JP6473114B2 - Electrolytic solution for electrolytic capacitors - Google Patents

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).

 Moreover, what uses the addition form of ethylene oxide and propylene oxide whose addition form is a block is proposed (for example, patent document 2).

JP 62-268121 A JP-A-7-169653

However, neither polyethylene glycol nor block adducts of ethylene oxide and propylene oxide are easily solidified at a low temperature, and the temperature range in which an electrolytic capacitor can be used is narrow, so that it cannot be used in a cold region.
Accordingly, an object of the present invention is to provide an electrolytic capacitor that can be driven in a cold region and has a sufficient withstand voltage because it is difficult to solidify even at a low temperature.

The inventors of the present invention have reached the present invention as a result of studies to achieve the above object.
That is, in the present invention, the alkylene oxide adduct (A), the electrolyte (B) and the polar solvent (C) of the trivalent to hexavalent polyhydric alcohol (a) are essential components, and the alkylene oxide adduct (A) is the following: An electrolytic solution for an electrolytic capacitor characterized by being represented by the general formula (1); and an electrolytic capacitor using the same.

  The electrolytic capacitor of the present invention does not solidify even at a low temperature, for example, −20 ° C., and has an effect that the withstand voltage is sufficiently high.

The electrolytic solution for electrolytic capacitors of the present invention comprises an alkylene oxide adduct (A), an electrolyte (B) and a polar solvent (C) of a tri- to hexavalent polyhydric alcohol (a) as essential components, and an alkylene oxide adduct ( A) is represented by the following general formula (1).

[K represents the number of added moles of ethylene oxide, and is independently a number of 1 to 70. m represents the number of added moles of ethylene oxide, and is independently a number of 1 to 150. n represents the number of added moles of propylene oxide, and is independently a number from 1 to 150. f represents the valence of the polyhydric alcohol (a) and is an integer of 3-6. R represents a residue obtained by removing a hydroxyl group from an f-valent alcohol. A represents a hydrogen atom, an alkyl group, or an allyl group. “/” Indicates that the addition form of ethylene oxide and propylene oxide is random. ]

K of General formula (1) represents the addition mole number of ethylene oxide, and is the number of 1-70 each independently, Preferably, it is 5-30, More preferably, it is 10-30.
If it is less than 1, the effect of improving the withstand voltage is reduced, and if it exceeds 70, the low temperature characteristics are deteriorated.

M in the general formula (1) represents the number of added moles of ethylene oxide, and is independently a number of 1 to 150, preferably 5 to 100, more preferably 5 to 60, Preferably it is 5-30. If it is less than 1, the effect of improving the withstand voltage is reduced, and if it exceeds 150, the low temperature characteristics are deteriorated.

N in the general formula (1) represents the number of added moles of propylene oxide, and is independently a number of 1 to 150, preferably 2 to 50, more preferably 3 to 20, Preferably it is 3-10. If it is less than 1, the low-temperature characteristics deteriorate, and if it exceeds 150, the low-temperature characteristics and the withstand voltage improvement effect deteriorate.

In the general formula (1), f represents the valence of the polyhydric alcohol (a), but the alkylene oxide adduct (A) of the present invention adds an alkylene oxide of a 3-6 valent polyhydric alcohol (a). , R is an integer of 3 to 6, and R represents a residue obtained by removing a hydroxyl group from the polyhydric alcohol (a).

A at the terminal of the general formula (1) represents a hydrogen atom, an alkyl group, or an allyl group, and a hydrogen atom is preferable from the viewpoint of solubility.

The total number of moles of ethylene oxide in the alkylene oxide adduct (A), that is, (k + m) × f is preferably from 10 to 130, more preferably from 10 to 90, most preferably from 12 to 60. If it is less than 10, the effect of improving the withstand voltage is small, and if it exceeds 130, the low temperature characteristics are inferior.

The number average molecular weight (molecular weight converted from the hydroxyl value) of the alkylene oxide adduct (A) is preferably 200 to 20,000, more preferably 500 to 10,000, and most preferably 1,000 to 8,000. . If it is less than 200, the effect of improving the withstand voltage is small, and if it exceeds 20,000, the low temperature characteristics are inferior.

As a method for producing an alkylene oxide adduct (A) of a trivalent to hexavalent polyhydric alcohol (a), the polyhydric alcohol is first reacted with ethylene oxide in the presence of potassium hydroxide or sodium hydroxide catalyst to block. Add. After completion of the reaction, a general method is a method in which a mixture in which ethylene oxide and propylene oxide are made uniform in advance in a cylinder is dropped and added randomly.
In the aluminum electrolytic capacitor application which is the present application, since metal ions cause a short circuit of the capacitor, potassium ions or sodium ions need to be reduced to 10 ppm or less, preferably 1 ppm or less by 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 electrolytic capacitors. The electrolyte (B) is composed of a cation component (B1) and an anion component (B2). .

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

The anion component (B2) is a monocarboxylic acid anion such as 2-ethylhexanoic acid or 2-butylhexanoic acid; adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 1, Examples thereof include dicarboxylic acid anions such as 10-decanedicarboxylic acid, maleic acid, phthalic acid and citraconic acid; phosphate anions such as phosphate anions and phosphate esters; borate anions and borate derivative anions. Among these, a dicarboxylic acid 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, alcohol (C1), amide (C2), lactone (C3), nitrile (C4) , Sulfone (C5) and other polar organic solvents (C6).

Alcohol (C1)
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 (such as glycerin), tetrahydric or higher alcohol (such as hexitol)

Amide (C2)
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.

Lactone (C3)
γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, γ-valerolactone, δ-valerolactone, and the like.

Nitrile (C4)
Acetonitrile, propionitrile, butyronitrile, acrylonitrile, methacrylonitrile, benzonitrile, etc.

Sulfone (C5)
Sulfolane, dimethyl sulfoxide, ethyl methyl sulfone and the like.

Other organic solvents (C6)
1,3-dimethyl-2-imidazolidinone and the like.

    These polar solvents (C) may be used alone or in combination of two or more. Among these, alcohol (C1) and lactone (C3) 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 preferably 2/98 to 40/60, and preferably 2/98 to 20/80. Further preferred.
When the weight ratio (A) / (C) is less than 2/98, the effect of improving the withstand voltage is lowered. On the other hand, when it exceeds 40/60, the viscosity is increased. 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, poval, etc. are 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
1.1 parts by weight (0.02 mol) of potassium hydroxide is added to 182 parts by weight (1 mol) of hexitol sorbitol (a-1), and 616 parts by weight (14 mol) of ethylene oxide is reached at 170 ° C. until pressure equilibrium is reached. Reacted. Thereafter, a solution in which 572 parts by weight (13 mol) of ethylene oxide and 354 parts by weight (6 mol) of propylene oxide were made uniform in a cylinder was reacted in advance, and the end point was reached when pressure equilibrium was 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.
The sampled product and the final product proton nuclear magnetic resonance apparatus (H-NMR) chart and hydroxyl value at the end of the first stage reaction, k = 14, m = 13, n = 6 in the chemical formula (1), It was confirmed that an alkylene oxide adduct (A-1) of f = 6, A = hydrogen atom, and R = sorbitol residue was obtained.

Production Example 2
In Production Example 1, the first ethylene oxide was changed to 704 parts by weight (16 mol) of ethylene oxide, and the second stage ethylene oxide and propylene oxide were changed to 4,268 parts by weight (97 mol) of ethylene oxide and 2,360 parts by weight of propylene oxide. (40 mol) was reacted in the same manner as in Production Example 1 except that the liquid was made uniform in a cylinder, and k = 16, m = 97, n = 40, f = 6, A = hydrogen atom in chemical formula (1) , R = alkylene oxide adduct (A-2) of sorbitol residue was obtained.

Production Example 3
In Production Example 1, sorbitol was changed to glycerin (a-2) of a trivalent alcohol, and 572 parts by weight (13 mol) of ethylene oxide and 767 parts by weight (13 mol) of propylene oxide were added to ethylene oxide and propylene oxide in the second stage. The reaction was conducted in the same manner as in Production Example 1 except that the liquid was made uniform in a cylinder, and k = 14, m = 13, n = 13, f = 3, A = hydrogen atom, R = glycerin in chemical formula (1). An alkylene oxide adduct (A-3) of the residue was obtained.

Production Example 4
In Production Example 1, sorbitol was changed to glycerin to make 704 parts by weight (16 mol) of the first ethylene oxide, 2,200 parts by weight (50 mol) of ethylene oxide and 472 parts by weight of ethylene oxide and propylene oxide in the second stage. (8 mol) was reacted in the same manner as in Production Example 1 except that the solution was made uniform in a cylinder, and k = 16, m = 50, n = 8, f = 3, A = hydrogen atom in chemical formula (1) , R = alkylene oxide adduct (A-4) of glycerin residue was obtained.

Comparative production example 1
1.1 parts by weight (0.02 mol) of potassium hydroxide was added to 182 parts by weight (1 mol) of glycerin (a-1), and 616 parts by weight (14 mol) of ethylene oxide and 767 parts by weight (13 mol) of propylene oxide were added at 170 ° C. The liquid made uniform in the cylinder was dropped and reacted until pressure equilibrium was 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. Sampling was performed a plurality of times during the reaction, and 14 mol of ethylene oxide / 13 mol of propylene oxide (A-2 ′) was obtained from the H-NMR chart and hydroxyl value of the final product. The additional format was random. This does not correspond to chemical formula (1).

Comparative production example 2
In Production Example 1, sorbitol is changed to glycerin, 826 parts by weight (14 mol) of propylene oxide is first added instead of addition of ethylene oxide, and 572 parts by weight (13 mol) of ethylene oxide and propylene oxide are added to the second stage of ethylene oxide and propylene oxide. The reaction was carried out in the same manner as in Production Example 1 except that 354 parts by weight (6 mol) was made uniform in a cylinder to obtain PO14 mol addition of glycerin-EO13 mol / PO6 mol addition product (A′-3). . This does not correspond to chemical formula (1).

Comparative production example 3
In Production Example 1, the second-stage ethylene oxide and propylene oxide were changed to propylene oxide parts by weight 767 (13 mol) and reacted until pressure equilibrium was reached. In addition, as the third stage, 572 parts by weight of ethylene oxide (13 mol) Was reacted in the same manner as in Production Example 1 except that the reaction mixture was reacted until pressure equilibrium was reached, to obtain an EO14 mol addition-EO13 mol-PO13 mol addition product (A′-4) of glycerin. This does not correspond to chemical formula (1).

Example 1
(A-1) and the polar solvent ethylene glycol (C-1) were mixed in the number of parts (parts by weight) shown in Table 1. Thereafter, 8 parts by weight of 1,6-decanedicarboxylic acid (B2-1) was added to 91 parts by weight of this solution, and 1 part by weight of ammonia gas (B1-1) was blown and dissolved while neutralization. An electrolytic solution was obtained. 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 (−20 ° C.) state was visually observed by the method shown below, and the results of measuring the conductivity are shown in Table 1. Described.

[State of electrolyte at −20 ° C.]
The electrolytic solution was put in a transparent glass bottle, left in a -20 ° C. constant temperature bath for 24 hours, tilted at −20 ° 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: Whole solidified

[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.).
Under this condition, the conductivity is required to be 1.2 mS / cm or more.

[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.
Under these conditions, a 500V-compatible capacitor generally requires a withstand voltage of 520V or more.

The electrolyte solutions of Examples 1 to 4 of the present invention were transparent at -20 ° C., had no deposits and were fluid, and had high conductivity and withstand voltage.
On the other hand, Comparative Example 1 using a divalent alcohol alkylene oxide adduct and Comparative Example 2 using an m-zero alcohol alkylene oxide adduct solidified at -20 ° C. First, the withstand voltage was insufficient in Comparative Example 3 in which propylene oxide was added instead of ethylene oxide. Further, in Comparative Example 4 in which ethylene oxide and propylene oxide were not random adducts, the electrolyte solution was slightly cloudy at −20 ° C. and the withstand voltage was insufficient.

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 trivalent to hexavalent polyhydric alcohol (a) are essential components, and the alkylene oxide adduct (A) is represented by the following general formula (1). An electrolytic solution for electrolytic capacitors, characterized by being expressed.
[K represents the number of added moles of ethylene oxide, and is independently a number of 1 to 70. m represents the number of added moles of ethylene oxide, and is independently a number of 1 to 150. n represents the number of added moles of propylene oxide, and is independently a number from 1 to 150. f represents the valence of the polyhydric alcohol (a) and is an integer of 3-6. R represents a residue obtained by removing a hydroxyl group from an f-valent alcohol. A represents a hydrogen atom, an alkyl group, or an allyl group. “/” Indicates that the addition form of ethylene oxide and propylene oxide is random. ] The electrolytic solution for an electrolytic capacitor according to claim 1, wherein k in the general formula (1) is a number from 10 to 30. The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, wherein the total number of moles of ethylene oxide in the alkylene oxide adduct (A) is 12 to 60. The number average molecular weight of (A) is 1,000-8,000, The electrolyte solution for electrolytic capacitors in any one of Claims 1-3. The electrolytic capacitor using the electrolyte solution for electrolytic capacitors in any one of Claims 1-4.