Electrolytic capacitor and method of manufacturing the same

Abstract

To provide an electrolytic capacitor capable of ensuring airtightness under high temperature conditions.SOLUTION: An electrolytic capacitor includes an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealing body that seals an opening of the metal case, and the sealing body includes an elastic member formed from a thermally adhesive composition that contains a polymer component and an inorganic filler, the polymer component contains butyl rubber, the inorganic filler contains calcined clay and zinc oxide, and the content of the calcined clay in the thermally adhesive composition is 140 pts.mass or less per 100 pts.mass of the polymer component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors. [Background technology]

[0002] An electrolytic capacitor includes an electrolytic capacitor element, a case that houses the electrolytic capacitor element, and a sealing member that seals the opening of the case (see Patent Document 1). By sealing the case with the sealing member, the electrolytic capacitor protects the electrolytic capacitor element from the outside air and prevents leakage of the electrolyte. In recent years, in response to the need for smaller electrolytic capacitors, there has been active development of smaller electrolytic capacitors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-274011 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when electrolytic capacitors are miniaturized, the sealing body is also miniaturized, which can reduce the airtightness, particularly in electrolytic capacitors that reach high temperatures during operation. Therefore, there is a need to develop technology that can ensure airtightness even when electrolytic capacitors are miniaturized.

[0005] An object of the present disclosure is to provide an electrolytic capacitor that can ensure airtightness under high temperature conditions. [Means for solving the problem]

[0006] The inventors of the present disclosure have found that the use of a sealing body having an elastic member formed from a thermally adhesive composition containing a polymer component and an inorganic filler can ensure the airtightness of an electrolytic capacitor under high temperature conditions.

[0007] [1] An electrolytic capacitor having an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealing body that seals an opening of the metal case, the sealing body has an elastic member formed of a thermal adhesive composition containing a polymer component and an inorganic filler, the polymer component comprises butyl rubber; the inorganic filler comprises calcined clay and zinc oxide; An electrolytic capacitor, wherein the content of the calcined clay in the thermal adhesive composition is 140 parts by mass or less per 100 parts by mass of the polymer component. [2] the content of the calcined clay in the thermal adhesive composition is 50 parts by mass or more and 130 parts by mass or less per 100 parts by mass of the polymer component, The electrolytic capacitor according to [1], wherein the content of the zinc oxide in the thermal adhesive composition is 0.5 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the polymer component. [3] The electrolytic capacitor according to [1] or [2], wherein the thermal adhesive composition contains carbon black. [4] The electrolytic capacitor according to any one of [1] to [3], wherein the inorganic filler contains talc. . [5] The electrolytic capacitor according to any one of [1] to [4], wherein the electrolyte contained in the electrolytic capacitor element is a solid electrolyte. [6] A method for manufacturing an electrolytic capacitor having an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealing body that has an elastic member and seals an opening of the metal case, comprising: an elastic member preparation step of molding a thermally adhesive composition containing a polymer component and an inorganic filler to prepare the elastic member; a sealing step of placing the electrolytic capacitor element in the metal case and sealing the electrolytic capacitor element in the metal case with the sealing member; Including, the inorganic filler comprises calcined clay and zinc oxide; The method for producing an electrolytic capacitor, wherein the content of the calcined clay in the thermal adhesive composition is 140 parts by mass or less per 100 parts by mass of the polymer component. [7] The method for manufacturing an electrolytic capacitor according to [6], further comprising a heating step of heating the elastic member at a temperature of 80°C or higher and 160°C or lower after the sealing step. [Effects of the Invention]

[0008] According to the present disclosure, an electrolytic capacitor capable of ensuring airtightness under high temperature conditions can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a conceptual diagram illustrating a method for evaluating shear strength in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present disclosure. The following description of the components is an example (typical example) of the embodiments of the present disclosure, and the present disclosure is not limited to these contents as long as it does not exceed the gist of the present disclosure.

[0011] In the present disclosure, the range "X to Y" means "X or more and Y or less." Furthermore, when a numerical range expressed as "X to Y" or "X or more and Y or less" is stated in stages (for example, in order of preference), the upper and lower limits of each numerical range can be combined in any way. In the present disclosure, a description such as "X such as x1, x2, and x3" lists x1, x2, and x3 as examples of X, and does not mean that X is limited to x1, x2, x3, and the like. In the present disclosure, the expression "content of X" means "total content of multiple types of X" when multiple types of X are used in combination, unless otherwise specified.

[0012] 1. Electrolytic capacitors One embodiment of the present disclosure provides an electrolytic capacitor having an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealer that seals the opening of the metal case, wherein the sealer has an elastic member formed from a thermally adhesive composition that includes a polymer component and an inorganic filler. The polymer component includes butyl rubber, and the inorganic filler includes calcined clay and zinc oxide. The content of the calcined clay in the thermally adhesive composition is 140 parts by mass or less per 100 parts by mass of the polymer component.

[0013] In this disclosure, "inorganic fillers" include carbon black, carbon fiber, and Carbon materials such as graphite are not included.

[0014] Conventional electrolytic capacitors have a problem in that the contact area between the sealing body and the outer case decreases as the capacitor is miniaturized, resulting in a decrease in airtightness. This problem is particularly pronounced when the electrolytic capacitor heats up during operation, causing the sealing body to thermally deteriorate and creating a gap between the sealing body and the outer case. This decrease in airtightness of the electrolytic capacitor allows outside air to enter, potentially reducing the characteristics and lifespan of the electrolytic capacitor.

[0015] On the other hand, in the electrolytic capacitor according to this embodiment, the adhesive strength of the elastic member formed from the thermal adhesive composition is increased under high temperature conditions, thereby improving the adhesive strength between the sealing member and the metal case, thereby making it possible to maintain the airtightness and performance of the electrolytic capacitor during operation and thereby achieving a longer life for the electrolytic capacitor.

[0016] The electrolytic capacitor according to this embodiment is not particularly limited as long as it is an electrolytic capacitor element housed in a metal case and sealed with a sealing body. Examples of the electrolytic capacitor include an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, and an electric double layer capacitor, and an aluminum electrolytic capacitor is preferred.

[0017] The electrolytic capacitor according to this embodiment will be described below using an aluminum electrolytic capacitor, which is a typical electrolytic capacitor, as an example, with reference to Fig. 1. However, the electrolytic capacitor according to this embodiment is not limited to that shown in Fig. 1; the aluminum electrolytic capacitor can be replaced with another electrolytic capacitor as appropriate, and the electrolytic capacitor may have components and structures not shown.

[0018] Fig. 1 is a schematic cross-sectional view of an aluminum electrolytic capacitor 10 according to this embodiment. The aluminum electrolytic capacitor 10 shown in Fig. 1 includes an aluminum electrolytic capacitor element 11 having terminals 17, a metal case 13 that houses the aluminum electrolytic capacitor element 11, and a sealing body 15 that seals the opening of the metal case 13. The metal case 13 has horizontal crimped portions 13a and vertical crimped portions 13b, which fix the sealing body 15 and maintain airtightness. The sealing body 15 also has a through hole, and the terminals 17 are led out of the metal case 13 through the through hole of the sealing body 15.

[0019] 1(a), sealing body 15 is a sealing rubber disposed between vertical crimped portion 13b and aluminum electrolytic capacitor element 11, and this sealing rubber corresponds to the elastic member. In FIG. 1(b), sealing body 15 is a rubber-laminated plate having rubber layer 15a and substrate 15b disposed between vertical crimped portion 13b and horizontal crimped portion 13a, and this rubber layer 15a corresponds to the elastic member.

[0020] 1 is sealed with sealing member 15, which prevents outside air from entering aluminum electrolytic capacitor 10 even under high-temperature conditions during operation. This allows aluminum electrolytic capacitor 10 to maintain its characteristics, such as equivalent series resistance (ESR), for a long period of time.

[0021] Such an aluminum electrolytic capacitor 10 is manufactured by inserting aluminum electrolytic capacitor element 11 into a cylindrical metal case 13 with a bottom and an opening, with terminals 17 passing through sealing body 15, fitting sealing body 15 into the opening, and then laterally crimping (drawing) the side of metal case 13 and further vertically crimping (curling) the edge of the opening of metal case 13. More specific manufacturing methods that can be used include those disclosed in Japanese Patent Application Laid-Open Nos. 2004-119907 and 2002-25870, for example.

[0022] In other words, the method for manufacturing an electrolytic capacitor according to this embodiment includes a sealing step of placing an electrolytic capacitor element in a metal case and sealing the electrolytic capacitor element in the metal case with a sealing member having an elastic member. Sealing is preferably performed by the above-described horizontal crimping and vertical crimping. The method for manufacturing an electrolytic capacitor according to this embodiment also includes an elastic member preparation step of preparing an elastic member from a thermally adhesive composition. The elastic member preparation step may be a step of molding the thermally adhesive composition, or a step of crosslinking (vulcanizing) the thermally adhesive composition after molding. Note that crosslinking (vulcanization) may also occur during the molding stage.

[0023] Furthermore, the method for manufacturing the electrolytic capacitor according to this embodiment preferably includes a heating step of heating the elastic member at a temperature of 80°C or higher and 160°C or lower after the sealing step. By applying heat to the elastic member in the heating step, the adhesion between the sealing member and the metal case is improved, thereby further increasing the airtightness of the electrolytic capacitor. The heating time for the elastic member in the heating step is not particularly limited, but is preferably 10 minutes to 12 hours, more preferably 20 minutes to 6 hours, and even more preferably 30 minutes to 3 hours. One aspect of heating in the heating step is aging (re-chemical conversion). The aging treatment is a treatment in which a voltage is applied to the electrolytic capacitor while heating, thereby repairing defects in the dielectric. The voltage applied in the aging treatment is typically 1.0 to 2.0 times the rated voltage of the electrolytic capacitor.

[0024] Thus, in this embodiment, the sealing body uses an elastic member formed from a thermal adhesive composition. Heat generated during operation of the electrolytic capacitor increases the adhesiveness of the elastic member, improving the adhesiveness between the sealing body and the metal case. As a result, the airtightness of the electrolytic capacitor can be improved. Furthermore, an electrolytic capacitor manufactured through a heating process can exhibit higher airtightness due to the improved adhesiveness between the sealing body and the metal case caused by the heat generated during the heating process, coupled with the increased adhesiveness of the elastic member due to the heat generated during operation of the electrolytic capacitor. Furthermore, when the electrolytic capacitor is flow-mounted or reflow-mounted on a substrate, the adhesiveness between the sealing body and the metal case is also improved by the heat generated during mounting. This, combined with the increased adhesiveness of the elastic member due to the heat generated during operation of the electrolytic capacitor, can further improve the airtightness of the electrolytic capacitor.

[0025] 2. Electrolytic capacitor element The electrolytic capacitor element is not particularly limited, and any electrolytic capacitor element can be used, including known electrolytic capacitors and electrolytic capacitors equivalent thereto. The electrolytic capacitor element may be a laminated type or a wound type, but the wound type is preferred. When the electrolytic capacitor element is a wound type, the electrolytic capacitor may be any of a chip type, a lead type, a substrate-supported type, and a screw terminal type, but the chip type is preferred.

[0026] In this embodiment, the electrolyte contained in the electrolytic capacitor element is preferably a solid electrolyte. Examples of the solid electrolyte include conductive polymers and ion-conductive solids, and preferably conductive polymers. Examples of the conductive polymer include poly(3,4-ethylenedioxythio) (PEDOT) doped with a toluenesulfonic acid-based dopant such as p-toluenesulfonic acid and polystyrenesulfonic acid (PSS).

[0027] Because solid electrolytes are susceptible to oxidation degradation under heated conditions, electrolytic capacitors using solid electrolytes as electrolytes may experience significant performance degradation when oxygen-containing ambient air penetrates the interior, and degradation may become even more severe during operation at high temperatures. As described above, the electrolytic capacitor according to this embodiment can maintain its airtightness even during operation under high-temperature conditions, making the solid electrolyte less susceptible to degradation during operation and allowing properties such as equivalent series resistance (ESR) to be maintained for a long period of time. Therefore, in this embodiment, a solid electrolyte can be suitably used as the electrolyte contained in the electrolytic capacitor element.

[0028] 3. Sealing body The sealing member is a member that is fitted into the opening of the metal case and seals the metal case to ensure airtightness of the electrolytic capacitor. In this embodiment, the sealing member has an elastic member formed of a thermal adhesive composition.

[0029] In this disclosure, "thermal tackiness" refers to the property of increasing tackiness when placed under high-temperature conditions (e.g., temperature conditions during operation of an electrolytic capacitor, temperature conditions during a heating process, temperature conditions during reflow mounting of an electrolytic capacitor, etc.) compared to before being placed under high-temperature conditions. The rate of change in shear strength before and after heating can be used as an indicator of "thermal tackiness." Heating increases shear strength, and when the rate of change in shear strength before and after heating is equal to or greater than a certain value, preferably equal to or greater than the value described below, the material can be considered to have "thermal tackiness." The larger the positive rate of change in shear strength before and after heating, the higher the thermal tackiness. The temperature conditions during operation of an electrolytic capacitor are typically in the range of 80°C to 160°C.

[0030] In the present disclosure, the term "thermally adhesive composition" is not particularly limited as long as it is a composition having the above-described thermal adhesive properties, but is preferably a composition in which the rate of change in shear strength before and after heating, calculated by formula (1) (hereinafter also simply referred to as "rate of change in shear strength"), is at least a certain level. Specifically, the rate of change in shear strength of the thermally adhesive composition is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, even more preferably 20% or more, particularly preferably 30% or more, especially preferably 50% or more, and most preferably 60% or more. The upper limit of the rate of change in shear strength of the thermally adhesive composition is not particularly limited, but is preferably 120% or less, more preferably 110% or less, even more preferably 100% or less, even more preferably 90% or less, and particularly preferably 85% or less. That is, preferred ranges for the rate of change in shear strength of the thermally adhesive composition include, for example, 5% or more and 120% or less, 10% or more and 120% or less, 15% or more and 120% or less, 20% or more and 110% or less, 30% or more and 100% or less, 50% or more and 90% or less, and 60% or more and 85% or less.

[0031] By setting the rate of change in shear strength of the thermal adhesive composition within the above range, the heat resistance of the electrolytic capacitor can be improved, and therefore a highly reliable electrolytic capacitor can be provided that can maintain properties such as equivalent series resistance (ESR) for a long period of time.

[0032]

number

[0033] In formula (1), the shear strength after heating is the shear strength measured by using a sample prepared by heating a test piece formed from the thermal adhesive composition at 125°C for 1000 hours, releasing the heat, and then press-bonding the test piece to an aluminum plate at a pressure of 0.44 MPa, and pulling the test piece and the aluminum plate in the shear direction at a pulling rate of 50 mm / min. A more detailed method for measuring the shear strength after heating is as described in the Examples below.

[0034] In formula (1), the shear strength is the shear strength measured by using a sample prepared by pressing a test piece formed from the thermal adhesive composition onto an aluminum plate at a pressure of 0.44 MPa, and pulling the test piece and the aluminum plate in the shear direction at a pulling rate of 50 mm / min. The test piece used to prepare the sample is different from the sample used to measure shear strength after heating, and is a test piece that has not been heat-treated at 125°C for 1000 hours. A more detailed method for measuring shear strength is described below. , as will be shown in the examples below.

[0035] The test piece formed of the thermal adhesive composition used for preparing the sample for measuring the shear strength after heating and the shear strength is prepared as follows. First, the thermal adhesive composition is crosslinked (vulcanized) for 3 to 5 hours under heating conditions of 180 to 200°C to form a sheet with a thickness of 2.0 mm, and this sheet is punched into a dumbbell shape to prepare a dumbbell No. 4 test piece. Next, this dumbbell No. 4 test piece is cut in half at the parallel part of the dumbbell shape to obtain a test piece for the sample.

[0036] The inventors of the present disclosure speculate that the shear strength of the thermo-adhesive composition increases when placed under high temperature conditions because bonds within and / or between polymer components are broken, resulting in lower molecular weights, and the surface of the thermo-adhesive composition softens and changes to a clay-like state that is partially sticky. Here, it is believed that when an appropriate amount of inorganic filler, particularly calcined clay, is contained in the thermal adhesive composition, the formation of bonds between polymer components is moderately hindered, creating a state in which the polymer components are likely to be depolymerized under high-temperature conditions. Also, when an appropriate amount of inorganic filler, particularly calcined clay, is contained in the thermal adhesive composition, a sufficient amount of polymer components can be present, making the effect of depolymerization more likely to be apparent, and increasing the shear strength under high-temperature conditions. From the above, it is presumed that the elastic member of the sealing member of this embodiment exhibits a high anchoring effect by softening the thermally adhesive composition on the surface of the member to a clay-like state under high-temperature conditions and penetrating into the fine irregularities on the surface of the metal case. In other words, the thermally adhesive composition softened to a clay-like state on the surface of the elastic member acts as an adhesive that bonds the metal case and the sealing member. As a result, it is believed that the airtightness of the electrolytic capacitor can be ensured under high-temperature conditions even when the contact area between the sealing member having such an elastic member and the metal case is small. The portion of the thermally adhesive composition that softens to a clay-like state when placed under high-temperature conditions is preferably formed on the surface of the elastic member. That is, under the temperature conditions during operation of the electrolytic capacitor according to this embodiment, the surface portion of the elastic member that is in contact with the metal case (for example, in the electrolytic capacitor shown in FIG. 1, the side portion of sealing body 15 that is in contact with lateral crimping portion 13a of metal case 13) is preferably softened to a clay-like state, and this clay-softened portion is preferably fixed to the metal case.

[0037] It is desirable that the thermal adhesive composition maintains its airtightness not only under high temperature conditions but also at the temperature during storage after production. Therefore, it is desirable that the thermal adhesive composition exhibits sufficient shear strength even under non-high temperature conditions, for example, under room temperature conditions of 35°C or less. Specifically, the shear strength of the thermal adhesive composition is preferably 1.0 N / cm 2 More preferably 2.0N / cm 2 More preferably, 3.2N / cm 2 More preferably, 4.0 N / cm or more 2 More preferably, 4.4 N / cm or more 2 More preferably, 4.8 N / cm 2 The upper limit of the shear strength of the thermoadhesive composition is preferably 10 N / cm 2 Less than or equal to 9.0 N / cm 2 or less, more preferably 8.0 N / cm 2 or less, and even more preferably 7.0 N / cm 2 Below 6.0 N / cm, particularly preferably 2Below 5.5 N / cm, particularly preferably 2 That is, the preferred range of the shear strength of the thermal adhesive composition is, for example, 1.0 N / cm 2 More than 10N / cm 2 Below, 2.0N / cm 2 More than 10N / cm 2 Below, 3.2N / cm 2 More than 9.0N / cm 2 Below, 3.2N / cm 2 More than 8.0N / cm 2 Below, 4.0N / cm 2 More than 7.0N / cm 2 Below, 4.4N / cm 2 More than 6.0N / cm 2 or less, and 4.8N / cm 2 More than 5.5N / cm 2 The following ranges are included:

[0038] The shear strength of the thermal adhesive composition, the shear strength after heating, and the rate of change in shear strength are described below. The temperature can be controlled by adjusting the contents of calcined clay and zinc oxide in the thermo-adhesive composition so as to achieve a desired temperature.

[0039] The thermo-adhesive composition includes a polymer component and an inorganic filler.

[0040] The polymer component includes butyl rubber. Butyl rubber is an isobutylene-isoprene copolymer obtained by cationic polymerization of isobutylene and a small amount of isoprene. In this disclosure, the term "rubber" is used to refer to not only uncrosslinked rubber but also crosslinked rubber. In other words, "butyl rubber" refers to uncrosslinked butyl rubber and / or crosslinked butyl rubber. However, the butyl rubber is preferably uncrosslinked butyl rubber.

[0041] In addition to butyl rubber, the polymer component may contain one or more other resins, such as halogenated butyl rubbers (e.g., chlorinated butyl rubber and brominated butyl rubber), isoprene rubber, ethylene propylene rubber, and chlorosulfonated polyethylene rubber.

[0042] The content of the polymer component in the thermal-adhesive composition is not particularly limited, but from the viewpoint of the heat resistance of the electrolytic capacitor, it is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 33% by mass or more, even more preferably 35% by mass or more, particularly preferably 39% by mass or more, and particularly preferably 45% by mass or more, and from the viewpoint of the heat resistance and airtightness of the electrolytic capacitor, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. That is, preferred ranges of the content of the polymer component in the thermal-adhesive composition include, for example, 25% by mass or more and 60% by mass or less, 30% by mass or more and 60% by mass or less, 33% by mass or more and 55% by mass or less, 35% by mass or more and 55% by mass or less, 39% by mass or more and 50% by mass or less, and 45% by mass or more and 50% by mass or less.

[0043] The content of butyl rubber in the thermal-adhesive composition is not particularly limited, but from the viewpoint of the heat resistance of the electrolytic capacitor, it is preferably 30% by mass or more, more preferably 33% by mass or more, even more preferably 35% by mass or more, still more preferably 39% by mass or more, and particularly preferably 45% by mass or more, and from the viewpoint of the heat resistance and airtightness of the electrolytic capacitor, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. That is, preferred ranges of the content of butyl rubber in the thermal-adhesive composition include, for example, 30% by mass or more and 60% by mass or less, 33% by mass or more and 60% by mass or less, 35% by mass or more and 55% by mass or less, 39% by mass or more and 55% by mass or less, and 45% by mass or more and 50% by mass or less.

[0044] The content of butyl rubber in the polymer component is not particularly limited, but in order to fully exhibit the heat resistance and gas barrier properties of the butyl rubber, it is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and is usually 100% by mass or less.

[0045] The thermal adhesive composition may contain a crosslinking agent, and from the viewpoint of heat resistance, it preferably contains a crosslinking agent for butyl rubber. In the present disclosure, the term "crosslinking agent" is intended to include a crosslinking accelerator. Furthermore, "vulcanization" is sometimes referred to as "crosslinking," and vice versa.

[0046] The cross-linking agent for butyl rubber is not particularly limited and can be appropriately selected from any cross-linking agent, but is preferably a resin having a cross-linking group. Specific examples of the cross-linking agent for butyl rubber include alkylphenol formaldehyde resins, heat-reactive phenol resins, and bisphenol resins, and the like, with alkylphenol formaldehyde resins being preferred. do.

[0047] The content of the crosslinking agent for butyl rubber in the thermal-adhesive composition is not particularly limited, but is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and preferably 20 parts by mass or less, relative to 100 parts by mass of butyl rubber. That is, preferred ranges for the content of the crosslinking agent for butyl rubber in the thermal-adhesive composition include, for example, ranges of 5 parts by mass or more and 20 parts by mass or less, 10 parts by mass or more and 20 parts by mass or less, and 15 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of butyl rubber.

[0048] The thermo-adhesive composition contains calcined clay and zinc oxide (ZnO) as inorganic fillers.

[0049] The content of the inorganic filler in the thermal-adhesive composition is not particularly limited, but from the viewpoint of increasing the strength of the thermal-adhesive composition, it is preferably 25 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, particularly preferably 70 parts by mass or more, especially preferably 80 parts by mass or more, and is preferably 170 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 135 parts by mass or less, even more preferably 120 parts by mass or less, especially preferably 85 parts by mass or less, relative to 100 parts by mass of the polymer component. That is, preferred ranges for the content of the inorganic filler in the thermal-adhesive composition include, for example, 25 parts by mass or more to 170 parts by mass or less, 40 parts by mass or more to 170 parts by mass or less, 50 parts by mass or more to 150 parts by mass or less, 50 parts by mass or more to 85 parts by mass or less, 60 parts by mass or more to 150 parts by mass or less, 50 parts by mass or more to 135 parts by mass or less, 70 parts by mass or more to 135 parts by mass or less, and 80 parts by mass or more to 120 parts by mass or less.

[0050] Calcined clay is clay that has been calcined at high temperatures. Calcined clay has had the structural water removed from the crystals, rendering the clay surface hydrophobic. This allows for good dispersibility when kneaded with non-polar butyl rubber, increasing the strength of the elastic member. Calcined clay also has low surface activity, which inhibits reaction with oxygen in the air, and is therefore expected to improve stability against heat aging. Furthermore, the use of calcined clay can improve the thermal adhesiveness of the thermal adhesive composition compared to when uncalcined clay is used.

[0051] The clay before high-temperature calcination is not particularly limited as long as it is composed mainly of aluminum silicate, and examples thereof include kaolin, montmorillonite, pyrophyllite, halloysite, and sericite, with kaolin being preferred. That is, the calcined clay is not particularly limited as long as it is a calcined product of clay composed mainly of aluminum silicate, but calcined kaolin is preferred. The calcined clay may be used alone or in any combination and ratio of two or more types.

[0052] The calcination temperature when calcining clay to produce calcined clay is not particularly limited as long as it is possible to remove structural water in the crystals and make the clay surface hydrophobic, but is preferably 500°C or higher and 700°C or lower.

[0053] The average particle size of the calcined clay is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 0.8 μm or more, even more preferably 1 μm or more, particularly preferably more than 4 μm, and is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. That is, preferred ranges for the average particle size of the calcined clay include, for example, 0.1 μm or more and 50 μm or less, 0.5 μm or more and 40 μm or less, 0.8 μm or more and 30 μm or less, 1 μm or more and 20 μm or less, and more than 4 μm and 10 μm or less.

[0054] In the present disclosure, the term "average particle size" refers to the median diameter (D 50 )

[0055] The content of the calcined clay in the thermally adhesive composition is not particularly limited, but is preferably at least 25 parts by mass, more preferably at least 40 parts by mass, even more preferably at least 50 parts by mass, even more preferably at least 60 parts by mass, particularly preferably at least 70 parts by mass, and especially preferably at least 80 parts by mass, relative to 100 parts by mass of the polymer component, and is usually at most 140 parts by mass, preferably at most 130 parts by mass, and more preferably at most 100 parts by mass. That is, preferred ranges for the content of the calcined clay in the thermally adhesive composition include, for example, from 25 to 140 parts by mass, from 40 to 140 parts by mass, from 50 to 140 parts by mass, from 50 to 130 parts by mass, from 50 to 130 parts by mass, from 60 to 130 parts by mass, from 70 to 100 parts by mass, and from 80 to 100 parts by mass.

[0056] By setting the content of calcined clay in the thermal-adhesive composition to the above-mentioned lower limit or more, the rate of change in shear strength of the thermal-adhesive composition can be easily adjusted to the above-mentioned range. That is, by setting the content of calcined clay in the thermal-adhesive composition to the above-mentioned lower limit or more, the thermal adhesiveness of the thermal-adhesive composition under high-temperature conditions can be increased, thereby improving and maintaining the airtightness of the electrolytic capacitor under high-temperature conditions, such as during operation. Furthermore, by setting the content of calcined clay in the thermal-adhesive composition to the above-mentioned upper limit or less, the shear strength of the thermal-adhesive composition can be increased, and for example, the airtightness of the electrolytic capacitor during storage under non-high-temperature conditions (e.g., room temperature conditions) can be improved and maintained.

[0057] Alternatively, the content of the calcined clay in the thermally adhesive composition may be 10 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more, or 150 parts by mass or less, 130 parts by mass or less, less than 70 parts by mass, 65 parts by mass or less, or 60 parts by mass or less, relative to 100 parts by mass of the polymer component. That is, the content of the calcined clay in the thermally adhesive composition may be, for example, in the range of 10 parts by mass or more to 150 parts by mass or less, 20 parts by mass or more to 130 parts by mass or less, 25 parts by mass or more to 130 parts by mass or less, 30 parts by mass or more to less than 70 parts by mass, 40 parts by mass or more to 65 parts by mass or less, 50 parts by mass or more to 60 parts by mass or less, or 50 parts by mass or more to 150 parts by mass, relative to 100 parts by mass of the polymer component.

[0058] The content of calcined clay in the inorganic filler is not particularly limited, but from the viewpoint of the airtightness of the electrolytic capacitor, it is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and is usually less than 100% by mass, preferably 99% by mass or less, and more preferably 98% by mass or less.

[0059] The content of zinc oxide in the thermally adhesive composition is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more (1.0 part by mass or more), even more preferably 2 parts by mass or more (2.0 parts by mass or more), particularly preferably 3 parts by mass or more (3.0 parts by mass or more), and is preferably 20 parts by mass or less (20.0 parts by mass or less), more preferably 15 parts by mass or less (15.0 parts by mass or less), even more preferably 10 parts by mass or less (10.0 parts by mass or less), even more preferably 8 parts by mass or less (8.0 parts by mass or less), particularly preferably 5 parts by mass or less (5.0 parts by mass or less), relative to 100 parts by mass of the polymer component. That is, the preferred range of the content of zinc oxide in the thermal adhesive composition is, for example, 0.1 parts by mass or more and 20 parts by mass or less (0.1 parts by mass or more and 20.0 parts by mass or less), 0.5 parts by mass or more and 20 parts by mass or less (0.5 parts by mass or more and 20.0 parts by mass or less), 0.5 parts by mass or more and 5 parts by mass or less (0.5 parts by mass or more and 5.0 parts by mass or less), relative to 100 parts by mass of the polymer component. and 3.0 parts by mass or more and 8 parts by mass or less (3.0 parts by mass or more and 8.0 parts by mass or less).

[0060] By setting the zinc oxide content in the thermal-adhesive composition within the above range, the shear strength, shear strength after heating, and shear strength change rate of the thermal-adhesive composition can be increased. Furthermore, under high-temperature conditions, the polymer components in the thermal-adhesive composition are depolymerized, resulting in a clay-like softened state on the surface of the elastic member. By setting the zinc oxide content in the thermal-adhesive composition within the above range, this state can be maintained for a long period of time. Furthermore, by setting the zinc oxide content in the thermal-adhesive composition to the above upper limit or less, the aggregation of zinc oxide can be suppressed. That is, by setting the zinc oxide content in the thermal-adhesive composition within the above range, the thermal adhesiveness of the thermal-adhesive composition can be enhanced regardless of temperature conditions, thereby improving and maintaining the airtightness of the electrolytic capacitor under both temperature conditions during storage and operation. Furthermore, by setting the zinc oxide content in the thermal-adhesive composition within the above range, the strength of the elastic member can be increased.

[0061] In this embodiment, by setting the content of calcined clay in the thermal-adhesive composition and the content of zinc oxide in the thermal-adhesive composition within the above-mentioned preferred ranges, the shear strength, shear strength after heating, and rate of change of shear strength of the thermal-adhesive composition are more likely to be improved, thereby making it possible to further improve the airtightness of the electrolytic capacitor.

[0062] The inorganic filler may contain one or more other inorganic fillers in addition to calcined clay and zinc oxide. Examples of other inorganic fillers include, but are not limited to, silica, alumina, kaolin, talc, rock wool, glass powder, glass flakes, glass beads, glass fiber, silicon carbide, silicon nitride, aluminum nitride, zinc oxide, titanium dioxide, calcium carbonate, calcium sulfate, barium carbonate, magnesium carbonate, magnesium sulfate, barium sulfate, cellulose, aramid, and wood, with talc being preferred.

[0063] When the inorganic filler contains talc, the content of talc in the inorganic filler is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less. That is, when the inorganic filler contains talc, preferred ranges for the content of talc in the inorganic filler include, for example, 1% by mass or more and 50% by mass or less, 5% by mass or more and 10% by mass or more and 10% by mass or more and 20% by mass or less.

[0064] The thermoadhesive composition may further contain a carbon material, such as carbon black, carbon fiber, and graphite, with carbon black being preferred.

[0065] When the thermal-adhesive composition contains a carbon material, the content of the carbon material (preferably carbon black) in the thermal-adhesive composition is not particularly limited, but in order to increase the strength of the thermal-adhesive composition, it is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the polymer component. That is, preferred ranges for the content of the carbon material in the thermal-adhesive composition include, for example, 20 parts by mass or more and 70 parts by mass or less, 30 parts by mass or more and 60 parts by mass or less, and 40 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the polymer component.

[0066] The thermoadhesive composition may contain other components in addition to those described above, as long as the effects of the present disclosure are not impaired. Examples of other components include processing aids such as stearic acid; coupling agents; Examples of other components include, but are not limited to, modifiers such as additives, antioxidants, and dispersing aids. The other components may be used singly or in any combination and ratio of two or more.

[0067] When the thermally adhesive composition contains other components, the content of the other components in the thermally adhesive composition is not particularly limited as long as it does not impair the effects of the present disclosure, and may be, for example, 10% by mass or less, 5% by mass or less, or 2% by mass or less.

[0068] The sealing member may be an elastic member itself, or may be a combination of an elastic member and another member. For example, in the aluminum electrolytic capacitor shown in FIG. 1(a), sealing member 15 is an elastic member disposed between vertical crimping portion 13b and aluminum electrolytic capacitor element 11 to seal metal case 13. Also, in the aluminum electrolytic capacitor shown in FIG. 1(b), sealing member 15 is an elastic member disposed between vertical crimping portion 13b and horizontal crimping portion 13a, and is a rubber-laminated plate having a rubber layer and a substrate. Preferred examples of the substrate laminated with the rubber layer include hard substrates such as metal substrates, resin substrates, and ceramic substrates. Metal substrates include metal substrates such as aluminum, aluminum alloy, and stainless steel. Synthetic resin substrates include resin substrates such as Bakelite (phenolic resin), polypropylene, epoxy resin, fluororesin, acrylic resin, and silicone resin.

[0069] 4. Metal case The metal case is an outer case for an electrolytic capacitor, and is not particularly limited as long as it can accommodate an electrolytic capacitor element and can be subjected to vertical and horizontal crimping processes. It is usually a cylindrical metal case with a bottom. Examples of materials for the metal case include aluminum, aluminum alloys, copper, copper alloys such as brass, iron, and stainless steel. Since the thermal adhesive composition of this embodiment has particularly high thermal adhesiveness to aluminum, the material for the metal case is preferably aluminum. [Example]

[0070] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to the description of the following examples as long as it does not depart from the gist of the disclosure.

[0071] Example 1 (Making of sealing body) A thermal adhesive composition was obtained by kneading 100 parts by weight of butyl rubber, 50 parts by weight of carbon black, 25 parts by weight of calcined kaolin (average particle size 3.2 μm), 1 part by weight of zinc oxide, 16 parts by weight of alkylphenol formaldehyde resin, and other additives (stearic acid, silane coupling agent, and antioxidant). This thermal adhesive composition was molded and crosslinked at 190°C ± 10°C for about 4 hours to obtain a sealant with a thickness of about 1.5 mm.

[0072] (Fabrication of aluminum electrolytic capacitor elements) An electrolytic capacitor element, in which an anode foil and a cathode foil were wound with a separator interposed therebetween, was immersed in a solid electrolyte forming solution and then heated to obtain an aluminum electrolytic capacitor element. The anode foil was aluminum foil with an oxide film on its surface, and the cathode foil was aluminum foil. The solid electrolyte-forming solution contained 3,4-ethylenedioxythiophene and an oxidizing agent such as p-toluenesulfonic acid, and the 3,4-ethylenedioxythiophene in the solution was polymerized by heating. The resulting aluminum electrolytic capacitor contained poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonic acid as the solid electrolyte.

[0073] (Making aluminum electrolytic capacitors) The lead terminals of the aluminum electrolytic capacitor element were passed through a sealing member, and the aluminum electrolytic capacitor element was then inserted into an aluminum case, with the sealing member then fitted into the opening of the aluminum case. In this state, the aluminum case was crimped vertically and horizontally to seal the aluminum electrolytic capacitor element inside the aluminum case. The sealing member was then heated at a temperature of 105°C or higher for 30 minutes or more while a voltage of 25 V was applied, resulting in the aluminum electrolytic capacitor shown in Figure 1(a).

[0074] [Examples 2 to 9, Comparative Examples 1 to 3] A thermally adhesive composition was obtained in the same manner as in Example 1, except that the amounts of calcined kaolin and zinc oxide used were changed as shown in Table 1 or Table 2. The obtained thermally adhesive composition was molded in the same manner as in Example 1 to obtain a sealant with a thickness of approximately 1.5 mm. Furthermore, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 using the obtained sealant.

[0075] Example 10 A thermally adhesive composition was obtained in the same manner as in Example 1, except that the amount of calcined kaolin used was changed as shown in Table 1 and that the amount of talc used was changed as shown in Table 1. The obtained thermally adhesive composition was molded in the same manner as in Example 1 to obtain a sealant with a thickness of approximately 1.5 mm. Furthermore, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 using the obtained sealant.

[0076] Comparative Example 4 A thermally adhesive composition was obtained in the same manner as in Example 4, except that hydrous kaolin was used instead of calcined kaolin. The obtained thermally adhesive composition was molded in the same manner as in Example 1 to obtain a sealant with a thickness of approximately 1.5 mm. Furthermore, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 using the obtained sealant.

[0077] [Measurement of shear strength] The thermally adhesive compositions obtained in the examples and comparative examples were crosslinked at 190°C ± 10°C for approximately 4 hours to obtain a sheet having a thickness of 2.0 mm. This sheet was punched into a dumbbell shape to prepare a dumbbell-shaped No. 4 test piece 22 as shown in Figure 2(a). Next, as shown in Figure 2(a), this dumbbell-shaped No. 4 test piece 22 was cut in half (cut at the center of the parallel portion 22a of the dumbbell shape) to prepare a test piece 21.

[0078] Tape 29 was attached to both sides of the obtained test piece 21. At this time, the tape 29 was attached to the portion other than the end of the test piece 21 so that the end (2.1 cm × 1.5 cm) of the test piece 21 was not covered by the tape 29. As shown in FIG. 2(b), the end of the test piece 21 was placed on a first aluminum plate 23 (length × width × thickness: 67 mm × 25 mm × 2 mm), and a second aluminum plate 27 was placed on the end of the test piece 21 with a release film 25 interposed therebetween. A load of 14 kg was applied to the second aluminum plate 27, thereby pressing the end of the test piece 21 to the first aluminum plate 23 with a pressure of 0.44 MPa. Thereafter, the release film 25 and the second aluminum plate 27 were removed from the test piece 21 to prepare an evaluation sample. The release film 25 is a film for preventing adhesion between the test piece 21 and the second aluminum plate 27.

[0079] 2(c), the test piece 21 of the evaluation sample 20 and the first aluminum plate 23 were pulled in the shear direction at a pulling speed of 50 mm / min to measure the shear strength. At this time, the tape 29 was pulled while the first aluminum plate 23 was fixed.

[0080] [Measurement of shear strength after heating] Prior to preparing the evaluation sample, the test piece was heated at 125°C for 1000 hours, and then cooled to room temperature (25°C). The shear strength was measured in the same manner as in "Evaluation of shear strength," except that the test piece was cooled to room temperature (25°C).

[0081] [Evaluation of airtightness of aluminum electrolytic capacitors under high temperature conditions] The airtightness of aluminum electrolytic capacitors under high temperature conditions was evaluated by measuring the equivalent series resistance (ESR) of the aluminum electrolytic capacitor before and after the heat resistance test and determining the rate of change in ESR before and after the heat resistance test. The specific evaluation method is as follows: However, in Comparative Example 1, the test piece did not adhere to the first aluminum plate in the shear strength measurement after heating, which clearly indicated that the airtightness of the aluminum electrolytic capacitor could not be ensured, and therefore evaluation was not performed. In Comparative Example 2, the shear strength measurement showed that the shear strength was significantly reduced by heating, which clearly indicated that the airtightness of the aluminum electrolytic capacitor could not be ensured, and therefore evaluation was not performed. In Comparative Example 3, zinc oxide aggregates were generated in the test piece, which likely indicated that the airtightness of the aluminum electrolytic capacitor could not be ensured, and therefore evaluation was not performed.

[0082] First, the ESR of the aluminum electrolytic capacitors was measured using the following method before the heat resistance test. Next, as a heat resistance test, the aluminum electrolytic capacitors were heated at a temperature of 125°C for 4000 hours. After this heat resistance test, the ESR of the aluminum electrolytic capacitors was measured using the following method. The ESR change rate was calculated from the ESR of the aluminum electrolytic capacitor before and after the heat resistance test according to the following formula (I), and the airtightness of the aluminum electrolytic capacitor under high temperature conditions was evaluated based on the following evaluation criteria. The results are shown in Tables 1 and 2.

[0083] (ESR measurement method) The ESR was measured at a temperature of 20°C and a frequency of 100 kHz using an LCR meter (Agilent Technologies, Inc., "E4980A Precision LCR Meter").

[0084] ESR change rate (%) = {(ESR after heat resistance test - ESR before heat resistance test) / (ESR before heat resistance test)} × 100 Formula (I)

[0085] (Evaluation criteria) A: The ESR change rate is less than 50%. B: The ESR change rate is 50% or more and less than 100%. C: The ESR change rate is 100% or more and 150% or less. D: The ESR change rate is more than 150%.

[0086] [Table 1]

[0087] [Table 2] [Explanation of symbols]

[0088] 10 Aluminum electrolytic capacitors 11 Aluminum electrolytic capacitor elements 13 Metal case 13a Horizontal crimping part 13b Vertical crimping part 15 Sealing body 15a Rubber layer 15b board 17 terminals 20 Evaluation samples 21 Test specimen 22 Dumbbell-shaped No. 4 test piece 22a Parallel part 23 First aluminum plate 25 Release film 27 Second aluminum plate 29 Tape

Claims

1. An electrolytic capacitor having an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealing body that seals an opening of the metal case, the sealing body has an elastic member formed of a thermal adhesive composition containing a polymer component and an inorganic filler, the polymer component comprises butyl rubber; the inorganic filler comprises calcined clay and zinc oxide; The electrolytic capacitor, wherein the content of the calcined clay in the thermal adhesive composition is 140 parts by mass or less per 100 parts by mass of the polymer component.

2. the content of the calcined clay in the thermal adhesive composition is 50 parts by mass or more and 130 parts by mass or less per 100 parts by mass of the polymer component, 2. The electrolytic capacitor according to claim 1, wherein the content of the zinc oxide in the thermal adhesive composition is 0.5 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the polymer component.

3. 10. The electrolytic capacitor of claim 1, wherein the thermally tacky composition comprises carbon black.

4. 10. The electrolytic capacitor of claim 1, wherein the inorganic filler comprises talc.

5. 2. The electrolytic capacitor according to claim 1, wherein the electrolyte contained in the electrolytic capacitor element is a solid electrolyte.

6. A method for manufacturing an electrolytic capacitor having an electrolytic capacitor element, a metal case that houses the electrolytic capacitor element, and a sealing body that has an elastic member and seals an opening of the metal case, comprising: an elastic member preparation step of molding a thermally adhesive composition containing a polymer component and an inorganic filler to prepare the elastic member; a sealing step of placing the electrolytic capacitor element in the metal case and sealing the electrolytic capacitor element in the metal case with the sealing member; Including, the inorganic filler comprises calcined clay and zinc oxide; The method for producing an electrolytic capacitor, wherein the content of the calcined clay in the thermal adhesive composition is 140 parts by mass or less per 100 parts by mass of the polymer component.

7. The method for manufacturing an electrolytic capacitor according to claim 6, further comprising, after the sealing step, a heating step of heating the elastic member at a temperature of 80°C or higher and 160°C or lower.

Images