JP2008078687A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic solution for medium-high voltage having a high sparking voltage, high conductivity, proper leakage current characteristics and durability characteristics. <P>SOLUTION: By dissolving three-dodecyl adipic acid or its salt in a solvent having ethylene glycol, and adding boric acid and propylene glycol, etc. into the solvent as main components, the sparking voltage of a resultant solution is improved. Furthermore, by adding 1,6-decanoic dicarboxylic acid, 5,6-decanoic dicarboxylic acid, etc., into the solution, an electrolytic solution having a high sparking voltage, high electrical conductivity, proper formation property can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolytic solution for electrolytic capacitors, and more particularly to an electrolytic solution for medium to high pressure.

  The electrolytic solution for the electrolytic capacitor uses a valve metal having an insulating oxide film formed on the surface of aluminum or tantalum as an anode electrode, and the oxide film layer is a dielectric, and an electrolyte layer is formed on the surface of the oxide film layer. And an electrode for current collection, usually called a cathode, is arranged.

  The electrolytic solution for electrolytic capacitors directly contacts the dielectric layer as described above and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric of the electrolytic capacitor and the current collecting cathode, and the resistance component of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristics of the electrolytic solution are a major factor that affects the characteristics of the electrolytic capacitor.

  In the prior art of electrolytic capacitors, an electrolytic solution in which boric acid or ammonium borate is dissolved as a solute in a solvent made of ethylene glycol has been used because a spark voltage is relatively high as an electrolytic solution for medium and high pressures. However, in such an electrolytic solution, since the electrical conductivity is low, and a large amount of water is produced by esterification of ethylene glycol and boric acid, the internal pressure increases due to evaporation of water at 100 ° C. or higher, and aluminum that is an electrode The problem of being easy to react with the liquid also occurred, and it was not suitable for use at high temperatures.

In order to solve these disadvantages, organic dicarboxylic acids such as sebacic acid and azelaic acid are sometimes used, but these have low solubility, so that crystals are likely to precipitate at low temperatures, which deteriorates the low temperature characteristics of capacitors. I couldn't escape the drawback of making it happen. Furthermore, there are examples using butyloctanedioic acid as a solute (Patent Document 1) and examples using 5,6-decanedicarboxylic acid as a solute (Patent Document 2). Electrolytic solutions using these dibasic acids or their salts have high spark voltage and electrical conductivity, are very slow in esterification, and produce little water, so that stability at high temperatures can be obtained.
Japanese Patent Publication No. 60-13296 Japanese Patent Publication No. 63-15738

  However, in recent years, electronic devices using a switching power supply have been widely used in general households, and the demand for safety of aluminum electrolytic capacitors has increased. In other words, an overvoltage may be applied to the aluminum electrolytic capacitor used on the primary side of the switching power supply due to the instability of the supplied power. In this case, the capacitor is destroyed, and a situation of ignition and combustion occurs. In some cases, safety measures are in place to prevent this situation. In order to improve the safety of this electrolytic capacitor, it is desired to further improve the spark voltage of the electrolytic solution for the electrolytic capacitor to improve the overvoltage characteristics of the electrolytic capacitor.

  An object of the present invention is to provide an electrolyte solution for medium and high pressures that has a high spark voltage and electrical conductivity, and also has good leakage current characteristics and life characteristics.

  In order to solve the above problems, an electrolytic solution for an electrolytic capacitor according to a first invention is obtained by dissolving 3-dodecyladipic acid or a salt thereof in a solvent mainly composed of ethylene glycol, boric acid, propylene glycol, glycerin, pentaerythritol. In addition, one or more of mannit, sorbit, zurichite, 1,3-butanediol, and polyvinyl alcohol are added.

  Furthermore, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid, benzoic acid were added to the electrolyte solution. In addition, one or more of sebacic acid, azelaic acid, adipic acid or salts thereof are added.

  As described above, the electrolytic solution for an electrolytic capacitor of the present invention dissolves 3-dodecyladipic acid or a salt thereof in a solvent mainly composed of ethylene glycol, boric acid, propylene glycol, glycerin, pentaerythritol, mannitol. , Sorbit, Zursisite, 1,3-butanediol, or one or more of polyvinyl alcohol is added. This improves the spark voltage and improves the overvoltage characteristics of the electrolytic capacitor.

  Furthermore, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid, benzoic acid were added to the electrolyte solution. By adding one or more of sebacic acid, azelaic acid, adipic acid or salts thereof, an electrolytic solution having a high spark voltage and high electrical conductivity and a good chemical property can be obtained. The overvoltage performance of the capacitor is further improved.

In general, as the carbon number of the organic carboxylic acid used in the electrolytic solution of the electrolytic capacitor increases, the spark voltage increases for a certain concentration, but the solubility decreases accordingly, so the conductivity is increased by increasing the concentration. It cannot be raised. However, although 3-dodecyl adipic acid has a total carbon number of 18 and a higher carbon number than conventional organic carboxylic acids, it has a high solubility in ethylene glycol, so an electrolyte with high conductivity and high spark voltage can be realized. . On the other hand, since the chemical conversion is inferior, there is a drawback that heat generation is large when repairing the deterioration of the anodized film, and as a result, the characteristics of the capacitor cannot be stably maintained for a long time.

  However, as in the present invention, boric acid and propylene glycol, glycerin, pentaerythritol, mannitol, sorbit, zulsisite, 1,3-butanediol, polyvinyl alcohol are dissolved in an electrolytic solution in which 3-dodecyladipic acid or a salt thereof is dissolved. The spark voltage can be improved by adding one or more of the above. This further improves the safety when an overvoltage is applied to the capacitor.

  Further, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid, benzoic acid, sebacic acid, azelain By using one or more of acid, adipic acid, or salts thereof in combination, the chemical conversion of the electrolytic solution is improved, and a capacitor having stable characteristics for a long time can be obtained. Further, the conductivity can be improved by increasing the concentration of these carboxylic acids.

  The addition concentration of boric acid is 0.1 to 30% by weight, preferably 1 to 10% by weight, and the concentration of propylene glycol and the like is 0.1 to 20% by weight, preferably 1 to 10%. The effect is small, and if it exceeds this, the conductivity will decrease.

  Examples of the present invention will be described below.

  (Table 1) to (Table 3) show the composition, spark voltage, and conductivity of the electrolytic solutions for electrolytic capacitors of Examples and Comparative Examples of the electrolytic solution.

As is clear from (Table 1) to (Table 3), the spark voltage is improved in the example as compared with the comparative example.

Claims (2)

In a solvent mainly composed of ethylene glycol, 3-dodecyladipic acid or a salt thereof is dissolved, and boric acid and propylene glycol, glycerin, pentaerythritol, mannitol, sorbit, zuriscit, 1,3-butanediol, polyvinyl alcohol An electrolytic solution for electrolytic capacitors to which one or more of them are added. 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9-decanedicarboxylic acid, benzoic acid, sebacic acid, azelaic acid, An electrolytic solution for electrolytic capacitors to which adipic acid or one or more of these salts are added.