Sealing body and electric double layer capacitor

Abstract

To provide a sealing body having a low moisture permeation rate but a suppressed degree of decrease in gas permeation rate, and an electric double layer capacitor provided with the sealing body.SOLUTION: A sealing body includes an elastomeric member containing an elastomer. The elastomeric member contains one or more selected from the group of process oil, polyethylene wax, and polybutadiene, and talc. An electric double layer capacitor is constructed by housing a capacitor element having an electric double layer in a case and sealing the case with the sealing body.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing body for sealing a case in which a capacitor element having an electric double layer is accommodated, and an electric double layer capacitor including this sealing body.

Background Art

[0002] An electric double layer capacitor is configured by filling an electrolyte between a pair of polarizable electrodes. This electric double layer capacitor utilizes the charge storage action of the electric double layer formed at the interface between the polarizable electrode and the electrolyte. That is, at the positive electrode, anions in the electrolyte align at the interface with the polarizable electrode and form pairs with the pores in the polarizable electrode at an extremely short distance. Thereby, a potential barrier is formed at the positive electrode. Also at the negative electrode, cations in the electrolyte align at the interface with the polarizable electrode and form pairs with the electrons in the polarizable electrode at an extremely short distance, and a potential barrier is formed at the negative electrode.

[0003]

[0004] In this electric double layer capacitor, in order to suppress the evaporation of the electrolytic solution formed by adding an electrolyte, a capacitor element configured by filling an electrolyte between a pair of polarizable electrodes is sealed with a case and a sealing body (see, for example, Patent Document 1). The sealing body is a member that seals the opening of a bottomed cylindrical case that houses the capacitor element. This sealing body is provided with an elastomer member such as butyl rubber, for example. A solution has also been proposed to eliminate problems with the sealing performance of the sealing body in a high-temperature and high-humidity environment by blending a petroleum-based or paraffin-based softening agent and clay, which is a white filler, into the elastomer member.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As an electrolyte for an electric double layer capacitor, a non-aqueous system using an organic solvent such as γ-butyrolactone and propylene carbonate is known. If the non-aqueous electrolyte contains moisture, it may cause inconvenience to the electric double layer capacitor. Specifically, when a voltage load test is performed on an electric double layer capacitor using an electrolyte containing moisture under high temperature conditions around 70 °C, a chemical reaction occurs on the activated carbon, which is the main material of the polarized electrode of the electric double layer capacitor.

[0007] The chemical reaction on the activated carbon destroys the structure of the activated carbon and moves the fine particles of the activated carbon into the electrolyte, which may also cause an increase in leakage current and short circuit. In addition, since the structure of the activated carbon is destroyed, the electrical resistance of the polarized electrode itself increases, which also causes an increase in the internal resistance of the entire electric double layer capacitor. Therefore, the sealing body is required to have low permeability that does not allow moisture to pass through, prevents or suppresses the intrusion of moisture from the outside of the electric double layer capacitor, and makes it difficult for moisture to penetrate into the inside of the electric double layer capacitor.

[0008] However, it is impossible to completely control the amount of moisture intrusion into the electric double layer capacitor to zero. Even an electrolyte containing only a few tens of ppm or less of moisture causes a chemical reaction on the activated carbon. And the chemical reaction on the activated carbon ultimately leads to the generation of gases such as carbon monoxide inside the electric double layer capacitor.

[0009] Therefore, if the sealing body is required to have too low gas permeability, the gas cannot be sufficiently released to the outside, and the gas accumulates in the electric double layer capacitor, and the accumulated gas increases the internal pressure of the electric double layer capacitor. Then, there is a risk of causing liquid leakage from the electric double layer capacitor due to the operation of the relief valve, or rupturing the electric double layer capacitor. Therefore, there is a need for a sealing body that reduces the amount of water passing through and suppresses the amount of water entering the electric double layer capacitor, while suppressing the degree of decrease in the gas permeability.

[0010] The present invention has been proposed to solve the above problems, and its object is to provide a sealing body in which the amount of water passing through is low, but the degree of decrease in the gas permeability is suppressed, and an electric double layer capacitor including this sealing body.

Means for Solving the Problems

[0011] In order to solve the above problems, the sealing body of the present invention is a sealing body that seals the case of an electric double layer capacitor, and includes an elastomer member containing an elastomer, and the elastomer member contains at least one selected from the group consisting of process oil, polyethylene wax, and polybutadiene, and talc.

[0012] The combination of at least one selected from the group consisting of process oil, polyethylene wax, and polybutadiene and talc can suppress a small decrease in gas permeability while reducing the water permeability, and can make the ratio of the gas permeability to the water permeability exceed 1. For example, the amount of water passing through can be 10 [mg×mm / cm 2 or less, and the ratio of the gas permeability to the water permeability can exceed 1.

[0013] The elastomer member may further contain mica. By containing mica, the decrease in gas permeability can be further suppressed, the water permeability can be further reduced, and the ratio of the gas permeability to the water permeability greatly exceeds 1.

[0014] The elastomer member contains the process oil, and the process oil may be contained in the elastomer member at a ratio of 5 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the elastomer.

[0015] The white filler containing the talc may be contained in the elastomer member at a ratio of 150 parts by weight or more and 420 parts by weight or less with respect to 100 parts by weight of the elastomer.

[0016] The elastomer member contains the process oil and the polyethylene wax, and the white filler containing the talc may be contained in the elastomer member at a ratio of 250 parts by weight or more and 420 parts by weight or less with respect to 100 parts by weight of the elastomer. Compared with the case where none of the process oil, polyethylene wax, polybutadiene, and talc is added, the gas permeability increases, the water permeability decreases, and a balance between the gas permeability and the water permeability can be achieved at a high level.

[0017] The elastomer member may further contain clay.

[0018] An electric double layer capacitor including this sealing body, a case sealed by the sealing body, and a capacitor element having an electric double layer accommodated in the case is also an aspect of the present invention.

[0019] In this electric double layer capacitor, a non-aqueous electrolyte impregnated in the capacitor element may be provided.

Advantages of the Invention

[0020] According to the present invention, in the sealing body, the water permeation amount is low, but the degree of decrease in the gas permeation amount can be suppressed.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, a sealing body and an electric double layer capacitor according to embodiments of the present invention will be described. Note that the present invention is not limited to the embodiments described below.

[0022] (Overview of Electric Double Layer Capacitor) An electric double layer capacitor is a passive element that stores and discharges electric charges based on capacitance. The capacitor element of an electric double layer capacitor includes a positive electrode foil, a negative electrode foil, a separator, and an electrolytic solution, and adopts a wound or laminated form. The positive electrode foil and the negative electrode foil face each other with a separator in between. The electrolytic solution is filled in the voids of the capacitor element. However, as long as it can hold the electrolyte, the medium does not have to be a liquid, and it may be a solid polymer or a gel electrolyte.

[0023] This capacitor element has an electric double layer. That is, an electrode active material layer is formed on the positive electrode foil and the negative electrode foil, and an electric double layer is formed at the interface between at least one of the polarizable electrodes of the positive electrode foil or the negative electrode foil and the electrolytic solution. In addition to capacitors having polarizable electrodes on both the positive electrode foil and the negative electrode foil, hybrid capacitors are also called electric double layer capacitors. A hybrid capacitor has a polarizable electrode on the positive electrode foil and an electrode active material layer composed of metal compound particles capable of occluding and releasing lithium ions or a Faraday reaction electrode of a carbon material on the negative electrode foil.

[0024] The capacitor element is housed in a case of the electric double layer capacitor and sealed with a sealing body. The case is a bottomed cylindrical shape for housing the capacitor element and is made of, for example, aluminum. The sealing body is attached to the opening of the case by caulking to seal the opening of the case. Lead-out terminals are connected to the positive electrode foil and the negative electrode foil. An external terminal for leading to the outside is attached to the sealing body. The lead-out terminals connected to the positive electrode foil and the negative electrode foil and the external terminal of the sealing body are electrically connected, whereby the electric double layer capacitor can be mounted on a circuit. Alternatively, the lead-out terminals connected to the positive electrode foil and the negative electrode foil are led out to the outside through through-holes in the sealing body.

[0025] (Sealing Body) This sealing body is provided with an elastomer member having an elastic force in order to improve the adhesion to the case by caulking and to ensure insulation. The elastomer member mainly contains an elastomer. Examples of the elastomer include isobutylene isoprene rubber also called butyl rubber, ethylene propylene diene rubber also called EPDM, styrene butadiene rubber, isoprene rubber, fluororubber, acrylic rubber, and natural rubber. The elastomer member is produced by vulcanization such as resin vulcanization, peroxide vulcanization, sulfur vulcanization, quinoid vulcanization, and polyol vulcanization, and also includes thermoplastic elastomers. One or more kinds of elastomers may be used.

[0026] Furthermore, one or more of process oil, polyethylene wax, and polybutadiene are added to this elastomer member. Examples of the process oil include paraffinic, naphthenic, and aromatic types. The polyethylene wax may be either low-density polyethylene wax or high-density polyethylene wax. Also, talc is added to the elastomer member. A white filler other than talc may be added to the elastomer member in addition to talc. Examples of the white filler other than talc include mica and clay. For example, talc alone, talc and clay, or talc, mica, and clay may be added to the elastomer member.

[0027] Here, an elastomer member containing process oil, polyethylene wax, or polybutadiene easily permeates gas and moisture. On the other hand, an elastomer member containing talc has an effect opposite to that of process oil, polyethylene wax, or polybutadiene and hardly permeates gas and moisture. Moreover, although clay etc. are cited as white fillers that hardly permeate moisture and gas in addition to talc, talc, compared with clay, reduces the amount of moisture passing through while extremely reducing the gas permeability.

[0028] However, when one or more selected from the group consisting of process oil, polyethylene wax, and polybutadiene are combined with talc, the effect of the low gas permeability of talc is canceled or reduced, the gas permeability does not extremely decrease, the water permeability can be reduced, and the ratio of the gas permeability to the water permeability can be made greater than 1. When only clay is selected, both the low gas permeability and the low water permeability of the clay are canceled, and the water passage amount also increases.

[0029] The added species among process oil, polyethylene wax, and polybutadiene are preferably added at a ratio of 5 parts by weight or more and 50 parts by weight or less per 100 parts by weight of the total elastomer for each type. For example, when process oil is added, the process oil is added at a ratio of 5 parts by weight or more and 50 parts by weight or less per 100 parts by weight of the total elastomer.

[0030] Also, the total of talc and white fillers other than talc contained in the elastomer member is preferably added at a ratio of 150 parts by weight or more and 420 parts by weight or less per 100 parts by weight of the total elastomer. Talc is preferably added at a ratio of 10 parts by weight or more and 160 parts by weight or less per 100 parts by weight of the total elastomer. When clay is added, it is preferably added at a ratio of 20 parts by weight or more and 220 parts by weight or less per 100 parts by weight of the total elastomer. When mica is added, it is preferably added at a ratio of more than 0 parts by weight and 80 parts by weight or less.

[0031] In particular, it is preferable that the elastomer member contains both process oil and polyethylene wax, and a white filler containing talc is added in a proportion of 150 parts by weight or more and 420 parts by weight or less with respect to 100 parts by weight of the total elastomer. With this type of combination and addition amount range, compared with a sealing body provided with an elastomer member in which neither process oil, polyethylene wax, polybutadiene nor talc is added, the moisture permeation amount is reduced, while not only suppressing a decrease in gas permeation amount, but also improving the gas permeation amount, and the ratio of the gas permeation amount to the moisture permeation amount also becomes much higher than 1.

[0032] The elastomer member may further contain other additives. For example, the elastomer member can contain carbon black and the like. Further, this sealing body may be provided by laminating a hard resin plate on the elastomer member or enclosing the hard resin plate with the elastomer member. The hard resin plate further enhances the sealing property inside the electric double layer capacitor.

[0033] Such a sealing body is produced by mixing an elastomer, a vulcanizing agent, and one or more selected from the group consisting of process oil, polyethylene wax, and polybutadiene, and talc or a white filler other than talc and other additives. Examples of the vulcanizing agent include benzoyl peroxide, dicumyl peroxide, 2,5 - dimethyl - 2,5 - bis(t - butylperoxy)hexane, alkylphenol formaldehyde resins, etc., and these may be mixed in an amount of 0.5 to 20 parts by weight with respect to 100 parts by weight of the total elastomer.

[0034] (Capacitor element) (Electrode foil) By fitting such a sealing body into the opening of a case containing a capacitor element, an electric double layer capacitor is fabricated. The positive electrode foil and negative electrode foil of the capacitor element are formed by forming an electrode active material layer, which serves as a polarized electrode, on a current collector. As the current collector, metals having a valve action such as aluminum foil, platinum, gold, nickel, titanium, steel, and carbon can be used. The shape of the current collector can adopt any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape. Further, the surface of the current collector may form an uneven surface by etching treatment or the like, or may be a plane surface. Furthermore, surface treatment may be performed to attach phosphorus to the surface of the current collector.

[0035] The electrode active material layer serving as a polarized electrode contains a carbon material. The carbon material is activated carbon, carbon black such as ketjen black, acetylene black, and channel black, carbon nanohorn, amorphous carbon, natural graphite, artificial graphite, graphitized ketjen black, mesoporous carbon, carbon nanotube, carbon nanofiber, etc., which are made from natural plant tissues such as coconut husk, synthetic resins such as phenol, and fossil fuels such as coal, coke, and pitch. The specific surface area of this carbon material may be improved by activation treatment such as steam activation, alkali activation, zinc chloride activation, or electric field activation, as well as opening treatment.

[0036] The carbon material is mixed with a conductive aid and a binder and applied to the current collector by a doctor blade method or the like. The mixture of the carbon material, the conductive aid, and the binder may be formed into a sheet shape and crimped to the current collector. Examples of the binder include rubbers such as fluorine-based rubber, diene-based rubber, and styrene-based rubber, fluorine-containing polymers such as polytetrafluoroethylene and polyvinylidene fluoride, celluloses such as carboxymethyl cellulose and nitrocellulose, and other polyolefin resins, polyimide resins, acrylic resins, nitrile resins, polyester resins, phenol resins, polyvinyl acetate resins, polyvinyl alcohol resins, and epoxy resins. These binders may be used alone or in combination of two or more.

[0037] As the conductive aid, Ketjen black, acetylene black, natural / artificial graphite, fibrous carbon, etc. can be used, and examples of the fibrous carbon include fibrous carbons such as carbon nanotubes and carbon nanofibers (hereinafter referred to as CNF). The carbon nanotubes may be single-walled carbon nanotubes (SWCNT) in which the graphene sheet is a single layer, multi-walled carbon nanotubes (MWCNT) in which two or more graphene sheets are coaxial and rolled up to form a multi-layer tube wall, or a mixture thereof.

[0038] (Electrolyte solution) The electrolyte solution is composed of a non-aqueous solvent. Examples of the non-aqueous solvent include lactone compounds such as γ-butyrolactone or γ-valerolactone, and carbonate compounds such as propylene carbonate or ethylene carbonate. As the solvent, other types of solvents can be mixed and used in addition to lactone compounds and carbonate compounds. Examples of the other types of solvents include cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, chain esters, nitrile compounds, amide compounds, and sulfone compounds such as sulfolane.

[0039] Examples of the solute of the electrolyte solution include quaternary ammonium salts. Examples of the quaternary ammonium salts include tetramethylammonium, ethyltrimethylammonium, tetraethylammonium, triethylmethylammonium, diethyldimethylammonium, methylethylpyrrolidinium, spirobipyrrolidinium, etc. as the cation, and BF 4 - , PF 6 - , ClO 4 - , AsF 6 - , SbF 6 - , AlCl 4 - , or RfSO 3 - , (RfSO 2 ) 2 N- , RfCO 2 - (Rf is a fluoroalkyl group having 1 to 8 carbon atoms) and the like can be mentioned.

[0040] Typically, as the quaternary ammonium salt, tetramethylammonium BF 4 , ethyltrimethylammonium BF 4 , diethyldimethylammonium BF 4 , triethylmethylammonium BF 4 , tetraethylammonium BF 4 , spirobipyrrolidinium BF 4 , methylethylpyrrolidinium BF 4 , tetramethylammonium PF 6 , ethyltrimethylammonium PF 6 , diethyldimethylammonium PF 6 , triethylmethylammonium PF 6 , tetraethylammonium PF 6 , spirobipyrrolidinium PF 6 , methylethylpyrrolidinium PF 6、 tetramethylammonium bis(oxalato)borate, ethyltrimethylammonium bis(oxalato)borate, diethyldimethylammonium bis(oxalato)borate, triethylmethylammonium bis(oxalato)borate, tetraethylammonium bis(oxalato)borate, spirobipyrrolidinium bis(oxalato)borate, methylethylpyrrolidinium bis(oxalato)borate, tetramethylammonium difluorooxalatoborate, ethyltrimethylammonium difluorooxalatoborate, diethyldimethylammonium difluorooxalatoborate, triethylmethylammonium difluorooxalatoborate, tetraethylammonium difluorooxalatoborate, spirobipyrrolidinium difluorooxalatoborate, methylethylpyrrolidinium difluorooxalatoborate and the like can be used.

[0041] In addition, examples of the additive include phosphoric acids and their derivatives (phosphoric acid, phosphorous acid, phosphate esters, phosphonic acids, etc.), boric acids and their derivatives (boric acid, boric anhydride, borate esters, complexes of boron with compounds having a hydroxyl group and / or a carboxyl group, etc.), nitrates (lithium nitrate, etc.), nitro compounds (nitrobenzoic acid, nitrophenol, nitrophenetole, nitroacetophenone, aromatic nitro compounds, etc.).

[0042] (Separator) The separator prevents contact between the positive electrode foil and the negative electrode foil. Examples of the separator include cellulose such as kraft, manila hemp, esparto, hemp, rayon, and mixed papers thereof, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and their derivatives, polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins, polyamide-based resins such as aliphatic polyamide, semi-aromatic polyamide, and wholly aromatic polyamide, polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, etc. These resins can be used alone or in combination.

Examples

[0043] Hereinafter, the sealing body and the electric double layer capacitor of the present invention will be described in more detail based on examples. It should be noted that the present invention is not limited to the following examples.

[0044] (Examples 1 to 3) Seals of Examples 1 to 3 and Comparative Examples 1 to 5 were produced. Each seal has only an elastomeric member. The elastomeric member was formed by mixing a butyl rubber polymer produced by vulcanization using alkylphenol formaldehyde resins, a paraffinic process oil, talc, and clay. The addition amount of the process oil and the total addition amount of the white fillers including talc and clay are as shown in Table 1 below. The thickness and surface area of the seals of Examples 1 to 3 and Comparative Examples 1 to 5 were made the same. In Table 1, the addition amounts are weight ratios when the addition amount of the butyl rubber polymer is 100 parts by weight.

[0045] (Table 1) TIFF0007683244000001.tif76164

[0046] (Gas Permeation Measurement) The seals of Examples 1 to 3 and Comparative Examples 1 to 5 were used to seal the openings of aluminum cases of the same shape and the same thickness containing 5 ml of γ-butyrolactone. The initial weight of the case sealed with the seal was measured, and the case was left in a temperature environment of 85°C for 500 hours, and the weight after leaving was measured. Then, the gas permeation amount after leaving was calculated by the following formula (1). (Formula (1)) Gas permeation amount [mg×mm / cm 2 = (Initial weight - Weight after leaving) × Seal thickness / Seal surface area

[0047] (Water Permeation Measurement) The seals of Examples 1 to 3 and Comparative Examples 1 to 5 were used to seal the openings of aluminum cases of the same shape and the same thickness containing 4 g of molecular sieve. The initial weight of the case sealed with the seal was measured, and the case was left in a temperature environment of 85°C and a humidity of 85% for 500 hours, and the weight after leaving was measured. Then, the water permeation amount after leaving was calculated by the following formula (2). (Formula (2)) Water permeation amount [mg×mm / cm 2 = (Weight after leaving - Initial weight) × Seal thickness / Seal surface area

[0048] Using the calculated gas permeation rate and water permeation rate, the ratio of the gas permeation rate to the water permeation rate was calculated. The gas permeation rates, water permeation rates, and the ratios of the gas permeation rates to the water permeation rates for Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 2 below.

[0049] (Table 2) TIFF0007683244000002.tif121164

[0050] As shown in Table 2, in Comparative Example 5 where only clay instead of talc was contained in the elastomer member and no process oil was added, the low-permeability property of the clay strongly affected. As a result, the water permeation rate of Comparative Example 5 decreased compared to Comparative Example 1, but the gas permeation rate of Comparative Example 5 also decreased compared to Comparative Example 1, and the degree of decrease in the gas permeation rate exceeded the degree of decrease in the water permeation rate. That is, the ratio of the gas permeation rate to the water permeation rate fell below 1.

[0051] Also, in Comparative Example 2 where only talc was contained in the elastomer member and no process oil was added, the low-permeability property of the talc strongly affected. As a result, the water permeation rate of Comparative Example 2 decreased compared to Comparative Example 1, but the gas permeation rate of Comparative Example 2 decreased significantly, far exceeding the degree of decrease in the water permeation rate. That is, the ratio of the gas permeation rate to the water permeation rate fell far below 1.

[0052] Also, in Comparative Example 3 where only process oil was contained in the elastomer member and no talc was added, the high-permeability property of the process oil strongly affected. As a result, the gas permeation rate of Comparative Example 3 improved more than that of Comparative Example 1, but the water permeation rate of Comparative Example 3 also exceeded that of Comparative Example 1.

[0053] It was thus confirmed that process oil and white filler have opposite effects on permeability. Further, when comparing only the results of Comparative Example 2 and Comparative Example 5, it was confirmed that clay is better than talc in terms of the ratio of gas permeation amount to water permeation amount. In other words, it was confirmed that talc has a stronger effect of reducing gas permeation amount than the effect of reducing water permeation amount, and it is difficult to achieve a balance between water permeation amount and gas permeation amount with talc alone compared to clay alone.

[0054] Therefore, in Comparative Example 4, while clay was selected, process oil and clay, which have opposite properties in terms of permeability, were mixed in the elastomer member. As a result, in Comparative Example 4, although the gas permeation amount increased, the water permeation amount also increased significantly compared to Comparative Example 1.

[0055] However, it was confirmed that in Examples 1 to 3 in which talc and process oil, which disrupt the balance between water permeation amount and gas permeation amount, were mixed in the elastomer member, the water permeation amount decreased compared to Comparative Example 1, and the ratio of gas permeation amount to water permeation amount also exceeded 1. That is, in Examples 1 to 3 in which process oil and talc were mixed, it was confirmed that the water permeation amount was decreased while suppressing the degree of decrease in gas permeation amount.

[0056] (Examples 4 - 5) Sealing bodies of Examples 4 and 5 were produced. The sealing body of Example 4 was produced with the same composition, same configuration, same manufacturing method, and same conditions as Example 3, except that polyethylene wax was contained in the elastomer member instead of process oil, including the addition amount of the elastomer and the type and addition amount of the white filler. The sealing body of Example 5 was produced with the same composition, same configuration, same manufacturing method, and same conditions as Example 3, except that polybutadiene was contained in the elastomer member instead of process oil, including the addition amount of the elastomer and the type and addition amount of the white filler.

[0057] Each sealing body has only an elastomer member. The elastomer member is formed by mixing process oil, talc, and clay using a butyl rubber polymer as the elastomer. The addition amounts of the process oil in Examples 4 and 5 and each comparative example, and the total addition amount of the white filler combining talc and clay are as shown in Table 3 below. In Table 3, the addition amount is the weight ratio when the addition amount of the butyl rubber polymer is 100 parts by weight.

[0058] (Table 3) TIFF0007683244000003.tif106146

[0059] (Measurement) The gas permeation amount and water permeation amount of the sealing bodies in Examples 4 and 5 and each comparative example were measured. The measurement conditions are the same as those in Examples 1 to 3. The measurement results are shown in Table 4 below.

[0060] (Table 4) TIFF0007683244000004.tif151149

[0061] As shown in Examples 4 and 5 of Table 4, even if it is a combination of polyethylene wax and talc, or a combination of polybutadiene and talc instead of the combination of process oil and talc, it was confirmed that the water permeation amount decreased compared to Comparative Example 1, and the ratio of the gas permeation amount to the water permeation amount also exceeded 1. That is, it was confirmed that by including at least one selected from the group consisting of process oil, polyethylene wax, and polybutadiene and talc in the elastomer member, the degree of decrease in the gas permeation amount was suppressed while the water permeation amount was decreased.

[0062] (Examples 6 to 11) Sealing bodies of Examples 6 to 11 were produced. The sealing bodies of Examples 6 to 11 were prepared by selecting and combining one or more types from the group of process oil, polyethylene wax, and polybutadiene, and further adding mica to talc and clay except for Example 7. The compositions and addition amounts of the sealing bodies of specific Examples 6 to 11 are as shown in Table 5 below. In Table 5, the addition amount is the weight ratio when the addition amount of the butyl rubber polymer is 100 parts by weight. Except for the points described in Table 5, Examples 6 to 11 were produced under the same configuration, same manufacturing method, and same conditions as Example 1.

[0063] (Table 5) TIFF0007683244000005.tif106128

[0064] (Measurement) The gas permeation amount and moisture permeation amount of the sealing bodies of Examples 6 to 11 were measured. The measurement conditions are the same as those of Examples 1 to 3. The measurement results are shown in Table 6 below together with Comparative Example 1.

[0065] (Table 6) TIFF0007683244000006.tif151152

[0066] As shown in Examples 7 to 11 of Table 6, even if two or more types are selected from the group of process oil, polyethylene wax, and polybutadiene and are included in the elastomer member together with talc, it was confirmed that the degree of decrease in the gas permeation amount was suppressed while the moisture permeation amount was decreased. Further, as shown in Examples 6, 8 to 11, even if mica was further contained in the elastomer member, it was confirmed that the degree of decrease in the gas permeation amount was suppressed while the moisture permeation amount was decreased.

[0067] Furthermore, Examples 9 to 11 can be confirmed to have a higher gas permeation rate, a suppressed water permeation rate, and a ratio of gas permeation rate to water permeation rate far exceeding 1, compared to Comparative Example 1. That is, by including both process oil and polyethylene wax in the elastomer member and including a white filler containing talc in the elastomer member at a ratio of 250 parts by weight or more and 450 parts by weight or less with respect to 100 parts by weight of the elastomer, it was confirmed that the gas permeation rate increases, the water permeation rate is suppressed, and the ratio of the gas permeation rate to the water permeation rate far exceeds 1.

Claims

1. A sealing body for sealing a case of an electric double layer capacitor, comprising an elastomer member containing an elastomer, wherein the elastomer member contains one or more selected from the group consisting of process oil, polyethylene wax, and polybutadiene, and talc, the water permeation amount is 10 [mg×mm / cm²] or less, and the ratio of the gas permeation amount to the water permeation amount exceeds 1, characterized by the above sealing body.

2. The elastomer member further contains mica, characterized by the sealing body according to Claim 1.

3. The elastomer member contains the process oil, wherein the process oil is contained in the elastomer member at a ratio of 5 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the elastomer, characterized by the sealing body according to Claim 1 or 2.

4. The white filler containing talc is contained in the elastomer member at a ratio of 150 parts by weight or more and 420 parts by weight or less with respect to 100 parts by weight of the elastomer, characterized by the sealing body according to any one of Claims 1 to 3.

5. The elastomer member contains the process oil and the polyethylene wax, wherein the white filler containing talc is contained in the elastomer member at a ratio of 250 parts by weight or more and 420 parts by weight or less with respect to 100 parts by weight of the elastomer, characterized by the sealing body according to any one of Claims 1 to 3.

6. The elastomer member further contains clay, characterized by the sealing body according to any one of Claims 1 to 5.

7. The sealing body according to any one of Claims 1 to 6, a case sealed by the sealing body, and a capacitor element having an electric double layer and housed in the case, characterized by comprising the above. characterized by the electric double layer capacitor.

8. comprising a non-aqueous electrolyte impregnated in the capacitor element, characterized by the electric double layer capacitor according to Claim 7.

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