Sealing body and electrolytic capacitor

Abstract

This invention provides a sealing body that inhibits thermal oxidation degradation, and an electrolytic capacitor including the sealing body. The sealing body seals the opening of a casing housing a capacitor element in which an anode foil and a cathode foil with a dielectric oxide film are facing each other and the capacitor element is impregnated with electrolyte. The sealing body includes an elastomeric component containing an elastomer such as butyl rubber. The initial crosslinking density of the elastomer is 1.8 × 10⁻³ mol / g or higher, and its content relative to the total elastomer component is 30 wt% or less.

Description

Sealing body and electrolytic capacitor The present invention relates to a sealing body for sealing the casing of an electrolytic capacitor, and an electrolytic capacitor including the sealing body. An electrolytic capacitor comprises a valve-acting metal, such as tantalum or aluminum, as an anode foil and a cathode foil. The anode foil is expanded by shaping the valve-acting metal into a sintered body or etched foil, and a dielectric oxide film is formed on the expanded surface. An electrolyte is present between the anode foil and the cathode foil. The electrolyte is in close contact with the uneven surface of the anode foil, functioning as the actual cathode. The electrolytic capacitor obtains anode-side capacitance through the dielectric polarization effect of the dielectric oxide film. In the electrolytic capacitor, to suppress the evaporation of the electrolyte formed by adding an electrolyte, a capacitor element consisting of an anode foil and a sealing body is sealed (see, for example, Patent Document 1). The sealing body is a component that seals the opening of the bottomed cylindrical shell housing the capacitor element. The sealing body is pressed tightly against the opening of the shell and includes an elastic member of appropriate hardness to improve sealing. For example, the sealing body includes an elastomer member such as butyl rubber. The elastomer member is manufactured by vulcanization for cross-linking. Electrolytic capacitors can also be envisioned for use in high-temperature environments, such as in automotive applications. In high-temperature environments, the sealing body may undergo thermal oxidative degradation on the outer side of the casing. Specifically, the CH bonds of the elastomer molecules break, generating free radicals. First, these free radicals attack another CH bond in the elastomer molecule, promoting further cracking. Second, these free radicals add oxygen to form peroxides. These peroxides decompose due to heat, accelerating the generation of free radicals, which then attack another CH bond in the elastomer molecule, promoting further cracking. If this operation is repeated, the chain length of the elastomer molecules gradually shortens, and the elastomer component gradually softens. Elastomers that have undergone low molecular weight reduction are prone to vaporization. Furthermore, when elastomers with shortened chain lengths recombine, their density increases. Therefore, the elastomer component gradually shrinks. This shrinkage is most pronounced on the outer side of the sealed body, which is more easily exposed to heat or oxygen, and the degree of shrinkage gradually decreases from the outer side of the sealed body towards the inner side. On the other hand, swelling of the elastomeric components caused by the electrolyte occurs inside the casing of the seal. This creates contraction and expansion areas within the seal, leading to rupture of the elastomeric components. When the seal ruptures, electrolyte leakage, increased evaporation, and the introduction of moisture into the electrolytic capacitor can easily occur, resulting in a shortened lifespan for the electrolytic capacitor. Therefore, as in Patent Document 1, a sealing body is proposed, which is formed by laminating a fluoropolymer integrally bonded to the electrolyte-side surface of an elastomer component after forming an elastomer component. Furthermore, as in Patent Document 2, a crosslinking density of 0.5 mol / cm³ for the elastomer is proposed. 3 ×10 -4 ~10 mol / cm 3 ×10 -4 [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. Sho 59-80925 [Patent Document 2] Japanese Patent Application Publication No. Hei 05-283302 [Problem to be Solved by the Invention] Patent Document 1 proposes to reduce the contact opportunity between the electrolyte and the elastomer component on the inner side of the sealing body by using fluororesin, thereby suppressing the swelling of the elastomer component. Patent Document 2 proposes to reduce the crosslinking density so that the elasticity of the elastomer component remains even after thermal oxidation degradation. However, the proposals in Patent Documents 1 and 2 are countermeasures based on thermal oxidation degradation and do not achieve the suppression of thermal oxidation degradation. This invention was proposed to solve the aforementioned problems, and its object is to provide a sealing body that suppresses thermal oxidation degradation, and an electrolytic capacitor including the sealing body. [Means for Solving the Problems] To address the aforementioned problem, the sealing body of the present invention is characterized by comprising an elastomeric member containing an elastomer, wherein the initial crosslinking density of the elastomer is 1.8 × 10⁻⁶. -3 The content is above mol / g, and below 30 wt% relative to the total content of the elastomer component. When the initial crosslinking density is 1.8 × 10 -3 At concentrations above mol / g, crosslinking suppresses the vibration of the elastomer caused by heat, making the elastomer less prone to cracking. That is, the elastomer component is less likely to soften. However, the crosslinking density tends to decrease over time. On the other hand, when the elastomer content is set to 30 wt% or less relative to the total elastomer component, the decrease in crosslinking density can be suppressed. This allows for long-term suppression of elastomer cracking. Furthermore, through long-term suppression of elastomer cracking, the degree of elastomer vaporization or recombination is reduced, and the shrinkage of the elastomer component becomes slower. That is, thermal oxidative degradation can be suppressed for a long time. The initial crosslinking density of the elastomer can be 2.5 × 10⁻⁶. -3 mol / g or higher. When the initial crosslinking density becomes 2.5 × 10⁻⁶ -3 At concentrations above mol / g, robust crosslinking inhibits the decrease in crosslinking density. This, combined with the effect of setting the elastomer content to below 30 wt% relative to the overall elastomer component, further suppresses the decrease in crosslinking density, resulting in slower cracking of the elastomer and more gradual shrinkage of the elastomer component. In other words, thermal oxidative degradation can be suppressed for a longer period. The elastomeric component may further include carbon and inorganic fillers. The interaction between the elastomer and the carbon or inorganic filler can also suppress the reduction of crosslink density. The inorganic filler may include a flattened inorganic filler. The flattened inorganic filler may be talc, mica, or both. Flattened inorganic fillers further enhance the effect of suppressing the reduction of crosslink density through interaction with the elastomer. The elastomer can be cross-linked with a resin. In the cross-linking of the elastomer, the resin cross-linking is strong, and the strong cross-linking inhibits the decrease in cross-linking density. The elastomer can be butyl rubber. Butyl rubber has higher heat resistance than other elastomers, thus it is less prone to oxidative degradation. Furthermore, butyl rubber is non-polar, while the organic solvent used in the electrolyte is polar. Therefore, butyl rubber is less likely to swell due to the electrolyte compared to other elastomers. Consequently, when the elastomer is butyl rubber, the volume difference between the inner and outer sides of the seal body is less likely to occur compared to the outer side of the seal body, which shrinks due to thermal oxidation. Therefore, the seal body is less prone to cracking. The change rate of crosslink density after exposure at 150°C for 500 hours is limited to within -60% compared to the initial value. Consequently, the change in hardness after exposure at 150°C for 1000 hours is limited to within -2% compared to the initial value. When the hardness change is limited to within -2% compared to the initial value, the shrinkage of the sealant becomes slow. The following electrolytic capacitor is also a form of the present invention, the electrolytic capacitor comprising: the sealing body; a housing, sealed by the sealing body; and a capacitor element housed in the housing, wherein an anode foil and a cathode foil having a dielectric oxide film formed thereon face each other and are impregnated with electrolyte. The shrinkage of the sealing body becomes slower, and the thermal oxidative degradation of the sealing body is suppressed for a longer period of time, thereby inhibiting the evaporation of electrolyte from the electrolytic capacitor to the outside through the sealing body. Therefore, the time-dependent deterioration of the electrostatic capacitance or dielectric loss tangent (tanδ) of the electrolytic capacitor is reduced. Consequently, the lifespan of the electrolytic capacitor is extended. It may further include a solid electrolyte layer formed within the capacitor element and comprising a conductive polymer. The effect of suppressing the decrease in crosslinking density is that the shrinkage of the elastomer component becomes slower, thermal oxidative degradation is suppressed for a longer period of time, and oxygen is prevented from penetrating from the outside into the electrolytic capacitor. Therefore, not only is the thermal oxidative degradation of the sealing body suppressed, but also the oxidative degradation of the conductive polymer in the electrolytic capacitor is suppressed. This reduces the time-dependent deterioration of electrostatic capacitance or dielectric loss tangent (tanδ) caused by the oxidative degradation of the conductive polymer. Therefore, the lifespan of the electrolytic capacitor, which simultaneously has an electrolyte and a solid electrolyte layer, is extended. [Effects of the Invention] According to the present invention, thermal oxidative deterioration of the sealing body can be suppressed. The sealing body and electrolytic capacitor according to embodiments of the present invention will be described below. Furthermore, the present invention is not limited to the embodiments described below. (Overview of Electrolytic Capacitors) Electrolytic capacitors are passive components that store and discharge electrical charge through electrostatic capacitance. The capacitor element of an electrolytic capacitor includes an anode foil, a cathode foil, a separator, and an electrolyte, and is either wound or laminated. A dielectric oxide film is formed on the surface of the anode foil. The anode foil and cathode foil face each other across the separator. The electrolyte fills the voids in the capacitor element, maintaining close contact with the dielectric oxide film, thus functioning as the true cathode. The electrolyte in an electrolytic capacitor can consist of any liquid, or a solid electrolyte can be used. Furthermore, the electrolyte can be kept in a liquid state or gelled. The capacitor element is housed in a casing and sealed using a sealing body. The casing is a bottomed cylindrical shape that houses the capacitor element, for example, made of aluminum. The sealing body is installed in the opening of the casing by a pressing process to seal the opening. Lead-out terminals are connected to the anode and cathode foils, and external terminals are electrically connected to these connection terminals. The external terminals are led to the outside through a through-hole in the sealing body. (Sealing Body) The sealing body includes an elastomer component with elasticity to improve the tightness with the shell through compression processing and to ensure insulation. The elastomer component includes an elastomer. Examples of elastomers include isobutylene isoprene rubber, also known as butyl rubber; ethylene propylene diene rubber, also known as EPDM; styrene butadiene rubber; isoprene rubber; fluororubber; acrylic rubber; and natural rubber. These elastomers are produced by vulcanization such as resin vulcanization, peroxide vulcanization, sulfur vulcanization, quinone vulcanization, and polyol vulcanization, and thermoplastic elastomers are also included. One or more elastomers may be used. Examples of vulcanizing agents include benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, and alkylphenol formaldehyde resins. Crosslinking accelerators include zinc oxide, magnesium oxide, lead peroxide, dibenzothiazole disulfide, 1,2-polybutadiene, triallyl cyanurate, metal salts of methacrylic acid and acrylic acid, and N,N'-m-phenylene dimaleimide. By combining these vulcanizing agents and crosslinking accelerators individually or in combination, and by selecting specific agents for each type of elastomer, the initial crosslinking density of the elastomer can be adjusted. In addition to the elastomer, the elastomeric component may also contain carbon and inorganic fillers. When carbon and inorganic fillers are added, the elastomer is less prone to cracking, and the softening of the elastomeric component is suppressed. Examples of inorganic fillers include talc, mica, silica, kaolin, titanium dioxide, alumina, and mixtures thereof, with talc or mica having a flattened shape being preferred. Inorganic fillers with a flattened shape are preferably used to promote crosslinking and adjust the crosslinking density. In this type of elastomer component, the initial crosslinking density of the elastomer is adjusted to 1.8 × 10⁻⁶. -3 mol / g or higher. The so-called initial crosslinking density is the crosslinking density before the sealant is exposed to high-temperature air for a long time. Specifically, the initial crosslinking density also includes the crosslinking density during the stage of manufacturing the sealant or assembling the manufactured sealant into the electrolytic capacitor. In addition, the electrolytic capacitor is exposed to high-temperature environment during the aging or reflow steps, but since these steps are at most a short time of a few seconds to about 6 hours, the crosslinking density does not change significantly. The crosslinking density of the sealant of the electrolytic capacitor after the aging or reflow steps is also included in the initial crosslinking density. The crosslinking density is calculated by the Flory-Rehner formula expressed by the following formula (1). Furthermore, the swelling volume v is measured after the elastomer is immersed in cyclohexane solution and left to stand in the dark for 72 hours in a room temperature environment set at 20 degrees Celsius or higher and 25 degrees Celsius or lower. (Equation 1) n: Crosslinking density (mol / g) v 2=v 0 / vv 0: Volume before swelling; v: Volume after swelling; χ: Interaction coefficient between the elastomer and cyclohexane; V: Mole volume of cyclohexane (mol / mol) Furthermore, the elastomer content was adjusted to be 30 wt% or less relative to the overall elastomer component. When the elastomer content is 30 wt% or less relative to the overall elastomer component, the time-dependent decrease in crosslinking density can be suppressed. Therefore, when the initial crosslinking density of the elastomer is 1.8 × 10⁻⁶, -3 When the crosslinking density is above mol / g and the elastomer content is set to be below 30 wt% relative to the total elastomer component, a high crosslinking density can be maintained for a long period. That is, when the crosslinking density is high, the crosslinking effectively suppresses the vibration of the elastomer caused by heat, and the elastomer is less prone to cracking. Furthermore, if a high crosslinking density can be maintained for a long period, the rate of cracking of the elastomer during this period becomes slower, the rate of re-bonding of the elastomer also becomes slower, and as a result, the rate of shrinkage of the sealing body also becomes slower. In other words, the thermal oxidative degradation of the sealing body is suppressed. Furthermore, when the elastomer is butyl rubber, resin vulcanization is preferred as the vulcanization method. When butyl rubber is resin vulcanized, it exhibits a robust cross-linked structure and has the effect of inhibiting the decrease in cross-linking density. The optimal initial crosslinking density of the elastomer is 2.5 × 10⁻⁶. -3 Above mol / g. Adjusted to 2.5 × 10⁻⁶. -3 With a higher initial crosslinking density of mol / g or higher, adjusting the elastomer content to 30 wt% or less relative to the total elastomer component slows down the cracking of the elastomer during this period. That is, softening of the elastomer component can be significantly suppressed. Furthermore, the elastomer content is preferably 27 wt% or less relative to the total elastomer component. When the elastomer content is 27 wt% or less, a high crosslinking density can be maintained for a longer period, suppressing the final softening of the elastomer component to a mild degree. As an elastomer, isobutylene-isoprene rubber, also known as butyl rubber, is particularly preferred. The electrolyte does not easily penetrate the elastomer component containing butyl rubber, thereby suppressing swelling on the inner side of the elastomer component's shell. Therefore, in the elastomer component containing butyl rubber, the difference in volume change between the inner shell swelling due to electrolyte penetration and the outer shell shrinking due to thermal oxidation is reduced. Consequently, the elastomer component is less prone to cracking. The sealing element can also be provided by laminating rigid resin sheets into the elastomer component, or by encapsulating a rigid resin sheet inside the elastomer component. The rigid resin sheet improves the sealing performance within the electrolytic capacitor, protecting the elastomer component from the effects of electrolyte or heat. (Electrolytic capacitors) Electrolytic capacitors are manufactured by inserting this type of sealing body into the opening of a housing that contains capacitor elements. The anode and cathode foils of an electrolytic capacitor are foils made of a valve-acting metal. Valve-acting metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Regarding purity, the ideal purity for the anode foil is above 99.9%, and for the cathode foil, it is around 99% or higher, although impurities such as silicon, iron, copper, and magnesium may be present. The anode foil has an expanded layer with an expanded structure formed on one or both sides of the foil. The cathode foil can be a plain foil without an expanded layer, or it can have an expanded layer formed in the same way as the anode foil. The expanded layer includes tunnel-like pits, sponge-like pits, or dense voids between powder particles. The diffusion layer is formed by electrolytic etching, chemical etching, or sandblasting, or by vapor deposition or sintering metal particles on the foil. The dielectric oxide film on the anode foil is typically an oxide film formed on the surface of the anode foil. If the anode foil is made of aluminum, it is aluminum oxide formed by oxidizing the surface layer. This dielectric oxide film is intentionally formed by a chemical conversion treatment in a halogen-free solution by applying voltage. Examples of halogen-free solutions include aqueous solutions of adipic acid, boric acid, or phosphoric acid. An oxide film can also be intentionally formed on the surface of the cathode foil by the same chemical conversion treatment, or it can form naturally. There are no particular limitations on the solvent for the electrolyte; either protic or aprotic polar organic solvents can be used. Examples of protic polar solvents include monohydric alcohols, polyhydric alcohols, oxyhydric alcohols, and water. Examples of aprotic polar solvents include sulfonate compounds, amide compounds, lactones, cyclic amide compounds, nitrile compounds, and sulfone compounds. Examples of monohydric alcohols include: ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc. Examples of polyhydric alcohols and oxyhydric alcohols include: ethylene glycol, propylene glycol, glycerol, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, diethylene glycol, etc. Examples of sulfonium compounds include: dimethylsulfonium, ethylmethylsulfonium, diethylsulfonium, cyclobutanone, 3-methylcyclobutanone, 2,4-dimethylcyclobutanone, etc. Examples of acetamide compounds include: N-methylmethamide, N,N-dimethylmethamide, N-ethylmethamide, N,N-diethylmethamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphatamide, etc. Examples of lactones and cyclic acetamides include: γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylparaben carbonate, propylparaben carbonate, butylparaben carbonate, isobutylparaben carbonate, etc. Examples of nitrile compounds include acetonitrile, 3-methoxypropionitrile, and glutaronitrile. Examples of urethane compounds include dimethyl urethane. Electrolytes may contain solutes. The solutes in an electrolyte may include both anionic and cationic components, typically organic acids or their salts, inorganic acids or their salts, or complex compounds of organic and inorganic acids or their salts, which may be used alone or in combination of two or more. Alternatively, acids that become anions and bases that become cations may be added separately as solute components to the electrolyte. Examples of organic acids include: oxalic acid, succinic acid, glutaric acid, heptanoic acid, octanoic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, heptanoic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and other carboxylic acids, phenols, and sulfonic acids. Examples of inorganic acids include: boric acid, phosphoric acid, phosphorous acid, hypophosphite, carbonic acid, and silicic acid. Examples of complex compounds of organic and inorganic acids include: borodisalicylic acid, borodioxalic acid, and borodiglycolic acid. Examples of salts of organic acids, inorganic acids, and complex compounds of organic and inorganic acids include: ammonium salts, quaternary ammonium salts, quaternary amidine salts, amine salts, sodium salts, and potassium salts. Examples of quaternary ammonium ions as quaternary ammonium salts include: tetramethylammonium, triethylmethylammonium, and tetraethylammonium. Examples of quaternary amidine salts include: ethyldimethylimidazolinenium and tetramethylimidazolinenium. Examples of amine salts include: primary amines, secondary amines, and tertiary amines. Examples of primary amines include: methylamine, ethylamine, and propylamine; examples of secondary amines include: dimethylamine, diethylamine, ethylmethylamine, and dibutylamine; and examples of tertiary amines include: trimethylamine, triethylamine, tripropylamine, tributylamine, ethyldimethylamine, and ethyldiisopropylamine. Furthermore, other additives can be added to the electrolyte. Examples of additives include: polyethylene glycol, polypropylene glycol, polyoxyethylene glycerol, compounds of boric acid and polysaccharides (mannitol, sorbitol, etc.), compounds of boric acid and polyols, borate esters, nitro compounds, phosphate esters, colloidal silicon dioxide, etc. These can be used alone or in combination. Nitro compounds suppress the generation of hydrogen gas in electrolytic capacitors. Examples of nitro compounds include: o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, etc. In the case of a gel electrolyte, the polymer that maintains this electrolyte is a homopolymer of a single monomer or a copolymer of two or more monomers, which is cross-linked to have a three-dimensional network structure. The monomer is not particularly limited, but examples include hydroxyethyl acrylamide, 2-(diethylamino)ethyl methacrylate, 2-(tert-butylamino)ethyl methacrylate, N-isopropyl acrylamide, diacetone acrylamide, N-tert-butyl acrylamide, N,N-diethyl acrylamide, N-vinyl acetamide, 2-hydroxyethyl methacrylate, methacrylic acid, or methoxy polyethylene glycol methacrylate, etc., and one or more monomers may be selected from this group. In the case of using a solid electrolyte layer, the solid electrolyte layer is a layer containing a conductive polymer. The conductive polymer is a conjugated polymer or a doped conjugated polymer. Known conjugated polymers can be used without particular limitation. Examples include: polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. These conjugated polymers can be used alone, or in combination of two or more, and further, they can be copolymers of two or more monomers. Among the conjugated polymers, those polymerized from thiophene or its derivatives are preferred, particularly those polymerized from 3,4-epethyldioxythiophene (i.e., 2,3-dihydrothiophene[3,4-b][1,4]dioxin), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, or their derivatives. As thiophene derivatives, compounds selected from thiophenes having substituents at the 3 and 4 positions are preferred, wherein the substituents at the 3 and 4 positions of the thiophene ring can form a ring together with the carbons at the 3 and 4 positions. The number of carbon atoms in the alkyl or alkoxy group is preferably 1 to 16, especially preferably a polymer of 3,4-ethylenedioxythiophene called EDOT (3,4-ethylenedioxythiophene), i.e., poly(3,4-ethylenedioxythiophene) called PEDOT (poly(3,4-ethylenedioxythiophene)). Alternatively, it can be an alkylated ethylenedioxythiophene with an alkyl group added to 3,4-ethylenedioxythiophene, for example: 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), etc. Dopant may be any known additive without particular limitation. Examples include inorganic acids such as boric acid, nitric acid, and phosphoric acid; and organic acids such as acetic acid, oxalic acid, citric acid, aconitic acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzene disulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bis(oxalato)boronic acid, sulfonylaminoimino acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid. Additionally, as polyanionic additives, examples include: polyvinylsulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid. As a conductive polymer, a representative example is poly(3,4-epoxythiophene) doped with polystyrene sulfonic acid (PSS), known as PEDOT. The solid electrolyte layer is formed by immersing the capacitor element in a dispersion of a conductive polymer in a solvent and then drying it. The anode foil, cathode foil, and separator can be immersed in the dispersion separately before assembly, or they can be applied by drop coating or spray coating. The partition can be made from kraft paper, Manila hemp, esparto, hemp, rayon and other cellulose and their blends, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and their derivatives, polyester resins, polytetrafluoroethylene resins, polyvinylidene fluoride resins, vinylon resins, aliphatic polyamines, semi-aromatic polyamines, fully aromatic polyamines and other polyamine resins, polyimide resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, polyvinyl alcohol resins, etc. These resins can be used alone or in combination. The electrolytic capacitor achieves a long lifespan by slowing down the shrinkage of the sealing body and suppressing the thermal oxidation degradation of the sealing body over a long period of time. That is, since the evaporation of the electrolyte from the electrolytic capacitor to the outside through the sealing body is suppressed, the time-related deterioration of the electrostatic capacitance or the time-related deterioration of the dielectric loss tangent (tanδ) of the electrolytic capacitor is reduced. Furthermore, suppressing the decrease in crosslinking density slows down the shrinkage of the elastomer component, inhibits thermal oxidative degradation, and thus prevents oxygen from penetrating into the electrolytic capacitor from the outside. Therefore, in the case of a hybrid type electrolytic capacitor that simultaneously has an electrolyte layer and a solid electrolyte layer, the oxidative degradation of the conductive polymer can also be suppressed. That is, the time-dependent deterioration of electrostatic capacitance or dielectric loss tangent (tanδ) caused by the oxidative degradation of the conductive polymer can also be reduced, especially in the hybrid type electrolytic capacitor, where extended lifespan can be achieved. [Example] The sealing body and electrolytic capacitor of the present invention will be further described in detail below based on embodiments. Furthermore, the present invention is not limited to the following embodiments. (Examples 1 and 2, and Comparative Examples 1 and 2) Sealing bodies of Examples 1 and 2, and Comparative Examples 1 and 2 were prepared. Each sealing body has only an elastomer component. The elastomer component is made by crosslinking a mixture of butyl rubber polymer, carbon, inorganic filler, and alkylphenol-aldehyde resin as a vulcanizing agent through resin vulcanization. Talc was used as an inorganic filler in Examples 1 and 2, and Comparative Example 2. Clay was used as an inorganic filler in Comparative Example 1. In addition, stearic acid, zinc oxide, and silane coupling agent were mixed as the remaining components in Examples 1 and 2, and Comparative Examples 1 and 2. The sealing bodies of Examples 1 and 2, as well as Comparative Examples 1 and 2, were manufactured by adjusting the composition ratio of butyl rubber polymer to carbon and inorganic filler, and by adjusting the crosslinking density, as shown in Table 1 below. Each composition ratio is relative to the overall weight of the elastomer component. (Table 1) In calculating the crosslinking density, elastomer components of various examples and comparative examples were prepared with a thickness of approximately 2 mm, a size of 1 cm × 1 cm, and each test piece weighing approximately 0.3 g. For the elastomer components, the pre-swelling volume v of the elastomer components was calculated based on the initial weight and specific gravity. 0. The elastomer component was placed in 15 ml of cyclohexane solution and allowed to stand for 72 hours in the dark at room temperature (20-25°C). After the standing period, the swollen weight of the elastomer component was measured. After the measurement, the elastomer component was dried under vacuum at 100°C for 1 hour to remove the cyclohexane. The volume of cyclohexane impregnated in the elastomer component is calculated based on its dry weight and swollen weight. The volume of the swollen elastomer component is then calculated based on the volume of cyclohexane, and the sum of the volumes of the elastomer component and cyclohexane is defined as the swollen volume *v*. Furthermore, the molecular weight of cyclohexane is set to 84.16 g / mol, and its density is set to 0.78 g / cm³. 3 The interaction coefficient χ between butyl rubber polymer and cyclohexane was set to 0.44 for calculation. (Changes in physical properties after thermal aging) The degree of thermal oxidation degradation of the sealing bodies of Examples 1 and 2, and Comparative Examples 1 and 2 was observed. That is, the sealing bodies of each example and comparative example were exposed to air at 150 degrees Celsius. Then, the change in hardness (ΔHS) and the rate of thermal shrinkage (Δdiameter) after continuous exposure to air at 150 degrees Celsius for various periods of time were measured. The results of the change in hardness are shown in Table 2 below, and the results of the rate of thermal shrinkage are shown in Table 3 below. In addition, based on Table 2 below, a graph with time on the horizontal axis and change in hardness on the vertical axis is shown in Figure 1, and based on Table 3 below, a graph with time on the horizontal axis and rate of thermal shrinkage on the vertical axis is shown in Figure 2. (Table 2) (Table 3) As shown in Table 2 and Figure 1, it can be seen that Comparative Examples 1 and 2 softened to approximately -5 after 500 hours. On the other hand, regarding the softening of Example 1, after 1000 hours, the softening also stopped at approximately -1.7, with no further softening occurring. Therefore, it can be confirmed that the elastomer of the sealing body in Comparative Examples 1 and 2 underwent a considerable degree of cracking, while the cracking of the elastomer in the sealing body of Example 1 was suppressed. Furthermore, it can be seen that the hardness change in Example 2 was positive, and the cracking of the elastomer was suppressed to a degree not exhibited in the hardness change. Furthermore, as shown in Table 3 and Figure 2, it can be seen that the thermal shrinkage of the sealing bodies in Examples 1 and 2 is smaller compared to that in Comparative Examples 1 and 2. Moreover, the sealing body of Comparative Example 1 cracked after 2000 hours. Combining Tables 2 and 3 with Figures 1 and 2, it can be seen that the cracking of the elastomers in Examples 1 and 2 is suppressed; therefore, there is less elastomer vaporization and less recombination of short-chain elastomers, thus suppressing the shrinkage of the sealing body. (Changes in crosslinking density) Here, the crosslinking density of Comparative Example 2 is higher than that of Example 1. However, compared with Comparative Example 2, the softening of Example 1 was suppressed, and as a result, the thermal shrinkage rate was also suppressed. Therefore, the changes in the crosslinking density of the sealing bodies of Examples 1, 2, and Comparative Example 2 were measured. That is, the sealing bodies of each example and comparative example were exposed to a temperature environment of 150 degrees Celsius, and the crosslinking density before exposure to the temperature environment and after continuous exposure to the temperature environment for 500 hours and 1000 hours were measured, and the rate of change of crosslinking density was calculated. The measurement results are shown in Table 4 below. (Table 4) As shown in Table 4, in Comparative Example 2, where the initial crosslinking density was higher than that of Example 1, the crosslinking density decreased significantly after 500 hours, becoming lower than that of Example 1. This confirms that the sealing material of Comparative Example 2 did not maintain a high crosslinking density for an extended period; the crosslinking density decreased rapidly. Therefore, in other words, the crack suppression of the elastomer only lasted for a short time, and the cracking of the elastomer became severe, with greater shrinkage than in Example 1. The difference between Example 1 and Comparative Example 2 lies in the content ratio of the elastomer in the elastomer component. In other words, it was confirmed that, not only was the initial crosslinking density of the elastomer set to 1.8 × 10⁻⁶ as in Comparative Example 2, but... -3 Furthermore, as in Example 1 or Example 2, the content of the elastomer relative to the total elastomer component is further set to 30 wt% or less, thereby slowing down the change in crosslinking density, suppressing the cracking of the elastomer, and suppressing the shrinkage of the elastomer component. That is, it is confirmed that thermal oxidative degradation is suppressed. Furthermore, it was confirmed that, as shown in Example 2, when the content of the elastomer relative to the total elastomer component is set to 27 wt% or less, the change in crosslinking density can be further suppressed. When the initial crosslinking density is 2.5 × 10⁻⁶, the change in crosslinking density can be further suppressed. -3 At concentrations above mol / g, softening is barely observable, and shrinkage is most effectively suppressed. (Examples 3 and 4 and Comparative Example 3) Electrolytic capacitors of Examples 3 and 4 and Comparative Example 3 were made using the sealing bodies of Examples 1 and 2 and Comparative Example 2. These electrolytic capacitors are a so-called hybrid type that uses both an electrolyte and a solid electrolyte layer. In the electrolytic capacitors of Examples 3 and 4, and Comparative Example 3, the anode foil and cathode foil were aluminum foils, which were enlarged by etching and formed with an oxide film by chemical conversion treatment. In the chemical conversion treatment, a voltage was applied in an aqueous adipic acid solution. The oxide film of the anode foil became the dielectric oxide film of the electrolytic capacitor. Wires are connected to the anode and cathode foils respectively, and the anode and cathode foils are wound towards each other through a cellulose-based separator. The capacitor element undergoes a repair chemical transformation by immersing it in an aqueous solution of ammonium dihydrogen phosphate of the same concentration for 10 minutes. Next, a dispersion of polyvinyl dioxythiophene (PEDOT / PSS) doped with polystyrene sulfonic acid of the same product was prepared as a conductive polymer. A capacitor element was immersed in the dispersion, then lifted out and dried at 150°C for 30 minutes. This formed a solid electrolyte layer on the capacitor element. Ethylene glycol was selected as the solvent for the electrolyte. Ammonium azelate, an ion-dissociating salt, was selected as the solute in the electrolyte. The solvent and solute were mixed at a ratio of 5 wt% of ammonium azelate in the electrolyte. A capacitor element with a solid electrolyte layer formed was immersed in the electrolyte, so that the electrolyte was contained within the capacitor element. Then, the capacitor element is housed in an aluminum casing of the same size and shape. At the open end of the aluminum casing, the sealing body of Example 1 is installed on the electrolytic capacitor of Example 3, and sealed by a pressing process. The sealing body of Example 2 is installed on the electrolytic capacitor of Example 4, and sealed by a pressing process. The sealing body of Comparative Example 2 is installed on the electrolytic capacitor of Comparative Example 3, and sealed by a pressing process. Furthermore, the leads from the capacitor elements are pre-exited from the sealed body to allow energizing of the electrolytic capacitors. Each electrolytic capacitor undergoes an aging process by applying voltage at 115°C for 45 minutes. The capacitor elements of each electrolytic capacitor have a diameter of 6.3 mm and a height of 5.8 mm, and each electrolytic capacitor has a rated withstand voltage of 35 WV and a rated capacitance of 47 μF. The electrolytic capacitors of Examples 3 and 4, as well as Comparative Example 2, were exposed to a high-temperature environment of 170°C. Then, the dielectric loss tangent (tanδ), capacitance (Cap), and electrolyte leakage (ΔWt) were measured before and after exposure to the high-temperature environment for 1200 hours. Furthermore, the reduction rate (ΔCap) of the capacitance after 2000 hours relative to the capacitance before exposure to the high-temperature environment was calculated. The measurement and calculation results are shown in Table 5 below. (Table 5) As shown in Table 5, the initial characteristics of the electrolytic capacitors of Examples 3 and 4, as well as Comparative Example 3, were the same. However, when the electrolytic capacitors were exposed to a high-temperature environment such as 170°C, the characteristics of Examples 3 and 4 differed from those of Comparative Example 3. Specifically, after 1200 hours, the leakage amount ΔWt of the electrolyte from the electrolytic capacitors of Examples 3 and 4 was less than that of Comparative Example 3. Furthermore, after 1200 hours, compared to Comparative Example 3, the reduction of Cap and the deterioration of tanδ in the electrolytic capacitors of Examples 3 and 4 were suppressed. Thus, it was confirmed that the shrinkage of the elastomer slowed down, the thermal oxidative degradation of the sealing body was suppressed over a long period, and the evaporation of the electrolyte through the sealing body was also suppressed. Furthermore, the time-dependent deterioration of the electrostatic capacitance or the time-dependent deterioration of the dielectric loss tangent (tanδ) of the electrolytic capacitor was reduced. Additionally, it was confirmed that the oxidative degradation of the conductive polymer was also suppressed, which also reduced the time-dependent deterioration of the electrostatic capacitance or the time-dependent deterioration of the dielectric loss tangent (tanδ) caused by the oxidative degradation of the conductive polymer. none Figure 1 is a graph showing the change in hardness of the seal over time. Figure 2 is a graph showing the change in thermal shrinkage rate of the seal over time.

Claims

1. A sealing body, characterized in that it comprises an elastomeric component containing an elastomer, wherein the initial crosslinking density of the elastomer is 1.8 × 10⁻³ mol / g or higher, the content of the elastomer relative to the entire elastomeric component is 30 wt% or less, and the surface is not coated with fluororesin.

2. The sealing body as described in claim 1, wherein, The initial crosslinking density of the elastomer is above 2.5 × 10⁻³ mol / g, and its content relative to the overall elastomer component is below 27 wt%.

3. The sealing body as described in claim 1 or claim 2, wherein, The elastomeric component further comprises carbon and inorganic fillers.

4. The sealing body as described in claim 3, wherein, The inorganic filler includes a flat inorganic filler.

5. The sealing body as described in claim 4, wherein, The flat inorganic filler is talc, mica, or both.

6. The sealing body as described in claim 1 or claim 2, wherein, The elastomer is cross-linked with resin.

7. The sealing body as described in claim 1 or claim 2, wherein, The elastomer is butyl rubber.

8. The sealing body as described in claim 1 or claim 2, wherein, The change rate of crosslink density after exposure at 150°C for 500 hours was limited to -60% compared to the initial value.

9. The sealing body as described in claim 1 or claim 2, wherein, The hardness change after 1000 hours of exposure at 150°C is limited to within -2 compared to the initial temperature.

10. An electrolytic capacitor, characterized in that it comprises: The sealing body as described in Request 1 or Request 2; The shell is sealed by the sealing body; And capacitor elements, housed in the housing, with the anode foil and cathode foil having dielectric oxide films formed facing each other and impregnated with electrolyte.

11. The electrolytic capacitor of claim 10, further comprising a solid electrolyte layer formed within the capacitor element and comprising a conductive polymer.

Images