JPH08181041A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE: To reduce the loss of an electrolytic capacitor, to improve the reduction in the capacity, and to make progress at high and low temperature characteristics by providing a high spark voltage, a low specific resistance and excellent high and low temperature characteristics. CONSTITUTION: Electrolyte for an electrolytic capacitor contains ethylene glycol as a main ingredient of solvent, and comprises at least one type of 2,2,4- trimethyladipic acid or its salt, at least one type of 2,4,4-trimethyladipic acid or its salt to be dissolved.

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 electrolytic capacitors.

[0002]

2. Description of the Related Art An electrolytic capacitor such as an aluminum electrolytic capacitor has a structure in which a capacitor element is impregnated with an electrolytic solution. And for medium and high voltage electrolytic capacitors, a solvent consisting of ethylene glycol, ammonium borate,
An electrolytic solution in which azelaic acid or a salt thereof, sebacic acid or a salt thereof, butyloctanedioic acid or a salt thereof, or the like is used is used.

[0003]

However, the electrolytic solution in which ammonium borate is dissolved has a drawback that although the spark voltage is high, the specific resistance is large and the loss of the electrolytic capacitor is large. Further, there is a drawback that it is easily deteriorated at high temperature due to the influence of water generated by the esterification reaction.

The electrolytic solution in which azelaic acid, sebacic acid, etc. are dissolved has a small specific resistance, and therefore the loss of the electrolytic capacitor can be reduced. However, since azelaic acid, etc. is a straight chain carboxylic acid, the solubility is low at low temperatures. It has the disadvantage of poor low temperature properties.

Further, since the electrolyte solution in which butyloctanedioic acid or the like is dissolved has a high solubility of butyloctanedioic acid,
Although the low-temperature characteristics are good, this butyloctanedioic acid has a drawback that it easily reacts with aluminum to form a complex and the capacity of the electrolytic capacitor is easily reduced.

The object of the present invention is to improve the above-mentioned drawbacks, to have a high spark voltage, a low specific resistance, excellent high temperature characteristics and low temperature characteristics, so that the loss of the electrolytic capacitor can be reduced and the reduction of the capacity can be improved. The present invention provides an electrolytic solution for an electrolytic capacitor, which can improve its high temperature characteristics and low temperature characteristics.

[0007]

In order to achieve the above-mentioned object, the present invention provides an electrolytic solution for an electrolytic capacitor containing ethylene glycol as a main component, which is 2,2,4-trimethyladipic acid or a salt thereof. The present invention provides an electrolytic solution for an electrolytic capacitor, which is characterized by dissolving at least one of them and at least one of 2,4,4-trimethyladipic acid or a salt thereof.

[0008]

The 2,2,4-trimethyladipic acid and its salt and the 2,4,4-trimethyladipic acid and its salt used in the present invention have the structural formulas shown in [Chemical Formula 1] to [Chemical Formula 4], respectively. It has become.

[Chemical formula 1]

[Chemical formula 2]

[Chemical formula 3]

[Chemical formula 4]

As is clear from the above constitutive formula, these substances have one or two methyl groups at the α-position of the methylene group (-CH _2- ), which causes steric hindrance and causes ethylene glycol. It becomes difficult to cause an esterification reaction with glycols such as. Therefore, the electrolytic solution in which these substances are dissolved can reduce the water generated by the esterification reaction,
High temperature characteristics can be improved.

Further, these substances are dicarboxylic acids or salts having a side chain, have excellent solubility as compared with conventional linear dicarboxylic acids such as azelaic acid, can improve low temperature characteristics, and have a spark voltage. Can be increased and the specific resistance can be reduced.

Furthermore, these substances are unlikely to cause a reaction to form a complex due to the unique molecular structure, and moreover, even if a complex is formed, they are easily dissolved in ethylene glycol, thus preventing the capacity of the electrolytic capacitor from decreasing. it can.

In the present invention, when each of the substances is used alone by mixing 2,2,4-trimethyladipic acid or a salt thereof with 2,4,4-trimethyladipic acid or a salt thereof. The solubility is further increased as compared with. Therefore, the specific resistance can be reduced and the loss of the electrolytic capacitor element can be reduced.

[0017]

EXAMPLES The present invention will be described below based on examples.
The solvent has a composition containing ethylene glycol as a main component and a small amount of water or the like. Then, in this solvent, 2,2,4-trimethyl adipic acid, 2,2,4-trimethyl adipic acid ammonium, 2,4,4-trimethyl adipic acid,
Dissolve ammonium 2,4,4-trimethyl adipate. Furthermore, aqueous ammonia and amines are added if necessary. In addition, at the time of production, ammonia gas may be fed into the liquid to neutralize the liquid.

Next, regarding the embodiment of the present invention and the conventional example,
When the spark voltage and the specific resistance were measured, the results are shown in Table 1. The composition of the electrolytic solution used in this example and the conventional example is 8% by weight of solute dissolved in a solvent consisting of 91% by weight of ethylene glycol and 1% by weight of water.

[Table 1]

As is clear from Table 1, in Examples 1 to 3, the spark voltage was 445 V and the specific resistance was 316 to 322.
Ωcm. On the other hand, in Conventional Example 1 to Conventional Example 6, the spark voltage is 420 to 440 V and the specific resistance is 330 to 846.
Ωcm. Therefore, the spark voltage of Examples 1 to 3 is about 1.01 to 1.06 as compared with Conventional Examples 1 to 6.
1.06 times, and the specific resistance is about 0.37-0.
It is 98 times lower.

Further, the solvent consisting only of ethylene glycol was set to 92 wt% and the solute as shown in Table 1 was added thereto.
Table 2 shows the solubilities when wt% was dissolved.

[Table 2]

As is apparent from Table 2, the solubilities of Examples 4 to 6 are 61 to 64% and Conventional Examples 6 to 12 are the same.
Has a solubility of 11 to 58%. That is, Example 4 to
Example 6 is about 1.05 as compared with Conventional Examples 6 to 12.
~ 5.82 times more soluble.

Furthermore, a rated voltage of 400 V and 330 impregnated with the electrolytic solutions of Examples and Conventional Examples having the compositions shown in Table 3 was used.
Table 4 shows the initial characteristics of the μF aluminum electrolytic capacitor, the high-temperature load test, and the subsequent characteristics of capacitance change rate, tan δ, and leakage current. The test conditions are: ambient temperature 105 ° C, applied voltage 400V
(Rated voltage) and application time up to 2000 hr. The number of samples is 10, respectively. In addition, the measurement results are average values.

[Table 3]

[Table 4]

As is clear from Table 4, the electrolytic capacitors NO1 to NO5 impregnated with the electrolytic solutions of Examples A to E had an initial tan δ of 3.4 to 4.0% and a leakage current of 12 to 14 μA. Is. On the other hand, the electrolytic capacitors NO6 to NO11 impregnated with the electrolytic solutions of Conventional Example A to Conventional Example F have tan δ of 3.6 to 9.6 and leakage current of 12 to 136 μA. Therefore, NO1 to NO5
The electrolytic capacitor of No. 6 is lower in overall tan δ and leakage current than those of NO 6 to NO 11.

After 2000 hours of the high temperature load test, tan δ of the electrolytic capacitors of NO1 to NO5 is 4.2.
˜4.8%, and the tan δ of the electrolytic capacitors of NO7 to NO11 is 4.3 to 12.4%. That is, NO
The tan δ of the electrolytic capacitors 1 to NO5 is lower than that of NO7 to NO11 as a whole.

After 2000 hours, NO1 ~
The capacity change rate of the NO5 electrolytic capacitor is 0.2 to 0.3.
%, NO7-NO11 electrolytic capacitors are -15.2-
It becomes 0.3%. Therefore, it is clear that the electrolytic capacitors of NO1 to NO5 have a lower capacity change rate and can prevent the decrease of the electrostatic capacity.

The NO6 electrolytic capacitors were defective because the explosion-proof valves of all the samples were activated within a standing time of 500 hours.

Further, an aluminum electrolytic capacitor having a rating of 400 V and 330 μF, which is impregnated with the electrolytic solution having the composition shown in Table 3, is subjected to a high temperature no-load test after the initial characteristics are measured, and thereafter the capacitance change rate is measured. , Tan δ and leakage current were measured. The test conditions are an ambient temperature of 105 ° C. and a standing time of up to 2000 hours. The number of samples is 10, respectively. The measurement results are shown in Table 5 as average values.

[Table 5]

As is clear from Table 5, the high temperature no-load test 2
After 000 hr, tan δ of NO12 to NO16 electrolytic capacitors impregnated with the electrolytic solutions of Examples A to E.
Of 4.2 to 4.8%, and t of the electrolytic capacitors NO18 to NO22 impregnated with the electrolytic solutions of Conventional Example B to Conventional Example F.
anδ is 4.3 to 9.8%. Therefore, NO12 ~ N
The electrolytic capacitor of O16 has an overall lower tan δ value than that of NO18 to NO22.

Moreover, after 2000 hours, NO1
2 to NO16, the capacitance change rate of the electrolytic capacitor is 0.2 to
0.3%, NO18 ~ NO22 electrolytic capacitor -1
It becomes 0.3 to 0.3%. That is, NO12 to NO1
The electrolytic capacitor of No. 6 has a lower rate of change in capacitance and can prevent a decrease in electrostatic capacitance.

The NO17 electrolytic capacitors were defective because the explosion-proof valves of all the samples were activated within a standing time of 1000 hr.

Further, with respect to an aluminum electrolytic capacitor having a rating of 400 V and 330 μF impregnated with the electrolytic solution having the composition shown in Table 3, the rate of change in capacitance and the respective characteristics of tan δ were measured in the temperature range of −40 ° C. to 105 ° C. 3 samples each
To be individual. The measurement results are shown in Table 6 as average values.

[Table 6]

As is clear from Table 6, NO23 impregnated with the electrolyte solutions of Examples A to E at -40 ° C.
The electrolytic capacitor of NO27 has a capacity change rate of −29.0.
.About.-27.2% and tan.delta. 206-242%. On the other hand, the electrolytic capacitors NO29 to NO33 impregnated with the electrolytic solutions of Conventional Example B to Conventional Example F have a capacity change rate of −52.5 to −33.2% and a tan δ of 262 to 262.
It becomes 492%. Therefore, the electrolytic capacitors of NO23 to NO27 are more
The rate of change in capacity is reduced to about 51.8 to 87.3% and the tan δ is reduced to about 41.9 to 92.4%.

At a temperature of 105 ° C., NO23
~ NO27 electrolytic capacitor has a capacity change rate of 5.6 ~
5.8% and tan δ is 2.6%. On the other hand, the electrolytic capacitors of NO28 to NO33 have a capacity change rate of 5.6 to 9.8% and a tan δ of 2.6 to 3.0%.
Becomes That is, the electrolytic capacitors of NO23 to NO27 are lower in overall capacity change rate and tan δ than those of NO28 to NO33.

[0040]

As described above, according to the present invention,
Since 4-trimethyladipic acid or its salt and 2,4,4-trimethyladipic acid or its salt are mixed and dissolved, the spark voltage is high, the specific resistance is low, and the low temperature characteristics and high temperature characteristics are excellent. Moreover, it is possible to obtain an electrolytic solution for an electrolytic capacitor, which can reduce the loss of the electrolytic capacitor, prevent the capacity from decreasing, and improve its high-temperature characteristics and low-temperature characteristics.

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[Chemical 4]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor containing ethylene glycol as a main component, wherein at least one of 2,2,4-trimethyladipic acid or a salt thereof and 2,4,4-trimethyladipic acid or An electrolytic solution for an electrolytic capacitor, which is characterized by dissolving at least one of the salts.