JPS63221608A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor using a novel driving electrolyte.

[Prior Art] Electrolytic capacitors are made by winding an anode foil and a cathode foil made of a valve metal such as aluminum together with a separator to form a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and the capacitor element is made of a metal case made of aluminum or the like. Synthesis N
The capacitor and IL are housed in a 4m case with a sealed structure.

Conventional electrolytic solutions for electrolytic capacitors include polar organic solvents such as ethylene glycol as the main solvent, and electrolytic solutions in which salts such as ammonium salts of saturated organic acids that do not corrode metal electrodes are dissolved. is generally used (Japanese Patent Publication No. 58-13019). It is also known to use a mixed solvent of γ-butyrolactone and ethylene glycol as a solvent for the electrolyte. (
JP-A No. 54-7564).

[Problems to be Solved by the Invention] However, in the electrolytic solution disclosed in Japanese Patent Publication No. 58-13019, 1 to 3. OCK-break%
However, in this case, the characteristics of the capacitor deteriorate at high temperatures due to corrosion of the cathode foil and transpiration of dissociated ammonia (NH3), especially changes in the tangent of the loss angle (tan δ). The problem was that it was large. In addition, as an electrolytic solution that has high conductivity (low electrical resistance) and is stable at high temperatures, the use of an electrolytic solution in which a quaternary ammonium salt of a saturated chain dicarboxylic acid is dissolved in a polar organic solvent has been disclosed in JP-A No. 59-78522. Disclosed in the official gazette. However, according to the examples in the same publication, the electrolyte
The problem was that the degree was 9.4 mS/cm at most, which was insufficient compared to the currently required level (12 to 25 mS/cm). Furthermore, when γ-butyrolactone and ethylene glycol are used as a mixed solvent as seen in the above-mentioned JP-A-54-7564, the viscosity of ethylene glycol increases at low temperatures, which improves the low-temperature characteristics of the capacitor. The problem was that it was small.

The present invention solves these problems and provides an electrolytic capacitor that uses a driving electrolyte that has low electrical resistance (high conductivity), excellent low-temperature characteristics, and excellent high-temperature stability. With the goal.

[Means for Solving the Problems] In order to solve the problems mentioned above, the present invention uses a driving electrolyte prepared by dissolving a quaternary ammonium salt of pyromellitic acid in a polar organic solvent. The present invention provides an electrolytic capacitor with special characteristics.

The quaternary ammonium salt of pyromellitic acid used in the present invention is one having a quaternary ammonium represented by the general formula R4N'' with an alkyl group (R) having 1 to 10 carbon atoms, especially one having 1 to 4 carbon atoms. can be suitably used 1
For example, pyromeri.

Examples include tetramethylammonium acid, tetraethylammonium pyromellitate, tetrapropylammonium pyromellitate, and tetrabutylammonium pyromellitate.

In the present invention, it is preferable to use a quaternary ammonium salt of pyromellitic acid because if pyromellitic acid is another amine salt, the electrolyte will have low conductivity and the product will have a large tan δ. That's because there isn't.

Inclusion of the quaternary ammonium salt of pyromellitic acid used in the present invention in the electrolyte composition! l (1 degree) can be selected as appropriate, but considering that the resistivity is the lowest when it is in a saturated solution state, 1 to 50% is appropriate, and in particular, in order to obtain good high temperature stability, 5 to 40% is suitable.

The polar organic solvent used in the present invention is at least γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one (hereinafter referred to as A,
0. ).

Here, the alkyl group includes methyl, ethyl, propyl, etc. Among them, for improving low temperature characteristics,
Methyl and ethyl are preferred. Furthermore, any polar organic solvent commonly used in electrolytic capacitors can be used as the solvent to be mixed, including amides, lactones, etc.
Glycols, sulfur compounds or carbon salts can be suitably used. Specific examples of preferred miscible solvents include N,N-dimethylformamide, N-methylformamide, β-butyrolactone, γ-valerolactone, N
- Examples include methylpyrrolidone, ethylene glycol, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, dimethyl sulfoxide, propylene carbonate, ethylene cyanohydrin, etc. These solvents may be used individually or in multiple combinations as appropriate. used.

In the present invention, in order to obtain a driving electrolyte containing a quaternary ammonium salt of pyromellitic acid, this quaternary ammonium salt may be added to a polar organic solvent. The quaternary ammonium salt may be produced by reacting substances capable of producing the salt.

In the present invention, it is not necessary to include water in the electrolytic solution, but it is effective to lower the specific resistance. However, if the amount of water containing 4T exceeds a certain limit, it will increase the swelling of the case of the electrolytic capacitor due to the generation of internal gas and the corrosion of the electrode foil. It is preferable that the water content be as small as possible. Therefore, depending on the purpose of use of the electrolytic capacitor, the water content in the electrolyte composition should be 0.
The range of 1 to 20% by weight is preferable, and the range of 0.5 to 15% by weight is more preferable.

The electrolytic capacitor of the present invention includes various types of capacitors. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode are separated by a suitable separator such as paper, and these are wound into a cylindrical shape to form a capacitor element, and this element is impregnated with a driving electrolyte. let The electrolyte content uffl is as follows for the separator:
Preferably it is 50 to 300% by weight. The element impregnated with the electrolyte is housed in a case made of corrosion-resistant metal, synthetic resin, or the like, and has a sealed structure.

[Example] The present invention will be explained in detail based on Examples and Comparative Examples below. A 10% aqueous solution of tetraalkylammonium hydroxide (carbons a1 to a3 of the alkyl group) and pyromellitic acid were mixed in equal moles. After dissolving the pyromellitic acid by mixing the mixture so that the pyromellitic acid is dissolved, water is removed using an evaporator to produce a quaternary ammonium salt of pyromellitic acid. The electrolytes of Examples 1 to 9 were prepared.

Make sure the pH of the electrolyte is between 5 and 7! I L/ta.

Using these electrolytes, we manufactured an electrolytic capacitor (rated 16V, 330μF) with aluminum electrodes, and conducted a high-temperature load test (rated voltage applied, 125℃, 1000 hours).
The changes in the tangent (tan δ) of the loss angle were measured, and the results are shown in Table 1. In addition, Comparative Examples 1 to 4 are cases in which a solute other than the quaternary ammonium salt of pyromellitic acid is used. Electrolytic capacitors were manufactured in the same manner as in the example, and a high temperature load test was conducted under the same conditions as in the example. The results are shown in Table 1.

In Table 1, M, O, and E, 0. is the above-mentioned A, 0. represents methyl and ethyl alkyl groups, respectively.

Table 1 shows examples of electrolyte composition and high-temperature load test water, and Table 2 shows the low-temperature characteristics of electrolytic capacitors. The electrolytic capacitors were the same as those described above, and the number of samples was 10 each. The measurement frequency is 120Hz. ΔC/C20℃ in the table is the rate of change in capacity at 20℃, Z/22
0°C indicates the impedance ratio with respect to 20°C.

As can be seen from Table 1, the average value for n=10, the change in the tangent of the loss angle is large in the comparative example in the high temperature load test, whereas this change can be made small in the example.

Furthermore, as can be seen from Table 2, in the comparative example, the rate of change at 80/C20℃ and Z/Z 20℃ is large in low temperature characteristics, whereas in the example it is possible to reduce this rate of change. It is possible.

[Effects of the Invention] As explained above, the present invention provides an electrolytic capacitor with excellent low-temperature characteristics and excellent high-temperature stability with small change in tangent of loss angle (tan δ) under high-temperature conditions. can do.

Claims (3)

[Claims] (1) The use of a driving electrolytic solution made by dissolving a quaternary ammonium salt of pyromellitic acid in a polar organic solvent consisting of γ-butyrolactone and 3-alkyl-1,3-oxazolidin-2-one. electrolytic capacitor. (2) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of pyromellitic acid in the driving electrolyte is 1 to 50% by weight. (3) The electrolysis according to claim 1 or 2, wherein the alkyl group (R) of the quaternary ammonium represented by the general formula R_4N^+ has 1 to 10 carbon atoms. capacitor.