Electrolytic capacitor and manufacturing method

Abstract

Provided are: an electrolytic capacitor in which a decrease in electrostatic capacity is suppressed even in a high-temperature environment; and a manufacturing method. An electrolytic capacitor comprises: a capacitor element having a positive electrode foil, a negative electrode foil, an electrolytic solution, and a solid electrolyte layer; a case that accommodates the capacitor element; and a sealing body for sealing the case. The sealing body has an elastic body containing an elastomer. The elastomer contains butyl rubber, and is contained in the elastic body at 31 wt% or more. The electrolytic solution contains glycerin in the amount of 40 wt% or more in the solvent of the electrolytic solution.

Description

Electrolytic capacitor and manufacturing method

[0001] The present invention relates to an electrolytic capacitor that obtains capacitance by the dielectric polarization of a dielectric film and stores and discharges electric charge, and to a method for manufacturing the same.

[0002] Electrolytic capacitors using valve metals such as tantalum or aluminum can achieve a small size and large capacitance by enlarging the surface area of ​​the dielectric by forming the valve metal as a sintered body or etched foil as the anode-side counter electrode. In this type of electrolytic capacitor, the gap between the anode dielectric film and the counter electrode is filled with electrolyte to ensure close contact.

[0003] The electrolyte directly contacts the dielectric film and acts as a true cathode, while also repairing the dielectric film. However, over time, the electrolyte evaporates and escapes from the electrolytic capacitor. As a result, the capacitance of the electrolytic capacitor decreases over time as it dries up, eventually reaching the end of its life.

[0004] The capacitor element is housed in a bottomed outer case, and the opening of the outer case is sealed with a sealant. This sealant is crimped to fit tightly to the case opening and is made of an elastic material with appropriate hardness to improve sealing. For example, the sealant contains an elastomer such as butyl rubber. The elastomer is vulcanized to allow a cross-linking reaction.

[0005] However, the electrolyte is not completely confined within the case, but gradually permeates the sealing material and volatilizes out of the electrolytic capacitor. Therefore, it has been proposed to use a solvent with a high boiling point for the electrolyte (see, for example, Patent Document 1). Known high-boiling-point solvents include γ-butyrolactone with a boiling point of 203°C, butanediol with a boiling point of 230°C, sulfolane with a boiling point of 285°C, ethylene glycol with a boiling point of 198°C, and diethylene glycol with a boiling point of 244°C.

[0006] International Publication No. 2013 / 094462

[0007] In recent years, electrolytic capacitors have been required to perform well in high-temperature environments, such as those at 170°C, such as those used in automobiles. Specifically, electrolytic capacitors are required to have a long life, maintaining a certain level of capacitance for a long period of time even in high-temperature environments. However, the present inventors have confirmed that even if an electrolytic solution is composed of a solvent with a high boiling point exceeding 170°C, evaporation of the electrolytic solution cannot be suppressed in such high-temperature environments, resulting in a decrease in the capacitance of the electrolytic capacitor.

[0008] The present invention has been proposed to solve the above-mentioned problems, and its object is to provide an electrolytic capacitor in which the decrease in capacitance is suppressed even in a high-temperature environment, and a manufacturing method thereof.

[0009] In order to solve the above-described problems, the electrolytic capacitor of this embodiment includes a capacitor element having an anode body, a cathode body, an electrolytic solution, and a solid electrolyte; a case that houses the capacitor element; and a sealing body that seals the case, wherein the sealing body has an elastic body containing an elastomer, the elastomer containing butyl rubber and comprising 31 wt % or more of the elastomer with respect to the elastic body, and the electrolytic solution contains 40 wt % or more of glycerin, diglycerin, or both in a solvent of the electrolytic solution.

[0010] The content of the elastomer may be 36 wt % or less relative to the elastic body.

[0011] The sealing body may be configured such that after being exposed to a temperature environment of 170° C. for 1000 hours, the bending strain change rate is within −30% in a three-point bending test according to JIS K7171.

[0012] The elastic body may contain a total of 50 wt % to 60 wt % of carbon and inorganic filler.

[0013] The carbon may be carbon black having a dibutyl phthalate absorption of 80 ml / 100 g or less.

[0014] The electrolyte has an electrolyte loading coefficient R of 3.93 mg mm / mm, as shown in the following formula (1): ２ It may be set to be equal to or greater than the above (Equation 1).

[0015] The butyl rubber may be crosslinked with an alkylphenol resin.

[0016] In order to solve the above-described problems, the method for manufacturing an electrolytic capacitor of this embodiment includes an element forming step of a capacitor element having an anode body, a cathode body, and a solid electrolyte; an impregnation step of impregnating the capacitor element with an electrolyte solution containing 40 wt % or more of glycerin, diglycerin, or both in a solvent of the electrolyte solution; an accommodating step of accommodating the capacitor element in a case; and a sealing step of sealing the case with a sealing body having an elastic body containing an elastomer, the elastomer including butyl rubber, and the elastomer content relative to the elastic body being 31 wt % or more.

[0017] The method may include a step of producing the sealing body such that, after being exposed to a temperature environment of 170° C. for 1000 hours, a bending strain change rate is −30% or less in a three-point bending test according to JIS K7171.

[0018] In the impregnation step and the sealing step, the electrolyte loading coefficient R shown in the above formula (Formula 1) is 3.93 mg mm / mm ２ The weight of the electrolyte and the shape and size of the sealing body may be combined so as to satisfy the above.

[0019] According to the present invention, cracks are unlikely to occur in the sealing body even in a high-temperature environment, and the capacitance can be maintained for a long period of time.

[0020] 1 is a graph showing the relationship between the bending strain and heat treatment time of elastic bodies having various elastomer contents. 2 is a graph showing the relationship between the electrolyte loading coefficient R and tan δ.

[0021] DETAILED DESCRIPTION OF THE INVENTION An electrolytic capacitor and a manufacturing method thereof according to an embodiment of the present invention will be described below. However, the present invention is not limited to the following embodiment.

[0022] (Overall Structure) An electrolytic capacitor is a passive device that stores and discharges electric charge through capacitance. This electrolytic capacitor has a capacitor element. The capacitor element includes an anode body, a cathode body, a separator, and an electrolyte. A dielectric film is formed on the surface of the anode body. The separator is interposed between the anode body and the cathode body, insulating them from each other. The electrolyte is interposed between the anode body and the cathode body while being in close contact with the dielectric film, and acts as a true cathode. The electrolytic capacitor has an electrolytic solution as the electrolyte. The electrolytic solution is filled in the voids of the capacitor element.

[0023] This capacitor element is housed in a case. The case is made of aluminum, an aluminum alloy containing aluminum or manganese, or stainless steel, and is, for example, a cylinder with a bottom and an open end. A pressure release valve may be formed at the bottom of the case so that it opens when the internal pressure of the case exceeds a set pressure. The opening of the case is sealed by a sealing body. The sealing body is attached to the opening of the case by crimping, and the crimping process bends and crushes the opening of the case inward, allowing the sealing body to adhere tightly.

[0024] In this electrolytic capacitor, the sealing body has an elastomer primarily composed of elastomer. The elastomer contains at least butyl rubber as the elastomer. Butyl rubber is also called isobutylene isoprene rubber. For example, regular butyl is preferred as the butyl rubber. The content of the elastomer containing butyl rubber in the elastomer is 31 wt% or more. Furthermore, the electrolyte contains 40 wt% or more of glycerin, diglycerin, or both, based on the total solvent content of the electrolyte, and a solid electrolyte is used in addition to the electrolyte.

[0025] The mechanism of thermal oxidative degradation of the sealant's elastomer is as follows: First, the C-H bonds of the elastomer molecules on the exterior side of the case are cleaved, generating radicals. First, these radicals attack other C-H bonds in the elastomer molecules, promoting further cleavage. Second, oxygen is added to these radicals, generating peroxides. These peroxides decompose under heat, accelerating the generation of radicals, which then attack other C-H bonds in the elastomer molecules, promoting further cleavage.

[0026] When this process is repeated, the chain length of the elastomer molecules shortens, softening the elastomer material. The lower molecular weight elastomer becomes more susceptible to vaporization. Furthermore, when the elastomer molecules that have been cut due to their shorter chain length recombine, the density of the elastomer increases. This causes the elastomer to shrink. The shrinkage of the elastomer is most pronounced on the exterior side of the case of the sealing body, which is more susceptible to heat and oxygen, and the degree of shrinkage decreases from the exterior side of the case of the sealing body toward the interior side of the case.

[0027] On the other hand, the electrolyte causes swelling of the elastic body inside the case of the sealing body. This causes contraction and expansion in areas inside the sealing body, leading to cracks in the elastic body of the sealing body. When cracks occur in the elastic body, the electrolyte evaporates through the cracks, reducing the capacitance of the electrolytic capacitor.

[0028] In response to this mechanism of thermal oxidative degradation, butyl rubber is resistant to electrolyte penetration, suppressing swelling of the inside of the case of the elastomer. Therefore, in an elastomer containing butyl rubber, the difference in volume change between the inside of the case, which swells due to electrolyte penetration, and the outside of the case, which shrinks due to thermal oxidative degradation, is small. Furthermore, when the elastomer content in the elastomer is 31 wt % or more, the bending strain change rate of the elastomer remains within -30% even after prolonged exposure to high-temperature environments. By limiting the bending strain change rate of the elastomer to a decrease of 30%, flexibility is maintained and cracks are less likely to occur in the elastomer. This makes it possible to suppress volatilization and evaporation of the electrolyte through cracks.

[0029] The bending strain change rate indicates the change in bending test results before and after long-term exposure to a high-temperature environment. The temperature and time for the bending test to which the elastic body is exposed are 170°C and 1000 hours. The bending test is a three-point bending test in accordance with JIS K7171. An elastic body test piece having a thickness of 2 mm, a length of 40 mm, and a width of 25 mm is prepared and placed on a support with a support distance of 32 mm. A force is applied to the center of the test piece with an indenter at a test speed of 1 mm / min in a temperature environment of 170°C. The bending strain until cracks appear in the test piece is measured. The bending strain (%) before long-term exposure to a high-temperature environment is subtracted from the bending strain (%) after long-term exposure to a high-temperature environment, and the percentage of the difference relative to the bending strain (%) before long-term exposure to a high-temperature environment is defined as the bending strain change rate.

[0030] Furthermore, butyl rubber has low electrolyte permeability. Furthermore, when the content of glycerin, diglycerin, or both (hereinafter referred to as "glycerins") is 40 wt % or more of the total amount of solvent in the electrolyte, the amount of electrolyte that evaporates through the elastomer is particularly suppressed. Therefore, this elastomer suppresses both the evaporation of electrolyte through cracks and the evaporation of electrolyte through the elastomer, allowing the electrolytic capacitor to maintain a good capacitance for a long period of time.

[0031] The solid electrolyte reduces the high resistivity caused by the high viscosity of glycerin compounds, thereby lowering the internal resistance of the electrolytic capacitor. Preferably, the solid electrolyte is a conductive polymer. When dedoping occurs in the conductive polymer, the conductivity of the solid electrolyte layer decreases, and the canceling effect of glycerin and diglycerin on the resistivity is weakened. However, glycerin compounds have low ionic diffusivity, so the dedoping reaction is suppressed. Therefore, in this electrolytic capacitor, a solid electrolyte is used in combination with an electrolytic solution.

[0032] (Sealing Body) In the above electrolytic capacitor, the elastomer of the sealing body may contain, in addition to butyl rubber, elastomers such as ethylene propylene diene rubber (also known as EPDM), styrene butadiene rubber, isoprene rubber, fluororubber, acrylic rubber, natural rubber, or a mixture of these, as long as the butyl rubber exceeds 50 wt% of the total elastomer contained in the elastomer. The elastomer content in the elastomer is preferably 36 wt% or less. The elastomer of the present invention refers to a polymeric substance exhibiting rubber elasticity and is thermosetting.

[0033] Butyl rubber is preferably produced by vulcanization. Examples of vulcanization include resin vulcanization, sulfur vulcanization, and quinoid vulcanization. Examples of vulcanizing agents include alkylphenol resins such as alkylphenol formaldehyde resins, quinoids, and sulfur. Examples of crosslinking accelerators include zinc oxide, magnesium oxide, lead peroxide, dibenzothiazyl, disulfide, 1,2-polybutadiene, triallyl cyanurate, metal salts of methacrylic acid and acrylic acid, and ester stearic acid N,N'-metaphenyl dimaleic acid. In particular, butyl rubber is preferably crosslinked with alkylphenol resins, which inhibits cleavage of the butyl rubber.

[0034] When butyl rubber and ethylene propylene rubber are used in combination, the elastomer is preferably a blended rubber obtained by crosslinking butyl rubber and ethylene propylene rubber by resin vulcanization. This suppresses evaporation of the electrolyte more than when butyl rubber and ethylene propylene rubber are vulcanized separately and then mixed. This blended rubber is prepared by mixing unvulcanized butyl rubber and unvulcanized ethylene propylene rubber, adding a resin vulcanizing agent to the mixture, and then pressurizing and heating it. Alternatively, this blended rubber is prepared by adding unvulcanized butyl rubber, unvulcanized ethylene propylene rubber, and a resin vulcanizing agent, and then pressurizing and heating it.

[0035] The elastic body may contain carbon and inorganic fillers in addition to the elastomer. The addition of carbon and inorganic fillers makes the butyl rubber less susceptible to cleavage and suppresses softening of the butyl rubber. Examples of carbon include carbon black, and examples of inorganic fillers include talc, mica, silica, kaolin, titania, alumina, and mixtures thereof.

[0036] The carbon and inorganic filler are preferably contained in a total amount of 50 wt% to 60 wt% of the entire elastomer. If the total content of the carbon and inorganic filler is 50 wt% or more of the entire elastomer, the elastomer can obtain better strength and contribute to a reduction in the bending strain change rate after exposure to a high-temperature environment. Furthermore, if the total content of the carbon and inorganic filler is 60 wt% or less of the entire elastomer, the elastomer can obtain good flexibility and suppress cracking of the elastomer.

[0037] Furthermore, the carbon is preferably carbon black having a dibutyl phthalate absorption of 80 ml / 100 g or more. Dibutyl phthalate absorption is also called DBP absorption or DBP oil absorption. Carbon black exists as agglomerates in which particles are strongly adhered to each other. These agglomerates are called aggregates and have a structure similar to a bunch of grapes. Dibutyl phthalate absorption indicates the ability of the voids within this structure to absorb dibutyl phthalate. In other words, it is an index showing the degree of development of the carbon black structure. This dibutyl phthalate absorption can be measured, for example, in accordance with the method for determining oil absorption in JIS K 6217-4, a JIS standard.

[0038] If the carbon contained in the elastic body of the sealing body is carbon black with a structure that results in a dibutyl phthalate absorption of 80 ml / 100 g or less, it not only contributes to a decrease in the bending strain change rate after exposure to a high temperature environment and suppresses the decrease in capacitance, but also significantly suppresses the leakage current of the electrolytic capacitor. Although this is speculation and not limited to this mechanism, the mechanism behind the leakage current suppression effect is speculated to be as follows.

[0039] First, when a sealing body having an elastic body is incorporated into a circuit through which leakage current caused by defects in the dielectric film flows, if the electrical resistance of the sealing body is high, the leakage current will be small, but if the electrical resistance of the sealing body is low, the leakage current will be large. Carbon black with a high dibutyl phthalate absorption has a large structure, so carbon black aggregates come into contact with each other more frequently. In high-temperature environments, thermal vibrations tend to increase the frequency of contact between carbon black aggregates.

[0040] If the contact frequency increases and carbon black strands form, these strands function as conductive circuits within the seal. When conductive circuits caused by carbon black strands form within the seal, the electrical resistance of the seal decreases, resulting in increased leakage current.

[0041] However, if the carbon black has a structure that results in a dibutyl phthalate absorption of 80 ml / 100 g or less, the frequency of contact between carbon black aggregates is kept low, and carbon black linkages do not occur or are reduced. In other words, conductive circuits are not formed within the sealer, or the number of parallel conductive circuits within the sealer is kept low, maintaining the sealer's electrical resistance high. Therefore, it is presumed that not only can the capacitance of the electrolytic capacitor be kept low, but also the leakage current of the electrolytic capacitor can be suppressed. Furthermore, suppressing the leakage current of the electrolytic capacitor further suppresses the decrease in capacitance over time.

[0042] The elastomer may further contain one or more of process oil, polyethylene wax, and polybutadiene. Examples of process oil include paraffinic, naphthenic, and aromatic oils. The polyethylene wax may be either low-density polyethylene wax or high-density polyethylene wax.

[0043] The sealing body may be an elastomer, a laminate of an elastomer and a hard substrate, or a hard substrate enclosed within an elastomer. The hard substrate may be a synthetic resin plate, a ceramic plate, or a metal plate. The synthetic resin plate may be made of, for example, phenolic resin, epoxy resin, or polyethylene sulfide resin. Various resins can be used, including epoxy resin, fluororesin, acrylic resin, polyimide resin, silicone resin, phenolic resin, melamine resin, urethane resin, and unsaturated polyester resin. The metal plate may be made of, for example, aluminum, an aluminum alloy containing aluminum or manganese, or stainless steel. The hard substrate improves the sealing performance inside the electrolytic capacitor and protects the elastomer from the electrolyte and heat.

[0044] (Electrolyte) The electrolyte may contain a solvent other than glycerin, as long as the content of the glycerin is 40 wt % or more of the total solvent. Examples of the solvent other than glycerin include protic polar solvents such as monohydric alcohols, polyhydric alcohols, and oxyalcohol compounds, and aprotic polar solvents such as sulfones, amides, lactones, cyclic amides, and nitriles.

[0045] Examples of monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc. Examples of polyhydric alcohols and oxyalcohol compounds include ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.

[0046] Examples of sulfone-based solvents include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane. Examples of amide-based solvents include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide. Examples of lactones and cyclic amide-based solvents include γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate. Examples of nitrile-based solvents include acetonitrile, 3-methoxypropionitrile, and glutaronitrile.

[0047] The solvent to be added other than glycerin and diglycerin is preferably ethylene glycol, sulfolane, or both. The boiling point of ethylene glycol is 198°C. The boiling point of sulfolane is 285°C. Therefore, an electrolyte containing ethylene glycol and sulfolane can achieve an evaporation suppression effect. Furthermore, by including ethylene glycol and sulfolane in the electrolyte, the concentration of glycerins can be reduced, the viscosity of the entire electrolyte decreases, and the specific resistance of the electrolytic capacitor decreases. For example, the content of glycerins may be 100 wt% or less, preferably 98 wt% or less, of the total amount of solvent in the electrolyte.

[0048] The electrolyte has an electrolyte loading coefficient R of 3.93 mg mm / mm, as shown in the following formula (1). ２ The gaps in the capacitor element are filled so that the above formula is satisfied (Equation 1).

[0049] The weight of the initial electrolyte is the weight of the electrolyte filled in the electrolytic capacitor during its manufacturing process. This initial electrolyte can be extracted by removing the capacitor element from an unused electrolytic capacitor and using a centrifuge or similar device. In other words, the amount of water that was mixed in during the manufacturing process of the electrolytic capacitor is also added to the weight of the initial electrolyte.

[0050] The thickness of the sealing body is the length along the winding axis of the capacitor element, and is the distance that the electrolyte inside the electrolytic capacitor must pass through before escaping to the outside. The sealing surface area of ​​the sealing body is the area of ​​a plane extending in a direction perpendicular to the winding axis of the capacitor element, and is the area exposed to the inside of the electrolytic capacitor through which the electrolyte inside the electrolytic capacitor can pass when escaping to the outside.

[0051] The electrolyte loading coefficient R is 3.93 mg mm / mm ２ If the above conditions are met, not only is the electrolytic capacitor prevented from decreasing in capacitance due to exposure to a high-temperature environment, but also an increase in resistance at low frequencies, i.e., dielectric loss tangent (tan δ), can be suppressed.

[0052] This is speculation and is not limited to this mechanism, but the electrolyte loading coefficient R is 3.93 mg mm / mm ２ The reason why the increase in tan δ is suppressed by the above is as follows: First, when the electrolyte evaporates, the amount of electrolyte around the conductive polymer decreases, making it easier for oxygen to reach the conductive polymer without being trapped by the electrolyte. Therefore, when the amount of electrolyte in the capacitor element decreases due to evaporation, the conductive polymer becomes more susceptible to oxidative degradation.

[0053] Therefore, if the initial weight of the electrolyte is large, even if the electrolyte evaporates, sufficient electrolyte will remain to protect the periphery of the conductive polymer. Also, if the sealing body is thick, the electrolyte will be less likely to evaporate, and sufficient electrolyte will remain to protect the periphery of the conductive polymer. Also, if the sealing body has a small sealing surface area, the electrolyte will be less likely to evaporate, and sufficient electrolyte will remain to protect the periphery of the conductive polymer. And, if the electrolyte loading coefficient R is 3.93 mg mm / mm ２ If the above conditions are met, the oxidative deterioration of the conductive polymer due to evaporation of the electrolyte solution is suppressed, and the tan δ of the electrolytic capacitor is suppressed.

[0054] In addition, the electrolyte loading coefficient R is 8.5 mg mm / mm ２ If the thickness is less than or equal to this, swelling of the solid electrolytic capacitor in a reflow process environment or a high-temperature environment can be suppressed.

[0055] This electrolyte is a solution in which an anionic component and a cationic component are added to a solvent. The anionic component and the cationic component are typically salts of organic acids, salts of inorganic acids, or salts of complex compounds of organic acids and inorganic acids, and are added to the solvent in the form of an ion-dissociating salt that dissociates into the anionic component and the cationic component. An acid that becomes the anionic component and a base that becomes the cationic component may be added separately to the solvent. Furthermore, the electrolyte does not necessarily need to contain either the anionic component or the cationic component, or both the anionic component and the cationic component, in the solvent.

[0056] Examples of organic acids that can serve as anion components include carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcylic acid, phloroglucinic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, pyromellitic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, t-butyladipic acid, and 11-vinyl-8-octadecenedioic acid, as well as phenols and sulfonic acids.

[0057] Furthermore, examples of inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid, etc. Examples of composite compounds of organic acids and inorganic acids include borodisalicylic acid, borodioxalic acid, borodiglycolic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodiazelaic acid, borodibenzoic acid, borodimaleic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodiresorcylic acid, borodimethylsalicylic acid, borodinaphthoic acid, borodimandelic acid, and borodi(3-hydroxy)propionic acid, etc.

[0058] Examples of the cationic component include ammonium, quaternary ammonium, quaternized amidinium, amine, sodium, potassium, etc. Examples of the quaternary ammonium include tetramethylammonium, triethylmethylammonium, tetraethylammonium, etc. Examples of the quaternized amidinium include ethyldimethylimidazolinium, tetramethylimidazolinium, etc. Examples of the amine include primary amine, secondary amine, and tertiary amine. Examples of the primary amine include methylamine, ethylamine, propylamine, etc. Examples of the secondary amine include dimethylamine, diethylamine, ethylmethylamine, dibutylamine, etc. Examples of the tertiary amine include trimethylamine, triethylamine, tributylamine, ethyldimethylamine, ethyldiisopropylamine, etc.

[0059] Furthermore, other additives can be added to the electrolyte. Examples of additives include complex compounds of boric acid and polysaccharides (e.g., mannitol, sorbitol), complex compounds of boric acid and polyhydric alcohols, borate esters, nitro compounds, phosphate esters, and colloidal silica. These may be used alone or in combination of two or more. Nitro compounds suppress the generation of hydrogen gas in the electrolytic capacitor. Examples of nitro compounds include o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, and p-nitrophenol.

[0060] The anions and cations may be added to the electrolytic solution in the form of ionically dissociable salts, or an acid that becomes an anion and a base that becomes a cation may be added to the electrolytic solution separately as solute components. The anions and cations may be used alone or in combination of two or more. The electrolytic solution may be composed only of glycerins, without containing an ionically dissociable salt that dissociates into an anion component and a cation component or an additive.

[0061] (Solid Electrolyte) Examples of solid electrolytes include manganese dioxide or 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes, as well as conductive polymers. Conductive polymers are self-doped conjugated polymers doped with an intramolecular dopant, or conjugated polymers doped with external dopant molecules. Conjugated polymers are obtained by chemical oxidative polymerization or electrolytic oxidative polymerization of monomers having π-conjugated double bonds or their derivatives. The dopant or external dopant molecule is an acceptor that readily accepts electrons into the conjugated polymer, or a donor that readily donates electrons, which allows the conductive polymer to exhibit high conductivity.

[0062] As the conjugated polymer, any known polymer can be used without any particular limitation. Examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. These conjugated polymers may be used alone or in combination of two or more types, or may even be a copolymer of two or more types of monomers.

[0063] Among the above conjugated polymers, preferred are conjugated polymers obtained by polymerizing thiophene or a derivative thereof, and preferred are conjugated polymers obtained by polymerizing 3,4-ethylenedioxythiophene (i.e., 2,3-dihydrothieno[3,4-b][1,4]dioxin), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, or derivatives thereof. The thiophene derivative is preferably a compound selected from thiophenes having substituents at the 3rd and 4th positions, and the substituents at the 3rd and 4th positions of the thiophene ring may form a ring together with the carbon atoms at the 3rd and 4th positions. The alkyl group or alkoxy group preferably has 1 to 16 carbon atoms.

[0064] In particular, a polymer of 3,4-ethylenedioxythiophene, known as EDOT, i.e., poly(3,4-ethylenedioxythiophene), known as PEDOT, is preferred. Furthermore, a substituent may be added to 3,4-ethylenedioxythiophene. For example, an alkylated ethylenedioxythiophene having an alkyl group having 1 to 5 carbon atoms added as a substituent may be used. Examples of alkylated ethylenedioxythiophenes include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin), and butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxin).

[0065] Any known dopant can be used without any particular limitation. A single dopant may be used, or two or more dopants may be used in combination. Furthermore, a polymer or a monomer may be used. Examples of dopants include inorganic acids such as polyanions, boric acid, nitric acid, and phosphoric acid, and organic acids such as acetic acid, oxalic acid, citric acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bisoxalateborate acid, sulfonylimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid.

[0066] Examples of the polyanion include a substituted or unsubstituted polyalkylene, a substituted or unsubstituted polyalkenylene, a substituted or unsubstituted polyimide, a substituted or unsubstituted polyamide, and a substituted or unsubstituted polyester, and include a polymer consisting only of a structural unit having an anionic group, and a polymer consisting of a structural unit having an anionic group and a structural unit not having an anionic group. Specific examples of the polyanion include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0067] (Other Configurations) The anode body and the cathode body are foil bodies based on a valve metal. The foil bodies may be formed by stretching the valve metal or by sintering a valve metal powder. In wound electrolytic capacitors, the anode body has a long strip shape, while in laminated and flat electrolytic capacitors, the anode body is a flat plate. The valve metal may be aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, or the like. The purity of the anode body is preferably 99.9% or higher, and that of the cathode body is preferably about 99% or higher, but impurities such as silicon, iron, copper, magnesium, and zinc may be contained.

[0068] A surface-expanding layer is formed on one or both sides of the anode foil. A surface-expanding layer may also be formed on one or both sides of the cathode foil. The surface-expanding layer may be an etching layer formed by etching the foil, a sintered layer formed by sintering valve metal powder, or a vapor-deposited layer formed by vapor-depositing valve metal particles onto the foil. That is, the surface-expanding layer has a porous structure consisting of tunnel-shaped pits, spongy pits, or voids between densely packed powder or particles. Tunnel-shaped etching pits are holes dug in the thickness direction of the foil. Furthermore, spongy etching pits make the surface-expanding layer into a sponge-like layer with a series of fine voids extending in a spatial manner.

[0069] The dielectric film is formed on one or both sides of the anode body on which the surface-expanding layer is formed. When a surface-expanding layer is formed, the dielectric film is formed on the surface of the surface-expanding layer, following the irregularities of the surface-expanding layer. The dielectric film is typically an oxide film formed on the surface of the anode body. If the anode body is made of aluminum, it is an aluminum oxide layer formed by oxidizing the surface of the surface-expanding layer. This dielectric film is formed by chemical conversion treatment in which a voltage is applied in an aqueous solution of adipic acid, boric acid, phosphoric acid, or the like. Furthermore, a thin dielectric film (approximately 1 to 10 V) may be formed on the surface of the cathode foil by chemical conversion treatment, as needed. A natural oxide film may be formed on the surface of the cathode foil. The natural oxide film is formed by the cathode body reacting with oxygen in the air.

[0070] Examples of materials for the separator include cellulose papers such as kraft, Manila hemp, esparto, hemp, and rayon, and mixtures thereof; polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof; polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins; polyamide-based resins such as aliphatic polyamides, semi-aromatic polyamides, and wholly aromatic polyamides; polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and polyvinyl alcohol resins. These resins can be used alone or in combination.

[0071] (Manufacturing Method) Such an electrolytic capacitor is manufactured through an element-forming step, an impregnation step, a housing step, a step of preparing a sealing body, and a sealing step. The element-forming step includes an anode-forming step of forming an anode body, a cathode-forming step of forming a cathode body, a laminate-forming step of stacking the anode body and the cathode body with a separator interposed therebetween, and a solid electrolyte-forming step of forming a solid electrolyte in the laminate. In the laminate-forming step, the strip-shaped anode body, the cathode body, and the separator may be wound to form the laminate as a wound body.

[0072] After the winding, a repair chemical conversion step may be provided to repair bare metal portions of the valve metal exposed when the anode body and the cathode body are cut to a desired width, and to repair defects in the anode body and the cathode body caused by physical stress such as winding.

[0073] In the solid electrolyte formation step, a solid electrolyte layer is formed between the anode body and the cathode body using, for example, a conductive polymer liquid. The conductive polymer liquid is a liquid in which a conductive polymer is dispersed or dissolved. The dispersion medium or solvent for the conductive polymer liquid may be any medium that disperses or dissolves conductive polymer particles or powder, such as water or a mixture of water and an organic solvent. Suitable examples of organic solvents include polar solvents, alcohols, esters, hydrocarbons, carbonate compounds, ether compounds, chain ethers, heterocyclic compounds, and nitrile compounds.

[0074] A solid electrolyte is formed in the laminate by using an impregnation method in which the laminate is impregnated with a conductive polymer liquid. Alternatively, the conductive polymer is attached to the anode body. The conductive polymer liquid may be immersed or applied once or multiple times. The laminate may be placed in a reduced pressure environment to be impregnated with the conductive polymer liquid. After the conductive polymer liquid is impregnated or applied, the solvent is removed by a drying process.

[0075] In the impregnation step, the capacitor element is immersed in the electrolyte solution to impregnate the voids within the capacitor element. A depressurization or pressurization process may be performed as necessary to impregnate the electrolyte solution into smaller voids. The electrolyte impregnation step may be repeated multiple times. For example, the pressure inside the capacitor element may be reduced, and the electrolyte solution may be injected into the capacitor element while pressurizing the electrolyte solution.

[0076] In the housing process, the capacitor element is housed in an outer case, and in the sealing process, the opening of the outer case is sealed with a sealing member. After the capacitor element is sealed in the outer case, the electrolytic capacitor is completed by undergoing an aging process. In the aging process, a DC voltage is applied to the electrolytic capacitor to repair defects in the dielectric film, etc.

[0077] The sealing body used in the sealing process is produced through a process in which the sealing body is exposed to a temperature environment of 170°C for 1000 hours and then undergoes a process in which the bending strain change rate is within -30% in a three-point bending test according to JIS K7171.

[0078] In the impregnation process and the sealing process, the electrolyte loading coefficient R is 3.93 mg mm / mm ２The combination of the weight of the electrolyte to be impregnated into the capacitor element and the shape and size of the sealing member is selected so that the above is achieved.

[0079] The electrolytic capacitor of the present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0080] Examples 1 to 9 An electrolytic capacitor according to Example 1 was fabricated. The anode foil was aluminum foil, the surface of which was enlarged by etching, and a dielectric film was formed by chemical conversion treatment. The cathode foil was also aluminum foil, the surface of which was enlarged by etching, and an oxide film was formed by chemical conversion treatment. Lead wires were connected to each foil, and the anode foil and cathode foil were wound facing each other with a manila separator interposed between them. The capacitor element was then immersed in an aqueous solution of ammonium dihydrogen phosphate for 10 minutes to undergo chemical conversion repair.

[0081] Next, a dispersion liquid of polyethylenedioxythiophene doped with polystyrene sulfonic acid (PEDOT / PSS) was prepared as a conductive polymer, and the capacitor element was immersed in the dispersion liquid. The capacitor element was then removed and dried at 150° C. for 30 minutes, thereby forming a solid electrolyte in the capacitor element.

[0082] An electrolyte solution was prepared by adding ammonium azelaate to a solvent composed of 40 wt% glycerin and 60 wt% ethylene glycol. Ammonium azelaate was added at a ratio of 0.16 mol per 1 kg of electrolyte. The capacitor element with the conductive polymer formed thereon was immersed in the electrolyte solution, allowing the electrolyte to penetrate the capacitor element.

[0083] This capacitor element was housed in an aluminum case. A seal was attached to the open end of the aluminum case, and the aluminum case was sealed by crimping. The seal consisted solely of an elastomer. The elastomer consisted of 31 wt% elastomer, 16 wt% carbon, 40 wt% inorganic filler, vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent. The vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent were added so that the total amount was 12 wt%. The entire elastomer was regular butyl. The carbon was carbon black with a dibutyl phthalate absorption capacity of 50 ml / 100 g.

[0084] After the capacitor element was housed in an aluminum case and sealed with a sealant, the electrolytic capacitor was subjected to an aging treatment in which a DC voltage was applied to the electrolytic capacitor to repair any damage to the dielectric film that had been caused during the winding and other processes of the electrolytic capacitor.

[0085] Furthermore, electrolytic capacitors were fabricated in Examples 2 to 8 and Comparative Examples 1 to 10. These electrolytic capacitors differ from Example 1 in the composition ratio of glycerin and ethylene glycol that constitute the solvent of the electrolyte solution and the content of elastomer contained in the elastic body. Other configurations of the electrolytic capacitors in Examples 2 to 8 and Comparative Examples 1 to 10 are the same as those in Example 1.

[0086] In the electrolytic capacitors of Comparative Examples 1 to 3, the glycerin content in the electrolyte solution was 0 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 100 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 1, 31 wt % in Comparative Example 2, and 36 wt % in Comparative Example 3.

[0087] In the electrolytic capacitors of Comparative Examples 4 to 6, the glycerin content in the electrolyte solution was 20 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 80 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 4, 31 wt % in Comparative Example 5, and 36 wt % in Comparative Example 6.

[0088] In the electrolytic capacitors of Comparative Example 7 and Examples 1 and 2, the glycerin content in the electrolyte solution was 40 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 60 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 7, 31 wt % in Example 1, and 36 wt % in Example 2.

[0089] In the electrolytic capacitors of Comparative Example 8 and Examples 3 and 4, the glycerin content in the electrolyte solution was 60 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 40 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 8, 31 wt % in Example 3, and 36 wt % in Example 4.

[0090] In the electrolytic capacitors of Comparative Example 9 and Examples 5 and 6, the glycerin content in the electrolyte solution was 80 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 20 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 9, 31 wt % in Example 5, and 36 wt % in Example 6.

[0091] In the electrolytic capacitors of Comparative Example 10 and Examples 7 and 8, the glycerin content in the electrolyte solution was 100 wt % relative to the total solvent, and the ethylene glycol content in the electrolyte solution was 0 wt % relative to the total solvent. The elastomer content in the elastic body constituting the sealing body was 27 wt % in Comparative Example 10, 31 wt % in Example 7, and 36 wt % in Example 8.

[0092] When the elastomer content in the elastomer is 27 wt%, the elastomer contains 17 wt% carbon, 45 wt% inorganic filler, vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent. The vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent were added in a total amount of 11 wt%. When the elastomer content in the elastomer is 36 wt%, the elastomer contains 14 wt% carbon, 37 wt% inorganic filler, vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent. The vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent were added in a total amount of 13 wt%.

[0093] (Three-point bending test) The elastic bodies of Comparative Example 7, Example 1, and Example 2 were subjected to a three-point bending test at regular intervals while exposed to high temperatures, and the amount of change in bending strain was measured. The elastic body of Comparative Example 7 contained 27 wt % of elastomer relative to the entire elastic body, the elastic body of Example 1 contained 31 wt % of elastomer relative to the entire elastic body, and the elastic body of Example 2 contained 36 wt % of elastomer relative to the entire elastic body.

[0094] In a three-point bending test, the elastic bodies of Comparative Example 7, Example 1, and Example 2 were exposed to a temperature of 170°C. The three-point bending test was performed immediately before exposure to a temperature of 170°C, after 500 hours, and after 1000 hours. Test pieces measuring 2 mm in thickness, 40 mm in length, and 25 mm in width were cut from the elastic bodies and placed on a support with a support distance of 32 mm. A force was applied to the center of the test piece using an indenter at a test speed of 1 mm / min. The bending strain until cracks occurred in the test piece was then measured. The bending strain change rate after 1000 hours relative to the bending strain immediately before exposure to a temperature of 170°C was calculated. The bending strain change rate was calculated by subtracting the bending strain (%) immediately before exposure to a temperature of 170°C from the bending strain (%) after 1000 hours at a temperature of 170°C, and expressing the difference as a percentage of the bending strain (%) immediately before exposure to a temperature of 170°C.

[0095] The relationship between the bending strain change rate and the heat treatment time for the elastic bodies of Comparative Example 7, Example 1, and Example 2 is shown in the graph of Figure 1. In Figure 1, the series of square plots corresponds to Example 1, the series of circle plots corresponds to Example 2, and the series of diamond plots corresponds to Comparative Example 7. The bending strain change rates after 1000 hours for the elastic bodies of Comparative Example 7, Example 1, and Example 2 are shown in Table 1 below. (Table 1)

[0096] As shown in FIG. 1, in comparison with Comparative Example 7 in which the elastomer content was 27 wt % relative to the entire elastomer body, the elastomer bodies of Examples 1 and 2 in which the elastomer content was 31 wt % and 36 wt % relative to the entire elastomer body, respectively, showed suppressed changes in bending strain even after 1000 hours had elapsed.

[0097] Specifically, as shown in Table 1, it was confirmed that the bending strain change rate of the elastic body of Comparative Example 1 reached -66%, while the bending strain change rates of the elastic bodies of Examples 1 and 2 were within -30%. In other words, it was confirmed that elastic bodies containing butyl rubber and having an elastomer content of 31 wt % or more relative to the entire elastic body retain their flexibility and are less likely to crack even when exposed to high temperatures for long periods of time.

[0098] (Capacitance Test) The electrolytic capacitors of Examples 1 to 8 and Comparative Examples 1 to 10 were exposed to a high-temperature environment at 170°C. The capacitance (Cap) of each electrolytic capacitor was measured immediately before exposure to the high-temperature environment and after 2500 hours of exposure to the high-temperature environment, and ΔCap (%), which represents the rate of change in capacitance before and after exposure to the high-temperature environment, was calculated. That is, ΔCap was calculated by subtracting the Cap after 2500 hours at 170°C from the Cap before exposure to the 170°C environment, and expressing the difference as a percentage of the Cap before exposure to the 170°C environment. The capacitance was measured using an LCR meter (Agilent ZM2376, manufactured by NF Corporation). The ambient temperature during measurement was 25°C, the DC bias was 1.5 V, the AC current level was a sine wave of 1.0 Vrms, and the measurement frequency was 120 Hz.

[0099] The capacitance change rates ΔCap of the electrolytic capacitors of Examples 1 to 8 and Comparative Examples 1 to 10 are shown in Table 2 below. (Table 2)

[0100] As shown in Table 2, when the elastomer content is 31 wt% or more relative to the total elastomer body, ΔCap is kept low. For example, electrolytic capacitors with an elastomer content of 27 wt% relative to the total elastomer body are almost unable to obtain capacitance. In contrast, electrolytic capacitors with an elastomer content of 31 wt% or more relative to the total elastomer body maintain capacitance at about half, even at worst, as shown in Comparative Example 3.

[0101] Furthermore, among electrolytic capacitors in which the elastomer content is 31 wt % or more relative to the entire elastomer body, Examples 1 to 8 in which glycerin is 40 wt % or more relative to the entire solvent of the electrolyte solution have a ΔCap of -16% or more. In other words, among electrolytic capacitors in which the elastomer content is 31 wt % or more relative to the entire elastomer body, those in which glycerin is 40 wt % or more relative to the entire solvent of the electrolyte solution maintain a good capacitance even when exposed to high temperatures for a long period of time.

[0102] Thus, it was confirmed that when the elastomer content is 31 wt % or more relative to the entire elastic body, the bending strain change rate is within -30%, and when the glycerin content is 40 wt % or more relative to the entire solvent of the electrolyte solution, the capacitance is well maintained even when exposed to high temperatures for a long period of time.

[0103] Furthermore, electrolytic capacitors of Examples 9 and 10 were fabricated. The electrolytic capacitor of Example 9 differs from Example 3 in that glycerin and sulfolane were used as the solvent for the electrolyte solution instead of the combination of glycerin and ethylene glycol. The electrolytic capacitor of Example 10 also differs from Example 3 in that glycerin and polyethylene glycol were used as the solvent for the electrolyte solution. Other than the changed solvent combination, the structure, composition, manufacturing method, and manufacturing conditions of the electrolytic capacitor were the same as those of Example 3, including the glycerin ratio being 60 wt %, the fact that the elastic body of the sealing body contained butyl rubber, and the elastomer content relative to the entire elastic body was 31 wt %.

[0104] The electrolytic capacitors of Examples 9 and 10 were also exposed to a high-temperature environment of 170°C. The capacitance (Cap) of each electrolytic capacitor was measured immediately before exposure to the high-temperature environment and after 2500 hours of exposure to the high-temperature environment, and ΔCap (%), which is the rate of change in capacitance before and after exposure to the high-temperature environment, was calculated. The capacitance measurement method was the same as in Example 3.

[0105] The capacitance change rates ΔCap of the electrolytic capacitors of Examples 9 and 10 are shown in Table 3 below, along with that of Example 3. (Table 3)

[0106] The capacitance change rate, ΔCap (%), of Examples 9 and 10 is not significantly different from that of Example 3. The capacitance change of Examples 9 and 10 was kept small compared to Comparative Examples 1 to 10. That is, it was confirmed that the capacitance was well maintained even when exposed to high temperatures for a long period of time, as long as the other solvent mixed with glycerin, whether ethylene glycol, sulfolane, or polyethylene glycol, contained butyl rubber, the elastomer content was 31 wt % or more relative to the entire elastomer, and the glycerin content was 40 wt % or more relative to the entire solvent of the electrolyte solution.

[0107] (Examples 11A-C to 17A-C) Elastic bodies of Examples 11 to 17 were produced. The type of carbon contained in the elastic body of these sealing bodies differed from that of Example 1. In Example 1, 16 wt % of carbon black having a dibutyl phthalate absorption capacity (hereinafter referred to as DBP absorption capacity) of 50 ml / 100 g was contained in the elastic body. In contrast, in Examples 11 to 17, carbon black having a dibutyl phthalate absorption capacity of 38.5 to 139 ml / 100 g was contained in the elastic body. The carbon content in Examples 11 to 17 was the same as that of Example 1.

[0108] In Example 11, the elastomer contained 16 wt% of carbon black (manufactured by Cancarb, THERMAX N990: ASTM D 1765-01) with a DBP absorption of 38.5 ml / 100 g. In Example 12, the elastomer contained 16 wt% of carbon black (manufactured by Asahi Carbon, Asahi #35 N754: ASTM D 1765-01) with a DBP absorption of 50 ml / 100 g. In Example 13, the elastomer contained 16 wt% of carbon black (manufactured by Tokai Carbon, Toka Black #7550SB: ASTM D 1765-01) with a DBP absorption of 53 ml / 100 g.

[0109] In Example 14, carbon black having a DBP absorption of 75 ml / 100 g (Asahi Carbon Co., Ltd., Asahi #70L N326: ASTM D 1765-01) was contained in the elastomer at 16 wt %. In Example 15, carbon black having a DBP absorption of 110 ml / 100 g (Asahi Carbon Co., Ltd., Asahi #60U N550: ASTM D 1765-01) was contained in the elastomer at 16 wt %. In Example 16, carbon black having a DBP absorption of 126 ml / 100 g (Nitelon #300IH N234: ASTM D 1765-01) was contained in the elastomer at 16 wt %. In Example 17, the elastomer contained 16 wt % of carbon black (manufactured by Nippon Steel Carbon Co., Ltd., Nitelon #SH N765: ASTM D 1765-01) having a DBP absorption of 140 ml / 100 g.

[0110] The sealing body is composed of only an elastomer. The elastomer in Examples 11 to 17 is composed of 32 wt% elastomer, 16 wt% carbon, 42 wt% inorganic filler, vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent. The entire elastomer is regular butyl. The vulcanizing agent, stearic acid, zinc oxide, and silane coupling agent were added so that the total amount was 10 wt%.

[0111] Three types of electrolytes were prepared: electrolyte types A to C. The solvent for electrolyte type A was composed of 40 wt% glycerin and 60 wt% ethylene glycol. The solvent for electrolyte type B was composed of 60 wt% glycerin and 40 wt% ethylene glycol, and the solvent for electrolyte type C was composed of 80 wt% glycerin and 20 wt% ethylene glycol. The electrolyte for electrolyte types A to C was ammonium azelaate, which was added at a rate of 0.16 mol per 1 kg of electrolyte.

[0112] Electrolytic capacitors combining the elastic bodies of Examples 11 to 17 with electrolyte solution type A are referred to as Examples 11A to 17A. Electrolytic capacitors combining the elastic bodies of Examples 11 to 17 with electrolyte solution type B are referred to as Examples 11B to 17B. Electrolytic capacitors combining the elastic bodies of Examples 11 to 17 with electrolyte solution type C are referred to as Examples 11C to 17C. These electrolytic capacitors were produced using the same manufacturing method and under the same manufacturing conditions as Example 1, except for the elastic bodies and electrolyte solution, and have the same configuration as Example 1.

[0113] For each of Examples 11A-C to 17A-C, the electrolytic capacitors were also exposed to a high-temperature environment at 170°C. The capacitance (Cap) of each electrolytic capacitor was measured immediately before exposure to the high-temperature environment and after 1,400 hours of exposure to the high-temperature environment, and ΔCap (%), which is the rate of change in capacitance before and after exposure to the high-temperature environment, was calculated. The capacitance measurement method was the same as in Example 3.

[0114] Furthermore, after 1,400 hours of exposure to a high-temperature environment, the leakage current (μA) of each electrolytic capacitor was measured as a value measured on an oscilloscope 120 seconds after applying 35 V in a 20°C temperature environment.

[0115] The capacitance change rate ΔCap and leakage current of the electrolytic capacitors of Examples 11A to 17A are shown in Table 4 below. The capacitance change rate ΔCap and leakage current of the electrolytic capacitors of Examples 11B to 17B are shown in Table 5 below. The capacitance change rate ΔCap and leakage current of the electrolytic capacitors of Examples 11C to 17C are shown in Table 6 below.

[0116] (Table 4)

[0117] (Table 5)

[0118] (Table 6)

[0119] As shown in Table 4, the electrolytic capacitors of Examples 11A to 17A all have excellent ΔCap. Furthermore, the electrolytic capacitors of Examples 11A to 14A are superior to Examples 15A to 17A in that they have low leakage current, at most about 1 / 95th of that of Examples 15A to 17A.

[0120] As shown in Table 5, the electrolytic capacitors of Examples 11B to 17B are all excellent in ΔCap. Furthermore, the electrolytic capacitors of Examples 11B to 14B are excellent in that they have a low leakage current, which is up to about 1 / 126 of that of Examples 15B to 17B.

[0121] As shown in Table 6, the electrolytic capacitors of Examples 11C to 17C all have excellent ΔCap. Furthermore, the electrolytic capacitors of Examples 11C to 14C are superior to Examples 15C to 17C in that their leakage currents are as low as 1 / 200 at most.

[0122] In the electrolytic capacitors of Examples 11A to 14A, 11B to 14B, and 11C to 14C, carbon black with a DBP absorption of 80 ml / 100 g or less was contained in the elastic body of the sealing body, which prevented not only the decrease in capacitance but also the increase in leakage current in high-temperature environments.

[0123] Therefore, it was confirmed that by making the elastic body of the sealing body contain 31 wt% or more of butyl rubber, making the electrolyte contain 40 wt% or more of glycerin, diglycerin, or both in a solvent, making the elastic body contain a total of 50 wt% to 60 wt% of carbon and inorganic filler, and using carbon black with a DBP absorption of 80 ml / 100 g or less, not only is the change in capacitance suppressed, but the leakage current of the electrolytic capacitor is also dramatically suppressed.

[0124] (Examples 18A-B to 22A-B) Electrolytic capacitors of Examples 18A to 22A and Examples 18B to 22B were fabricated. The electrolytic capacitors of Examples 18A to 22A had the same configuration as Example 1, except that the amount of electrolyte was different from that of Example 1, and the amount of glycerin in the electrolyte was 40 wt % with respect to the total amount of solvent. The electrolytic capacitors of Examples 18B to 22B had the same configuration as Example 3, except that the amount of electrolyte was different from that of Example 3, and the amount of glycerin in the electrolyte was 60 wt % with respect to the total amount of solvent.

[0125] The sealing bodies used in the electrolytic capacitors of Examples 18A to 22A and Examples 18B to 22B were cylindrical and had a radius of 4.72 mm and a height of 2.5 mm. By changing the weight of the electrolyte contained in the electrolytic capacitors of Examples 18A to 22A and Examples 18B to 22B, the electrolyte loading coefficients R of the electrolytic capacitors were adjusted as follows:

[0126] That is, the electrolyte loading coefficient R of Examples 18A and 18B is 5.00 mg mm / mm ２ The electrolyte loading coefficient R of Examples 19A and 19B was 4.29 mg mm / mm ２ The electrolyte loading coefficient R of Examples 20A and 20B was 3.93 mg mm / mm ２ The electrolyte loading coefficient R of Examples 21A and 21B was 3.57 mg mm / mm ２ The electrolyte loading coefficient R of Examples 22A and 22B was 3.21 mg mm / mm ２ It was.

[0127] For Examples 18A to 22A and 18B to 22B, the electrolytic capacitors were also exposed to a high-temperature environment at 170°C. The capacitance (Cap) of each electrolytic capacitor was measured immediately before exposure to the high-temperature environment and after 1,400 hours of exposure to the high-temperature environment, and ΔCap (%), which is the rate of change in capacitance before and after exposure to the high-temperature environment, was calculated. The capacitance measurement method was the same as in Example 3.

[0128] After 1400 hours of exposure to a high-temperature environment, the tan δ of each electrolytic capacitor was measured at room temperature using an LCR meter. The measurement frequency for tan δ was 120 Hz, and the AC amplitude was a sine wave of 0.5 Vms.

[0129] The capacitance change rates ΔCap and tanδ of the electrolytic capacitors of Examples 18A to 22A are shown in Table 7 below. The capacitance change rates ΔCap and tanδ of the electrolytic capacitors of Examples 18B to 22B are shown in Table 8 below. The results of Tables 7 and 8 below are shown in the graph of Figure 2. In Figure 2, the horizontal axis is the electrolyte loading coefficient R and the vertical axis is tanδ, with the circle plots representing the series of Examples 18A to 22A and the triangle plots representing the series of Examples 18B to 22B.

[0130] (Table 7)

[0131] (Table 8)

[0132] As shown in Table 7 and the circled series in Figure 2, the electrolytic capacitors of Examples 18A to 22A all have excellent ΔCap. Furthermore, the electrolytic capacitors of Examples 18A to 20A have significantly lower tanδ than Examples 21A and 22A. As shown in Table 8 and Figure 2, the electrolytic capacitors of Examples 18B to 22B all have excellent ΔCap. Furthermore, the electrolytic capacitors of Examples 18B to 20B have significantly lower tanδ than Examples 21B and 22B.

[0133] The electrolytic capacitors of Examples 18A to 20A and Examples 18B to 20B all had an electrolyte loading coefficient R of 3.93 mg mm / mm ２ The dimensions of the electrolyte and the sealing member are adjusted so that the above-mentioned values ​​are achieved. As a result, the electrolytic capacitor not only prevents a decrease in capacitance in a high-temperature environment, but also suppresses tan δ.

[0134] In this way, the elastic body of the sealing body contains 31 wt % or more of butyl rubber, the electrolyte contains 40 wt % or more of glycerin, diglycerin, or both in a solvent, and the elastic body contains a total of 50 wt % to 60 wt % of carbon and inorganic filler, and the electrolyte loading coefficient R is 3.93 mg mm / mm ２ By doing so, it was confirmed that not only was the change in capacitance suppressed, but also the tan δ of the electrolytic capacitor could be reduced.

Claims

1. An electrolytic capacitor comprising: a capacitor element having an anode body, a cathode body, an electrolytic solution, and a solid electrolyte; a case that houses the capacitor element; and a sealing body that seals the case; wherein the sealing body has an elastic body containing an elastomer, the elastomer containing butyl rubber and comprising 31 wt% or more of the elastomer relative to the elastic body; and the electrolytic solution containing 40 wt% or more of glycerin, diglycerin, or both in a solvent of the electrolytic solution.

2. The electrolytic capacitor according to claim 1, wherein the content of the elastomer is 36 wt % or less relative to the elastic body.

3. The electrolytic capacitor according to claim 1 or 2, wherein the sealing body has a bending strain change rate of -30% or less in a three-point bending test according to JIS K7171 after being exposed to a temperature environment of 170°C for 1000 hours.

4. The electrolytic capacitor according to claim 1 or 2, wherein the elastic body contains a total of 50 wt % to 60 wt % of carbon and inorganic filler.

5. The electrolytic capacitor according to claim 4, wherein the carbon is carbon black having a dibutyl phthalate absorption of 80 ml / 100 g or less.

6. The electrolyte has an electrolyte loading coefficient R of 3.93 mg mm / mm, as shown in the following formula (1). ２ 5. The electrolytic capacitor according to claim 4, wherein:

7. The electrolytic capacitor according to claim 1 or 2, wherein the butyl rubber is cross-linked with an alkylphenol resin.

8. The electrolytic capacitor according to claim 1 or 2, wherein the electrolyte contains ethylene glycol, sulfolane, or both.

9. A method for manufacturing an electrolytic capacitor, comprising: an element forming step of a capacitor element having an anode body, a cathode body, and a solid electrolyte; an impregnation step of impregnating the capacitor element with an electrolyte solution containing 40 wt % or more of glycerin, diglycerin, or both in the solvent of the electrolyte solution; an accommodating step of accommodating the capacitor element in a case; and a sealing step of sealing the case with a sealing body having an elastic body containing an elastomer, the elastomer including butyl rubber, and the elastomer content relative to the elastic body being 31 wt % or more.

10. The method for manufacturing an electrolytic capacitor according to claim 9, further comprising the step of producing the sealing body such that, after being exposed to a temperature environment of 170°C for 1000 hours, the bending strain change rate is within -30% in a three-point bending test according to JIS K7171.

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