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

Abstract

To provide a highly reliable, long-life capacitor that can be used for immersion cooling and a manufacturing method thereof, which reduce the occurrence of unexpected deterioration.SOLUTION: An aluminum electrolytic capacitor 2000 used for immersion cooling includes a capacitor element 1400, an electrolyte, an aluminum case 1300, and a sealing body 1000 that seals the opening of the aluminum case. The sealing body 1000 is disposed inside an aluminum case 1300 and has a laminated structure of different elastic members, including an inner elastic member that is partially in contact with the electrolyte and an outer elastic member that is partially exposed from the case. The inner elastic member is at least one selected from the group consisting of butyl rubber 1200 and ethylene propylene rubber, and the outer elastic member has a Hansen solubility parameter distance of 8.0 or more with a hydrocarbon-based refrigerant such as nitrile rubber 1100.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[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 ever-increasing tendency for the amount of heat generated by circuit boards containing electronic components, and there has been an increase in the number of applications and situations where immersion cooling, which provides more powerful cooling than air or water cooling, is required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-169554 Summary of the Invention [Problem to be solved by the invention]

[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 body 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 body 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 sealants for aluminum electrolytic capacitors, tend to swell easily in hydrocarbon refrigerants, raising concerns that this could cause deterioration of the capacitor's 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. [Means for solving the problem]

[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. 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. The sealing body has a structure in which different elastic members are laminated, and 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 includes 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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a sealing body of the present invention that seals the opening of a capacitor housing case, as viewed obliquely from above and to the side. FIG. [Figure 2] 1A and 1B are diagrams illustrating the crimping characteristics of a capacitor, typically an aluminum electrolytic capacitor; FIG. 1A is a conceptual diagram illustrating the state in which a sealing body housed in a case, typically made of aluminum, is sealed by horizontal and vertical crimping; and FIG. 1B is a diagram illustrating the horizontal crimping width L2 and the relative arrangement and positional relationship between the nitrile rubber layer and the butyl rubber layer of the sealing body. [Figure 3] FIG. 2 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). [Figure 4] FIG. 10 is a cross-sectional view illustrating a conceptual configuration of an aluminum electrolytic capacitor according to another embodiment of the present invention. [Figure 5] 10A and 10B are diagrams illustrating an example of a structure in which the characteristics and lifespan of a capacitor are deteriorated when the width of the lateral crimping on the aluminum case is limited to the butyl rubber layer. [Figure 6] FIG. 1 is an external view showing a dumbbell-shaped No. 3 specimen used in the experiment. [Figure 7] 10 is a diagram illustrating the arrangement of the outer elastic member and the inner elastic member within the horizontal crimping width L2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[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] For this reason, if the sealing body were constructed using a single type of rubber plug, 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 simultaneous molding using vulcanization bonding under the application of 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 diagonally above. As shown in FIG. 1, the sealing member 1000 has a laminated double-layer structure comprising 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 an electrolyte and is typically resistant to the electrolyte solution, underneath. 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 can be inserted, passing through the nitrile rubber layer and the butyl rubber layer. 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 limited to these. 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 solution, etc., is highly durable and reliable against the electrolyte solution 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, 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] (About vulcanization adhesion 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, laminating the inner and outer elastic members and simultaneously molding them under heat and pressure to vulcanize and bond them is a preferred technique for firmly bonding the interface between the outer and inner elastic members. For example, rubber is molded using compression molding or injection molding, but bonding two layers of rubber can be achieved by applying heat and pressure in a mold to bond them together using the vulcanizing agent contained in each layer of rubber.

[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 characteristics of a capacitor, typically an aluminum electrolytic capacitor. FIG. 2A is a conceptual diagram illustrating the state in which a sealing body 1000 housed in a case 1300, typically 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 and the relative arrangement and positional relationship between the nitrile rubber layer 1100 and the butyl rubber layer 1200 of the sealing body 1000.

[0021] 2(a), all necessary components 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 press simultaneously to crimp and seal. 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 (joint 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] For example, as shown in Figure 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, allowing the refrigerant to penetrate into the capacitor from the outside, causing swelling and deterioration of the butyl rubber layer 3, which may result in deterioration of the capacitor's characteristics and shortening of its lifespan.In addition, if this condition occurs, there is a concern that the electrolyte inside the capacitor may leak to the outside.

[0025] 2(b), the arrangement and positional relationship between the transverse crimp width L2 and the lead terminal 2100 will be 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. The transverse crimp width L2 is the area where the sealing body 1000 is crimped from the outside and compressed and pressed inward. Therefore, it is preferable that the round bar portion 2110 is compressed and pressed by the sealing body around it due to this pressure, resulting in 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 is 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 part) The round bar portion 2110 of the lead terminal shown in FIGS. 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 adhere tightly to the sealing body.

[0027] 3A and 3B are diagrams illustrating the relationship between the sealing body 1000 and the rod 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 rod portion 2110 of the lead terminal 2100 is kept in tight contact with the sealing body 1000, with all or part of the rod portion 2110 being compressed to the extent that liquid or the like does not leak or intrude through the peripheral interface of the rod portion 2110. In terms of sealing, the sealing body 1000 functions like a packing, ensuring airtightness and liquid-tightness at the peripheral interface of the rod 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, tightly contacts with the hole 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 may swell and deteriorate, potentially compromising the airtightness and liquid-tightness of the inside of the capacitor.

[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 to ensure airtightness and liquid tightness. A through-hole or notch of a predetermined diameter or shape may be provided in advance at the 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 refrigerant heated by the circuit board vaporizes, and the vaporized refrigerant is cooled by cooling water, turning into droplets and returning to its original liquid form. In this case, the refrigerant 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] (Other embodiments) Fig. 4 is a diagram illustrating a cross-sectional conceptual diagram 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 is cooled. Horizontal crimp marks 2510 and 2520 are formed circumferentially at two locations on the aluminum case 2500 of the capacitor 3000. The horizontal crimp marks 2510 press against the nitrile rubber (NBR) layer 1100 by crimping pressure at that location, and the horizontal crimp marks 2520 press against the butyl rubber (IIR) layer 1200 by crimping pressure at that location. In this structure, between the horizontal crimp marks 2510 in the nitrile rubber layer and the horizontal crimp marks 2520 in the butyl rubber layer, there are regions where the aluminum case and the rubber are insufficiently in contact with each other and regions where the aluminum case and the rubber are not insufficiently in contact. In the regions where the aluminum case and the rubber are insufficiently in contact, the stress exerted by the aluminum case on the rubber due to the horizontal crimping is less than in the regions where the aluminum case and the rubber are insufficiently in contact.

[0035] The respective transverse crimping of each rubber layer ensures that each rubber layer of sealing body 1000 exhibits a tightly closed, tightly closed, and sealing function. This reliably prevents both the intrusion of liquids from outside the capacitor and leakage from inside. Transverse crimping marks 2510 prevent liquids from entering from the outside from reaching butyl rubber (IIR) layer 1200, while transverse crimping marks 2520 more reliably prevent 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 paired lead terminals 2100, including their round bar portions, and their relative positional relationships with other components, can adopt the same configurations and details already described above.

[0036] In the present invention, the sealing body has a double layered 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 fabricated 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 that comes into contact with the electrolyte) of the sealing body are each made of elastic materials 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 interface and raising concerns that the deformation of the rubber would weaken the seal.

[0039] (Supplementary explanation regarding the relationship between the immersion cooling refrigerant and the capacitor seal) 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 branched hydrocarbons or straight-chain hydrocarbons are preferably selected.

[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] A capacitor usable for immersion cooling in a coolant, wherein the coolant is a hydrocarbon refrigerant, the capacitor seal 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 capacitors to immersion cooling using coolants such as hydrocarbons, the seal must be resistant to swelling caused by the coolant. The Hansen Solubility Parameter (HSP) is used as a criterion for selecting the seal material, and the seal swelling can be suppressed by ensuring that the rubber material placed in the seal area that comes into contact with the coolant has an HSP distance of 8.0 or greater.

[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 its compatibility with substance B.

[0045] Furthermore, 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). 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 MPa1 / 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, 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 to substance A.

[0046] In the formula of HSP distance (Ra) = {4 × (δD1 - δD2)2 + (δP1 - δP2)2 + (δH1 - δH2)2}1 / 2, δD1, δP1, and δH1 are δD, δP, and δH, respectively, of substance A. In the above formula, δD2, δP2, and δH2 are δD, δP, and δH, respectively, 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 for 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] Note that "HSP distance between the outer elastic member and the coolant" refers to 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 rubbers, or the HSP distance between the coolant and the mixture when the coolant is a mixture of two or more 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 believed that there is no problem if the rubber component that forms the outer elastic member contains rubber whose HSP distance from the coolant is less than the above lower limit, as long as the HSP distance from 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 forms 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 it 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 made 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 whose main component is acrylic ester. "Mainly composed of acrylic ester" means that the acrylic rubber contains 50% or more acrylic ester units by weight. 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. Examples of crosslinkable monomers include monomers with carboxyl groups, epoxy groups, and hydroxyl groups, as well as diene-based monomers.

[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, and vinylidene fluoride. 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 (-SS-) 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), copolymer of epichlorohydrin and ethylene oxide (ECO), copolymer of epichlorohydrin and allyl glycidyl ether (GCO), and copolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether (GECO).

[0061] The rubber component that forms 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 that forms 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 from 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 from 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 donors such as sulfur, 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. That is, when the rubber component for the outer elastic member contains a filler, preferred ranges for the content of the filler per 100 parts by weight of the rubber component for the outer elastic member are typically 10 parts by weight to 250 parts by weight, 20 parts by weight to 200 parts by weight, and 30 parts by weight to 180 parts by weight.

[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, as 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 becomes 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 becomes 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 to 20 parts by weight, 0.3 to 10 parts by weight, or 0.5 to 5 parts by weight.

[0069] (Preferable upper and lower limits for HSP of 8.0 or higher) The Hansen Solubility Parameter distance (HSP) between the outer elastic member and the hydrocarbon-based refrigerant is preferably 8.0 or greater. Based on the criterion that immersion in a coolant reduces changes in the rubber member, it is even more preferable that the upper limit of the HSP is 25.0 and the lower limit is 8.6. Furthermore, the hardness change rate is preferably 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 using the method described below, and the results are shown in Table 1. In Table 1 below, the upper limit of 25.0 and the lower limit of 8.6 of the HSP are circled.

[0070] [Evaluation of hardness change due to immersion] (immersion test) Three dumbbell-shaped test pieces were immersed in the test refrigerant contained in a test tube. The test tube was heated in an oven set to a temperature of 85°C for 168 hours. The test tube was removed from the oven and left 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) The hardness of the three dumbbell-shaped test specimens was measured before the immersion test using a durometer (Teloc Corporation, "GX-01A"; Type A) in accordance with JIS K 6253-3:2012 "Vulcanized rubber and thermoplastic rubber - Determination of hardness - Part 3: Durometer hardness" (established March 21, 2012). The median of the measured values ​​was calculated as the hardness of the dumbbell-shaped test specimens before the immersion test. The hardness of the dumbbell-shaped test specimens after the immersion test was calculated in the same manner. The hardness change rate of the dumbbell-shaped test specimens was calculated by applying these calculation results to the following [Equation 1]. The results are shown in Table 1.

[0072]

number

[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 with 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 Fischer-Tropsch distillate heavy oil (a mixture of branched and linear hydrocarbons with carbon numbers between 18 and 50) which is a hydrocarbon refrigerant was calculated using the HSP analysis software "HSPiP (Ver.5.4.05)". The calculated HSP values ​​of acrylonitrile butadiene rubber and hydrocarbon refrigerant, as well as the HSP distance between acrylonitrile butadiene rubber and hydrocarbon refrigerant calculated 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 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.

[0077] Example 3 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 vinylidene fluoride-hexafluoropropylene copolymer.

[0078] 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.

[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 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 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.

[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 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.

[0083] Comparative Example 2 Dumbbell-shaped test pieces (Type 3) were 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] In the same manner as in Example 1, the HSP and HSP distance were calculated, and the hardness change was evaluated. 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 2 mm thick sheet. This sheet was punched out into a dumbbell shape to prepare dumbbell-shaped test pieces (size 3).

[0086] 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.

[0087] Example 6 A dumbbell-shaped test piece (No. 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 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.

[0089] Example 7 A dumbbell-shaped test piece (No. 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 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.

[0091] Example 8 A dumbbell-shaped test piece (No. 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 (No. 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 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.

[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 out into a dumbbell shape to prepare a dumbbell-shaped test piece (size 3).

[0095] 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.

[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 2 mm thick sheet. This sheet was punched out into a dumbbell shape to prepare dumbbell-shaped test pieces (size 3).

[0097] 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.

[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)), a hydrocarbon-based refrigerant.

[0099] Moreover, calculation of HSP and HSP distance, and evaluation of hardness change were performed 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 a hydrocarbon-based refrigerant, poly-α-olefin (poly(1-decene)), was used as the test refrigerant.

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

[0102] [Table 1]

[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 with 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] (Vulcanization adhesion of elastic materials) When the inner elastic member and the outer elastic member are immersed in a liquid immersion refrigerant, a decrease in adhesive strength at the interface (1500) where the inner elastic member and the outer elastic member are joined is confirmed, and the inventors have therefore confirmed that there is an optimal adhesive strength for laminated rubber to be 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, "Vulcanized and thermoplastic rubber - Determination of tensile properties." 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 (N=3 for each sample).

[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 an NBR sheet having a thickness of 2 mm. Preparing the IIR sheet An IIR sheet having a thickness of 2 mm was obtained in the same manner as in the preparation of the NBR sheet, except that the amount of butyl rubber was changed to 100 parts by weight and the amount of alkylphenol-formaldehyde resin was changed to 8 parts by weight. Prepare the NBR sheet and butyl sheet (200 x 50 x 2.0 mm each), place the NBR sheet and butyl sheet next to the fabric in a mold, and press 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 (Type 3) 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 (Type 3) 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) EPDM sheet preparation A dumbbell-shaped test piece (Type 3) was prepared in the same manner as in Experimental Level 1, except that the materials were changed to 100 parts by weight of ethylene propylene rubber (EPDM) and 5 parts by weight of dicumyl peroxide.

[0109] Preparation method for experimental level 5 (F-EPDM) F sheet preparation 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. EPDM sheet preparation An EPDM sheet having a thickness of 2 mm was obtained in the same manner as in the EPDM sheet of experimental level 3. The F sheet and EPDM sheet (200 x 50 x 2.0 mm each) were prepared, and the F sheet and EPDM sheet were placed side by side in a mold. They were then 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 for 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 having a thickness of 2 mm. Preparing the IIR sheet A 2 mm thick IIR sheet was obtained in the same manner as the preparation of the IIR (35) NBR (65) sheet, except that butyl rubber was changed to 100 parts by weight. The IIR (35) NBR (65) sheet and IIR sheet (each 200 × 50 × 2.0 mm) were prepared, and the IIR (35) NBR (65) sheet and IIR 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).

[0111] Preparation method for experimental level 7 (IIR(65)NBR(35)-IIR) Preparation of IIR(65)NBR(35) sheet Dumbbell-shaped test specimens (Type 3) were prepared in the same manner as in 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 for changes in adhesive strength of laminated rubber] [Table 2]

[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 immersion in the refrigerant 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 immersion evaluation test, it is possible that the refrigerant will reach the rubber interface over the course of the test time. If the strength of the rubber interface is insufficient, the sealing performance will be lost, raising concerns that the refrigerant will 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] [Table 3]

[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 rubber component interface (1500) 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 rubber, and between the round bar and rubber component. Furthermore, the adhesive strength after immersion in a hydrocarbon-based refrigerant is preferably 3.0 MPa or higher. The adhesive strength before immersion in a hydrocarbon-based refrigerant shown in Table 3 corresponds to the adhesive strength of the interface (1500) of the sealing body as shown in Figure 1 or the interface of the sealing body 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 was at least 3.0 MPa.

[0116] (About the manufacturing method of the capacitor) The surface of the aluminum foil was etched, and then chemically treated to form a dielectric layer. A lead terminal with a round bar portion was electrically connected to the anode foil. A lead terminal with a round bar portion was also electrically connected to the 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 produce a capacitor element with lead terminals.

[0117] The produced 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 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 outer case, the open end of the aluminum case was sealed with a sealing body. The sealing body used a rubber layer with a thickness of 5 mm (NBR 2 mm, IIR 3 mm). This sealing body was fitted onto the end of the outer case, and the open end of the aluminum case was sealed by crimping, including horizontal crimping, as shown in Figures 2(a) and (b) and Figure 7 (L2 = 2.5 mm). (Capacitor size: 12.5φ, height: 33 mm)

[0118] (Sample preparation of sealing body for capacitor evaluation); Experimental levels 2-1 to 2-8 ·Preparing the 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 having a thickness of 2 mm. Preparing the IIR sheet An IIR sheet having a thickness of 3 mm was obtained in the same manner as in the preparation of the NBR sheet, except that the amount of butyl rubber was changed to 100 parts by weight and the amount of alkylphenol-formaldehyde resin was changed to 12 parts by weight. The obtained NBR sheet and butyl sheet were stacked and compressed in a mold under pressure (50 kg / cm 2 ) was added, and each layer was vulcanized and bonded for 4 hours at 190±10°C. After that, the product part was punched out from the molded rubber sheet to prepare a sealing body.

[0119] (Sample production of sealing body for capacitor evaluation); Experimental level 3-1 Preparing the 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 amounts of butyl rubber and alkylphenol-formaldehyde resin were changed to 100 parts by weight and 14 parts by weight, respectively.

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

[0121] [Experiment on the desirable ratio of outer and inner elastic members for horizontal crimping] [Table 4]

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

[0124] From the results of [Table 4] above, 1) The ratio of the outer elastic member to the 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, a more preferable ratio of the outer elastic member / inner elastic member within L2 is 20:80 to 40:60 (experimental levels 2-2 to 2-4). 3) It was confirmed that the adhesive strength before immersion in hydrocarbon refrigerant in experimental level 3 was 7.1 MPa, which was the same result as experimental levels 2-3. Therefore, particularly 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] Although the method for adjusting the experimental level has been specifically explained using examples, the present disclosure is not limited to the specific description 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. [Industrial Applicability]

[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. [Explanation of symbols]

[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··Horizontal crimping width, L2-1··Outer elastic member within horizontal crimping width, horizontal crimping width, L2-2··Inner elastic member within horizontal crimping width.

Claims

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

2. 2. The capacitor according to claim 1, which can be used for liquid immersion cooling, The outer elastic member is at least one selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber. A capacitor that can be used for liquid immersion cooling, characterized by:

3. 2. The capacitor according to claim 1, which can be used for liquid immersion cooling, The inner elastic member and the outer elastic member are formed by vulcanization bonding. A capacitor that can be used for liquid immersion cooling, characterized by:

4. The capacitor that can be used for liquid immersion cooling according to claim 3, A capacitor that can be used for immersion cooling, wherein the adhesive strength in the vulcanization bonding before immersion in a hydrocarbon-based refrigerant is 6.0 MPa or more.

5. The capacitor that can be used for liquid immersion cooling according to claim 3, A capacitor that can be used for immersion cooling, characterized in that the adhesive strength of the vulcanization adhesion after immersion in a hydrocarbon-based refrigerant is 3.0 MPa or more.

6. 2. The capacitor according to claim 1, which can be used for liquid immersion cooling, 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. A capacitor that can be used for liquid immersion cooling, characterized by:

7. A capacitor that can be used for liquid immersion cooling according to claim 6, the sealing body has a lead terminal insertion hole that penetrates the outer elastic member and the inner elastic member, the lead terminal has a round bar portion that is inserted through the lead terminal insertion hole, At least the lead terminal insertion holes of the outer elastic member and the round bar portion abut against each other so as to form a sealed state in which the hydrocarbon-based refrigerant does not infiltrate from the outside to the inside of the capacitor that can be used for liquid immersion cooling through the interface between the lead terminal insertion holes of the outer elastic member and the round bar portion. A capacitor that can be used for liquid immersion cooling, characterized by:

8. The capacitor that can be used for liquid immersion cooling according to claim 7, At least a part of the round bar portion is located within the width of the transversely crimped outer elastic member. A capacitor that can be used for liquid immersion cooling, characterized by:

9. 7. The capacitor that can be used for liquid immersion cooling according to claim 6, The width of the inner elastic member that is laterally crimped is greater than the width of the outer elastic member that is laterally crimped. A capacitor that can be used for liquid immersion cooling, characterized by:

10. A method for manufacturing a capacitor that can be used for liquid immersion cooling, the method 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 an opening of the case, the method comprising: a step of molding the sealing body by laminating an inner elastic member and an outer elastic member; a step of sealing the opening of the case containing the capacitor element and the electrolyte with the molded sealing body; and a step of 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, 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, The outer elastic member has a Hansen solubility parameter distance of 8.0 or more with respect to at least the surface that comes into contact with the hydrocarbon-based refrigerant. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

11. 11. The method for manufacturing a capacitor that can be used for liquid immersion cooling according to claim 10, The step of molding the sealing body includes 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. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

12. The method for manufacturing a capacitor that can be used for liquid immersion cooling according to claim 10 or 11, the sealing body has a lead terminal insertion hole that penetrates the outer elastic member and the inner elastic member, the lead terminal has a round bar portion that is inserted through the lead terminal insertion hole, a step of sealing an opening of the case containing the capacitor element and the electrolyte with the molded sealing body, At least the lead terminal insertion holes of the outer elastic member are brought into contact with the round bar portion so as to achieve a sealed state in which the hydrocarbon-based refrigerant does not infiltrate from the outside to the inside of the capacitor that can be used for liquid immersion cooling through the interface between the lead terminal insertion holes of the outer elastic member and the round bar portion. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

13. 13. The method for manufacturing a capacitor that can be used for liquid immersion cooling according to claim 12, In the transverse crimping step, 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. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

14. The method for manufacturing a capacitor that can be used for liquid immersion cooling according to claim 10 or 11, In the transverse crimping step, The width of the inner elastic member that is laterally crimped is greater than the width of the outer elastic member that is laterally crimped. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

15. The method for manufacturing a capacitor that can be used for liquid immersion cooling according to claim 10 or 11, The outer elastic member is at least one selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber. A method for manufacturing a capacitor that can be used for liquid immersion cooling.

16. The capacitor usable for liquid immersion cooling according to claim 1 is mounted on a metal frame or an electronic circuit board, An immersion cooling method is carried out by immersing a part or the whole of a metal frame on which the capacitor is mounted or an electronic circuit board on which the capacitor is mounted in a cooling liquid of the hydrocarbon-based refrigerant.

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