JPH0428215A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To make it possible to achieve a long lifetime at high temperature by a method wherein elastic hole-sealing material, having excellent heat-resisting property, airtightness and chemical-resisting property, is used. CONSTITUTION:An electrolyte-impregnated capacitor element is housed in a metal case, and the element is airtightly sealed by an elastic sealing material. In this electrolytic capacitor, a peroxide-vulcanized material, obtained by compounding at least magnesia in the main polymer of 3-component copolymer consisting of isobutylene, isoprene and divinylbenzene, is used as the above- mentioned elastic sealing material. The desirable quantity of compounding of magnesia is 1 to 50 parts against 100 parts of the main polymer. Also, it is desirable that the electrolyte is formed using gamma-butyrolactone as the main solvent and a quaternary ammonium salt of organic acid as a solute.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly reliable electrolytic capacitor with an improved sealing body.

(Prior art) Electrolytic capacitors are made by impregnating an electrolyte into a capacitor element made by winding an anode foil and a cathode foil with separator paper interposed between them.The capacitor element impregnated with the electrolyte is housed in a metal case. It is formed by sealing the case with an elastic sealing body.

Conventionally, electrolytes with ethylene glycol as the main solvent have been widely used as electrolytic solutions for electrolytic capacitors, and as elastic sealants, natural rubber (NR), 1-styrene butadiene (SBR), and ethylene propylene terpolymer (EPT) have been widely used.
) and other materials have been used.

In recent years, reliability over a wide temperature range has become required, and N,N-dimethylbormamide (DMF) and T-butyrolactone (GBL) have come to be used as solvents for electrolyte solutions.

However, DMF and GBL are highly volatile, and with conventional elastic sealers, the electrolyte passes through as vapor, making it impossible to maintain reliability.

Therefore, isoptylene/isoprene rubber (IIR), which has higher airtightness, has come to be used.

However, TIP has a problem with heat resistance. IIR vulcanization methods include sulfur vulcanization, quinoid vulcanization, resin vulcanization, etc. Among these, resin vulcanization is superior in heat resistance, but even resin vulcanization 11R can be used for long periods of time at high temperatures. It had the disadvantage that it would soften if left for a long time.

(Problem to be solved by the invention) Recently, in order to improve the heat resistance of ITR,
As shown in Publication No. 15862, a three-component copolymer of isoptylene, isoprene, and divinylbenzene is used as a polymer and is crosslinked by peroxide vulcanization! 1R is proposed.

This crosslinked FIR has better heat resistance than resin-vulcanized FIR. However, since they are inferior in the most important air-tightness property, they have the disadvantage that when capacitor tests are conducted at high temperatures and for long periods of time, changes in properties due to permeation and dissipation of electrolyte become large.

In addition, it is necessary to use a highly reliable electrolyte for capacitors designed for high-temperature, long-life use, and a low resistivity electrolyte made of a combination of T-butyrolactone and a quaternary ammonium salt of an organic acid is being used. It has become to. However, these 4
For electrolytic capacitors that combine an electrolytic solution using grade ammonium salt and a sealing body made of cross-linked ITR, when a life test is performed at high temperatures, the electrolytic solution leaks from near the lead wire through hole of the sealing body. I found a new problem.

The present invention was made in view of the dual problems.
An object of the present invention is to provide a highly reliable electrolytic capacitor that can achieve long life at high temperatures by using an elastic sealing body with excellent heat resistance, airtightness, and chemical resistance.

(Means for Solving the Problems) In the present invention having a dual purpose, in an electrolytic capacitor in which a capacitor test impregnated with an electrolytic solution is housed in a metal case and sealed with an elastic sealing body, the elastic sealing body is made of isoptylene, It is characterized by being made of a material in which the main polymer is a three-component copolymer of isoprene and divinylbenzene, and at least magnesia is blended therein and peroxide vulcanized.

The blending amount of magnesia is 1 to 5 with respect to the main polymer.
Preferably it is 0 parts.

The elastic sealant has chemical resistance even to an electrolytic solution containing γ-butyrolactone as a main solvent and a quaternary ammonium salt of an organic acid as a solute.

In addition, as the polymer for the elastic sealing body, the three-component copolymer mentioned above may be used alone, but it is also possible to use a blend with ethylene propylene terpolymer (EPDM), etc., which can also be vulcanized with perchloride. effect can be obtained.

(Function) A three-component copolymer of isoptylene, isoprene, and divinylbenzene is cured with peroxide as a polymer.The double bonds of divinylbenzene are dissolved to form a CC bond crosslink, making it more heat resistant than conventional simple IIR. Improves sex.

When magnesia (MgO) is blended with this crosslinked 11R, it acts as a vulcanization accelerator and the crosslinking density is increased, thereby improving airtightness. Moreover, when the amount of magnesia increases, it acts like a filler, so it is possible to increase the hardness of the rubber.

Cross-linking occurs when it comes into contact with an electrolyte containing quaternary ammonium salt 1
Even at 1R, the capacitor swelled and the airtightness deteriorated, and when a long-term capacitor life test was performed, the electrolyte sometimes leaked from the vicinity of the lead wire through-hole. In order to prevent this, the inventors have discovered that it is good to make the sealing body alkaline. Since the addition of magnesia has the effect of making the crosslinked IIR alkaline in addition to the above-mentioned effect, the present invention can provide an elastic sealing body with good heat resistance, airtightness, and chemical resistance. Actually, when we measured the pH after powdering 2g of rubber and immersing it in 100g of pure water and extracting it with boiling water for 30 minutes, it was 6.78 for the one without magnesia, but 100 parts of polymer had 10% magnesia. The score for the part was 9.99.

(Example) Hereinafter, the present invention will be described in detail based on Examples.

[Example 1] Two parts of magnesia was blended with 100 parts of a polymer consisting of a three-component copolymer of isoptylene, isoprene, and divinylbenzene, and the mixture was peroxide vulcanized with dicumyl peroxide to produce a TTR rubber.

(Example 2) In the same manner as in Example 1, 5 parts of magnesia was blended with 100 parts of polymer to produce an IIR rubber.

[Example 3] In the same manner as in Example 1, 10 parts of magnesia was blended with 100 parts of polymer to produce an IIR rubber.

[Example 4] In the same manner as in Example 1, 20 parts of magnesia was blended with 100 parts of polymer to produce an IIR rubber.

[Example 5] In the same manner as in Example 1, 30 parts of magnesia was mixed with 100 parts of polymer to produce an IIR rubber.

[Example 6] In the same manner as in Example 1, 40 parts of magnesia was blended with 100 parts of polymer to produce an IIR rubber.

[Example 7] ITR was prepared by peroxide vulcanization of a polymer consisting of a three-component copolymer of isoptylene, isoprene, and divinylbenzene using dicumyl peroxide.

[Conventional Example 2] Isoptylene and isoprene polymers were vulcanized with alkylphenol formaldehyde resin to produce (1) IR rubber.

Table 1 shows the formulation and physical properties of the IIR rubber produced.

Hardness is JIS K630] Spring type hardness test A
The compression set is measured by the shape, and the compression set is 1.
It was left in a constant temperature bath at 00°C for 70 hours and calculated using the following formula.

The thickness after the experiment, t2, is the thickness of the spacer.

According to Table 1, it can be seen that by increasing the amount of magnesia blended, the hardness increases. If the hardness is low, problems may occur during the rubber lead wire threading process during capacitor manufacturing, or problems may occur when the rubber is conveyed by automatic machines during assembly. According to the present invention, since the hardness can be increased by blending magnesia, workability during capacitor manufacturing can be improved.

Regarding compression set, conventional example 1 of peroxide vulcanization and the example of the present invention have lower values than conventional example 2 of resin vulcanization. When this happens, it is difficult for the pressure due to the horizontal drawing to be transmitted to the inside, which may result in poor sealing, so the value should be smaller.
Equivalent to ■Next, using the rubber produced in Examples 1 to 7 and Conventional Example 1.2 as a sealant, 25V10μF (φ5mm
mL) capacitor was manufactured.

Table: A life test of 5,000 hours at 105°C was conducted on this electrolytic capacitor. The electrolytic solution used was one in which 15 parts of tetramethylammonium phthalate was dissolved in 100 parts of T-butyrolactone, and had a specific resistance of 100 Ωcm. FIG. 1 shows a cross-sectional view showing the structure of the fabricated capacitor. 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 50
Figure 2 shows the weight loss of the capacitor after 00 hours and the leakage of the electrolyte, and Figure 2 shows the weight change during the life test.

Conventional Example 1 using peroxide vulcanization has a greater weight reduction than Conventional Example 2 using resin vulcanization. That is, although the amount of gas permeation is large and the airtightness is poor, weight loss is improved as the amount of magnesia is increased in Examples 1 to 5. However, when the amount exceeds 30 parts by weight, there is a tendency for the weight loss to increase slightly. In addition, regarding electrolyte leakage (liquid leakage), conventional example 1
In Examples 1 to 2, about half leaked.
7, no leakage occurred. Although not shown in Table 2, if the amount of magnesia added is less than a part, the effect against liquid leakage will be reduced, so it is desirable that the amount of magnesia added is 1 part or more.

FIG. 3 shows t, an δ, and capacitance change (ΔC) in the life test. In FIG. 2, it can be seen that the smaller the weight loss, the smaller the change in characteristics.

The amount of magnesia to be blended is desirably 50 parts or less per 100 parts of the rubber polymer, since if it exceeds 50 parts, the processability during rubber production will be poor and the airtightness will also be reduced.

(Effects of the Invention) As described above, by using the sealing body of the present invention, the heat resistance, airtightness, and chemical resistance of electrolytic capacitors can be significantly improved, resulting in long life and reliability even at high temperatures. We can provide high electrolytic capacitors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a capacitor according to an embodiment of the present invention;
FIG. 2 is a diagram showing changes in capacitor weight during a 5,000-hour life test at 105°C, and FIG. 3 is a diagram showing changes in capacitor characteristics during a 5,000-hour life test at 105°C.

Claims (3)

[Claims] 1. In 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, the elastic sealing body has a three-component copolymer of isoptylene, isoprene, and divinylbenzene as a main polymer, and at least magnesia. An electrolytic capacitor characterized by being made of a material that is compounded and vulcanized with peroxide. 2. The blending amount of the magnesia is 100% of the main polymer
Claim 1 characterized in that the amount is 1 to 50 parts.
Electrolytic capacitors listed. 3. The electrolyte contains γ-butyrolactone as a main solvent,
3. The electrolytic capacitor according to claim 1, wherein the solute is a quaternary ammonium salt of an organic acid.