JPS6124813B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrolytic solution for driving an electrolytic capacitor. Conventionally, as an electrolytic solution for driving an electrolytic capacitor, an electrolytic solution in which boric acid or ammonium borate is dissolved in ethylene glycol is known. This electrolytic solution has a drawback in that the specific resistance becomes large at low temperatures due to the high viscosity of ethylene glycol, and therefore the temperature characteristics change significantly at low temperatures. Furthermore, in order to improve conductivity at low temperatures, an electrolytic solution in which organic acid salts are dissolved in ethylene glycol and water is added is also known, but the presence of water causes deterioration of the aluminum anodic oxide film. It is large, and the operating temperature range is up to approximately 85°C, so high-temperature characteristics cannot be expected. Next, instead of ethylene glycol, N.
Electrolytes in which ammonium borate is dissolved in N'-dimethylformamide, and electrolytes in which water is further added to this electrolyte, are also known, but in electrolytes to which water is not added, boric acid is dissolved in N'-dimethylformamide. Only a small amount of ammonium dissolves, resulting in a high resistivity, and an electrolyte containing water can only be used at a temperature range of about 85°C, making it difficult to expect high-temperature properties. Furthermore, as an electrolytic solution that can be used over a wide temperature range from low to high temperatures, boric acid is Esterified with 5 to 15 wt% of alcohols and 10 to 35 wt% of alcohols and water removed, and amines of 2 to 35 wt%.
15wt% and N・N'-dimethylformamide 45~
An electrolyte solution containing 75wt% is known. This electrolytic solution has a high specific resistance, and since amines are used, it lacks high-temperature stability and cannot be expected to have long life characteristics. Therefore, as an electrolytic solution with low resistivity, good low temperature characteristics and long life characteristics,
As disclosed in No. 68866, "Electrolyte for Dry Aluminum Electrolytic Capacitors," an ester obtained by reacting an alcohol with ammonium borate and an N/N'-dimethylformamide solution in which an organic acid salt is dissolved are mixed by weight. Ester in ratio 10~30wt
%, N・N'-dimethylformamide solution 90~
An electrolytic solution mixed at 70 wt% is known. According to this electrolyte, N.N'-dimethylformamide is a single solvent, and since the boiling point of N.N'-dimethylformamide is 153° C., the high temperature stability is unstable at temperatures near the boiling point. Therefore, the present invention aims to provide an electrolytic solution for driving an electrolytic capacitor that has further improved high-temperature characteristics, is stable over a wide temperature range from low temperatures to about 200°C, and can be expected to have a long life. It is something. Specifically, the organic acid salt was converted into γ-valerolactone (3-methylbutyrolactone, abbreviated as
GVL) and N・N'-dimethylformamide (abbreviation: DMF) dissolved in a mixed solution,
The present invention provides an electrolytic solution that is a mixture of ammonium borate and a boric acid ester obtained by esterifying alcohols. Next, examples of the electrolytic solution for driving an electrolytic capacitor according to the present invention will be described. A boric acid ester is produced by dissolving 20 to 40 wt% of ammonium borate and 80 to 60 wt% of alcohol (ethylene glycol, propylene glycol, etc.), heating, and esterifying it. γ-valerolactone 75-25wt% and N・N′-
Organic acid salts (ammonium salicylate, monoammonium phthalate, diammonium phthalate, ammonium benzoate, etc.) 0.2 to 1.0 mol/in a mixed solvent with 25 to 75 wt% dimethylformamide
Make a mixed solution that dissolves the following. Next, 10 to 30wt of the boric acid ester obtained in
%, and mix the mixed solution obtained in 90 to 70 wt%. In the electrolytic solution according to the present invention, as shown in Fig. 1, when the organic acid salt mixed solution is 70 wt% or less (boric acid ester is 30 wt% or more), the conductivity is 1000μ
S/cm or less, and when the organic acid salt mixed solution becomes 90 wt% or more (boric acid ester is 10 wt% or less), the withstand voltage becomes 50 V or less, making it impractical. In the mixed solvent of the organic acid salt mixed solution, as shown in Figure 2, γ-valerolactone [GVL] is 75 wt% or more (N・N'-dimethylformamide [DMF] is 25 wt%).
% or less), the conductivity is less than 1000μS/cm, and γ-valerolactone is less than 25wt% (N.
When the N'-dimethylformamide content is 75wt% or more, the withstand voltage becomes 50V or less. As shown in Figure 3, when the concentration of organic acid salt in the organic acid salt mixture solution becomes 0.2 mol/or less, the conductivity decreases to 1000 μS/cm.
At 1.0 mol/ or more, the conductivity approaches saturation and there is no improvement in conductivity. Therefore, the range of 0.3 to 0.9 mol/ is preferable. In this case, the mixed solvent contains both γ-valerolactone and N·N'-dimethylformamide at 50 wt%. As shown in Figure 4, borate esters contain alcohols of 80wt% or more (ammonium borate 20wt%).
below), the leakage current increases rapidly, and when the alcohol content is below 60wt% (ammonium borate
(40wt% or more), the viscosity increases. Table 1 specifically illustrates the composition of the electrolytic solution according to the embodiment of the present invention, and shows a comparison with a conventional composition. In Table 1, EG/boric acid ester indicates boric acid ester obtained by using ethylene glycol,
PG/boric acid ester refers to boric acid ester obtained by using propylene glycol. Furthermore, among those shown in Table 1, the electrolytes of Conventional Examples 1, 2, 3 and Examples 1, 3, 5, and 8 (of the present invention) were used to impregnate a capacitor element with a rating of 10 V and 1000 μF. Table 2 shows the characteristics of aluminum electrolytic capacitors at low temperature, room temperature, and high temperature. This electrolytic capacitor has a well-known structure, in which a capacitor element consisting of an anode and a cathode of aluminum foil sandwiched between electrolytic paper and wound around the capacitor element is impregnated with electrolyte, and the capacitor element is inserted into an aluminum case using a sealant. It has a structure in which it is housed in a

【table】

【table】

[Table] Next, Fig. 5 shows that the electrolytes of Conventional Examples 2 and 3 and Examples 1, 3, 5, and 8 (of the present invention) were used to impregnate a capacitor element with a rating of 10 V and 1000 μF. This shows the accelerated life characteristics of aluminum electrolytic capacitors at high temperatures. In Figure 5, a is the capacitance change rate (ΔC), b is the tangent of the loss angle (tanδ),
c indicates the characteristics of leakage current (LC). As a result, it can be seen from Table 1 that the electrolytic solution according to the present invention has a higher conductivity (1/Ωcm) than the conventional example. Furthermore, Table 2 shows that both the rate of change in capacity (%) and the tangent of loss angle (tan δ) are stable over a wide temperature range. Furthermore, from the accelerated life characteristics at high temperatures shown in Figure 5, the electrolytic solution according to the present invention is more stable and superior over a long period of time, especially in terms of capacitance change rate (%) and tangent of loss angle (tan δ). I can see that From the above, the present invention can provide an electrolytic solution that has a low specific resistance and has a long life when used over a wide temperature range from low to high temperatures.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the amount of organic acid salt mixed solution and boric acid ester in the electrolytic solution according to the present invention and the electrical conductivity and counter pressure of the electrolytic solution. Figure 3 is a characteristic diagram showing the relationship between the amount of GVL) and N/N'-dimethylformamide (DMF), conductivity, and counter pressure, and Figure 3 is a characteristic diagram showing the relationship between organic acid salt concentration and conductivity. Fourth
The figure is a characteristic diagram showing the relationship between viscosity and leakage current of a boric acid ester consisting of ammonium borate and alcohols, and Figure 5 shows a capacitor with a rating of 10 V and 1000 μF using the conventional electrolyte and the electrolyte according to the present invention. The figure shows the accelerated life characteristics at high temperatures of an aluminum electrolytic capacitor impregnated into an element, where a shows the capacitance change rate (ΔC), b shows the tangent of the loss angle (tanδ), and c shows the leakage current (LC). The characteristics of each are shown.

Claims (1)

[Claims] 1 Organic acid salts are γ-valerolactone and N.N'-
A solution dissolved in a mixed solution of dimethylformamide and a boric acid ester obtained by esterifying ammonium borate and alcohol are combined in a weight ratio of 70 to 90 wt% of the organic acid salt mixed solution and the boric acid ester.
An electrolytic solution for driving an electrolytic capacitor characterized by being mixed at a concentration of 10 to 30 wt%. 2 In Claim 1, the content of the organic acid salt mixed solution is that the γ-valerolactone is
25wt%, 25% of the N・N'-dimethylformamide
An electrolytic solution for driving electrolytic capacitors characterized by ~75wt%. 3. In claim 1 or 2, the organic acid salt mixture solution includes 0.3 to 0.9 mol/dissolved of the organic acid salt in a mixed solvent consisting of the γ-valerolactone and the N·N'-dimethylformamide. An electrolytic solution for driving electrolytic capacitors. 4. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the boric acid ester is an esterification of 80 to 60 wt% of the alcohol and 20 to 40 wt% of the ammonium borate. 5. The electrolytic solution for driving an electrolytic capacitor according to claim 1, 2 or 3, characterized in that ammonium salicylate, monoammonium phthalate, diammonium phthalate, or ammonium benzoate is used as the organic acid salt. 6. The electrolytic solution for driving an electrolytic capacitor according to claim 1 or 4, characterized in that ethylene glycol or propylene glycol is used as the alcohol.