JPH03126209A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve voltage resistance by adding sorbitol fatty acid ester containing predetermined composition to electrolyte for an electrolytic capacitor containing organic polarizable solvent as main solvent and organic acid, inorganic acid or its salts as solute. CONSTITUTION:Sorbitol fatty acid ester represented by a general formula is added to electrolyte for an electrolytic capacitor containing organic polarizable solvent as main solvent and organic acid, inorganic acid or its salts as solute. In the formula, Y1 to Y6 are the same or different -(R), -X, hydrogen atoms, higher acyl group, wherein at least one is higher acyl group or higher alcohol residue, R ls ethylene oxide and/or propylene oxide, and a is 1 or more integer numbers. The a in the polyalkylene is suitable if in a range preferably from 1 to 100 since if the polymerization becomes high, its synthesis becomes difficult or solubility is lowered.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the improvement of an electrolytic solution for electrolytic capacitors,
In particular, it relates to an electrolytic solution for electrolytic capacitors with improved voltage resistance.

[Prior Art] A typical electrolytic capacitor consists of an anode electrode foil with an insulating oxide film layer formed on the surface of a roughened valve metal foil such as aluminum or tantalum, and a cathode electrode foil for current collection. A capacitor element is formed by winding the capacitor with electrolytic paper interposed therebetween, and the capacitor element is impregnated with an electrolytic solution and housed in an exterior case.

The oxide film layer formed on the anode electrode foil of the capacitor element serves as a dielectric, and the electrolyte solution serves as an electrolyte layer. The electrolytic solution, which is this electrolyte layer, acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer formed on the anode foil and the cathode foil for current collection, and its resistance is inserted in series with the electrolytic capacitor.

Therefore, if the conductivity of the electrolytic solution is low, the equivalent series resistance inside the electrolytic capacitor will increase, which will adversely affect the high frequency characteristics and loss characteristics. However, when the conductivity of the electrolyte is improved during boat fishing, the spark voltage tends to decrease, and the withstand voltage characteristics of the electrolytic capacitor may be impaired. Conversely, when various additives are added to improve the withstand voltage characteristics, the electrical conductivity decreases, resulting in increased loss.

Therefore, as a means to improve the withstand voltage characteristics of an electrolytic capacitor without reducing its conductivity, it has been proposed to add various additives to the electrolytic solution.

For example, sulfamic acid (JP-A-49-82963)
, superric acid (JP-A-49-133860), dodecyl phosphate (JP-A-49-73659), alkyl phosphoric acid (JP-A-52-153154), diphosphorous acid (JP-A-57-141913) ), boric acid-mannitol system (JP-A-57-60829), boric acid-mannitol-polyvinyl alcohol system (JP-A-59-177915), modified silicone oil (JP-A-1-175722), etc. be.

[Problems to be Solved by the Invention] However, as the scope of use of electronic devices increases, there is a growing demand for improvements in the performance of electrolytic capacitors, and the conductivity of conventional electrolytes is no longer sufficient. Therefore, it is necessary to further improve the conductivity of the electrolytic solution, and as a result, it becomes difficult to maintain voltage resistance characteristics.

An object of the present invention is to provide an electrolytic solution that maintains high electrical conductivity and has improved withstand voltage characteristics.

[Means to solve the problem]

An electrolytic solution for electrolytic capacitors with an organic polar solvent as the main solvent and an organic acid, an inorganic acid, or a salt thereof as a solute has the general formula: % formula % (wherein, Y and Y are the same or different, respectively). RhX represents a hydrogen atom, a higher acyl group, at least one is a higher acyl group, and -+RhX
In, X is a hydrogen atom, a higher acyl group or a higher alcohol residue, R is ethylene oxide and/or propylene oxide, and a represents an integer of 1 or more. ) is characterized by the addition of sorbitol fatty acid ester.

Note that a in the general formula of polyalkylene is not particularly limited as long as it is 1 or more, but if the degree of polymerization becomes extremely high, disadvantages such as difficulty in synthesis and decreased solubility will occur, so preferably Approximately 1 or more and 100 or less.

Further, specific examples of so-called higher alcohols having 6 or more carbon atoms corresponding to polyoxyalkylene alkyl (alkenyl) ethers include hexyl alcohol, heptyl alcohol, octyl alcohol, cabtyl alcohol,
Nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol,
Examples include myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nanodecyl alcohol, eicosyl alcohol, ceryl alcohol, mericyl alcohol, oleyl alcohol, phytol, and the like.

In addition, as fatty acids corresponding to fatty acids and fatty acid polyoxyalkylenes in sorbitol fatty acid esters, there are saturated fatty acids represented by the general formula: CL(CL)-COON (n is an integer of 9 or more), such as undecyl acid ( n・9
), lauric acid (n・10), tridecylic acid (n・11
), myristic acid (n・12), pentadecyl acid (n・
13), palmitic acid (n=14), heptadecylic acid (
n・15), stearic acid (n=16), nonadecanoic acid (n=17), arachidic acid (n・18), behenic acid (n
= 20), lignoceric acid (n = 22), cerotic acid (
n=24), heptacanoic acid (n=25), montanic acid (n=27), melisic acid (n=28), lafcelic acid (
n・30), etc.

In addition, as an unsaturated fatty acid, undecylic acid <10> (1
1), oleic acid (cis) <9> (18), elaidic acid (trans) <9> (18), cetoleic acid <11> (22), erucic acid (sis) d3> (22)
, brassic acid (trans) d3> (22), linoleic acid <9.12> (18), linuric acid <9.12
．． 15>(18), arachidonic acid<5.8. IL
14>(20), stearol acid triple bond, 9>(
1B) [<> indicates the position of an unsaturated bond, and () indicates the total number of carbon atoms].

The organic polar solvent that is the main solvent of the electrolyte according to the present invention includes ethanol, propatool, protic polar solvent,
There are monohydric alcohols such as butanol and pentanol, polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, and methoxyethanol, and alcohol ethers. Examples of aprotic polar solvents include N-methylformamide, N, Examples include amide-based polar solvents such as N-dimethylformamide, N-ethylformamide, and N,N-diethylformamide, lactones such as T-butyrolactone, N-methyl-2-pyrrolidone, and ethylene carbonate, and cyclic amide-based solvents. In addition, nitrile systems such as acetonitrile, and oxide systems such as dimethyl sulfoxide can be exemplified as aprotic polar solvents.
These main solvents can be used alone or in combination.

Further, the electrolyte used in this invention is not particularly limited, and any commonly used electrolyte may be used. For example, anion sources include organic acids such as aliphatic monocarboxylic acids such as formic acid and acetic acid, aliphatic dicarboxylic acids such as malonic acid and succinic acid, and aromatic carboxylic acids such as benzoic acid and phthalic acid. , boric acid, phosphoric acid, silicic acid, etc. Examples of cation sources include monoalkylammonium cations such as ammonium and methylammonium, dialkylammonium cations such as dimethylammonium and diethylammonium, trialkylammonium cations such as trimethylammonium and triethylammonium, tetramethylammonium, and triethylmethylammonium. There are quaternary ammonium cations such as phosphonium and arsonium cations.

The electrolytic solution for an electrolytic capacitor according to the present invention is prepared by preparing 100 parts by weight of one or more of the above-mentioned organic polar solvents, and adding a solute consisting of an electrolyte substance in a solvent mixed with 0 to 30 parts by weight of water as required. What is necessary is just to melt|dissolve 1-50 weight part individually or in combination of several. Then, the above-mentioned sorbitol fatty acid ester is added to such an electrolytic solution, preferably 0.1 to 20 parts by weight, more preferably 0.5 to 20 parts by weight.
Desired characteristics can be obtained by adding 6 parts by weight.

[For production]

The effect of improving the withstand voltage characteristics of the sorbitol fatty acid ester used in this invention involves the formation of a micelle layer of the sorbitol fatty acid ester as a nonionic surfactant at the interface of the aluminum oxide film, which is the dielectric of the electrolytic capacitor. It is considered that

〔Example〕

Examples of the electrolytic solution for electrolytic capacitors according to the present invention will be described below.

In each example, an electrolytic solution was prepared using the same solvent and solute as in the conventional example, and sorbitol fatty acid ester was added thereto. The following sorbitol fatty acid esters were used.

A) Tetralyoxyethylene solpifthodioleate [total sum of 1 to P = 40] B) Bentapolyoxyethylene bolioxib biren sorbiftostearate) CHZ OCo
C+tHas [sum of l to q = 30/sum of f to j = 20]
C) Cypolyoxib lanthisylate ■Birensorbitobentatesylenate ester 'LIIuLL [sum of m to n = 30] D) Polyoxyethylene sorbitoleic acid ester 1 A) Tetrapolyoxyethylene sorbitoleic acid ester Acid ester large” l jiang l [sum of l or p = 601 E) Sorbitol oleate ester C8! O-CC+J! a HOH C)! OR HOR A) Tetrapolyoxyethylene sorbitoleic acid ester tlzU LJ-SiM? 1133 fruit”L
11i B) Pentapolyoxyethylene polyoxypropylene sorbitol stearate C) Dipolyoxypropylene hexyl ether sorbitol 11i B) Pentapolyoxyethylene Polyoxypropylene sorbitol stearate C) Dipolyoxypropylene hexyl ether sorbitol decylenic acid ester (Large) U block D) Tetraoleic acid polyoxyethylene sorbitoleic acid ester [Example] E) Sorbitol dioleic acid As can be seen from the above results, the electrical conductivity of the electrolytic solution of the present invention tends to be the same or slightly lower than that of the conventional example, but the withstand voltage can be improved by about 10% to 50%. Ta.

〔Effect of the invention〕

As described above, this invention uses an organic polar solvent as the main solvent,
An electrolytic solution for an electrolytic capacitor containing an organic acid, an inorganic acid, or a salt thereof as a solute has a general formula: % formula % (wherein, Y, to Y6 are the same or different, respectively -(-R)-X, a hydrogen atom, represents a higher acyl group, at least one is a higher acyl group, and -fR)r
In X, X is a hydrogen atom, a higher acyl group or a higher alcohol residue, R is ethylene oxide and/or propylene oxide, and a represents an integer of 1 or more. )
By adding a small amount of these additives to a normal electrolytic solution, it is possible to improve the withstand voltage characteristics while maintaining the electrical conductivity. Therefore, the electrical characteristics at high voltages are well stabilized, and the reliability of the electrolytic capacitor using this electrolyte is improved.

Claims (1)

[Claims] (1) The electrolytic solution for electrolytic capacitors has an organic polar solvent as the main solvent and an organic acid, an inorganic acid, or a salt thereof as a solute, and has a general formula: ▲Mathematical formula, chemical formula, table, etc.▼ (In the formula, Y_1 to Y_6 represent the same or different -(R)_a-X, a hydrogen atom, or a higher acyl group, at least one of which is a higher acyl group, and -(
In R)_a-X, X is a hydrogen atom, a higher acyl group or a higher alcohol residue, R is ethylene oxide and/or propylene oxide, and a represents an integer of 1 or more. ) An electrolytic solution for electrolytic capacitors, characterized by the addition of sorbitol fatty acid ester.