JPH0239085B2 - DENKAIKONDENSA - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrolytic capacitor, and aims to improve the performance of the capacitor by improving the sealing body. In general, electrolytic capacitors have a dielectric film formed by anodization on the surface of a metal with valve action, such as aluminum or tantalum, as an anode electrode, and a separator impregnated with electrolyte between the opposing cathode electrode and the anode electrode. The structure is such that a capacitor element is formed by winding the capacitor element, a sealing body is attached to the capacitor element, the capacitor element is housed in a case, and the opening of the case is then tightly wound and sealed. In recent years, as electronic devices have become smaller and more compact, changes in the atmosphere in which capacitors are used, particularly the rise in ambient temperature, have been noticeable. Furthermore, the environments in which devices are placed are diverse, and they are less likely to be placed in high-temperature atmospheres. Therefore, in response to such environmental changes, the demand for improved heat resistance of electrolytic capacitors has inevitably increased. However, since electrolytic capacitors generally use an electrolyte, the evaporation rate of the electrolyte increases as the temperature rises, and the pressure inside the case increases rapidly, which can lead to premature activation of the explosion-proof valve or rupture of the capacitor. Seen a lot. For this reason, it is essential to improve the heat resistance of the electrolytic solution, that is, to reduce the evaporation rate in a high-temperature atmosphere, but there is a limit to this reduction due to unavoidable phenomena such as reaction with the dielectric oxide film. Therefore, as a means to compensate for this, a method is used in which the evaporative electrolyte is permeated and dissipated through a sealing body. Silicone rubber has conventionally been used as a material that has a large effect on this, and a large effect has been obtained in combination with a low-evaporation electrolyte. Moreover, silicone rubber has great heat resistance and can withstand long-term use without hardness changes or embrittlement up to about 200°C.
However, as is well known, the gas permeability of silicone rubber is quite high, and depending on the composition of the electrolyte, the permeation rate may be too high to prevent premature deterioration of properties over time. On the other hand, ethylene propylene rubber is also frequently used as a material with excellent heat resistance. This ethylene propylene rubber can withstand long-term use up to about 150℃ and has relatively little change in hardness. However, it has a low gas permeability and is highly airtight, but it is difficult to use when using large capacitors or electrolytes with a high evaporation rate. In this case, the sealing body is pushed up as the internal pressure increases, resulting in an unfavorable appearance. The present invention was made in view of the current situation, and uses styrene ethylene butylene styrene elastomer as the rubber material of the sealing body to provide the above-mentioned advantages and at the same time eliminate the disadvantages. The present invention will be explained based on specific embodiments. Table 1 shows, as an example of gas permeability, the oxygen gas permeability measured for five samples each of styrene ethylene butylene styrene elastomer, silicone rubber, and ethylene propylene rubber.

[Table] Table 2 also lists the same three types of materials as in Table 1.
A comparison with the initial value of hardness measured after being left at ℃ for 2000 hours and then returning to room temperature is shown.

[Table] Next, as shown in Table 3, a sealing body made of each material was sealed into the opening of a case housing a capacitor element impregnated with an electrolyte with a rating of 50WV and 470μF to form an electrolytic capacitor (16mmφ x 30.5mml). produced,
The figure shows the capacitance change, tonδ change, and appearance change when a life test was conducted at 125°C and rated voltage was applied for 2000 hours. In each case, the number of samples was 10, and for ethylene propylene rubber, there were 6 samples except for the one in which the explosion-proof valve was activated.
The average value of 1, others are the average of 10.

[Table] As is clear from these test results, the styrene ethylene butylene styrene elastomer of the present invention not only has excellent physical properties, but also exhibits excellent heat resistance when used as a sealing member for an electrolytic capacitor. Furthermore, there is no need for a vulcanization process, and scraps can be reused, contributing to cost reduction. In addition, in the above-mentioned examples, only the case of single rubber packing was described, but it can also be used for rubber materials for bonding with resin base materials such as phenol, rubber materials for O-rings provided around the sealing body, etc. A similarly large effect was obtained. As described above, the present invention greatly contributes to improving the performance and reducing costs of electrolytic capacitors, and has extremely great industrial value.

Claims (1)

[Claims] 1. An electrolytic capacitor characterized in that a sealing body using styrene ethylene butylene styrene elastomer as a rubber material is sealed to an opening of a case housing a capacitor element.