JP2015026764A - 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 can maintain electric conductivity and the spark voltage under a high temperature condition for a long period of time and also to provide the electrolytic capacitor using the same.SOLUTION: Disclosed is an electrolyte for an electrolytic capacitor which is characterized in containing at least polyether polyol, colloidal silica, electrolyte salt and an organic solvent, and the electrolytic capacitor using the same is also disclosed. Charge balance of colloidal silica in the electrolyte can be prevented from being collapsed by containing polyether polyol therein.

Description

  The present invention relates to an electrolytic solution for an electrolytic capacitor that has a high spark voltage and can maintain conductivity and spark voltage at a high temperature of 105 ° C. for a long period of time, and an electrolytic capacitor using the electrolytic solution.

  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.

  Due to the increasing demand for safety, electrolytic capacitors with a high spark voltage are required in order to prevent short-circuiting and ignition even under severe conditions where a voltage exceeding the rated voltage is applied to the electrolytic capacitor. ing.

  In addition, there is a problem that the conductivity and the spark voltage are greatly reduced when the electrolytic solution used is gelled or deteriorated, and the high performance that can maintain the conductivity and the spark voltage for a long time even at a high temperature such as 105 ° C. There is a need for an electrolytic solution for electrolytic capacitors having the following. It is known that an electrolytic capacitor having excellent equivalent series resistance (hereinafter abbreviated as “ESR”) and withstand voltage can be manufactured by using such an electrolytic solution for electrolytic capacitors.

  In the electrolytic solution for electrolytic capacitors, as additives that have a high spark voltage and can maintain the conductivity and the spark voltage for a long period of time, colloidal silica, silicon dioxide (see Patent Document 1), phosphate ester (Patent Document) 2), porous polyimide fine particles (see Patent Document 3), and the like. However, even with these additives, the spark voltage is still insufficient, and it was impossible to maintain the conductivity and spark voltage for a long time at a high temperature of 105 ° C.

  Patent Document 4 discloses an electrolytic solution for electrolytic capacitors containing a dialkyl phosphate and colloidal silica. By including a dialkyl phosphate ester and colloidal silica in combination, a high spark voltage is obtained, and it is possible to maintain a certain degree of conductivity and spark voltage at a high temperature of 105 ° C. No voltage was obtained, and the ability to maintain conductivity and spark voltage under high temperature conditions was still insufficient.

  As described above, there is a need for an electrolytic solution for an electrolytic capacitor that has a high spark voltage and can maintain conductivity and spark voltage for a long period of time at a high temperature of 105 ° C. and an electrolytic capacitor using the electrolytic solution.

JP 05-6839 A JP 2001-155968 A JP 2009-283581 A Japanese Patent Laid-Open No. 06-196366

  An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor that has a high spark voltage and can maintain a conductivity and a spark voltage for a long time at a high temperature of 105 ° C., and an electrolytic capacitor using the electrolytic solution. is there.

  The present invention provides an electrolytic solution for an electrolytic capacitor, and an electrolytic capacitor using the same, comprising at least a polyether polyol, colloidal silica, an electrolyte salt, and an organic solvent.

  That is, the present invention is as follows.

  A first invention is an electrolytic solution for an electrolytic capacitor characterized by containing at least a polyether polyol, colloidal silica, an electrolyte salt, and an organic solvent.

  The second invention is the electrolytic solution for an electrolytic capacitor according to the first invention, wherein the mass ratio of the polyether polyol to the colloidal silica is 0.01 to 10.

  3rd invention is the electrolyte solution for electrolytic capacitors as described in 1st or 2nd invention, wherein the average molecular weight of polyether polyol is 500-10000.

  In the fourth invention, the polyether polyol is selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, polyoxypropylene triol, polytetramethylene ether glycol, polyoxyethylene glycol-polyoxypropylene glycol block copolymer. The electrolytic solution for electrolytic capacitors according to any one of the first to third inventions, wherein the electrolytic solution is at least one kind.

  5th invention is 0.01-20 mass% in content of the polyether polyol in the electrolyte solution for electrolytic capacitors, It is described in any one of the 1st to 4th invention characterized by the above-mentioned. This is an electrolytic solution for electrolytic capacitors.

  According to a sixth invention, in any one of the first to fifth inventions, the electrolyte salt is any one of the compounds represented by the following general formulas (1) to (5). This is an electrolytic solution for electrolytic capacitors.

（式（１）〜（５）中、基Ｒ^１〜Ｒ^２５は、それぞれ同一でも異なっても良い水素、炭素数１〜１８のアルキル基、炭素数１〜１８のアルコキシ基又は水酸基であり、Ｒ^１〜Ｒ^２５のうち隣接する基同士は連結して炭素数２〜６のアルキレン基を形成しても良い。Ｘ⁻は、カルボン酸アニオン又はホウ素化合物アニオンである。）

(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.)

  A seventh invention is an electrolytic capacitor characterized by using the electrolytic solution for an electrolytic capacitor described in any one of the first to sixth inventions.

  According to the present invention, it is possible to obtain an electrolytic solution for an electrolytic capacitor having a high spark voltage and capable of maintaining the electrical conductivity and the spark voltage at a high temperature of 105 ° C. for a long period of time and an electrolytic capacitor using the electrolytic solution. .

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

  As a result of intensive studies, the present inventors have found that an electrolytic solution for an electrolytic capacitor containing at least a polyether polyol, colloidal silica, an electrolyte salt, and an organic solvent, and an electrolytic capacitor using the same can solve the above problems. And found the present invention.

<Polyether polyol>
Polyether polyol is a polymer having an ether group and a hydroxyl group. Specifically, glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxypropylene triol, polytetramethylene ether glycol, polyoxyethylene glycol- Examples include polyoxypropylene glycol block copolymers. By containing these compounds, the spark voltage can be improved and the dispersibility of colloidal silica can be improved, so that gelation can be prevented. It is known that the electrolytic solution for an electrolytic capacitor is gelled, whereby the electrical conductivity and the spark voltage are reduced. Therefore, by preventing gelation of the electrolytic solution for electrolytic capacitors, the electrical conductivity and the spark voltage can be maintained for a long time.

  Polyether polyols can be used alone or in combination of two or more. Among these, a polyoxyethylene glycol-polyoxypropylene glycol block copolymer is preferred because it prevents gelation of the electrolytic solution for electrolytic capacitors.

  Although what kind of thing may be sufficient as the average molecular weight of polyether polyol, 300-20000 are mentioned preferably, 500-10000 are more preferable, 1000-5000 are especially preferable. By using the polyether polyol having the average molecular weight, the colloidal silica in the electrolytic solution can be further dispersed, and thus gelation of the electrolytic solution can be prevented.

<Electrolyte salt>
As the electrolyte salt used in the present invention, any electrolyte salt usually used in an electrolytic capacitor can be used. Among the electrolyte salts, it is particularly preferable to use any of the compounds represented by the following general formulas (1) to (5) as the electrolyte salt.

In the general formulas (1) to (5), the groups R ^{1 to} R ²⁵ are the same or different hydrogen, a C 1-18 alkyl group, a C 1-18 alkoxy group, or a hydroxyl group, Adjacent groups among 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.

  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, ethylmalo Acid anion, propylmalonate anion, butylmalonate anion, pentylmalonate anion, hexylmalonate anion, dimethylmalonate anion, diethylmalonate anion, methylpropylmalonate anion, methylbutylmalonate anion, ethylpropylmalonate anion , Dipropylmalonate 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, 3 Methyl adipate anion, 1,6-decanedicarboxylic acid anion, 5,6-decanedicarboxylic acid anion, formate anion, acetate anion, propionate anion, butyrate anion, isobutyrate anion, valerate anion, caproate anion, enanthate Anion, caprylate anion, pelargonate anion, laurate anion, myristic acid anion, stearate anion, behenate anion, undecanoate anion, borate anion, borodiglycolate anion, borodisoxalate anion, borodisalicylate anion, boro Saturated carboxylate and maleate anions such as diazelineate anion, borodilactic acid anion, itaconic acid anion, tartrate anion, glycolate anion, lactate anion, pyruvate anion, Examples thereof include an aliphatic carboxylic acid anion containing an unsaturated carboxylic acid such as a fumarate anion, an acrylate anion, a methacrylate anion, and an oleate 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, sebacic acid anion, azelaic acid anion, 1,6-decane from the viewpoint of improved spark voltage and thermal stability Preferable examples include dicarboxylic acid anions and 3-tert-butyladipate anions.

  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 for high-voltage electrolytic capacitors, sebacic acid anion, azelaic acid anion, 1,6-decanedicarboxylic acid anion, 3-tert-butyladipate anion, borate anion, borodisalicylate anion, borodiglycol An acid anion or the like is preferably 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), any one of the compounds represented by the general formulas (1) to (3) is stable over a long period of time and obtains a high spark voltage. It is preferably used because of its excellent heat resistance. Specifically, electrolyte salts used in low and medium pressure electrolytic capacitors include dimethylethylamine maleate, dimethylethylamine phthalate, tetraethylammonium maleate, tetraethylammonium phthalate, trimethylamine maleate, trimethylamine phthalate, triethylamine maleate, phthalate Triethylamine acid, diethylamine maleate, diethylamine phthalate, spiro- (1,1 ′)-bipyrrolidinium maleate, spiro- (1,1 ′)-bipyrrolidinium phthalate, 1-ethyl-3-methylimidazolium maleate, phthalate 1-ethyl-3-methylimidazolium acid, 1-ethyl-3-methylimidazolinium maleate, 1-ethyl-3-methylimidazolinium phthalate, tetramethylimidazole phthalate Potassium, phthalic acid tetramethyl imidazolinium phthalate tetraethyl imidazolium, phthalic acid tetraethyl imidazolium and the like. On the other hand, electrolyte salts used for high-voltage electrolytic capacitors include dimethylamine sebacate, diethylamine sebacate, trimethylamine sebacate, triethylamine sebacate, ammonium sebacate, dimethylamine azelate, diethylamine azelate, trimethylamine azelate, triethylamine azelate , Ammonium azelate, ammonium 1,6-decanedicarboxylate, dimethylamine 1,6-decanedicarboxylic acid, diethylamine 1,6-decanedicarboxylic acid, trimethylamine 1,6-decanedicarboxylic acid, triethylamine 1,6-decanedicarboxylic acid , N-methylpyrrolidine borodisalicylate is preferably used.

The content of the electrolyte salt in the electrolytic solution for electrolytic capacitors is preferably 1.0 to 60% by mass, more preferably 5.0 to 50% by mass, and particularly preferably 10 to 40% by mass.
When the amount is less than 1.0% by mass, there is a defect that sufficient electric characteristics cannot be obtained. When the amount exceeds 60% by mass, the specific resistance increases.

<Colloidal silica>
Colloidal silica is a colloid of SiO ₂ or its hydrate, and has a particle size of 1 to 300 nm and no fixed structure. It can be obtained by dialysis after dilute hydrochloric acid is allowed to act on the silicate. As the particle size becomes smaller, gelation tends to proceed, but as the particle size becomes larger, gelation becomes difficult. As for the particle size of the colloidal silica used for this invention, 10-50 nm is mentioned preferably, More preferably, 10-30 nm is mentioned preferably. By using colloidal silica having such a particle size, it is difficult to form a gel, and a stable dispersed state can be maintained even when an electrolytic capacitor is used.

  Colloidal silica hardly dissolves in water or an organic solvent, and can be used in a state where it is added to an electrolytic solution as a colloidal solution generally dispersed in an appropriate dispersion solvent and dispersed when an electrolytic capacitor is used.

The colloidal silica used in the present invention may be sodium stable colloidal silica, acidic colloidal silica, or ammonia stable colloidal silica.
The sodium stable colloidal silica has an ONa group on the surface of the colloidal silica. Acidic colloidal silica is colloidal silica in which the surface of the colloidal silica is an OH group from which Na has been removed. Ammonia-stable colloidal silica is stable by removing ammonia to form an OH group and then containing ammonia. Colloidal silica.
Among these, acidic colloidal silica or ammonia-stable colloidal silica having a low sodium ion content is preferably exemplified.

  The content of colloidal silica in the electrolytic solution for electrolytic capacitors is 0.1 to 20% by mass, more preferably 0.2 to 15% by mass, and particularly preferably 0.3 to 10% by mass. When the amount is less than 0.1% by mass, the effect of improving the electrical characteristics of the electrolytic capacitor is small.

  The average particle diameter of colloidal silica may be any, and is preferably 1 to 100 nm, more preferably 10 to 50 nm, and particularly preferably 10 to 30 nm. By setting the average particle size, an electrolytic solution for electrolytic capacitors having excellent 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.

<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. Further, the smaller the amount of water contained in the electrolytic solution for electrolytic capacitors, the better.
When used for a high voltage electrolytic capacitor, ethylene glycol is preferred. The amount of water contained in the electrolytic solution for electrolytic capacitors is not particularly limited, but is preferably 0.1 to 30% by mass, and more preferably 0.5 to 20% by mass. By setting the amount of water, good electrical conductivity can be obtained.

  The content of the polyether polyol in the electrolytic solution for an electrolytic capacitor is preferably 0.01 to 20% by mass, more preferably 0.05 to 15% by mass, and particularly preferably 0.1 to 10% by mass. It is done. If it is less than 0.01% by mass, the effect of preventing the aggregation of colloidal silica cannot be sufficiently obtained, and if it exceeds 20% by mass, the electric conductivity in the electrolytic solution may be slightly lowered.

  The content ratio (mass ratio) of colloidal silica and polyether polyol in the electrolytic solution for electrolytic capacitors may be any mass ratio, but it is preferable to contain 0.01 to 10 polyether polyol with respect to colloidal silica 1. More preferably, 0.05 to 5.0 is included, and 0.1 to 2.0 is particularly preferable. By making it into this range, gelation of the electrolytic solution for electrolytic capacitors can be prevented, and the initial conductivity and spark voltage can be maintained for a long time even under high temperature conditions.

  As the performance required for the electrolytic solution for medium and low pressure electrolytic capacitors, the electrical conductivity after a heat resistance test (105 ° C., 2000 hours) is preferably 7.0 mS / cm or more, more preferably 7.3 mS / cm or more. 7.7 mS / cm or more is even more preferable, and 8 mS / cm or more is particularly preferable. The spark voltage after the heat resistance test (105 ° C., 2000 hours) is preferably 200 V or more, more preferably 205 V, even more preferably 210 V or more, and particularly preferably 215 V or more.

  As the performance required for the electrolytic solution for electrolytic capacitors for high voltage, the conductivity after a heat resistance test (105 ° C., 2000 hours) is preferably 2.0 mS / cm or more, more preferably 2.3 mS / cm or more. Preferably, 2.7 mS / cm or more is even more preferable, and 3 mS / cm or more is particularly preferable. The spark voltage after the heat resistance test (105 ° C., 2000 hours) is preferably 550 V or more, more preferably 555 V or more, even more preferably 560 V or more, and particularly preferably 565 V or more.

  By including polyether polyol in the electrolytic solution for electrolytic capacitors, it is possible to prevent gelation caused by colloidal silica during heating, storage and use, and maintain conductivity and spark voltage over a long period of time. Can do.

<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.

  The addition amount is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5.0% by mass. If it is less than 0.1% by mass, there is a drawback that a sufficient spark voltage cannot be obtained, and if it exceeds 10% by mass, there is a disadvantage that the conductivity is lowered.

<Electrolytic capacitor>
The electrolytic capacitor of the present invention is an electrolytic capacitor comprising the above-described electrolytic solution for electrolytic capacitors.
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 for electrolytic capacitor therein.

  In general, an electrolytic capacitor using an electrolytic solution for an electrolytic capacitor containing an electrolyte salt and colloidal silica is excellent in initial withstand voltage, but has a drawback that electric characteristics such as withstand voltage and ESR are lowered during use. there were. The cause of the deterioration of their electrical characteristics is that the charge balance of the colloidal silica in the electrolytic solution is lost during use, and the colloidal silica is gelled by agglomeration or / and polymerization, so that the electric conductivity and sparks of the electrolytic solution for electrolytic capacitors are reduced. By applying voltage, characteristics such as withstand voltage and ESR of the electrolytic capacitor are greatly reduced.

  By using the electrolytic solution for an electrolytic capacitor containing the polyether polyol used in the present invention, it is possible to prevent the charge balance of colloidal silica from being lost, and it is difficult to cause aggregation, thereby preventing gelation. Can do. As a result, it is possible to obtain an electrolytic capacitor that has excellent initial withstand voltage and has little change with time in ESR and withstand voltage even at high temperatures.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited at all by the Example. In the examples, “part” represents “part by mass”, and “%” represents “% by mass”.

Example 1
While mixing 166 parts of phthalic acid and 530 parts of γ-butyrolactone as a solvent and stirring, 73.1 parts of N, N-dimethylethylamine was dropped to obtain a dimethylethylamine phthalate solution, then colloidal silica (Nissan Chemical Industries, Snowtex N-40, aqueous dispersion, solid content 40%, average particle size 20-30 nm, pH 9.0-10) 40.0 parts, polyether polyol as polyoxyethylene glycol-polyoxy 0.2 parts of a propylene glycol block copolymer (manufactured by NOF Corporation, Pronon 102, molecular weight 1250) was added, mixed, and concentrated at 80 ° C. to obtain an electrolytic solution for an electrolytic capacitor.

(Examples 2 to 11)
An electrolytic solution for an electrolytic capacitor was obtained in the same manner as in Example 1 except that the content or molecular weight of the polyether polyol was changed so as to correspond to Table 1.

(Examples 12-14, Comparative Examples 1-4)
An electrolytic solution for an electrolytic capacitor was obtained in the same manner as in Example 1 except that the content, molecular weight, and type of additives such as polyether polyol were used so as to correspond to Table 1.

(Example 15)
After mixing 188 parts (1.0 mol) of azelaic acid and 1630 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, Colloidal silica (manufactured by Nissan Chemical Industries, Snowtex N-40, aqueous dispersion, solid content 40%, average particle size 20-30 nm, pH 9.0-10) 100 parts and polyoxyethylene glycol as polyether polyol -0.2 part of polyoxypropylene glycol block copolymer (manufactured by NOF Corporation, Pronon 102, average molecular weight 1250) was added and mixed, and concentrated at 80 ° C to obtain an electrolytic solution for electrolytic capacitors.

(Examples 16 to 25)
An electrolytic solution for an electrolytic capacitor was obtained in the same manner as in Example 15 except that the content of the polyether polyol was changed so as to correspond to Table 2.

(Examples 26 to 28, Comparative Examples 5 to 8)
An electrolytic solution for an electrolytic capacitor was obtained in the same manner as in Example 15 except that the content and type of additives such as polyether polyol were used so as to correspond to Table 2.

  The evaluation methods of the electrical conductivity, spark voltage, and heat resistance of the electrolytic solution for electrolytic capacitors are summarized below.

(Conductivity evaluation method)
The evaluation method of the conductivity is the conductivity (mS / cm) at 30 ° C. of the electrolytic solution for electrolytic capacitors (Examples 1 to 28, Comparative Examples 1 to 8) using SC meter SC72 manufactured by Yokogawa Electric Corporation. It was measured. Moreover, the electrical conductivity after 2000 hours was measured on the conditions of the temperature of 105 degreeC.

(Spark voltage evaluation method)
The spark voltage was evaluated by applying a constant current of 5 mA / cm ² at 25 ° C. to the electrolytic solution for electrolytic capacitors (Examples 1 to 28, Comparative Examples 1 to 8) and examining the voltage-time curve. The spark voltage (V) was the voltage at which spark or scintillation was observed at the beginning of the voltage rise curve. Further, the spark voltage after 2000 hours was measured under a temperature of 105 ° C.

  Tables 1 and 2 show the electrical conductivity (mS / cm) and spark voltage (V) of the electrolytic solution for electrolytic capacitors, and the measurement results of their heat resistance tests.

Details of the additives used in the table are as follows. Moreover, the mass ratio in a table | surface represents the mass ratio of the additive with respect to colloidal silica when colloidal silica is set to 1.
<Additives>
Polyoxyethylene glycol-polyoxypropylene glycol block copolymer (average molecular weight 1250): manufactured by NOF Corporation, "Pronon 102"
Polyoxyethylene glycol-polyoxypropylene glycol block copolymer (average molecular weight 3330): NOF Corporation, "Pronon 204"
Polyoxyethylene glycol-polyoxypropylene glycol block copolymer (average molecular weight 10,000): “Pronon 208” manufactured by NOF Corporation
Polyoxypropylene triol (average molecular weight 1500): “SANNICS GP-1500” manufactured by Sanyo Chemical Industries
Sodium hexametaphosphate: made by ALDRICH Nonionic surfactant: made by Big Chemie Japan "DISPER BYK193"
Diethyl phosphate: Wako Pure Chemical Industries, Ltd.

  From Tables 1 and 2, in Examples 1-28, the spark voltage in the electrolytic solution for electrolytic capacitors is higher than in Comparative Examples 1-8, and the electrical conductivity and spark voltage change over time even under high temperature conditions of 105 ° C. It was found that it was maintained for a long time because there were few.

  The electrolytic solution for electrolytic capacitors of the present invention has a high spark voltage, and can maintain electrical conductivity and spark voltage at a high temperature for a long period of time. Therefore, it is used not only for electrolytic capacitors but also in a wide range of industrial fields. be able to.

Claims (7)

  An electrolytic solution for an electrolytic capacitor, comprising at least a polyether polyol, colloidal silica, an electrolyte salt, and an organic solvent.   2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein a mass ratio of the polyether polyol to the colloidal silica is 0.01 to 10. 5.   The electrolyte solution for electrolytic capacitors according to claim 1 or 2, wherein the polyether polyol has an average molecular weight of 500 to 10,000.   The polyether polyol is at least one selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, polyoxypropylene triol, polytetramethylene ether glycol, polyoxyethylene glycol-polyoxypropylene glycol block copolymer. The electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 3, wherein:   The electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 4, wherein the content of the polyether polyol in the electrolytic solution for an electrolytic capacitor is 0.01 to 20% by mass. 6. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the electrolyte salt is any one of compounds represented by the following general formulas (1) to (5).

(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.)   An electrolytic capacitor comprising the electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 6.