Capacitor capable of being used for immersion cooling and method for manufacturing the same

Abstract

The purpose of the present invention is to provide a capacitor which can be used for immersion cooling with high reliability and long life by reducing the incidence of unexpected deterioration, and to provide a method of manufacturing the same.　The present invention provides a capacitor 3000 that can be used for immersion cooling, said capacitor 3000 comprising a capacitor element 1400, an electrolyte, a case 1300 for accommodating the capacitor element 1400 and the electrolyte, and a sealing body 1000 for sealing the opening portion of the case, wherein the sealing body 1000 comprises: an inside elastic member that is positioned inside the case 1300, at least some of the inside elastic member contacting the electrolyte; and an outside elastic member, at least some of which being exposed through the case. The sealing body 1000 has a structure lamainted using mutually different elastic members, the inside elastic member is at least one rubber species selected from the group consisting of butyl rubber and ethylene propylene rubber, and the outside elastic member has a Hansen solubility parameter distance form a hydrocarbon refrigerant of at least 8.0.

Description

Capacitor that can be used for immersion cooling and manufacturing method thereof

[0001] The present invention relates to a capacitor that can be used for immersion cooling and a method for manufacturing the same.

[0002] In recent years, as server systems have become more powerful, they have been equipped with denser and smaller electronic components to perform high-speed, advanced continuous processing. This has resulted in an increasing tendency for the amount of heat generated by circuit boards containing electronic components to increase, and there is an increasing number of applications and situations where immersion cooling is required to provide more powerful cooling than air or water cooling.

[0003] Japanese Patent Application Laid-Open No. 2022-169554

[0004] When a circuit board on which electronic components such as capacitors are mounted is cooled by immersion cooling, the capacitor is also immersed in the cooling medium. In this case, the exterior side of the sealing member that hermetically seals the opening of the aluminum case (exterior housing) of the capacitor is also naturally in contact with the cooling medium. There is a concern that the rubber material of the sealing member that comes into contact with the immersion cooling medium will swell over time and will no longer be able to maintain its airtightness.

[0005] On the other hand, the inside of the rubber seal is in constant contact with an electrolyte, typically an electrolytic solution. However, because the properties and behavior of the cooling refrigerant and the electrolyte differ significantly, there is no known single rubber material that can ensure reliable resistance to both.

[0006] More specifically, for example, butyl rubber and ethylene propylene diene rubber (EPDM), which are commonly used as sealing materials for aluminum electrolytic capacitors, tend to swell easily in hydrocarbon refrigerants, which raises concerns about the deterioration of capacitor characteristics.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a capacitor that can be used for highly reliable, long-life immersion cooling by reducing the occurrence of unexpected deterioration in immersion cooling applications, and a method for manufacturing the same.

[0008] The capacitor of the present invention that can be used for immersion cooling is a capacitor that is immersion cooled with a hydrocarbon-based refrigerant, and includes a capacitor element, an electrolyte, a case that accommodates the capacitor element and the electrolyte, and a sealing body that seals an opening of the case, wherein the sealing body includes an inner elastic member that is disposed inside the case and at least a portion of which contacts the electrolyte, and an outer elastic member that is at least a portion of which is exposed from the case, and has a structure in which different elastic members are laminated, wherein the inner elastic member is at least one type selected from the group consisting of butyl rubber and ethylene propylene rubber, and the outer elastic member has a Hansen solubility parameter distance with the hydrocarbon-based refrigerant of 8.0 or more.

[0009] Furthermore, the present invention provides a method for manufacturing a capacitor usable for immersion cooling, the capacitor being subjected to immersion cooling using a hydrocarbon-based refrigerant and comprising a capacitor element, an electrolyte, a case accommodating the capacitor element and the electrolyte, and a sealing body sealing an opening of the case, the method comprising the steps of: laminating an inner elastic member and an outer elastic member and simultaneously molding them under temperature and pressure to vulcanize and bond them together; sealing the opening of the case accommodating the capacitor element and the electrolyte with the molded sealing body; and laterally crimping at least a portion of the inner elastic member and at least a portion of the outer elastic member from the outside of the case, wherein at least a surface of the inner elastic member that comes into contact with the electrolyte is made of one or more rubbers selected from the group consisting of butyl rubber and ethylene propylene rubber; and at least a surface of the outer elastic member that comes into contact with the hydrocarbon-based refrigerant has a Hansen solubility parameter distance with the hydrocarbon-based refrigerant of 8.0 or greater.

[0010] It is possible to provide a capacitor that can be used for highly reliable, long-life immersion cooling with reduced occurrence of unexpected deterioration, and a method for manufacturing the same.

[0011]

[0023] FIG. 1 is a diagram illustrating the crimping characteristics of a capacitor, typically an aluminum electrolytic capacitor; (a) is a conceptual diagram illustrating the sealing of a sealing body housed in a case typically made of aluminum by horizontal and vertical crimping; and (b) is a diagram illustrating the relative arrangement and positional relationship between the horizontal crimping width L2 and the nitrile rubber layer and the butyl rubber layer of the sealing body.

[0024] FIG. 1 is a diagram illustrating the relationship between the sealing body and the round rod portion of the lead terminal inserted into the sealing body when the sealing body is mounted in a case (not shown).

[0025] FIG. 2 is a diagram illustrating a cross-sectional structural concept of an aluminum electrolytic capacitor according to another embodiment of the present invention.

[0026] FIG. 3 is a diagram illustrating a structural example in which the characteristics and lifespan of a capacitor deteriorate when the horizontal crimping width relative to the aluminum case is limited to the butyl rubber layer.

[0027] FIG. 4 is an external view of a dumbbell-shaped No. 3 dumbbell test specimen used in the experiment.

[0028] FIG. 5 is a diagram illustrating the arrangement of an outer elastic member and an inner elastic member within the horizontal crimping width L2.

[0012] Aluminum electrolytic capacitors are sometimes mounted on metal frames or electronic circuit boards along with other electronic components, and the entire board is immersed in a refrigerant for immersion cooling to maximize their performance. An electrolyte such as an electrolytic solution is housed inside the capacitor along with the capacitor element, and the opening of the aluminum or other case that houses them is sealed with a seal made of rubber or other material.

[0013] For this reason, the rubber that makes up the sealing body comes into contact with electrolytes such as electrolytic solution on its inner surface and with refrigerants on its outer surface, and also has the function of blocking leakage and intrusion so that the two do not mix with each other. However, the properties and stability of the rubber, electrolytes such as electrolytic solution, and refrigerants are very different, and generally, even if a material has strong resistance to one, it has weak resistance to the other.

[0014] Therefore, if the sealing body were constructed using a single type of rubber stopper, swelling and deterioration would occur from the weaker side, which could have a negative impact on the capacitor's lifespan, durability, and reliability. Therefore, in the present invention, the sealing body has a laminated double-layer structure made of rubber, and the layers are bonded together by vulcanization bonding through simultaneous molding using temperature and pressure. The number of layers of rubber in the sealing body is not limited to two, and any number of layers may be used.

[0015] FIG. 1 is a diagram illustrating a sealing member 1000 of the present invention, which seals the opening of a capacitor case, as viewed from above and at an angle. As shown in FIG. 1 , the sealing member 1000 has a laminated double-layer structure including a nitrile rubber (NBR) layer 1100, which is resistant to the refrigerant used as the immersion coolant, and a butyl rubber (IIR) layer 1200, which is typically resistant to the electrolyte. Examples of suitable electrolyte solvents include ethylene glycol, γ-butyrolactone, sulfolane, water, diethylene glycol, triethylene glycol, propanediol, PEG, glycerin, diglycerin, butanediol, and methylsulfolane. The electrolyte is not limited to an electrolyte solution, but may be a combination of a conductive polymer and an electrolyte solution.

[0016] The sealing body 1000 shown in FIG. 1 has a lead terminal insertion hole 1150 through which a lead terminal 2100 passing through the nitrile rubber layer and the butyl rubber layer can be inserted. The diameter D of the sealing body is 12.5 mm, the thickness H1 of the nitrile rubber layer 1100 is 2 mm, and the thickness H2 of the butyl rubber layer 1200 is 3 mm, but these dimensional values ​​are examples and are not intended to be limiting. The nitrile rubber layer 1100, which comes into contact with the refrigerant, is highly durable and reliable, especially against hydrocarbon-based refrigerants. On the other hand, the butyl rubber layer 1200, which comes into contact with the electrolyte and the like, is highly durable and reliable against the electrolyte of the capacitor.

[0017] The nitrile rubber layer 1100 and the butyl rubber layer 1200 are simultaneously molded by vulcanization bonding while applying temperature and pressure, thereby completing the sealing body 1000 shown in Fig. 1. The layer that comes into contact with the refrigerant can be made of not only nitrile rubber but also fluororubber or acrylic rubber. The layer that comes into contact with the electrolyte can be made of not only butyl rubber but also ethylene propylene diene rubber.

[0018] (Regarding vulcanization bonding during simultaneous molding) Examples of molding methods for laminated rubber include compression molding and transfer molding (injection molding), but the molding method is not particularly limited and any known method can be used. Furthermore, vulcanization bonding during simultaneous molding by laminating the inner elastic member and the outer elastic member and applying temperature and pressure is a preferred technique for firmly bonding the interface between the outer elastic member and the inner elastic member. For example, molding rubber is performed using compression molding or injection molding, but bonding two layers of rubber can be achieved by applying temperature and pressure in a mold to bond the layers together using the vulcanizing agent contained in each rubber layer.

[0019] When laminating the inner elastic member and the outer elastic member and simultaneously applying temperature and pressure to vulcanize and bond them by simultaneous molding, the temperature and pressure to be applied are not particularly limited. The temperature and pressure to be applied may be changed depending on the equipment used. For example, the temperature during molding may be 160°C to 220°C. For example, the pressure during molding may be 10 to 150 kg / cm. ２ That's fine too.

[0020] 2A and 2B are diagrams illustrating the crimping (swaging) characteristics of a capacitor, a typical example of which is an aluminum electrolytic capacitor. FIG. 2A is a conceptual diagram illustrating the state in which a sealing body 1000 housed in a case 1300, a typical example of which is made of aluminum, is crimped and sealed using a horizontal crimping roll 2500 and a vertical crimping roll 2600. FIG. 2B is a diagram illustrating the horizontal crimping width L2, the nitrile rubber layer 1100 and the butyl rubber layer 1200 of the sealing body 1000, and the relative arrangement and positional relationship.

[0021] 2(a), all necessary elements are housed in case 1300, and finally the opening of case 1300 is sealed with sealing body 1000. Then, while rotating case 1300, horizontal crimping roll 2500 and vertical crimping roll 2600 simultaneously press and crimp the case 1300. Also, in FIG. 2(b), aluminum electrolytic capacitor 2000 has capacitor element 1400 sealed in aluminum case 1300 by sealing body 1000, which is a laminated double layer of nitrile rubber layer 1100 and butyl rubber layer 1200.

[0022] As shown in FIG. 2( b), the lead terminal 2100 has a round bar portion 2110 embedded in the sealing body 1000, and the round bar portion 2110 is thicker than the upper lead terminal 2100. The thickness H1 of the nitrile rubber layer 1100 and the thickness H2 of the butyl rubber layer 1200 add up to the total thickness H3 of the sealing body 1000. As can be seen from FIG. 2( b), the horizontal crimping width L2 includes the interface (bonding surface) between the nitrile rubber layer 1100 and the butyl rubber layer 1200. In other words, the horizontal crimping extends across both the nitrile rubber layer 1100 and the butyl rubber layer 1200. This ensures stronger and more reliable adhesion and sealing between the aluminum case 1300 and the sealing body 1000. The horizontal crimping width L2 refers to the length over which the aluminum case 1300 and the sealing body 1000 are in close contact with each other due to the horizontal crimping.

[0023] Although there are no particular limitations on the length of L2, it is preferable that the ratio of the length of L2 to the thickness H3 of the entire sealing body 1000 be 20 to 90%. For example, when the thickness H3 of the entire sealing body 1000 is 5 mm, it is preferable that the length of L2 be 1.5 mm to 4 mm.

[0024] 5, if the width of the lateral crimping to the aluminum case 2 is limited to the butyl rubber layer 3, there is a concern that the adhesion and sealing between the nitrile rubber layer 4 and the aluminum case 2 will be insufficient, causing the refrigerant to penetrate into the capacitor from the outside and causing swelling and deterioration of the butyl rubber layer 3, resulting in deterioration of the characteristics and shortening of the life of the capacitor.In addition, if this condition occurs, there is a concern that the electrolyte inside the capacitor will leak to the outside.

[0025] 2(b) , the positional relationship between the transverse crimp width L2 and the lead terminal 2100 is described. It is preferable that the round bar portion 2110 of the lead terminal 2100 is always included within the range of the transverse crimp width L2. Because the transverse crimp width L2 is the area where the sealing body 1000 is externally crimped and compressed inward, it is preferable that the round bar portion 2110 is compressed and pressed by the surrounding sealing body due to this pressure, thereby achieving stronger adhesion. It is even more preferable that the butyl rubber layer 1200 is crimped more (by a larger width and length) than the nitrile rubber layer 1100 within the range of the transverse crimp width L2. In other words, it is preferable that the surface or distance where the aluminum case and the butyl rubber layer are in close contact with each other due to the transverse crimping be longer than that of the nitrile rubber layer, or that the area of ​​contact between the aluminum case and the butyl rubber layer due to the transverse crimping be larger than that of the nitrile rubber layer. The sealing body of the present invention, which has a laminated double-layer structure (preferably co-molded and vulcanized) using rubbers of different materials, is expected to reliably prevent the intrusion of immersion cooling refrigerant into the capacitor and the leakage of electrolyte to the outside of the capacitor over a long period of time.

[0026] (Regarding the Round Bar Portion) The round bar portion 2110 of the lead terminal shown in Figures 2, 3(b), etc. is preferably made of aluminum. The surface of the round bar portion 2110 may be coated with a natural oxide film or a chemical conversion film. It may also be coated with a coating agent such as a resin material or a ceramic material. By coating the surface of the round bar portion of the lead terminal with a natural oxide film, a chemical conversion film, or a coating agent, it is expected that the gap between the lead terminal insertion hole 1150 in the sealing body and the round bar portion 2110 of the lead terminal 2100 inserted into the lead terminal insertion hole 1150 in the sealing body can be prevented from the intrusion of the immersion cooling refrigerant. The diameter of the round bar portion 2110 may be, for example, 0.3 to 3.0 mm, and is not particularly limited as long as it can be tightly attached to the sealing body.

[0027] 3A and 3B are diagrams illustrating the relationship between the sealing body 1000 and the round bar portion 2110 of the lead terminal 2100 inserted into the lead terminal insertion hole 1150 of the sealing body 1000 when the sealing body 1000 is mounted in a case (not shown). As shown in Fig. 3A, the round bar portion 2110 of the lead terminal 2100 is maintained in a tight contact state with all or part of the round bar portion 2110 compressed by the sealing body 1000 to an extent that liquid or the like does not leak or intrude through the peripheral interface of the round bar portion 2110. In terms of sealing, the sealing body 1000 functions like a packing, so to speak, and ensures airtightness and liquidtightness at the peripheral interface of the round bar portion 2110.

[0028] 3(a), since sealing body 1000 of the present invention has a laminated double-layer structure, it is preferable that the upper nitrile rubber layer 1100 abuts against lead terminal insertion hole 1150 of the sealing body around at least a portion of round bar portion 2110, forms tight contact with the hole 1150 without any gaps, and is compressed and pressed to ensure airtightness and liquid-tightness. This reliably prevents the immersion cooling refrigerant filling the outside of the capacitor from reaching the inside of the capacitor, particularly butyl rubber layer 1200, during actual operation. If there is butyl rubber exposed to the refrigerant, the butyl rubber will swell and change in quality, raising concerns that the airtightness and liquid-tightness of the inside of the capacitor will be compromised.

[0029] 3(b), it is further preferable that the contact portion 5000 between the lead terminal 2100 and the nitrile rubber layer 1100 on the outermost surface (top surface in FIG. 3) of the nitrile rubber layer 1100 is tightly adhered and compressed / pressed without any gaps around at least a portion of the periphery of the lead terminal 2100, in order to ensure airtightness and liquid tightness. A through hole or notch of a predetermined diameter or shape may be provided in advance at a corresponding portion of the outermost surface (top surface in FIG. 3) of the sealing body 1000 into which the lead terminal 2100 (including the round bar portion 2110) is inserted, or the rubber thickness of the sealing body 1000 at the corresponding portion may be made thin so that the tip of the lead terminal 2100 breaks through it, thereby allowing the lead terminal 2100 to penetrate.

[0030] Immersion cooling systems are available in single-phase (1-phase) and two-phase (2-phase) configurations. In a single-phase (1-phase) immersion cooling system, electronic circuit boards such as server motherboards stored in a data center are immersed in an inert cooling liquid, which acts as a refrigerant. The inert cooling liquid heated by the boards is transported via a path to a heat exchanger where it is cooled. The cooled inert cooling liquid is then transported via a path to the boards such as motherboards and circulated to cool them.

[0031] In a two-phase immersion cooling system, the coolant heated by the circuit board vaporizes, and the vaporized coolant is cooled by cooling water, turning into droplets and returning to its original liquid form. In this case, the coolant heated by the electronic circuit board is an inert liquid with a low boiling point, so it quickly vaporizes and removes the heat of vaporization. Meanwhile, the heated water is pumped through the cooling device and circulated as cooling water.

[0032] The method of cooling a metal frame or circuit board on which the capacitor of the present invention is mounted by immersion cooling is carried out by immersing a part or the whole of the capacitor in an immersion refrigerant. To improve the cooling efficiency, it is preferable to provide a space between the mounting metal frame or circuit board and at least the lead terminals 2100, which generate a large amount of heat, so that the cooling medium can circulate throughout the capacitor.

[0033] Another Embodiment Fig. 4 is a diagram illustrating a cross-sectional conceptual diagram of the configuration of an aluminum electrolytic capacitor 3000 according to another embodiment of the present invention. In Fig. 4, an electrolyte 2450 and a capacitor element 2400 are sealed within an aluminum case 2500 by a sealing member 1000. The sealing member 1000 has a laminated structure of a nitrile rubber (NBR) layer 1100 and a butyl rubber (IIR) layer 1200, and hermetically closes an opening 2530 of the case. A pair of lead terminals 2100 are exposed to the outside and extend through the sealing member 1000.

[0034] The capacitor 3000 shown in FIG. 4 is immersed in a hydrocarbon-based refrigerant 2300 so that the entire capacitor 3000 is cooled by the hydrocarbon-based refrigerant 2300. The aluminum case 2500 of the capacitor 3000 has a circumferentially formed transverse crimp mark 2510 and a transverse crimp mark 2520 at two locations. The transverse crimp mark 2510 presses the nitrile rubber (NBR) layer 1100 by crimping pressure at that location, and the transverse crimp mark 2520 presses the butyl rubber (IIR) layer 1200 by crimping pressure at that location. In this structure, between the transverse crimp mark 2510 in the nitrile rubber layer and the transverse crimp mark 2520 in the butyl rubber layer, there are formed regions where the aluminum case and the rubber are in sufficient contact and regions where the aluminum case and the rubber are not in sufficient contact. In the regions where the aluminum case and the rubber are insufficiently in contact, the stress applied to the rubber by the transverse crimping is less than in the regions where the aluminum case and the rubber are in sufficient contact.

[0035] The respective transverse crimping of each rubber layer ensures that each rubber layer of sealing body 1000 exhibits a tight fit, tightly closed, and sealing function. This reliably prevents both the intrusion of liquids from outside the capacitor and leakage from inside, with transverse crimping marks 2510 preventing liquids from entering from the outside from reaching butyl rubber (IIR) layer 1200, and transverse crimping marks 2520 more reliably preventing liquids from leaking from the inside from reaching nitrile rubber (NBR) layer 1100. Furthermore, in capacitor 3000 shown in FIG. 4 , the configuration and structure of pair of lead terminals 2100, as well as their relative positional relationship with other components, including their round bar portions, can adopt the same description and configuration as described above.

[0036] In the present invention, the sealing body has a laminated double structure made of different materials, and preferably the relative positions of the horizontal crimping points and the sealing body, and the horizontal crimping points and the round bar portion of the lead terminal are optimized, and more preferably the sealing body and the round bar portion inserted into the lead terminal insertion hole 1150 are in an appropriate compression relationship, thereby improving the reliability and durability of capacitors, particularly aluminum electrolytic capacitors, and achieving a longer lifespan.

[0037] In this embodiment, the sealing body was produced by stacking a 3 mm sheet of a butyl rubber compound containing alkylphenol formaldehyde resin and a 2 mm sheet of an acrylonitrile rubber compound containing alkylphenol formaldehyde resin, placing them in a mold, and vulcanizing them by compression molding to form a laminated rubber.

[0038] Furthermore, the outer surface (the surface not covered by the case) and inner surface (the surface in contact with the electrolyte) of the sealing body are each made of elastic material and are vulcanization bonded together, thereby achieving strong adhesion and stability. If a two-layer rubber that is not vulcanization bonded (where the layers simply abut against each other) were used as the sealing body for a capacitor, the horizontal crimping would deform the boundaries of the rubber, creating gaps at the rubber interfaces and potentially weakening the sealing performance due to rubber deformation.

[0039] (Supplementary explanation regarding the relationship between the immersion cooling refrigerant and the capacitor sealing member) Known hydrocarbon refrigerants for immersion cooling of electronic components such as capacitors include petroleum hydrocarbons such as paraffinic mineral oil and naphthenic mineral oil, synthetic oils such as poly-α-olefins (PAOs) and artificial petroleum obtained by Fischer-Tropsch synthesis, as well as bio-oil, vegetable oil, lubricating oil, etc. Of these, the hydrocarbon refrigerant is preferably one or more selected from petroleum hydrocarbons and synthetic oils, more preferably one or more selected from poly-α-olefins (PAOs) and artificial petroleum, and even more preferably artificial petroleum.

[0040] The petroleum hydrocarbons and synthetic petroleum may be a mixture of hydrocarbons having 15 to 50 carbon atoms, but preferably a mixture of hydrocarbons having 18 to 50 carbon atoms. Each hydrocarbon may be selected from cyclic hydrocarbons, branched hydrocarbons, and straight-chain hydrocarbons, but it is preferable to select branched or straight-chain hydrocarbons.

[0041] From the viewpoint of reducing the environmental load, the hydrocarbon refrigerant is preferably a fluorine-free hydrocarbon, and more preferably a petroleum-based hydrocarbon. In this description, "fluorine-free hydrocarbon" means a hydrocarbon that does not contain fluorine atoms as constituent atoms, but does not exclude the unintentional inclusion of fluorine or a fluorine-containing compound as an impurity.

[0042] In a capacitor usable for immersion cooling in a coolant, the coolant is a hydrocarbon refrigerant, and the sealing body of the capacitor has an outer elastic member in a region that comes into contact with the coolant during immersion cooling, and from the viewpoint of preventing the outer elastic member from swelling due to the coolant, the Hansen solubility parameter distance with the coolant is preferably 8.0 or more. Furthermore, the rubber composition or components of the outer elastic member may be one or more selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber.

[0043] To enable the application of a capacitor to immersion cooling using a coolant such as hydrocarbon, the sealing body must be resistant to swelling caused by the coolant. As a criterion for selecting such a sealing body material, the Hansen solubility parameter (HSP) is considered, and swelling of the sealing body can be suppressed by ensuring that the rubber member disposed in the region of the sealing body that comes into contact with the coolant has an HSP distance of 8.0 or more from the coolant.

[0044] The HSP is a value that quantifies the solubility of a substance A in another substance B using a multidimensional vector. In general, the shorter the HSP distance between two substances, the higher the solubility of substance A in substance B and the higher the compatibility with substance B.

[0045] Furthermore, the HSP can be calculated from the chemical structural formula using HSP analysis software such as HSPiP (Hansen Solubility Parameters in Practice, Ver. 5.4.05). The HSP is expressed by three components: δD (dispersion term), δP (polarization term), and δH (hydrogen bond term). The units of δD, δP, δH, and Ra are MPa 1 / 2. The HSP distance between two compounds is the distance between two points when the respective δD, δP, and δH values ​​are plotted on a three-dimensional orthogonal coordinate system, and can be calculated according to the following formula. In this description, the HSP is assumed to be a value at 25°C, and the rubber component can be considered to correspond to substance B, and the coolant can be considered to correspond to substance A.

[0046] In the formula HSP distance (Ra) = {4 × (δD1 - δD2)2 + (δP1 - δP2)2 + (δH1 - δH2)2}1 / 2, δD1, δP1, and δH1 are respectively δD, δP, and δH of substance A. In the above formula, δD2, δP2, and δH2 are respectively δD, δP, and δH of substance B.

[0047] In this description, the HSP distance between the outer elastic member and the coolant is 8.0 or more, and may be preferably 10.0 or more, more preferably 12.0 or more, even more preferably 15.0 or more, and particularly preferably 20.0 or more, in order to further suppress swelling of the sealing body. The upper limit of the HSP distance between the rubber component and the coolant is not particularly limited, but may preferably be 50.0 or less or 40.0 or less. That is, preferred ranges of the HSP distance between the rubber component and the coolant can typically be 8.0 or more and 50.0 or less, 10.0 or more and 40.0 or less, 12.0 or more and 40.0 or less, 15.0 or more and 40.0 or less, and 20.0 or more and 40.0 or less.

[0048] Furthermore, if the HSP distance between the outer elastic member and the coolant is within the above-mentioned range, swelling of the outer elastic member due to the coolant during immersion cooling can be significantly suppressed, making it possible to substantially avoid the occurrence of problems such as deterioration in the characteristics and shortened lifespan of electronic components such as capacitors, and deformation of the metal case.

[0049] In addition, "HSP distance between the outer elastic member and the coolant" means the HSP distance between the coolant and the rubber component that forms the outer elastic member when the rubber component that forms the outer elastic member is a mixture of two or more types of rubber, or the HSP distance between the coolant and the mixture when the coolant is a mixture of two or more types of refrigerants, or the HSP distance between the mixture and the rubber component that forms the outer elastic member when the rubber component that forms the outer elastic member is the above mixture and the coolant is the above mixture. Therefore, it is thought that there is no problem even if the rubber component that forms the outer elastic member contains rubber whose HSP distance to the coolant is less than the above lower limit, as long as the HSP distance to the coolant as a whole is equal to or greater than the above lower limit.

[0050] The rubber component that forms the outer elastic member can be appropriately selected so that the HSP distance with the coolant falls within the above-mentioned range, and the type is not particularly limited. However, rubbers that contain heteroatoms such as nitrogen atoms, oxygen atoms, chlorine atoms, sulfur atoms, and fluorine atoms in the main chain or side chain are known to tend to have a large HSP distance with hydrocarbon-based refrigerants, and are therefore suitable.

[0051] More specifically, the rubber component that becomes the outer elastic member can be one or more selected from the group consisting of acrylic rubber, fluororubber, nitrile rubber, hydrogenated nitrile rubber, urethane rubber, polysulfide rubber, epichlorohydrin rubber, chloroprene rubber, and chlorosulfonated polyethylene rubber, because it has a large HSP distance with the coolant, and it is more preferable that the rubber component be one or more selected from the group consisting of acrylic rubber, fluororubber, nitrile rubber, and hydrogenated nitrile rubber.

[0052] Nitrile rubber is a copolymer of acrylonitrile and butadiene, and generally contains 15% to 60% by weight of acrylonitrile units. Nitrile rubber can also be copolymerized with other monomers such as ethylene, conjugated dienes, and vinyl compounds.

[0053] Hydrogenated nitrile rubber is a rubber obtained by hydrogenating nitrile rubber, and the hydrogenation rate of the hydrogenated nitrile is not particularly limited, but is generally known to be in the range of 70% to 100%.

[0054] Acrylic rubber refers to rubber containing acrylic ester as the main component. "Containing acrylic ester as the main component" is understood to mean that the content of acrylic ester units in the acrylic rubber is 50% by weight or more. In this specification, "acrylic ester" may also be understood to mean "methacrylic ester." Acrylic rubber may be copolymerized with vinyl acetate, ethylene, and other monomers such as crosslinkable monomers. Known examples of crosslinkable monomers include monomers and diene-based monomers having carboxyl groups, epoxy groups, and hydroxyl groups.

[0055] Fluorine rubber is a homopolymer or copolymer containing fluorine atoms in the main chain or side chain, and is obtained by polymerizing fluorine-containing monomers such as hexafluoropropylene, tetrafluoroethylene, vinylidene fluoride, etc. Fluorine rubber may also be copolymerized with fluorine-free monomers such as ethylene and propylene.

[0056] The chloroprene rubber may be a diene rubber obtained by polymerizing chloroprene.

[0057] Chlorosulfonated polyethylene rubber is understood to be rubber in which chlorine atoms and chlorosulfonyl groups (-SO2Cl) are bonded to the polyethylene backbone.

[0058] The urethane rubber is not particularly limited as long as it has a urethane bond in its molecular structure, but is preferably an ester-based urethane rubber.

[0059] Polysulfide rubber has disulfide bonds (-S-S-) in the main chain, may contain a slightly branched structure, and may be a liquid polymer with thiol groups at the ends. Polysulfide rubber can be cured with metal oxides, organic peroxides, etc.

[0060] Epichlorohydrin rubber is a general term for epichlorohydrin homopolymer (CO), epichlorohydrin and ethylene oxide copolymer (ECO), epichlorohydrin and allyl glycidyl ether copolymer (GCO), and epichlorohydrin, ethylene oxide, and allyl glycidyl ether copolymer (GECO).

[0061] The rubber component of the outer elastic member may be a single rubber, or a combination or mixture of any two or more types of rubber. When the rubber component of the outer elastic member is a mixture of two or more types of rubber, the rubber component may contain any amount of rubber whose HSP distance to the coolant is less than the above-mentioned lower limit, as long as the HSP distance between the mixed rubber and the coolant is equal to or greater than the above-mentioned lower limit. Examples of rubber whose HSP distance to the coolant is less than the above-mentioned lower limit include ethylene propylene diene rubber (EPDM) and butyl rubber.

[0062] In order to form the rubber member that will become the outer elastic member, in addition to the rubber component described above, any other components may be contained as needed. Typical examples of the optional other components include, but are not limited to, vulcanizing agents, fillers, and processing aids.

[0063] Known examples of vulcanizing agents include sulfur, sulfur donors such as 4,4'-dithiodimorpholine and tetramethylthiuram disulfide, organic peroxides such as dicumyl peroxide and benzoyl peroxide, metal oxides such as zinc oxide, polyfunctional amine compounds such as hexamethylenediamine carbamate and 4,4'-diaminodiphenyl ether, and alkylphenol polymers such as alkylphenol-formaldehyde resins and halogenated alkylphenol-formaldehyde resins.

[0064] When the rubber composition for the outer elastic member contains a vulcanizing agent, the content of the vulcanizing agent in the rubber composition is not particularly limited, but is preferably at least 0.1 part by weight, more preferably at least 0.5 part by weight, and even more preferably at least 1 part by weight, and is preferably at most 25 parts by weight, and even more preferably at most 20 parts by weight, per 100 parts by weight of the rubber component for the outer elastic member. That is, when the rubber composition for the outer elastic member contains a vulcanizing agent, the preferred content of the vulcanizing agent per 100 parts by weight of the rubber component for the outer elastic member can typically be in the range of 0.1 to 25 parts by weight, or 0.5 to 20 parts by weight.

[0065] As the filler, inorganic fillers such as clay, talc, carbon black, silica, calcium carbonate, etc. are preferred. Silica may be surface-treated with a silane coupling agent. Furthermore, the rubber composition preferably contains carbon black, as this is expected to have the effect of increasing the strength of the rubber member.

[0066] When the rubber composition for the outer elastic member contains a filler, the content of the filler in the rubber composition is not particularly limited, but is preferably 10 parts by weight or more, more preferably 20 parts by weight or more, and even more preferably 30 parts by weight or more, per 100 parts by weight of the rubber component for the outer elastic member, and may be preferably 250 parts by weight or less, more preferably 200 parts by weight or less, and even more preferably 180 parts by weight or less. In other words, when the rubber component for the outer elastic member contains a filler, the preferred range of the content of the filler per 100 parts by weight of the rubber component for the outer elastic member is typically 10 parts by weight or more and 250 parts by weight or less, 20 parts by weight or more and 200 parts by weight or less, or 30 parts by weight or more and 180 parts by weight or less.

[0067] As the processing aid, known rubber processing aids can be used. Known examples of known rubber processing aids include fatty acids having from 12 to 30 carbon atoms, such as palmitic acid, stearic acid, ricinoleic acid, and lauric acid; salts of fatty acids having from 12 to 30 carbon atoms, such as barium stearate, calcium stearate, and zinc stearate; and esters of fatty acids having from 12 to 30 carbon atoms, such as ricinoleic acid esters, stearic acid esters, palmitic acid esters, and lauric acid esters. Among the above examples, it is preferable to include stearic acid as the rubber component that becomes the outer elastic member, because this can improve the dispersibility of each component in the rubber composition and the fluidity of the rubber component, thereby improving moldability.

[0068] When a processing aid is contained in the rubber component that forms the outer elastic member, the content of the processing aid in the rubber component is not particularly limited, but may be preferably 0.1 part by weight or more, more preferably 0.3 part by weight or more, and even more preferably 0.5 part by weight or more, per 100 parts by weight of the rubber component, and may be preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less. When a processing aid is contained in the rubber component that forms the outer elastic member, the content of the processing aid per 100 parts by weight of the rubber component may typically be in the range of 0.1 part by weight to 20 parts by weight, 0.3 parts by weight to 10 parts by weight, or 0.5 parts by weight to 5 parts by weight.

[0069] (Preferred Upper and Lower Limits for an HSP of 8.0 or More) The Hansen Solubility Parameter Distance (HSP) between the outer elastic member and the hydrocarbon-based refrigerant is preferably 8.0 or more. Based on the criterion that changes in the rubber member are reduced by immersion in a coolant, it is even more preferable that the upper limit of the HSP is 25.0 and the lower limit is 8.6. Furthermore, it is preferable that the hardness change rate is between -20% and 10%. Regarding this, the hardness change of a dumbbell-shaped test piece caused by immersion in a hydrocarbon-based refrigerant was evaluated according to the method described below, and the results are shown in Table 1. The upper limit of 25.0 and the lower limit of 8.6 for the HSP are circled in Table 1 below.

[0070] [Evaluation of Hardness Change Due to Immersion] (Immersion Test) Three dumbbell-shaped test pieces were immersed in a test refrigerant contained in a test tube. The test tube was heated in an oven set at 85°C for 168 hours. The test tube was removed from the oven and allowed to cool at room temperature for 30 minutes. After cooling, the dumbbell-shaped test pieces were removed from the test refrigerant, and the test refrigerant adhering to the dumbbell-shaped test pieces was wiped off.

[0071] (Calculation of Hardness Change Rate) Using a durometer ("GX-01A"; Type A, manufactured by Teroc Corporation) in accordance with JIS K 6253-3:2012 "Vulcanized rubber and thermoplastic rubber - Determination of hardness - Part 3: Durometer hardness" (established on March 21, 2012), the hardness of three dumbbell-shaped test pieces before the immersion test was measured, and the median value of each measurement value was determined as the hardness of the dumbbell-shaped test piece before the immersion test. The hardness of the dumbbell-shaped test piece after the immersion test was calculated in the same manner. The hardness change rate of the dumbbell-shaped test piece was calculated by applying these calculation results to the following [Equation 1]. The results are shown in Table 1.

[0072]

[0073] Example 1 100 parts by weight of acrylonitrile butadiene rubber, 50 parts by weight of carbon black, 1 part by weight of stearic acid, and 5 parts by weight of dicumyl peroxide were kneaded, and the resulting composition was vulcanized at 170° C. for 10 minutes to obtain a sheet having a thickness of 2 mm. This sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0074] The HSP of acrylonitrile-butadiene rubber and a hydrocarbon-based refrigerant, Fischer-Tropsch distilled heavy oil (a mixture of branched and linear hydrocarbons having a carbon number of 18 to 50) was calculated using the HSP analysis software "HSPiP (Ver. 5.4.05)". The calculated HSP values ​​of the acrylonitrile-butadiene rubber and the hydrocarbon-based refrigerant, as well as the HSP distance between the acrylonitrile-butadiene rubber and the hydrocarbon-based refrigerant obtained from these calculated values, are shown in Table 1.

[0075] [Example 2] A dumbbell-shaped test piece (No. 3) was prepared in the same manner as in Example 1, except that 100 parts by weight of acrylonitrile butadiene rubber was changed to 100 parts by weight of ethylene-vinyl acetate-acrylic acid ester copolymer, and 5 parts by weight of dicumyl peroxide was changed to 1 part by weight of hexamethylenediamine carbamate.

[0076] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0077] Example 3 A dumbbell-shaped test piece (size 3) was prepared in the same manner as in Example 1, except that 100 parts by weight of acrylonitrile butadiene rubber was changed to 100 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer.

[0078] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0079] Example 4 A dumbbell-shaped test piece (No. 3) was prepared in the same manner as in Example 1, except that 100 parts by weight of the acrylonitrile-butadiene rubber was changed to 100 parts by weight of hydrogenated acrylonitrile-butadiene rubber and the amount of dicumyl peroxide was changed to 10 parts by weight.

[0080] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0081] Comparative Example 1 A dumbbell-shaped test piece (No. 3) was prepared in the same manner as in Example 1, except that 100 parts by weight of acrylonitrile butadiene rubber was changed to 100 parts by weight of ethylene propylene rubber (EPDM).

[0082] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0083] [Comparative Example 2] A dumbbell-shaped test piece (No. 3) was prepared in the same manner as in Example 1, except that 100 parts by weight of acrylonitrile butadiene rubber was changed to 100 parts by weight of butyl rubber, 5 parts by weight of dicumyl peroxide was changed to 12 parts by weight of alkylphenol formaldehyde resin, and the vulcanization conditions were changed to 170°C for 40 minutes.

[0084] The HSP and HSP distance were calculated, and the hardness change was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0085] Example 5 20 parts by weight of butyl rubber, 80 parts by weight of nitrile rubber, 50 parts by weight of carbon black, 1 part by weight of stearic acid, and 12 parts by weight of alkylphenol-formaldehyde resin were kneaded, and the resulting composition was vulcanized at 170°C for 40 minutes to obtain a sheet with a thickness of 2 mm. This sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0086] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0087] Example 6 A dumbbell-shaped test piece (size 3) was prepared in the same manner as in Example 5, except that the rubber component consisting of a mixture of 20 parts by weight of butyl rubber and 80 parts by weight of nitrile rubber was changed to a rubber component consisting of a mixture of 40 parts by weight of butyl rubber and 60 parts by weight of nitrile rubber.

[0088] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0089] Example 7 A dumbbell-shaped test piece (size 3) was prepared in the same manner as in Example 5, except that the rubber component consisting of a mixture of 20 parts by weight of butyl rubber and 80 parts by weight of nitrile rubber was changed to a rubber component consisting of a mixture of 50 parts by weight of butyl rubber and 50 parts by weight of nitrile rubber.

[0090] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0091] Example 8 A dumbbell-shaped test piece (size 3) was prepared in the same manner as in Example 5, except that the rubber component consisting of a mixture of 20 parts by weight of butyl rubber and 80 parts by weight of nitrile rubber was changed to a rubber component consisting of a mixture of 60 parts by weight of butyl rubber and 40 parts by weight of nitrile rubber.

[0092] Example 9 A dumbbell-shaped test piece (size 3) was prepared in the same manner as in Example 5, except that the rubber component consisting of a mixture of 20 parts by weight of butyl rubber and 80 parts by weight of nitrile rubber was changed to a rubber component consisting of a mixture of 65 parts by weight of butyl rubber and 35 parts by weight of nitrile rubber.

[0093] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0094] Example 10: 65 parts by weight of ethylene propylene rubber (EPDM), 35 parts by weight of nitrile rubber, 50 parts by weight of carbon black, 1 part by weight of stearic acid, and 5 parts by weight of dicumyl peroxide were kneaded, and the resulting composition was vulcanized at 170° C. for 10 minutes to obtain a sheet with a thickness of 2 mm. This sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0095] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0096] Example 11 65 parts by weight of ethylene propylene rubber (EPDM), 35 parts by weight of acrylic rubber, 50 parts by weight of carbon black, 1 part by weight of stearic acid, and 5 parts by weight of dicumyl peroxide were kneaded, and the resulting composition was vulcanized at 170° C. for 10 minutes to obtain a sheet with a thickness of 2 mm. This sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0097] The calculation of HSP and HSP distance, and the evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0098] Examples 12 to 15 The dumbbell-shaped test pieces (Type 3) prepared in each of Examples 1 to 4 were subjected to immersion tests in the same manner as in Example 1, except that the test refrigerant was poly-α-olefin (poly(1-decene)), which is a hydrocarbon refrigerant.

[0099] Moreover, calculation of HSP and HSP distance, and evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0100] [Comparative Examples 3 and 4] The dumbbell-shaped test pieces (Type 3) prepared in Comparative Examples 1 and 2 were subjected to immersion tests in the same manner as in Example 1, except that poly-α-olefin (poly(1-decene)), a hydrocarbon-based refrigerant, was used as the test refrigerant.

[0101] Moreover, calculation of HSP and HSP distance, and evaluation of hardness change were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0102]

[0103] From Table 1 above, it was confirmed that when the HSP distance between the rubber component and the coolant was less than 8.0 (Comparative Examples 1 to 4), the hardness change rate of the dumbbell-shaped test specimen was -24% or less. This indicates that rubber members formed from vulcanizates of rubber compositions containing such rubber components swell in the coolant, resulting in a significant decrease in hardness. On the other hand, when the HSP distance between the rubber component and the coolant was 8.0 or more (Examples 1 to 15), particularly when the HSP distance was between 8.6 and 25.0 (Examples 3 and 9), it was confirmed that the hardness change of the dumbbell-shaped test specimen was small, regardless of the type of rubber component and the type of coolant. This indicates that more preferably, rubber members formed from vulcanizates of rubber compositions containing rubber components having an HSP distance between the rubber component and the coolant of 8.6 to 25.0 are less likely to swell in the coolant and can maintain their hardness even after immersion in the coolant.

[0104] (Regarding Vulcanization Adhesion of Elastic Members) When the inner and outer elastic members were immersed in a liquid immersion refrigerant, a decrease in adhesive strength at the interface (1500°C) where the inner and outer elastic members were joined was confirmed, confirming the existence of an optimal adhesive strength for laminated rubber used in liquid immersion cooling applications. Calculation of Changes in Adhesive Strength of Laminated Rubber Using an autograph ("AGS-X Series," manufactured by Shimadzu Manufacturing Co., Ltd.), the adhesive strength of three dumbbell-shaped test specimens was measured before the immersion test in accordance with JIS K6251:2023, "Determination of Tensile Properties of Vulcanized and Thermoplastic Rubber," and the average of the measured values ​​was calculated as the adhesive strength of the dumbbell-shaped test specimens before the immersion test. The adhesive strength of the dumbbell-shaped test specimens after the immersion test was measured in the same manner. The test conditions were as follows: The adhesive strength of the interface was evaluated before and after immersion in distilled heavy oil (85°C, 168 hours) as a hydrocarbon refrigerant (number of samples: N = 3 for each test).

[0105] - Preparation method for experimental level 1 (NBR-IIR) Preparation of NBR sheet 100 parts by weight of acrylonitrile butadiene rubber, 50 parts by weight of carbon black, 100 parts by weight of inorganic filler, 1 part by weight of stearic acid, and 12 parts by weight of alkylphenol-formaldehyde resin were kneaded to obtain a 2 mm thick NBR sheet. Preparation of IIR sheet A 2 mm thick IIR sheet was obtained in the same manner as the preparation of the NBR sheet, except that the ingredients were changed to 100 parts by weight of butyl rubber and 8 parts by weight of alkylphenol-formaldehyde resin. The prepared NBR sheet and butyl sheet (each 200 x 50 x 2.0 mm) were prepared, and the NBR sheet and butyl sheet were placed side by side in a mold and pressed at 190 ± 10°C for 4 hours (pressure 50 kg / cm). ２ The obtained sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0106] Preparation method for experimental level 2 (NBR-IIR) A dumbbell-shaped test piece (No. 3 type) was prepared in the same manner as in experimental level 1, except that the butyl sheet was prepared using 12 parts by weight of alkylphenol-formaldehyde resin.

[0107] Preparation method for experimental level 3 (NBR-IIR) A dumbbell-shaped test piece (No. 3 type) was prepared in the same manner as in experimental level 1, except that the butyl sheet was prepared using 14 parts by weight of alkylphenol-formaldehyde resin.

[0108] Preparation method for experimental level 4 (NBR-EPDM) Preparation of EPDM sheet A dumbbell-shaped test piece (No. 3) was prepared in the same manner as in experimental level 1, except that the amount of ethylene propylene rubber (EPDM) was changed to 100 parts by weight and dicumyl peroxide to 5 parts by weight.

[0109] - Preparation method for experimental level 5 (F-EPDM) Preparation of F sheet 100 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer (F; fluorine), 50 parts by weight of carbon black, 100 parts by weight of inorganic filler, 1 part by weight of stearic acid, and 5 parts by weight of dicumyl peroxide were kneaded to obtain an F sheet with a thickness of 2 mm. Preparation of EPDM sheet An EPDM sheet with a thickness of 2 mm was obtained in the same manner as the EPDM sheet for experimental level 3. The F sheet and EPDM sheet (each 200 x 50 x 2.0 mm) were prepared, and the F sheet and EPDM sheet were set side by side in a mold and pressed at 170±10°C for 10 minutes (pressure 50 kg / cm ２ The obtained sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0110] - Preparation method of experimental level 6 (IIR (35) NBR (65) - IIR) Preparation of IIR (35) NBR (65) sheet 35 parts by weight of butyl rubber, 65 parts by weight of acrylonitrile butadiene rubber, 50 parts by weight of carbon black, 100 parts by weight of inorganic filler, 1 part by weight of stearic acid, and 12 parts by weight of alkylphenol-formaldehyde resin were kneaded to obtain a sheet with a thickness of 2 mm. Preparation of IIR sheet Except for changing to 100 parts by weight of butyl rubber, an IIR sheet with a thickness of 2 mm was obtained in the same manner as the preparation of the IIR (35) NBR (65) sheet. The prepared IIR (35) NBR (65) sheet and IIR sheet (each 200 x 50 x 2.0 mm) were prepared, and the IIR (35) NBR (65) sheet and IIR sheet were set side by side in a mold and pressed at 190 ± 10 ° C for 4 hours (pressure 50 kg / cm ２ The obtained sheet was punched into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0111] Preparation method for experimental level 7 (IIR (65) NBR (35) - IIR) Preparation of IIR (65) NBR (35) sheet A dumbbell-shaped test piece (No. 3) was prepared in the same manner as the preparation method for experimental level 6, except that the mixture was changed from 35 parts by weight of butyl rubber and 65 parts by weight of acrylonitrile butadiene rubber to 65 parts by weight of butyl rubber and 35 parts by weight of acrylonitrile butadiene rubber.

[0112] [Calculation results of changes in adhesive strength of laminated rubber]

[0113] As can be seen from the results shown in Experimental Level 1 above, it can be confirmed that the adhesive strength of the laminated rubber interface (1500) after refrigerant immersion decreased from 2.7 MPa to 0.1 MPa. The laminated rubber interface is subjected to stress and load at the rubber interface (1500) due to lateral crimping as shown in Figure 2. Furthermore, in the liquid immersion evaluation test, it is possible that the refrigerant may reach the rubber interface over the test time. If the strength of the rubber interface is insufficient, the sealing performance will be lost, raising concerns that the refrigerant may enter the capacitor from the outside. The dumbbell test specimen is shown in Figure 6. Figure 6 is an external view of the dumbbell-shaped No. 3 dumbbell test specimen used in this experiment.

[0114] ・How to adjust adhesive strength [Adjusting adhesive strength]

[0115] The results of Experimental Levels 2 to 7 shown in Table 3 above demonstrate that adhesive strength can be adjusted by the polymer type and vulcanization method. However, Experimental Levels 1, 4, and 7 shown here do not include evaluation of the final capacitor product. For example, the adhesive strength before immersion in a hydrocarbon-based refrigerant is preferably 6.0 to 20 MPa. If the adhesive strength before immersion in a hydrocarbon-based refrigerant exceeds 25 MPa, the crosslink density at the interface (1500) of the rubber component increases, and the rubber component loses its conformability due to stress and load caused by lateral crimping. Poor conformability of the rubber component leads to reduced adhesion between the aluminum case and the rubber, and between the round bar and the rubber component. Furthermore, the adhesive strength after immersion in a hydrocarbon-based refrigerant is preferably 3.0 MPa or greater. The adhesive strength before immersion in a hydrocarbon-based refrigerant shown in Table 3 corresponds to the adhesive strength at the interface (1500) of the sealant as shown in Figure 1 or the interface of the sealant removed from the capacitor before immersion in a hydrocarbon-based refrigerant. The following describes the results of evaluation of a capacitor using a sample in which the adhesive strength of the laminated rubber interface (1500) after immersion in a refrigerant is at least 3.0 MPa.

[0116] (Method of manufacturing the capacitor) After etching the surface of an aluminum foil, a lead terminal having a round bar portion was electrically connected to an anode foil on which a dielectric layer was formed by chemical conversion treatment. Also, a lead terminal having a round bar portion was electrically connected to a cathode foil made of aluminum foil. The anode foil and cathode foil with the connected lead terminals were wound with a separator interposed therebetween to manufacture a capacitor element having lead terminals.

[0117] The fabricated capacitor element was immersed in a chemical conversion solution, and a voltage was applied to perform a chemical conversion treatment. The capacitor element after the chemical conversion treatment was impregnated with an electrolyte solution containing ethylene glycol and water. The capacitor element was then inserted into the lead terminal insertion hole of the sealing body. After the capacitor element was housed in the exterior case, the open end of the aluminum case was sealed with a sealing body. The sealing body used had a rubber layer thickness of 5 mm (NBR 2 mm, IIR 3 mm). This sealing body was fitted into the end of the exterior case, and the open end of the aluminum case was sealed by crimping, including horizontal crimping, as shown in Figures 2(a) and 2(b) and Figure 7 (L2 = 2.5 mm). (Capacitor size: 12.5φ, height: 33 mm)

[0118] (Preparation of sealing body samples for capacitor evaluation); Experimental levels 2-1 to 2-8 Preparation of NBR sheet 100 parts by weight of acrylonitrile butadiene rubber, 50 parts by weight of carbon black, 100 parts by weight of inorganic filler, 1 part by weight of stearic acid, and 12 parts by weight of alkylphenol-formaldehyde resin were kneaded to obtain an NBR sheet with a thickness of 2 mm. Preparation of IIR sheet A 3 mm thick IIR sheet was obtained in the same manner as in the preparation of the NBR sheet, except that the ingredients were changed to 100 parts by weight of butyl rubber and 12 parts by weight of alkylphenol-formaldehyde resin. The obtained NBR sheet and butyl sheet were stacked, and the pressure (50 kg / cm) was applied in a mold. ２ ) was added, and the layers were vulcanized and bonded for 4 hours at 190±10° C. Thereafter, a product portion was punched out from the molded rubber sheet to prepare a sealing body.

[0119] (Preparation of sealing body samples for capacitor evaluation): Experimental level 3-1 Preparation of IIR sheet A sealing body was prepared in the same manner as in the preparation of experimental levels 2-1 to 2-8, except that the butyl rubber was changed to 100 parts by weight and the alkylphenol-formaldehyde resin was changed to 14 parts by weight.

[0120] (Regarding the transverse crimping of the outer and inner elastic members) The length ratio of the "outer elastic member (NBR layer) to the inner elastic member (IIR layer)" within the transverse crimping length L2 was calculated from the cross section of the capacitor using a microscope, as shown in Figure 7. The capacitors prepared above were immersed in a hydrocarbon refrigerant (heavy distillate oil) at 105°C, and the weight change (δwt%) was measured before and after immersion in the hydrocarbon refrigerant for 2000 hours (sample number N = 4). The results are shown in Table 4 below.

[0121] [Experiment on the preferred ratio of outer and inner elastic members for horizontal crimping]

[0122] Explanation of symbols in Table 4 δwt: Within 1%: ◎, Less than 5%: 〇, 5-10%: △

[0123] Here, experimental levels 2-1 and 2-8 shown in Table 4 above are comparative examples. Experimental levels 2-1 to 2-8 are experiments conducted using the sample of experimental level 2 shown in Table 3 above. Experimental level 3-1 is an experiment conducted using the sample of experimental level 3 shown in Table 3 above. Particularly preferred embodiments within δwt 1% shown by double circles on the right side of Table 4 above are experimental levels 2-2, 2-3, 2-4, and 3 in Table 4.

[0124] From the results of Table 4 above, it can be seen that: 1) the ratio of outer elastic member to inner elastic member within L2 is particularly preferably 20:80 to 80:20, as shown in the black box in Table 4 (experimental levels 2-2 to 2-7); 2) from the viewpoint of the rate of change of δwt, the ratio of outer elastic member to inner elastic member within L2 is even more preferably 20:80 to 40:60 (experimental levels 2-2 to 2-4); and 3) experimental level 3 showed an adhesive strength of 7.1 MPa before immersion in a hydrocarbon refrigerant, a result similar to that of experimental level 2-3. Therefore, from the viewpoint of the rate of change of δwt in 2) above, it can be said that it is preferable that the width of the inner elastic member that is laterally crimped is longer than the width of the outer elastic member that is laterally crimped.

[0125] The method for adjusting the experimental level has been specifically explained using examples, but the present disclosure is not limited to the specific descriptions of the above examples as long as it is within the scope of the gist and invention.

[0126] The capacitors, electronic components, their sealing bodies, rubber members, and their manufacturing and molding methods, structures, configurations, etc. described above are not limited to the specific explanations that exemplify the numerical values, structures, configurations, procedures, etc. in the examples, but are broadly applicable to any electronic components, etc., and adjustments and changes can be made by appropriately changing and arranging the structures, materials, process contents, order, procedures, etc., as is obvious to those skilled in the art and within the scope of the technical concept of the present invention.

[0127] The present invention is suitable for various capacitors such as aluminum electrolytic capacitors, various other electronic components sealed with rubber bodies, and electronic components in which rubber is exposed to the outside.

[0128] 1000: Sealing body, 1100: Nitrile rubber (NBR) layer, 1150: Lead terminal insertion hole, 1200: Butyl rubber (IIR) layer, 1300: Case, 1400: Capacitor element, 2100: Lead terminal, 2110: Round bar portion, 1500: Interface, L2: Lateral crimping width, L2-1: Outer elastic member within the horizontal crimping width, Horizontal crimping width, L2-2: Inner elastic member within the horizontal crimping width.

Claims

1. A capacitor that can be used for immersion cooling with a hydrocarbon-based refrigerant, comprising: a capacitor element having lead terminals; an electrolyte; a case that houses the capacitor element and the electrolyte; and a sealing body that seals the opening of the case, wherein the sealing body comprises an inner elastic member that is disposed inside the case and at least a portion of which contacts the electrolyte, and an outer elastic member that is at least a portion of which is exposed from the case, and has a structure in which different elastic members are laminated together, wherein the inner elastic member is one or more types selected from the group consisting of butyl rubber and ethylene propylene rubber, and the outer elastic member has a Hansen solubility parameter distance with the hydrocarbon-based refrigerant of 8.0 or more.

2. A capacitor usable for liquid immersion cooling according to claim 1, characterized in that the outer elastic member is one or more selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber.

3. A capacitor usable for liquid immersion cooling according to claim 1, characterized in that the inner elastic member and the outer elastic member are formed by vulcanization bonding.

4. A capacitor usable for liquid immersion cooling according to claim 3, characterized in that the adhesive strength of the vulcanization bonding before immersion in a hydrocarbon refrigerant is 6.0 MPa or more.

5. A capacitor usable for liquid immersion cooling according to claim 3, characterized in that the adhesive strength of the vulcanization bonding after immersion in a hydrocarbon refrigerant is 3.0 MPa or more.

6. A capacitor usable for liquid immersion cooling according to claim 1, characterized in that at least a portion of the inner elastic member and at least a portion of the outer elastic member are laterally crimped together with the case.

7. A capacitor usable for liquid immersion cooling according to claim 6, wherein the sealing body has a lead terminal insertion hole penetrating the outer elastic member and the inner elastic member, the lead terminal has a round bar portion that inserts into the lead terminal insertion hole, and at least the lead terminal insertion hole of the outer elastic member and the round bar portion abut each other so as to achieve a sealed state that prevents the hydrocarbon-based refrigerant from entering the inside of the capacitor usable for liquid immersion cooling from the outside via the interface between the lead terminal insertion hole of the outer elastic member and the round bar portion.

8. A capacitor usable for liquid immersion cooling according to claim 7, characterized in that at least a part of the round bar portion is located within the width of the outer elastic member where the outer elastic member is laterally crimped.

9. A capacitor usable for liquid immersion cooling according to claim 6, characterized in that the width of the lateral crimping of the inner elastic member is longer than the width of the lateral crimping of the outer elastic member.

10. A method for manufacturing a capacitor usable for liquid immersion cooling, comprising: a capacitor element having lead terminals, an electrolyte, a case accommodating the capacitor element and the electrolyte, and a sealing body sealing an opening of the case, the method comprising the steps of: molding the sealing body by laminating an inner elastic member and an outer elastic member; sealing the opening of the case accommodating the capacitor element and the electrolyte using the molded sealing body; and laterally crimping at least a portion of the inner elastic member and at least a portion of the outer elastic member from the outside of the case, wherein at least a surface of the inner elastic member that comes into contact with the electrolyte is made of one or more rubbers selected from the group consisting of butyl rubber and ethylene propylene rubber, and at least a surface of the outer elastic member that comes into contact with a hydrocarbon-based refrigerant has a Hansen solubility parameter distance with the hydrocarbon-based refrigerant of 8.0 or more.

11. A method for manufacturing a capacitor usable for liquid immersion cooling according to claim 10, wherein the step of molding the sealing body comprises laminating the inner elastic member and the outer elastic member and simultaneously molding them by applying temperature and pressure to vulcanize and bond the inner elastic member and the outer elastic member.

12. A method for manufacturing a capacitor usable for liquid immersion cooling as defined in claim 10 or 11, wherein the sealing body has lead terminal insertion holes penetrating the outer elastic member and the inner elastic member, and the lead terminals have round bar portions that insert into the lead terminal insertion holes, and in the step of sealing the opening of the case containing the capacitor element and the electrolyte using the molded sealing body, at least the lead terminal insertion holes of the outer elastic member and the round bar portions are abutted against each other so as to achieve a sealed state in which the hydrocarbon-based refrigerant does not enter from the outside to the inside of the capacitor usable for liquid immersion cooling through the interface between the lead terminal insertion holes of the outer elastic member and the round bar portions.

13. A method for manufacturing a capacitor usable for liquid immersion cooling as described in claim 12, characterized in that in the lateral crimping step, at least a part of the round bar portion is located within the width of the lateral crimping of the outer elastic member.

14. A method for manufacturing a capacitor usable for liquid immersion cooling as described in claim 10 or 11, characterized in that in the lateral crimping step, the width of the lateral crimping of the inner elastic member is longer than the width of the lateral crimping of the outer elastic member.

15. A method for manufacturing a capacitor usable for liquid immersion cooling according to claim 10 or 11, characterized in that the outer elastic member is one or more selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber.

16. A liquid immersion cooling method in which a capacitor usable for liquid immersion cooling according to claim 1 is mounted on a metal frame or an electronic circuit board, and the metal frame on which the capacitor is mounted or the electronic circuit board on which the capacitor is mounted is partially or entirely immersed in the hydrocarbon-based refrigerant cooling liquid.

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