Sealing body, electrolytic capacitor, and method for manufacturing sealing body

Abstract

Provided are a sealing body that has improved crack resistance, an electrolytic capacitor that comprises the sealing body, and a method for manufacturing the sealing body. An elastic body that is provided to the sealing body contains 7 wt% or more of a resin vulcanization component with respect to the total amount of the elastic body, and 27 wt% or more of an elastomer with respect to the total amount of the elastic body. The sealing body is manufactured including an elastic body forming step of forming the elastic body that contains 7 wt% or more of the resin vulcanization component with respect to the total amount of the elastic body and 27 wt% or more of the elastomer with respect to the total amount of the elastic body. The electrolytic capacitor is provided with a capacitor element that has a positive electrode body, a negative electrode body, and an electrolyte. The capacitor element is accommodated in an outer case in which an opening is sealed by the sealing body described above.

Description

Sealing body, electrolytic capacitor, and method for manufacturing the sealing body

[0001] The present invention relates to an electrolytic capacitor, a sealing body for sealing the opening of an electrolytic capacitor, and a method for manufacturing the sealing body.

[0002] An electrolytic capacitor is a passive component that stores and discharges electric charge by obtaining capacitance through the dielectric polarization effect of a dielectric film. An electrolytic capacitor is equipped with valve metals such as tantalum or aluminum as the anode and cathode. The anode is enlarged by shaping the valve metal into a sintered body or etched foil. The anode has a dielectric film on its enlarged surface. An electrolyte is interposed between the anode and cathode. The electrolyte is in close contact with the uneven surface of the dielectric film and functions as a true cathode.

[0003] Electrolytic capacitors are equipped with an electrolyte solution (see, for example, Patent Document 1). The electrolyte solution creates a conductive path between the anode and cathode through ion movement. Since the electrolyte solution penetrates the uneven surface of the anode, it easily increases the contact area with the dielectric film. For this reason, electrolytic capacitors using an electrolyte solution have a large capacitance. In addition, the electrolyte solution has the effect of repairing deteriorated parts of the dielectric film, such as deterioration or damage, and reduces the leakage current (LC) of the electrolytic capacitor.

[0004] The electrolyte contains, for example, ethylene glycol or γ-butyrolactone as a solvent. Furthermore, the electrolyte contains carboxylic acids such as 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, and azelaic acid as solutes for the anionic components, and dimethylamine and ammonia as solutes for the cationic components.

[0005] Electrolytic capacitors that use a solid electrolyte are also becoming widespread (see, for example, Patent Document 2). The solid electrolyte creates a conductive path between the anode and cathode through charge transfer. The solid electrolyte has high conductivity, and electrolytic capacitors using a solid electrolyte have low equivalent series resistance (ESR).

[0006] Known solid electrolytes include manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes. Conductive polymers derived from monomers with π-conjugated double bonds, such as poly(3,4-ethylenedioxythiophene) (PEDOT), and doped with polyanions such as polystyrene sulfonic acid (PSS), are also rapidly gaining popularity.

[0007] In the case of electrolytic capacitors using an electrolyte, if the airtightness inside the outer casing is compromised, the electrolyte will evaporate and evaporate to the outside. Therefore, electrolytic capacitors using an electrolyte may experience a decrease in capacitance as they dry out. In the case of electrolytic capacitors using a solid electrolyte, the solid electrolyte can oxidize and degrade due to oxygen entering from the outside. Therefore, electrolytic capacitors using a solid electrolyte may experience an increase in ESR over time.

[0008] Therefore, in an electrolytic capacitor, the capacitor element, which consists of an anode, an electrolyte, and a cathode, is housed in an outer casing with a closed bottom at one end and an open end at the other. The opening of the outer casing is sealed with a sealing element. The sealing element is tightly fitted to the opening of the outer casing by crimping. The sealing with the sealing element enhances the airtightness inside the outer casing.

[0009] Various elastomers are used as sealing material. Typical elastomers are butyl rubber and ethylene propylene rubber. Butyl rubber is made three-dimensional by resin vulcanization. Ethylene propylene rubber is made three-dimensional by peroxide vulcanization. This vulcanization imparts excellent rubber elasticity to the elastomer, improving adhesion to the outer case (see, for example, Patent Document 3).

[0010] Japanese Patent Publication No. 07-320984, Japanese Patent Publication No. 2011-60980, Japanese Patent Publication No. 2000-173877

[0011] The sealing material deteriorates through phenomena such as the following: First, the C-H bonds of the elastomer molecules cleave due to heat, generating radicals. Secondly, these radicals attack other C-H bonds in the elastomer molecules, promoting further cleavage. Secondly, oxygen is added to these radicals, producing peroxides. These peroxides decompose due to heat, accelerating the generation of radicals, which then attack other C-H bonds in the elastomer molecules, promoting further cleavage. If this process is repeated, the chain length of the elastomer molecules shortens, making the sealing material brittle and potentially leading to cracks.

[0012] Regardless of the specific mechanism, the sealing material deteriorates and cracks due to the weather resistance of the elastomer, making it impossible to maintain the airtightness of the electrolytic capacitor. As a result, the capacitance of electrolytic capacitors using electrolyte decreases, and the ESR of electrolytic capacitors using solid electrolytes increases.

[0013] The present invention was proposed to solve the above problems, and its objective is to provide a sealing body with improved crack resistance, an electrolytic capacitor equipped with this sealing body, and a method for manufacturing the sealing body.

[0014] To solve the above problems, the sealing body of this embodiment is a sealing body that comprises an elastic body and seals the opening of an outer case housing a capacitor element, wherein the elastic body comprises 7 wt% or more of a resin vulcanizing component and 27 wt% or more of an elastomer relative to the total amount of the elastic body.

[0015] The resin vulcanization component may include a crosslinking-involved resin vulcanization component that crosslinks the elastomer and an excess resin vulcanization component that does not crosslink the elastomer.

[0016] The elastic body may include a resin crosslinked elastomer represented by the following chemical structural formula (1). In the formula, n is an integer of 1 or more, m is an integer including 0, and R １ is a methylene group or an ether group, R ２ This is an alkyl group (either at the end or within a repeating unit).

[0017] (Chem.1)

[0018] The elastic body may further contain zeolite relative to its total volume.

[0019] The zeolite may be present in an amount of 3 wt% or more relative to the total amount of the elastic body.

[0020] The zeolite may have pores with an average size of 0.3 nm or larger.

[0021] The resin vulcanization component may be a resin having a phenol skeleton, a 2,5-cyclohexanedienone skeleton, or both.

[0022] The elastomer may be butyl rubber.

[0023] Furthermore, in order to solve the above problems, the electrolytic capacitor of this embodiment comprises such a sealing body, an outer case whose opening is sealed by the sealing body, and the capacitor element housed in the outer case, wherein the capacitor element has an anode, a cathode, and an electrolyte.

[0024] The electrolyte may be an electrolyte solution, a solid electrolyte, or both.

[0025] Furthermore, in order to solve the above problems, the method for manufacturing a sealing body of this embodiment is a method for manufacturing a sealing body that seals the opening of an outer case housing a capacitor element, and includes an elastic body forming step of forming an elastic body containing 7 wt% or more of a resin vulcanizing component and 27 wt% or more of an elastomer relative to the total amount of the elastic body.

[0026] According to the present invention, the crack resistance of the sealing body is improved.

[0027] This graph shows the results of pyrolizer gas chromatography-mass spectrometry of the control sample. This graph shows the results of pyrolizer gas chromatography-mass spectrometry of the extract obtained from the sealing material of Comparative Example 1 with toluene. This graph shows the results of pyrolizer gas chromatography-mass spectrometry of the extract obtained from the sealing material of Example 1 with toluene. This graph shows the results of pyrolizer gas chromatography-mass spectrometry of the extract obtained from the sealing material of Example 2 with toluene. This graph shows the results of pyrolizer gas chromatography-mass spectrometry of the extract obtained from the sealing material of Example 3 with toluene.

[0028] The following describes an electrolytic capacitor and a manufacturing method according to an embodiment of the present invention. However, the present invention is not limited to the embodiments described below.

[0029] (Overall Structure) An electrolytic capacitor is a passive element that obtains capacitance through the dielectric polarization effect of a dielectric film and stores and discharges electric charge. This electrolytic capacitor has a capacitor element. The capacitor element comprises an anode, a cathode, a separator, and an electrolyte. A dielectric film is formed on the surface of the anode. The separator is interposed between the anode and the cathode to insulate them. The electrolyte is in close contact with the dielectric film and is interposed between the anode and the cathode, acting as a true cathode.

[0030] The electrolyte can be a liquid electrolyte, a solid electrolyte, or both. The liquid electrolyte fills the voids in the capacitor element and creates a conductive path between the anode and cathode through ion transfer. The solid electrolyte fills the voids in the capacitor element or is layered between the anode and cathode and creates a conductive path between the anode and cathode through charge transfer.

[0031] Capacitor elements have lead terminals that extend to the outside connected to the anode and cathode. These lead terminals are electrically and mechanically connected to the anode and cathode by methods such as stitching, cold welding, ultrasonic welding, or laser welding. Electrolytic capacitors are electrically connected to the mounted circuitry via these lead terminals.

[0032] The capacitor element is housed in an outer casing after lead terminals are connected to the anode and cathode. The outer casing is made of aluminum, an aluminum or manganese-containing aluminum alloy, or stainless steel. The outer casing is, for example, a cylindrical body with one end closed and the other end open. A pressure relief valve may be formed at the bottom of the outer casing. The pressure relief valve opens when the internal pressure of the outer casing exceeds a set pressure.

[0033] The opening of the outer casing is sealed by a sealing body. The sealing body is attached to the opening of the outer casing. The sealing body is then crimped, causing the opening of the outer casing to be folded inward and crushed, creating a tight seal around the entire circumference of the opening edge of the outer casing. A press-fit hole is formed in the sealing body, and the lead terminals are pulled out to the outside through this press-fit hole.

[0034] (Sealing body) This sealing body has an elastic material mainly composed of an elastomer. In addition to being an elastic material, the sealing body may be a laminate of an elastic material and a hard substrate, or it may be provided so that a hard substrate is enclosed within the elastic material.

[0035] The elastic body is composed of an elastomer and a resin vulcanization component. The elastomer is, for example, butyl rubber (also called isobutylene isoprene rubber), ethylene propylene diene rubber (also called EPDM), styrene butadiene rubber, isoprene rubber, fluororubber, acrylic rubber, natural rubber, or a composite thereof. The resin vulcanization component is, for example, alkylphenol resins such as alkylphenol formaldehyde resin.

[0036] The resin vulcanizing component is contained in the elastomer in an amount larger than the amount capable of crosslinking the elastomer. When the elastomer contains 7 wt% or more of the resin vulcanizing component based on the total weight of the elastomer, the resin vulcanizing component becomes an amount larger than the amount capable of crosslinking the elastomer. That is, in the initial stage of use of the electrolytic capacitor, there are a crosslinking-involved resin vulcanizing component and an excess resin vulcanizing component in the elastomer. The crosslinking-involved resin vulcanizing component is the resin vulcanizing component that has crosslinked the elastomer by pressure and heating during the manufacturing process. The excess resin vulcanizing component is unreacted with the elastomer during the manufacturing process and is a resin vulcanizing component that has not participated in crosslinking with the elastomer at least in the initial stage of use after the production of the electrolytic capacitor is completed.

[0037] This excess resin vulcanizing component can be detected by analysis using, for example, a gas chromatograph-mass spectrometer (GC-MS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-VIS), gel permeation chromatography (GPC), nuclear magnetic resonance analysis (NMR), and the like.

[0038] Not limited thereto, it is presumed that deterioration related to, for example, the following chemical reaction formulas (2) to (4) has occurred in the elastomer of the sealing body. In chemical reaction formulas (2) to (4), P is the initial letter of the polymer and represents, for example, a butyl component or a butyl component crosslinked with a resin.

[0039] (Chemical formulas 2 to 4)

[0040] As shown in the above chemical reaction formula (2), the C-H bond of the elastomer molecule is cleaved by heat to generate a polymer radical (P•). The polymer radical (P•) attacks another C-H bond of the elastomer molecule to promote further cleavage. Also, as shown in the above chemical reaction formula (3), oxygen (O ２When ( ) is added, polymer peroxy radicals (POO·) of the peroxide are generated. The polymer peroxy radicals (POO·) have a peroxide group. By attacking the elastomer, these polymer peroxy radicals (POO·) generate polymer radicals (P·) and hydroxyl radicals (·OH), and as shown in the above chemical reaction formula (4), they become polymer oxy radicals (PO·). The polymer oxy radicals (PO·) attack another C-H bond of the elastomer molecule to promote further cleavage.

[0041] If only the chemical reaction formulas (2) to (4) are repeated, the chain length of the elastomer molecule becomes shorter, and the elastomer member softens. The low-molecular-weight elastomer becomes more likely to vaporize. Also, when the elastomer with a short chain length is recombined, the density of the elastomer increases. Therefore, the elastomer shrinks. The shrinkage of the elastomer causes cracks in the elastomer, and the sealing ability by the sealing member decreases. That is, the airtightness inside the outer case is lost.

[0042] However, there is an excess resin vulcanization component in this elastomer. Although the excess resin vulcanization component is speculative and not limited to this, it is presumed to generate a new resin crosslinked elastomer by the following chemical reaction formula (5). Note that the following chemical reaction formula (5) takes the combination of an alkylphenol resin and a butyl component as an example. In chemical reaction formula (5), P is the initial letter of the polymer and represents an elastomer molecule.

[0043] (Chemical formula 5) In the formula, R １ is a methylene group or an ether group, R ２ is an alkyl group, and X is -CH ２ OH, a methylene group or an ether group.

[0044] As shown in the chemical reaction equation (5) above, the alkylphenol resin, which is the excess resin vulcanization component, is attacked by polymer oxy radicals (PO•) generated during the thermal oxidative degradation process, which remove hydrogen ions from the hydroxyl groups of the phenol skeleton. The polymer oxy radicals (PO•) are stabilized by the removed hydrogen ions. In other words, the number of radical species that attack other C-H bonds of the elastomer molecule is reduced.

[0045] Furthermore, polymer peroxyl radicals (POO•) are stabilized by being added to the double bond of the alkylphenol resin from which a hydrogen ion has been abstracted, via the polymer peroxide group. This reduces the number of radical species that attack other C-H bonds of the elastomer molecule. Moreover, although not limited to this, it is presumed that a resin cross-linked elastomer, as shown in chemical structural formula (6) below, is formed. In chemical structural formula (6), P is the initial letter of polymer and indicates an elastomer molecule.

[0046] (C6) In the formula, n is an integer greater than or equal to 1, m is an integer including 0, and R １ is a methylene group or an ether group, R ２ This is an alkyl group (either at the end or within a repeating unit).

[0047] The resin crosslinked elastomer shown in chemical structural formula (6) crosslinks the elastomer via polymer peroxide groups and a 2,5-cyclohexadienone skeleton. This crosslinked elastomer, via polymer peroxide groups and a 2,5-cyclohexadienone skeleton, acts as a new elastic body, supplementing the degraded elastic body and maintaining the rubber elasticity of the elastic body. Therefore, it is presumed that the formation of this new elastic body suppresses crack formation in the elastic body.

[0048] Therefore, by incorporating 7 wt% or more of the resin vulcanization component relative to the total weight of the elastic body, cracks in the sealing body are suppressed. This suppression of cracks maintains airtightness within the outer casing. Consequently, electrolytic capacitors using electrolytes are less prone to capacitance reduction. Furthermore, electrolytic capacitors using solid electrolytes are less prone to ESR increase.

[0049] Further, preferably, a large amount of elastomer, such as 27 wt% or more based on the total weight of the elastomer, is intentionally included in the sealing body so as to promote the reaction between the excess resin vulcanization component and the elastomer and generate the resin-crosslinked elastomer represented by the above chemical structural formula (6).

[0050] The resin-crosslinked elastomer represented by this chemical structural formula (6) may be detected by analysis using, for example, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, nuclear magnetic resonance analysis (NMR), or the like.

[0051] The resin-crosslinked elastomer formed by the resin crosslinking component is said to have the following chemical structural formula (7) according to the chroman theory and the following chemical structural formula (8) according to the methylene quinone theory.

[0052] (Chemical Formula 7) In the formula, R １ is a methylene group or an ether group, R ２ is an alkyl group (either at the end or in the repeating unit), and n is an integer of 10 or less including 0.

[0053] (Chemical Formula 8) In the formula, R １ is a methylene group or an ether group, R ２ is an alkyl group (either at the end or in the repeating unit), and n is an integer of 10 or less including 0.

[0054] That is, in this sealing body, through the manufacturing process, in the case of butyl rubber, the resin-crosslinked elastomer of chemical structural formula (7), the resin-crosslinked elastomer of chemical structural formula (8), or both resin-crosslinked elastomers are included. Further, it is presumed that a resin-crosslinked elastomer represented by chemical structural formula (6), which is different from chemical structural formulas (7) and (8), is newly generated by the polymer radical generated in the process of elastomer deterioration and the excess resin vulcanization component, compensating for the deteriorated elastomer.

[0055] However, the elastomer should be at least 27 wt% of the total weight of the elastic body. When the elastomer is at least 27 wt% of the total weight of the elastic body, the reaction shown in chemical equation (4) between the excess resin vulcanizing component and the elastomer becomes possible. In other words, if the elastomer is less than 27 wt% of the total weight of the elastic body, it is difficult to obtain a sufficient new elastic body, and the crack suppression effect on the elastic body is insufficient.

[0056] Furthermore, the resin vulcanizing component is preferably included in the elastic body in an amount of less than 20 wt% of the total weight of the elastic body, and the elastomer is preferably included in the elastic body in an amount of less than 45 wt% of the total weight of the elastic body. If 20 wt% of the resin vulcanizing component is included in the elastic body in an amount of the total weight of the elastic body, the crack resistance of the sealing body is effective, but the stickiness of the elastic body increases. When the viscosity of the elastic body increases, the ease of kneading the elastic body decreases. Also, if 45 wt% of the elastomer is included in the elastic body in an amount of the total weight of the elastic body, the crack resistance of the sealing body is effective, but the hardness of the elastic body decreases significantly. When the hardness of the elastic body decreases, insufficient rigidity of the elastic body is likely to occur.

[0057] The elastic material may further contain a crosslinking accelerator. 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 stearate N,N'-metaphenyl dimaleic acid.

[0058] The elastic material may contain, in addition to the elastomer, resin vulcanization component, and crosslinking accelerator, carbon and inorganic fillers. The addition of carbon and inorganic fillers makes the elastomer less prone to rupture. Examples of carbon include carbon black, and examples of inorganic fillers include talc, mica, zeolite, silica, kaolin, titania, alumina, and mixtures thereof.

[0059] As inorganic fillers, talc or mica having a flattened shape are preferred. Flattened inorganic fillers are suitable for promoting crosslinking and adjusting the crosslinking density. Furthermore, it is preferable to include zeolite in the elastic body, and more preferably, the zeolite should be included in the elastic body at a concentration of 3 wt% or more relative to the total weight of the elastic body.

[0060] Here, if the resin vulcanizing component is included in an amount of 7 wt% or more relative to the total weight of the elastic body, a crosslinking reaction of the excess resin vulcanizing component occurs within the electrolytic capacitor, stabilizing the radical species of the elastomer and forming a new elastic body. However, during the crosslinking reaction by the excess resin vulcanizing component, gases such as water are generated as byproducts. These gases can create cavities in the elastic body as bubbles. These cavities in the elastic body can become the starting point for cracks that form in the elastic body.

[0061] Zeolites are porous crystals. The pores in zeolites are smaller than the size of gas bubbles, such as water, that are generated as byproducts of crosslinking reactions. Therefore, zeolites selectively retain gases, such as water, generated as byproducts of crosslinking reactions within their pores. In other words, zeolites adsorb gases, such as water, that are generated as byproducts of crosslinking reactions.

[0062] Therefore, zeolite suppresses the formation of cavities within the elastic body due to the crosslinking reaction of excess resin vulcanization components. In other words, zeolite reduces the number of crack initiation points. Consequently, zeolite improves the crack resistance of the sealing body. This effect of zeolite is obtained when the resin vulcanization component is contained at a concentration of 7 wt% or more of the total amount of the elastic body, and the elastomer is contained at a concentration of 27 wt% or more of the total amount of the elastic body, and when zeolite is contained at a concentration of 3 wt% or more of the total weight of the elastic body.

[0063] It is preferable that the zeolite has a greater distribution of pores larger than the size of gas bubbles such as water, which are generated as byproducts of the crosslinking reaction. Since the approximate size of a water molecule is 0.28 nm, the diameter of the pores in the zeolite is preferably between 0.3 nm and 0.5 nm on average, as determined by the pore distribution measured by the gas adsorption measurement method. When the pore diameter of the zeolite is in the range of between 0.3 nm and 0.5 nm on average, the adsorption efficiency of gases such as water is increased, and the crack resistance of the sealing body is particularly improved.

[0064] Furthermore, it is preferable that the carbon and inorganic fillers are included in a total proportion of 40 wt% to 60 wt% of the entire elastic body. If the total content of carbon and inorganic fillers is 40 wt% or more of the entire elastic body, the elastic body can obtain even better strength. Also, if the total content of carbon and inorganic fillers is 60 wt% or less of the entire elastic body, the elastic body can obtain good flexibility and cracking can be suppressed.

[0065] Furthermore, the elastic body may contain one or more of the following: process oil, polyethylene wax, and polybutadiene. Examples of process oils include paraffinic, naphthenic, and aromatic oils. The polyethylene wax may be either low-density polyethylene wax or high-density polyethylene wax.

[0066] When the sealing body includes a rigid substrate, the rigid substrate is a synthetic resin plate, a ceramic plate, or a metal plate. Synthetic resin plates are, for example, made of 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. Metal plates are, for example, made of aluminum, an aluminum alloy containing aluminum or manganese, or stainless steel. The rigid substrate enhances the airtightness within the electrolytic capacitor and protects the elastic body from electrolyte and heat.

[0067] (Anode) In this electrolytic capacitor equipped with a sealing body, the anode, cathode, electrolyte, and separator can be any known material without particular limitation. That is, the anode is a thin plate or foil made of a valve metal. The anode may be formed by stretching a valve metal, or by sintering a powder of a valve metal. Furthermore, the anode may be formed by laminating the same or different types of valve metal powders on the surface of a stretched valve metal by sintering or vapor deposition. Examples of valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. The purity of the valve metal is preferably 99.9% or higher with respect to the anode, and may contain silicon, iron, copper, magnesium, zinc, etc.

[0068] A surface expansion layer is formed on one or both sides of the anode body. The surface expansion layer is an etched layer obtained by etching the foil body, a sintered layer obtained by sintering valve metal powder, or a vapor-deposited layer obtained by depositing valve metal particles onto the foil. In other words, the surface expansion layer has a porous structure and consists of tunnel-shaped pits, sponge-like pits, or densely packed powder or voids between particles.

[0069] Tunnel-shaped etching pits are holes carved in the direction of the foil thickness. These tunnel-shaped etching pits are typically formed by passing a direct current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The tunnel-shaped etching pits are further expanded by passing a direct current through an acidic aqueous solution containing nitric acid, for example. Sponge-like etching pits cause the expanded layer to become a sponge-like layer with a series of fine voids. These sponge-like etching pits are formed by passing an alternating current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid.

[0070] The sintered layer is produced by pasteuring powder of the same or different valve metal as the foil body with a binder and solvent, applying and drying it, and then heating and sintering it in a vacuum or reducing atmosphere. The vapor-deposited layer is produced, for example, by resistance heating vapor deposition or electron beam heating vapor deposition. This vapor-deposited layer is formed by heating the same or different valve metal as the foil body with resistance heat or electron beam energy to evaporate it, and depositing the vapor of valve metal particles onto the surface of the foil body.

[0071] The dielectric film is formed on one or both sides of the anode body on which the expanding layer is formed. When an expanding layer is formed, the dielectric film is formed on the surface of the expanding layer, following the irregularities of the expanding layer. Typically, the dielectric film is an oxide film formed on the surface of the anode body, and if the anode body is made of aluminum, it is an aluminum oxide layer formed by oxidizing the surface of the expanding layer. In the chemical conversion treatment to form the dielectric film, a voltage is applied to the anode body in the conversion solution to achieve a desired withstand voltage. The conversion solution is a halogen-ion-free solution, such as a phosphoric acid-based conversion solution such as ammonium dihydrogen phosphate, a boric acid-based conversion solution such as ammonium borate, or an adipic acid-based conversion solution such as ammonium adipate.

[0072] (Cathode Body) The cathode body is a thin plate or foil made of a valve metal, or a laminate of a metal layer such as a silver layer and a carbon layer. The valve metal is preferably 99% or more of the cathode body and may also contain silicon, iron, copper, magnesium, zinc, etc. The cathode body may be formed in the shape of a plate by laminating a carbon layer on a metal layer and stacked with the anode body with a separator or solid electrolyte layer in between. Alternatively, the carbon layer may be formed by making it into a paste, forming a semiconductor layer on the anode body, coating it onto the solid electrolyte layer, and curing it by heating. The metal layer may be formed by making it into a paste, coating it on top of the carbon layer, and curing it by heating.

[0073] The surface of the cathode body is flattened or enlarged. An oxide film may be intentionally or naturally formed on the surface of the cathode body. Intentionally, a thin oxide film of about 1 to 10 Vfs may be formed by chemical conversion treatment. The naturally occurring oxide film is formed by the reaction of the cathode foil with oxygen in the air.

[0074] (Separator) The separator is made of cellulose and mixed papers such as kraft, Manila hemp, esparto, hemp, cotton, and rayon; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and their derivatives; polytetrafluoroethylene resins; polyvinylidene fluoride resins; vinylon resins; polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides; polyimide resins; polyethylene resins; polypropylene resins; trimethylpentene resins; polyphenylene sulfide resins; acrylic resins; and polyvinyl alcohol resins, and these resins are used individually or in mixtures.

[0075] The separator may be fibrillated by generating thin fibers that branch out from the surface of the original fibers, such as fibrillated cellulose. Fibrillation can be achieved, for example, by beating. The fibrillated fibers intertwine using the thin fibrillated fibers, improving the strength of the separator. As a result, the separator can be made thinner. Increasing the foil thickness of the separator allows for longer anodes and cathodes per unit volume, improving the capacitance of the electrolytic capacitor.

[0076] (Electrolyte) An electrolyte is a mixture obtained by dissolving a solute in a solvent and adding additives as needed. Examples of solvents for electrolytes include protic organic polar solvents or aprotic organic polar solvents, which can be used alone or in combination of two or more. The solute of the electrolyte may contain anionic or cationic components. Typically, the solute is a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid, which can be used alone or in combination of two or more. The acid that becomes an anion and the base that becomes a cationic may be added to the solvent separately.

[0077] Examples of protic organic polar solvents include monohydric alcohols, polyhydric alcohols, and oxyalcohol compounds. Examples of monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol. Examples of polyhydric alcohols and oxyalcohol compounds include ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, and alkylene oxide adducts of polyhydric alcohols such as polyethylene glycol and polyoxyethylene glycerin.

[0078] Examples of aprotic organic polar solvents include sulfones, amides, lactones, cyclic amides, nitriles, and sulfoxides. Examples of sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane. Examples of amides 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 amides include γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate. Examples of nitrile-based compounds include acetonitrile, 3-methoxypropionitrile, and glutaronitrile. Examples of sulfoxide-based compounds include dimethyl sulfoxide.

[0079] Organic acids that act as anionic components as solutes 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, undecanediic acid, dodecanediic acid, tridecanediic acid, t-butyladipic acid, 11-vinyl-8-octadecenediic acid, resorcinic acid, phloroglucic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, and pyromellitic acid, as well as phenols and sulfonic acids.

[0080] In addition, examples of inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Examples of complex compounds of organic and inorganic acids include borogisalicylic acid, borogiolusic acid, borogiglycolic acid, borogimalonic acid, borogisuccinic acid, borogiadipic acid, borogiazelaic acid, borogibenzoic acid, borogimalic acid, borogilacterial acid, borogitartaric acid, borogicitric acid, borogiphthalic acid, borogis(2-hydroxy)isobutyric acid, borogisorcinic acid, borogynaphthoic acid, borogimandelic acid, and borogis(3-hydroxy)propionic acid.

[0081] Furthermore, examples of salts of organic acids, inorganic acids, and composite compounds of organic and inorganic acids include ammonium salts, quaternary ammonium salts, amidinium quaternary salts, amine salts, sodium salts, potassium salts, etc. Examples of quaternary ammonium ions in quaternary ammonium salts include tetramethylammonium, triethylmethylammonium, and tetraethylammonium. Examples of amidinium quaternary salts include ethyldimethylimidazolinium and tetramethylimidazolinium. Examples of amine salts include salts of 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, tributylamine, ethyldimethylamine, and ethyldiisopropylamine.

[0082] Furthermore, other additives can be added to the electrolyte. Examples of additives include alkylene oxide adducts of polyhydric alcohols such as polyethylene glycol and polyoxyethylene glycerin, complex compounds of boric acid and polysaccharides (mannitol, sorbitol, etc.), complex compounds of boric acid and polyhydric alcohols, boric acid esters, nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, m-nitroacetophenone, etc.), and phosphate esters. These may be used individually or in combination of two or more. The amount of additives added is not particularly limited, but it is preferable to add them in an amount that does not degrade the characteristics of the electrolytic capacitor, for example, 60 wt% or less of the electrolyte.

[0083] The electrolyte is injected by immersing the element in the electrolyte, allowing it to penetrate the voids within the element. To ensure the electrolyte penetrates even finer voids, vacuum or pressure treatment may be performed as needed. The electrolyte impregnation process may be repeated multiple times. For example, the inside of the element may be depressurized, and the electrolyte may be injected into the element while simultaneously pressurizing the electrolyte solution.

[0084] (Solid Electrolytes) 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 intramolecular dopants, or conjugated polymers doped with external dopant molecules. Conjugated polymers are obtained by chemical oxidation polymerization or electrolytic oxidation polymerization of monomers or derivatives thereof having π-conjugated double bonds. Dopants or external dopant molecules are acceptors that readily accept electrons into the conjugated polymer, or donors that readily donate electrons, thereby enabling the conductive polymer to exhibit high conductivity.

[0085] Any known conjugated polymer can be used without particular limitation. Examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene. These conjugated polymers may be used individually, in combination of two or more types, or as copolymers of two or more monomers.

[0086] Among the above-mentioned conjugated polymers, conjugated polymers formed by polymerizing thiophene or its derivatives are preferred, and conjugated polymers formed 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 are preferred. As the thiophene derivative, compounds selected from thiophenes having substituents at the 3rd and 4th positions are preferred, 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 number of carbon atoms in the alkyl group or alkoxy group is suitable to be 1 to 16.

[0087] In particular, a polymer of 3,4-ethylenedioxythiophene called EDOT, i.e., poly(3,4-ethylenedioxythiophene) called PEDOT, is preferred. Furthermore, substituents may be added to 3,4-ethylenedioxythiophene. For example, alkylated ethylenedioxythiophene, in which an alkyl group having 1 to 5 carbon atoms is added as a substituent, may be used. Examples of alkylated ethylenedioxythiophene include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydrothieno[3,4-b][1,4]dioxin), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydrothieno[3,4-b][1,4]dioxin), butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydrothieno[3,4-b][1,4]dioxin), and 2-alkyl-3,4-ethylenedioxythiophene.

[0088] Dopants can be any known substance without particular limitation. Dopants may be used alone or in combination of two or more. Polymers or monomers may also be used. Examples of dopants include polyanions, inorganic acids such as boric acid, nitric acid, and phosphoric acid, and organic acids such as acetic acid, oxalic acid, citric acid, tartaric acid, squalaneic 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.

[0089] Polyanions include, for example, substituted or unsubstituted polyalkylenes, substituted or unsubstituted polyalkenes, substituted or unsubstituted polyimides, substituted or unsubstituted polyamides, and substituted or unsubstituted polyesters, which are polymers consisting only of structural units having anionic groups, or polymers consisting of structural units having anionic groups and structural units not having anionic groups. Specifically, examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylate sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylate, and polymaleic acid.

[0090]

[0091] The electrolytic capacitor of the present invention will be described in more detail below based on the following examples. However, the present invention is not limited to the following examples.

[0092] (Examples 1 to 3) Sealing bodies were prepared for Examples 1 to 3 and Comparative Examples 1 and 2. The sealing bodies consisted solely of an elastic material. The elastic material was composed of an elastomer, a resin vulcanizing component, a rubber reinforcing compound, and a processing aid. The composition of the elastic material was the same for Examples 1 to 3 and Comparative Examples 1 and 2. These elastomers, resin vulcanizing components, rubber reinforcing compound, and processing aids were kneaded together, and the sealing bodies were molded while undergoing crosslinking treatment by pressurization and heating. The thickness, surface area, and density of the sealing bodies for Examples 1 to 3 and Comparative Examples 1 and 2 were the same.

[0093] Butyl rubber was used as the elastomer. Alkylphenol formaldehyde resin was used as the resin vulcanization component. Inorganic fillers containing carbon, clay, talc, and mica were used as rubber reinforcing compounders. Stearic acid and the like were used as processing aids. However, the sealing bodies of Examples 1 to 3 and Comparative Examples 1 and 2 have different composition ratios. Table 1 below shows the composition ratios of each sealing body.

[0094] (Table 1)

[0095] As shown in Table 1 above, the resin vulcanizing component accounts for 5, 7, 11, 16, or 20 wt% of the total amount of the elastic body. That is, in the sealing bodies of Examples 1 to 3 and Comparative Example 2, the resin vulcanizing component accounts for 7 wt% or more of the total amount of the elastic body. However, in the sealing body of Comparative Example 2, the resin vulcanizing component is contained in the elastic body at a rate of 20 wt% of the total amount of the elastic body. On the other hand, in the sealing body of Comparative Example 1, the content of the resin vulcanizing component is 5 wt%, which is less than 7 wt% of the total amount of the elastic body. The butyl rubber is at a rate of 27 wt% or more and less than 45 wt% of the total amount of the elastic body.

[0096] (Residual Residue Test of Residual Residue of Resin Vulcanizing Components) The residual resin vulcanizing components contained in the sealing bodies of Comparative Example 1 and Examples 1 to 3 were analyzed. The analysis was performed by pyrolizer gas chromatography-mass spectrometry. First, a control sample was prepared by dissolving 0.1 g of alkylphenol formaldehyde resin having the same basic structure as the resin vulcanizing components contained in the sealing bodies of Comparative Example 1 and Examples 1 to 3 in 2 g of toluene, centrifuging it, and then collecting the supernatant.

[0097] Furthermore, 1 g of the sealing bodies from Comparative Example 1 and Examples 1 to 3 were shredded. This sample was immersed in 3 g of toluene and extracted for 88 hours at a temperature of 80°C. Since the excess resin vulcanization component is not used for crosslinking the elastomer, when the elastomer of the sample swells with toluene, the excess resin vulcanization component is extracted into the toluene. The extract was centrifuged and the supernatant was collected to obtain analytical samples of the sealing bodies from Comparative Example 1 and Examples 1 to 3.

[0098] These control and analytical samples were measured using a pyrolizer gas chromatography-mass spectrometer (MS unit: JEOL JMS-Q1500GC, GC unit: Agilent 7890B). The measurement conditions were as follows: for GC conditions, the column was phenylmethyl-based (slightly polar), the inlet temperature was 300°C, and the oven temperature was 50°C to 320°C; for MS conditions, the ion source temperature was 200°C, the GC-IF temperature was 300°C, and the carrier gas was He.

[0099] Figures 1 to 5 are graphs showing the results of pyrolizer gas chromatography-mass spectrometry. Figure 1 shows the results for the control sample, Figure 2 shows the results for the analytical sample of Comparative Example 1, Figure 3 shows the results for the analytical sample of Example 1, Figure 4 shows the results for the analytical sample of Example 2, and Figure 5 shows the results for the analytical sample of Example 3.

[0100] From the results of the control sample in Figure 1, it was confirmed that the mass-to-charge ratio m / z of the resin vulcanization component, specifically the 191 peak, appeared at a holding time of 14 minutes and 44 seconds. However, it is sufficient to confirm that the peak appears at the same holding time; the actual holding time may differ from 14 minutes and 44 seconds. In Figures 2 to 5, peaks also appear at the same holding time as the control sample, confirming that the resin vulcanization component has been analyzed. From Figures 1 to 5, the ratio of the peak area in Figures 2 to 5 to the peak area in Figure 1 was calculated as a percentage.

[0101] The formula for calculating the peak area was as follows: The measured peak area was multiplied by the sum of the weight of the toluene used and the weight of the sample, and the result was divided by the weight of the sample. The peak area was measured using the peak with the highest intensity.

[0102] The peak ratios calculated from Figures 1 to 5 are shown in Table 2 below.

[0103] (Table 2)

[0104] As shown in Figure 2 and Table 2, the peak ratio in the analysis of the sealing body of Comparative Example 1 is 0.7%. This result indicates that no resin vulcanization components remain in the sealing body of Comparative Example 1. On the other hand, as shown in Figures 3 to 5 and Table 2, the peak ratios in the analysis of the sealing bodies of Examples 1 to 3 range from 3.2% to 7.1%. This result indicates that, unlike Comparative Example 1, excess resin vulcanization components are present in Examples 1 to 3.

[0105] Furthermore, when the resin vulcanizing agent was set to 20 wt%, mixing could not be performed without corrective measures. However, crack resistance improved. When the resin vulcanizing agent was set to 20 wt%, the peak area ratio of excess resin vulcanizing component was 8.8%. From these results, it is preferable that the peak area ratio of excess resin vulcanizing component be between 2.0% and 8.0%.

[0106] Here, the resin vulcanizing component content in Comparative Example 1 was 5 wt% of the total weight of the elastic body, while the resin vulcanizing component content in Examples 1 to 3 was 7 wt% or more of the total weight of the elastic body. This confirmed that if the resin vulcanizing component is included in an amount of 7 wt% or more of the total weight of the elastic body, an excess of the resin vulcanizing component is added beyond the crosslinking-involved resin vulcanizing component that crosslinks the elastomer, resulting in the generation of excess resin vulcanizing component that does not crosslink the elastomer.

[0107] (Crack Resistance Test 1) Electrolytic capacitors using the sealing bodies of Examples 1 to 3 and Comparative Examples 1 and 2 were exposed to a temperature environment of 170°C, and the time at which cracks occurred in the sealing bodies was measured. The occurrence of cracks was confirmed by imaging using an X-ray CT scanner. Cracks occurred in the sealing bodies of Examples 1 to 3 and Comparative Example 1 after 2000 hours had elapsed since exposure to the high-temperature environment.

[0108] Then, using the elapsed time when cracks occurred in the sealing body of Comparative Example 1 as the reference elapsed time, the crack improvement ratio for the sealing bodies of Examples 1 to 3 was calculated. The crack improvement ratio is the ratio obtained by dividing the elapsed time when cracks occurred in the sealing bodies of Comparative Example 1 and Examples 1 to 3 by the reference elapsed time. The respective crack improvement ratios are shown in Table 3 below.

[0109] (Table 3)

[0110] As shown in Table 3 above, Examples 1 to 3, which contained 7 wt% or more of the resin vulcanization component relative to the total amount of the elastic body, showed a crack improvement ratio of 1.4 or more. That is, if the lifespan is defined as the time until crack initiation, the sealing bodies of Examples 1 to 3 had a lifespan 1.4 times or more that of the sealing body of Comparative Example 1. These sealing bodies of Examples 1 to 3 contained excess resin vulcanization components that did not crosslink the elastomer, as confirmed by pyrolizer gas chromatography-mass spectrometry. Thus, it was confirmed that by containing 7 wt% or more of the resin vulcanization component relative to the total amount of the elastic body, the elastic body contains both the crosslinking-involved resin vulcanization component that crosslinks the elastomer and the excess resin vulcanization component that does not crosslink the elastomer, thereby improving crack resistance.

[0111] However, as shown in the "Kneadability" column of Table 3 above, the sealing body of Comparative Example 2, which contained 20 wt% of the resin vulcanizing component relative to the total amount of the elastic body, was difficult to knead during the manufacturing process and could not be produced. Therefore, it was confirmed that the resin vulcanizing component should be contained in the elastic body in proportions of 7 wt% or more and less than 20 wt% relative to the total amount of the elastic body.

[0112] (Examples 4 to 6) Furthermore, sealing bodies of Examples 4 to 6 and Comparative Examples 3 and 4 were prepared. The sealing bodies were composed solely of an elastic material, and the composition of the elastic material in Examples 1 to 3 and Comparative Examples 1 and 2 was the same. In addition, the thickness, surface area, and density of the sealing bodies of Examples 6 and Comparative Examples 3 and 4 were the same as those of the sealing bodies of Examples 1 to 3 and Comparative Examples 1 and 2.

[0113] However, the sealing bodies of Examples to 6 and Comparative Examples 3 and 4 have different composition ratios. In particular, the sealing bodies of Examples to 6 and Comparative Examples 3 and 4 have different butyl rubber content. Table 4 below shows the composition ratios of the sealing bodies of Examples to 6 and Comparative Examples 3 and 4, along with Comparative Example 1 and Example 1.

[0114] (Table 4)

[0115] As shown in Table 4 above, Examples 1, 4 to 6 and Comparative Example 4 differ from Comparative Example 1 in that the resin vulcanization component achieves 7 wt% of the total amount of the elastic material. However, in the sealing body of Comparative Example 4, the butyl rubber deviates from the range of 27 wt% or more and less than 45 wt% of the total amount of the elastic material, and is 45 wt% of the total amount of the elastic material.

[0116] Furthermore, the elastomer was subjected to a process where the elastic material was shredded and washed with toluene to remove excess resin vulcanization components, rubber reinforcing compounding agents, and processing aids. Then, it was measured by differential thermal-thermogravimetric analysis (TG-DTA) at the temperature range in which the elastomer decomposes, and quantified by subtracting the amount of resin vulcanization components obtained by gas chromatography-mass spectrometry from the measured value.

[0117] (Crack Resistance Test 2) The sealing bodies of Examples 4 to 6 and Comparative Examples 3 and 4 were exposed to a temperature environment of 170°C, and the time it took for cracks to occur in the sealing bodies was measured. The occurrence of cracks was confirmed using images obtained with an X-ray CT scanner. The elapsed time when cracks occurred in the sealing body of Comparative Example 1 was used as the reference elapsed time, and the crack improvement ratio of the sealing bodies of Examples 4 to 6 and Comparative Examples 3 and 4 was calculated.

[0118] The crack improvement ratios for each example, along with those for Example 1 and Comparative Example 1, are shown in Table 4 below.

[0119] (Table 5)

[0120] As shown in Table 5 above, the difference between Comparative Example 1 and Comparative Example 3 is the amount of butyl rubber, but in both cases the content of the resin vulcanization component is less than 7 wt% of the total amount of elastic material, so the crack improvement ratio has not improved. On the other hand, in Examples 4 to 6, the content of the resin vulcanization component is 7 wt% of the total amount of elastic material, so the crack improvement ratio is higher than that of Comparative Example 1. However, in Comparative Example 4, the elastomer content was 45 wt% of the total amount of elastic material, so the rigidity of the sealing body was reduced. As a result, swelling of the elastic material occurred in the sealing body of Comparative Example 4.

[0121] Therefore, the elastic body contains 7 wt% or more and less than 20 wt% of resin vulcanizing components relative to the total amount of the elastic body, and contains 27 wt% or more of elastomer relative to the total amount of the elastic body, in addition to the upper limit of the elastomer content being less than 45 wt% relative to the total amount of the elastic body.

[0122] (Examples 7 to 12) Sealing bodies of Examples 7 to 12 were further prepared. The sealing bodies were composed solely of elastic material, and the thickness, surface area, and density of the sealing bodies were the same as those of the sealing bodies of Examples 1 to 6 and Comparative Examples 1 to 4. However, the elastic material of Examples 8 to 12 differs from that of Examples 1 to 5 and Comparative Examples 1 to 4 in that it contains zeolite. The zeolite contained in the elastic material of Examples 8 to 12 has pores with an average size of 0.3 nm. Table 6 below shows the composition of the elastic material of Examples 7 to 12 along with Comparative Example 1.

[0123] (Table 6)

[0124] As shown in Table 6 above, the elastic bodies of Examples 7 to 12 are composed in almost the same composition ratio except for the presence and amount of zeolite. Furthermore, the elastic bodies of Examples 7 to 12 are the same as those of Examples 1 to 5 and Comparative Examples 1 to 4 in that they contain butyl rubber, alkylphenol formaldehyde resin, and carbon, clay, talc, mica, etc., as well as stearic acid, etc. In addition, the elastic bodies of Examples 7 to 12 contain 10 wt% of a resin vulcanizing component in the range of 7 wt% or more and less than 20 wt% of the total amount of the elastic body, and 31 wt% or 32 wt% of an elastomer in the range of 27 wt% or more and less than 45 wt% of the total amount of the elastic body.

[0125] (Crack Resistance Test 3) The sealing bodies of Examples 7 to 12 were exposed to a temperature environment of 170°C, and the time it took for cracks to occur in the sealing bodies was measured. The occurrence of cracks was confirmed using images obtained with an X-ray CT scanner. The time elapsed when cracks occurred in the sealing body of Comparative Example 1 was used as the reference elapsed time, and the crack improvement ratio for the sealing bodies of Examples 7 to 12 was calculated.

[0126] The crack improvement ratios for each method are shown in Table 7 below, along with those for Comparative Example 1.

[0127] (Table 7)

[0128] As shown in Table 7 above, Examples 8 to 12 show a higher crack improvement ratio compared to Example 7. The sealing body of Example 7 does not contain zeolite, whereas the sealing bodies of Examples 8 to 12 contain zeolite at a concentration of 3 wt% or more relative to the total amount of the elastic body. This confirms that when the sealing body contains resin vulcanization components at a concentration of 7 wt% or more and less than 20 wt% relative to the total amount of the elastic body, and elastomers at a concentration of 27 wt% or more and less than 45 wt% relative to the total amount of the elastic body, the crack resistance of the sealing body is further improved by adding zeolite at a concentration of 3 wt% or more relative to the total amount of the elastic body.

[0129] (Examples 13 to 16) Sealing bodies of Examples 13 to 16 were further prepared. The sealing bodies were composed solely of elastic material, and the thickness, surface area, and density of the sealing bodies were the same as those of the sealing bodies of Examples 1 to 12. The butyl rubber content, resin vulcanizing agent content, and rubber reinforcing compound content were the same as those of the sealing body of Example 4. However, the elastic material of Examples 13 to 16 differs from that of Example 4 in that it contains zeolite. Furthermore, the zeolite contained in the elastic material of Examples 13 to 16 has a different pore size. Table 8 below shows the composition of the elastic material and the average pore size of the zeolite for Examples 7 to 12, along with Example 4.

[0130] (Table 8)

[0131] As shown in Table 8 above, the elastic bodies of Example 4 and Examples 13 to 16 are composed in almost the same composition ratio, except for the presence or absence of zeolite. Furthermore, the elastic bodies of Examples 13 to 16 are identical to those of Examples 1 to 12 and Comparative Examples 1 to 4 in that they contain butyl rubber, alkylphenol formaldehyde resin, and carbon, clay, talc, mica, etc., as well as stearic acid, etc. The elastic bodies of Examples 13 to 16 also contain 7 wt% of a resin vulcanizing component, in the range of 7 wt% or more and less than 20 wt% of the total amount of the elastic body, and 27 wt% of an elastomer, in the range of 27 wt% or more and less than 45 wt% of the total amount of the elastic body. However, the zeolite contained in the sealing bodies of Examples 13 to 16 has a different pore size.

[0132] (Crack Resistance Test 4) The sealing bodies of Examples 13 to 16 were exposed to a temperature environment of 170°C, and the time it took for cracks to occur in the sealing bodies was measured. The occurrence of cracks was confirmed using images obtained with an X-ray CT scanner. The time elapsed when cracks occurred in the sealing body of Comparative Example 1 was used as the reference elapsed time, and the crack improvement ratio for the sealing bodies of Examples 13 to 16 was calculated.

[0133] The crack improvement ratios for each example are shown in Table 9 below, along with those for Example 4.

[0134] (Table 9)

[0135] As shown in Table 9 above, Examples 13 to 16 show a higher crack improvement ratio compared to Example 4 when the average pore diameter of the zeolite is 0.3 nm or more. Examples 13 to 16, which include zeolite having an average pore size of 0.3 nm to 0.5 nm in the elastic body, show a higher crack improvement ratio than Example 6.

[0136] This confirmed that when the material contains a resin vulcanizing component in an amount of 7 wt% or more and less than 20 wt% relative to the total amount of the elastic material, and an elastomer in an amount of 27 wt% or more and less than 45 wt% relative to the total amount of the elastic material, the crack resistance of the sealing body is further improved by further including a zeolite having an average pore size of 0.3 nm or more relative to the total amount of the elastic material. Furthermore, it was confirmed that the crack resistance of the sealing body is particularly improved when the average pore size of the zeolite is between 0.3 nm and 0.5 nm.

Claims

1. A sealing body comprising an elastic body for sealing the opening of an outer case housing a capacitor element, wherein the elastic body comprises 7 wt% or more of a resin vulcanizing component and 27 wt% or more of an elastomer relative to the total amount of the elastic body.

2. The sealing body according to claim 1, characterized in that the resin vulcanizing component comprises a crosslinking-involved resin vulcanizing component that crosslinks the elastomer, and an excess resin vulcanizing component that does not crosslink the elastomer.

3. The sealing body according to claim 1, characterized in that the elastic body contains a resin crosslinked elastomer represented by the following chemical structural formula (1). In the formula, n is an integer greater than or equal to 1, m is an integer including 0, and R １ is a methylene group or an ether group, R ２ is an alkyl group 4. The sealing body according to claim 1, characterized in that the elastic body further contains zeolite relative to the total amount of the elastic body.

5. The sealing body according to claim 4, characterized in that the zeolite is contained in an amount of 3 wt% or more relative to the total amount of the elastic body.

6. The sealing body according to claim 4, characterized in that the zeolite has pores of an average of 0.3 nm or more.

7. The sealing body according to claim 1, characterized in that the resin vulcanizing component is a resin having a phenol skeleton, a 2,5-cyclohexanedienone skeleton, or both.

8. The sealing body according to claim 1, characterized in that the elastomer is butyl rubber.

9. An electrolytic capacitor comprising: a sealing body according to any one of claims 1 to 8; an outer case whose opening is sealed by the sealing body; and a capacitor element housed in the outer case, wherein the capacitor element has an anode, a cathode, and an electrolyte.

10. The electrolytic capacitor according to claim 9, characterized in that the electrolyte is an electrolyte solution, a solid electrolyte, or both.

11. A method for manufacturing a sealing body for sealing an opening in an outer case containing a capacitor element, comprising an elastic body forming step of forming an elastic body containing 7 wt% or more of a resin vulcanizing component and 27 wt% or more of an elastomer relative to the total amount of the elastic body.

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