JPS63232409A - 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, in which a capacitor element is made by combining a J:J bar foil and a cathode foil together with a separator, are made of a valve metal such as aluminum, and the capacitor element is generally impregnated with a driving electrolyte, The capacitor element is housed in a metal case or a case made of synthetic wood, and has a sealed structure.

Conventionally, the electrolytic solution for driving such electrolytic capacitors uses a polar organic solvent such as ethylene glycol as the main solvent, and an electrolytic solution in which a salt such as an ammonium salt of a saturated organic acid that does not corrode the metal electrodes is dissolved. A liquid 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 (Japanese Unexamined Patent Publication No. 7564/1983).

[Problems to be Solved by the Invention] However, in the electrolytic solution disclosed in Japanese Patent Publication No. 58-13019, it is an indicator of electrical resistance, but in this case corrosion of the cathode foil and dissociated ammonia (NHff )
There has been a problem in that the characteristics of the capacitor deteriorate at high temperatures due to the transpiration of , especially the change in the tangent of the loss angle (tan δ) is large. It also has high conductivity (low electrical resistance),
JP-A-59-78522 discloses 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 as an electrolytic solution that is stable at high temperatures. According to the example of
There was a problem that it was insufficient from the point of view of (m).

Furthermore, when using γ-butyrolactone and ethylene glycol as shown in the above-mentioned JP-A-54-7564 as a mixed solvent, 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.

It is an object of the present invention to solve these problems and provide 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 above problems, the present invention is characterized by using a driving electrolyte prepared by dissolving a quaternary ammonium salt of succinic acid in a polar organic solvent. The present invention provides electrolytic capacitors.

As the quaternary ammonium salt of succinic acid used in the present invention, those having the alkyl group (R) of the quaternary ammonium represented by the general formula R4N" have 1 to 10 carbon atoms, particularly those having 1 to 4 carbon atoms. Preferred examples include tetramethylanthonium succinate, tetraethylammonium succinate, tetrapropylammonium succinate, and tetrabutylammonium succinate.

In the present invention, quaternary ammonium salts of succinic acid are used, including other amine salts of succinic acid.

The content (concentration) of the quaternary ammonium salt of succinic acid used in the present invention in the electrolyte composition can be selected as appropriate, but considering that the specific resistance is the lowest in the state of a saturated solution, it is 1 to 50. Weight % is suitable, and in order to obtain good high temperature stability, 5 to 40 weight % is particularly suitable.

In order to solve the above problems, the polar organic solvent used in the present invention includes at least Y-butyrolactone and 3-alkyl-1,3-oxycylidin-2-one (hereinafter referred to as A,
(referred to as O,).

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 preferably used. Specific examples of preferred miscible solvents include N,N-dimethylformamide, dimethylformamide, 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. The two solvents may be used alone or in a combination of two or more as appropriate. used.

In the present invention, in order to obtain a driving electrolyte containing a quaternary ammonium salt of succinic acid, the quaternary ammonium salt may be added to a polar organic solvent. This quaternary ammonium salt may be produced by one reaction of substances that can be produced.

In the present invention, it is not necessarily necessary to include water in the electrolytic solution, but it is effective to lower the specific resistance. However, if the 4T amount of water is increased beyond a certain limit, it is preferable that the water content be as small as possible for the purpose of generating internal gas. Therefore, depending on the purpose of use of the electrolytic capacitor, the water content in the electrolyte composition is preferably in the range of 0.1 to 20% by weight, and 0.5 to 20% by weight.
A range of 15% by weight is more preferred.

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, the stiff straw is rolled into a cylindrical shape as a capacitor element, and a driving electrolyte is applied to this element. Impregnate. The amount of electrolytic solution impregnated is preferably 50 to 300% by weight based on the separator. 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.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

A 10% aqueous solution of tetraalkylammonium hydroxide (carbons & 1 to 3 of the alkyl group) and succinic acid are mixed in equal mole numbers to dissolve the succinic acid, and then water is removed using an evaporator to dissolve the succinic acid. A quaternary ammonium salt of an acid was generated, and a predetermined amount of these salts were dissolved in a polar organic solvent as a solute to obtain the electrolyte solutions of Examples 1 to 8. electrolyte p
I adjusted !I4 so that i( is 5 to 7.

Using these electrolytes, we manufactured an electrolytic capacitor (rated 25V, 470μF) 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. Comparative Examples 1 to 3 also show cases where solutes other than the quaternary ammonium salt of succinic acid were used.
An electrolytic capacitor was 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, 0. and E, O, are the aforementioned A, 0. Table 2 shows the low-temperature characteristics of electrolytic capacitors in which the alkyl group is methyl and ethyl. The electrolytic capacitors were the same as those described above, and the number of samples was 10 each. The measurement frequency is 120Hz. In the table, ΔC/C20°C represents the rate of change in capacity at 20°C, and Z/Z 20°C represents the impedance ratio at 20°C.

As can be seen from the first person, in the comparative example, the change in the tangent of the loss angle is large in the high temperature load test, whereas in the example, this change can be made small.

Furthermore, as can be seen from Table 2, in the comparative example, the rate of change in ΔC/C20″c and Z/ZZ 0°C is large in the low-temperature characteristics, whereas the example aims to reduce this rate of change. It is something that can be done.

[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 be provided.

Claims (3)

[Claims] (1) A driving electrolyte is used, which is obtained by dissolving a quaternary ammonium salt of succinic 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 succinic 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.