JP2017034030A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for an electrolytic capacitor that has a sufficient voltage resistance and can be driven even in a cold district in a high voltage region since it is hardly solidified even at a low temperature (for instance at -30°C).SOLUTION: The electrolyte for an electrolytic capacitor contains an alkylene oxide adduct (A) of polyalcohol (a) of tetra valence to hexa valence and a polar solvent (B) as essential components. The content of (A) is 5 to 40 weight% on the basis of the weight of (B).SELECTED DRAWING: None

Description

  The present invention relates to an electrolytic solution for an electrolytic capacitor and an electrolytic capacitor using the same. Specifically, the present invention relates to an electrolytic solution suitable for an aluminum electrolytic capacitor.

  Conventionally, an electrolytic capacitor typified by an aluminum electrolytic capacitor has a sealed case in which an anode provided with a dielectric and a separator holding an electrolytic solution disposed between a cathode for collecting current and the anode and cathode are sealed. It has a structure housed inside and is widely known to have a wound type or a laminated type.

Here, for the purpose of increasing the withstand voltage, an electrolytic solution in which polyethylene glycol is added to the electrolytic solution has been proposed. (For example, patent document 1).

JP 62-268121 A

However, polyethylene glycol is easily solidified at a low temperature, and the temperature range in which the electrolytic capacitor can be used is narrow, so that it cannot be used in cold regions.
An object of the present invention is to provide an electrolytic capacitor having a sufficient withstand voltage that can be driven in a cold region because it is hard to solidify even at low temperatures in a high voltage region.

The inventors of the present invention have reached the present invention as a result of studies to achieve the above object.
That is, the present invention comprises an alkylene oxide adduct (A), an electrolyte (B) and a polar solvent (C) of a tetravalent to hexavalent polyhydric alcohol (a) as essential components, and the weight of (A) / (C). An electrolytic solution for electrolytic capacitors characterized by a ratio of 5/95 to 40/60; and an electrolytic capacitor using the same.

  The electrolytic capacitor of the present invention does not solidify even at a low temperature, for example, −30 ° C., and has an effect that the withstand voltage is sufficiently high.

The electrolytic solution for an electrolytic capacitor of the present invention comprises, as essential components, an alkylene oxide adduct (A) of a 4 to 6 valent polyhydric alcohol (a), an electrolyte (B) and a polar solvent (C), and (A) / The weight ratio of (C) is 5/95 to 40/60.

The alkylene oxide adduct (A) of the present invention is an alkylene oxide adduct of a tetravalent to hexavalent polyhydric alcohol (a). Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and the like may be used alone or in combination of two or more.
The kind of alkylene oxide to be added is preferably ethylene oxide from the viewpoint of easy penetration into the electrode.
When ethylene oxide is used in combination with other alkylene oxides, 70 mol% or more of alkylene oxide is preferably ethylene oxide, and more preferably 85 mol% or more from the viewpoint of facilitating penetration into the electrode. . When 70 mol% or more of the alkylene oxide is ethoxide, there is an effect of increasing the withstand voltage.

Examples of the 4- to 6-valent polyhydric alcohol (a) include tetravalent alcohols such as pentaerythritol; pentavalent alcohols such as xylitol; hexavalent alcohols such as sorbitol, mannitol, and dipentaerythritol.
Of these, (a) is preferably a hexavalent polyhydric alcohol, more preferably sorbitol and mannitol, and most preferably sorbitol.
On the other hand, an alkylene oxide adduct of monohydric to trihydric alcohol is hard to use as an electrolyte because it is solidified at a low temperature.
12-42 mol is preferable and, as for the average addition mole number of the alkylene oxide to a polyhydric alcohol (a), More preferably, it is 18-30 mol.
When the average number of added moles is less than 12 moles, the effect of increasing the withstand voltage is weak, and when it exceeds 42 moles, the viscosity is excessively increased and it is difficult for the separator to soak the electrolyte when assembling the capacitor.

The number average molecular weight of the alkylene oxide adduct (A) of the tetravalent to hexavalent polyhydric alcohol (a) is preferably 1,000 to 2,200, more preferably 1,000 to 1,500, from the viewpoint of conductivity. It is. If it is less than 1,000, the effect of increasing the withstand voltage is weak, and if it exceeds 2,200, it is difficult to impregnate the separator with the electrolyte when assembling the capacitor.

As a method for synthesizing an alkylene oxide adduct (A) of a tetravalent to hexavalent polyhydric alcohol, it is common to react polyhydric alcohol with ethylene oxide or propylene oxide under a potassium hydroxide or sodium hydroxide catalyst. is there.
In the aluminum electrolytic capacitor application, which is the present application, since metal ions cause a short circuit of the capacitor, potassium or sodium needs to be reduced to 10 ppm or less, preferably 1 ppm or less by an adsorption treatment or the like.

The electrolyte (B) of the present invention is not particularly limited as long as it is an electrolyte that is usually used in an electrolytic solution for an electrolytic capacitor. The electrolyte (B) is composed of a cation component (B1) and an anion component (B2). .

As the cation component (B1), ammonia cation; cation of secondary amine such as dimethylamine, ethylmethylamine, diethylamine; cation of tertiary amine such as trimethylamine, triethylamine; tetramethylammonium, 1,2,3,4- There are quaternary ammonium cations such as tetramethylimidazolinium and 1-ethyl-2,3-methylimidazolinium, which may be used alone or in combination of two or more. Of these, ammonia cations and secondary amines are preferred, and ammonia cations are more preferred.

Anionic component (B2) is a carboxylic acid such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 1,10-decanedicarboxylic acid, maleic acid, phthalic acid, citraconic acid Anions; phosphate anions such as phosphate anions and phosphate esters; borate anions and borate derivative anions.
Of these, a carboxylate anion is preferable, and an aliphatic carboxylate anion having 4 to 12 carbon atoms is more preferable.
Anions may be used alone or in combination of two or more.

The polar solvent (C) of the present invention is not particularly limited as long as it is a polar solvent usually used in an electrolytic solution for electrolytic capacitors. For example, (1) alcohol, (2) amide, (3) lactone, (4) nitrile , (5) sulfone and (6) other polar organic solvents.

(1) Alcohol Monohydric alcohol (methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diacetone alcohol, benzyl alcohol, amino alcohol, furfuryl alcohol, etc.) Dihydric alcohol (ethylene glycol, propylene glycol, diethylene glycol, hexylene) Glycol, etc.), trihydric alcohol (glycerin, etc.), tetravalent or higher alcohol (hexitol, etc.), etc.

(2) Amide formamide (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, etc.), acetamide (N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide) N, N-diethylacetamide, etc.), propionamide (N, N-dimethylpropionamide, etc.), pyrrolidone (N-methylpyrrolidone, N-ethylpyrrolidone, etc.), hexamethylphosphorylamide, etc.

(3) Lactone γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, and the like.

(4) Nitrile Acetonitrile, propionitrile, butyronitrile, acrylonitrile, methacrylonitrile, benzonitrile and the like.

(5) Sulfone sulfolane, dimethyl sulfoxide, ethyl methyl sulfone and the like.

(6) Other organic solvents 1,3-dimethyl-2-imidazolidinone and the like.

    These polar solvents (C) may be used alone or in combination of two or more. Of these, alcohol and lactone are preferable, ethylene glycol and γ-butyrolactone are more preferable, and ethylene glycol is most preferable.

The weight ratio (A) / (C) of the alkylene oxide adduct (A) and the polar solvent (C) in the electrolytic solution of the present invention is 5/95 to 40/60, and 7/90 to 30/70 is Further preferred.
When the weight ratio (A) / (C) is less than 5/95, the withstand voltage becomes insufficient. On the other hand, when it exceeds 40/60, the viscosity increases. Therefore, when assembling the capacitor, the electrolyte is immersed in the separator. It becomes difficult to penetrate.

If necessary, various additives usually used in the electrolytic solution can be added to the electrolytic solution of the present invention.
For the purpose of absorbing hydrogen gas generated slightly during driving, for example, nitro compounds such as o-nitrobenzoic acid, p-nitrobenzoic acid, m-nitrobenzoic acid, o-nitrophenol, p-nitrophenol, etc. Is added. In addition, boric acid or the like is added to increase the withstand voltage. The addition amount is preferably 5% by weight or less, particularly preferably 0.1 to 2% by weight, based on the weight of the electrolytic solution, from the viewpoint of specific conductivity and solubility in the electrolytic solution.

The electrolytic solution for electrolytic capacitors of the present invention is optimal for aluminum electrolytic capacitors.
The aluminum electrolytic capacitor is not particularly limited. For example, it is a scraped electrolytic capacitor, and a separator is interposed between an anode (aluminum oxide foil) in which aluminum oxide is formed on the anode surface and a cathode aluminum foil. For example, a capacitor formed by winding is used.
A separator is impregnated with the electrolytic solution of the present invention as a driving electrolytic solution, housed in a bottomed cylindrical aluminum case together with a positive electrode, and then the aluminum case opening is sealed with a sealing rubber to form an electrolytic capacitor. Can do.

  Next, specific examples of the present invention will be described, but the present invention is not limited thereto.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, “%” represents “% by weight” and “parts” represents “parts by weight”.

Production Example 1
To 182 parts by weight (1 mol) of hexavalent sorbitol (a-1), 1.1 parts by weight (0.02 mol) of potassium hydroxide was added, and 880 parts by weight (20 mol) of ethylene oxide was reacted at 170 ° C. The end point was reached when it reached. Thereafter, potassium hydroxide was adjusted to 1 ppm or less using Kiyoward 600 and Kiyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.) as adsorbents for removing potassium hydroxide. It was confirmed that a 20-mol adduct of sorbitol with ethylene oxide (A-1) was obtained with a proton nuclear magnetic resonance apparatus (H-NMR) chart and a hydroxyl value.

Production Example 2
The reaction was carried out in the same manner as in Production Example 1 except that the number of reaction parts of ethylene oxide was 1320 parts by weight (30 mol) to obtain an adduct of 30 mol of ethylene oxide of sorbitol (A-2).

Production Example 3
Except for changing sorbitol to 182 parts by weight (1 mol) of hexavalent mannitol (a-2), a 20-mole ethylene oxide adduct (A-3) of mannitol was obtained in the same manner as in Production Example 1.

Production Example 4
Addition of sorbitol ethylene oxide 12 mol / propylene oxide 8 mol in the same manner as in Production Example 1 except that 880 parts by weight (20 mol) of ethylene oxide was changed to 528 parts by weight (12 mol) of ethylene oxide and 472 parts by weight (8 mol) of propylene oxide. A product (A-4) was obtained.

Comparative production example 1
Except having changed sorbitol into 92 weight part (1 mol) of trivalent glycerol (a'-1), it carried out similarly to manufacture example 1, and obtained the ethylene oxide 20 mol adduct (A'-1) of glycerol.

Example 1
Sorbitol ethylene oxide 20 mol adduct (A-1) and ethylene glycol (B-1) were mixed in the number of parts (parts by weight) listed in Table 1. Thereafter, 8 parts by weight of 1,6-decanedicarboxylic acid was added to 100 parts by weight of this solution, and 1 part by weight of ammonia gas was blown and dissolved while neutralization to obtain an electrolyte solution of Example 1. The pH was 6.9.

Examples 2-4, Comparative Examples 1-3
According to the number of parts (parts by weight) described in Table 1, the same operation as in Example 1 was performed to obtain electrolytic solutions of Examples 2 and 3 and Comparative Examples 1 to 3.

Using the electrolytic solutions obtained in Examples 1 to 4 and Comparative Examples 1 to 3, the low temperature (−30 ° C.) state was visually observed by the method shown below, and the results of measuring the conductivity are shown in Table 1. Described.

[Electrolyte state at −30 ° C.]
The electrolyte was placed in a transparent glass bottle, left in a -30 ° C. constant temperature bath for 24 hours, tilted at −30 ° C., visually observed, and evaluated according to the following criteria.
○: Transparent, no precipitate, and fluid when tilted. Δ: Slightly clouded, but uniform as a whole, fluid when tilted. X: Solidified as a whole.

[Measurement of conductivity]
The conductivity (mS / cm) at 30 ° C. was measured using a conductivity meter CM-40S (manufactured by Toa Denpa Kogyo Co., Ltd.).

[Measurement of withstand voltage]
When a 10 cm ² high pressure chemical etching aluminum foil is used for the anode and a 10 cm ² plain aluminum foil is used for the cathode, and a constant current (2 mA) is loaded at 25 ° C., a voltage drop (short) is observed. The withstand voltage was read by reading the voltage value. It measured using GP650-05R made from Takasago Seisakusho as a direct current stabilization power supply.

The electrolytic solutions of Examples 1 to 4 of the present invention were transparent even at −30 ° C., had no deposits, were fluid, and had high electrical conductivity.
On the other hand, the electrolytic solution of Comparative Example 1 using an alkylene oxide adduct of a trivalent alcohol solidifies at -30 ° C., and the weight ratio of (A) / (C) is less than the lower limit. The electrolyte solution was solidified as a whole and had a low withstand voltage. On the other hand, the electrolytic solution of Comparative Example 2 in which the weight ratio of (A) / (C) was equal to or higher than the upper limit had low conductivity.

Since the electrolytic solution of the present invention is an electrolytic capacitor that does not solidify even at a low temperature and can be driven even in a cold region, it can be suitably used for outdoor use, for example, on-vehicle use.

Claims (5)

  The alkylene oxide adduct (A), the electrolyte (B) and the polar solvent (C) of the tetravalent to hexavalent polyhydric alcohol (a) are essential components, and the weight ratio of (A) / (C) is 5/95 to An electrolytic solution for an electrolytic capacitor, wherein the electrolytic solution is 40/60. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein 70 mol% or more of the alkylene oxide of (A) is ethylene oxide. The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, wherein the average added mole number of the alkylene oxide (A) is 12 to 42. The additive for electrolytic capacitors according to any one of claims 1 to 3, wherein (A) has a weight average molecular weight of 1,000 to 2,200. The electrolytic capacitor using the electrolyte solution for electrolytic capacitors in any one of Claims 1-4.