JPS63228708A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrolytic capacitor, and more particularly to an electrolytic capacitor using a novel driving electrolyte.

[Prior Art] Electrolytic capacitors are made by winding an anode foil and a cathode foil made of an fF action metal such as aluminum together with a separator to form a capacitor element.Generally, the capacitor element is impregnated with a driving electrolyte, and an aluminum foil is formed by impregnating the capacitor element with a driving electrolyte. The capacitor element is housed in a metal case such as , or a case made of synthetic wood, and the structure is sealed.

As a driving electrolyte for this type of electrolytic capacitor,
Conventionally, electrolyzers have been commonly used in which a polar organic solvent such as ethylene glycol is used as the solvent, and a salt that does not interfere with metal electrodes, such as ammonium salt of saturated iron, is dissolved in the solvent (in particular, Publication No. 58-13019). It is also known that a mixed solvent of γ-butyrolactone and ethylene glycol is used as a solvent for the electrolytic solution (Japanese Unexamined Patent Publication No. 7564/1983). [Problems to be Solved by the Invention] However, In the electrolytic solution disclosed in No. 5B-13019, in order to lower the tangent of the loss angle (tan δ), which is an index of electrical resistance, the deterioration of capacitor characteristics at high temperatures due to evaporation of lmonium (NHs), especially the loss There was a problem in that the tangent (tan δ) of the angle varied greatly. In addition, the conductivity is high (low 1 air resistance),
Furthermore, as an electrolytic solution that is stable at high temperatures, the use of an electrolytic solution prepared by dissolving a quaternary ammonium salt of a saturated chain dicarboxylic acid in a polar organic solvent is disclosed in JP-A-59-78522. However, according to the examples in the same publication, the conductivity of this electrolyte is at most 9.4 mS/cm, which is higher than the currently required level (12 to 25 mS/cm).
), there was a problem that it was insufficient. Furthermore, when using γ-butyrolactone and ethylene glycol as shown in the above-mentioned JP-A-54-7564 as a mixed solvent, the viscosity of ethylene glycol increases at low temperatures, which improves the low-temperature characteristics of the capacitor. The problem was that it was small.

The present invention solves these problems and provides an electrolytic capacitor using a driving electrolyte that has low electrical resistance (high conductivity), excellent low-temperature characteristics, and high-temperature stability. purpose.

[Means for Solving the Problems] In order to solve the above problems, the present invention is characterized by using a driving electrolyte prepared by dissolving a quaternary ammonium salt of O-phthalic acid in a polar organic solvent. The present invention provides an electrolytic capacitor that has the following characteristics.

The quaternary ammonium salt of O-7 talic acid used in the present invention is one in which the alkyl group (R) of the quaternary ammonium represented by the general formula R,N has 1 to 10 carbon atoms, especially 1 to 10 carbon atoms. Four types can be suitably used, and examples thereof include tetramethylammonium O-phthalate, tetraethylammonium O-phthalate, tetrapropylammonium O-phthalate, and tetrabutylammonium O-phthalate. .

The reason why the quaternary ammonium salt of °C,a-phthalic acid is used in the present invention is because O-phthalic acid is other ammonium salts.

The content (concentration) of the quaternary ammonium salt of 0-phthalic acid used in the present invention in the electrolyte composition can be selected as appropriate, but considering that the specific resistance is the lowest in the state of a saturated solution, 1 -50% by weight is suitable, especially 5-40% by weight to obtain good high temperature stability.
is suitable.

In order to solve the above problems, the polar organic solvent used in the present invention includes at least γ-butyrolactone and N,N-
Contains dimethylformamide. Here, examples of the alkyl group include methyl, ethyl, propyl, etc., among which methyl and ethyl are preferred from the viewpoint of improving low-temperature properties. Further, as the solvent to be mixed, any polar organic solvent commonly used in electrolytic capacitors can be used, and amides, lactones, glycols, sulfur compounds, or carbon salts are preferably used. Examples of preferred miscible solvents include N-methylformamide, β-butyrolactone, γ-valerolactone, N-methylpyrrolidone, ethylene glycol, ethylene glycol monoalkyl ether, and ethylene glycol dialkyl. Ether, dimethyl sulfoxide, propylene carbonate, ethylene cyanohydrin, etc. can be used, and these solvents may be used alone or in combinations of a plurality of them as appropriate.

In the present invention, in order to obtain a driving electrolyte containing a quaternary ammonium salt of O-phthalic acid, this quaternary ammonium salt may be added to a polar organic solvent.
The quaternary ammonium salt of phthalic acid may be produced by reacting substances capable of producing the quaternary ammonium salt.

In the present invention, it is not necessary to include water in the electrolytic solution, but it is effective to lower the specific resistance. However, if the amount of water spray exceeds a certain limit, it will increase the expansion of the case of the capacitor due to the generation of internal gas and the erosion of the electrode foil, so it should not be used for long periods at high temperatures. Depending on the purpose of use, the water content is preferably in the range of 1 to 20% by weight in the electrolytic solution m acid.
, a range of 0.5 to 15% by weight is more preferable.

The electrolytic capacitor of the present invention includes various types of capacitors. In a typical embodiment, an aluminum foil anode and an aluminum foil cathode separated by an appropriate separator such as paper are used, and these are arranged in a cylindrical shape to form a capacitor or capacitor element, and this element is injected with a driving electrolyte. Impregnate with liquid. The content of the electrolyte is as follows for the separator:
Preferably it is 50 to 300% by weight. The element impregnated with the electrolyte is housed in a case made of corrosion-resistant metal, synthetic resin, or the like, and has a sealed structure.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

A 10% aqueous solution of tetraalkylammonium hydroxide (alkyl group has 1 to 3 carbon atoms) and O-phthalic acid are mixed to have an equimolar number, and after dissolving O-phthalic acid, water is removed using a 5-evaporator. This was removed to produce a quaternary ammonium salt of O-7 talic acid, and a predetermined amount was dissolved in a polar 4F organic solvent using the stiff solids as a solute to obtain the electrolytes of Examples 1 to 10. The pH of the electrolyte was adjusted to 5-7.

Using these electrolytes, we manufactured an electrolytic capacitor (constant AIOV, 1000 μF) with aluminum electrodes,
A high temperature load test (rated voltage applied, 125° C., 1000 hours) was conducted to measure changes in the loss angle tangent (tan δ), and the results are shown in Table 1. In addition, Comparative Examples 1 to 4 are cases in which a solute other than the quaternary ammonium salt of 0-phtaceic acid is used, and a C electrolytic capacitor was manufactured in the same manner as in the example, and a high temperature load test was conducted under the same conditions as in the example. The results are shown in Table 1. In addition, DMF in Table 1 is N,
Indicates N-dimethylformamide.

Next, Table 2 shows the low temperature characteristics of electrolytic capacitors. 7 shows the capacitance of the capacitor, which is the same as that described above, is the rate of change, and Z/220°C shows the impedance ratio with respect to 20°C.

Average value of n; 10 As can be seen from Table 1, in the comparative example, the change in the tangent of the loss angle was large in the high temperature load test, whereas in the example, this change could be made small.

Furthermore, as can be seen from Table 2, the comparative example has a large change rate at 8C/C 20°C and Z/Z 20°C in low-temperature characteristics, whereas the example has a different rate of change. It is something that can be done.

Finally, Figure 1 shows the amounts of N, N-dimethylformamide and γ-butyrolactone and the conductivity of the electrolyte when the amounts of 0-tetra phthalate and methylammonium in the electrolyte are constant (20wt%). Indicates the relationship between Also, the second
The figure shows the relationship between the amount of tetramethylammonium 0-phthalate added and the conductivity of the electrolytic solution when the amounts of N,N-dimethylformamide and γ-butyrolactone are equal.

[Effects of the Invention] As explained above, according to the present invention, an electrolytic capacitor with excellent low temperature characteristics and excellent high temperature stability with small change in tangent of loss angle (tan δ) under high temperature conditions can be obtained. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the amount of N,N-dimethylformamide and γ-butyrolactone in the electrolytic solution according to the present invention and the electrical conductivity of the electrolytic solution. It is a characteristic diagram showing the relationship between the amount of 0-7 tetramethylammonium talate and the electrical conductivity of the electrolytic solution.

Claims (3)

[Claims] (1) An electrolytic capacitor characterized by using a driving electrolytic solution prepared by dissolving a quaternary ammonium salt of o-phthalic acid in a polar organic solvent consisting of γ-butyrolactone and N,N-dimethylformamide. (2) The electrolytic capacitor according to claim 1, wherein the content of the quaternary ammonium salt of o-phthalic acid in the driving electrolyte is 1 to 50% by weight. (3) Claim 1 or 2, characterized in that the alkyl group (R) of the quaternary ammonium represented by the general formula R_4N^+ has 1 to 10 carbon atoms. electrolytic capacitor.