Pretreatment agent for manufacturing electrolytic capacitor and method for manufacturing electrolytic capacitor in which the same is used

Abstract

Provided are: a pretreatment agent for manufacturing an electrolytic capacitor in which a pretreatment agent layer is formed on a positive electrode of the electrolytic capacitor, said pretreatment agent for manufacturing an electrolytic capacitor being characterized by containing an N-vinyl lactam polymer or an acrylamide polymer, the polymer being dissolved in a range of 0.1–5 mass% in a solvent that contains one or more substances selected from the group consisting of water, ethanol, methanol and isopropyl alcohol; a pretreatment agent for manufacturing an electrolytic capacitor that has excellent LC characteristics and does not adversely affect ESR, by using said pretreatment agent and a method for manufacturing an electrolytic capacitor in which said pretreatment agent is used; and a method for manufacturing an electrolytic capacitor in which said pretreatment agent is used.

Description

Pretreatment Agent for Manufacturing Electrolytic Capacitor and Method for Manufacturing Electrolytic Capacitor Using the Same

[0001] The present invention relates to a pretreatment agent for manufacturing an electrolytic capacitor and a method for manufacturing an electrolytic capacitor using the pretreatment agent.

[0002] Electrolytic capacitors can be broadly classified into types using an electrolytic solution and types using a solid electrolyte. As electrolytic capacitors using an electrolytic solution, those in which a solution obtained by dissolving an organic acid, an inorganic acid or salts thereof as an electrolyte in an organic solvent is generally used as the electrolytic solution. On the other hand, a solid electrolytic capacitor using a solid electrolyte generally has a solid electrolyte layer containing a conductive polymer functioning as a cathode formed on an anode having a dielectric oxide film. There also exist hybrid electrolytic capacitors that combine the characteristics of both types. As for the performance of electrolytic capacitors, not only reduction in equivalent series resistance (ESR) characteristics but also low leakage current (LC) is required for improving reliability.

[0003] In order to reduce ESR and LC, Patent Document 1 discloses a solid electrolytic capacitor in which an anode having a dielectric oxide film is pretreated with a pretreatment agent before forming a solid electrolyte layer on the anode having the dielectric oxide film, and then the solid electrolyte layer is formed. A gelling agent is used as the pretreatment agent, and examples thereof include polyvinylpyrrolidone (PVP), polyacrylamide (PAM), fine particle silica, fine particle alumina, fine particle titanium, agar, gelatin, carrageenan, karaya gum, alginic acid, sodium alginate, cellulose, polyvinyl alcohol, polystyrene sulfonic acid or salts thereof, polyethylene glycol, polyacrylic acid or salts thereof, starch, carboxymethyl cellulose or salts thereof, hydrophilic polymers such as hydrophilic polyurethane, and the like.

[0004] Patent Document 2 describes a solid electrolytic capacitor comprising a dielectric layer (dielectric oxide film) on a valve metal (anode) having an oxide film repair layer capable of forming an oxide film, followed by a solid electrolyte layer, a graphite paste layer, and a silver paste layer. A conductive polymer and a gelling agent are used to form the oxide film repair layer, and examples of gelling agents include PVP, sodium polyacrylate, polyvinylidene fluoride, polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and their derivatives.

[0005] International Publication No. 2023 / 171344, Japanese Patent Publication No. 2014-045115

[0006] As described in Patent Documents 1 and 2 above, in solid electrolytic capacitors in which a pretreatment layer or oxide film repair layer is formed on an anode having a dielectric oxide film using a particularly water-soluble polymer as a gelling agent, depending on the type of water-soluble polymer, the LC reduction effect may not be obtained, or even if the LC reduction effect is obtained, the ESR may increase. Therefore, it was necessary to select the water-soluble polymer and optimize its application conditions. Accordingly, the present invention provides a pretreatment agent for manufacturing electrolytic capacitors that have excellent LC characteristics and do not adversely affect the ESR, and a method for manufacturing electrolytic capacitors using the pretreatment agent.

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the above problems can be solved by using a pretreatment agent for manufacturing electrolytic capacitors, in which a specific water-soluble polymer (polymer in the present invention) is dissolved in a predetermined amount in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, in order to form a good pretreatment layer on the anode having a dielectric oxide film that constitutes an electrolytic capacitor. This led to the completion of the present invention.

[0008] In other words, the present invention is as follows: [1] A pretreatment agent for manufacturing electrolytic capacitors, which forms a pretreatment layer on the anode of an electrolytic capacitor, comprising an N-vinyl lactam polymer or an acrylamide polymer, wherein the polymer is dissolved in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol in an amount of 0.1% by mass or more and 5% by mass or less. [2] The pretreatment agent for manufacturing electrolytic capacitors according to [1], wherein the weight-average molecular weight of the polymer is 40,000 or more and 1,300,000 or less. [3] The pretreatment agent for manufacturing electrolytic capacitors according to [1] or [2], wherein the viscosity of the pretreatment agent at 25°C is 1 mPa·s or more and 100 mPa·s or less. [4] A method for manufacturing an electrolytic capacitor, comprising at least the steps of forming a pretreatment layer on the anode having a dielectric oxide film of an electrolytic capacitor element, and then forming a conductive solid layer on the pretreatment layer, wherein the step of forming the pretreatment layer is characterized in that a pretreatment agent for manufacturing an electrolytic capacitor is formed by applying a pretreatment agent for manufacturing an electrolytic capacitor, which is obtained by dissolving an N-vinyllactam polymer or an acrylamide polymer in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol in an amount of 0.1% by mass or more and 5% by mass or less, onto the anode of an electrolytic capacitor element, and then removing the solvent of the pretreatment agent to form a pretreatment layer on the anode. [5] The method for manufacturing an electrolytic capacitor according to [4], wherein the viscosity of the pretreatment agent at 25°C is 1 mPa·s or more and 100 mPa·s or less. [6] The method for manufacturing an electrolytic capacitor according to [4] or [5], wherein the weight-average molecular weight of the N-vinyllactam polymer or acrylamide polymer in the pretreatment agent is 40,000 or more and 1,300,000 or less. [7] The method for manufacturing an electrolytic capacitor according to [4], characterized in that the electrolytic capacitor element is a capacitor element in which an anode foil and a counter cathode foil are wound with a separator in between.[8] The method for manufacturing an electrolytic capacitor according to [4], characterized in that the step of forming the conductive solid layer is a step of using an oxidizing agent solution containing a monomer compound and a dopant to chemically oxidize and polymerize in a capacitor element to form a conductive solid layer made of a conductive polymer.

[0009] By selecting a polymer in the pretreatment agent for electrolytic capacitor manufacturing according to the present invention and optimizing its application conditions, it is possible to manufacture electrolytic capacitors with excellent LC characteristics and no adverse effects on ESR by using this pretreatment agent.

[0010] The pretreatment agent for manufacturing electrolytic capacitors of the present invention (hereinafter referred to as "the pretreatment agent of the present invention") is for forming a pretreatment layer on the anode of an electrolytic capacitor. The pretreatment agent of the present invention comprises an N-vinyl lactam polymer or an acrylamide polymer, wherein the polymer is dissolved in a solvent containing 0.1% to 5% by mass (hereinafter simply referred to as "%) of water, ethanol, methanol, and isopropyl alcohol, one or more of which are selected from the group.

[0011] First, the pretreatment agent of the present invention will be described. The polymer contained in the pretreatment agent of the present invention includes an N-vinyl lactam polymer or an acrylamide polymer.

[0012] First, the N-vinyllactam polymer used in the present invention will be described. The N-vinyllactam polymer used in the present invention is represented by formula (1). In equation (1), X represents an integer between 3 and 5, and R １ The symbol represents a methylene group. n is an integer greater than or equal to 100.

[0013] In the above formula (1), R １ The methylene group having 3 to 5 carbon atoms represented by formula (1) specifically includes trimethylene, tetramethylene, and pentamethylene groups. Furthermore, both or one end of the polymer represented by formula (1) may be hydrogen atoms or functionalized groups. Examples of functional groups include carboxyl, methyl, amino, hydroxyl, and amine groups.

[0014] Examples of polymers represented by formula (1) include polyvinylpyrrolidone, polyvinylpiperidone, polyvinylcaprolactam, carboxyl-terminated polyvinylpyrrolidone, and amine-terminated polyvinylpyrrolidone. Among these, polyvinylpyrrolidone is preferred. These polymers can be synthesized by well-known methods or commercially available products. Examples of commercially available products include reagents from Sigma-Aldrich, and industrial-grade products from Nippon Shokubai Co., Ltd. and Daiichi Kogyo Seiyaku Co., Ltd.

[0015] Next, the acrylamide polymer used in the present invention will be described. The acrylamide polymer used in the present invention is represented by formula (2). In formula (2), R ２ , R ３ Each of these atoms may be independent and may be a hydrogen atom or a branched alkyl group having 1 to 3 carbon atoms. m is an integer greater than or equal to 100.

[0016] R in equation (2) ２ , R ３ Specific alkyl groups in formula (2) include methyl, ethyl, propyl, and isopropyl groups. Furthermore, both or one end of the polymer represented by formula (2) may be hydrogen atoms or functionalized groups. Examples of functional groups include carboxyl, methyl, amino, hydroxyl, and amine groups.

[0017] Examples of polymers represented by formula (2) include polyacrylamide, poly(N-methylacrylamide), poly(N-ethylacrylamide), poly(N-propylacrylamide), poly(N-isopropylacrylamide), poly(N,N-dimethylacrylamide), poly(N,N-diethylacrylamide), poly(N,N-dipropylacrylamide), poly(N,N-diisopropylacrylamide), carboxyl-terminated poly(N-isopropylacrylamide), and amine-terminated poly(N-isopropylacrylamide). Among these, poly(N-isopropylacrylamide) and carboxyl-terminated poly(N-isopropylacrylamide) are preferred. These polymers can be synthesized by well-known methods or commercially available products. Examples of commercially available products include reagents from Sigma-Aldrich and industrial-grade products from Mitsui Chemicals, Inc.

[0018] The polymer content in the above pretreatment agent is 0.1% to 5%, preferably 0.1% to 2%. This content allows for a greater reduction in LC when used in electrolytic capacitors. If the polymer content is less than 0.1%, the reduction in LC when used in electrolytic capacitors may not be achieved, and if it is more than 5%, both ESR and LC will increase.

[0019] The molecular weight of the N-vinyl lactam polymer or acrylamide polymer is not particularly limited, but is, for example, 1,000 or more to 1,500,000 or less, preferably 40,000 or more to 1,300,000 or less. By using this molecular weight, when manufacturing an electrolytic capacitor using a capacitor element having a dielectric oxide film on the anode, a uniform pretreatment layer can be formed covering the dielectric oxide film, and the dielectric oxide film can be sufficiently coated with the polymer, thus achieving a greater LC reduction effect when an electrolytic capacitor is made. If the molecular weight of the polymer is less than 1,000, the film-forming ability is poor when forming the pretreatment layer, and a uniform pretreatment layer covering the dielectric oxide film cannot be formed. If it is greater than 1,500,000, the viscosity increases when preparing the pretreatment agent, resulting in low impregnation into the element and insufficient coating of the dielectric oxide film with the polymer, thus failing to achieve an LC reduction effect. This molecular weight is the weight-average molecular weight and can be measured, for example, by gel permeation chromatography (GPC).

[0020] The above pretreatment agent further comprises a solvent. The solvent is one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol. Of these solvents, water is preferably used.

[0021] The above pretreatment agent may contain other additives besides polymers in appropriate amounts, as long as they do not impair the effects of the present invention. Examples of other additives include surface modifiers, leveling agents, defoamers, dispersants, surfactants, surface activators, viscosity modifiers, and the like.

[0022] The viscosity of the pretreatment agent described above is not particularly limited, but for example, it is 1 mPa·s or more and 1,000 mPa·s or less, preferably 1 mPa·s or more and 100 mPa·s or less, more preferably 1 mPa·s or more and 80 mPa·s or less, and even more preferably 1 mPa·s or more and 10 mPa·s or less. By setting the viscosity to this level, when manufacturing an electrolytic capacitor using a capacitor element having a dielectric oxide film on the anode, it becomes possible to sufficiently impregnate the capacitor element with the polymer, and an LC reduction effect can be obtained. If the viscosity of the pretreatment agent is less than 1 mPa·s, the film-forming ability is poor when forming the pretreatment agent layer, and it is not possible to form a uniform pretreatment agent layer covering the dielectric oxide film. If it is higher than 1,000 mPa·s, the impregnation ability into the element is low, and it is not possible to sufficiently coat the dielectric oxide film with the polymer, so the LC reduction effect cannot be obtained. This viscosity is at 25°C and can be measured, for example, using a viscometer. The viscosity of this pretreatment agent can be adjusted by using multiple types of solvents or other additives.

[0023] The pretreatment agent of the present invention can be manufactured by mixing a polymer with a solvent. The temperature of the solution during the manufacture of the pretreatment agent is not particularly limited as long as it is a temperature at which the polymer dissolves uniformly in the solvent without thermal decomposition or denaturation, but it is preferably between 10 and 90°C.

[0024] The pretreatment agent of the present invention forms a pretreatment layer on an anode having a dielectric oxide film that constitutes an electrolytic capacitor in a method for manufacturing electrolytic capacitors. The method for forming the pretreatment layer on an anode having a dielectric oxide film using the pretreatment agent of the present invention is not particularly limited, but the pretreatment agent can be applied, sprayed, impregnated, etc., to the anode having a dielectric oxide film, and then dried to form the pretreatment layer on the dielectric oxide film of the anode. In the case of a capacitor element in which an anode foil having a dielectric oxide film and an opposing cathode foil are wound with a separator in between, the pretreatment agent can be brought into contact with the entire capacitor element and dried, in which case a pretreatment layer will be formed on the capacitor element.

[0025] A specific method for manufacturing an electrolytic capacitor using the pretreatment agent of the present invention includes at least the steps of forming a pretreatment agent layer on a capacitor element in which an anode foil having a dielectric oxide film and a counter cathode foil are wound with a separator in between, and then forming a conductive solid layer on the pretreatment agent layer, wherein the step of forming the pretreatment agent layer includes at least the step of forming a pretreatment agent layer on the anode by attaching the pretreatment agent of the present invention to the anode of the electrolytic capacitor element and then removing the solvent of the pretreatment agent, and optionally further including an electrolyte impregnation step of impregnating the gaps of the conductive solid layer with an electrolyte.

[0026] The above manufacturing method can be rephrased as follows: A capacitor element in which an anode foil having a dielectric oxide film and an opposing cathode foil are wound with a separator in between, comprises at least the steps of: (a) applying the pretreatment agent of the present invention to the anode of the capacitor element, and then removing the solvent of the pretreatment agent to form a pretreatment agent layer on the anode; and (b) forming a conductive solid layer on the pretreatment agent layer after the pretreatment agent formation step, and optionally further (c) impregnation of the conductive solid layer with an electrolyte solution.These manufacturing methods will now be explained.

[0027] [Anode with Dielectric Oxide Film Formed] Examples of anodes include aluminum, tantalum, niobium, and titanium. The anode can be used in the form of a sintered body formed by sintering fine particles, or in the form of a foil or plate that has been roughened by etching or the like. Among these anodes, foil-shaped aluminum that has been roughened by etching or the like is extremely preferred because it easily exhibits the effects of the present invention.

[0028] A dielectric oxide film can be formed on the surface of the anode by applying a known chemical conversion treatment to the anode. For example, a dielectric oxide film can be formed by performing anodic oxidation treatment by electrolysis in an aqueous solution of diammonium adipate or the like.

[0029] When using a wound-type capacitor element, lead terminals are attached to the anode and to the opposing cathode made of aluminum foil. These lead-terminal-equipped anode and cathode are then placed opposite each other via a separator and wound to create the capacitor element.

[0030] [(a) Step of forming a pretreatment layer] As a method of forming a pretreatment layer on an anode having a dielectric oxide film using the above pretreatment agent, for example, the pretreatment agent can be brought into contact with a capacitor element, dried, and a portion of the solvent removed to form a pretreatment layer on an anode having a dielectric oxide film. Any method of contact is acceptable, but a preferred method is to immerse the capacitor element in the pretreatment agent of the present invention. Furthermore, forming a pretreatment layer as described herein includes a state in which the polymer contained in the pretreatment agent is supported in a layer on part or all of the surface of the dielectric oxide film on an anode having a dielectric oxide film, or a state in which a pretreatment layer consisting of the polymer contained in the pretreatment agent is formed on part or all of the surface of the dielectric oxide film.

[0031] The process of immersing the capacitor element in the above-mentioned pretreatment agent, removing it, and drying it may be repeated multiple times.

[0032] Drying can be done by natural drying at room temperature or by heating, but it is preferable to dry by heating to 80°C or higher.

[0033] As a more specific example of the process, one can cite the step of immersing a capacitor element in the pretreatment agent of the present invention for 30 seconds, followed by drying it at 125°C for 30 minutes.

[0034] After performing step (a) above, the next step is to (b) form a conductive solid layer on the pretreatment layer.

[0035] [(b) Step of forming a conductive solid layer on a pretreatment layer] Next, the step of forming a conductive solid layer is described below. The step of forming a conductive solid layer may be performed not only by a chemical oxidation polymerization method in which an oxidizing agent solution containing a monomer compound and a dopant is brought into contact on the anode, but also by known electropolymerization methods or by a known conductive polymer dispersion being attached to a capacitor element and dried to form a conductive solid layer.

[0036] Preferably, after bringing an oxidizing agent solution containing a monomer compound and a dopant into contact with the anode on which the pretreatment agent layer has been formed, chemical oxidative polymerization is performed in the capacitor element, thereby producing a capacitor element in which a conductive solid layer made of a conductive polymer is formed on the anode on which the pretreatment agent layer has been formed. The contacting method may be any arbitrary method, and examples thereof include a method of impregnating the anode in a monomer solution and then further impregnating it in an oxidizing agent solution containing a dopant, and a method of immersing the anode in a polymerization solution containing a monomer compound, a dopant and an oxidizing agent; the method of immersing the anode in a polymerization solution containing a monomer compound, a dopant and an oxidizing agent is preferred.

[0037] That is, a preferred example includes a step of immersing the anode with the pretreatment agent layer formed thereon in the above-described oxidizing agent solution containing the monomer compound and the dopant, pulling the anode out, then heating it to perform chemical oxidative polymerization in the capacitor element, thereby forming the conductive solid layer made of a conductive polymer.

[0038] The step of immersing the anode having a dielectric oxide film in the above-described oxidizing agent solution containing the monomer compound and the dopant, pulling the anode out, and then drying it may be repeated a plurality of times.

[0039] [Conductive Solid Layer] The conductive polymer used in the step of forming the conductive solid layer is preferably a polymer doped with a dopant. The monomer compound used for producing the polymer is not particularly limited, and for example, pyrroles, thiophenes, anilines and the like can be used. Due to its excellent conductivity, a thiophene compound represented by the following general formula (3) is more preferred.

[0040] General Formula (3)

[0041] In the above general formula (3), R ４ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and each Y represents an oxygen atom or a sulfur atom which may be the same or different.

[0042] Specific examples of thiophene compounds represented by the above general formula (3) include 3,4-ethylenedioxythiophene, methyl-3,4-ethylenedioxythiophene, ethyl-3,4-ethylenedioxythiophene, propyl-3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, methyl-3,4-propylenedioxythiophene, ethyl-3,4-propylenedioxythiophene, propyl-3,4-propylenedioxythiophene, 3,4-ethylenedithiathiophene, methyl-3,4-ethylenedithiathiophene, ethyl-3,4-ethylenedithiathiophene, propyl-3,4-ethylenedithiathiophene, 3,4-propylenedithiathiophene, methyl-3,4-propylenedithiathiophene, ethyl-3,4-propylenedithiathiophene, and propyl-3,4-propylenedithiathiophene. In the name of the above thiophene compounds, the descriptions such as methyl-, ethyl-, and propyl- at the beginning of the name refer to R in the above formula (3) ４ which is a substituent.

[0043] Among these, 3,4-ethylenedioxythiophene (EDOT), methyl-3,4-ethylenedioxythiophene, and ethyl-3,4-ethylenedioxythiophene are particularly preferred, especially from the viewpoint of excellent electrical properties in electrolytic capacitors.

[0044] The conductive polymer can be obtained by chemically oxidative polymerizing a monomer compound such as a thiophene compound represented by the above general formula (3) in the presence of the above dopant. As the oxidizing agent for chemical oxidative polymerization, a known oxidizing agent such as iron (III) p-toluenesulfonate can be used, for example.

[0045] Examples of the above dopants include halogen ions such as iodine, bromine, and chlorine; halide ions such as hexafluoroline, hexafluoroarsenide, hexafluoroantimony, tetrafluoroboron, and perchloric acid; alkyl-substituted organic sulfonate ions such as methanesulfonic acid and dodecylsulfonic acid; cyclic sulfonate ions such as camphorsulfonic acid; or alkyl-substituted or unsubstituted benzene mono or disulfonic acid ions such as benzenesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, and benzenedisulfonic acid; 2-naphthalenesulfonic acid; and 1,7-naphthalenesulfonic acid. Examples include alkyl-substituted or unsubstituted ions of naphthalene sulfonic acid in which one to four sulfonic acid groups such as fusonic acid are substituted, anthracene sulfonic acid ions, anthraquinone sulfonic acid ions, alkyl-substituted or unsubstituted biphenyl sulfonic acid ions such as alkyl biphenyl sulfonic acid and biphenyl disulfonic acid, polymer sulfonic acid ions such as polystyrene sulfonic acid and naphthalene sulfonic acid formalin condensate, or heteropoly acid ions such as molybd phosphoric acid, tungstonic acid, and tungstomolybdonic acid, methoxybenzene sulfonic acid, ethoxybenzene sulfonic acid, and xylene sulfonic acid. Among these, at least one selected from polystyrene sulfonic acid, benzene sulfonic acid, p-toluenesulfonic acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, and xylene sulfonic acid is more preferred, and p-toluenesulfonic acid (PTS) is particularly preferred.

[0046] [(c) Electrolyte impregnation process] The electrolytic capacitor of the present invention can be made into a hybrid electrolytic capacitor by using not only a solid electrolyte but also a liquid electrolyte (electrolyte solution) in combination with the electrolyte.

[0047] In the case of a hybrid electrolytic capacitor, in addition to steps (a) to (b) above, step (c) above is performed. In this case, the electrolyte salt, solution, and additives used in the electrolyte can be those described in Japanese Patent Application Publication No. 2024-045918 or those that are known.

[0048] [Electrolytic Capacitors] The electrolytic capacitors manufactured in this invention can be assembled by known methods. After step (b) above, in the case of hybrid electrolytic capacitors, step (c) above is performed, the capacitor is sealed using epoxy resin or rubber, and a voltage is applied to perform aging, thereby manufacturing electrolytic capacitors or hybrid electrolytic capacitors.

[0049] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to these examples. In the examples, "parts" refers to "parts by mass" and "%" refers to "percentage by mass".

[0050] (Example 1) (1) An aluminum anode foil measuring 7 × 100 mm was prepared as the anode of a capacitor element. It was wound together with a cathode foil placed opposite it via separator paper, and leads were attached to the anode foil and cathode foil to obtain a capacitor element. The aluminum anode foil was pre-treated with a chemical conversion treatment in an aqueous solution of diammonium adipate at a voltage of 38 V in order to form a dielectric oxide film. The obtained element had a rated voltage of 25 V and a rated capacitance of 390 μF.

[0051] (2) A pretreatment agent for electrolytic capacitor manufacturing was obtained by diluting 5 parts by mass of polyvinylpyrrolidone (PVP) (Pitzcol K-30: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., molecular weight approximately 45,000) with 95 parts by mass of water.

[0052] (3) Polymerization solution containing conductive polymer monomer, dopant and oxidizing agent Four parts of 2-ethyl-2,3-dihydrothieno[3,4-b]-1,4-dioxin (2-ethyl-EDOT) and 10 parts of 50% ferric p-toluenesulfonate / ethanol solution were mixed to obtain a polymerization solution containing conductive polymer monomer, dopant and oxidizing agent.

[0053] (a) Step to form a pretreatment layer The capacitor element obtained in (1) was immersed in the pretreatment agent obtained in (2) for 30 seconds, and the element was slowly withdrawn. Then, the capacitor element was air-dried at 125°C for 30 minutes to form a pretreatment layer on the anode having a dielectric oxide film. (b) Step to form a conductive solid layer on the pretreatment layer The capacitor element that underwent step (a) was immersed in the polymerization solution described in (3) for 30 seconds, and the element was slowly withdrawn. After drying at 85°C for 30 minutes, a conductive solid layer was formed by further heat treatment at 230°C for 3 minutes. The capacitor element was housed in a bottomed cylindrical aluminum outer case, a butyl rubber sealing body with a through hole for leading out the lead wires was inserted into the open end of the outer case, and the end of the outer case was crimped to seal it. Then, a voltage of 25V was applied and aging was performed to obtain an electrolytic capacitor.

[0054] (Examples 2-21, Comparative Examples 6-19) Electrolytic capacitors were obtained in the same manner as in Example 1, except that the polymers listed in Table 1 were used instead of the pretreatment agent in Example 1, and these were diluted with water to produce a pretreatment agent in the mass percentages listed in Table 1. The polymers other than PVP (Pitzcol K-30) used were as follows: PVP (polyvinylpyrrolidone K-85N: manufactured by Nippon Shokubai, molecular weight approximately 1,000,000) PVP (Pitzcol K-90: ​​manufactured by Daiichi Kogyo Seiyaku Co., Ltd., molecular weight approximately 1,200,000) Poly(N-isopropylacrylamide): (manufactured by Sigma-Aldrich, molecular weight approximately 40,000) Carboxylate-terminated poly(N-isopropylacrylamide): (manufactured by Sigma-Aldrich, molecular weight approximately 2,000)

[0055] The types and mass percentages of the polymers used in Examples 1 to 21 and Comparative Examples 6 to 19 are shown in Table 1.

[0056]

[0057] (Comparative Example 1) A solid electrolytic capacitor was obtained by performing step (b) without performing step (a) described in Example 1.

[0058] (Comparative Example 2) An electrolytic capacitor was obtained in the same manner as in Example 1, except that an aqueous solution of 2 parts by mass of polyvinyl alcohol (molecular weight approximately 75,000) diluted with 98 parts by mass of water was used instead of the pretreatment agent in Example 1.

[0059] (Comparative Example 3) An electrolytic capacitor was obtained in the same manner as in Example 1, except that an aqueous solution of 2 parts by mass of polyvinyl butyral (molecular weight approximately 40,000 to 70,000) diluted with 98 parts by mass of water was used instead of the pretreatment agent in Example 1.

[0060] (Comparative Example 4) An electrolytic capacitor was obtained in the same manner as in Example 1, except that an aqueous solution of 2 parts by mass of ethylene vinyl alcohol (molecular weight approximately 2,000 to 10,000) diluted with 98 parts by mass of water was used instead of the pretreatment agent in Example 1.

[0061] (Comparative Example 5) An electrolytic capacitor was obtained in the same manner as in Example 1, except that an aqueous solution of 2 parts by mass of pullulan (molecular weight approximately 200,000) diluted with 98 parts by mass of water was used instead of the pretreatment agent in Example 1.

[0062] (Test Example 1) <Evaluation of Pretreatment Agent> The viscosity of the pretreatment agent at 25°C was measured using a TV-10 viscometer manufactured by Toki Sangyo Co., Ltd. For the pretreatment agents of Examples 1 to 21, it was confirmed that the viscosity at 25°C was in the range of 1 mPa·s to 100 mPa·s. The measurement results of the viscosity of the pretreatment agents for Examples 1, 2, 3, 4, 10, 11, 12, 14, 15, 16, 17, 19, 20, 21 and Comparative Examples 6, 8, 9, 14, 16, 17, 18, 19 are shown in Table 2.

[0063] (Test Example 2) <Evaluation of Electrolytic Capacitors> For the electrolytic capacitors obtained from Examples 1 to 21 and Comparative Examples 1 to 19, the ESR at 100 kHz was measured using an Agilent Technologies, Inc. Precision LCR meter E4980A. In addition, a DC voltage / current source / monitor R6243 manufactured by Advantest Corporation was used to apply a 25 V DC voltage to both electrodes of the electrolytic capacitor, and the current value after 60 seconds was measured and defined as the LC value. The measurement results are shown in Table 2.

[0064]

[0065] As shown in Table 2, in Examples 1 to 21, electrolytic capacitors with superior LC reduction effect and low ESR were obtained compared to the comparative examples. In particular, in Comparative Examples 2 to 5, where the type of polymer (water-soluble polymer) added to the pretreatment agent was changed, the LC reduction effect was not obtained, or the ESR increased.

[0066] The pretreatment agent and manufacturing method of the present invention can be used in the manufacture of electrolytic capacitors. Furthermore, electrolytic capacitors obtained by the manufacturing method of the present invention can be realized that have excellent LC characteristics and no adverse effects on ESR.

Claims

1. A pretreatment agent for manufacturing electrolytic capacitors, which forms a pretreatment layer on the anode of an electrolytic capacitor, comprising an N-vinyl lactam polymer or an acrylamide polymer, wherein the polymer is dissolved in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol in an amount of 0.1% by mass or more and 5% by mass or less.

2. The pretreatment agent for manufacturing electrolytic capacitors according to claim 1, characterized in that the weight-average molecular weight of the polymer is 40,000 or more and 1,300,000 or less.

3. The pretreatment agent for manufacturing electrolytic capacitors according to claim 1 or 2, characterized in that the viscosity of the pretreatment agent at 25°C is 1 mPa·s or more and 100 mPa·s or less.

4. A method for manufacturing an electrolytic capacitor, comprising at least the steps of forming a pretreatment layer on the anode having a dielectric oxide film of an electrolytic capacitor element, and then forming a conductive solid layer on the pretreatment layer, wherein the step of forming the pretreatment layer is a step of forming a pretreatment layer on the anode by applying a pretreatment agent for manufacturing electrolytic capacitors, which is obtained by dissolving an N-vinyl lactam polymer or an acrylamide polymer in a range of 0.1% by mass or more and 5% by mass or less in a solvent containing one or more selected from the group consisting of water, ethanol, methanol, and isopropyl alcohol, onto the anode of the electrolytic capacitor element, and then removing the solvent of the pretreatment agent.

5. The method for manufacturing an electrolytic capacitor according to claim 4, wherein the viscosity of the pretreatment agent at 25°C is 1 mPa·s or more and 100 mPa·s or less.

6. The method for producing an electrolytic capacitor according to claim 4 or 5, wherein the weight-average molecular weight of the N-vinyllactam polymer or acrylamide polymer in the pretreatment agent is 40,000 or more and 1,300,000 or less.

7. The method for manufacturing an electrolytic capacitor according to claim 4, characterized in that the electrolytic capacitor element is a capacitor element in which an anode foil and a counter cathode foil are wound with a separator in between.

8. The method for manufacturing an electrolytic capacitor according to claim 4, characterized in that the step of forming the conductive solid layer is a step of using an oxidizing agent solution containing a monomer compound and a dopant to chemically oxidize and polymerize in a capacitor element to form a conductive solid layer made of a conductive polymer.

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