JPH0291910A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve the electric characteristic of an electrolytic capacitor and lengthen the lifetime thereof by adding an electrolyte of a specific compound salt to a solvent the principal ingredient of which is an aprotic solvent. CONSTITUTION:An electrolyte of a mono/di-N,N-dialkyltetrahydrooxazinium compound salt of an aliphatic unsaturated dicarboxylic acid compound shown by a general formula is added to a solvent the principal ingredient of which is an aprotic solvent. In the general formula, m+n is 4, m is 2-4, n is 2-0, R1 and R2 are alkyl radicals of one to six carbon atoms, R3 and R4 are alkoxy or alkyl radicals of one to six hydrogen and carbon atoms, R is an alkenylene radical of one to ten carbon atoms, and X is a hydrogen atom or the same radical as an N,N-dialkyltetrahydrooxazinium compound radical in the formula. This compound salt has high solubility in and high degree of dissociation from the solvent; therefore, the electric characteristic of an electrolytic capacitor improves to lengthen the lifetime thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the preparation of mono- or di-N,N-dialkitetrahydroxazinium compound salts of aliphatic unsaturated dicarboxylic acids in a solvent mainly consisting of an aprotic solvent. The present invention relates to an electrolytic solution for an electrolytic capacitor containing as an electrolyte.

(Prior art) An electrolytic capacitor uses a valve metal such as aluminum or tantalum on the surface of which an insulating oxide film is formed as an anode electrode, the oxide film layer is used as a dielectric, and the surface of the oxide film layer is It is constructed by bringing an electrolytic solution, which forms an electrolyte layer, into contact with it, and further arranging a current collecting electrode, usually called a cathode.

As described above, the electrolytic solution for an electrolytic capacitor comes into direct contact with the dielectric layer and acts as a true cathode. That is, the electrolytic solution is interposed between the dielectric layer and the collector cathode of the electrolytic capacitor, and the resistance bones of the electrolytic solution are inserted in series with the electrolytic capacitor. Therefore, its characteristics become a major factor that influences the characteristics of electrolytic capacitors. For example, if the electrolytic solution has a low amount of conductive dust, it increases the equivalent series resistance inside the electrolytic capacitor, resulting in poor high frequency characteristics and loss characteristics.

From this background, electrolytes with high conductive dust have been selected, and conventionally known electrolytes with high conductive dust include organic acids such as adipic acid or their salts dissolved in glyfurs such as ethylene glycol or alcohols. These are mainly used for normal purposes.

(Problems to be Solved by the Invention) Due to the recent increase in the scope of use of electronic devices, there has been an increasing demand for improvements in the performance of electrolytic capacitors, and the current conductive dust in electrolytes is not sufficient. Particularly in the case of current electrolytes, when the desired conductive dust cannot be obtained or when an electrolyte with low solubility is used, water is intentionally added to improve the conductive dust. .

However, in recent years, when electrolytic capacitors are used for long periods of time at higher temperatures than conventional products, the presence of moisture in the electrolyte can cause deterioration of the dielectric film layer and internal steam of the electrolytic capacitor. This increases the pressure, leading to damage to the sealing part and evaporation of the electrolyte, which shortens its lifespan, and has the disadvantage that stable characteristics cannot be maintained over a long period of time.

Therefore, an object of the present invention is to improve the electrical characteristics of electrolytic capacitors and to maintain stable characteristics for a long time by providing a substantially non-aqueous highly conductive electrolytic solution containing an aprotic solvent as a main component. The purpose is to improve the reliability of electrolytic capacitors by maintaining them for a long period of time.

(Means for Solving the Problems) As a result of extensive research into an electrolyte that is a substantially non-aqueous electrolyte mainly composed of an aprotic solvent and provides high conductivity, the present inventors have found that an aliphatic unsaturated The present invention was achieved by discovering that N,N-dialkyltetrahydroxazinium compound salts of mono- or di-carboxylic acids have high solubility in aprotic solvents, have a high degree of dissociation, and impart high conductivity. .

That is, the electrolytic solution for an electrolytic capacitor according to the present invention has the general formula: (wherein, re + n = 4+ 1 = 2-4. n = 2
~0, R1+ R* are each an alkyl group having 1 to 6 carbon atoms, which may be the same or different, R3lR4 are hydrogen atoms, an alkoxy group having 1 to 6 carbon atoms, or 1 to 6 carbon atoms, which may each be the same or different. alkyl group, R is 1 carbon atom
~IO fulkenylene groups, X is a hydrogen atom or N shown in the formula; It is characterized by containing an N-dialkyltetrahydroxazinium compound salt as an electrolyte.

The aprotic solvents used include (1) tomethylformamide, N, as an amide type;
N-dimethylformamide, N-ethylformamide,
N, tomethylformamide, N-methylacetamide,
N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoric amide, (2) Dimethyl sulfoxide as oxide type (3) Acetonitrile as nitrile type, (4) Cyclic ester, as amide type Representative examples include γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, and propylene carbonate.

The polyhydric alcohol compound to be used in the present invention is preferably a dihydric alcohol compound or a monoalkyl ether of a dihydric alcohol compound, and the dihydric alcohol compound is ethylene glycol, and the dihydric alcohol monoalkyl ether compound is methyl cellosolve or a dihydric alcohol compound. It is ethyl cellosolve.

The weight ratio of the polyhydric alcohol compound to the aprotic solvent is (100-5G): (0-50), and 100% of the aprotic solvent is suitable, but up to about 50% of the polyhydric alcohol compound is substantially To avoid product deterioration,
May be used as appropriate.

The aliphatic unsaturated dicarboxylic acid compounds targeted by the present invention include maleic acid, citraconic acid, glutaconic acid, itaconic acid, allylmalonic acid, teraconic acid fumaric acid, mesaconic acid,
Examples include, but are not limited to, muconic acid.

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

N, N-dimethylmorpholinium N, N-diethyltetrahydro-.

N, N-diethylmorpholinium 1,2-oxazinium where R= C113, or Ctlls N, N-dimethyl-2-methoxy-N, ll-dimethyl-2,5-dimethyl-morpholinium
Morpholinium N, N-dimethyltetrahydro-1,
3-Oxazinium The tetrahydroxazine compound that is a raw material for the synthesis of the N,N-dialkyltetrahydroxazinium compound used in the present invention is, for example, tetrahydro-1,4-oxazine (morpholine), which is obtained by dehydrating jetanolamine with sulfuric acid or the like. It is produced industrially by ring closure and is available on the market, and is treated by N-methylation with an alkyl halide, such as methyl iodide, by a conventional method.
N,N-dimethylmorpholinium iodide can be obtained. This is subjected to electrodialysis using an ion exchange membrane and desalted with deiodine and anion exchange to produce a purified aqueous solution of N,N-dimethylmorpholinium hydroxide suitable for use in the electrolytic capacitor of the present invention. Get it.

Equimole or 1/2 mole of the desired aliphatic unsaturated dicarboxylic acid compound is added to this aqueous solution, neutralized, and evaporated to dryness under reduced pressure to obtain mono- or di-N, N- of the aliphatic unsaturated dicarboxylic acid. Dimethylmorpholinium salt can be obtained. Moreover, 1,3-oxazine or 1,2-oxazine is, for example, 11. It can be synthesized as appropriate by the method described in King: Journal Chemical Society, 1942, p. 432. For example, 1,2-oxazine can be synthesized as follows using ethyl hydroxamate and 1,4-dibromobutane as raw materials: Book The electrolytic solution for an electrolytic capacitor according to the invention generally comprises a desired aliphatic unsaturated dicarboxylic acid mono- or di-N, in a solvent prepared by mixing an aprotic solvent with a polyhydric alcohol compound or its monoalkyl ether compound as necessary. - Obtained by adding and dissolving a dialkyltetrahydroxazinium compound salt.

(Example) Hereinafter, examples of the electrolyte solution for electrolytic capacitors according to the present invention will be described.
Table 1 shows the electrical conductivity at 30 DEG C. of 20% by weight solutions of N-dialkyltetrahydroxazinium compound salts in various aprotic solvents or with ethylene glycol or methyl celluloph (ethylene glycol monomethyl ether). As a comparative example, a conventional standard electrolytic solution (8% ethysine liquor, 10% water, 12% diammonium adipate) is shown.

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

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

The produced electrolytic capacitors were made by using aluminum foil as an anode and a cathode, sandwiching separator paper and rolling it up to form a cylindrical capacitor element, which was impregnated with the electrolyte of each example and comparative example. It is stored in an external case and sealed.

Both use the same capacitor element and have a rated voltage of 1
The 6V rated capacity is fftlloμF.

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 of applying rated voltage at °C
) (dichotomous value).

As is clear from the results of this test, since the electrolytic solution of the present invention has a high conductivity, the loss, that is, t
The value of anδ becomes low.

In addition, since it essentially does not contain water, there is no appearance abnormality or decrease in capacitance due to increased internal pressure even when placed under high temperature loads.
Even when comparing the initial values and the characteristic values after 1000 hours, there is very little change in the properties of the present invention.

(Effects of the Invention) The electrolytic capacitor using the electrolyte according to the present invention has a low loss value and can maintain stable characteristics even when used at high temperatures for long periods of time, so it can be used at high frequencies and requires high efficiency. It can be used in power supply devices such as switching regulators, which are used for a long period of time, and various electrical devices that are used at high temperatures for long periods of time.

Claims (7)

[Claims] (1) General formulas in solvents that are mainly aprotic solvents: [▲There are mathematical formulas, chemical formulas, tables, etc.▼]▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, m + n = 4, m = 2 ~ 4, n=2~0, R_1
, R_2 are each an alkyl group having 1 to 6 carbon atoms which may be the same or different, R_3 and R_4 are each a hydrogen atom which may be the same or different, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. Alkyl group, R is 1 to 10 carbon atoms
mono- or di-N,N-dialkyl of an aliphatic unsaturated dicarboxylic acid compound of An electrolytic solution for electrolytic capacitors containing a tetrahydroxazinium compound salt as an electrolyte. (2) A solvent mainly composed of an aprotic solvent is 100 to 50 parts by weight of an aprotic solvent and 0 to 50 parts by weight of a polyhydric alcohol compound.
The electrolytic solution for an electrolytic capacitor according to claim 1, comprising parts by weight. (3) The aprotic solvent is N-methylformamide N,N
-dimethylformamide, N-ethylformamide, N
, N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide N-ethylacetamide, N,N-diethylacetamide, γ-butyrolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, dimethyl sulfoxide,
The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, which is selected from the group of acetonitrile or a mixture thereof. (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 a dihydric alcohol compound. (5) The electrolytic solution for an electrolytic capacitor according to claim 2, wherein the dihydric alcohol compound is ethylene glycol and the dihydric alcohol monoalkyl ether compound is methyl cellosolve or ethyl cellosolve. (6) N,N-dialkyltetrahydroxazinium compounds include N,N-dimethylmorpholinium, N,N-diethylmorpholinium, N,N-diethyltetrahydro-1,2-oxazinium, N,N-dimethyl The electrolytic solution for an electrolytic capacitor according to claim 1, which is -2-methoxymorpholinium, N,N-dimethyl-2,5-dimethylmorpholinium, or N,N-dimethyltetrahydro-1,3-oxazinium. (7) The aliphatic unsaturated dicarboxylic acid compound is maleic acid,
The electrolytic solution for an electrolytic capacitor according to claim 1, which is citraconic acid, glutaconic acid, or itaconic acid.