JP7340650B2 - Electrolytic solution for electrolytic capacitors and electrolytic capacitors using the electrolytic solution - Google Patents

Description

The present invention relates to an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor using the electrolytic solution.

BACKGROUND OF THE INVENTION Electrolytic capacitors are widely used in various electrical and electronic products, and have a wide range of uses, including charge storage, noise removal, and phase adjustment. In recent years, in order to enable electrolytic capacitors to operate at higher driving voltages, there has been a growing need for improved withstand voltage, and various improvements have been attempted.

For example, Patent Document 1 discloses a technique for improving withstand voltage by incorporating a polyethylene glycol-polyacrylic acid graft copolymer or a polypropylene glycol-polyacrylic acid graft copolymer into an electrolytic solution for an electrolytic capacitor. There is.
Furthermore, Patent Document 2 discloses a technique for improving withstand voltage by incorporating an acrylic acid/methacrylic acid copolymer into an electrolytic solution for an electrolytic capacitor.

However, in the electrolytic capacitors described in Patent Documents 1 and 2, although the withstand voltage was improved, it was insufficient.
In addition, electrolytic capacitors used in automotive electrical products are expected to be used in high-temperature environments, but there is also the problem that the withstand voltage decreases at high temperatures.

Japanese Patent Application Publication No. 2002-217067 Japanese Patent Application Publication No. 7-45482

An object of the present invention is to provide an electrolytic solution for an electrolytic capacitor that has excellent withstand voltage and can suppress a decrease in withstand voltage even under high temperature conditions.

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention includes a polymer (A) having (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) as essential constituent monomers, a solvent (B), and an electrolyte for an electrolytic capacitor (C). An electrolytic solution for an electrolytic capacitor, wherein the absolute value of the difference between the solubility parameter of the (meth)acrylic monomer (a1) and the solubility parameter of the solvent (B) is 0.0 (cal/cm ³ ) ^1/2 or more 4.5 (cal/cm ³ ) ^1/2 , and the absolute value of the difference between the solubility parameter of the (meth)acrylic monomer (a2) and the solubility parameter of the solvent (B) is 4.5 (cal/cm 3 ). cm ³ ) ^1/2 or more and 7.5 (cal/cm ³ ) ^1/2 or less, and the solvent (B) contains alcohol with a molecular weight of 600 or less; It is an electrolytic capacitor containing.

An electrolytic capacitor using the electrolytic solution for electrolytic capacitors of the present invention has excellent withstand voltage, and also has the effect of suppressing a drop in withstand voltage at high temperatures.

The electrolytic solution for electrolytic capacitors of the present invention comprises a polymer (A) containing (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) as essential constituent monomers, a solvent (B), and an electrolyte for electrolytic capacitors. (C).
In addition, in the present invention, the expression "(meth)acryloyl" means acryloyl and/or methacryloyl, the expression "(meth)acrylate" means acrylate and/or methacrylate, and the expression "(meth)acryloyl" means acryloyl and/or methacryloyl. '' means acrylic and/or methacrylic, and the expression ``(meth)acryloyloxy'' means acryloyloxy and/or methacrylyloxy.

The above polymer (A) is a polymer containing (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) as essential constituent monomers.
The absolute value of the difference between the solubility parameter (hereinafter abbreviated as SP value) of the (meth)acrylic monomer (a1) and the SP value of the solvent (B) is 0.0 (cal/cm ³ ) ^{1/ 2} or more and 4.5 (cal/cm ³ ) ^1/2 or more, and from the viewpoint of withstand voltage and solubility at room temperature, it is 1.0 (cal/cm ³ ) ^1/2 or more and 4.0 ( Cal/cm ³ ) ^1/2 or less is preferable, and more preferably 2.0 (cal/cm ³ ) ^1/2 or more and 3.0 (cal/cm ³ ) ^1/2 or less.
Further, the absolute value of the difference between the SP value of the (meth)acrylic monomer (a2) and the SP value of the solvent (B) is 4.5 (cal/cm ³ ) ^1/2 or more and 7.5 (cal/cm ³ ) It is ^1/2 or less. If it exceeds 7.5 (cal/cm ³ ) ^1/2 , there is a problem that the withstand voltage at high temperatures decreases. The absolute value of the difference between the SP value of the (meth)acrylic monomer (a2) and the SP value of the solvent (B) is preferably 4.5 (cal/cm ³ ) ^1/2 or more and 7.0 (cal/cm ³ ) ^1/2 or less, more preferably 5.0 (cal/cm ³ ) ^1/2 or more and 6.5 (cal/cm ³ ) ^1/2 or less.
Note that the SP value in the present invention was calculated by the method described in "Polymer Engineering and Science" by Robert F. Fedors et al., Volume 14, pages 147-154. It is.

In addition, when the above-mentioned polymer (A) has two or more types of (meth)acrylic monomers (a1) as constituent units, the SP value of the (meth)acrylic monomer (a1) is ) is the weighted average of the SP values of each (meth)acrylic monomer corresponding to their weight ratios. Even when the polymer (A) has two or more types of (meth)acrylic monomers (a2) as constituent units, the SP value of the (meth)acrylic monomer (a2) is calculated in the same manner. However, the SP value of each (meth)acrylic monomer corresponding to (meth)acrylic monomer (a1) must be larger than the SP value of each (meth)acrylic monomer corresponding to (meth)acrylic monomer (a2). be.
In addition, when the solvent (B) is a mixture of two or more types of solvents, the SP value of the solvent (B) is a weighted average of the SP values of each solvent contained in the solvent (B) based on their weight ratios. Use value.

Examples of the (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) include monomers having at least one (meth)acryloyl group; ) From the viewpoint of solubility, monomers having one (meth)acryloyl group are preferred.

Preferred monomers having one (meth)acryloyl group include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Benzyl acrylate, cyclohexyl acrylate, hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerin monoacrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, succinic acid 2-( meth)acryloyloxyethyl, (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-butyl(meth)acrylamide, N,N'-dimethyl Examples include (meth)acrylamide, N,N'-diethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxypropyl (meth)acrylamide, N-hydroxybutyl (meth)acrylamide, and acryloylmorpholine.
Preferred monomers having two or more (meth)acryloyl groups include 1,4-butanediol diacrylate, 1,6-hexadiol diacrylate, polyethylene glycol diacrylate (n=4), and polyethylene glycol diacrylate (n=4). Acrylate (n=7) Polyethylene glycol diacrylate (n=14), Polypropylene glycol diacrylate (n=3), Polypropylene glycol diacrylate (n=7) Polypropylene glycol diacrylate (n=12), Trimethylolpropane triacrylate , ethylene oxide (EO) modified glycerol triacrylate, propylene oxide (PO) modified triglycerol triacrylate, pentaerythritol tetraacrylate, and the like.

Whether the above (meth)acrylic monomer corresponds to (meth)acrylic monomer (a1) or (meth)acrylic monomer (a2) is determined depending on the absolute value of the difference from the SP value of solvent (B). However, the (meth)acrylic monomer (a1) is a (meth)acrylic monomer having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, an amide group, and an oxyalkylene group having 2 to 3 carbon atoms. It is preferable that there be.

Preferred examples of the (meth)acrylic monomer (a1) include hydroxyethyl methacrylate (SP value: 12.1 (cal/cm ³ ) ^1/2 ), hydroxyethyl acrylate (SP value: 12.5 (cal/cm ) ³ ) ^1/2 ), hydroxybutyl acrylate (SP value: 11.6 (cal/cm ³ ) ^1/2 ), acrylic acid (SP value: 11.1 (cal/cm ³ ) ^1/2 ), glycerin mono Acrylate (SP value: 13.1 (cal/cm ³ ) ^1/2 ), 1,4-cyclohexanedimethanol mono(meth)acrylate (SP value: 12.2 (cal/cm ³ ) ^1/2 ), polyethylene Glycol mono(meth)acrylate [SP value when n (number of repeating oxyethylene groups) = 2: 11.8 (cal/cm ³ ) ^1/2 ; SP value when n = 4: 11.1 ( cal/cm ³ ) ^1/2 ] and N-hydroxyethylacrylamide (SP value: 14.4 (cal/cm ³ ) ^1/2 ).

In addition, as preferred (meth)acrylic monomers (a2), methyl methacrylate (SP value: 8.9 (cal/cm 3 ) ^1/2 ), n-butyl acrylate (SP value: 8.8 (cal/cm ³ ) 1/2), cm ³ ) ^1/2 ), t-butyl acrylate (SP value: 8.5 (cal/cm ³ ) ^1/2 ), 2-ethylhexyl (meth)acrylate (SP value: 8.6 (cal/cm ³ ) ^1/2 ), phenoxyethyl acrylate (SP value: 10.1 (cal/cm ³ ) ^1/2 ), benzyl acrylate (SP value: 10.1 (cal/cm ³ ) ^1/2 ), and cyclohexyl acrylate (SP value: 9.7 (cal/cm ³ ) ^1/2 ), etc.
Moreover, the above-mentioned (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) may be used alone or in combination of two or more.

The polymer (A) of the present invention may also be a polymer containing a monomer (a3) other than the essential constituent monomers (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) as a constituent monomer. .
Examples of the monomer (a3) include butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, 2-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, vinyl cyclohexyl ether, cyclohexanedimethanol monovinyl ether, acetoxyethyl vinyl ether, acetoxybutyl vinyl ether, Examples include 1-vinylimidazole, vinylcaprolactone, and N-vinylpyrrolidone.

The absolute value of the difference between the SP value of the (meth)acrylic monomer (a1) and the SP value of the (meth)acrylic monomer (a2) is 1.0 from the viewpoint of suppressing a drop in withstand voltage at high temperatures. It is preferably ^1/2 to 7.0 (cal/cm ³ ), more preferably 1.5 to 6.0 (cal/cm ³ ) ^1/2 , particularly preferably 2.0 to 5 .0 (cal/cm ³ ) ^1/2 , most preferably 2.5 to 4.0 (cal/cm ³ ) ^1/2 .
In addition, when the above-mentioned polymer (A) has two or more types of (meth)acrylic monomers (a1) as constituent units, the SP value of the (meth)acrylic monomer (a1) is ) is the weighted average of the SP values of each (meth)acrylic monomer corresponding to their weight ratios. Even when the polymer (A) has two or more types of (meth)acrylic monomers (a2) as constituent units, the SP value of the (meth)acrylic monomer (a2) is calculated in the same manner.

In addition, when there are two or more kinds of (meth)acrylic monomers (a1) and/or (meth)acrylic monomers (a2), which are the essential constituent monomers of the polymer (A), the withstand voltage drop at high temperatures can be further reduced. From the viewpoint of suppression, among the combinations of each monomer corresponding to (meth)acrylic monomer (a1) and each monomer corresponding to (meth)acrylic monomer (a2), the combination in which the absolute value of the difference in SP value is the smallest The absolute value of the difference in SP value for is preferably 1.0 to 7.0 (cal/cm ³ ) ^1/2 , more preferably 1.5 to 6.0 (cal/cm ³ ) ^{1 /2} , particularly preferably from 2.0 to 5.0 (cal/cm ³ ) ^1/2 , and most preferably from 2.5 to 4.0 (cal/cm ³ ) ^1/2 .
In addition, among the combinations of monomers corresponding to (meth)acrylic monomer (a1) and monomers corresponding to (meth)acrylic monomer (a2), the SP value for the combination with the largest absolute value of the difference in SP value The absolute value of the difference is preferably 1.5 to 7.0 (cal/cm ³ ) ^1/2 , more preferably 3.0 to 5.0 (cal/cm ³ ) ^1/2. be.

The number average molecular weight (hereinafter abbreviated as Mn) of the polymer (A) is preferably 1,000 to 100,000, more preferably 3. 000 to 50,000, particularly preferably 4,000 to 15,000.

The Mn of the polymer (A) in the present invention is measured using gel permeation chromatography (hereinafter abbreviated as GPC) under the following conditions.
Equipment (one example): HLC-8120 manufactured by Tosoh Corporation
Column (example): 2 TSK GEL GMH6 [manufactured by Tosoh Corporation]
Measurement temperature: 40℃
Sample solution: 0.25% by weight THF solution Solution injection amount: 100μl
Detection device: Refractive index detector Reference material: 12 points of TSK standard POLYSTYRENE manufactured by Tosoh Corporation (weight average molecular weight: 500 1050 2800 5970 9100 18100 37900 96400 190000 355000 1090000 2,890,000)

The weight ratio of the (meth)acrylic monomer (a1) constituting the polymer (A) is determined from the viewpoint of suppressing voltage resistance drop at high temperatures and from the viewpoint of solubility. It is preferably 50 to 99% by weight based on the total weight of a1) and (a2).
In addition, the weight ratio of the (meth)acrylic monomer (a2) constituting the polymer (A) is determined from the viewpoint of suppressing a drop in withstand voltage at high temperatures. It is preferably 1 to 50% by weight based on the total weight of a2).
In addition, when the polymer (A) includes a monomer (a3) as a constituent monomer, the weight proportion of the monomer (a3) constituting the polymer (A) is determined from the viewpoint of suppressing a decrease in withstand voltage at high temperatures. It is preferably 20% by weight or less based on the weight of all monomers constituting the polymer (A).

The above polymer (A) can be obtained by adding (meth)acrylic monomer (a1), (meth)acrylic monomer (a2) and, if necessary, monomer (a3) using a known method (as described in JP-A-5-117330, etc.). It can be synthesized by polymerization using the method described above.
For example, the monomers (a1), (a2), and if necessary (a3) are synthesized by a solution polymerization method in which the monomers (a1), (a2), and optionally (a3) are reacted together with a radical initiator (such as azobisisobutyronitrile) in a polymerization solvent (such as toluene). , and then distilling off the solvent used in the polymerization by drying under reduced pressure.

The solvent (B) contains alcohol having a molecular weight of 600 or less as an essential component.
Examples of alcohols with a molecular weight of 600 or less include methyl alcohol (SP value: 13.8 (cal/cm ³ ) ^1/2 ), ethyl alcohol (SP value: 12.1 (cal/cm ³ ) ^1/2 ), and propyl alcohol. (SP value: 11.8 (cal/cm ³ ) ^1/2 ), butyl alcohol (SP value: 11.3 (cal/cm ³ ) ^1/2 ), ethylene glycol (SP value: 14.8 (cal/cm 3 ) 1/2), cm ³ ) ^1/2 ), diethylene glycol (SP value: (cal/cm ³ ) ^1/2 ), propylene glycol (SP value: 13.5 (cal/cm ³ ) ^1/2 ), ethylene glycol monobutyl ether (SP Value: 10.8 (cal/cm ³ ) ^1/2 ), polyethylene glycol (Mn: 600 or less) (SP value: 11.2 to 10.1 (cal/cm ³ ) ^1/2 ) and glycerin (SP value :16.4 (cal/cm ³ ) ^1/2 ), etc.
Among these, ethylene glycol, propylene glycol, polyethylene glycol with a molecular weight of 600 or less, and polypropylene glycol with a molecular weight of 600 or less are preferred from the viewpoint of suppressing a drop in withstand voltage at high temperatures.

The above-mentioned solvent (B) may contain other solvents within a range that does not impede the effects of the invention. Other solvents include water, amide solvents (N-methylformamide and N,N-dimethylformamide, etc.), lactone solvents (α-acetyl-γ-butyrolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, and δ - valerolactone, etc.), nitrile solvents (acetonitrile, propionitrile, butyronitrile, acrylonitrile, methacrylnitrile, benzonitrile, etc.), sulfoxide solvents (dimethylsulfoxide, methylethylsulfoxide, diethylsulfoxide) and sulfone solvents (sulfolane and ethylmethylsulfone, etc.) etc.

The SP value of the solvent (B) is preferably 10.0 to 18.0 (cal/cm ³ ) ^1/2 , more preferably 13 .0 to 15.0 (cal/cm ³ ) ^1/2 .
In addition, when the solvent (B) is a mixture of two or more types of solvents, the SP value of the solvent (B) is a weighted average of the SP values of each solvent contained in the solvent (B) based on their weight ratios. Use value.
As the solvent (B) having an SP value within the above preferable range (10.0 to 16.0 (cal/cm ³ ) ^1/2 ), ethylene glycol (SP value: 14.8 (cal/cm ³ ) ^{1 ) /2} ), propylene glycol (SP value: 13.5 (cal/cm ³ ) ^1/2 ), diethylene glycol (SP value: 13.0 (cal/cm ³ ) ^1/2 ), and mixtures thereof.

From the viewpoint of electrical conductivity, the weight proportion of the alcohol having a molecular weight of 600 or less contained in the solvent (B) is preferably 50 to 100% by weight, more preferably 100% by weight, based on the weight of the solvent (B). It is.

As the electrolyte (C) for electrolytic capacitors, known electrolytes used in electrolytic solutions for electrolytic capacitors can be used, but an electrolyte consisting of carboxylate ions and ammonium or amidinium is preferable.

Carboxylate ions include saturated polycarboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, 2-methyl azelaic acid, sebacic acid, 1,5-octanedicarbone) acid, 4,5-octanedicarboxylic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedicarboxylic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid, butylmalonic acid, pentyl Malonic acid, hexylmalonic acid, dimethylmalonic acid, diethylmalonic acid, methylpropylmalonic acid, methylbutylmalonic acid, ethylpropylmalonic acid, dipropylmalonic acid, methylsuccinic acid, ethylsuccinic acid, 2,2-dimethylsuccinic acid, 2 , 3-dimethylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 3-methyl-3-ethylglutaric acid, 3,3-diethylglutaric acid, 3,3-dimethylglutaric acid and 3-methyladipic acid etc);
Saturated monocarboxylic acids (formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid and undecanoic acid, etc.);
Unsaturated monocarboxylic acids [(meth)acrylic acid, crotonic acid, oleic acid, etc.];
Unsaturated aliphatic polycarboxylic acids (maleic acid, fumaric acid, itaconic acid and citraconic acid, etc.);
Aromatic monocarboxylic acids (benzoic acid, cinnamic acid, naphthoic acid, toluic acid, ethylbenzoic acid, propylbenzoic acid, isopropylbenzoic acid, butylbenzoic acid, isobutylbenzoic acid, sec-butylbenzoic acid, tertiary-butylbenzoic acid) , hydroxybenzoic acid, ethoxybenzoic acid, propoxybenzoic acid, isopropoxybenzoic acid, butoxybenzoic acid, isobutoxybenzoic acid, sec-butoxybenzoic acid, tertiary-butoxybenzoic acid, aminobenzoic acid, N-methylaminobenzoic acid, N -ethylaminobenzoic acid, N-propylaminobenzoic acid, N-isopropylaminobenzoic acid, N-butylaminobenzoic acid, N-isobutylaminobenzoic acid, N-sec-butylaminobenzoic acid, N-tert-butylaminobenzoic acid acids, N,N-dimethylaminobenzoic acid and N,N-diethylaminobenzoic acid, etc.);
and aromatic polycarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, etc.) and other carboxylic acids, including anions obtained by removing a hydrogen atom from a carboxy group.
Among these, preferred from the viewpoint of withstand voltage are anions obtained by removing hydrogen atoms from the carboxy groups of saturated polycarboxylic acids and unsaturated polycarboxylic acids.

Ammonium can be used without particular limitation as long as it forms a salt with the carboxylate ion.
Examples of ammonium include unsubstituted ammonium, primary ammonium (methylammonium, ethylammonium, propylammonium, isopropylammonium, etc.), secondary ammonium (dimethylammonium, diethylammonium, methylethylammonium, methylpropylammonium, methylisopropylammonium, etc.) ), tertiary ammoniums (such as trimethylammonium, triethylammonium, dimethylethylammonium, dimethylpropylammonium and dimethylisopropylammonium) and quaternary ammoniums (tetramethylammonium, ethyltrimethylammonium, diethyldimethylammonium, triethylmethylammonium and tetraethylammonium) etc.) etc.

Amidinium can be used without particular limitation as long as it forms a salt with the carboxylate ion.
Amidinium includes imidazolinium, a cation in which the hydrogen atom of imidazolinium is substituted with an alkyl group (1,2,3,4-tetramethylimidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium), 1,3-dimethyl-2,4-diethylimidazolinium, 1,2-dimethyl-3,4-diethylimidazolinium, etc.), imidazolium, and cations in which the hydrogen atom of imidazolium is substituted with an alkyl group. (1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium, etc.).

Among ammonium and amidinium, ammonium is preferred from the viewpoint of withstand voltage, and unsubstituted ammonium, primary ammonium, and tertiary ammonium are more preferred.

The electrolytic solution for an electrolytic capacitor of the present invention may contain a boric acid compound (D) as necessary.
Examples of the boric acid compound (D) include boric acid and boric esters.
Examples of the boric acid esters include alkyl borates (triethyl borate, etc.), aryl borates (triphenyl borate, etc.), and the like.
Among these, boric acid is preferred from the viewpoint of withstand voltage.

In the electrolyte solution for electrolytic capacitors of the present invention, the weight ratio of the polymer (A) to the total weight of the electrolyte solution for electrolytic capacitors is preferably 0.5 to 40% by weight, more preferably 1 to 30% by weight. % by weight, particularly preferably from 5 to 20% by weight.
When the content of the polymer (A) is 0.5% by weight or more, the withstand voltage is good, and when it is 40% by weight or less, the electrical conductivity is good.
The weight ratio of the solvent (B) to the total weight of the electrolytic solution for electrolytic capacitors is preferably 50 to 99% by weight, more preferably 60 to 80% by weight from the viewpoint of improving withstand voltage.
The weight ratio of the electrolyte for electrolytic capacitors (C) to the total weight of the electrolytic solution for electrolytic capacitors is preferably 0.5 to 40% by weight, more preferably 5 to 30% by weight from the viewpoint of electrical conductivity.

The weight ratio of the boric acid compound (D) to the total weight of the electrolytic solution for an electrolytic capacitor is preferably 0 to 10% by weight, more preferably 0 to 5% by weight from the viewpoint of withstand voltage.

The method for producing the electrolytic solution for electrolytic capacitors of the present invention is not particularly limited.
For example, the above-mentioned polymer (A), solvent (B), electrolyte for electrolytic capacitors (C), and if necessary, boric acid compound (D) are mixed at a temperature range of 20 to 150° C. using a known mechanical mixing method. (For example, a method using a mechanical stirrer or a magnetic stirrer) can be used to uniformly mix the mixture.

The electrolytic capacitor of the present invention only needs to contain the electrolytic solution for an electrolytic capacitor of the present invention, and its shape, size, etc. are not limited. The electrolytic capacitor of the present invention is, for example, a rolled-up type electrolytic capacitor, which is wound with a separator interposed between an anode (aluminum oxide foil) having aluminum oxide formed on the anode surface and a cathode aluminum foil. An example of this is a capacitor configured by rotating the capacitor.

The electrolytic capacitor of the present invention can be produced by, for example, impregnating a separator (kraft paper, manila paper, etc.) with the electrolytic solution for an electrolytic capacitor of the present invention as a driving electrolyte, and storing it together with an anode and a cathode in a bottomed cylindrical aluminum case. After that, the opening of the aluminum case is sealed with sealing rubber (butyl rubber, silicone rubber, etc.).

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. Note that in the following, Examples 7, 17, 18, and 21 are Reference Examples 1 to 4, respectively.

Moreover, Mn of the polymer (A) synthesized in the production example and the comparative production example was measured using GPC under the following conditions.
Equipment: HLC-8120 manufactured by Tosoh Corporation
Column: TSK GEL GMH6 2 pieces [manufactured by Tosoh Corporation]
Measurement temperature: 40℃
Sample solution: 0.25% by weight THF solution Solution injection amount: 100μl
Detection device: Refractive index detector Reference material: 12 points of TSK standard POLYSTYRENE manufactured by Tosoh (weight average molecular weight: 500 1050 2800 5970 9100 18100 37900 96400 190000 355000 1090000 28 90000)

<Production Example 1: Synthesis of polymer (A-1)>
In a flask equipped with a stirrer, a thermometer, and a cooling tube, 200 parts by weight of methyl isobutyl ketone [manufactured by Wako Pure Chemical Industries, Ltd.], 70 parts by weight of hydroxyethyl methacrylate [manufactured by Tokyo Chemical Industry Co., Ltd.], and methyl methacrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] were added. 30 parts by weight (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added and heated to 80°C. A previously prepared solution of 1 part of azobisisobutyronitrile [manufactured by Wako Pure Chemical Industries, Ltd.] dissolved in 5 parts by weight of methyl isobutyl ketone was added dropwise over 3 hours. After the dropwise addition was completed, the mixture was further heated for 3 hours. Thereafter, methyl isobutyl ketone was distilled off by drying under reduced pressure at 100° C. and 0.5 kPa to synthesize polymer (A-1).

<Production Example 2: Synthesis of polymer (A-2)>
In Production Example 1, 70 parts by weight of hydroxyethyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] and 30 parts by weight of n-butyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] were used in place of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-2) was synthesized in the same manner as in Production Example 1 except for this.

<Production Example 3: Synthesis of polymer (A-3)>
In Production Example 1, 70 parts by weight of hydroxybutyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.], 15 parts by weight of methyl methacrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] and t-butyl acrylate were used in place of hydroxyethyl methacrylate and methyl methacrylate. [Manufactured by Tokyo Kasei Kogyo Co., Ltd.] Polymer (A-3) was synthesized in the same manner as in Production Example 1 except that 15 parts by weight was used.

<Production Example 4: Synthesis of polymer (A-4)>
Polymer (A-4) was synthesized in the same manner as in Production Example 1, except that 70 parts by weight of acrylic acid [manufactured by Tokyo Chemical Industry Co., Ltd.] was used in place of hydroxyethyl methacrylate.

<Production Example 5: Synthesis of polymer (A-5)>
In Production Example 1, 70 parts by weight of glycerin monoacrylate [Blenmar GLM, manufactured by NOF Corporation] and 30 parts by weight of 2-ethylhexyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] were used in place of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-5) was synthesized in the same manner as in Production Example 1 except for using the following.

<Production Example 6: Synthesis of polymer (A-6)>
In Production Example 1, 70 parts by weight of 1,4-cyclohexanedimethanol monoacrylate [manufactured by Nippon Kasei Co., Ltd.] and phenoxyethyl acrylate [Viscoat #192, Osaka Organic Chemical Industry Co., Ltd.] were used instead of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-6) was synthesized in the same manner as in Production Example 1, except that 30 parts by weight (manufactured by )) was used.

<Production Example 7: Synthesis of polymer (A-7)>
Production examples except that in Production Example 1, 70 parts by weight of acrylamide [manufactured by Tokyo Kasei Kogyo Co., Ltd.] and 30 parts by weight of benzyl acrylate [manufactured by Tokyo Kasei Kogyo Co., Ltd.] were used instead of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-7) was synthesized in the same manner as in 1.

<Production Example 8: Synthesis of polymer (A-8)>
In Production Example 1, 70 parts by weight of polyethylene glycol [n (number of repeating oxyethylene groups) = 2] monoacrylate [Blemmer AE-90, manufactured by NOF Corporation] was used in place of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-8) was synthesized in the same manner as in Production Example 1, except that 30 parts by weight of cyclohexyl acrylate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) were used.

<Production Example 9: Synthesis of polymer (A-9)>
In Production Example 1, 70 parts by weight of polyethylene glycol [n (number of repeating oxyethylene groups) = 4] monoacrylate [Blemmer AE-200, manufactured by NOF Corporation] was used in place of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-9) was synthesized in the same manner as in Production Example 1, except that 30 parts by weight of cyclohexyl acrylate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) were used.

<Production Example 10: Synthesis of polymer (A-10)>
In Production Example 1, 30 parts by weight of hydroxyethyl methacrylate [manufactured by Tokyo Chemical Industry Co., Ltd.], 30 parts by weight of hydroxybutyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] and phenoxyethyl acrylate were used in place of hydroxyethyl methacrylate and methyl methacrylate. [Manufactured by Tokyo Kasei Kogyo Co., Ltd.] Polymer (A-10) was synthesized in the same manner as in Production Example 1 except that 40 parts by weight was used.

<Production Example 11: Synthesis of polymer (A-11)>
In Production Example 1, 90 parts by weight of hydroxybutyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] and 10 parts by weight of methyl methacrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] were used instead of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-11) was synthesized in the same manner as in Production Example 1.

<Production Example 12: Synthesis of polymer (A-12)>
In Production Example 1, 50 parts by weight of hydroxybutyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] and 50 parts by weight of phenoxyethyl acrylate [manufactured by Tokyo Chemical Industry Co., Ltd.] were used instead of hydroxyethyl methacrylate and methyl methacrylate. Polymer (A-12) was synthesized in the same manner as in Production Example 1.

<Comparative Production Example 1: Synthesis of Polymer (A'-1)>
Production Example 1 except that 72 parts by weight of acrylic acid [manufactured by Tokyo Kasei Kogyo Co., Ltd.] and 28 parts by weight of methacrylic acid [manufactured by Tokyo Kasei Kogyo Co., Ltd.] were used instead of hydroxyethyl methacrylate and methyl methacrylate. A comparative polymer (A'-1) was synthesized in the same manner as in Example 1.

<Comparative Production Example 2: Synthesis of Polymer (A'-2)>
A comparative polymer (A '-2) was synthesized.

<Comparative Production Example 3: Synthesis of Polymer (A'-3)>
A comparative polymer (A' -3) was synthesized.

Table 1 shows the SP values of each monomer constituting the polymers (A-1) to (A-14) and the comparative polymers (A'-1) to (A'-3). In addition, each monomer constituting the polymers (A-1) to (A-14) and comparative polymers (A'-1) to (A'-3) when the solvent (B) is ethylene glycol Table 1 shows the absolute value of the difference between the SP value of ethylene glycol and the SP value of ethylene glycol.
Further, Table 2 shows the absolute value of the difference between the SP value of each monomer constituting the polymer (A-1) and the SP value of propylene glycol when the solvent (B) is propylene glycol.
Also, the difference between the SP value of each monomer constituting the polymer (A-1) when the solvent (B) is a mixture of ethylene glycol and propylene glycol and the SP value of a mixture of ethylene glycol and propylene glycol. Table 2 shows the absolute value of the SP value of each monomer constituting the polymer (A-1) and the SP value of glycerin when the solvent (B) is glycerin.
Further, Table 3 shows the absolute value of the difference between the SP value of each monomer constituting the polymer (A-3) and the SP value of diethylene glycol or glycerin when the solvent (B) is diethylene glycol or glycerin.
Further, the number average molecular weights of the polymers (A-1) to (A-14) and comparative polymers (A'-1) to (A'-3) are shown in Tables 1 to 3.

<Preparation of electrolyte (C-1)>
<Manufacture example 13>
200 parts by weight of methanol and 48.5 parts by weight of azelaic acid were placed in a beaker, followed by 29.2 parts by weight of ammonium carbonate for neutralization. Thereafter, methanol was removed under reduced pressure (0.5 kPa) at 80° C. to obtain 54.0 parts by weight of ammonium azelaate (C-1).

<Preparation of electrolyte solution for electrolytic capacitors>
<Examples 1 to 21, Comparative Examples 1 to 7>
Polymers (A-1) to (A-14) as polymer (A) synthesized in the above production examples and comparative polymers (A'-1) to (A'-3) synthesized in comparative production examples. ), electrolyte for electrolytic capacitors (C), ethylene glycol as solvent (B) (SP value: 14.8 (cal/cm 3 ) ^1/2 ), propylene glycol (SP value: 13.5 (cal/cm ³ ) 1/2 ), cm ³ ) ^1/2 ), diethylene glycol (SP value: 13.0 (cal/cm ³ ) ^1/2 ) and glycerin (SP value: 16.4 (cal/cm ³ ) ^1/2 ), boric acid compound ( D) and boric acid were blended in the parts shown in Table 1 to prepare electrolytic solutions for electrolytic capacitors of Examples 1 to 21 and electrolytic solutions for comparative electrolytic capacitors of Comparative Examples 1 to 7.

Further, the conductivity and spark voltage of the electrolytic solutions for electrolytic capacitors of Examples 1 to 21 and the electrolytic solutions for comparative electrolytic capacitors of Comparative Examples 1 to 7 were evaluated using the following method. The results are shown in Table 4.

<Conductivity>
Using an electrical conductivity meter CM-40S [manufactured by Toa Denpa Kogyo Co., Ltd.], the electrical conductivity of the electrolytic solutions of Examples and Comparative Examples at 30° C. was measured.

<Spark voltage (25℃, 85℃)>
A 10 cm ² high-pressure chemically etched aluminum foil was used as the anode, a 10 cm ² plain aluminum foil was used as the cathode, and each of the electrolytes of Examples and Comparative Examples was used as the electrolyte. Next, a load was applied using a constant current method (2 mA) using a constant voltage/constant current DC power supply device [manufactured by Takasago Seisakusho Co., Ltd., GP0650-05R] at 25° C. or 85° C., and the voltage was measured. Time was plotted on the horizontal axis and voltage was plotted on the vertical axis, and the voltage rise curve over time was observed, and the voltage at the time when the rise curve first became disturbed due to sparks or scintillation was defined as the spark voltage. The higher the spark voltage, the higher the withstand voltage.

The electrolytic solutions for electrolytic capacitors of Examples 1 to 21 of the present invention exhibit excellent withstand voltage and conductivity in a room temperature environment, and also maintain excellent withstand voltage and withstand even in a high temperature environment (85°C). The voltage drop is small.
The electrolytic solution for a comparative electrolytic capacitor of Comparative Example 1 has a low withstand voltage under a room temperature environment and a temperature-lowering environment.
On the other hand, the electrolytes for comparative electrolytic capacitors of Comparative Examples 2 to 4 have improved withstand voltage in a room temperature environment compared to Comparative Example 1 without the addition of polymer (A), but in a high temperature environment of 85°C. The withstand voltage decreases significantly. This is because polymer (A'-1) and polymer (A'-2) do not have (meth)acrylic monomer (a2), which has a relatively large polarity difference with the solvent, as a constituent unit. it is conceivable that.
The electrolytic solutions for comparative electrolytic capacitors of Comparative Examples 5 and 6 have a low withstand voltage under a room temperature environment and a temperature decreasing environment. Furthermore, in the electrolytic solution for comparative electrolytic capacitors of Comparative Example 7, the polymer (A'-3) is insoluble in the solvent and cannot be used as an additive for capacitors. This is considered to be because the polymer (A'-3) does not have the (meth)acrylic monomer (a1) as a constituent unit and has a large difference in polarity from the solvent.

Since the electrolytic capacitor using the electrolytic solution for electrolytic capacitors of the present invention has excellent withstand voltage, it can be suitably used as a component of electrical products and electronic products that require high driving voltage.
Furthermore, since the electrolytic solution for electrolytic capacitors of the present invention has a high withstand voltage even at high temperatures, it is suitable as an electrolytic solution for electrolytic capacitors for mobile applications such as notebook computers that tend to reach high temperatures when driven, and particularly for in-vehicle applications.

Claims (5)

An electrolytic solution for electrolytic capacitors containing a polymer (A) containing (meth)acrylic monomer (a1) and (meth)acrylic monomer (a2) as essential constituent monomers, a solvent (B), and an electrolyte for electrolytic capacitors (C) And,
The solubility parameter of the solvent (B) is 13.0 (cal/cm ³ ) ^1/2 to 15.0 (cal/cm ³ ) ^1/2 , and the solubility parameter of the (meth)acrylic monomer (a1) is and the solubility parameter of the solvent (B) is 1.0 (cal/cm ³ ) ^1/2 to 4.0 (cal/cm ³ ) ^1/2 , and the (meth)acrylic monomer The absolute value of the difference between the solubility parameter of (a2) and the solubility parameter of solvent (B) is 4.5 (cal/cm ³ ) ^1/2 or more and 7.5 (cal/cm ³ ) ^1/2 or less. , the solvent (B) contains an alcohol having a molecular weight of 600 or less, and the weight ratio of the (meth)acrylic monomer (a1) constituting the polymer (A) is (a1) constituting the polymer (A). and (a2), and the weight proportion of the (meth)acrylic monomer (a2) constituting the polymer (A) is 50 to 99% by weight based on the total weight of the polymer (A). An electrolytic solution for electrolytic capacitors having a content of 1 to 50% by weight based on the total weight of (a1) and (a2) . The (meth)acrylic monomer (a1) is a (meth)acrylic monomer having at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, an amide group, and an oxyalkylene group having 2 to 3 carbon atoms. The electrolytic solution for an electrolytic capacitor according to claim 1. The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, wherein the polymer (A) has a number average molecular weight of 1,000 to 100,000. The absolute value of the difference between the solubility parameter of the (meth)acrylic monomer (a1) and the solubility parameter of the (meth)acrylic monomer (a2) is 1.0 to 7.0 (cal/cm ³ ) ^1/2 The electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 3 . An electrolytic capacitor comprising the electrolytic solution for an electrolytic capacitor according to any one of claims 1 to 4 .