JP2695254B2 - Electrolyte for driving electrolytic capacitors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic solution for driving an electrolytic capacitor.

2. Description of the Related Art Conventionally, an ethylene glycol-boric acid-based electrolyte has been used as a medium- and high-pressure-grade electrolyte, but this type of electrolyte is 100% because water is generated by the esterification reaction of ethylene glycol and boric acid. Above ℃, the vapor pressure is high,
In addition, it was not suitable for use at high temperature because it easily reacts with aluminum as an electrode. To remedy these drawbacks,
As a solute, there is an electrolytic solution using azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, nonanedioic acid (JP-A-61-172323), 1,6-decanedicarboxylic acid, or a salt thereof.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the above-mentioned conventionally used carboxylic acids and salts thereof have insufficient solubility in a solvent such as ethylene glycol.

Further, although the conventional carboxylic acid can relatively increase the spark voltage, it is not sufficient, and when these carboxylic acids or salts thereof are used alone as solute, the rated voltage is 350V.

Further, when the electrolytic solution was allowed to stand at a high temperature, the conventional carboxylic acid or its ammonium salt showed a large change at a high temperature such as causing an esterification reaction with ethylene glycol.

In order to improve the above-mentioned conventional drawbacks, the inventors of the present invention have proposed the second class and / or the second class in Japanese Patent Laid-Open No. 1-103821.
It was also found that the use of a salt of a polycarboxylic acid having a total of two or more tertiary carboxyl groups and a molecular weight of 260 or more results in an electrolytic solution having a high spark voltage and a small change in specific electric conductivity at high temperatures. . However, when applied to higher performance capacitors, the characteristics were not sufficient.

The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor, which enables a medium- and high-voltage class electrolytic capacitor to have a long life and high reliability.

Means for Solving the Problems The present inventors have arrived at the present invention as a result of earnest studies to find out an electrolytic solution having excellent stability at higher temperatures. That is, the electrolytic capacitor driving electrolytic solution of the present invention is a polycarboxylic acid having two or more secondary and / or tertiary carboxyl groups, which has an ether bond and no ester bond. A salt is used as a solute, and the polycarboxylic acid is represented by the general formula (1) or (2) O (-A-COOH) ₂ (1) R (-O-A-COOH) _n (2) (wherein A is a residue of a carboxylic acid having a secondary or tertiary carboxyl group and having no ester bond, the same or different, R is an organic residue having no ester bond, and n is an integer of 2 or more. Is used).

The molecular weight of the polycarboxylic acid is, for example, 160 to 5,0.
00 or more, usually 250 to 3,000, preferably 250
To 2,000, more preferably 350 to 1,500.

These polycarboxylic acids include, for example, oxycarboxylic acid (HO-A-COOH) and halogen-substituted carboxylic acid (X
-A-COOH, X represents a halogen atom) or a reaction with a polyhalide (R (-X) n), a carboxylic acid containing a halogen substituent and a polyol (R (-OH) m, m is an integer of n or more.). It can be obtained by a reaction with

In the case of an oxycarboxylic acid, the following are examples of the carboxylic acid of the residue of the carboxylic acid having a secondary or tertiary carboxyl group represented by A and having no ester bond.

1. Fatty acid oxycarboxylic acid For example, 2-hydroxyisobutyric acid, 2-hydroxy-
2-Methylbutyric acid, 2-ethyl-2-hydroxybutyric acid, hydroxypivalic acid.

2. Alicyclic oxycarboxylic acid For example, 1-hydroxy-1-cyclopropanecarboxylic acid, hexahydromandelic acid.

3. Aromatic oxycarboxylic acid For example, salicylic acid.

Further, examples of the carboxylic acid of the halogen-substituted group-containing carboxylic acid residue include a halogen-substituted product of the above-mentioned hydroxy group of oxycarboxylic acid, such as chloropivalic acid.

Examples of the organic residue containing no ester bond represented by R include a hydrocarbon group and a polyether group.
When R is a residue of a polyol, the following polyols are available.

1. Saturated and unsaturated aliphatic polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,12-dodecanediol, propylene glycol, 2-butyl-2-ethyl-1,3-propanediol, 2,3- or 2,4-butanediol, 1,
Linear and branched saturated aliphatic diols such as 5-hexanediol, 1,2-decanediol, and 1,2-dodecanediol.

Alternatively, 2-ethyl-2-hydroxymethyl-1,3-
Saturated aliphatic polyols such as prodiol, 1,2,3-heptanetriol, 1,1,1-tris (hydroxymethyl) ethane, pentaerythritol and 1,2,7,8-octane tetrol.

Alternatively, unsaturated aliphatic polyols such as 5-hexene-1,2-diol and 7-octene-1,2-diol.

2. Saturated and unsaturated alicyclic polyols, for example 1,3-cyclopentanediol, (methyl-) 1,2- or 1,3- or 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1 Saturated monocyclic alicyclic polyols such as 2,2-cycloheptanediol and 1,4- or 1,5-cyclooctanediol.

Or saturated polycyclic alicyclic polyols such as 1,5-decalindiol, hydrogenated bisphenol A, hydrogenated bisphenol B, and 4,8-bis (hydroxymethyl) tricyclo [5,2,10] decane.

Or 3-cyclohexene-1,1-dimethanol,
Unsaturated alicyclic polyols such as 3,5-cyclohexadiene-1,2-diol.

3. Aromatic polyol For example, resorcin, bisphenol A, bisphenol B, 2,2-bis (4-hydroxy-3-methylphenol) propane, bis (2- or 4-hydroxyphenyl) methane.

4. Polyalkylene glycol For example, polyethylene glycol, polypropylene glycol, polybutylene glycol, or a copolymer thereof having a molecular weight of 106 to 4,500 or more.

5. Sugars Monosaccharides such as glucose, galactose, mannose and fructose.

Alternatively, polysaccharides such as maltitol, lactose and sucrose.

6. Heterocyclic polyols For example, 2,5-furandimethanol and the like.

7. Polyol containing atoms other than carbon and oxygen in the main chain, for example, 2,2 ′-(decamethylenedithio) dimethanol, diethanolamine, triethanolamine, 2,
2'-bis (hydroxymethyl) -2,2 ', 2 "-nitriloethanol, 1,4-bis (2-hydroxyethyl) piperazine, tris (hydroxymethyl) aminomethane, tris (hydroxymethyl) phosphine oxide, Bisphenol S, etc.

8. Polymers and copolymers of monomers having a hydroxyl group For example, polyvinyl alcohol having a molecular weight of 90 to 4,500 or more.

For those polyols with a valence of 3 or higher,
It is not necessary for all hydroxyl groups to be subjected to ether bonds,
One or more hydroxyl groups may remain.

When R is a polyhalide residue, examples of the polyhalide include halogen-substituted products of the above hydroxyl groups of the polyol, such as dichloroethane and 1,6-dibromohexane.

It is preferable that all of these halogen groups of the polyhalide are consumed for the formation of ether bond and do not remain in the molecule after the reaction.

Deterioration at room temperature and high temperature occurs due to the reaction of the carboxyl group of carboxylic acid with the solvent such as causing esterification reaction. The present invention pays attention to this point, and the second grade and / or the third grade
A carboxylic acid having a graded carboxyl group was used. Second
It is considered that the primary and / or tertiary carboxyl groups are unlikely to cause an esterification reaction due to steric hindrance, and that a stable electrolytic solution can be obtained at high temperatures.

Further, by using a polycarboxylic acid having an ether bond but not an ester bond, an electrolytic solution having higher high temperature stability can be obtained.

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Table 1 shows examples of the present invention and conventional electrolytes, as well as their specific conductivities and spark voltages at room temperature.

As is clear from Table 1, in the present invention, the spark voltage can be increased without lowering the specific electric conductivity as compared with the conventional examples 1, 2, and 3.

FIG. 1 shows changes over time in the specific conductivity of the electrolytic solutions of Examples 1, 2, 3, 4 and Conventional Examples 2, 4 and 5 at 125 ° C. As is clear from FIG. 1, The present invention is
It can be seen that the change at high temperature is smaller than that of the conventional example, and the life can be extended at high temperature.

Table 2 shows Examples 1 to 4 and Conventional Examples 4 and 5 shown in Table 1.
Aluminum electrolytic capacitor (rated 400V,
It shows the characteristic change in the life test of 220 μF) at 125 ° C. In addition, in the conventional examples 1 to 3, the voltage of 400 V could not be applied.

As is clear from Table 2, the capacitors using Examples 1 to 4 have smaller changes in capacitance and tangent change of loss angle than those of Conventional Examples 4 and 5, and have excellent reliability with excellent life characteristics. A high capacitor can be obtained.

EFFECTS OF THE INVENTION As described above, according to the present invention, the spark voltage is high and the change at high temperature is small compared to the conventional electrolytic solution, and further, the life and reliability of the medium and high voltage class electrolytic capacitor are increased. It is possible to commercialize and has great industrial value.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing changes over time in specific electric conductivity of an electrolytic solution according to an example of the present invention at 125 ° C. in comparison with a conventional electrolytic solution.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Shimamoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Keiji Mori, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Kazushio Shiono 1 1-11, Hitotino-honcho, Higashiyama-ku, Kyoto Prefecture Sanyo Kasei Co., Ltd. (72) Inventor Takaaki 1 1-11, Hitotino-honcho, Higashiyama-ku, Kyoto Prefecture Kyoto Co., Ltd. (56) Reference JP-A-2-18919 (JP, A)

Claims (1)

(57) [Claims] 1. A polycarboxylic acid having two or more secondary and / or tertiary carboxyl groups which has an ether bond and does not have an ester bond is used as a solute. As said polycarboxylic acid, it is general formula (1) or (2) O (-A-COOH) ₂ (1) R (-OA-COOH) _n (2) (In formula, A is a secondary | 2nd-class or secondary | 1st-class. Residues of carboxylic acids having a tertiary carboxyl group and having no ester bond, which are the same or different, R is an organic residue having no ester bond, and n is an integer of 2 or more.). Electrolyte for driving an electrolytic capacitor using a liquid electrolyte.