JPH0399416A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent the deterioration of characteristics and the like generated by the washing using a halogenohydrocarbon cleaning liquid by a method wherein a specific compositional solution, which is mainly composed of gamma- butyrolactone, is used. CONSTITUTION:The solvent of an electrolyte consists of component mainly composed of gamma-butyrolactone containing 15wt.% or less ethylene glycol and 0.1 to 8wt.% water. Butyloctanedioic acid is dissolved and used as a solute. Also, monoalkylamine and dialkylamine are added to adjust pH to 4 to 7.5wt.%. The gamma-butyrolactone, which is the main component of the above-mentioned solvent, prevents a washing liquid from coming into contact with water by surrounding halogenohydrocarbon molecules, and also it suppresses the generation of hydrolysis. Also, the above-mentioned monoalkylamine and dialkylamine trap the chlorine ions generated by the hydrolysis of the cleaning liquid, and they display a strong corrosion-suppressing action.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrolytic solution for electrolytic capacitors.

(Prior technology) Conventional electrolytic capacitors such as aluminum electrolytic capacitors are made by winding an anode foil connected to a lead wire, a separator, and a cathode foil in layers to form a capacitor element, which is then impregnated with an electrolytic solution and then wrapped in a case. It has a structure in which it is stored and sealed by attaching a lid to this case.

The anode foil and the 1114 foil are etched aluminum foils, and the former is particularly chemically converted to form a dielectric oxide film.

By the way, when electronic components such as electrolytic capacitors are connected to a printed circuit board, in order to remove flux and dirt contained in the half-coat used for connection, 1.1.1-trichloroethane or 1.1. The cleaning process is performed using a halogen-based cleaning agent such as 2-Trifluoroethane (Freon 113).

(Problem to be Solved by the Invention) However, in the conventional 41I electrolytic capacitor, cleaning liquid may enter through the gap between the case and the lid.

When the cleaning solution enters the case, it reacts with the water contained in the electrolyte to liberate chlorine ions, which cause corrosion of the anode foil and cathode foil. As a result, defects such as the electrical characteristics of the electrolytic capacitor are significantly reduced or the capacitor function is lost occur.

In order to prevent this drawback, some electrolytic capacitors have a structure in which epoxy resin is coated on the outer surface of the lid, but this requires coating the resin and curing it, making the J-manufacturing process complicated and time-consuming. There are drawbacks.

Further, a corrosion inhibitor such as a nitro compound such as P-nitrphenol or P-nitrobenzoic acid, or a silver compound may be added to the electrolytic solution. However, P-nitrophenol has an extremely strong yellow staining property, and it adheres to and stains the case and the hands of workers, causing problems in workability. Although P-nido-O benzoic acid does not have any dyeing problems, it has the disadvantage that even when added in a small amount, the spark voltage decreases and the withstand voltage is low. In addition, conventional corrosion inhibitors include Freon 11, which has less dissociation of chlorine.
3 shows a relatively good corrosion inhibiting effect, but 1,
1.1-Trichloroethane has the drawback of being less effective.

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor that can improve the above-mentioned drawbacks and prevent property deterioration caused by cleaning with a halogenated hydrocarbon-based cleaning solution.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention has provided a solution containing γ-butyrolactone as a main component, ethylene glycol of 15 wt% or less, and water of 0.1 to 8 wt%. While dissolving octanoic acid as a solute, monoalkylamine or dialkylamine is dissolved to adjust the pH to 4-7.
The present invention provides an electrolytic solution for electrolytic capacitors according to No. 5.

(Function) T-butyrolactone, which is the main component in the solvent, surrounds the halogen-based cleaning liquid molecules, prevents the cleaning liquid from coming into contact with water, and has the effect of suppressing hydrolysis.

Furthermore, monoalkylamines and dialkylamines trap chlorine ions generated by hydrolysis of the cleaning solution, and exhibit a strong corrosion inhibiting effect.

(Example) Hereinafter, the present invention will be explained based on examples.

The solvent of the electrolytic solution is mainly composed of γ-butyrolactone, 15 wt% or less of ethylene glycol, and 0.1 to 8 w of water.
Consists of t% components.

As a solute, 2M of butyl octane is dissolved.

Further, in order to adjust the pH to 4 to 7.5, a MoI alkylamine or a dialkylamine is added.

Monomethylamine, monoethylamine, or monopropylamine is used as the monoalkylamine. Dimethylamine, diethylamine, or dipropylamine is used as the dialkylamine.

Next, an aluminum electrolytic capacitor having a rating of 400V-220 μF is manufactured by impregnating the electrolytic solution of the example of the present invention, the comparative example, and the conventional example. Then, these capacitors were placed in a cleaning tank, and 1°1.1-trichloroethane at a temperature of 50°C was injected, and after washing for 15 minutes, they were placed in a cleaning tank at a temperature of 110°C, and a voltage of 400 μ was applied. A high-temperature load test was conducted to investigate the occurrence of corrosion. The number of samples was 30 for each example, comparative example, and conventional example, and after 500 hours of testing time, 1
0 pieces were disassembled, and the remaining 20 pieces were completed in 11 hours after the test time of 1000 hours.
11 were dismantled and the occurrence of corrosion was investigated.

The results were as shown in the table.

As is clear from the table, according to Examples 1 to 4 of the present invention, there was no corrosion even after 500 hr and 1000 hr, whereas in Conventional Example 1 and Conventional Example 2, the corrosion was 1000 hr.
Corrosion had occurred in all of the hls. Furthermore, as is clear from Comparative Example 1 and Comparative Example 2, when the content of ethylene glycol exceeds 15 wt%, after 1000 hr, each
0% and 50% corrosion occurs, reducing the effectiveness of corrosion inhibition. Further, as is clear from Comparative Examples 3 and 4, the specific resistance increases when water is not included, and the specific resistance can be lowered by containing water as in the present invention.

In addition, in an electrolytic solution consisting of 75 wt% γ-butyrolactone, 10 wt% ethylene glycol, and water as a solvent, 1011% butyloctanoic acid as a solute, and 5 wt% diethylamine, we investigated the change in specific resistance when the water content was changed. Shown in the figure.

As is clear from the figure, when the water content exceeds 6 wt%, the specific resistance hardly changes. Furthermore, it is generally known that when the amount of water added increases, the amount of gas generated increases and the life of the capacitor becomes shorter. Furthermore, if water is not added, the chemical formation properties will be very poor. Therefore, the appropriate amount of water to be added is 0.1 to 8 wt%.

(Effects of the Invention) As described above, according to the present invention, since γ-butyrolactone is the main component and monoalkylamine and dialkylamine are dissolved, the corrosion inhibiting effect can be improved, and butyloctane dioic acid is dissolved. By doing so, the spark voltage can be increased, and by adding ethylene glycol in an amount of 15 wt% or less and water in a range of 0.1 to Qwt%, an electrolytic solution for an electrolytic capacitor with a low specific resistance can be obtained.

[Brief explanation of drawings]

The figure shows a graph of specific resistance when the water content is changed in an example of the present invention.

Claims (1)

[Claims] (1) In a solvent containing γ-butyrolactone as the main component, 15 wt% or less of ethylene glycol, and 0.1 to 8 wt% of water, dissolve butyloctane dioic acid as a solute and dissolve monoalkylamine or dialkylamine. An electrolytic solution for electrolytic capacitors with a pH of 4 to 7.5.