JP2014130854A - Electrolyte for electrolytic capacitor and electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for an electrolytic capacitor, which has a high spark voltage and is excellent in heat resistance in spark voltage and electrical conductivity, and to provide an electrolytic capacitor using the same.SOLUTION: The electrolyte for an electrolytic capacitor contains an electrolyte salt containing a nitrogen-containing cation, a colloidal silica, and an organic solvent. The colloidal silica contains as surface modifying groups an OH group and an ONHgroup at a content ratio of 1:25 to 99:75.

Description

  The present invention relates to an electrolytic solution for an electrolytic capacitor having a high spark voltage and excellent heat resistance in terms of spark voltage and conductivity, and an electrolytic capacitor using the same.

  Conventionally, as an electrolytic solution for an electrolytic capacitor, a solution obtained by dissolving an organic acid, an inorganic acid, or a salt thereof in an organic solvent as an electrolytic solution is used.

  Among the characteristics of the electrolyte, conductivity is directly related to the loss and impedance characteristics of electrolytic capacitors, and if the withstand voltage is low, a short circuit or ignition may occur, but the spark voltage is an indicator of withstand voltage. Development of electrolytic solutions for electrolytic capacitors having high electrical conductivity and spark voltage has been actively conducted.

  For example, as disclosed in Patent Document 1, sulfamic acid, suberic acid, dodecyl phosphate, porous polyimide, and the like are known as additives for improving the spark voltage. In either case, the initial spark voltage was excellent, but it deteriorated as soon as it was used, resulting in poor heat resistance.

  Patent Document 2 discloses a technique using silica colloidal particles, which are inorganic oxide colloidal particles, in order to improve the spark voltage while maintaining high electrical conductivity. However, the electrolyte containing silica colloidal particles has a problem of short-circuiting because it gels during use, although the initial spark voltage is high.

  On the other hand, Patent Document 3 discloses an electrolytic solution for an electrolytic capacitor containing colloidal silica stabilized with ammonia. Although this electrolytic solution has a certain spark voltage and heat resistance, it has further heat resistance. There was a need for improvement.

JP 2009-283581 A JP 05-6839 A JP 2011-108675 A

  Accordingly, an object of the present invention is to provide an electrolytic solution for an electrolytic capacitor that has a high spark voltage and is excellent in heat resistance at the spark voltage and conductivity, and an electrolytic capacitor using the electrolytic solution.

As a result of intensive studies to solve the above problems, the present inventors have found that an electrolytic solution containing a nitrogen-containing cation, colloidal silica, and an organic solvent contains an OH group as a surface modifying group. By using colloidal silica having an ONH ₄ group in a specific ratio, it was found that a high spark voltage was exhibited, and the heat resistance in the spark voltage and conductivity was remarkably improved, and the present invention was completed.

That is, the present invention contains an electrolyte salt containing a nitrogen-containing cation, colloidal silica, and an organic solvent, and the colloidal silica contains OH groups and ONH ₄ groups as surface modifying groups in a content ratio of 1:25 to 99:75. It is electrolyte solution for electrolytic capacitors characterized by including.

  Moreover, this invention is electrolyte solution for electrolytic capacitors which contains 1-100 ppm of sulfate ions further.

  Moreover, this invention is an electrolytic capacitor using the said electrolyte solution.

Further, the present invention provides a colloidal containing an OH group and an ONH ₄ group as a surface modifying group in a content ratio of 1:25 to 99:75 in an electrolytic solution for an electrolytic capacitor containing an electrolyte salt containing a nitrogen-containing cation and an organic solvent. It is a method for improving the spark voltage of an electrolytic solution for an electrolytic capacitor, and heat resistance in the spark voltage and conductivity, characterized by adding silica.

  The electrolytic solution for an electrolytic capacitor of the present invention has a high spark voltage and excellent heat resistance in terms of spark voltage and conductivity. By using this, a high withstand voltage is maintained over a long period of time even at high temperatures. An electrolytic capacitor that can be obtained can be obtained.

  The electrolytic solution for electrolytic capacitors of the present invention will be described.

<Colloidal silica>
The electrolytic solution for electrolytic capacitors of the present invention contains an electrolyte salt containing a nitrogen-containing cation, colloidal silica, and an organic solvent. Among these, colloidal silica includes OH groups and ONH ₄ groups in a content ratio of 1:25 to 99:75 as surface modification groups. That is, acid-type colloidal silica having an OH group as a surface modification group and ammonia-stable colloidal silica having an ONH ₄ group as a surface modification group are known. In the present invention, both an OH group and an ONH ₄ group are contained. By using colloidal silica, compared with acid type colloidal silica or ammonia stable type colloidal silica, the spark voltage is improved, and the effect of significantly improving the heat resistance in the spark voltage and conductivity can be obtained. The content of OH groups and ONH ₄ groups in the surface modifying group, OH group is 1% to 25%, preferably a ONH ₄ groups 75 to 99% OH groups 5 to 20% ONH ₄ groups 80 More preferably, it is -95%. Moreover, the content ratio of OH groups and ONH ₄ groups is in the range of 1:99 to 25:75, and more preferably 5:95 to 20:80. When the content and content ratio of the OH group and the ONH ₄ group are in such a range, the effect of improving the spark voltage and the effect of improving the heat resistance in the spark voltage and the conductivity are excellent. In the present invention, the content of OH groups and ONH ₄ groups in the surface modification group of colloidal silica and the content ratio of OH groups and ONH ₄ groups are values determined by the methods described in the examples.

  Although the average particle diameter of colloidal silica is not specifically limited, Preferably it is 1-50 nm, More preferably, it is 5-40 nm, Most preferably, it is 10-30 nm. By using a material having such an average particle size, an electrolytic solution for electrolytic capacitors excellent in dispersibility in a solvent can be obtained.

  The shape of the colloidal silica may be any of a spherical type, a chain type, and a cyclic type in which colloidal silica is aggregated in a ring and dispersed in a solvent.

The colloidal silica used in the present invention can be obtained, for example, by mixing acid colloidal silica and ammonia stable colloidal silica in a ratio of 1:99 to 25:75, preferably 5:95 to 20:80. . Moreover, when ammonia is added to acid-type colloidal silica and the pH is adjusted to 9 to 10, all OH groups are replaced with ONH ₄ groups. By terminating the reaction at pH 8 to 8.9, the surface modification group of colloidal silica is increased. The content and content ratio of the OH group and the ONH ₄ group can be adjusted within the above range. As acid-type colloidal silica and ammonia-stable colloidal silica, Snowtex-O (acid type, surface modification group is OH group, manufactured by Nissan Chemical Co., Ltd.), Snowtex-N (ammonia stable type, surface modification group is ₄ ONH groups, Commercial products such as those manufactured by Nissan Chemical Co., Ltd. can be used.

  Colloidal silica is hardly soluble in water or organic solvents, and is generally added to an electrolyte as a colloidal solution dispersed in water, ethylene glycol, γ-butyrolactone, or other suitable dispersion solvent, and used as an electrolytic capacitor. Also used in a dispersed state.

  The content of colloidal silica in the electrolytic solution for electrolytic capacitors of the present invention is preferably 0.1 to 20% by mass, more preferably 0.2 to 15% by mass, and particularly preferably 0.3 to 10% by mass. It is. If the amount is less than 0.1% by mass, the effect of improving the electrical characteristics of the electrolytic capacitor may be small. If the amount exceeds 20% by mass, the viscosity may increase and it may be difficult to handle.

<Sulfate ion>
Furthermore, sulfuric acid, aluminum sulfate, magnesium sulfate, ammonium sulfate, dimethyl sulfate, diethyl sulfate, titanium sulfate, sodium sulfate, and the like are added to the electrolytic solution for electrolytic capacitors of the present invention, so that sulfate ion is 1 to 100 ppm, preferably 1 By containing ˜50 ppm, the spark voltage can be further improved.

<Electrolyte salt>
The electrolyte salt used in the present invention contains a nitrogen-containing cation, and specifically, one or more selected from the group consisting of compounds represented by the following general formulas (1) to (5). Is used.

In the formulas (1) to (5), the groups R ^{1 to} R ²⁵ are each the same or different hydrogen, a C 1-18 alkyl group, a C 1-18 alkoxy group or a hydroxyl group, and R Adjacent groups of ^{1 to} R ²⁵ may be linked to form an alkylene group having 2 to 6 carbon atoms. X < ^- > is a carboxylate anion or a boron compound anion.

  Specific examples of the cation moiety of the compound represented by the general formula (1) include an ammonium cation; a tetramethylammonium cation, a tetraethylammonium cation, a tetrapropylammonium cation, a tetraisopropylammonium cation, a tetrabutylammonium cation, and a trimethylethylammonium cation. , Triethylmethylammonium cation, dimethyldiethylammonium cation, dimethylethylmethoxyethylammonium cation, dimethylethylmethoxymethylammonium cation, dimethylethylethoxyethylammonium cation, trimethylpropylammonium cation, dimethylethylpropylammonium cation, triethylpropylammonium cation, spiro- (1,1 ') Quaternary ammonium cations such as bipyrrolidinium cation, piperidine-1-spiro-1′-pyrrolidinium cation, spiro- (1,1 ′)-bipiperidinium cation; trimethylamine cation, triethylamine cation, tripropylamine Cation, triisopropylamine cation, tributylamine cation, diethylmethylamine cation, dimethylethylamine cation, diethylmethoxyamine cation, dimethylmethoxyamine cation, dimethylethoxyamine cation, diethylethoxyamine cation, methylethylmethoxyamine cation, N-methylpyrrolidine Cation, N-ethylpyrrolidine cation, N-propylpyrrolidine cation, N-isopropylpyrrolidine cation, N-butylpyrrolidine Tertiary ammonium cations such as cations, N-methylpiperidine cations, N-ethylpiperidine cations, N-propylpiperidine cations, N-isopropylpiperidine cations, N-butylpiperidine cations; dimethylamine cations, diethylamine cations, diisopropylamine cations, di Secondary grades such as propylamine cation, dibutylamine cation, methylethylamine cation, methylpropylamine cation, methylisopropylamine cation, methylbutylamine cation, ethylisopropylamine cation, ethylpropylamine cation, ethylbutylamine cation, isopropylbutylamine cation, pyrrolidine cation An ammonium cation etc. are mentioned.

  Among these, the ammonium cation, the tetraethylammonium cation, the triethylmethylammonium cation, and the spiro- (1,1 ′)-bipyrrolidinium cation are superior because they are excellent in the spark voltage and / or conductivity improvement effect and heat resistance improvement effect. N-methylpyrrolidine cation, dimethylethylamine cation, diethylmethylamine cation, trimethylamine cation, triethylamine cation, diethylamine cation and the like are preferably used.

  Specific examples of the cation moiety of the compound represented by the general formula (2) include tetramethylimidazolium cation, tetraethylimidazolium cation, tetrapropylimidazolium cation, tetraisopropylimidazolium cation, tetrabutylimidazolium cation, 1, 3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1,3-dipropylimidazolium cation, 1,3-diisopropylimidazolium cation, 1,3-dibutylimidazolium cation, 1-methyl-3- Ethyl imidazolium cation, 1-ethyl-3-methyl imidazolium cation, 1-butyl-3-methyl imidazolium cation, 1-butyl-3-ethyl imidazolium cation, 1,2,3-trimethyl imidazole Cation, 1,2,3-triethylimidazolium cation, 1,2,3-tripropylimidazolium cation, 1,2,3-triisopropylimidazolium cation, 1,2,3-tributylimidazolium cation, 1 , 3-dimethyl-2-ethylimidazolium cation, 1,2-dimethyl-3-ethyl-imidazolium cation, and the like. Among these, tetramethylimidazolium cation, tetraethyl imidazolium cation, 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl, because of high conductivity and excellent heat resistance improvement effect -3-Methylimidazolium cation or the like is preferably used.

  Specific examples of the cation moiety of the compound represented by the general formula (3) include tetramethylimidazolinium cation, tetraethylimidazolinium cation, tetrapropylimidazolinium cation, tetraisopropylimidazolinium cation, and tetrabutylimidazoli. Cation, 1,3,4-trimethyl-2-ethylimidazolinium cation, 1,3-dimethyl-2,4-diethylimidazolinium cation, 1,2-dimethyl-3,4-diethylimidazolinium cation 1-methyl-2,3,4-triethylimidazolinium cation, 1,2,3-trimethylimidazolinium cation, 1,2,3-triethylimidazolinium cation, 1,2,3-tripropylimidazole Linium cation, 1,2,3-triisopro Louis imidazolinium cation, 1,2,3-tributylimidazolinium cation, 1,3-dimethyl-2-ethylimidazolinium cation, 1-ethyl-2,3-dimethylimidazolinium cation, 4-cyano- 1,2,3-trimethylimidazolinium cation, 3-cyanomethyl-1,2-dimethylimidazolinium cation, 2-cyanomethyl-1,3-dimethylimidazolinium cation, 4-acetyl-1,2,3- Trimethylimidazolinium cation, 3-acetylmethyl-1,2-dimethylimidazolinium cation, 4-methylcarbooxymethyl-1,2,3-trimethylimidazolinium cation, 3-methylcarbooxymethyl-1,2 -Dimethylimidazolinium cation, 4-methoxy-1,2,3- Limethylimidazolinium cation, 3-methoxymethyl-1,2-dimethylimidazolinium cation, 4-formyl-1,2,3-trimethylimidazolinium cation, 3-formylmethyl-1,2-dimethylimidazoli Cation, 3-hydroxyethyl-1,2-dimethylimidazolinium cation, 4-hydroxymethyl-1,2,3-trimethylimidazolinium cation, 2-hydroxyethyl-1,3-dimethylimidazolinium cation, etc. Is mentioned. Among these, tetramethylimidazolinium cation, tetraethylimidazolinium cation, 1,2,3-trimethylimidazolinium cation, 1,2,3-triethyl have high conductivity and are excellent in heat resistance improvement effect. An imidazolinium cation and a 1-ethyl-3-methylimidazolinium cation are preferably used.

  Specific examples of the cation moiety of the compound represented by the general formula (4) include tetramethyl pyrazolium cation, tetraethyl pyrazolium cation, tetrapropyl pyrazolium cation, tetraisopropyl pyrazolium cation, tetrabutyl pyrazo Rium cation, 1,2-dimethylpyrazolium cation, 1-methyl-2-ethylpyrazolium cation, 1,2-diethylpyrazolium cation, 1,2-dipropylpyrazolium cation, 1,2- Dibutylpyrazolium cation, 1-methyl-2-propylpyrazolium cation, 1-methyl-2-butylpyrazolium cation, 1-methyl-2-hexylpyrazolium cation, 1-methyl-2-octylpyra Zorium cation, 1-methyl-2-dodecylpyrazolium cation, 1, , 3-trimethylpyrazolium cation, 1,2,3-triethylpyrazolium cation, 1,2,3-tripropylpyrazolium cation, 1,2,3-triisopropylpyrazolium cation, 1,2 , 3-tributylpyrazolium cation, 1-ethyl-2,3,5-trimethylpyrazolium cation, 1-ethyl-3-methoxy-2,5-dimethylpyrazolium cation, 3-phenyl-1,2 , 5-trimethylpyrazolium cation, 3-methoxy-5-phenyl-1-ethyl-2-ethylpyrazolium cation, 1,2-tetramethylene-3,5-dimethylpyrazolium cation, 1,2- Tetramethylene-3-phenyl-5-methylpyrazolium cation, 1,2-tetramethylene-3-methoxy-5-methylpyrazolium Thione, and the like. Among these, tetramethylpyrazolium cation, tetraethylpyrazolium cation, 1,2-dimethylpyrazolium cation, 1,2-diethylpyrazolium cation because of high conductivity and excellent heat resistance improvement effect A cation, 1-methyl-2-ethylpyrazolium cation, etc. are preferably used.

  Specific examples of the cation moiety of the compound represented by the general formula (5) include N-methylpyridinium cation, N-ethylpyridinium cation, N-propylpyridinium cation, N-isopropylpyridinium cation, N-butylpyridinium cation, N -Hexylpyridinium cation, N-octylpyridinium cation, N-dodecylpyridinium cation, N-methyl-3-methylpyridinium cation, N-ethyl-3-methylpyridinium cation, N-propyl-3-methylpyridinium cation, N-butyl Examples include -3-methylpyridinium cation, N-butyl-4-methylpyridinium cation, and N-butyl-4-ethylpyridinium cation. Among these, N-methylpyridinium cation, N-ethylpyridinium cation, N-butylpyridinium cation, N-butyl-3-methylpyridinium cation and the like are preferably used because they exhibit high conductivity and are excellent in heat resistance improvement effect. It is done.

The anion X ⁻ combined with the cation is a carboxylate anion or a boron compound anion. The carboxylic acid anion is an anion of an organic carboxylic acid such as an aromatic carboxylic acid or an aliphatic carboxylic acid, and the organic carboxylic acid may have a substituent. Specifically, phthalate anion, salicylate anion, isophthalate anion, terephthalate anion, trimellitic acid anion, pyromellitic acid anion, benzoic acid anion, resorcinic acid anion, cinnamic acid anion, naphthoic acid anion, mandelic acid anion Aromatic carboxylic acid anions such as: oxalate anion, malonate anion, succinate anion, glutarate anion, adipate anion, pimelate anion, suberate anion, azelaic acid anion, sebacic acid anion, undecanedioic acid anion, dodecane Diacid anion, tridecanedioic acid anion, tetradecanedioic acid anion, pentadecanedioic acid anion, hexadecanedioic acid anion, 3-tert-butyladipate anion, methylmalonate anion, ethylmalamate Acid anion, propylmalonate anion, butylmalonate anion, pentylmalonate anion, hexylmalonate anion, dimethylmalonate anion, diethylmalonate anion, methylpropylmalonate anion, methylbutylmalonate anion, ethylpropylmalonate Anion, dipropyl malonate anion, methyl succinate anion, ethyl succinate anion, 2,2-dimethyl succinate anion, 2,3-dimethyl succinate anion, 2-methyl glutarate anion, 3-methyl glutarate anion, 3- Methyl-3-ethyl glutarate anion, 3,3-diethyl glutarate anion, methyl succinate anion, 2-methyl glutarate anion, 3-methyl glutarate anion, 3,3-dimethyl glutarate anion, -Methyl adipate anion, 1,6-decanedicarboxylate anion, 5,6-decanedicarboxylate anion, formate anion, acetate anion, propionate anion, butyrate anion, isobutyrate anion, valerate anion, caproate anion, enanthate Acid anion, caprylate anion, pelargonate anion, laurate anion, myristic acid anion, stearate anion, behenate anion, undecanoate anion, borate anion, borodiglycolate anion, borodisoxalate anion, borodisalicylate anion, Saturated carboxylate and maleate anions such as borodiazelaic acid anion, borodilactic acid anion, itaconic acid anion, tartrate anion, glycolate anion, lactate anion, pyruvate anion And an aliphatic carboxylic acid anion containing an unsaturated carboxylic acid such as a fumarate anion, an acrylic acid anion, a methacrylic acid anion, and an oleic acid anion. These may be used alone or in combination of two or more. Among these, phthalate anion, maleate anion, salicylate anion, benzoate anion, adipate anion, azelate anion, 1,6-decanedicarboxylate anion, because the spark voltage is improved and is thermally stable. Preferable examples include 3-tert-butyl adipate anion.

  Examples of the boron compound anion include a borate anion, a borodiazelate anion, a borodisalicylate anion, a borodiglycolate anion, a borodilactic acid anion, and a borodisoxalate anion. Among these, a borate anion, a borodisalicylate anion, a borodiglycolate anion, etc. are preferably used from the point which is excellent in a spark voltage.

  Among the above-mentioned anions, when used for an electrolytic capacitor for low to medium pressure, phthalate anion, maleate anion, salicylate anion, benzoate anion, adipate anion, borodisalicylate anion, borodiglycolate anion, etc. are preferably used. High electrical conductivity and excellent heat resistance. On the other hand, when used in an electrolytic capacitor for high voltage, azelaic acid anion, 1,6-decanedicarboxylic acid anion, 3-tert-butyladipate anion, borate anion, borodisalicylate anion, borodiglycolate anion, etc. It is suitably used, and an excellent effect in spark voltage and heat resistance can be obtained.

  Among the compounds represented by the general formulas (1) to (5), the compound represented by the general formula (1) is stable over a long period of time, can obtain a high spark voltage, and is also heat resistant. Since it is excellent, it is preferably used. Specifically, electrolyte salts used for low and medium pressure electrolytic capacitors include dimethylethylamine phthalate, tetraethylammonium maleate, diethylamine phthalate, spiro- (1,1 ′)-bipyrrolidinium maleate, 1-ethyl phthalate Examples include 3-methylimidazolinium, 1-methyl-2-ethylpyrazolium phthalate, N-butylpyridinium phthalate, and tetramethylimidazolinium phthalate. On the other hand, as electrolyte salts used for high-voltage electrolytic capacitors, diethylamine azelate, trimethylamine azelate, ammonium azelate, ammonium 1,6-decanedicarboxylate, diethylamine 1,6-decanedicarboxylate, 1,6-decanedicarboxylic acid Trimethylamine, N-methylpyrrolidine borodisalicylate and the like are preferably used.

  The content of the electrolyte salt selected from the group consisting of the compounds represented by the general formulas (1) to (5) in the electrolytic solution for electrolytic capacitors of the present invention is preferably 1 to 70% by mass, and 3 to 60% by mass. More preferred is 5 to 50% by mass. If it is less than 1% by mass, sufficient electrical conductivity may not be obtained, and if it exceeds 70% by mass, the viscosity of the electrolytic solution may be increased and sufficient electrical conductivity may not be obtained.

<Organic solvent>
The organic solvent used for the electrolytic solution for the electrolytic capacitor can be a protic polar solvent or an aprotic polar solvent, and may be used alone or in combination of two or more.

  Protic polar solvents include monohydric alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds ( Ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.).

  Examples of the aprotic polar solvent include γ-butyrolactone, γ-valerolactone, amide type (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoricamide, etc.), sulfolane (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc.), chain sulfone (Dimethylsulfone, ethylmethylsulfone, ethylisopropylsulfone), cyclic amide (N-methyl-2-pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitrile (acetonitrile, etc.) , Sulfoxide (dimethylsulfoxide, etc.), 2-imidazolidinone [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidi) Non, 1,3-di (n-propyl) -2-imidazolidinone), 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone, etc.) )] And the like.

  When used for an electrolytic capacitor for low and medium pressure, a solvent containing γ-butyrolactone as a main solvent is preferably used. The content of γ-butyrolactone in the organic solvent is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Moreover, the water content in the case of low and medium pressure is specifically preferably 2.0% by mass or less, and more preferably 1.0% by mass or less. On the other hand, the solvent used in the electrolytic capacitor for high voltage is preferably one having ethylene glycol as the main solvent, preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more in the organic solvent. . Moreover, in the case of high pressure, it may contain moisture, specifically 0.5 to 10.0% by mass, more preferably 1.0 to 5.0% by mass. By using such a moisture content, the chemical conversion to the electrode foil is enhanced and a high spark voltage is obtained.

<Additives>
The electrolytic solution for electrolytic capacitors of the present invention may contain an additive. Additives include polyvinyl alcohol, dibutyl phosphoric acid or phosphoric acid compound of phosphorous acid, boric acid, mannit, complex compounds such as boric acid and mannit, sorbit and boric acid and polyhydric alcohols such as ethylene glycol and glycerin And nitro compounds such as o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, and p-nitrophenol.

  0.1-10 mass% is preferable and, as for the addition amount of the said additive, 0.5-5.0 mass% is more preferable. If it is less than 0.1% by mass, a sufficient spark voltage may not be obtained, and if it exceeds 10% by mass, the conductivity may decrease.

  The electrolytic solution of the present invention can be produced by mixing the above essential components and optional components added as necessary according to a conventional method.

<Electrolytic capacitor>
The electrolytic capacitor of the present invention is characterized by using the above-described electrolytic solution for electrolytic capacitors. Hereinafter, an aluminum electrolytic capacitor will be described as an example.

  An aluminum electrolytic capacitor uses, as an anode electrode, a chemical conversion foil in which an oxide film is formed on a surface of an aluminum foil by anodization as a dielectric, and a cathode electrode is disposed opposite to the anode electrode. An electrolytic capacitor is formed by interposing a separator and holding an electrolytic solution therein.

  As performance required for the electrolytic capacitor for low and medium pressure, the electric conductivity is preferably 5 to 50 mS / cm, more preferably 6 to 30 mS / cm, and particularly preferably 7 to 20 mS / cm. The spark voltage is preferably 160 to 400V, more preferably 190 to 350V, and particularly preferably 220 to 300V.

  As performance required for electrolytic capacitors for high voltage, the electric conductivity is preferably 1 to 7 mS / cm, more preferably 1.5 to 6 mS / cm, and particularly preferably 2 to 5 mS / cm. The spark voltage is preferably 500 to 1000 V, more preferably 550 to 900 V, particularly preferably 600 to 850 V, and further preferably 650 to 800 V.

  Conventional electrolytic capacitors using an electrolytic solution containing colloidal silica and an electrolyte salt are excellent in the initial spark voltage, but colloidal silica aggregates and polymerizes during use under high temperature conditions, etc., and gelation occurs. As a result, the spark voltage is reduced. On the other hand, the electrolytic capacitor using the electrolytic solution of the present invention has a spark voltage higher than that of the conventional one, and has a high heat resistance with almost no decrease in the spark voltage even under high temperature conditions. The reason for this is not clear, but colloidal silica having a specific surface modification group has high charge balance stability, which suppresses aggregation, and together with sulfate ions, prevents hydration of the oxide film on the electrode and prevents its deterioration. Since it suppresses, it is estimated that a spark voltage improves and heat resistance is improved.

  Hereinafter, the present invention will be described based on examples and the like. In addition, this invention is not limited at all by the Example etc. In the examples, “part” represents “part by mass”, and “%” represents “% by mass” (however, the content of the surface modifying group of colloidal silica simply means “%”).

Reference example 1
(Preparation of ethylene glycol dispersion of acid-type colloidal silica)
Commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group) 20% aqueous dispersion 500 parts and ethylene glycol 400 parts are mixed, Concentration at 60 ° C. yielded 500 parts of colloidal silica ethylene glycol dispersion.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of an ethylene glycol dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption analyzer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of content ratio of surface modification group of colloidal silica)
5 μl of an ethylene glycol dispersion of colloidal silica was sampled and applied onto a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby preparing a uniform sample thin film. The thin film of the obtained sample was measured by the infrared absorption spectrum method, and it was confirmed that the peak at a wavelength of 3700 cm ⁻¹ was attributed to an OH group and there was no ONH ₄ group peak. The peak area (A ₀ ) of the peak attributed to the OH group was measured.

Reference example 2
(Synthesis of ammonia stable colloidal silica and preparation of ethylene glycol dispersion)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 9.0 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of ethylene glycol was mixed and concentrated at 60 ° C. to obtain 500 parts of an ethylene glycol dispersion of colloidal silica.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of an ethylene glycol dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption analyzer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of content ratio of surface modification group of colloidal silica)
5 μl of an ethylene glycol dispersion of colloidal silica was sampled and applied onto a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby preparing a uniform sample thin film. The thin film of the obtained sample was measured by the infrared absorption spectrum method, and it was confirmed that the peak of wavelengths 3030 cm ^{−1 to} 3330 cm ⁻¹ was attributed to ₄ groups of ONH, and there was no peak of OH group. Regarding peaks attributed with ONH ₄ group was determined and the peak area _(B 0).

Production Example 1
(Synthesis of colloidal silica 1)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 8.9 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of ethylene glycol was mixed and concentrated at 60 ° C. to obtain 500 parts of an ethylene glycol dispersion of colloidal silica.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of an ethylene glycol dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption analyzer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of content ratio of surface modification group of colloidal silica)
5 μl of an ethylene glycol dispersion of colloidal silica was sampled and applied onto a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby forming a uniform sample thin film. Thin film of the obtained sample was subjected to measurement by infrared absorption spectroscopy, attributing peak wavelengths 3700 cm ^-1 and OH groups, and the peak wavelength ^{3030cm -1 ~3330cm} -1 attributed with ONH ₄ group. The peak area (A) of the peak attributed to the OH group (A) and the peak area (B) of the peak attributed to the ONH ₄ group were determined, and the content of the OH group or ONH ₄ group in the surface modification group was calculated by the following formula. .
OH group content (%) = A / A ₀ × 100
ONH ₄ group content (%) = B / B ₀ × 100
As a result, the OH group content was 1%, the ONH ₄ group content was 99%, and the OH group / ONH ₄ group content ratio was 1:99.

Production Example 2
(Synthesis of colloidal silica 2)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 8.5 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of ethylene glycol was mixed and concentrated at 60 ° C. to obtain 500 parts of an ethylene glycol dispersion of colloidal silica.
(Measurement of surface modification group of colloidal silica)
When the content of OH group and ONH ₄ group in the surface modification group of colloidal silica was determined in the same manner as in Production Example 1, they were 10% and 90%, respectively, and the content ratio of OH group and ONH ₄ group was 10: 90.

Production Example 3
(Synthesis of colloidal silica 3)
Commercially available acid colloidal silica (Snowtex-O, manufactured by Nissan Chemical Industries, average particle size of 10 to 20 nm, surface modifying group is OH group) 20% Aqueous dispersion is added to 500 parts of aqueous dispersion to adjust pH to 8.0. Thereafter, 400 parts of ethylene glycol was mixed and concentrated at 60 ° C. to obtain 500 parts of an ethylene glycol dispersion of colloidal silica.
The content of OH groups and ONH ₄ groups in the surface modification group of colloidal silica was determined in the same manner as in Production Example 1 and found to be 20.1% and 79.9%, respectively, and the contents of OH groups and ONH ₄ groups The ratio was 20.1: 79.9.

Production Comparative Example 1
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 1 except that the pH was adjusted to 7.7.
When the contents of OH groups and ₄ ONH ₄ groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 1, they were 30% and 70%, respectively, and the content ratio thereof was 30:70.

Production Comparative Example 2
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 1 except that the pH was adjusted to 7.3.
When the content of OH group and ₄ ONH ₄ group in the surface modification group of colloidal silica was determined in the same manner as in Production Example 1, they were 40% and 60%, respectively, and the content ratio was 40:60.

Production Comparative Example 3
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 1 except that the pH was adjusted to 7.0.
When the contents of OH groups and ₄ ONH ₄ groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 1, they were 50% and 50%, respectively, and the content ratio was 50:50.

Example 1
(Preparation of electrolyte 1)
After mixing 188 parts (1.0 mol) of azelaic acid and 1670 parts of ethylene glycol as a solvent and stirring, 146 parts (2.0 mol) of diethylamine was dropped to obtain an azelaic acid diethylamine ethylene glycol solution, 223 parts of the colloidal silica ethylene glycol dispersion prepared in Production Example 1 was mixed with stirring to obtain an azelaic acid diethylamine ethylene glycol solution containing colloidal silica (colloidal silica content 2%).

Example 2
(Preparation of electrolyte 2)
An electrolyte solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 2.

Example 3
(Preparation of electrolyte 3)
An electrolyte solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 3.

Comparative Example 1
An electrolyte solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Reference Example 2.

Comparative Example 2
An electrolytic solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica of Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica of Production Comparative Example 1.

Comparative Example 3
An electrolytic solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Comparative Example 2.

Comparative Example 4
An electrolyte solution was prepared in the same manner as in Example 1 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Comparative Example 3.

Comparative Example 5
An electrolyte solution was prepared in the same manner as in Example 1, except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Reference Example 1.

Test example 1
About the electrolyte solution obtained in Examples 1-3 and Comparative Examples 1-5, the electrical conductivity and spark voltage after an initial stage and a heat test (after 2000 hours on 105 degreeC conditions) were measured with the following measuring method. The results are shown in Table 1.

(Measurement method of conductivity)
The conductivity (mS / cm) at 30 ° C. of the electrolytic solution for the electrolytic capacitor was measured using an SC meter SC72 manufactured by Yokogawa Electric Corporation.

(Measurement method of spark voltage)
A constant current of 5 mA / cm ² was applied to the electrolytic solution for electrolytic capacitors at 25 ° C., the voltage-time curve was examined, and the voltage at which spark or scintillation was observed at the beginning of the voltage rising curve was determined as the spark voltage (V). did.

From Table 1, the electrolytic solutions of Examples 1 to 3 can suppress gelation due to agglomeration and polymerization of colloidal silica as compared with the electrolytic solutions of Comparative Examples 1 to 5, so that the initial spark voltage is high and the heat resistance test is performed. After that, it was shown that the spark voltage and the conductivity were not lowered and the heat resistance was excellent.

Example 4
(Preparation of electrolyte solution 4)
While mixing 188 parts (1.0 mol) of azelaic acid and 1531 parts of ethylene glycol as a solvent and stirring, 394 parts (2.0 mol) of 30% trimethylamine aqueous solution was added dropwise and reacted, and then concentrated at 80 ° C. Thus, an azelaic acid trimethylamine ethylene glycol solution was obtained. Thereafter, 204 parts of the colloidal silica ethylene glycol dispersion prepared in Production Example 1 was mixed with stirring to obtain an azelaic acid trimethylamine ethylene glycol solution (colloidal silica content 2%) to which colloidal silica was added.

Example 5
(Preparation of electrolyte 5)
An electrolyte solution was prepared in the same manner as in Example 4 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 2.

Example 6
(Preparation of electrolyte 6)
An electrolyte solution was prepared in the same manner as in Example 4 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 3.

Example 7
(Preparation of electrolyte 7)
While mixing and stirring 188 parts (1.0 mol) of azelaic acid and 1111 parts of ethylene glycol as a solvent, 34.1 parts (2.0 mol) of ammonia was added dropwise to obtain an ammonium azelate ethylene glycol solution. Thereafter, 148 parts of an ethylene glycol dispersion of colloidal silica prepared in Production Example 1 was mixed with stirring to obtain an ammonium azelate ethylene glycol solution to which colloidal silica was added (content of colloidal silica 2%).

Example 8
(Preparation of electrolyte 8)
An electrolyte solution was prepared in the same manner as in Example 7 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 2.

Example 9
(Preparation of electrolyte solution 9)
An electrolyte solution was prepared in the same manner as in Example 7 except that the ethylene glycol dispersion of colloidal silica in Production Example 1 was replaced with the ethylene glycol dispersion of colloidal silica in Production Example 3.

Example 10
(Preparation of electrolyte 10)
While mixing 230 parts of 1,6-decanedicarboxylic acid (1.0 mol) and 1322 parts of ethylene glycol as a solvent and stirring, 34.1 parts (2.0 mol) of ammonia was added dropwise, and 1,6- After obtaining a solution of ammonium decanedicarboxylate ethylene glycol, 176 parts of an ethylene glycol dispersion of colloidal silica prepared in Production Example 2 were mixed with stirring, and ammonium 1,6-decanedicarboxylate added with colloidal silica was added. A solution (content of colloidal silica 2%) was obtained.

Example 11
(Preparation of electrolyte solution 11)
After placing 61.8 parts (1.0 mol) of boric acid, 276 parts (2.0 mol) of salicylic acid and 85.2 parts (1.0 mol) of N-methylpyrrolidine in 1000 parts of water, the mixture was reacted at 40 ° C. for 1 hour. The solution was concentrated under reduced pressure to obtain crude crystals of borodisalicylic acid-N-methylpyrrolidine, and the crude crystals were purified using methyl ethyl ketone and then dried.
198 parts (0.9 mol) of the obtained borodisalicylic acid-N-methylpyrrolidine and 990 parts of ethylene glycol as a solvent were mixed to obtain a borodisalicylic acid-N-methylpyrrolidine ethylene glycol solution. 132 parts of the prepared ethylene glycol dispersion of colloidal silica was mixed with stirring to obtain a borodisalicylic acid-N-methylpyrrolidine ethylene glycol solution to which colloidal silica was added (content of colloidal silica 2%).

Test example 2
For the electrolytic solutions obtained in Examples 4 to 11 in the same manner as in Test Example 1, the electrical conductivity and spark voltage after the initial stage and after the heat resistance test (after 2000 hours at 105 ° C.) were measured. The results are shown in Table 1.

  From Table 2, since electrolyte solution of Examples 4-11 can suppress gelatinization by aggregation and superposition | polymerization of colloidal silica, all have high initial spark voltage, maintain a high spark voltage after a heat test, and spark. It was excellent in heat resistance in terms of voltage and conductivity.

Reference example 3
(Preparation of γ-butyrolactone dispersion of acid-type colloidal silica)
Commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10 to 20 nm, surface modifying group is OH group) 20 parts aqueous dispersion 500 parts and 400 gamma-butyrolactone are mixed. The mixture was concentrated at 60 ° C. to obtain 500 parts of a γ-butyrolactone dispersion of colloidal silica.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of γ-butyrolactone dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption spectrometer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of content ratio of surface modification group of colloidal silica)
5 μl of γ-butyrolactone dispersion of colloidal silica was sampled and coated on a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby preparing a uniform sample thin film. . The thin film of the obtained sample was measured by the infrared absorption spectrum method, and it was confirmed that the peak at a wavelength of 3700 cm ⁻¹ was attributed to an OH group and there was no ONH ₄ group peak. Further, the peak area (A ₀ ′) of the peak attributed to the OH group was measured.

Reference example 4
(Synthesis of ammonia stable colloidal silica and preparation of γ-butyrolactone dispersion)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 9.0 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of γ-butyrolactone was mixed and concentrated at 60 ° C. to obtain 500 parts of a γ-butyrolactone dispersion of colloidal silica.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of γ-butyrolactone dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption spectrometer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of surface modification group of colloidal silica)
5 μl of γ-butyrolactone dispersion of colloidal silica was sampled and coated on a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby preparing a uniform sample thin film. . The thin film of the obtained sample was measured by an infrared absorption spectrum method, and a peak at a wavelength of 3030 cm ⁻¹ 3330 cm ⁻¹ was assigned to ₄ ONH groups, and it was confirmed that there was no OH group peak. Regarding peaks attributed with ONH ₄ group was determined and the peak area _{(B 0} ').

Production Example 4
(Synthesis of colloidal silica 4)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 8.9 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of γ-butyrolactone was mixed and concentrated at 60 ° C. to obtain 500 parts of a γ-butyrolactone dispersion of colloidal silica.
(Measurement of surface modification group content of colloidal silica)
After collecting 10 g of γ-butyrolactone dispersion of colloidal silica in a 100 ml volumetric flask, a sample diluted with ion-exchanged water up to the marked line was measured for sodium content with an atomic absorption spectrometer. From the peak at a wavelength of 589 nm, the sodium content was 10 ppm or less, and it was confirmed that the colloidal silica surface modifying group had no Na group. Therefore, it was confirmed that all the colloidal silica surface modifying groups were OH groups or ONH ₄ groups.
(Measurement of surface modification group of colloidal silica)
5 μl of γ-butyrolactone dispersion of colloidal silica was sampled and coated on a calcium fluoride tablet, and then allowed to stand for 48 hours under a vacuum of 5 Torr to completely evaporate the solvent, thereby preparing a uniform sample thin film. . Thin film of the obtained sample was subjected to measurement by infrared absorption spectroscopy, attributing peak wavelengths 3700 cm ^-1 and OH groups, and the peak wavelength ^{3030cm -1 ~3330cm} -1 attributed with ONH ₄ group. The peak area (A ′) of the peak attributed to the OH group and the peak area (B ′) of the peak attributed to the ONH ₄ group are obtained, and the content of the OH group or ONH ₄ group in the surface modification group is calculated by the following formula. Calculated.
OH group content (%) = A ′ / A ₀ ′ × 100
ONH ₄ group content (%) = B ′ / B ₀ ′ × 100
As a result, the OH group content was 1%, the ONH ₄ group content was 99%, and the OH group / ONH ₄ group content ratio was 1:99.

Production Example 5
(Synthesis of colloidal silica 5)
Ammonia is added to 500 parts of a 20% aqueous dispersion adjusted to pH 8.5 by commercially available acid-type colloidal silica (Snowtex-O, manufactured by Nissan Chemical Co., Ltd., average particle size 10-20 nm, surface modifying group is OH group). Thereafter, 400 parts of γ-butyrolactone was mixed and concentrated at 60 ° C. to obtain 500 parts of a γ-butyrolactone dispersion of colloidal silica.
When the contents of OH groups and ₄ ONH groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 4, they were 10% and 90%, respectively, and the content ratio was 10:90.

Production Example 6
(Synthesis of colloidal silica 6)
Commercially available acid colloidal silica (Snowtex-O, manufactured by Nissan Chemical Industries, average particle size of 10 to 20 nm, surface modifying group is OH group) 20% Aqueous dispersion is added to 500 parts of aqueous dispersion to adjust pH to 8.0. Thereafter, 400 parts of γ-butyrolactone was mixed and concentrated at 60 ° C. to obtain 500 parts of a γ-butyrolactone dispersion of colloidal silica.
When the contents of OH groups and ₄ ONH ₄ groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 4, they were 20.1% and 79.9%, respectively, and their content ratio was 20.1%. : 79.9.

Production Comparative Example 4
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 4 except that the pH was adjusted to 7.7.
The contents of OH groups and ONH ₄ groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 4 and found to be 30% and 70%, respectively, and the content ratio was 30:70.

Production Comparative Example 5
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 4 except that the pH was adjusted to 7.3.
When the contents of OH groups and ₄ ONH ₄ groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 4, they were 40% and 60%, respectively, and the content ratio was 40:60.

Production Comparative Example 6
An ethylene glycol dispersion of colloidal silica was obtained in the same manner as in Production Example 4 except that the pH was adjusted to 7.0.
When the contents of OH groups and ₄ ONH groups in the surface modification group of colloidal silica were determined in the same manner as in Production Example 4, they were 50% and 50%, respectively, and the content ratio was 50:50.

Example 12
(Preparation of electrolyte solution 12)
While mixing 166 parts (1.0 mol) of phthalic acid and 838 parts of γ-butyrolactone as a solvent and stirring, 73.1 parts (1.0 mol) of dimethylethylamine was added dropwise, and dimethylethylamine phthalate γ-butyrolactone was added. After obtaining the solution, 120 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 4 were mixed with stirring, and dimethylethylamine phthalate γ-butyrolactone solution containing colloidal silica (content of colloidal silica 2 %).

Example 13
(Preparation of Electrolytic Solution 13)
An electrolyte solution was prepared in the same manner as in Example 12 except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Production Example 5.

Example 14
(Preparation of Electrolytic Solution 14)
An electrolyte solution was prepared in the same manner as in Example 12 except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Example 6.

Comparative Example 6
An electrolyte solution was prepared in the same manner as in Example 12, except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Reference Example 4.

Comparative Example 7
An electrolytic solution was prepared in the same manner as in Example 12 except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Comparative Example 4.

Comparative Example 8
An electrolyte solution was prepared in the same manner as in Example 12, except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Comparative Example 5.

Comparative Example 9
An electrolyte solution was prepared in the same manner as in Example 12, except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Comparative Example 6.

Comparative Example 10
An electrolyte solution was prepared in the same manner as in Example 12 except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Reference Example 3.

Test example 3
In the same manner as in Test Example 1, the electrolytes obtained in Examples 12 to 14 and Comparative Examples 6 to 10 were measured for electrical conductivity and spark voltage after the initial and heat resistance tests (after 2000 hours at 105 ° C.). The results are shown in Table 3.

  From Table 3, since the electrolyte solution of Examples 12-14 can suppress gelatinization by aggregation and superposition | polymerization of colloidal silica compared with the electrolyte solution of Comparative Examples 6-10, an initial spark voltage is high, and also after a heat test. The spark voltage and conductivity were not decreased, and the heat resistance was excellent.

Example 15
(Preparation 15 of electrolyte solution)
After mixing 116 parts of maleic acid (1.0 mol) and 859 parts of γ-butyrolactone as a solvent and stirring, 736 parts (1.0 mol) of a 20% tetraethylammonium hydroxide aqueous solution was dropped and reacted. The pressure is reduced at 80 ° C. to obtain a tetraethylammonium hydrogen maleate γ-butyrolactone solution. Thereafter, 123 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 4 was mixed with stirring, and a tetraethylammonium hydrogen maleate γ-butyrolactone solution (colloidal silica content 2%) to which colloidal silica was added was added. Obtained.

Example 16
(Preparation of Electrolytic Solution 16)
An electrolyte solution was prepared in the same manner as in Example 15 except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Example 5.

Example 17
(Electrolytic Solution Preparation 17)
An electrolytic solution was prepared in the same manner as in Example 15 except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Production Example 6.

Example 18
(Preparation of Electrolytic Solution 18)
While mixing and stirring 166 parts (1.0 mol) of phthalic acid and 838 parts of γ-butyrolactone as a solvent, 73.1 parts (1.0 mol) of diethylamine was added dropwise to prepare a diethylamine phthalate γ-butyrolactone solution. Then, 120 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 4 was mixed with stirring, and a diethylamine phthalate γ-butyrolactone solution (colloidal silica content 2%) to which colloidal silica was added was obtained. Obtained.

Example 19
(Preparation of electrolyte 19)
An electrolyte solution was prepared in the same manner as in Example 18 except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Production Example 5.

Example 20
(Preparation of electrolyte 20)
An electrolytic solution was prepared in the same manner as in Example 18 except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Production Example 6.

Example 21
(Preparation of Electrolytic Solution 21)
While mixing and stirring 166 parts (1.0 mol) of phthalic acid and 1012 parts of γ-butyrolactone as a solvent, 705 parts (1.0 mol) of a 20% tetramethylimidazolium hydroxide aqueous solution was dropped and reacted. Thereafter, it is concentrated at 80 ° C. to obtain a tetramethylimidazolium phthalate γ-butyrolactone solution. Thereafter, 145 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 4 were mixed with stirring, and tetramethylimidazolium phthalate γ-butyrolactone solution containing colloidal silica (content of colloidal silica 2%) Got.

Example 22
(Preparation of Electrolytic Solution 22)
An electrolytic solution was prepared in the same manner as in Example 21 except that the colloidal silica γ-butyrolactone dispersion in Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion in Production Example 5.

Example 23
(Preparation of Electrolytic Solution 23)
An electrolyte solution was prepared in the same manner as in Example 21, except that the colloidal silica γ-butyrolactone dispersion of Production Example 4 was replaced with the colloidal silica γ-butyrolactone dispersion of Production Example 6.

Example 24
(Preparation of electrolyte solution 24)
While mixing 116 parts (1.0 mol) of maleic acid and 843 parts of γ-butyrolactone as a solvent and stirring, 716 parts (1.0 mol) of a 20% aqueous solution of spiro- (1,1 ′)-bipyrrolidinium hydroxide was added. After the reaction by dropping, it is concentrated at 80 ° C. to obtain a spiro- (1,1 ′)-bipyrrolidinium maleate γ-butyrolactone solution. Thereafter, 121 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 5 was mixed with stirring, and a spiro- (1,1 ′)-bipyrrolidinium γ-butyrolactone maleate solution to which colloidal silica was added (colloidal silica). Content 2%).

Example 25
(Preparation of Electrolytic Solution 25)
While mixing 166 parts (1.0 mol) of phthalic acid and 967 parts of γ-butyrolactone as a solvent and stirring, 641 parts (1.0 mol) of 20% 1-ethyl-3-methylimidazolinium hydroxide aqueous solution was added. After making it react by dripping, it concentrates at 80 degreeC and obtains the 1-ethyl-3-methylimidazolinium γ-butyrolactone solution of phthalate. Thereafter, 138 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 5 was mixed with stirring, and 1-ethyl-3-methylimidazolinium phthalate γ-butyrolactone solution containing colloidal silica (colloidal silica) was added. Content 2%).

Example 26
(Preparation of Electrolyte 26)
While mixing 166 parts (1.0 mol) of phthalic acid and 967 parts of γ-butyrolactone as a solvent and stirring, 641 parts (1.0 mol) of 20% aqueous 1-methyl-2-ethylpyrazolium hydroxide solution was added. After making it react by dripping, it concentrates at 80 degreeC and the phthalate 1-methyl-2-ethyl pyrazolium gamma-butyrolactone solution is obtained. Thereafter, 138 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 5 were mixed with stirring, and 1-methyl-2-ethylpyrazolium phthalate γ-butyrolactone solution containing colloidal silica (colloidal silica) was added. Content 2%).

Example 27
(Preparation of electrolyte solution 27)
While mixing and stirring 166 parts (1.0 mol) of phthalic acid and 1054 parts of γ-butyrolactone as a solvent, 765 parts (1.0 mol) of a 20% aqueous solution of N-butylpyridinium hydroxide was added dropwise to react. Then, it concentrates at 80 degreeC and N-butyl pyridinium phthalate (gamma) -butyrolactone solution is obtained. Thereafter, 151 parts of the colloidal silica γ-butyrolactone dispersion prepared in Production Example 5 were mixed with stirring, and the N-butylpyridinium phthalate γ-butyrolactone solution to which colloidal silica was added (colloidal silica content 2%). Got.

Test example 4
For the electrolyte solutions obtained in Examples 15 to 27 in the same manner as in Test Example 1, the electrical conductivity and spark voltage after the initial stage and after the heat resistance test (after 2000 hours at 105 ° C.) were measured. The results are shown in Table 4.

  As shown in Table 4, since the electrolytic solutions obtained in Examples 15 to 27 can suppress gelation due to aggregation and polymerization of colloidal silica, all have high initial spark voltage, and spark voltage and conductivity after the heat resistance test. The value of the degree hardly decreased, and the heat resistance was excellent.

Example 28
(Preparation of Electrolytic Solution 28)
While mixing and stirring 188 parts (1.0 mol) of azelaic acid and 1670 parts of ethylene glycol as a solvent, 146 parts (2.0 mol) of diethylamine was added dropwise to obtain a diethylamine ethylene glycol solution of azelaic acid. After the addition of 30 ppm, 223 parts of the colloidal silica ethylene glycol dispersion prepared in Production Example 2 was mixed with stirring to obtain an azelaic acid diethylamine ethylene glycol solution (colloidal silica content 2%) to which colloidal silica was added. It was.

Example 29
(Preparation of electrolyte solution 29)
When preparing the electrolytic solution, an electrolytic solution was obtained in the same manner as in Example 28 except that the amount of sulfuric acid added was changed to 100 ppm.

Test Example 5
For the electrolytic solutions obtained in Examples 28 to 29 in the same manner as in Test Example 1, the electrical conductivity and spark voltage after the initial stage and after the heat resistance test (after 2000 hours at 105 ° C.) were measured. The results are shown in Table 5.

  From Table 5, it was shown that the spark voltage was further improved by adding sulfate ions.

  Since the electrolytic solution of the present invention has a high spark voltage and is excellent in heat resistance in terms of spark voltage and conductivity, it is extremely useful as an electrolytic solution for electrolytic capacitors.

Claims (11)

An electrolyte salt containing a nitrogen-containing cation, colloidal silica, and an organic solvent are contained, and the colloidal silica contains OH groups and ONH ₄ groups as surface modification groups in a content ratio of 1:25 to 99:75. Electrolytic solution for electrolytic capacitors. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the OH group content in the surface modification group of the colloidal silica is 1 to 25% and the ONH ₄ group content is 75 to 99%.   The electrolytic solution for electrolytic capacitors according to claim 1 or 2, wherein the content of colloidal silica is 0.1 to 20% by mass.   The electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 3, wherein the colloidal silica has a particle size of 1 to 50 nm.   The electrolytic solution for electrolytic capacitors according to any one of claims 1 to 4, further comprising 1 to 100 ppm of sulfate ions. The electrolyte salt containing a nitrogen-containing cation is one or more selected from the group consisting of compounds represented by the following general formulas (1) to (5). Electrolytic solution for electrolytic capacitors.

(In the formulas (1) to (5), the groups R ^{1 to} R ²⁵ are each the same or different hydrogen, a C 1-18 alkyl group, a C 1-18 alkoxy group, or a hydroxyl group, Adjacent groups in R ^{1 to} R ²⁵ may be linked to form an alkylene group having 2 to 6 carbon atoms.X ⁻ is a carboxylate anion or a boron compound anion.)
In the general formulas (1) to (5), X ⁻ is selected from the group consisting of a phthalate anion, a maleate anion, a salicylate anion, a benzoate anion, an adipate anion, a borodisalicylate anion, and a borodiglycolate anion. 7. The electrolytic solution for an electrolytic capacitor according to claim 6, which contains an electrolyte salt which is an anion and is for low to medium pressure using γ-butyrolactone as a main solvent. In the general formulas (1) to (5), X ⁻ represents an azelate anion, a 1,6-decanedicarboxylic acid anion, a 3-tert-butyladipate anion, a borate anion, a borodisalicylate anion, and a borodiglycolic acid The electrolytic solution for an electrolytic capacitor according to claim 6, which contains an electrolyte salt which is an anion selected from the group consisting of anions, and is for high pressure using ethylene glycol as a main solvent.   The electrolytic capacitor formed using the electrolyte solution for electrolytic capacitors in any one of Claims 1-8. Adding colloidal silica containing OH groups and ONH ₄ groups as surface modification groups in a content ratio of 1:25 to 99:75 to an electrolytic solution for electrolytic capacitors containing a nitrogen-containing cation and an organic solvent. A method for improving the spark voltage of an electrolytic solution for electrolytic capacitors. Adding colloidal silica containing OH groups and ONH ₄ groups as surface modification groups in a content ratio of 1:25 to 99:75 to an electrolytic solution for electrolytic capacitors containing a nitrogen-containing cation and an organic solvent. A method for improving the heat resistance of an electrolytic solution for electrolytic capacitors.