JPH09102439A - Driving electrolytic solution for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve characteristics and to realize long-term high reliability of an electrolytic capacitor. SOLUTION: The electrolytic solution wherein metaphosphoric acid, sodium metaphosphate or sodium hexametaphosphoric acid is dissolved in the electrolytic solution wherein higher dibasic acid, or its ammonium salt and boric acid, or its ammonium salt is dissolved in the solvent with ethylene glycol as a main component. Metaphosphoric acid or sodium metaphosphate is dissolved by 0.01-0.50weight% against electrolytic solution solvent 100g, or, sodium hexametaphosphoric is dissolved by 0.01-0.10weight% against the electrolytic solution solvent 100g, for the electrolytic solution. All the metaphosphoric acid ((PHO3 )n ), the sodium metaphosphate ((NaPO3 )n ), and the sodium hexametaphosphoric acid ((NaPO3 )n P2 O5 ) are polyacid, here, in the metaphosphoric acid and the sodium metaphosphate, n=1-14, and in the sodium hexametaphosphoric acid, n=10-35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor for medium and high voltage.

[0002]

2. Description of the Related Art Conventionally, an orthophosphoric acid for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution) has an ability to form an oxide film, improves the water resistance of aluminum foil, and suppresses film deterioration. The addition of a phosphoric acid compound such as an acid or an ammonium salt thereof has been studied.

[0003]

Since orthophosphoric acid or its ammonium salt is consumed during the formation of an oxide film, the concentration in the electrolytic solution decreases over time, and a long-term high temperature load test or high temperature no-load test of an electrolytic capacitor is performed. In, the deterioration of the oxide film of the aluminum foil causes a decrease in capacitance and an increase in leakage current. Therefore, if the addition amount of orthophosphoric acid or its ammonium salt is excessively increased, the solubility in the aluminum foil and the oxide film is increased and corrosion is caused, which is not preferable. Further, orthophosphoric acid or its ammonium salt has poor thermal stability and has a drawback that the effect of suppressing the above-mentioned deterioration of the oxide film is reduced in a high temperature range. It is an object of the present invention to improve the above-mentioned drawbacks, to stabilize the characteristics of an electrolytic capacitor for a long time, and to provide an electrolytic solution for driving an electrolytic capacitor which exhibits a film deterioration suppressing effect at high temperatures.

[0004]

SOLUTION: An electrolytic solution for an electrolytic capacitor, in which a higher dibasic acid or its ammonium salt and boric acid or its ammonium salt are dissolved in a solvent containing ethylene glycol as a main component, metaphosphoric acid or sodium metaphosphate, or An electrolytic solution in which sodium hexametaphosphate is dissolved, wherein the metaphosphoric acid or sodium metaphosphate is 0.01 to 0.5 with respect to 100 g of the electrolytic solution solvent.
0% by weight is dissolved, or the sodium hexametaphosphate is added in an amount of 0.01 to 0.
It is an electrolytic solution in which 10% by weight is dissolved, and the metaphosphoric acid ((HPO ₃ ) n) and sodium metaphosphate ((NaP
O ₃ ) n), sodium hexametaphosphate ((NaP
O ₃ ) nP ₂ O ₅ ) are all polyacids, and n = 1 to 14 for metaphosphoric acid and sodium metaphosphate, and n = 10 to 35 for sodium hexametaphosphate. Have found that it is possible to provide an electrolytic capacitor that exhibits stable characteristics over a long period of time.

[0005]

[Function] Metaphosphoric acid changes to orthophosphoric acid by a hydration reaction in an aqueous solution, but in an electrolytic solution for electrolytic capacitors with a low water content, the reaction proceeds slowly and orthophosphoric acid is gradually supplied to the electrolytic solution. Therefore, since the water resistance of the aluminum foil of orthophosphoric acid and the ability to form an oxide film can be maintained without being reduced, it is possible to prevent the capacitance of the electrolytic capacitor from decreasing and the leakage current from increasing. Further, since sodium hexametaphosphate having a large molecular weight has excellent thermal stability due to its structure, it is possible to stabilize the characteristics of the electrolytic capacitor for a long time even in a high temperature region.

[0006]

EXAMPLES The concrete contents of the examples will be described below. A polyhydric alcohol such as ethylene glycol is used as the solvent. The solute contains 7-vinyl-9-hexadecene-1.
-16-Dicarboxylic acid or its ammonium salt is used. Boric acid and mannite are used as additives. Tables 1 and 2 show the compositions of the examples and the measurement results. However,
The specific resistance was measured at 30 ° C and the spark voltage was measured at 85 ° C.
As is clear from Tables 1 and 2, the specific resistance was about 710 Ω · cm in both the conventional example and the example, but the spark voltage was 430 V in the conventional example, while the specific examples were 1 to 9
Then, it becomes 440 to 450V. That is, the specific resistance is almost the same, and the spark voltage of Examples 1 to 9 is 2.0 to 5.0%.
It showed a high value.

[0007]

[Table 1]

[0008]

[Table 2]

Further, a high temperature load test and a high temperature no-load test were carried out using an electrolytic capacitor rated at 400 V and 10 μF using the electrolytic solutions of the conventional examples and Examples 1 to 9 shown in Tables 1 and 2. High temperature load test conditions are temperature 105 ℃, applied voltage 4
The test was performed under the conditions of a high temperature no-load test condition of 105 ° C. and a standing time of 2000 hours, and the number of electrolytic capacitor samples was 10 in each test. The measurement results are shown in Tables 3 and 4.

[0010]

[Table 3]

[0011]

[Table 4]

As is clear from Tables 3 and 4, in the initial stage, there is no remarkable difference between Examples 1 to 6 and the conventional example, but Examples 7 to 9 are ta when compared with the conventional example.
n δ and leakage current are slightly improved. High temperature load test 2
After 000 h, as is clear from Table 3, the difference between the conventional example and the example is more remarkable, and particularly in Examples 7 to 9, the capacitance change rate, tan δ, and the leakage current are different from those of the conventional example. Both are greatly improved.

As shown in Table 4, as in the case of the high temperature load test 2000h, the measured results after the high temperature no load test 2000h also show improvement in each characteristic in the embodiment as compared with the conventional example. From this, it is understood that metaphosphoric acid, sodium metaphosphate, and sodium hexametaphosphate improve the capacitor characteristics, and particularly sodium hexametaphosphate has a remarkable improving effect even in a high temperature region. When the added amount of metaphosphoric acid, sodium metaphosphate and sodium hexametaphosphate is 0.01% or less, no remarkable effect is observed, and the added amount of metaphosphoric acid and sodium metaphosphate is 0.5% or more, and sodium hexametaphosphate is added. If the amount is 0.1% or more, it takes a long time for the dissolution, the solute is precipitated, and the spark voltage is lowered, which is not preferable.

[0014]

As described above, the present invention improves various characteristics of an electrolytic capacitor such as capacitance, tan δ and leakage current as compared with the conventional electrolytic solution, and provides an electrolytic capacitor which is stable at high temperature for a long time. It is possible to provide a realizable electrolytic solution.

Claims (4)

[Claims] 1. A driving electrolytic solution for an electrolytic capacitor in which a higher dibasic acid or its ammonium salt and boric acid or its ammonium salt are dissolved in a solvent containing ethylene glycol as a main component, and metaphosphoric acid or sodium metaphosphate, or hexametaline. An electrolytic solution for driving an electrolytic capacitor, characterized in that sodium acid is dissolved. 2. The above-mentioned metaphosphoric acid or sodium metaphosphate is 0.01 to 0.05 with respect to 100 g of an electrolytic solution solvent.
The electrolytic solution for driving the electrolytic capacitor according to claim 1, wherein the electrolytic solution dissolves by weight. 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein 0.01 to 0.10% by weight of the sodium hexametaphosphate is dissolved in 100 g of the electrolytic solution solvent. 4. The metaphosphoric acid ((HPO ₃ ) n),
Sodium metaphosphate ((NaPO ₃ ) n) and sodium hexametaphosphate ((NaPO ₃ ) nP ₂ O ₅ ) are all polyacids. Metaphosphoric acid and sodium metaphosphate are n = 1 to 14, sodium hexametaphosphate is n. =
An electrolytic solution for an electrolytic capacitor, which is 10 to 35.