JPH0493011A - Electrolytic capacitor electrolyte - Google Patents

Abstract

PURPOSE:To realize high-withstand voltage with high conductivity through improvement in the withstand voltage of electrolyte by adding a specific phosphoric ester into an electrolyte whose main solvent is an organic polarity solvent and whose solute is an organic acid or inorganic acid or its salt. CONSTITUTION:The organic polarity solvent of an electrolytic capacitor electrolyte is a single or arbitrary mixed solvent of pront polarity solvent or a nonpront polarity solvent: mixing 100 weight parts of these solvents with water by about 0-20 weight parts decreases conductivity and further improves forming property. 1-30 weight parts of an organic acid or inorganic acid or its salt which serves as the solute are dissolved in such a solvent system. An electrolyte consisting of such a solute-solvent system is added with 0.5-20 weight parts, further preferably 3-10 weight parts, of a phosphoric ester where X is hydrogen or methyl group (i) is an integer of 1 or more, n1 is an integer of 1 or more, and RiO is the monoacrylate of an ethylene oxide or propylene oxide.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to improvement of an electrolytic solution for electrolytic capacitors, and more specifically, by adding specific additives, the withstand voltage of the electrolytic solution is improved, This invention relates to improvements in electrolytic solutions for electrolytic capacitors that can realize electrolytic solutions with high electrical conductivity and high withstand voltage.

[Prior art] Electrolytic capacitors are small, large capacity, inexpensive, and exhibit excellent characteristics such as smoothing rectified output, and are one of the important components of various electrical and electronic devices. It is produced by using an aluminum film that has been oxidized to an oxide film as an anode, and using this oxide film as a dielectric with an electrolyte interposed between it and a current collecting cathode. During use, it is stable because the oxide film is constantly regenerated, but if it is not used for a long time, for example, regeneration becomes insufficient and it deteriorates.

Since electrolytic capacitors are used while undergoing chemical reactions, their characteristics greatly depend on the properties of the electrolyte. Maintaining a steady state of the chemical reaction that occurs between the aluminum electrode, which has an oxide film on its surface, and the electrolyte, and maintaining the aluminum oxide film that serves as a dielectric well, is important for stabilizing performance and If the chemical steady state is disturbed due to an incorrect method, for example, due to an excessively high voltage load, the aluminum oxide film will be destroyed and eventually the insulation will be destroyed.

Scintillation is a phenomenon in which the electrochemical state fluctuates as a result of a change in the physical properties of the dielectric due to the high voltage load that occurs when the load voltage of the capacitor increases, resulting in a temporal change in dielectric constant.The voltage at which this phenomenon is observed is The scintillation voltage (spark voltage) can be used as a measure of the voltage resistance of the capacitor, and the higher the scintillation voltage (spark voltage), the greater the voltage resistance of the capacitor.

This can be easily done by immersing an unformed aluminum foil of an appropriate size in the electrolyte to be measured, without assembling the final capacitor product.

In conventional electrolytic solutions for general electrolytic capacitors, # such as boric acid or salts thereof are added to the electrolytic solution as a main solute in order to obtain high voltage resistance. In addition to these, attempts have been made to improve the electrolytic solution for electrolytic capacitors and obtain high voltage resistance by adding various additives.

Examples of additives for obtaining high voltage resistance include the addition of sulfamic acid (Japanese Patent Publication No. 4982963), the addition of superric acid (Japanese Patent Publication No. 49133860), and the addition of dodecyl phosphate (Japanese Patent Publication No. 49-73659). ), addition of alkyl phosphoric acid (JP-A-52-153154), addition of diphosphorous acid (JP-A-57-141913), use of boric acid-mannilla 1~ system (JP-A-57-60829) However, it has not been possible to sufficiently improve the withstand voltage while maintaining high conductivity.

[Problems to be Solved by the Invention] The present invention provides an electrolytic solution for electrolytic capacitors that can improve the dielectric strength of the electrolytic solution by adding specific additives and achieve high dielectric strength with high conductivity. The purpose is to

[Means for Solving the Problems] According to the present invention, a dihydrogen phosphate polyamide having the following general formula is added to an electrolytic solution containing an organic polar solvent as a main solvent and an organic acid or an inorganic acid or a salt thereof as a solute. Oxyethylene polypropylene monomethacrylate (or monoacrylate-1
An electrolytic solution for electrolytic capacitors characterized by the addition of phosphoric acid esters: CHCO(RiO)n+ P OHX 0
0H (wherein, X is hydrogen or a methyl group, i is an integer of 1 or more, n is an integer of 1 or more, and RiO is ethylene oxide or propylene oxide, and at least 1 [including any one of the above] is provided.

Specific examples of solvents that can be used alone or in combination as the organic polar solvent of the electrolyte include the following: Protic polar solvents ethanol, propatool, butanol, pentanol, hexanol, cyclobutanol, Monohydric alcohols such as cyclopentanol, cyclohexanol, and benzyl alcohol, ethylene glycol, propylene glycol, glycerin, methoxyethanol, 1-oxyethanol, methoxypropylene glycol, di-1-xypropatol, methyl cellosolve, and ethyl cellosolve. Polyhydric alcohols and alcohol ethers such as 1=protic polar solvent N-methylformamide, N,N-dimethylpolamide, N-ethylformamide, N,N-diethylpolamide, N-methylacetamide, j (, todimedylacetamide, toethylacetamide, N, N-
amide solvents such as diethyl acetamide and hexamethylphosphoric amide; Cyclic amide solvents, nitrile solvents such as ace)-21-lyl, and oxide solvents such as dimethyl sulfoxide.

Specific examples of electrolytes that can be used alone or in combination in the electrolyte of organic acids, inorganic acids, or salts thereof include the following: Organic acids formic acid, acetic acid, propionic acid, enane 1- Aliphatic monocarphonic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, pimelic acid, superic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, citraconic acid, itaconic acid, etc. aliphatic dicarboxylic acids, benzoic acid, phthalic acid, salicylic acid, 1-ruyl acid, and aromatic carboxylic acids such as pyromellitic acid, inorganic acids boric acid, phosphoric acid, silicic acid, HB F 4.1-IP
Inorganic acids such as F6, ammonium ammonium (NH41, methylammonium, ethylammonium, and monoalkylammonium such as globylammonium), dialkylammonium such as dimethylammonium, diethylammonium, ethylmethylammonium, and dibutylammonium, 1-dimethyl Trialkylammonium such as ammonium, 1-ethylammonium, and 1-libdellammonium, tetraethylammonium, 1-ethylmethylammonium, 1-butylammonium, tetraethylammonium, and N,N-dimethylpyrrolidinium, etc. Quaternary ammoniums, such as phosphoniums and arsoniums, can also be used.

The organic polar solvent of the electrolytic solution for an electrolytic capacitor according to the present invention can be the above-mentioned protic polar solvent or aprotic polar solvent alone or any mixed solvent. O~2 depending
By mixing about 0 parts by weight of water, it is possible to reduce the electrical conductivity and further improve the chemical conversion property (oxidized film forming property). In such a solvent system, it is preferable that the solute organic or inorganic acid or its salt be dissolved at a dissolution level of 1 to 30 parts by weight.

For an electrolytic solution consisting of such a solute-solvent system, preferably the above-mentioned dihydrogen phosphate polyoxyethylene polypropylene monomethacrylate-1 (or monoacrylate-1
~) By adding 0.5 to 20 parts by weight, more preferably 3 to 10 parts by weight, of a phosphoric acid ester, the withstand voltage of the electrolytic solution is improved, and an electrolytic solution that can realize high withstand voltage with high conductivity is obtained. It is possible to obtain electrolyte for capacitors.

[Function] Dihydrogen phosphate polyoxyethylene polypropylene monomethacrylate (or monoacrylate), which is a unique additive added to the electrolytic solution for electrolytic capacitors disclosed in the present invention,
The mechanism of action of the phosphoric acid esters 1 to 1-) in the electrolytic solution for electrolytic capacitors is not clear. However, the electrolytic solution for an electrolytic capacitor according to the present invention does not contribute in some way to stabilizing the chemical steady state of the electrochemical reaction system consisting of the anode, cathode, aluminum oxide film dielectric, and electrolyte of the electrolytic capacitor. It is estimated that there are.

As mentioned above, since electrolytic capacitors are used because they undergo chemical reactions, their characteristics greatly depend on the properties of the electrolyte. It is important to maintain a steady state of the chemical reaction that occurs between the aluminum electrode, which has an oxide film on its surface, and the electrolyte, and to maintain the aluminum oxide film, which serves as a dielectric, well in order to stabilize the performance.

The present invention has developed an electrolytic capacitor that is an electrochemical reaction system by adding a phosphate ester called dihydrogen phosphate polyoxyethylene polypropylene monomethacrylate-1 (or monoacrylate), which is a unique additive. It is presumed that the entire structure is stabilized and good capacitor characteristics are provided.

[Effects of the Invention] According to the present invention, the dihydrogen phosphate polyoxyethylene polypropylene monomethacrylate (or monoacrylate) phosphate ester, which is a unique additive, is added to improve the dielectric strength of the electrolyte. , an electrolytic solution for electrolytic capacitors that can realize high conductivity and high withstand voltage is provided.

[Example] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples.

In the following examples, the phosphoric acid esters used in the present invention were shown by the following symbols: A dihydrogen diphosphate polyoxypropylene monomethacrylate (n=6) B polyoxyethylene mono dihydrogen diphosphate methacrylate
1-(n=5) C dihydrogen dihydrogen polyoxyethylene polyoxypropylene monomethacrylate-1~ (n+-7, n2=3) D=dihydrogen dihydrogen polyoxyethylene monoacrylate-1
~(n=9).

Example 1 and Comparative Example 1 Electrolytic capacitors were manufactured by a conventional method using an electrolytic solution for electrolytic capacitors having the following common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration.

Ethylene glycol 80 parts by weight Water 7 Methyl cellosolve 20 ■ Ammonium adipate 20 Adipic acid 3 Type and amount of phosphoric acid ester (phosmer) added, conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor The following is shown.

Addition amount Electrical conductivity Withstand voltage (parts by weight) (ms/cm) (V) Example 1
^(6) 3.69 395 Comparative Example 1
An electrolytic capacitor was produced by a conventional method using an electrolyte solution for a 4.95 150 capacitor and adding the phosphoric acid ester according to the present invention at a predetermined concentration.

■ Ethylene glycol 100 Tartanbu water
5 Raku 2 Ammonium Benzoate 15 The type and amount of the added phosphoric acid ester (phosmer), the electrical conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor are shown below.

Addition amount Electrical conductivity Withstand voltage (parts by weight) (mS/cm) (V) Example 2
B(6) 3.33 350 Comparative Example 2
- 4.44 250 Example 3 and Comparative Example 3 Electrolytic capacitors were fabricated by a conventional method using an electrolytic solution for electrolytic capacitors having the following common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration. .

Mixed ethylene glycol 100 parts by weight water
7. Ammonium sebacate 17 The type and amount of the added phosphate ester (posmer), the electrical conductivity and withstand voltage at 30° C. of the obtained electrolytic capacitor are shown below.

Addition amount Conductivity Withstand voltage (parts by weight >(l'ns/c+n) (V) Example 3 ^(6) 2.96 380 Comparative example 3
- 4.59 350 Example 4 and Comparative Example 4 Using an electrolytic solution for electrolytic capacitors having the following common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration, and producing electrolytic capacitors by a conventional method. Na.

Shinbuki γ-butyrolactone 60 parts by weight Methyl cellosolve 15 Ethylene glycol 10 ■ Monotetramethylammonium phthalate
15 Boric acid 2 Mannitol 2 The type and amount of the added phosphoric acid ester (phosmer), the electrical conductivity and withstand voltage at 30° C. of the obtained electrolytic capacitor are shown below.

Addition amount Conductivity Withstand voltage (parts by weight) (IIIS/cl'N) (■) Example 4
C(4) 6.80 110 Comparative Example 4 -
8.62 85 However, Example 5 and Proportional Example 5 Electrolytic capacitors were manufactured by a conventional method using an electrolytic solution for an electrolytic capacitor having the following common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration.

■ γ-Butyrolactone 60 parts by weight Methyl cellosolve 15 Ethylene glycol 10 ■ Trimethylisopropylammonium malate
15 Boric acid 2 Mannilla 1-2 The type and amount of the added phosphoric acid ester (phosmer), the electrical conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor are shown below.

Addition amount Conductivity Withstand voltage (parts by weight) (ms/c+n) (V) Example 5
B(4) 5.39 150 Comparative Example 5-7.
00 105 Application J6 and Proportional Example 6 An electrolytic capacitor was prepared by a conventional method using an electrolytic solution for an electrolytic capacitor consisting of the following components as a common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration.

Chibuki gamma-butyrolactone 60 parts by weight Ethylene glycol 20 fat l Monotriethylammonium maleate
20 Boric acid 2 Mannilla 1-2 The type and amount of the added phosphoric acid ester (posmer), the electrical conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor are shown below.

Addition amount Electrical conductivity Withstand voltage (parts by weight) (ns/cn) (V) Example 6
D(4) 5.89 205 Comparative Example 6-7
．． 81 100 Example 7 and Proportional Example 7 Electrolytic capacitors were manufactured by a conventional method using an electrolytic solution for electrolytic capacitors having the following common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration.

Direct N,N-dimethylformamide
60 fflfl part ethylene glycol 20 M monotriethylammonium maleate
The type and amount of the phosphoric acid ester (phosmer) added, the electrical conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor are shown below.

Addition amount Electrical conductivity Withstand voltage (parts by weight) (n37cm) (V) Example 7
C(3) 10.5 155 Comparative Example 7 -
13.3 75 Example 8 and Comparative Example 8 An electrolytic capacitor was manufactured by a conventional method using an electrolytic solution for an electrolytic capacitor consisting of the following components as a common composition, adding the phosphoric acid ester according to the present invention at a predetermined concentration. .

Direct board N, 1(-dimethylformamyl'
65 ffi quantity department ethylene glycol 2
0 ■ Rest Wil + Limethylisoprobyl ammonium
15 The type and amount of the added phosphoric acid ester (phosmer), the electrical strength and voltage at 30° C. of the obtained electrolytic capacitor are shown below.

Addition amount Conductivity Withstand voltage (parts by weight) (n37cm) (V) Example 8
D(3) 8.78 155 Comparative Example 8
- 9.98 105 Examples 9 to 11 and Comparative Example 9 Using an electrolytic solution for electrolytic capacitors consisting of the following components as a common composition, adding the phosphate ester according to the present invention at a predetermined concentration, and forming an electrolytic capacitor by a conventional method. Don't make it.

Directly placed γ-butyrolactone 80 parts by weight Blood monotriethylammonium maleate
Polyoxyethylene monomethacrylate J-(n=5) dihydrogen phosphate was used as the 20 phosphate ester, and the amount added was varied to examine the dependence of electrical conductivity and withstand voltage on the amount added.

The amount of phosphoric acid ester (phosmer PE) added, the electrical conductivity and withstand voltage at 30°C of the obtained electrolytic capacitor are shown below.

Addition amount Electrical conductivity Withstand voltage (parts by weight) (ms/crn) (V) Example 9 2 13.0 155 Example 10 4
11.6 195 Example 11 6 1
0.6 225 Comparative Example 9 0 14.7
77 The scintillation curves of the pressure resistance of the electrolytic capacitors according to Examples 9 to 11 and Comparative Example 9 are shown in FIG.

From the above results, it can be seen that the addition of the phosphate ester according to the present invention improves the withstand voltage of the electrolytic solution, and provides an electrolytic solution for electrolytic capacitors that can realize high electrical conductivity and high withstand voltage.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing scintillation curves of withstand voltage of electrolytic capacitors according to the present invention (Examples 9 to 11) in comparison with scintillation curves of withstand voltage of a conventional electrolytic capacitor (Comparative Example 9).

Claims (1)

[Claims] (1) Add phosphorus dihydrogen phosphate polyoxyethylene polypropylene monomethacrylate (or monoacrylate) having the following general formula to an electrolytic solution containing an organic polar solvent as the main solvent and an organic acid or inorganic acid or its salt as the solute. Electrolyte for electrolytic capacitors characterized by the addition of acid esters: ▲Mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X is hydrogen or a methyl group, i is an integer of 1 or more,
n_1 is an integer of 1 or more, and R_iO is ethylene oxide or propylene oxide, and includes at least one of ethylene oxide and propylene oxide).