JPH07335504A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a highly reliable electrolytic capacitor which is capable of realizing a long service life at high temperatures. CONSTITUTION:In an electrolytic capacitor having a capacitor element 1 impregnated with an electrolyte solution housed in a metallic casing 3 and sealed by an elastic sealing body 2, the elastic sealing body 2 is made of a material prepared by mixing at least magnesia with three-component copolymer of isobutylene, isoprene and divinylbenzene as main polymer and then peroxide- vulcanizing the mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable electrolytic capacitor having an improved sealing body.

[0002]

2. Description of the Related Art An electrolytic capacitor is formed by impregnating a capacitor element in which an anode foil and a cathode foil are wound with a separator paper in between and impregnating the electrolytic solution with the electrolytic solution impregnated in a metal case. The case is formed by sealing it with an elastic sealing body. Conventionally, as the electrolytic solution of the electrolytic capacitor, the one using ethylene glycol as the main solvent has been widely used, and the elastic sealing body is made of natural rubber (N
R), styrene butadiene (SBR), ethylene propylene terpolymer (EPT) and the like have been used.

In recent years, reliability is required in a wide temperature range, and the solvent of the electrolytic solution is also N, N-dimethylformamide (DMF) or γ-butyrolactone (GBL).
Are being used. However, DMF
Since GBL and GBL have high volatility and the electrolytic solution permeates as vapor in the conventional elastic sealing body, the reliability cannot be maintained. Therefore, isobutylene-isoprene rubber (IIR) having higher airtightness has come to be used. However, IIR has a problem in heat resistance. Examples of IIR vulcanization methods include sulfur vulcanization, quinoid vulcanization, and resin vulcanization.
Among them, the resin vulcanized ones are excellent in heat resistance, but the resin vulcanized IIR also has a problem that it is softened when left in a high temperature for a long time.

[0004]

Recently, in order to improve the heat resistance of IIR, a three-component copolymer of isobutylene, isoprene and divinylbenzene is used as a polymer as disclosed in JP-A-55-15862. A peroxide-vulcanized crosslinked IIR has been proposed as the above. This cross-linking I
IR has better heat resistance than that of resin vulcanization. However, on the contrary, since the most important airtightness is inferior, there is a problem that when the capacitor test is performed at a high temperature for a long time, the characteristics change due to the permeation and dissipation of the electrolytic solution becomes large. In addition, it is necessary to use a highly reliable electrolytic solution for the capacitor for high temperature and long life, so that a low specific resistance electrolytic solution that is a combination of γ-butyrolactone and a quaternary ammonium salt of an organic acid is used. It has become to. However, an electrolytic solution using this quaternary ammonium salt and a crosslinked IIR
With respect to the electrolytic capacitor combined with the sealing body according to the above, when a life test was conducted at high temperature, a new problem was found that the electrolytic solution leaked out from the vicinity of the lead wire through hole of the sealing body.

The present invention has been made in view of the above problems, and by using an elastic sealing body having excellent heat resistance, airtightness and chemical resistance, high reliability which can achieve high temperature and long life is obtained. It is intended to provide an electrolytic capacitor.

[0006]

According to the present invention according to the above object, in an electrolytic capacitor in which a capacitor element impregnated with an electrolytic solution is housed in a metal case and sealed by an elastic sealing body, the elastic sealing body is isobutylene, isoprene or It is characterized in that it is a material obtained by peroxide-vulcanizing a three-component copolymer of divinylbenzene as a main polymer and at least magnesia being blended therein. The compounding amount of magnesia is preferably 1 to 50 parts with respect to the main polymer. The elastic sealing body has chemical resistance to an electrolytic solution containing γ-butyrolactone as a main solvent and a quaternary ammonium salt of an organic acid as a solute. Further, as the polymer for the elastic sealing body, the above-mentioned three-component copolymer may be used, of course, but the same polymer may be used by blending with ethylene propylene terpolymer (EPDM) which is also capable of peroxide vulcanization. The effect can be obtained.

[0007]

When a ternary copolymer of isobutylene, isoprene and divinylbenzene is used as a polymer for peroxide vulcanization, the double bond of divinylbenzene is dissolved to form a C—C bond crosslink, which is more than conventional IIR. Heat resistance is improved. Magnesia (MgO) is added to this crosslinked IIR
When blended with, the compound acts as a vulcanization accelerating aid and increases the crosslink density, so that the airtightness can be improved. Further, when the amount of magnesia increases, it acts like a filler, so that the rubber hardness can be increased.

When contacted with an electrolytic solution containing a quaternary ammonium salt, even the crosslinked IIR swells to lower the airtightness.
When a long-term capacitor life test was performed, the electrolytic solution sometimes leaked from the vicinity of the lead wire through hole. As a countermeasure for this, the inventors have found that it is good to make the sealing body alkaline. Since the compounding of magnesia has an effect of making the crosslinked IIR alkaline, in addition to the above-mentioned effect, the present invention can provide an elastic sealing body having excellent heat resistance, airtightness and chemical resistance. Actually, 2 g of rubber was made into a powder, immersed in 100 g of pure water, extracted with boiling water for 30 minutes, and the pH was measured.
On the other hand, the compounding amount of 10 parts of magnesia to 100 parts of the polymer was 9.99.

[0009]

EXAMPLES The present invention will be described in detail below based on examples. [Example 1] 2 parts of magnesia were mixed with 100 parts of a polymer consisting of a three-component copolymer of isobutylene, isoprene and divinylbenzene, and peroxide vulcanized with dicumyl peroxide to prepare an IIR rubber. Example 2 In the same manner as in Example 1, 100 parts of the polymer and 5 parts of magnesia were blended to prepare an IIR rubber.

Example 3 In the same manner as in Example 1, 100 parts of polymer was mixed with 10 parts of magnesia to prepare IIR.
A rubber was produced. Example 4 In the same manner as in Example 1, 20 parts of magnesia was mixed with 100 parts of the polymer to prepare an IIR rubber. Example 5 In the same manner as in Example 1, 30 parts of magnesia was mixed with 100 parts of the polymer to prepare an IIR rubber.

Example 6 In the same manner as in Example 1, 100 parts of polymer was mixed with 40 parts of magnesia to prepare IIR.
A rubber was produced. Example 7 In the same manner as in Example 1, 100 parts of polymer was mixed with 50 parts of magnesia to prepare an IIR rubber. [Conventional Example 1] A polymer composed of a three-component copolymer of isobutylene, isoprene and divinylbenzene was peroxide vulcanized with dicumyl peroxide to prepare IIR. [Conventional Example 2] I was obtained by vulcanizing an isobutylene or isoprene polymer with an alkylphenol formaldehyde resin.
An IR rubber was produced.

[0012]

[Table 1]

Table 1 shows the compounding and physical properties of the IIR rubber prepared. Hardness is measured by JIS K6301 spring type hardness test type A, and compression set is JIS K6301.
A test piece according to the 301 compression set test was compressed by 25% and then left in a constant temperature bath at 100 ° C. for 70 hours and calculated by the following formula.

[0014]

[Equation 1]

Here, tθ is the original thickness of the test piece, t ₁ is the thickness of the test piece after the test, and t ₂ is the thickness of the spacer. According to Table 1, it is understood that the hardness increases as the magnesia compounding amount is increased. If the hardness is low, problems may occur in the rubber threading process of the lead wire during capacitor manufacturing,
When assembling, problems may occur in rubber conveyance by an automatic machine. According to the present invention, the hardness can be increased by adding magnesia, so that the workability at the time of manufacturing a capacitor can be improved.

Regarding the compression set, the value is lower in the conventional example 1 of the peroxide vulcanization and the embodiment of the present invention than in the conventional example 2 of the resin vulcanization. If this value is high, it is difficult to transmit the pressure from the horizontal diaphragm to the inside when the capacitor is sealed at the time of manufacturing, so that the sealing may be defective. It can be seen that the example of the present invention can maintain the same value as the conventional example 1 even if the magnesia compounding amount is changed. Next, using the rubbers produced in Examples 1 to 7 and Conventional Examples 1 and 2 as the sealing body, 25V 10 μF (φ5 mm × 11 mm
The capacitor of L) was produced.

[0017]

[Table 2]

105 ° C. 5000 with this electrolytic capacitor
A time life test was conducted. The electrolyte used was a solution of 15 parts of tetramethylammonium phthalate dissolved in 100 parts of γ-butyrolactone and a specific resistance of 100Ω.
cm. FIG. 1 shows a sectional view showing the structure of the produced capacitor. Reference numeral 1 is a capacitor element, 2 is an elastic sealing body, 3 is a metal case, and 4 is a lead wire. Table 2 shows the amount of weight loss of the capacitor after 5000 hours and the state of electrolyte leakage, and FIG. 2 shows the weight change during the life test. The conventional example 1 of peroxide vulcanization has a larger weight reduction than the conventional example 2 of resin vulcanization. That is, the gas permeation amount is large and the airtightness is poor, but the weight reduction is improved as the compounding amount of magnesia is increased in Examples 1 to 5. But 30
When it exceeds the weight part, the weight loss tends to increase a little.

Regarding leakage of electrolyte (liquid leakage), about half of the electrolyte leaked in Conventional Examples 1 and 2, whereas no liquid leak occurred in Examples 1-7. Although not shown in Table 2, if the magnesia blending amount is less than a part, the effect on liquid leakage is reduced, so the magnesia blending amount is preferably 1 part or more. Figure 3
Shows the tan δ and the capacity change (ΔC) in the life test. It can be seen from FIG. 2 that the smaller the weight loss, the smaller the characteristic change. If the amount of magnesia is more than 50 parts with respect to 100 parts of the rubber polymer, the processability during rubber production will be poor and the airtightness will also decrease.
Less than or equal to part is desirable.

[0020]

As described above, according to the present invention, heat resistance, airtightness and chemical resistance can be greatly improved.
It is possible to provide an electrolytic capacitor having a long life and high reliability even at high temperatures.

[Brief description of drawings]

FIG. 1 is a sectional view of a capacitor according to an embodiment of the present invention.

FIG. 2 is a diagram showing changes in capacitor weight in a 105 ° C. 5000-hour life test.

FIG. 3 is a graph showing changes in the characteristics of capacitors in a 105 ° C. 5000-hour life test.

[Explanation of symbols]

 1 Capacitor element 2 Elastic sealing body 3 Metal case

Claims (2)

[Claims] 1. An electrolytic capacitor in which a capacitor element impregnated with an electrolytic solution is housed in a metal case and sealed with an elastic sealing body, wherein the elastic sealing body is a main component of a ternary copolymer of isobutylene, isoprene and divinylbenzene. An electrolytic capacitor characterized in that it is made of a material obtained by mixing at least magnesia with it and vulcanizing it with peroxide. 2. The electrolytic capacitor according to claim 1, wherein the compounding amount of the magnesia is 1 to 50 parts with respect to 100 parts of the main polymer.