Fluororubber for electrolytic capacitor sealing

Abstract

To provide a fluororubber for electrolytic capacitor sealing bodies that exhibits excellent compression set characteristics at high temperatures, as well as low permeability to electrolyte components such as γ-butyrolactone contained in the electrolyte of electrolytic capacitors, and excellent swelling resistance. [Solution] A fluororubber for electrolytic capacitor sealing is provided, wherein the vinylidene fluoride unit content is 48 mol% or less relative to the total monomer units, and the hydrogen content is 1.00 mass% or less.

Description

Technical Field

[0001] The present disclosure relates to a fluororubber for an electrolytic capacitor sealing body and a fluororubber.

Background Art

[0002] Patent Document 1 describes a sealing body for an electrolytic capacitor, wherein a resin film is attached to the upper surface and / or the lower surface of a perfluoropolyether-based fluororubber obtained by crosslinking a fluorine-containing rubber composition having a perfluoropolyether unit in the main chain as a base polymer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a fluororubber for an electrolytic capacitor sealing body that is excellent in compression set characteristics at high temperatures and has low permeability and swelling resistance to electrolyte components such as γ-butyrolactone contained in the electrolyte of an electrolytic capacitor. Another object of the present disclosure is to provide a novel fluororubber.

Means for Solving the Problems

[0005] According to the present disclosure, there is provided a fluororubber for an electrolytic capacitor sealing body, wherein the content of vinylidene fluoride units is 48 mol% or less based on all monomer units, and the hydrogen content is 1.00 mass% or less.

Effects of the Invention

[0006] According to this disclosure, it is possible to provide a fluororubber for electrolytic capacitor sealing bodies that exhibits excellent compression set characteristics at high temperatures, as well as low permeability to electrolyte components such as γ-butyrolactone contained in the electrolyte of the electrolytic capacitor and excellent swelling resistance. Furthermore, this disclosure makes it possible to provide novel fluororubber. [Modes for carrying out the invention]

[0007] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0008] Generally, electrolytic capacitors are constructed by impregnating a capacitor element, which consists of an aluminum anode foil, a cathode foil, and an insulating separator wound around it, with an electrolyte solution, housing it in a cylindrical cup-shaped aluminum case, and sealing the opening of this case with a sealing element. In such electrolytic capacitors, the lead wires drawn from the capacitor element are led to the outside through through holes in the sealing element, and the outer case is crimped in this state to maintain the seal. To maintain the seal between the outer case, lead wires, and the sealing element, rubber is generally used for the sealing element.

[0009] As the applications of electrolytic capacitors expand, there is a growing demand for electrolytic capacitors that can withstand long-term use even in high-temperature environments, such as near the internal combustion engines of automobiles. If the electrolyte sealed inside an electrolytic capacitor leaks out or evaporates and permeates the sealing material, the lifespan of the electrolytic capacitor is shortened. Therefore, a sealing material that can prevent the reduction of electrolyte even in high-temperature environments is necessary.

[0010] Conventional electrolytic capacitor seals have used isobutylene isoprene rubber (butyl rubber). Butyl rubber seals exhibit excellent low permeability to the electrolyte of electrolytic capacitors and also have excellent compression set characteristics, as long as they are used at low temperatures. However, butyl rubber seals have the problem that their sealing performance deteriorates at high temperatures, making it difficult to adequately suppress electrolyte leakage and permeation.

[0011] Patent Document 1 proposes using perfluoropolyether-based fluororubber, which has good heat resistance, as the elastic rubber material that constitutes the sealing body of an electrolytic capacitor. However, Patent Document 1 also states that perfluoropolyether-based fluororubber has the problem of having greater gas permeability than butyl rubber, and that the amount of ethylene glycol permeation can be significantly reduced by laminating a resin film onto the perfluoropolyether-based fluororubber.

[0012] Furthermore, Patent Document 1 states that fluororubber is known as a heat-resistant rubber, and that "although fluororubber has low gas permeability, general-purpose products lose their rubber elasticity at low temperatures below -20°C, and therefore may not be able to maintain sealing properties." However, our investigations have revealed that general-purpose fluororubber exhibits excellent low permeability to ethylene glycol contained in the electrolyte of electrolytic capacitors, but does not exhibit sufficiently low permeability to other substances used, such as γ-butyrolactone, ethylene glycol monomethyl ether, and N-methylformamide. A decrease in γ-butyrolactone and other substances in the electrolyte significantly reduces the lifespan of the electrolytic capacitor.

[0013] Therefore, there is a need for a fluororubber that can produce an electrolytic capacitor sealing body that exhibits excellent compression set characteristics at high temperatures, good low permeability to γ-butyrolactone and other substances contained in the electrolyte of an electrolytic capacitor without the need for means such as attaching a resin film, and also good swelling resistance to γ-butyrolactone and other substances.

[0014] After diligently investigating means to solve the above problems, it was discovered that the above problems could be successfully solved by appropriately adjusting the content of vinylidene fluoride units in the fluororubber and the hydrogen content of the fluororubber.

[0015] In other words, the present disclosure provides a fluororubber for forming a sealing body used in the sealing of an electrolytic capacitor, wherein the vinylidene fluoride unit content is 48 mol% or less relative to the total monomer units, and the hydrogen content is 1.00 mass% or less.

[0016] The composition of the fluororubber in this disclosure will be described in more detail.

[0017] (Fluororubber) In this disclosure, fluororubber is an amorphous fluoropolymer. "Amorphous" means that the magnitude of the melting peak (ΔH) observed in differential scanning calorimetry (DSC) (heating rate 20°C / min) or differential thermal analysis (DTA) (heating rate 20°C / min) of the fluoropolymer is 4.5 J / g or less. Fluororubber exhibits elastomeric properties by crosslinking. Elastomer properties refer to the ability of a polymer to be stretched and to retain its original length when the force required to stretch the polymer is no longer applied.

[0018] If fluororesin is used instead of fluororubber as the sealing material for the sealing of an electrolytic capacitor, the sealing performance of the sealing material will be inferior, and it will not be possible to sufficiently suppress the permeation of the electrolyte inside the electrolytic capacitor.

[0019] The fluorine content of fluororubber is preferably 61 to 73% by mass, more preferably 63% by mass or more, even more preferably 65% ​​by mass or more, still more preferably 67% by mass or more, and particularly preferably 69% by mass or more, as this can further improve the compression set characteristics at high temperatures, as well as the low permeability to electrolyte components and swelling resistance. 19 The composition of fluororubber can be calculated from the composition measured by 1F-NMR.

[0020] In one embodiment, the hydrogen content of the fluororubber is 1.00% by mass or less. Preferably, the hydrogen content of the fluororubber is 0.99% by mass or less, more preferably 0.98% by mass or less, more preferably 0.50% by mass or more, and more preferably 0.55% by mass or more.

[0021] The hydrogen content of fluororubber is primarily determined by the number of hydrogen atoms directly bonded to the carbon atoms forming the main chain of the fluororubber. The hydrogen content of fluororubber can be adjusted by selecting the types of monomers that make up the fluororubber and adjusting the content of each monomer unit. 19 The composition of fluororubber can be calculated from the composition measured by 1F-NMR.

[0022] In one embodiment, the fluororubber contains vinylidene fluoride (VdF) units. In one embodiment, the VdF unit content in the fluororubber is 48.0 mol% or less relative to the total monomer units. Preferably, the VdF unit content in the fluororubber is 47.5 mol% or less, more preferably 47.0 mol% or less. By relatively reducing the VdF unit content, the hydrogen content can be reduced compared to ordinary partially fluorinated rubber, and the compression set characteristics at high temperatures, as well as low permeability to electrolyte components and swelling resistance, can be improved.

[0023] In one embodiment, the fluororubber contains tetrafluoroethylene (TFE) units. In one embodiment, the TFE unit content in the fluororubber is 20.0 to 50.0 mol%, more preferably 25.0 mol% or more, even more preferably 26.0 mol% or more, even more preferably 45.0 mol% or less, and still more preferably, based on the total monomer units. By increasing the TFE unit content relatively, the hydrogen content can be reduced compared to ordinary partially fluorinated rubber, and the compression set characteristics at high temperatures, as well as low permeability to electrolyte components and swelling resistance can be improved.

[0024] In one embodiment, the fluororubber contains hexafluoropropylene (HFP) units. In one embodiment, the HFP unit content in the fluororubber is 10.0 to 35.0 mol%, more preferably 13.0 mol% or more, even more preferably 15.0 mol% or more, still more preferably 18.0 mol% or more, more preferably 34.0 mol% or less, still more preferably 33.0 mol% or less, and still more preferably less than or equal to the total monomer units. By adjusting the HFP unit content within the above range, the fluororubber can be given low permeability to electrolyte components and swelling resistance, and its compression set characteristics at high temperatures can be further improved.

[0025] In one embodiment, the fluororubber contains VdF units, TFE units, and HFP units, with the VdF unit content being 39.5 to 48.0 mol%, the TFE unit content being 20.0 to 50.0 mol%, and the HFP unit content being 10.0 to 35.0 mol% relative to the total monomer units constituting the fluororubber.

[0026] In one embodiment, the fluororubber contains VdF units, TFE units, and HFP units, with the VdF unit content being 40.0 to 48.0 mol%, the TFE unit content being 25.0 to 40.0 mol%, and the HFP unit content being 15.0 to 30.0 mol% relative to the total monomer units constituting the fluororubber.

[0027] In one embodiment, the fluororubber contains VdF units, TFE units, and HFP units, with the VdF unit content being 39.5 to 47.0 mol%, the TFE unit content being 20.0 to 50.0 mol%, and the HFP unit content being 10.0 to 35.0 mol% relative to the total monomer units constituting the fluororubber.

[0028] In one embodiment, the fluororubber contains VdF units, TFE units, and HFP units, and the content of VdF units is 40.0 to 47.0 mol%, the content of TFE units is 25.0 to 40.0 mol%, and the content of HFP units is 15.0 to 30.0 mol% with respect to all monomer units constituting the fluororubber.

[0029] In one embodiment, the fluororubber contains VdF units, TFE units, and HFP units, and the content of VdF units is 40.0 to 47.0 mol%, the content of TFE units is 26.0 to 40.0 mol%, and the content of HFP units is 18.0 to 30.0 mol% with respect to all monomer units constituting the fluororubber.

[0030] In one embodiment, the fluororubber contains VdF units and fluorinated monomer units (excluding VdF units). Also, in one embodiment, the fluororubber contains VdF units, TFE units, HFP units, and fluorinated monomer units (excluding VdF units, TFE units, and HFP units).

[0031] Examples of the fluorinated monomer include, for example, VdF, TFE, HFP, fluoroalkyl vinyl ether (FAVE), chlorotrifluoroethylene (CTFE), trifluoroethylene, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, general formula: CHX 1 =CX 2 Rf 1 (where X 1 and X 2 are such that one is H and the other is F, and Rf 1 is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms.) A fluoromonomer represented by the formula, general formula: CH2=CH-(CF2) n -X 3 (where X 3 is H or F, and n is an integer of 3 to 10.) A fluoromonomer represented by the formula, a fluorinated monomer providing a crosslinking site, and the like.

[0032] As fluorinated monomers other than VdF, at least one selected from the group consisting of TFE, HFP, FAVE, CTFE, and 2,3,3,3-tetrafluoropropylene is preferred, and at least one selected from the group consisting of TFE, HFP, and FAVE is more preferred.

[0033] As fluorinated monomers other than VdF, TFE, and HFP, at least one selected from the group consisting of FAVE, CTFE, and 2,3,3,3-tetrafluoropropylene is preferred, with FAVE being more preferred.

[0034] As for FAVE, the general formula is: CF2=CFO(CF2CFX 4 O) p -(CF2CF2CF2O) q -Rf 2 (In the formula, X 4 represents F or CF3, and Rf 2 represents a perfluoroalkyl group with 1 to 5 carbon atoms. p represents an integer from 0 to 5, and q represents an integer from 0 to 5. ), and the general formula: CFX=CXOCF2OR 1 (In the formula, X represents the same or different H, F, or CF3, and R represents the same or different H, F, or CF3.) 1 This represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms, which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms, which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br, and I.) At least one selected from the group consisting of is preferred.

[0035] As the FAVE, perfluoro(methyl vinyl ether) or perfluoro(propyl vinyl ether) is more preferred, and perfluoro(methyl vinyl ether) is even more preferred. These can be used individually or in any combination.

[0036] In one embodiment, the fluororubber contains non-fluorinated monomer units. Examples of non-fluorinated monomers include ethylene, propylene, alkyl vinyl ethers, and non-fluorinated monomers that provide crosslinking sites.

[0037] In one embodiment, the fluororubber contains monomer units that provide crosslinking sites. The monomers that provide crosslinking sites may be either fluorinated monomers that provide crosslinking sites or non-fluorinated monomers that provide crosslinking sites.

[0038] A monomer that provides crosslinking sites is a monomer (curation site monomer) that has a crosslinkable group that provides crosslinking sites for forming crosslinks in a fluoropolymer. In one embodiment, the monomer that provides crosslinking sites has at least one crosslinkable group selected from the group consisting of a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, and a hydroxyl group.

[0039] As monomers that provide crosslinking sites, General formula (11):CX 111 2=CX 112 -R f 111 CHR 111 X 113 (In the formula, X 111 and X 112 These are independently a hydrogen atom, a fluorine atom, or CH3, R f 111 is a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group, R 111 is a hydrogen atom or CH3, X 113 ) is an iodine atom or a bromine atom. ) Fluoromers represented by General formula (12):CX 121 2=CX 122 -R f 121 X 123 (In the formula, X121 and X 122 These are independently a hydrogen atom, a fluorine atom, or CH3, R f 121 X is a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group, or a perfluoropolyoxyalkylene group. 123 ) is an iodine atom or a bromine atom. ) Fluoromers represented by General formula (13): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 131 (In the formula, m is an integer from 0 to 5, n is an integer from 1 to 3, X 131 ) is a fluoromonomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2I, and General formula (14): CH2=CFCF2O(CF(CF3)CF2O) m (CF(CF3)) n -X 141 (In the formula, m is an integer from 0 to 5, n is an integer from 1 to 3, X 141 ) is a fluoromonomer represented by a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2OH, and General formula (15):CR 151 R 152 =CR 153 -Z 151 -CR 154 =CR 155 R 156 (In the formula, R 151 , R 152 , R 153 , R 154 , R 155 and R 156 These are either the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms. 151 This includes linear or branched alkylene groups having 1 to 18 carbon atoms, cycloalkylene groups having 3 to 18 carbon atoms, alkylene groups or oxyalkylene groups having 1 to 10 carbon atoms that are at least partially fluorinated, or -(Q)p -CF2O-(CF2CF2O) m (CF2O) n -CF2-(Q) p - A monomer represented by (wherein Q is an alkylene group or an oxyalkylene group, p is 0 or 1, and m / n is 0.2 to 5) and having a molecular weight of 500 to 10000. It is preferable that it be at least one selected from the group consisting of the following:

[0040] X 113 and X 123 It is preferable that R is an iodine atom. f 111 and R f 121 It is preferable that it is a perfluoroalkylene group having 1 to 5 carbon atoms. 111 It is preferably a hydrogen atom. 131 It is preferable that this is a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2I. 141 It is preferable that the component is a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH2OH.

[0041] The monomers that provide the crosslinking site are CF2=CFOCF2CF(CF3)OCF2CF2CN, CF2=CFOCF2CF(CF3)OCF2CF2COOH, CF2=CFOCF2CF(CF3)OCF2CF2CH2I, CF2=CFOCF2CF2CH2I, CH2=CFCF2OCF(CF3)CF2OCF(CF3)CN, CH2=CFCF2OCF(CF3)CF2OCF(CF3)COOH, CH2=CFCF2OCF( It is preferable that it is at least one selected from the group consisting of CF3)CF2OCF(CF3)CH2OH, CH2=CHCF2CF2I, CH2=CH(CF2)2CH=CH2, CH2=CH(CF2)6CH=CH2, and CF2=CFO(CF2)5CN, and more preferably at least one selected from the group consisting of CF2=CFOCF2CF(CF3)OCF2CF2CN and CF2=CFOCF2CF2CH2I.

[0042] In one embodiment, the fluororubber contains either or both bromine and iodine atoms. In another embodiment, the fluororubber contains iodine or bromine atoms at the main chain ends and / or side chains.

[0043] Fluororubber containing one or both bromine and iodine atoms can be introduced into fluororubber, for example, by polymerizing monomers containing one or both bromine and iodine atoms. That is, in one embodiment, fluororubber contains monomer units containing one or both bromine and iodine atoms. Examples of monomer units containing one or both bromine and iodine atoms include monomers that provide the crosslinking sites described above, which contain one or both bromine and iodine atoms.

[0044] Furthermore, fluororubber containing one or both bromine and iodine atoms can be manufactured, for example, by using a bromine compound or an iodine compound as a chain transfer agent. A polymerization method using a bromine compound or an iodine compound includes, for example, emulsion polymerization in an aqueous medium under pressurized conditions in the presence of a bromine compound or an iodine compound, in a substantially oxygen-free environment (iodine transfer polymerization). A typical example of a bromine compound or an iodine compound used is, for example, a general formula: R 2 I x Br y (In the formula, x and y are integers from 0 to 2, and satisfy 1 ≤ x + y ≤ 2, R 2 Examples of compounds represented by a saturated or unsaturated fluorohydrocarbon group or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, or a hydrocarbon group having 1 to 3 carbon atoms (which may contain an oxygen atom). By using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and functions as a crosslinking point.

[0045] Examples of fluororubbers include peroxide-crosslinkable fluororubbers, polyol-crosslinkable fluororubbers, and polyamine-crosslinkable fluororubbers. Peroxide-crosslinkable fluororubbers are preferred as the fluororubber material. The fluororubber for electrolytic capacitor sealing bodies of this disclosure has the above-mentioned VdF unit content and hydrogen content, but the crosslinking reaction proceeds smoothly by utilizing peroxide crosslinking.

[0046] The peroxide crosslinkable fluororubber is not particularly limited and any fluororubber having peroxide crosslinkable parts is acceptable. The peroxide crosslinkable parts are not particularly limited and can include, for example, iodine atoms, bromine atoms, etc. The iodine and bromine atom content of the fluororubber is preferably 0.001 to 10% by mass, more preferably 0.01% by mass or more, even more preferably 0.10% by mass or more, still more preferably 0.15% by mass or more, and more preferably 5% by mass or less. The iodine and bromine atom content can be measured by elemental analysis.

[0047] In one embodiment, the fluororubber contains substantially only VdF units, TFE units, and HFP units as monomer units. In one embodiment, the fluororubber contains substantially only VdF units, TFE units, and HFP units as monomer units, and also contains one or both of bromine atoms and iodine atoms. The content of VdF units, TFE units, and HFP units in fluororubber may be 90.0 mol% or more, 90.5 mol% or more, or 99.9 mol% or more, and may be 100 mol% or less, relative to the total amount of monomer units. Furthermore, the total content of fluorinated monomer units (excluding VdF units, TFE units, and HFP units) and non-fluorinated monomer units in fluororubber may be 1.0 mol% or less, 0.5 mol% or less, or 0.1 mol% or less, and may be 0 mol% or more.

[0048] The Mooney viscosity (ML1+10(121°C)) of fluororubber at 121°C is preferably 2 or higher, more preferably 5 or higher, even more preferably 10 or higher, preferably 100 or lower, and more preferably 80 or lower. The Mooney viscosity is measured in accordance with ASTM-D1646-15 and JIS K6300-1:2013. By keeping the Mooney viscosity of fluororubber within the above range, the processability of the fluororubber is improved, and as a result, the productivity of molded articles obtained from fluororubber, such as electrolytic capacitor seals, is improved.

[0049] The glass transition temperature of fluororubber is preferably 25°C or lower, more preferably 15°C or lower, even more preferably 10°C or lower, and preferably -3°C or higher. The glass transition temperature can be determined by using a differential scanning calorimeter to obtain a DSC curve by heating 10 mg of the sample at 20°C / min, and then determining the temperature at which the extension of the baseline before and after the secondary transition of the DSC curve intersects with the tangent line at the inflection point of the DSC curve.

[0050] The fluororubber described above exhibits excellent compression set characteristics at high temperatures, as well as low permeability to electrolyte components such as γ-butyrolactone contained in the electrolyte of electrolytic capacitors, and excellent swelling resistance. Therefore, by forming a sealing body using the fluororubber described above and sealing the electrolytic capacitor with the resulting sealing body, the electrolyte in the electrolytic capacitor does not decrease easily even when the electrolytic capacitor is used in a high-temperature environment, thus significantly extending the lifespan of the electrolytic capacitor. The operating temperature of the electrolytic capacitor may be, for example, 150°C or higher or 200°C or higher, and may be below the boiling point of the electrolyte.

[0051] This disclosure also relates to the use of the above-mentioned fluororubber for forming a sealing body that suppresses the reduction of the electrolyte containing γ-butyrolactone or the like in an electrolytic capacitor.

[0052] (Fluororubber composition) A fluororubber composition can be prepared by mixing the above-mentioned fluororubber for electrolytic capacitor sealing bodies with a crosslinking agent. A crosslinked body can be obtained by crosslinking the fluororubber composition containing the fluororubber for electrolytic capacitor sealing bodies and the crosslinking agent. The fluororubber composition of this disclosure can be suitably used as a fluororubber composition for electrolytic capacitor sealing bodies. This disclosure also relates to the use of the above-mentioned fluororubber composition for forming a sealing body that suppresses the reduction of electrolyte containing γ-butyrolactone and the like in an electrolytic capacitor.

[0053] The type of crosslinking agent is not particularly limited and can be appropriately selected depending on the type of fluororubber and the mixing conditions.

[0054] If the fluororubber contains crosslinking groups (curesites), the crosslinking agent should be appropriately selected depending on the type of curesite or the intended use of the resulting molded product. Any of the following crosslinking systems can be used: polyamine crosslinking systems, polyol crosslinking systems, peroxide crosslinking systems, imidazole crosslinking systems, triazine crosslinking systems, oxazole crosslinking systems, and thiazole crosslinking systems.

[0055] As the crosslinking agent, at least one selected from the group consisting of polyamine crosslinking agents, polyol crosslinking agents, and peroxide crosslinking agents is preferred, with peroxide crosslinking agents being more preferred. The fluororubber for electrolytic capacitor sealing bodies of this disclosure has the above-mentioned VdF unit content and hydrogen content, but by using a peroxide crosslinking agent, the crosslinking reaction proceeds smoothly.

[0056] The peroxide crosslinking agent can be any organic peroxide that can readily generate peroxy radicals in the presence of heat or a redox system. Specifically, examples include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, benzoylperoxide, t-butylperoxybenzene, t-butylperoxymaleic acid, and t-butylperoxyisopropyl carbonate. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is preferred.

[0057] The amount of crosslinking agent added is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 7 parts by mass, and particularly preferably 1 to 5 parts by mass, per 100 parts by mass of fluororubber. If there is too little crosslinking agent, the degree of crosslinking will be insufficient, which tends to impair the performance of the molded article, such as heat resistance and oil resistance. If there is too much crosslinking agent, the crosslinking density will become too high, which tends to lengthen the crosslinking time, and is also undesirable from an economic standpoint. Furthermore, the moldability of the resulting fluororubber composition tends to decrease.

[0058] Examples of crosslinking agents for organic peroxides include triallyl cyanurate, triallyl isocyanurate (TAIC), triacrylic formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropagyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, and fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine- Examples include 2,4,6-trione, tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylcrylamide, 1,6-divindodecafluorohexane, hexaarylphosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene)cyanurate, and triallyl phosphite. Among these, triallyl isocyanurate (TAIC) is preferred in terms of crosslinkability and the physical properties of the crosslinked product.

[0059] The amount of organic peroxide crosslinking aid added is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 10 parts by mass, and particularly preferably 0.5 to 5 parts by mass, per 100 parts by mass of fluororubber. If the amount of crosslinking aid is too small, the heat resistance, oil resistance, compression set, and other properties of the molded article tend to decrease, and if the amount of crosslinking aid is too large, the moldability of the resulting fluororubber composition tends to decrease.

[0060] The compositions of this disclosure may contain, as needed, various additives commonly used in fluororubber compositions, such as acid acceptors, fillers (carbon black, bituminous coal, barium sulfate, diatomaceous earth, calcined clay, talc, wollastonite, carbon nanotubes, etc.), processing aids (wax, etc.), plasticizers, colorants, stabilizers, tackifiers (coumarone resin, coumarone-indene resin, etc.), mold release agents, conductivity imparters, thermal conductivity imparters, surface non-tackeners, flexibility imparters, heat resistance improvers, flame retardants, foaming agents, and antioxidants described in International Publication No. 2012 / 023485.

[0061] Examples of fillers include metal oxides such as titanium dioxide and aluminum oxide; metal hydroxides such as magnesium hydroxide and aluminum hydroxide; carbonates such as magnesium carbonate, aluminum carbonate, calcium carbonate, and barium carbonate; silicates such as magnesium silicate, calcium silicate, and aluminum silicate; sulfates such as aluminum sulfate, calcium sulfate, and barium sulfate; metal sulfides such as molybdenum disulfide, iron sulfide, and copper sulfide; diatomaceous earth, asbestos, lithopone (zinc sulfide / barium sulfide), graphite, carbon fluoride, calcium fluoride, coke, quartz powder, talc, mica powder, wollastonite, carbon fiber, aramid fiber, various whiskers, glass fiber, organic reinforcing agents, organic fillers, polytetrafluoroethylene, fluorine-containing thermoplastic resins, mica, silica, celite, clay, cellulose fiber, and cellulose nanofiber.

[0062] As carbon black, thermal carbon black and furnace carbon black are preferred, and MT carbon black, FT carbon black, and SRF carbon black are more preferred. When carbon black with a relatively large particle size, such as MT carbon black or FT carbon black, is blended, a molded article with excellent compression set characteristics can be obtained, while when carbon black with a fine particle size is blended, a molded article with excellent strength and elongation can be obtained. By blending different grades in combination, the above characteristics can be balanced.

[0063] Examples of fillers include flake-shaped or plate-shaped fillers. This disclosure also relates to compositions containing flake-shaped or plate-shaped fillers. The inclusion of flake-shaped or plate-shaped fillers in a composition further improves low permeability to electrolyte components and reduces volume resistivity. These are important properties particularly required for sealing rubber.

[0064] As the flake-shaped or plate-shaped filler, at least one selected from the group consisting of clay, mica, sericite, plate-shaped alumina, plate-shaped boron nitride, graphite, and expanded graphite is preferred, and at least one selected from the group consisting of clay, mica, and sericite is more preferred.

[0065] The average particle size of the flake-shaped or plate-shaped filler is preferably 3 to 50 μm, more preferably 5 μm or more, more preferably 40 μm or less, and even more preferably 30 μm or less. The average particle size is the particle size of 50% of the cumulative particle size distribution based on the number of particles, and the cumulative particle size distribution is determined from the equivalent circle diameter of 100 particles captured by a scanning electron microscope (SEM).

[0066] The aspect ratio (flatness) of the flake-shaped or plate-shaped filler is preferably 10 or more, more preferably 40 or more, and even more preferably 70 or more. The aspect ratio refers to the ratio of the major axis to the thickness of the flake-shaped or plate-shaped filler (major axis / thickness). The major axis and thickness of the filler can be measured by scanning electron microscope (SEM).

[0067] The compositions of this disclosure may also preferably contain granular fillers and flake-shaped or plate-shaped fillers. By using fillers of different shapes in combination, the low permeability to the electrolyte components is further improved, and the volume resistivity is further reduced.

[0068] The compositions of this disclosure may also preferably contain carbon black and flake-like or plate-like fillers. Using these in combination as fillers further improves low permeability to the electrolyte components and further reduces volume resistivity.

[0069] The content of fillers such as carbon black is not particularly limited, but is preferably 0 to 300 parts by mass, more preferably 1 to 150 parts by mass, even more preferably 1 to 100 parts by mass, and particularly preferably 1 to 75 parts by mass per 100 parts by mass of fluororubber.

[0070] When carbon black and flake-shaped or plate-shaped fillers are included in the composition, their respective mass ratios (carbon black / flak-shaped or plate-shaped fillers) are preferably 10 / 90 to 90 / 10, and more preferably 20 / 80 to 80 / 20.

[0071] The compositions of this disclosure can be prepared by mixing fluororubber, a crosslinking agent, and other desired materials using an open roll mixer, Banbury mixer, kneader, etc. Alternatively, they can be prepared by using a closed mixer or by co-coagulation from emulsion mixing. Crosslinking agents, additives, etc., may be added as desired.

[0072] (Molded body) Various molded articles can be obtained by molding the composition of this disclosure. Preferably, the molded article of this disclosure is obtained by crosslinking the above composition.

[0073] The molding can be carried out by conventionally known methods, such as compression molding, injection molding, extrusion molding, and calendering. Alternatively, the material may be dissolved in a solvent and molded by dip molding, coating, or other methods.

[0074] In obtaining various molded articles from the fluororubber composition disclosed herein, a crosslinking step may be performed. The crosslinking conditions vary depending on the molding method and the shape of the molded article, but are generally in the range of several seconds to 180 minutes at 100 to 200°C. In addition, secondary crosslinking may be performed to stabilize the physical properties of the crosslinked article. The conditions for secondary crosslinking are approximately 30 minutes to 30 hours at 150 to 300°C.

[0075] (Electrolytic capacitor sealing material) A molded article obtained by crosslinking the fluororubber composition of this disclosure can be suitably used as an electrolytic capacitor seal. The electrolytic capacitor seal of this disclosure may be composed of part or all of a molded article obtained by crosslinking the fluororubber composition described above. For example, the electrolytic capacitor seal of this disclosure may be a seal composed solely of a molded article obtained by crosslinking the fluororubber composition described above, or a seal composed of a molded article obtained by crosslinking the fluororubber composition described above and a resin film integrated together. Examples of resins that form the resin film include phenolic resin, polyethylene naphthalate, polyphenylene sulfide, polyethersulfone, polyetherimide, polyetheretherketone, polyimide, ethylenetetrafluoroethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, polychlorotrifluoroethylene, and polytetrafluoroethylene. The electrolytic capacitor sealing body of this disclosure exhibits excellent low permeability to γ-butyrolactone and other substances contained in the electrolyte of the electrolytic capacitor, even when it does not include a resin film, and further exhibits excellent swelling resistance to γ-butyrolactone and other substances.

[0076] The electrolytic capacitor sealing body of this disclosure exhibits excellent compression set characteristics at high temperatures, and also has excellent low permeability to γ-butyrolactone and other substances contained in the electrolyte of the electrolytic capacitor, as well as excellent swelling resistance. Therefore, electrolytic capacitors equipped with the electrolytic capacitor sealing body of this disclosure are less likely to experience electrolyte reduction, even when used continuously at high temperatures, and even when the electrolyte contains γ-butyrolactone or other substances. Consequently, electrolytic capacitors equipped with the electrolytic capacitor sealing body of this disclosure can be used at high temperatures for extended periods.

[0077] In one embodiment, the electrolytic capacitor comprises a capacitor element impregnated with an electrolyte, an outer case housing the capacitor element, a sealing body that seals the opening of the outer case, and a lead terminal that penetrates the sealing body and protrudes from the outer case to the outside. By using an electrolytic capacitor sealing body obtained by crosslinking the above-mentioned fluororubber composition as the sealing body, the electrolyte can be made less likely to decrease even when the electrolyte contains γ-butyrolactone or the like.

[0078] (Novel fluororubber (a)) The disclosure also relates to a fluororubber (a) having a novel monomer composition. Specifically, the fluororubber (a) of the disclosure contains VdF units, TFE units and HFP units, with the VdF unit content being 39.5 to 47.0 mol%, the TFE unit content being 20.0 to 50.0 mol%, and the HFP unit content being 10.0 to 35.0 mol% relative to the total monomer units constituting the fluororubber.

[0079] A more preferred monomer composition for fluororubber (a) is one in which the VdF unit content is 40.0 to 47.0 mol%, the TFE unit content is 25.0 to 40.0 mol%, and the HFP unit content is 15.0 to 30.0 mol%, relative to the total monomer units constituting the fluororubber.

[0080] A more preferred monomer composition for fluororubber (a) is one in which the VdF unit content is 40.0 to 47.0 mol%, the TFE unit content is 26.0 to 40.0 mol%, and the HFP unit content is 18.0 to 30.0 mol%, relative to the total monomer units constituting the fluororubber.

[0081] The VdF unit content in fluororubber (a) is 39.5 to 47.0 mol%, preferably 47.0 mol% or less, and more preferably 40.0 mol% or more.

[0082] The TFE unit content in fluororubber (a) is 20.0 to 50.0 mol%, more preferably 25.0 mol% or more, even more preferably 26.0 mol% or more, more preferably 45.0 mol% or less, and even more preferably 40.0 mol% or less, relative to the total monomer units.

[0083] The HFP unit content in fluororubber (a) is 10.0 to 35.0 mol%, more preferably 13.0 mol% or more, even more preferably 15.0 mol% or more, still more preferably 18.0 mol% or more, more preferably 34.0 mol% or less, still more preferably 33.0 mol% or less, and still more preferably 30.0 mol% or less, relative to the total monomer units.

[0084] Since the fluororubber (a) of this disclosure has the above-described structure, it is possible to obtain a molded article that exhibits excellent low permeability to electrolyte components such as γ-butyrolactone.

[0085] In one embodiment, fluororubber (a) contains one or both bromine atoms and iodine atoms. In one embodiment, fluororubber (a) contains iodine atoms or bromine atoms in the main chain ends and / or side chains.

[0086] The iodine and bromine atom content of fluororubber (a) is preferably 0.001 to 10% by mass, more preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and more preferably 5% by mass or less.

[0087] Fluororubber (a) may contain fluorinated monomer units (excluding VdF units, TFE units, and HFP units) or non-fluorinated monomer units in addition to VdF units, TFE units, and HFP units, but it is preferable that it does not contain any of these monomer units. In one embodiment, fluororubber (a) contains substantially only VdF units, TFE units, and HFP units as monomer units. In one embodiment, fluororubber (a) contains substantially only VdF units, TFE units, and HFP units as monomer units, and contains either or both bromine atoms and iodine atoms.

[0088] The content of VdF units, TFE units, and HFP units in fluororubber (a) may be 90.0 mol% or more, 90.5 mol% or more, or 99.9 mol% or more, and may be 100 mol% or less, relative to the total monomer units. In addition, the total content of fluorinated monomer units (excluding VdF units, TFE units, and HFP units) and non-fluorinated monomer units in fluororubber (a) may be 1.0 mol% or less, 0.5 mol% or less, or 0.1 mol% or less, and may be 0 mol% or more.

[0089] The Mooney viscosity (ML1+10(121°C)) of fluororubber (a) at 121°C is preferably 2 or higher, more preferably 5 or higher, even more preferably 10 or higher, preferably 100 or lower, and more preferably 80 or lower.

[0090] The glass transition temperature of fluororubber (a) is preferably 25°C or lower, more preferably 15°C or lower, even more preferably 10°C or lower, and preferably -3°C or higher.

[0091] The iodine and bromine atom content of fluororubber (a) is preferably 0.001 to 10% by mass, more preferably 0.01% by mass or more, even more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and more preferably 5% by mass or less.

[0092] Fluororubber (a) can be produced by radical polymerization. The polymerization method may be bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization, but emulsion polymerization is preferred because it is easy to implement industrially.

[0093] In the polymerization described above, polymerization initiators, chain transfer agents, surfactants, hydrophilic compounds, solvents, etc., can be used, and conventionally known ones can be used.

[0094] In polymerization for the production of fluororubber (a), an oil-soluble radical polymerization initiator or a water-soluble radical initiator can be used as the polymerization initiator.

[0095] Oil-soluble radical polymerization initiators may be known oil-soluble peroxides, such as dialkyl peroxycarbonates including diisopropyl peroxydicarbonate and disec-butyl peroxydicarbonate, peroxyesters including t-butyl peroxyisobutyrate and t-butyl peroxypivalate, and dialkyl peroxides including dit-butyl peroxide.

[0096] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, or sodium salts of persulfuric acid, perboric acid, perchloric acid, superphosphate, or percarbonate, as well as t-butyl permalate and t-butyl hydroperoxide. Reducing agents such as sulfites and sulfites may also be included, and their amount may be 0.1 to 20 times the amount of the peroxide.

[0097] There are no particular limitations on the amount of radical polymerization initiator added, but it is sufficient to add at least an amount that does not significantly reduce the polymerization rate (for example, a few ppm relative to water concentration) in a lump sum at the beginning of polymerization, or sequentially or continuously. The upper limit is the range in which the heat of the polymerization reaction can be removed from the apparatus surface.

[0098] As the surfactant, known surfactants can be used, such as nonionic surfactants, anionic surfactants, and cationic surfactants. The amount added (relative to the polymerization water) is preferably 10 ppm to 20% by mass, more preferably 10 to 5000 ppm, and even more preferably 50 to 5000 ppm.

[0099] As the hydrophilic compound, known unsaturated hydrophilic compounds and hydrophilic polymers obtained by polymerizing known unsaturated hydrophilic compounds can be used. The amount added (relative to polymerization water) is preferably 10 to 5000 ppm. More preferably, it is 50 to 5000 ppm.

[0100] The solvent is preferably one that does not exhibit chain transfer properties. In the case of solution polymerization, dichloropentafluoropropane (R-225) is an example, while in the case of emulsion polymerization and suspension polymerization, water, a mixture of water and a water-soluble organic solvent, or a mixture of water and a water-insoluble organic solvent are examples.

[0101] In polymerization for the production of fluororubber (a), examples of chain transfer agents include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, methane, ethane, propane, isopropanol, acetone, various mercaptans, carbon tetrachloride, and cyclohexane. Bromine compounds or iodine compounds mentioned above can also be used as chain transfer agents.

[0102] In polymerization for the production of fluororubber (a), the polymerization temperature, polymerization pressure, and polymerization time vary depending on the type of solvent and polymerization initiator, but may be -15 to 150°C, atmospheric pressure to 6.5 MPa, and 1 to 24 hours.

[0103] The fluororubber (a) obtained by polymerization may be in any form, such as an aqueous dispersion or powder.

[0104] In the case of emulsion polymerization, fluororubber (a) powder can be obtained by coagulating the dispersion after polymerization, washing with water, dehydrating, and drying. Coagulation can be achieved by adding an inorganic salt such as aluminum sulfate or an inorganic acid, applying mechanical shear force, or freezing the dispersion. In the case of suspension polymerization, it can be obtained by recovering it from the dispersion after polymerization and drying it. In the case of solution polymerization, it can be obtained by drying the solution containing fluororubber (a) as is, or by purifying it by adding a poor solvent dropwise.

[0105] The fluororubber (a) of this disclosure can be suitably used as a fluororubber for electrolytic capacitor sealing bodies, and can also be suitably used for various other applications besides electrolytic capacitor sealing bodies. The fluororubber (a) can be crosslinked in the same manner as the fluororubber for electrolytic capacitor sealing bodies described above, and can be molded in the same manner.

[0106] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0107] <1> According to the first aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, wherein the vinylidene fluoride unit content is 48.0 mol% or less relative to the total monomer units, and the hydrogen content is 1.00 mass% or less. <2> According to the second aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, according to a first aspect, having a melting peak (ΔH) of 4.5 J / g or less. <3> According to the third aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, according to a first or second view, having a Mooney viscosity (ML1 + 10 (121°C)) of 2 or more at 121°C. <4> According to the fourth aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, having a hydrogen content of 0.50% by mass or more, according to any of the first to third aspects. <5> According to the fifth aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, wherein the content of vinylidene fluoride units is 39.5 mol% or more relative to the total monomer units, according to any of the first to fourth aspects. <6> According to the sixth aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, which contains tetrafluoroethylene units, and the content of tetrafluoroethylene units is 20.0 to 50.0 mol% of the total monomer units, according to any of the first to fifth aspects. <7> According to the seventh aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, which contains hexafluoropropylene units, and the content of hexafluoropropylene units is 10.0 to 35.0 mol% of the total monomer units, according to any of the first to sixth views. <8> According to the eighth aspect of this disclosure, A fluororubber for electrolytic capacitor sealing is provided, containing either or both bromine atoms and iodine atoms, according to any of the first to seventh aspects. <9> According to the ninth aspect of this disclosure, A fluororubber composition containing a fluororubber and a crosslinking agent for use as a sealing body for electrolytic capacitors is provided according to any of the first to eighth aspects. <10> According to the tenth aspect of this disclosure, A fluororubber for electrolytic capacitor sealing bodies according to any of the first to eighth aspects is provided, and a fluororubber composition containing a flake-shaped or plate-shaped filler is also provided. <11> According to the eleventh aspect of this disclosure, A fluororubber composition according to a ninth aspect is provided, wherein the crosslinking agent is a peroxide crosslinking agent. <12> According to the 12th aspect of this disclosure, An electrolytic capacitor sealing body is provided, obtained by crosslinking a fluororubber composition according to the eleventh aspect. <13> According to the 13th aspect of this disclosure, A fluororubber containing vinylidene fluoride units, tetrafluoroethylene units, and hexafluoropropylene units, The content of vinylidene fluoride units is 39.5 to 47.0 mol% relative to the total monomer units. The tetrafluoroethylene unit content is 20.0 to 50.0 mol% relative to the total monomer units. The hexafluoropropylene unit content is 10.0 to 35.0 mol% relative to the total monomer units. Fluororubber is provided. <14> According to the fourteenth aspect of this disclosure, A fluororubber according to a 13th aspect is provided, having a glass transition temperature of 25°C or lower. <15> According to the 15th aspect of this disclosure, A fluororubber according to the 13th or 14th aspect is provided, wherein the content of iodine atoms and bromine atoms is 0.10% by mass or more. <16> According to the sixteenth aspect of this disclosure, A fluororubber is provided that has a Mooney viscosity (ML1 + 10 (121°C)) of 2 or more at 121°C, according to any of the 13th to 15th aspects. [Examples]

[0108] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0109] Each value in the examples was measured by the following method.

[0110] <Solid content concentration of aqueous dispersion> One g of aqueous dispersion was dried in a forced-air dryer at 150°C for 180 minutes. The mass of the residue after heating was measured, and the ratio (mass%) of the mass of the residue to the mass of the aqueous dispersion (1 g) was determined.

[0111] <Average particle size> The average particle size (cumulant average diameter) of fluorine-containing elastomer particles in an aqueous dispersion was measured using dynamic light scattering with an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) and calculated using the cumulant method.

[0112] <Moony viscosity> The viscosity was measured using a Mooney viscometer (ALPHA TECHNOLOGIES Premier MV) in accordance with ASTM D1646-15 and JIS K6300-1:2013. The measurement temperature was 121°C.

[0113] <Monomer composition of fluororubber> 19 The polymer was dissolved in acetone or hexafluorobenzene and measured using F-NMR (JEOL JMN-ECZ500R).

[0114] <Hydrogen content> 19 The composition of fluororubber was calculated from the composition measured by 1F-NMR.

[0115] <Fluorine content> 19 The composition of fluororubber was calculated from the composition measured by 1F-NMR.

[0116] <Glass transition temperature (Tg)> Using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, X-DSC7000), a DSC curve was obtained by heating 10 mg of the sample at 20°C / min. The temperature at which the extension of the baseline before and after the second-order transition of the DSC curve intersects with the tangent line at the inflection point of the DSC curve was defined as the glass transition temperature.

[0117] <Heat of fusion> Using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, X-DSC7000), a DSC curve was obtained by heating 10 mg of the sample at 20°C / min, and the heat of fusion was calculated from the magnitude of the melting peak (ΔH) that appeared in the DSC curve.

[0118] <Iodine content> 12 mg of the sample (fluorine-containing elastomer) was mixed with 5 mg of Na2SO3, and an absorption solution was prepared by dissolving 30 mg of a 1:1 (by weight) mixture of Na2CO3 and K2CO3 in 20 ml of pure water. This solution was burned in a quartz flask under oxygen, and after standing for 30 minutes, it was measured using a Shimadzu 20A ion chromatograph. Calibration curves were calculated using KI standard solutions, solutions containing 0.5 ppm and 1.0 ppm of iodide ions.

[0119] <Crosslinking properties> For the fluororubber composition, a vulcanization tester (MDR H2030, manufactured by M&K Co., Ltd.) was used during primary crosslinking to determine the crosslinking curve at the temperatures listed in the table. From the change in torque, the minimum torque (ML), maximum torque (MH), crosslinking induction time (T10), and optimal crosslinking time (T90) were determined.

[0120] <100% Modulus, Tensile Strength and Elongation> A dumbbell-shaped test specimen (No. 6) was prepared using a 2 mm thick cross-linked sheet. Using the obtained test specimen and a tensile testing machine (Tensilon RTG-1310, A&D Corporation), the 100% Modulus (M100), tensile strength (TS), and elongation (EL) of the No. 6 dumbbell at 23°C were measured at a rate of 500 mm / min in accordance with JIS K6251-1:2015.

[0121] <Hardness (HS 3sec)> Three 2mm thick cross-linked sheets were stacked, and the durometer hardness (Type A, after 3 seconds) was measured in accordance with JIS K6251-3:2012.

[0122] <Hardness (IRHD)> A 2mm thick cross-linked sheet was used, and its hardness was measured using the IRHD M method in accordance with JIS K6253-2:2012.

[0123] <Compression set> Molded articles (small test specimens for compression set measurement (P-24, O-ring)) were prepared using the fluororubber compositions prepared in the examples and comparative examples. The obtained test specimens were measured according to Method A of JIS K6262:2013, with a compressibility of 25%, a test temperature of 200°C, and a test time of 70 hours.

[0124] <γ-Butyrolactone immersion test> Samples were prepared from molded bodies obtained in the examples and comparative examples. Samples whose mass and specific gravity had been measured beforehand using an automatic hydrometer (high-precision type DMA-220H, manufactured by Shinko Denshi Co., Ltd.) were immersed in a 100 ml glass container with a lid containing 50 ml of γ-butyrolactone. After 70 hours in a constant temperature device (60°C), the samples were removed and their mass and specific gravity were measured again using the automatic hydrometer. The volume of the sample before and after the test (volume = mass ÷ specific gravity) was calculated, and the rate of change in volume of the sample before and after the immersion test (ΔV) was determined using the following formula. Volume change rate (%) = (Sample volume after test - Sample volume before test) × 100 / Sample volume before test

[0125] <γ-butyrolactone permeation test> A SUS container with a volume of 70 mL (opening area 1.26 × 10⁻³ m²) was used to prepare a test specimen by placing 20 mL of γ-butyrolactone into the container, setting a 0.5 mm thick sheet-like molded body inside, and sealing the container. An electronic balance (GX-603AWP, A&D Corporation) was used to measure the weight of the test specimen. The specimen was placed in a constant temperature device (60°C) with the γ-butyrolactone in contact with the liquid, and its weight was measured. The permeability coefficient was calculated using the following formula once the weight loss per unit time became constant.

[0126]

number

[0127] <Volume resistivity> Molded articles (crosslinked sheets with a thickness of 2 mm) were prepared using the fluororubber compositions prepared in the examples and comparative examples. The obtained molded articles were measured at room temperature with an applied voltage of 1000 V using the double-ring electrode method in accordance with JIS K6271.

[0128] [Comparative Example 1] The following fluorine-containing elastomers were used. VdF / TFE / HFP copolymer VdF / TFE / HFP=51.5 / 21.0 / 27.5mol% Fluorine content: 70.2% by mass Hydrogen content: 1.09% by mass Mooney viscosity (ML1+10 (121℃)): 21 Iodine content: 0.22% by mass Glass transition temperature: -5.6℃

[0129] [Comparative Example 2] 3917g of deionized water, 7.834g of CF3CF2CF2CF2CF2COONH4, and 0.392g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 6.0L SUS polymerization tank, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of vinylidene fluoride [VDF] / tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] (=20 / 15 / 65 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG, while stirring at 498 rpm.

[0130] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.078 g of ammonium persulfate (APS) in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=45 / 30 / 25 mol%) was added so that the internal pressure remained constant at 2.01 MPaG.

[0131] When 25 g and 619 g of the mixed monomer were added, 1.558 g and 2.339 g of iodine compound I(CF2)4I were injected under nitrogen gas pressure.

[0132] At the point when 1237 g of the mixed monomer was added (reaction time 265 minutes), stirring was stopped and the polymerization vessel was depressurized until it reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.5% by mass. The average particle size of the aqueous dispersion was 136.6 nm.

[0133] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 79, the composition determined by NMR was VDF / TFE / HFP = 47.5 / 30.0 / 22.5 (molar ratio) (fluorine content: 70.6 mass%, hydrogen content: 1.02 mass%), the iodine content was 0.16 mass%, and the glass transition temperature was -1.3°C.

[0134] [Example 1] 3917g of deionized water, 7.835g of CF3CF2CF2CF2CF2COONH4, and 0.391g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 6.0L stainless steel polymerization tank, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=15 / 16 / 69 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG while stirring at 498 rpm.

[0135] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.078 g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=37 / 37 / 26 mol%) was added so that the internal pressure remained constant at 2.01 MPaG.

[0136] When 25 g and 619 g of the mixed monomer were added, 1.558 g and 2.339 g of iodine compound I(CF2)4I were injected under nitrogen gas pressure.

[0137] At the point when 1237 g of the mixed monomer was added (reaction time 398 minutes), stirring was stopped and the polymerization vessel was depressurized until it reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 22.8% by mass. The average particle size of the aqueous dispersion was 125.1 nm.

[0138] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 70, the composition determined by NMR was VDF / TFE / HFP = 41.5 / 36.7 / 21.8 (molar ratio) (fluorine content: 71.4 mass%, hydrogen content: 0.87 mass%), the iodine content was 0.16 mass%, and the glass transition temperature was 5.4°C.

[0139] [Example 2] 3917g of deionized water, 7.835g of CF3CF2CF2CF2CF2COONH4, and 0.391g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 6.0L SUS polymerization tank, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=15 / 15 / 70 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG while stirring at 498 rpm.

[0140] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.078 g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=35 / 33 / 32 mol%) was added so that the internal pressure remained constant at 2.01 MPaG.

[0141] When 25 g and 619 g of the mixed monomer were added, 1.754 g and 2.805 g of iodine compound I(CF2)4I were injected under nitrogen gas pressure.

[0142] At 320 minutes of reaction time, an aqueous polymerization initiator solution containing 0.039 g of APS dissolved in deionized water was injected under pressure with nitrogen gas. Additionally, at 393 minutes, 420 minutes, and 465 minutes of reaction time, an aqueous polymerization initiator solution containing 0.020 g of APS dissolved in deionized water was injected under pressure with nitrogen gas.

[0143] At the point when 1237 g of the mixed monomer was added (reaction time 591 minutes), stirring was stopped and the polymerization vessel was depressurized until it reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 22.3% by mass. The average particle size of the aqueous dispersion was 133.0 nm.

[0144] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 45, the composition determined by NMR was VDF / TFE / HFP = 41.3 / 32.0 / 26.7 (molar ratio) (fluorine content: 71.5 mass%, hydrogen content: 0.85 mass%), the iodine content was 0.18 mass%, and the glass transition temperature was 2.5°C.

[0145] [Example 3] 3917g of deionized water, 7.835g of CF3CF2CF2CF2CF2COONH4, and 0.391g of CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 were added to a 6.0L SUS polymerization tank, and the system was purged with nitrogen to remove oxygen. The polymerization tank was heated to 80°C, and monomers (initial monomers) were injected under pressure at a molar ratio of VDF / TFE / HFP (=14 / 16 / 70 mol%) so that the internal pressure of the polymerization tank was 2.00 MPaG while stirring at 498 rpm.

[0146] Next, an aqueous polymerization initiator solution, prepared by dissolving 0.078 g of APS in deionized water, was injected under pressure with nitrogen gas to start the reaction. As polymerization progressed, when the internal pressure dropped to 1.98 MPaG, a mixed monomer of VDF / TFE / HFP (=41.5 / 33 / 25.5 mol%) was added so that the internal pressure remained constant at 2.01 MPaG.

[0147] When 25 g and 619 g of the mixed monomer were added, 1.754 g and 2.805 g of iodine compound I(CF2)4I were injected under nitrogen gas pressure.

[0148] At the point when 1237g of the mixed monomer was added (reaction time 343 minutes), stirring was stopped and the polymerization vessel was depressurized until it reached atmospheric pressure. The polymerization vessel was cooled to obtain an aqueous dispersion with a solid content of 23.1% by mass. The average particle size of the aqueous dispersion was 125.2 nm.

[0149] An aqueous aluminum sulfate solution was added to the above aqueous dispersion to induce coagulation. The resulting coagulation was washed with water and dried to obtain a fluorine-containing elastomer. The Mooney viscosity of the fluorine-containing elastomer was ML1 + 10 (121°C) = 52, the composition determined by NMR was VDF / TFE / HFP = 46.1 / 31.1 / 22.8 (molar ratio) (fluorine content: 70.8 mass%, hydrogen content: 0.98 mass%), the iodine content was 0.18 mass%, and the glass transition temperature was -0.2°C.

[0150] Fluorine-containing elastomers from Comparative Examples 1-2 and Examples 1-3, carbon black (Thermax N990, manufactured by Cancarb), crosslinking aid (triallyl isocyanurate, TAIC, manufactured by Mitsubishi Chemical Corporation), and crosslinking agent (2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Perhexa 25, manufactured by NOF Corporation) were mixed in the proportions shown in Table 1 to prepare fluororubber compositions. The obtained fluororubber compositions were crosslinked under the crosslinking conditions shown in Table 1 to obtain molded articles. The results are shown in Table 1.

[0151] [Table 1]

[0152] [Examples 4-14] A fluororubber composition was prepared by mixing the fluorine-containing elastomer from Example 2, carbon black (Thermax N990, manufactured by Cancarb), a crosslinking aid (triallyl isocyanurate, TAIC, manufactured by Mitsubishi Chemical Corporation), a crosslinking agent (2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Perhexa 25, manufactured by NOF Corporation), and a filler in the proportions shown in Table 2.

[0153] In these examples, the following fillers were used. Fillers A to G are all in the shape of flakes or plates. Filler A (manufactured by Takehara Chemical Industry Co., Ltd., Glowmax LL): Calcined clay Filler B (manufactured by Yamaguchi Mica Co., Ltd., MICA POWDER AB-25S): Mica, average particle size 24 μm, aspect ratio 80 Filler C (manufactured by Yamaguchi Mica Co., Ltd., MICA POWDER NCF-322): Mica, average particle size 24 μm, aspect ratio 120 Packing material D (manufactured by Sanshin Mining Co., Ltd., sericite JS-A): Sericite, average particle size 10-15 μm Filler E (manufactured by Sanshin Mining Co., Ltd., sericite FSE): sericite, average particle size 6-8 μm Packing material F (manufactured by Sanshin Mining Co., Ltd., sericite FMK): sericite, average particle size 10-20 μm Filler G (manufactured by Kunimine Industries, Kunipia-F): Nanoclay

[0154] The obtained fluororubber composition was crosslinked under the crosslinking conditions described in Table 2 to obtain a molded article. The results are shown in Table 2.

[0155] [Table 2]

Claims

1. A fluororubber composition for an electrolytic capacitor sealing body, comprising a fluororubber for electrolytic capacitor sealing bodies and a flake-shaped or plate-shaped filler, The vinylidene fluoride unit content of the fluororubber for the electrolytic capacitor sealing body is 48.0 mol% or less relative to the total monomer units. The tetrafluoroethylene unit content of the fluororubber for the electrolytic capacitor sealing body is 20.0 to 50.0 mol% relative to the total monomer units. The fluororubber for the electrolytic capacitor sealing body contains 10.0 to 35.0 mol% of hexafluoropropylene units relative to the total monomer units. A fluororubber composition for electrolytic capacitor sealing, wherein the hydrogen content of the fluororubber for electrolytic capacitor sealing is 0.55% by mass or more and 1.00% by mass or less.

2. The fluororubber composition for electrolytic capacitor sealing body according to Claim 1, wherein the magnitude of the melting peak (ΔH) of the fluororubber for electrolytic capacitor sealing body is 4.5 J / g or less.

3. The fluororubber composition for electrolytic capacitor sealing according to claim 1 or 2, wherein the Mooney viscosity (ML1 + 10 (121°C)) of the fluororubber for electrolytic capacitor sealing is 2 or more at 121°C.

4. The fluororubber composition for electrolytic capacitor sealing according to claim 1 or 2, wherein the content of vinylidene fluoride units in the fluororubber for electrolytic capacitor sealing is 39.5 mol% or more with respect to the total monomer units.

5. The fluororubber composition for electrolytic capacitor sealing according to claim 1 or 2, wherein the fluororubber for electrolytic capacitor sealing contains one or both of bromine atoms and iodine atoms.

6. The fluororubber composition for electrolytic capacitor sealing body according to claim 1 or 2, which contains a crosslinking agent.

7. The fluororubber composition for electrolytic capacitor sealing body according to claim 6, wherein the crosslinking agent is a peroxide crosslinking agent.

8. The fluororubber composition for electrolytic capacitor sealing body according to claim 1 or 2, which contains carbon black.

9. An electrolytic capacitor seal obtained by crosslinking the fluororubber composition for electrolytic capacitor seals described in claim 7.

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