JP4555158B2 - Electrolytic solution for electrolytic capacitor and electrolytic capacitor - Google Patents

Description

  The present invention relates to an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution) and an electrolytic capacitor, and more particularly to an electrolytic solution with improved withstand voltage.

Conventionally, as an electrolytic solution for medium- and high-pressure aluminum electrolytic capacitors, a solvent such as ethylene glycol blended with a higher dibasic acid or its ammonium salt, boric acid or its ammonium salt, and polyhydric alcohols such as mannitol In this type of electrolytic solution, it is known that boric acid and polyhydric alcohols form an ester compound, and the withstand voltage of the electrolytic solution is improved due to its structural characteristics. As another polyhydric alcohol, it has been proposed to improve the withstand voltage by dissolving polyvinyl alcohol, which is a synthetic polymer (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, mannitol, sorbitol, etc., having about 6 carbon atoms in the main chain, are slow to improve the withstand voltage of the electrolyte even if the blending amount is increased, so a large amount is blended to greatly improve the withstand voltage. With the consequent increase in resistivity. Polyvinyl alcohol, on the other hand, can improve the withstand voltage of the electrolyte solution by adding a smaller amount than mannitol, but it is extremely low in solubility in a solvent containing ethylene glycol as a main component. When preparing a liquid, there exists a problem that heating and stirring for a long time are required.

  In view of the above problems, an object of the present invention is to provide a driving electrolyte solution for an aluminum electrolytic capacitor that can increase a withstand voltage while suppressing an increase in specific resistance, and can be efficiently prepared, and An object of the present invention is to provide an aluminum electrolytic capacitor using this driving electrolyte.

  The present invention has been found as a result of various studies to solve the above-mentioned problems, and was found to be soluble in a solvent in which leuconic acid is a cyclic polyhydric alcohol and contains ethylene glycol as a main component. In view of this, the withstand voltage is improved and the withstand voltage is improved by suppressing the chemical reaction between the electrolytic solution and the electrode foil by the structural effect.

  That is, in the aluminum electrolytic capacitor of the present invention, at least a carboxylic acid or a salt thereof, a leuconic anhydride represented by the following chemical formula (1), and a hydrous leucon represented by the chemical formula (2) in a solvent mainly composed of ethylene glycol. A driving electrolyte solution containing an acid and at least one leuconic acid among hydrous leuconic acids in an intermediate state between the states represented by the chemical formulas (1) and (2) is used.

  Further, in the aluminum electrolytic capacitor of the present invention, the electrolysis for driving formed by blending at least carboxylic acid or a salt thereof and leuconic anhydride represented by the above chemical formula (1) in a solvent mainly composed of ethylene glycol. It is characterized by using a liquid. In this case, even when leuconic anhydride is blended in the electrolytic solution, a part or all of the hydrous leuconic acid represented by the above chemical formula (2) or the above chemical formula ( 1) It is thought that it is the hydrous leuconic acid in the intermediate state of each state shown by (2).

In this invention, it is preferable that the compounding quantity of leuconic acid (an anhydrous leuconic acid or hydrous leuconic acid) is 0.1-5.0 wt% with respect to the whole electrolyte solution.
Here, when both leuconic anhydride and hydrous leuconic acid are added, the total content of these leuconic acids is preferably 0.1 to 5.0 wt%.

  In the present invention, examples of the carboxylic acid include azelaic acid, 2-methylazeleic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, and 7-vinylhexadecene-1,16 which are polycarboxylic acids. -Dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid Thiodipropionic acid and the like, and oxycarboxylic acids such as glycolic acid, lactic acid, tartaric acid, salicylic acid, and mandelic acid. Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid, acrylic acid, methacrylic acid, There are oleic acid, benzoic acid, p-nitrobenzoic acid, anisic acid, cumic acid, cinnamic acid, naphthoic acid, etc. In addition, borodisoxalic acid, borodiglycolic acid, borodisalicylic acid, ethylene glycol borate ester, etc. It can be illustrated.

  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. A tertiary amine salt such as triethylamine N, N-dimethyl-N- (2-methoxyethyl) amine, a quaternary ammonium salt such as tetramethylammonium, triethylmethylammonium and tetraethylammonium, and a molten salt such as an imidazolinium salt. It can be illustrated.

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

  Various additives can be added to the electrolytic solution 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, and polyoxyethylene polyoxypropylene glycol random copolymers and block copolymers. Examples thereof include a polymer compound and a nitro compound.

In the present invention, leuconic acid is in the state of the above chemical formula (1) in the anhydrous state, but becomes water-containing leuconic acid having the above chemical formula (2) in the presence of water. Further, depending on the amount of water, it may be in an intermediate state between the states represented by the chemical formulas (1) and (2).
Here, in the high-pressure electrolyte, even when no moisture is added, moisture contained in the element in advance or condensed water generated by the esterification reaction of solutes and additives is contained. Accordingly, when the capacitor is impregnated with the electrolytic solution according to the present invention, leuconic acid dissolves in the state of hydrous leuconic acid represented by chemical formula (2) or the like even if blended in the anhydrous state represented by chemical formula (1). Will be.

  Unlike conventional straight-chain polyhydric alcohols, this hydrous leuconic acid has a structure in which hydroxyl groups are arranged around a cyclic cyclopentane ring, which contributes to improved withstand voltage due to the surface structure. . For this reason, compared with the linear polyhydric alcohol conventionally used, the significant withstand voltage improvement effect is acquired.

Hydrous leuconic acid has a molecular weight similar to that of mannitol and sorbitol, which have been conventionally used as a withstand voltage improver, but can provide a higher withstand voltage improvement effect.
Furthermore, since the solubility in a solvent is better than that of a polymeric polyhydric alcohol such as polyvinyl alcohol, a predetermined amount can be blended.
Therefore, the withstand voltage can be improved while suppressing an increase in specific resistance, and the thermal stability is excellent, so that the reliability of the product at high temperature can be enhanced. Moreover, leuconic acid has better solubility in a solvent than high molecular weight polyhydric alcohols such as polyvinyl alcohol, so that the electrolytic solution can be prepared efficiently.

A driving electrolyte solution is prepared by dissolving 0.1 to 5.0 wt% of leuconic anhydride in an electrolyte solution containing ethylene glycol as a main solvent and carboxylic acid or a salt thereof as a solute. In such an electrolytic solution, leuconic acid is in an intermediate state between the hydrated leuconic acid represented by the chemical formula (2) or the states represented by the chemical formulas (1) and (2).
When such a driving electrolyte is used for an aluminum electrolytic capacitor, the withstand voltage is improved and the reliability of the product at high temperatures can be improved.
In addition, leuconic acid has better solubility in a solvent than high molecular weight polyhydric alcohols such as polyvinyl alcohol, so that the electrolytic solution can be prepared efficiently.

  Hereinafter, the present invention will be described more specifically based on examples. First, an electrolyte solution was prepared with the composition shown in Tables 1 and 2, and 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 result was obtained. In Table 1, Component A represents leuconic anhydride.

  As can be seen from Table 1, in the electrolytic solution using adipic acid and sebacic acid, all of the electrolytic solutions according to Examples 1, 2, 3, 4, and 5 to which leuconic anhydride was added had a higher withstand voltage than Conventional Example 1. Has improved. In addition, the electrolytic solutions according to Examples 2, 3, and 4 to which leuconic anhydride was added have lower specific resistance and higher withstand voltage than those of Conventional Example 2 to which polyvinyl alcohol as a withstand voltage improver is added.

  Here, if the blending amount of leuconic anhydride is less than 0.1 wt% (Example 1), the effect of improving the withstand voltage is not sufficient, and if it exceeds 5.0 wt% (Example 5), the specific resistance becomes high and low. Unsuitable for specific resistance applications. Therefore, the dissolution amount of leuconic anhydride is preferably in the range of 0.1 to 5.00 wt%.

  In addition, this invention is not limited to an Example, As shown in Table 2, the electrolytic solution which melt | dissolved various solutes illustrated previously individually or severally, the electrolyte solution which added the other additive, and a subsolvent The mixed electrolyte solution had the same effect as the example.

  Moreover, in the said form, at the time of preparation of electrolyte solution, although leuconic anhydride was added as leuconic acid, you may add the one part or the whole as hydrous leuconic acid.

Claims (4)

In a solvent mainly composed of ethylene glycol, at least carboxylic acid or a salt thereof, leuconic anhydride represented by the following chemical formula (1), hydrous leuconic acid represented by chemical formula (2), and chemical formulas (1), (2 An electrolytic solution for driving an electrolytic capacitor, comprising at least one of hydrated leuconic acids in an intermediate state between the states shown in FIG.

  An electrolytic solution for driving an electrolytic capacitor, comprising at least carboxylic acid or a salt thereof and leuconic anhydride represented by the above chemical formula (1) in a solvent containing ethylene glycol as a main component.   The electrolytic solution for driving an electrolytic capacitor, wherein the content of leuconic anhydride or hydrous leuconic acid according to claim 1 or 2 is 0.1 to 5.0 wt% with respect to the whole electrolytic solution.   4. An electrolytic capacitor using the driving electrolyte defined in any one of claims 1 to 3.