JPH0821527B2 - Electrolytic capacitor - Google Patents

Description

The present invention relates to a highly reliable electrolytic capacitor having an improved sealing body.

(Prior Art) An electrolytic capacitor is a capacitor element in which an anode foil and a cathode foil are wound with a separator paper interposed and impregnated with an electrolytic solution,
The capacitor element impregnated with the electrolytic solution is housed in a metal case, and the metal case is sealed by an elastic sealing body.

Conventionally, the electrolytic solution of an electrolytic capacitor is one in which ethylene glycol is the main solvent is widely used, and as the elastic sealing body, natural rubber (NR), styrene butadiene (SBR), ethylene propylene terpolymer (EPT), etc. The material has been used.

In recent years, reliability has come to be required in a wide temperature range, and N, N-dimethylformamide (DMF) and γ-butyrolactone (GBL) have been used as a solvent for an electrolytic solution. However, DMF and GBL have high volatility, and the electrolyte solution permeates as vapor in the conventional elastic sealing body, so that the reliability cannot be maintained.

Therefore, isobutylene / isoprene rubber (IIR), which is more sensitive, has come to be used. However, IIR has a problem in heat resistance. IIR vulcanization methods include sulfur vulcanization, quinoid vulcanization, resin vulcanization, etc. Of these, resin vulcanization is superior in heat resistance.
The IIR also has a drawback that it becomes soft when left in high temperature for a long time.

(Problems to be Solved by the Invention) Recently, in order to improve the heat resistance of IIR, JP-A-55-158
As disclosed in Japanese Patent Laid-Open No. 62-62, there has been proposed a crosslinked IIR obtained by peroxide vulcanizing a ternary copolymer of isobutylene, isoprene and divinylbenzene as a polymer.

This crosslinked IIR has better heat resistance than resin vulcanized ones. However, on the contrary, since the most important airtightness is inferior, there is a drawback that when a capacitor test is performed at a high temperature for a long time, the characteristic 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, regarding the electrolytic capacitor that combines the electrolyte using this quaternary ammonium salt and the sealing body made of cross-linked IIR, when the life test at high temperature is performed, the electrolytic solution leaks from the vicinity of the lead wire through hole of the sealing body. I found a new problem that it will come.

The present invention has been made in view of the above problems,
An object of the present invention is to provide a highly reliable electrolytic capacitor that can achieve high temperature and long life by using an elastic sealing body having excellent heat resistance, airtightness and chemical resistance.

(Means for Solving the Problems) In 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 and This is a material in which a three-component copolymer of divinylbenzene is used as a main polymer, and at least magnesia is added to the material to be peroxide vulcanized, and the electrolytic solution uses γ-butyrolactone as a main solvent and a quaternary organic acid. It is characterized by using an ammonium salt as a solute.

The compounding amount of magnesia is preferably 1 to 50 parts with respect to the main polymer.

Further, as the polymer of 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.

(Function) When a three-component copolymer of isobutylene, isoprene, and divinylbenzene is used as a polymer for peroxide vulcanization, the double bond of divinylbenzene is dissolved and a C—C bond is crosslinked, so that it is more difficult than conventional IIR. Heat resistance is improved.

When magnesia (MgO) is blended with this crosslinked IIR, it acts as a vulcanization accelerator 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.

Crosslinks when in contact with an electrolyte containing quaternary ammonium salt
Even with IIR, the airtightness deteriorated due to swelling, and when a long-term capacitor life test was performed, the electrolyte solution leaked out 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 also exerts an action of making the crosslinked IIR alkaline in addition to the action described above, according to the present invention, heat resistance,
It is possible to provide an elastic sealing body having good airtightness and chemical resistance. Actually, when 2 g of rubber was made into powder and immersed in 100 g of pure water and extracted with boiling water for 30 minutes, the pH was measured and 6.78 for magnesia unblended, 10 parts magnesia for 100 parts polymer What I did was 9.99.

(Examples) Hereinafter, the present invention will be described in detail 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 IIR rubber.

[Example 2] In the same manner as in Example 1, 100 parts of the polymer was mixed with 5 parts of magnesia 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 an IIR rubber.

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, 100 parts of the polymer and 30 parts of magnesia were compounded 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 an IIR rubber.

Example 7 In the same manner as in Example 1, 50 parts of magnesia was added to 100 parts of the polymer 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] An IIR rubber was prepared by vulcanizing an isobutylene or isoprene polymer with an alkylphenol-formaldehyde resin.

Table 1 shows the compounding and physical properties of the prepared IIR rubber.

The hardness is measured by JIS K6301 spring type hardness test A type, and the compression set is 25% compressed according to the JIS K6301 compression set test, and then left in a constant temperature bath at 100 ° C for 70 hours. It was calculated by the following formula.

Here, t _θ 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.

It can be seen from Table 1 that the hardness increases as the magnesia content is increased. If the hardness is low, problems may occur in the rubber threading process of the lead wire during manufacturing of the capacitor, and problems may occur in the rubber conveyance by the automatic machine during assembly. 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 values of Conventional Example 1 of peroxide vulcanization and Example of the present invention are lower than those of Conventional Example 2 of 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. In the example of the present invention, even if the magnesia compounding amount was changed, the conventional example 1
It can be seen that the same value as can be maintained.

Next, using the rubbers produced in Examples 1 to 7 and Conventional Examples 1 and 2 as a sealing body, a 25V 10 μF (φ5 mm × 11 mmL) capacitor was produced.

A life test was performed on this electrolytic capacitor at 105 ° C. for 5000 hours. The electrolytic solution used was a solution of 15 parts of tetramethylammonium phthalate dissolved in 100 parts of γ-butyrolactone and a specific resistance of 100 Ωcm. FIG. 1 shows a cross-sectional view showing the structure of the manufactured 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, although the gas permeability is large and the airtightness is poor, Example 1
Weight loss improves with increasing magnesia loading up to -5. However, if the amount exceeds 30 parts by weight, the weight loss tends to increase a little. Regarding leakage of the electrolytic solution (liquid leakage), about half of the conventional examples 1 and 2 leaked the liquid, whereas the liquid leakage did not occur in Examples 1 to 7. Although not shown in Table 2, if the magnesia compounding amount is less than a part, the effect on liquid leakage decreases, so the magnesia compounding amount is preferably 1 part or more.

Figure 3 shows tan δ and capacity change (Δ
C) is shown. It can be seen from FIG. 2 that the smaller the weight loss is, the smaller the characteristic change is.

If the content 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 be deteriorated, so 50 parts or less is desirable.

(Effects of the Invention) As described above, according to the electrolytic capacitor of the present invention,
By using the above-mentioned elastic sealing body, it is possible to effectively prevent leakage of the electrolytic solution in an electrolytic solution of a solvent having excellent heat resistance and airtightness, and particularly high volatility of γ-butyrolactone,
It is possible to provide a long-life and highly reliable electrolytic capacitor.

[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 a change in capacitor weight in a 105 ° C. 5000 hour life test, and FIG. 3 is a diagram showing a characteristic change in a capacitor in a 105 ° C. 5000 hour life test.

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 polymer of a three-component copolymer of isobutylene, isoprene and divinylbenzene. And at least magnesia is added to the material to be peroxide vulcanized, and the electrolytic solution contains γ-butyrolactone as a main solvent and a quaternary ammonium salt of an organic acid as a solute. Electrolytic capacitor. 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.