JP2006186217A - Electrolyte for driving aluminium electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for driving an aluminum electrolyte capacitor capable of surely preventing a corrosion in the capacitor without a number of processes. <P>SOLUTION: A benzoic acid, an ormic acid, a 1,6-decanedicarboxylic acid, a carboxylic acid such as sebacic acid or its common salt such as ammonium or a diethylamine, and a polyethylene glycol sorbitan ester ether of 0.5 to 5.0 wt% shown by the formula 1 are blended in a solvent primarily comprising ethylene glycol. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic solution).

An aluminum electrolytic capacitor has a structure in which an anode foil, a cathode foil, and an element obtained by winding electrolytic paper are impregnated with an electrolytic solution in a case, and the opening of the case is sealed with a sealing plate. .
For example, the electrolytic solution is blended with a solvent such as ethylene glycol as a solute of carboxylic acid or ammonium salt thereof, boric acid or ammonium salt thereof, and further blended with polyhydric alcohols such as mannitol as necessary. Sometimes.
Here, polyhydric alcohols form an ester compound with carboxylic acid or boric acid, and the withstand voltage of the electrolytic solution is improved due to structural characteristics thereof (see, for example, Patent Documents 1 to 3).
Japanese Examined Patent Publication No. 7-48459 (page 1-4) Japanese Examined Patent Publication No. 7-48460 (page 1-3) Japanese Examined Patent Publication No. 7-63047 (page 1-4)

However, in aluminum electrolytic capacitors, the solder flux used to mount them on the board, the cleaning agent used to clean the board, or the ionic components contained in the resin part or rubber part of the sealing plate enter the capacitor. There are things to do.
In such a state, when energizing the aluminum electrolytic capacitor for a long time in a high-temperature atmosphere, the lead plate pulled out from the element and the connecting portion by crimping the inner portion of the terminal fixed to the sealing plate, Alternatively, there is a problem that electrochemical corrosion occurs in the aluminum portion in the vicinity thereof, resulting in disconnection.

  As a method for preventing the occurrence of such corrosion, a structure in which the connection portion and its periphery are completely covered with a silicone resin or the like can be considered. However, in such a structure, it takes a lot of time to apply the silicone resin. Therefore, there is a problem that productivity is lowered. Further, there is a problem that corrosion disconnection cannot be reliably prevented if the amount of silicone resin applied is small or the application position is shifted.

  In view of the above problems, an object of the present invention is to provide an electrolytic solution for driving an aluminum electrolytic capacitor that can reliably prevent corrosion in the capacitor without much effort.

As a result of various investigations to solve the above problems, when polyethylene glycol sorbitan ester ether is blended in the electrolyte, the lead plate pulled out from the element and the inner part of the terminal fixed to the sealing plate are caulked. New knowledge that corrosion at or near the connection portion can be prevented is obtained, and the present invention has been made based on such knowledge.
That is, in the electrolytic solution for driving an aluminum electrolytic capacitor of the present invention, at least carboxylic acid or a salt thereof and polyethylene glycol sorbitan ester ether represented by the following chemical formula are blended in a solvent mainly composed of ethylene glycol. Features.

However, in Chemical formula 1, n ₁ , n ₂ , and n ₃ are integers of 4 to 15 and represent the number of oxyethylene groups, and R represents an alkyl group or alkylene group having 12 to 18 carbon atoms. Show. Here, n ₁ , n ₂ , and n ₃ may be the same number or different numbers.

  In this invention, it is preferable that the compounding quantity of polyethyleneglycol sorbitan ester ether is the range to 0.5 to 5.0 wt% with respect to the whole electrolyte solution. The greater the amount of polyethylene glycol sorbitan ester ether, the more effective it is to prevent corrosion. However, if it exceeds 5.0 wt%, the withstand voltage of the electrolyte tends to decrease. On the other hand, if it is less than 0.5 wt%, corrosion cannot be reliably prevented under a high temperature condition of 115 ° C.

  Examples of carboxylic acids used in the present invention include formic acid, acetic acid, lauric acid, stearic acid, decanoic acid, benzoic acid, salicylic acid, maleic acid, phthalic acid, fumaric acid, succinic acid, glutaric acid, azelaic acid, sebacic acid, Examples include 2-methyl azelaic acid, 1.6-decanedicarboxylic acid, 5.6-decanedicarboxylic acid, 7-vinylhexadecene-1.16-dicarboxylic acid and the like.

  Carboxylic acid salts include ammonium salts, primary amine salts such as methylamine, ethylamine, and t-butylamine, secondary amine salts such as dimethylamine, ethylmethylamine, and diethylamine, trimethylamine, diethylmethylamine, and ethyldimethylamine. And tertiary amine salts such as triethylamine, quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium and tetraethylammonium, and molten salts such as imidazolinium salts.

  As a co-solvent mixed with ethylene glycol, water, glycols such as propylene glycol, lactones such as γ-butyrolactone, N-methyl-2-pyrrolidone, N-methylformamide, N, N-dimethylformamide Amides such as N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoric amide, ethylene carbonate, Examples thereof include carbonates such as propylene carbonate and isobutylene carbonate, nitriles such as acetonitrile, oxides such as dimethyl sulfoxide, ethers, ketones, esters, sulfolane and sulfolane derivatives. These solvents can be used by mixing not only one type but also two or more types.

  Furthermore, in addition to the carboxylic acid, its salt, and solvent, various additives can be added for the purpose of reducing leakage current, improving withstand voltage, and absorbing gas. Examples of additives include phosphoric acid compounds, boric acid compounds, polyhydric alcohols, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene glycol random copolymers and block copolymers A molecular compound, a nitro compound, etc. are mentioned.

In the electrolytic solution according to the present invention, since polyethylene glycol sorbitan ester ether is blended, the lead plate (aluminum portion) drawn from the element and the inner portion (aluminum portion) of the terminal fixed to the sealing plate, etc. Corrosion can be prevented at or near the connecting portion due to, and the reliability of the aluminum electrolytic capacitor can be improved.
In the present invention, corrosion is prevented by the composition of the electrolytic solution, so that the productivity of the aluminum electrolytic capacitor is not reduced.

  In the electrolytic solution for driving an aluminum electrolytic capacitor according to the present invention, at least carboxylic acid or a salt thereof and polyethylene glycol sorbitan ester ether represented by the following chemical formula are blended in a solvent mainly composed of ethylene glycol.

However, in Chemical formula 1, n ₁ , n ₂ , and n ₃ are integers of 4 to 15 and represent the number of oxyethylene groups, and R represents an alkyl group or alkylene group having 12 to 18 carbon atoms. Show.

  In this invention, it is preferable that the compounding quantity of polyethyleneglycol sorbitan ester ether is the range to 0.5 to 5.0 wt% with respect to the whole electrolyte solution.

In the electrolytic solution having such a composition, polyethylene glycol sorbitan ester ether is a compound having a carbonyl group, and when this electrolytic solution is used for an aluminum electrolytic capacitor, it is fixed to a lead plate (aluminum portion) drawn from the element and a sealing plate. Corrosion is prevented at or near the connecting portion by caulking with the inner portion (aluminum portion) of the terminal that is being used.
The reason for this is that polyethylene glycol sorbitan ester ether is attached to the aluminum part, such as the connection part by the crimping between the lead plate pulled out from the element and the inner part of the terminal fixed to the sealing plate by the carbonyl group, or the vicinity thereof. On the other hand, it is considered to preferentially adsorb and form a protective film on the surface to protect the aluminum portion from attack of ionic components such as chlorine and prevent corrosion breakage.
In addition, since polyethylene glycol sorbitan ester ether has a structure having an oxyethylene group, it also has an advantage of being easily dissolved in a solvent such as ethylene glycol.

Hereinafter, based on an Example, this invention is demonstrated more concretely.
First, after the electrolyte solution was prepared with the composition shown in Table 1, the specific resistance of the electrolyte solution at 30 ° C. and the spark generation voltage (withstand voltage of the electrolyte solution) at 85 ° C. were measured. The results are shown in Table 1.

  Next, an electrolytic solution having the composition shown in Table 1 was impregnated into a capacitor element to prepare 100 60-type aluminum electrolytic capacitors each having a diameter of 35.0 mm, a length of 50.0 mm, a rated voltage of 450 V, and a capacitance of 470 μF. This 69-type aluminum electrolytic capacitor has a configuration in which the opening of the case is sealed with a sealing plate, and the lead plate drawn out from the element and the inner portion of the terminal fixed to the sealing plate are connected by caulking. It has a structured.

  Of the above samples, 50 samples were applied with a rated voltage for 5000 hours in a 105 ° C. thermostat, and the remaining 50 samples were applied with a rated voltage for 5000 hours in a 115 ° C. thermostat. After 5000 hours have passed, the aluminum electrolytic capacitor is disassembled, and the lead plate drawn out from the element and the inner portion of the terminal fixed to the sealing plate are connected to the inner portion of the terminal, or the vicinity thereof. The state of occurrence of corrosion and corrosion disconnection was confirmed. The results are shown in Table 2.

  As is apparent from Table 2, in Examples 1 to 10 in which polyethylene glycol sorbitan ester ether was blended, unlike the conventional example, corrosion and corrosion occurred at or near the connecting portion by caulking under a high temperature condition of 105 ° C. No disconnection occurred.

  Of Examples 1 to 10, in Examples 2 to 10, corrosion and corrosion disconnection did not occur at or near the connection portion due to caulking, even under a high temperature condition of 115 ° C.

  Thus, if the electrolyte solution which concerns on Examples 1-10 of this invention is used, corrosion of an aluminum electrolytic capacitor can be prevented. Here, the greater the amount of polyethylene glycol sorbitan ester ether, the more effective is the prevention of corrosion. However, when it exceeds 5.0 wt%, the withstand voltage of the electrolyte tends to decrease as shown in Table 1. Yes (Example 6). Moreover, if it is less than 0.5 wt%, corrosion cannot be reliably prevented under high temperature conditions of 115 ° C. (Example 1). Therefore, the dissolution amount of polyethylene glycol sorbitan ester ether is preferably in the range of 0.5 to 5.0 wt%.

In addition, this invention is not limited to the said Example, The electrolyte solution which melt | dissolved various solutes illustrated previously individually or in multiple, the electrolyte solution which added the additive mentioned above, and the electrolyte solution which mixed the subsolvent are also used. There was an effect equivalent to the said Example.

Claims (2)

An electrolytic solution for driving an aluminum electrolytic capacitor, wherein a solvent containing ethylene glycol as a main component contains at least carboxylic acid or a salt thereof and polyethylene glycol sorbitan ester ether represented by the following chemical formula.

n ₁ , n ₂ , n ₃ : number of oxyethylene groups having 4 to 15 R: alkyl group or alkylene group having 12 to 18 carbon atoms 2. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1, wherein the blending amount of polyethylene glycol sorbitan ester ether is in the range of 0.5 to 5.0 wt% with respect to the entire electrolytic solution.