution can be used in printed wiring boards, thermal interface materials, power module substrates, coils used in power devices such as motors, automotive engines, heat exchangers, vials, syringes, ampoules, medical wire, secondary batteries such as lithium-ion batteries, primary batteries such as lithium batteries, radical batteries, solar cells, fuel cells, lithium-ion capacitors, hybrid capacitors, capacitors (aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc.), electrochromic elements, electrochemical switching elements, electrode binders, electrode separators, and electrodes (positive and negative electrodes).

[0047] Conductors with insulating coatings formed from the present electrodeposition solution are useful for antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry products, heat dissipation parts, etc.

[0048] Specifically, coated electric wires such as aircraft wires, which have an insulating coating containing F polymer on the surface of a conductor such as copper wire (especially rectangular wire), coated enameled wire used in motors for electric vehicles, etc., electronic substrate materials such as rigid printed wiring boards, electrode binders (for lithium secondary batteries, fuel cells, etc.), copy rolls, furniture, automobile dashboards, covers for home appliances, etc., sliding parts (load bearings, yaw bearings, sliding shafts, valves, bearings, bushings, seals, thrust washers, wear rings, pistons, slide switches, gears, cams, belt conveyors, food transport belts, etc.), wear parts for centrifugal pumps, chemical and water supply pumps, tools (shovels, files, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, dies, toilets, container coating materials, heat dissipation substrates for mounting power devices, heat dissipation materials for wireless communication devices, transistors, thyristors, rectifiers, transformers, power MOS It is useful for 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 materials, interior and exterior parts of automobiles, sealing materials for processing machines and vacuum ovens that perform heat treatment under low oxygen conditions, plasma processing equipment, etc., heat dissipation parts in processing units for sputtering and various dry etching equipment, etc., and electromagnetic wave shielding.

[0049] The present electrodeposition liquid, the method for producing an insulating coating, and the conductor with an insulating coating have been described above, but the present invention is not limited to the configurations of the above-described embodiments. For example, the present electrodeposition liquid and the conductor with an insulating coating may have any other components added to the configurations of the above-described embodiments, or may be replaced with any other components that exhibit similar functions. Furthermore, the method for producing an insulating coating using the present electrodeposition liquid may have any other components added to the configurations of the above-described embodiments, or may be replaced with any other components that exhibit similar functions. [Example]

[0050] 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 ingredient [Resin component] "F polymer particles" 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 Tetrafluoroethylene polymer particles (melting temperature: 300°C) with 1000 particles per particle (D50: 2.0 μm) F Particle 2: Particles (D50: 2.7 μm) made of a tetrafluoroethylene-based polymer (melting temperature: 300°C) containing 97.5 mol% TFE units and 2.5 mol% PPVE units, in that order, and having no oxygen-containing polar groups. [Nonionic surfactants] Agent 1: A nonionic silicone surfactant with a polysiloxane chain in the main chain and polyethylene oxide groups (terminated with hydroxyl groups) in the side chains, with an HLB value of 13. Agent 2: A fluorosurfactant without a hydroxyl group, which is a homopolymer of CH2=C(CH3)C(O)OCH2CH2(CF2)6F

[0051] 2. Example of electrodeposition solution production [Example 1] F particles 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 to obtain electrodeposition solution 1 (viscosity: 30 mPa s) containing F particles 1 (40 parts by mass), surfactant 1 (5 parts by mass), and water (55 parts by mass).

[0052] [Example 2]~[Example 6] Electrodeposition Solutions 2 to 6 were obtained in the same manner as in Example 1, except that the types and amounts of the resin component, surfactant, and liquid medium were changed as shown in Table 1. In Example 4, N-methylpyrrolidone (NMP) was also used as the liquid medium, and in Example 6, polyimide was also used as the resin component.

[0053] [Table 1]

[0054] 3. Evaluation 3-1. Manufacturing and evaluation of insulating coating Each electrodeposition solution was stored in an electrodeposition tank, and the temperature of the electrodeposition solution in the electrodeposition tank was set to 20°C. Next, a rectangular copper wire (conductor) measuring 500 mm in length, 50 mm in width, and 2 mm in height was used as the anode, and a cylindrical copper plate inserted into the electrodeposition solution in the electrodeposition tank was used as the cathode. A DC voltage of 100 V was applied between the rectangular copper wire and the cylindrical copper plate, and the copper plate was held in the electrodeposition solution in the electrodeposition tank for 30 seconds (electrodeposition process). This resulted in an electrodeposition film being formed on the surface of the rectangular copper wire. Next, the rectangular copper wire with the electrodeposition film formed thereon was placed in a drying furnace at 300°C for 5 minutes for drying treatment, and the electrodeposition film was baked to obtain a rectangular copper wire with a 40 μm thick insulating film formed on its surface (baking process).

[0055] The behavior during the electrodeposition and baking steps was evaluated according to the following criteria. <Evaluation criteria for process behavior> A: No powder falls off from the electrodeposited film after the electrodeposition process, and drying can be performed quickly. B: Powder falling off from the electrodeposited film after the electrodeposition process is observed, but it can be dried quickly. C: No powder falls off from the electrodeposited film after the electrodeposition process, but the drying process takes time and powder falls off from the electrodeposited film during the drying process. The state of the rectangular copper wire on which the insulating coating was formed was evaluated according to the following criteria. <Insulation coating evaluation criteria> A: The entire surface and end faces of the rectangular copper wire are smoothly covered, and the wire is highly resistant to cracks caused by bending. B: The entire surface and end faces of the rectangular copper wire are smoothly covered, but the crack resistance caused by bending the rectangular copper wire is poor. C: Defects have occurred on the end surface of the rectangular copper wire, and the resistance to cracks caused by bending the rectangular copper wire is poor. The above results are summarized in Table 2.

[0056] [Table 2] [Industrial Applicability]

[0057] The electrodeposition solution of the present invention has excellent dispersion stability and ease of handling. It also highly exhibits the physical properties of the F polymer and can form an insulating coating (electrodeposited film) with excellent surface appearance.

Claims

1. An electrodeposition liquid comprising a resin component having a tetrafluoroethylene polymer particle content of 30% by mass or more, a nonionic surfactant having a hydroxyl group, and a liquid medium having a water content of 50% by mass or more.

2. 2. The electrodeposition solution according to claim 1, wherein the tetrafluoroethylene-based polymer is heat-fusible and contains an oxygen-containing polar group.

3. 2. The electrodeposition solution according to claim 1, wherein the average particle size of the tetrafluoroethylene polymer particles is 1 μm or more and less than 10 μm.

4. 2. The electrodeposition solution according to claim 1, wherein the proportion of the tetrafluoroethylene polymer particles in the resin component is 30 to 100% by mass.

5. 2. The electrodeposition solution according to claim 1, wherein the content of the tetrafluoroethylene-based polymer particles is 30 to 90% by mass.

6. 2. The electrodeposition solution according to claim 1, wherein the content of the nonionic surfactant having a hydroxyl group is in the range of 1 to 15% by mass relative to the particles of the tetrafluoroethylene-based polymer.

7. 2. The electrodeposition solution according to claim 1, wherein the HLB value of the nonionic surfactant having a hydroxyl group calculated by the Griffin equation is 3 to 16.

8. 2. The electrodeposition solution according to claim 1, wherein the nonionic surfactant having a hydroxyl group is a silicone-based surfactant or an acetylene diol-based surfactant.

9. 2. The electrodeposition solution according to claim 1, wherein the nonionic surfactant having a hydroxyl group is a nonionic surfactant containing no fluorine atoms.

10. 2. The electrodeposition solution according to claim 1, wherein the proportion of water in the liquid medium is 80 to 100 mass %.

11. The electrodeposition solution according to claim 1 , further comprising an electrodeposition auxiliary.

12. 2. The electrodeposition solution according to claim 1, wherein the viscosity is 10 to 10,000 mPa·s.

13. A method for producing an insulating coating, comprising immersing a conductor and a counter electrode in the electrodeposition solution according to any one of claims 1 to 12, and applying a voltage between the conductor and the counter electrode to form an insulating coating on the conductor.

14. A conductor with an insulating coating, comprising a conductor and an insulating coating that covers at least a portion of the conductor, wherein the insulating coating is formed using the electrodeposition solution according to any one of claims 1 to 12 and contains 30% by mass or more of a tetrafluoroethylene-based polymer.

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