JP2774525B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for preparing a mono- or di-N, N-dialkyltetrahydrooxazinium compound salt of an aliphatic saturated dicarboxylic acid in a solvent mainly composed of an aprotic solvent. The present invention relates to an electrolytic solution for an electrolytic capacitor contained as an electrolyte.

(Conventional technology) Electrolytic capacitors use a valve metal with an insulating oxide film formed on the surface such as aluminum or tantalum for the anode electrode, use a basic oxide film layer as a dielectric, and apply a capacitor to the surface of this oxide film layer. It is configured such that an electrolytic solution serving as an electrolyte layer is brought into contact with the battery, and an electrode for current collection usually called a cathode is arranged.

As described above, the electrolytic solution for the electrolytic capacitor directly contacts the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer of the electrolytic capacitor and the collector cathode, and the resistance of the electrolytic solution is inserted in series with the electrolytic capacitor. Therefore, the characteristic is a major factor affecting the characteristics of the electrolytic capacitor. For example, when the conductivity of the electrolytic solution is low, there is a disadvantage that the equivalent series resistance inside the electrolytic capacitor is increased and the high-frequency characteristics and the loss characteristics are deteriorated. From such a background, an electrolyte having a high conductivity is required, and as a conventionally known high conductivity electrolyte, an organic acid such as adipic acid or a salt thereof is dissolved in a glycol or an alcohol such as ethylene glycol. Things are used mainstream for normal use.

(Problems to be Solved by the Invention) With the recent increase in the range of use of electronic devices, demands for improving and improving the performance of electrolytic capacitors have increased, and the conductivity of current electrolytic solutions cannot be said to be sufficient. In particular, in the case of the current electrolytic solution, when the desired electric conductivity cannot be obtained, or when using an electrolyte having low solubility, it is attempted to intentionally add water to improve the electric conductivity. .

However, recently, in the use situation of electrolytic capacitors that require long-term use at high temperature exceeding conventional products, the presence of moisture in the electrolyte causes deterioration of the dielectric film layer and internal vapor of the electrolytic capacitor. When the pressure is increased, the sealing portion is damaged and the life of the electrolyte is deteriorated due to evaporation of the electrolytic solution, and there is a disadvantage that stable characteristics cannot be maintained for a long period of time.

Therefore, an object of the present invention is to provide a substantially non-aqueous, high-conductivity electrolytic solution mainly composed of an aprotic solvent, thereby improving the electric characteristics of an electrolytic capacitor and extending the stable characteristics. It is to improve the reliability of the electrolytic capacitor by maintaining the period.

(Means for Solving the Problems) The inventors of the present invention have conducted intensive studies on a substantially non-aqueous electrolytic solution mainly composed of an aprotic solvent and an electrolyte which provides high conductivity, and as a result, the aliphatic saturated dicarboxylic acid It has been found that an acid mono- or di-N, N-dialkyltetrahydrooxazinium compound salt has high solubility in an aprotic solvent, and has a high degree of dissociation and a high conductivity, and has reached the present invention. .

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has a general formula: (Wherein, m + n = 4, m = 2-4, n = 2-0, R ₁ and R ₂ may be the same or different alkyl groups having 1 to 6 carbon atoms,
R ₃ and R ₄ may be the same or different hydrogen atoms, alkoxy groups having 1 to 6 carbon atoms, or alkyl groups having 1 to 6 carbon atoms, R is an alkylene group having 1 to 20 carbon atoms, and X is A mono- or di-N, N-dialkyltetrahydrooxazinium compound salt of an aliphatic saturated dicarboxylic acid compound represented by a hydrogen atom or the same group as an N, N-dialkyltetrahydrooxazinium compound group represented by the formula It is characterized by containing as.

Examples of aprotic solvents used include: (1) N-methylformamide, N, N
-Dimethylformamide, N-ethylformamide, N,
N-diethylformamide, N-methylacetamide,
N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoramide, (2) dimethyl sulfoxide as an oxide type, (3) acetonitrile as a nitrile type, (4) cyclic ester, an amide type Representative examples include γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, and propylene carbonate.

The polyhydric alcohol compound targeted by the present invention is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound, the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol monoalkyl ether compound is methylcellosolve or It is an ethyl cellosolve.

The weight ratio of the polyhydric alcohol compound to the aprotic solvent is (100-50) :( 0-50), and 100% of the aprotic solvent is appropriate, but up to about 50% of the polyhydric alcohol compound is substantially It is possible to avoid deterioration of the product and use it as appropriate.

The aliphatic saturated dicarboxylic acid compound which is the object of the present invention is malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, cornic acid, azelaic acid, sebacic acid, undecandioic acid, dodecadioic acid, brassic acid, tetradecane Acids, pentadecandioic acid, tapsic acid, heptadecandioic acid, octadecandioic acid, nonadecandioic acid, eicosantioic acid, henicoisodioic acid, docosantioic acid, etc., but are not limited thereto.

The N, N-dialkyltetrahydrooxazinium compound that is the object of the present invention is represented by the following structural formula.

The tetrahydrooxazine compound used as a raw material for synthesizing the N, N-dialkyltetrahydrooxazinium compound used in the present invention is, for example, tetrahydro-1,4-oxazine (morpholine), which is industrially produced by dehydration and ring closure of diethanolamine with sulfuric acid or the like. Manufactured and available on the market,
This can be N-methylated with an alkyl halide, such as methyl iodide, by a conventional method to obtain the corresponding N, N-dimethylmorpholinium iodide. This is subjected to electrodialysis using an ion-exchange membrane and desalted with deiodine for anion exchange to obtain a purified aqueous solution of N, N-dimethylmorpholinium hydroxide suitable for use in the electrolytic capacitor of the present invention. obtain. Equimolar or 1/2 mole of the desired aliphatic saturated dicarboxylic acid compound is added to this aqueous solution, neutralized, and evaporated to dryness under reduced pressure to obtain a mono- or di- aliphatic saturated dicarboxylic acid.
N, N-dimethylmorpholinium salt can be obtained.
Also, 1,3-oxazine or 1,2-oxazine is, for example,
H. King: Journal Chemical Society 1942
Year, can be appropriately synthesized by the method described on page 432, for example,
1,2-Oxazine can be synthesized from ethyl hydroxamate and 1,4-dibromobutane as follows: The electrolytic solution for the electrolytic capacitor according to the present invention is generally,
A desired aliphatic saturated dicarboxylic acid mono- or di-N, N-dialkyltetrahydrooxazinium compound salt is added and dissolved in a solvent obtained by mixing a polyhydric alcohol compound or a monoalkyl ether compound thereof as necessary with an aprotic solvent, and then dissolving it. Can be

(Examples) Hereinafter, examples of the electrolytic solution for electrolytic capacitors according to the present invention will be described with reference to mono- or di-N, N-
The conductivity of a 20% by weight solution of a dialkyltetrahydrooxazinium compound salt in various aprotic solvents or ethylene glycol or methylcellosolve (ethylene glycol monomethyl ether) at 30 ° C.
It is shown in the table. As a comparative example, a conventional standard electrolyte (78% by weight of ethylene glycol, 10% of water, and 12% of diammonium adipate) is shown.

As can be seen from the above results, the electrolytic solution of the present invention has higher conductivity than the conventional one.

Next, electrolytic capacitors were manufactured using the electrolytic solutions of Examples 1 to 10 and Comparative Example, and their characteristics were compared.

The manufactured electrolytic capacitor was formed by using an aluminum foil as an anode and a cathode, and overlapping and winding a separator paper therebetween to form a cylindrical capacitor element, and impregnating the electrolytic solution of each of the examples and comparative examples. It is housed in an outer case and sealed.

All use the same capacitor element and rated voltage
The 16V rated capacity is 180 μF.

Table 2 shows the initial values of these electrolytic capacitors as well as 110
Capacitance value (μF), tangent of loss angle (tan δ), leakage current (μA) after 1000 hours from application of rated voltage at ℃
(Binary value).

As is clear from the results of this test, since the conductivity of the electrolytic solution of the present invention is high, the loss compared to the conventional one, that is,
The value of tan δ decreases.

In addition, since it does not essentially contain water, even under a high temperature load state, there is no appearance abnormality or decrease in capacitance due to an increase in internal pressure, and even when comparing the initial value and the characteristic value after 1000 hours, the present invention Changes very little.

(Effect of the Invention) The electrolytic capacitor using the electrolytic solution according to the present invention can maintain a low loss value and stable characteristics even when used for a long time at a high temperature. It can be used for power supply devices such as switching regulators, and various electric devices that are used at high temperatures for a long period of time.

Claims (6)

(57) [Claims] [1] A solvent comprising an aprotic solvent as a main component and a general formula: (Where m + n = 4, m = 2-4, n = 2-0, R ₁ , R ₂
Are the same or different alkyl groups each having 1 to 6 carbon atoms, R ₃ and R ₄ each may be the same or different hydrogen atom, alkoxy group having 1 to 6 carbon atoms, or 1 to 6 carbon atoms. An alkyl group, R is an alkylene group having 1 to 20 carbon atoms,
X represents a hydrogen atom or the same group as the N, N-dialkyltetrahydrooxazinium compound group shown in the formula;
-Dialkyltetrahydrooxazinium compound is N, N
-Diethylmorpholinium, N, N-diethyltetrahydro-1,2-oxazinium, N, N-dimethyl-2-methoxymorpholinium, N, N-dimethyl-2,5-dimethylmorpholinium, or N, An electrolytic solution for an electrolytic capacitor comprising, as an electrolyte, a mono- or di-N, N-dialkyltetrahydrooxazinium compound salt of an aliphatic saturated dicarboxylic acid compound of N-dimethyltetrahydro-1,3-oxazinium). 2. A solvent mainly comprising an aprotic solvent comprises 100 to 50 parts by weight of an aprotic solvent and 0 to 50 parts of a polyhydric alcohol compound.
2. The electrolytic solution for an electrolytic capacitor according to claim 1, comprising: parts by weight. 3. An aprotic solvent comprising N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, The electrolysis according to claim 1 or 2, wherein the electrolysis is selected from the group consisting of N, N-diethylacetamide, γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl sulfoxide, acetonitrile, and a mixture thereof. Electrolyte for capacitors. 4. The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the polyhydric alcohol compound is a dihydric alcohol compound or a monoalkyl ether of the dihydric alcohol compound. 5. The electrolytic solution for an electrolytic capacitor according to claim 4, wherein the dihydric alcohol compound is ethylene glycol and the dihydric alcohol monoalkyl ether compound is methylcellosolve or ethylcellosolve. 6. The compound according to claim 1, wherein the aliphatic saturated dicarboxylic acid compound is succinic acid, glutaric acid, adipic acid or cornic acid.
The electrolytic solution for an electrolytic capacitor according to the above.