JPS63219118A - 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 Use] 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 winterizing anode foil and 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 then the capacitor element is impregnated with a metal case made of aluminum or the like. The capacitor element is housed in a synthetic resin case and has a sealed structure.

Conventionally, the driving electrolyte for such an electrolytic capacitor is an organic solvent such as ethylene glycol, and an organic solvent such as an ammonium salt of a saturated organic acid.
An electrolytic solution containing a dissolved salt that does not corrode metal electrodes is generally used (Japanese Patent Publication No. 13019/1983). 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. 54-7564).

[Problems to be Solved by the Invention] However, in the electrolytic solution disclosed in Japanese Patent Publication No. 58-13019, 1 to 30% by weight is added in order to lower the tangent of loss angle (tan δ), which is an index of electrical resistance. However, in this case, the properties of the capacitor at high temperatures deteriorate due to corrosion of the cathode foil and dissipation of dissociated ammonia (NH3), especially the loss angle tangent (
There was a problem in that the change in tan δ) 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 was disclosed in JP-A-59.
It is disclosed in Japanese Patent No.-78522. however,
According to the examples in the same bulletin, the electrolyte has a conductivity of 9.4 mS/cm at most, which is insufficient compared to the currently required level (12 to 25 mS/cm). There was a problem. Furthermore, as a mixed solvent, γ
- When butyrolactone and ethylene glycol are used, there is a problem in that the viscosity of ethylene glycol increases at low temperatures, so that the effect of improving the low-temperature characteristics of the capacitor is small.

The present invention aims 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. purpose.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a driving electrolyte prepared by dissolving a quaternary ammonium salt of 0-phthalic acid in an organic solvent. The present invention provides an electrolytic capacitor characterized by:

The quaternary ammonium salt of 0-phthalic acid used in the present invention is one in which the alkyl group (R) of the quaternary ammonium represented by the general formula R4N+ has 1 to 10 carbon atoms, particularly 1 to 4 carbon atoms. For example, tetramethylammonium 0-phthalate, tetraethylammonium 0-phthalate, tetrapropylammonium 0-phthalate, and tetrabutylammonium 0-phthalate can be used.

In the present invention, the reason why a quaternary ammonium salt of 0-phthalic acid is used is that when 0-phthalic acid is other amine salt, the electrolytic solution has a low conductivity and the tan δ of the product becomes large. , because it is not desirable.

The content (concentration) of the quaternary ammonium salt of 0-phthalic 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, 1 -50% by weight is suitable, and in order to obtain good high temperature stability, 5-40% by weight is especially 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-oxazolidin-2-one (hereinafter referred to as A,
06).

Here, the alkyl group includes methyl, ethyl, propyl, etc. Among them, improvement of low temperature characteristics - 1
-, methyl and ethyl are preferred. Further, as the solvent to be mixed, any polar organic solvent commonly used in electrolytic capacitors can be used, and amides, lactones, glycols, sulfur compounds, or carbon salts are preferably used. Specific examples of preferred miscible solvents include N,N-dimethylformamide, N-methylformamide, β-butyrolactone, γ-valerolactone, N-methylpyrrolidone, ethylene glycol, and ethylene glycol monoalkylamide. del, ethylene glycol dialkyl needle, dimethyl sulfogyceto,
Examples include propylene carbonate and ethylene cyanohydrin.

These solvents may be used alone or in a suitable mixture of a plurality of solvents.

In the present invention, in order to obtain a driving electrolyte containing a quaternary ammonium salt of 0-phthalic 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 tetraammonium salt.

In the present invention, it is not necessary to include water in the electrolytic solution, but it is effective to reduce the specific resistance. However, if the water content is increased beyond a certain limit, it will cause the generation of internal gas, which will increase the case swelling and corrosion of the electrode foil of the electrolytic capacitor, so it is not intended for long-term use at high temperatures. For this reason, 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 is preferably 1 to 20% by weight, and 0.5 to 15% by weight.
The range of 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 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.

After mixing a 10% aqueous solution of tetraalkylammonium hydroxide (alkyl group has 1 to 3 carbon atoms) and O-phthalic acid to an equimolar number and dissolving the O-phthalic acid, water is removed using an evaporator. This was removed to produce a quaternary ammonium salt of O-phthalic acid, which was used as a solute and predetermined intervals were dissolved in a polar organic solvent to obtain the electrolytes of Examples 1 to 10. The pH of the electrolyte was adjusted to 5-7.

Using these electrolytes, we manufactured an electrolytic capacitor (rated 10V, 1000μF) with aluminum electrodes,
A high temperature load test (rated voltage applied, 125° C., 1000 hours) was conducted to measure changes in the loss angle tangent (tan δ), and the results are shown in Table 1. In addition, Comparative Examples 1 to 4 were cases in which a solute other than the quaternary ammonium salt of O-phthalic acid was used, and 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, 0. and E, 0. is A, 0. represents methyl and ethyl alkyl groups, respectively.

Table 1 Example of electrolyte composition and changes in anδ during high temperature load test Electrolyte composition (IOV, 125°C) (wt%)
Initial 10-year waiting period, then O-triethylamine phthalate 26 0.11 0.131 γ-butyrolactone 74tb A, 8. A, ka, ~a7ヮ2 Ammonium 26 0.15
0.28 comparison γ-butyrolactone 74
Tetraethylamine maleate 20 3 γ-butyrolactone 65 0.08
0.33 examples ethylene glycol 15
Ammonium borosilicate 4 thyrate 13 0.07
1.09 Ethylene glycol 27 N,N-dimethylformamide 600-Tetramethyl phthalate 1 Ammonium 26 0.08
0.09γ-butyrolactone 60 M, 0. 14 Fruit. -7,27ke1. □, 9 Ammonium 26 2 γ-butyrolactone 55 0.07
0.08/@E, 0.
14 Water 5 Example of 0-tetramethyl phthalate Ammonium 263 γ-
Butyrolactone 43 (1070,10M
,0. 13 Water 180-Phthalatetetramethylammonium 31 4 γ-Butyrolactone 47 0.05
0. 11M, 0. 12 Next, Table 2 shows the low temperature characteristics of electrolytic capacitors.

The electrolytic capacitors had the same dimensions as those described above, and the number of samples was 10 each. The measurement frequency is 120Hz. △C/C20℃ in the table is the capacity change rate at 20℃, Z/
7.20°C indicates the impedance ratio to 20°C.

As can be seen from Table 1, 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 △C/C20℃ and Z/Z 20℃ is large in the 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. Offer 1
-I can do something.

Claims (3)

[Claims] (1) O-
An electrolytic capacitor characterized by using a driving electrolyte formed by dissolving a quaternary ammonium salt of phthalic acid. (2) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of o-phthalic 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.