JPH0775214B2 - Aluminum electrolytic capacitor electrolyte - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic solution for driving an aluminum electrolytic capacitor, and in particular, it improves the high temperature load characteristics of the aluminum electrolytic capacitor and exhibits stable life characteristics for a long period of time. Regarding electrolyte solution.

(Prior Art) Aluminum electrolytic capacitors are required to have reliability for a long period of time. For this reason, inventions have been proposed that improve the high temperature load characteristics of electrolytic capacitors. However, these only guarantee the improvement of the initial value and the reliability after 1000 hours have passed, and few pursue the long-term reliability over 2000 hours.

(Problems to be solved by the invention) Conventionally, the life characteristics of electrolytic capacitors have been improved with respect to deterioration of electrolyte solution, suppression of gas generation and prevention of foil corrosion. Relying only, to improve the life characteristics of 2000 hours or more, ta
An important factor is electrolytic paper, which has a considerable effect on nδ and LC.

It is necessary that the electrolytic paper used for the electrolytic capacitor has excellent impregnation property, good liquid permeability, excellent heat resistance, and does not contain a substance that corrodes aluminum. In addition, if there is a portion where the electrolytic solution is not sufficiently impregnated in the center of the rolled width of the rolled electrolytic paper, the drying progresses and the fibers of the electrolytic paper peel off and adhere to the aluminum foil. Is also thought to be one of the causes of shortening the life of electrolytic capacitors.

As a measure against so-called dry-up of this electrolytic paper, there is JP-A-59-117209, which describes the use of gelling agents such as ethyl cellulose and hydroxyethyl cellulose. However, there are still problems with solubility and temperature characteristics,
The range of use is limited.

(Means for Solving the Problems) The present invention provides ethylene glycol, NN formamide, γ-
Organic polar solvents such as butyrolactone or those obtained by adding water to these solvents were used as a solvent, and at least one solute of boric acid, adipic acid, suberic acid, azelaic acid, butyloctanedioic acid, oxyacid or salts thereof was used. Provided is an electrolytic solution of an electrolytic capacitor in which polyvinylpyrrolidone is added to the electrolytic solution.

Note that phosphoric acid or the like is used as the oxyacid.

(Function) Polyvinylpyrrolidone used in the present invention is N-vinyl-2.
It is a polymer of pyrrolidone, and although it has a high molecular weight, it is well soluble in organic polar solvents and water. In addition, it has a hydrogen bond with a polyhydric alcohol such as ethylene glycol in the electrolytic solution, which has the effect of increasing the withstand voltage of the electrolytic capacitor. Furthermore, with respect to heat, the solution is stable up to 150 ° C, and there is little concern about loss of efficacy due to heat change. Polyvinylpyrrolidone not only regulates the water content of the paper appropriately and prevents the dry-up, but also enhances the permeability of the electrolytic solution between the paper fibers and corrects the distortion of the paper fibers. This prevents peeling of the paper fibers and delays the deterioration of the paper.

Furthermore, since polyvinylpyrrolidone surrounds the dielectric oxide film formed on the surface of the anode electrode in a gel state, polyvinylpyrrolidone has a function of alleviating deterioration caused by water and maintaining a uniform concentration distribution of the electrolytic solution, and thus, leakage current Control the increase over time.

The function of keeping the concentration distribution of the electrolytic solution uniform is an effect that the gelling agent has uniformly, but polyvinylpyrrolidone has a low viscosity and a solute-dispersing ability. For this reason, it is also effective for an electrolytic solution containing boric acid as a solute, which easily precipitates at a low temperature, and a boric acid system has an effect of promoting flame retardancy.

(Example) The composition ratio is shown by comparing the example of the present invention with the conventional example. Table 1
Is 2% by weight of polyvinylpyrrolidone in an electrolytic solution of ethylene glycol, ammonium borate and phosphoric acid (Example A)
Or 8% by weight (Example B) is added, and Table 2
Shows the case where 2% by weight (Example C) or 8% by weight (Example D) of polyvinylpyrrolidone was added to the electrolytic solution containing ethylene glycol, azelaic acid, and ammonia water, and Table 3 shows ethylene glycol, NN dimethylformamide. 2% by weight (Example E) or 8% by weight (Example F) was added to an electrolytic solution containing butyl octanedioic acid, ammonium suberate, and aqueous ammonia. The case where polyvinylpyrrolidone (Example G and Example H) was added to an electrolytic solution containing cellosolve, ammonium adipate, or ammonium citrate is shown.

Results obtained by manufacturing aluminum electrolytic capacitors rated at 400 V and 1200 μF using the electrolytic solutions having the compositions of Conventional Examples 1 to 5 and Examples A to H of the present invention, and conducting reliability tests of capacitance, tan δ, and leakage current. Is shown in FIGS.

(Effects of the Invention) An electrolytic capacitor using the electrolytic solution of the present invention suppresses an increase in leakage current in a high temperature load test, and also prevents deterioration of electrolytic paper, dry-up of elements, and the like, and has long-term reliability. Can be increased. Further conventional gelling agents,
As compared with a polymer agent such as polyvinyl alcohol, the solubility in organic polar solvents and water is good, and the viscosity can be kept low, so that impregnation can be performed quickly. Since polyvinylpyrrolidone has low toxicity, it has great practical value in the work environment.

[Brief description of drawings]

1 to 4 are electrostatic capacitances of the conventional example and the embodiment of the present invention,
FIG. 6 is a characteristic diagram showing the reliability test results for each characteristic of tan δ and leakage current.

Claims (1)

[Claims] 1. An organic polar solvent or a solvent obtained by adding water to this solvent is used as a solvent, and at least one solute of boric acid, adipic acid, suberic acid, azelaic acid, butyloctanedioic acid, oxyacid or salts thereof is used. The electrolytic solution for an aluminum electrolytic capacitor, wherein polyvinylpyrrolidone is added to the electrolytic solution.