JPH07240350A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent an electrolytic capacitor from igniting, to inhibit the increase in an LC with time and to improve the life of an electrolyte for electrolytic capacitor. CONSTITUTION:An electrolyte for electrolytic capacitor, which contains a polyhydric alcohol and the like as its main solvent and contains more than one kind of boric acids or salts out of a boric acid or its salt as its solute, dissolves a polysaccharide and the like and at the same time, contains more than one kind of phosphoric acids or phospholic esters out of a phosphoric acid or a phosphoric ester.

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 In recent years, as communication equipment and measuring equipment have become higher in performance, electrolytic capacitors used as parts of these equipment are required to have better characteristics and longer life. It was In order to improve the characteristics of the electrolytic capacitor, for example, an electrolytic solution having an excellent action of repairing the anodized film of the electrode foil may be used.

Conventionally, Japanese Patent Publication No. 62-
As described in Japanese Patent Publication No. 7684 and Japanese Patent Publication No. 62-11765, ethylene glycol is used as a main solvent, and a long-chain dibasic acid having an alkyl group in its side chain or a salt thereof is used as a solute to reduce the capacitance. Some have a composition in which additives are dissolved in order to prevent reduction.

Further, an electrolytic solution containing boric acid or a salt thereof as a main solute is also used in order to prevent the electrolytic capacitor from being ignited and damaging the device.

[0005]

However, using the former polyhydric alcohols such as ethylene glycol as a main solvent,
An electrolytic solution containing an organic acid such as a long-chain dibasic acid having an alkyl group in its side chain as a main solute is flammable. Therefore, this electrolytic solution has the drawback of increasing the risk of ignition when the capacitor element is destroyed when the electrolytic capacitor impregnated with the electrolytic solution is used in a high temperature atmosphere or when a high voltage is applied. is there.

The latter electrolytic solution contains a large amount of esterification water represented by the reaction between ethylene glycol and boric acid, and this water content promotes hydration deterioration of the anodic oxide film of the electrode foil. There is. Therefore, this electrolyte is
There are drawbacks that the leakage current (hereinafter referred to as LC) of the electrolytic capacitor is increased and the gas generation is increased, the explosion-proof valve provided on the lid is operated in a relatively short time, and the life of the electrolytic capacitor is shortened.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor, which improves the above-mentioned drawbacks, prevents ignition of the electrolytic capacitor, suppresses increase of LC with time, and improves life. is there.

[0008]

In order to achieve the above-mentioned object, the present invention is intended for an electrolytic capacitor which uses a polyhydric alcohol as a main solvent and one or more of boric acid or a salt thereof as a solute. Disclosed is an electrolytic solution for an electrolytic capacitor, which is characterized in that, in the electrolytic solution, a polysaccharide is dissolved and at least one kind of phosphoric acid or phosphoric acid ester is contained.

Polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, 1,4
-Butanediol, trimethylethylene glycol, pentaglycerol, trimethylene glycol isobutylene glycol (2-methyl-1,2-propanediol), glycerin and the like are used.

Then, boric acid, ammonium borate, or boric acid + ammonium borate is dissolved as a main solute in a solvent mainly composed of individual substances of these polyhydric alcohols or substances combining two or more kinds. .

As the polysaccharide, dextrin, dextran, araban, galactan, mannan, pectin, pectic acid, alginic acid or the like is used, and each substance is dissolved alone or in combination of two or more kinds. The amount of this polysaccharide dissolved is preferably in the range of 0.1 to 10.0 wt%. That is, if it is less than 0.1 wt%, the effect of suppressing the gas generation becomes low, and if it is more than 10.0 wt%, the specific resistance increases.

Further, as the phosphoric acid ester, triethyl phosphate, tri-n-butyl phosphate, triphenyl phosphate or the like is used. The phosphoric acid or phosphoric acid ester content is preferably in the range of 0.005 to 2.0 wt%. Outside this range, the effect of suppressing gas generation decreases.

[0013]

The polysaccharide has a large number of OH groups, so that it is adsorbed on the surface of the electrode foil. Since this polysaccharide has a large molecular weight and a high surface shielding property, it is possible to suppress the deterioration of the anodized film on the surface of the electrode foil and the elution of the metal of the electrode foil such as aluminum. Even if the polysaccharide is adsorbed on the surface of the electrode foil, the electrostatic capacitance of the electrolytic capacitor does not decrease due to the adsorption.

Further, phosphoric acid and phosphoric acid ester react with the electrode foil such as aluminum to form a dense and water resistant film on the surface thereof. Therefore, hydration deterioration of the anodized film on the surface of the electrode foil can be suppressed. And the increase of LC of an electrolytic capacitor can be suppressed.

Further, when a polysaccharide and phosphoric acid or phosphoric acid ester are used together, when the voltage is applied to the electrolytic capacitor in a high temperature atmosphere, the anodic oxide film deteriorates and leakage current increases. The effect of suppressing is improved. Therefore, the electrolytic capacitor generates less gas and has a longer life.

[0016]

EXAMPLES Examples of the present invention will be described below. The solvent is
Polyhydric alcohols such as ethylene glycol and glycerin are used. Further, ammonium borate is used as the solute. As the polysaccharide, dextrin, dextran, araban, galactan, mannan, pectic acid, and alginic acid are used alone, or dextrin and galactan or araban and pectic acid are used in combination. Further, phosphoric acid or phosphoric acid ester is used alone. As the phosphoric acid ester, triethyl phosphate, tri-n-butyl phosphate, and triphenyl phosphate are used. In addition, mannitol or sorbitol is used as an additive.

Next, L of the aluminum electrolytic capacitors impregnated with the electrolytic solutions of Examples and Conventional Examples having the compositions shown in Table 1 was used.
The C characteristics and the operating condition of the explosion-proof valve were measured.

[0018]

[Table 1]

The aluminum electrolytic capacitor used for measurement is rated at 400 V and 680 μF. Then, with 400V and DC applied to this aluminum electrolytic capacitor, the temperature of 90
Let stand for up to 2000h in the atmosphere of ℃. LC characteristic is 1
After being left for 000 hours and 2000 hours, the sample was left in an atmosphere at a temperature of 20 ° C. for 24 hours without any load, and then the voltage was set to 400.
V. It was determined by applying DC and measuring the value after 5 minutes.
As for the operation status of the explosion-proof valve, the number of samples in which the explosion-proof valve operated after being left for 2000 hours was measured. The number of samples is 10 each
To be individual. The measurement results are shown in Table 2.

[0020]

[Table 2]

As is clear from Table 2, the LC characteristics are 20
After 00h, Examples 1 to 14 are 55 to 70
μA, and Conventional Example 1 to Conventional Example 4 are 100 to 120 μA. That is, the former is about 46 to 70 compared to the latter.
It has fallen to%. In addition, the operating conditions of the explosion-proof valve are 0 to 10 in Examples 1 to 14, but 8 to 10 in Conventional Examples 1 to 4.

[0022]

As described above, according to the present invention, a polysaccharide is dissolved in an electrolytic solution containing ethylene glycol or the like as a main solvent and boric acid or ammonium borate as a solute to form phosphoric acid or phosphate ester. Since it contains, it is possible to prevent ignition of the electrolytic capacitor and improve LC characteristics,
An electrolytic solution for an electrolytic capacitor that can improve the life is obtained.

Claims (1)

[Claims] 1. An electrolytic solution for an electrolytic capacitor, which comprises a polyhydric alcohol as a main solvent and one or more kinds of boric acid or a salt thereof as a solute, and dissolves a polysaccharide and at the same time phosphoric acid or a phosphoric acid ester. An electrolytic solution for an electrolytic capacitor, containing one or more of the above.