JPH0636975A - Electrolyte for driving electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain electrolyte for driving an electrolytic capacitor wherein dry-up phenomenon is restrained, life characteristics are improved, and an electrolytic capacitor excellent in thermal stability and low temperature characteristics can be obtained. CONSTITUTION:A capacitor of 16V-100muF is formed by using electrolyte wherein 20g tetramethyl phthalate ammonium and 6g hydroxypropyl cellulose are dissolved in 100ml, solvent of gamma-butyrolactone. The above capacitor is subjected to a test wherein a rating voltage is continuously applied at 115 deg.C for 2000 hours, and the change of capacitance and the change of dielectric loss are measured. The results show that capacitance change ratio and change amount of tandelta are low as compared with an electrolytic capacitor using the conventional electrolyte.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor.

[0002]

2. Description of the Related Art An electrolytic capacitor comprises a separator paper, which is dipped in an electrolytic solution for driving the electrolytic capacitor (hereinafter referred to as "electrolyte solution"), and an aluminum foil. The structure is sealed by packing, and aluminum is used as a positive electrode.

The electrolytic solution of such an electrolytic capacitor uses ethylene glycol as a main solvent and an organic acid such as adipic acid, formic acid or benzoic acid, or a salt thereof as a solute, or an inorganic acid such as boric acid or phosphoric acid. Or, those that use the salt as a solute are often used.

The electrolytic solution containing ethylene glycol as the main solvent has a low permeability to the rubber packing for sealing the solvent and little leakage of the solvent, but the ethylene glycol is easily esterified, so that the electrolytic solution is thermally stable. Poor nature. Further, since the melting point of ethylene glycol is high, there are problems such as insufficient low temperature characteristics of the electrolytic solution.

Further, as an electrolytic solution having excellent thermal stability and low temperature characteristics, an electrolytic solution in which γ-butyrolactone solvent is a solute of tetramethylammonium phthalate, which is a quaternary ammonium salt of phthalic acid, is used in γ-butyrolactone solvent. An electrolytic solution has been proposed in which a tetramethylammonium maleic acid tetramethylammonium salt, which is a quaternary ammonium salt of maleic acid, is used as a solute (JP-A-63-69213).

[0006]

However, in such an electrolytic solution using γ-butyrolactone as a solvent, the permeability of the solvent to the rubber packing for sealing is larger than that of ethylene glycol, and the solvent easily leaks and leaks. In particular, in the case of a small electrolytic capacitor with a low height (low profile), the thickness of the rubber packing for sealing is thin, so that the solvent seeps out and leaks noticeably, and finally the electrolyte solution becomes dry. (Dry-up phenomenon) occurs. As a result, there is a problem that the performance of the electrolytic capacitor is significantly deteriorated and the life characteristics are deteriorated.

The present invention has been made in view of the above circumstances, and by dissolving a thickener in an electrolytic solution, the life characteristics of an electrolytic capacitor, particularly a low-profile and small-sized electrolytic capacitor are improved, and salani γ -An object of the present invention is to provide an electrolytic solution that improves the life characteristics, thermal stability and low temperature characteristics of an electrolytic capacitor by using butyrolactone as a solvent.

[0008]

The electrolytic solution for driving an electrolytic capacitor according to the first invention is characterized by containing hydroxypropylcellulose.

The electrolytic solution for driving the electrolytic capacitor according to the second aspect of the invention is characterized in that γ-butyrolactone is used as the solvent and contains hydroxypropyl cellulose.

[0010]

In the electrolytic solution for driving the electrolytic capacitor of the present invention,
By dissolving hydroxypropyl cellulose in the solvent, the viscosity of the electrolytic solution is increased, the mobility of particles in the electrolytic solution is lowered, and the permeability thereof is lowered. Also, γ
-By using butyrolactone as a solvent, it is possible to obtain an electrolytic solution having low permeability and further excellent thermal stability and low temperature characteristics.

[0011]

EXAMPLES The present invention will be specifically described below with reference to its examples.

[0012]

[Table 1]

Table 1 is a table showing the solvents, solutes and conductivities of the electrolytic solutions A, B, C, D and E. Electrolytes A, B, C, and D are the examples of the present invention. 100 ml of γ-butyrolactone was used as a solvent, and 20 g of tetramethylammonium phthalate salt and hydroxypropyl cellulose were respectively added.
10g, 6g, 4g, 2g are dissolved. The electrolytic solution E is a conventional example, and 100 ml of γ-butyrolactone is used as a solvent,
20 g of tetramethylammonium phthalate salt is dissolved as a solute.

The viscosity of these electrolytes increases as the amount of hydroxypropyl cellulose, which is a thickener, is increased. Then, as shown in Table 1, the conductivity of the electrolytic solution decreases as the viscosity increases. Conductivity is 7.0mS in case of Electrolyte E with 10g thickener added to 100ml solvent.
/ cm (25 ° C), which is not a problematic value for use.

Next, using these electrolytic solutions A to E, trial production of electrolytic capacitors having a capacity of 100 μF at a working voltage of 16 V, and a high temperature load test (rated voltage continuous application test) of 115 ° C. and 2000 hours was made for each. Was carried out. The results are shown in Table 2 below. These capacitors have a normal structure in which the electrolytic capacitor element is housed in an aluminum case and sealed with rubber packing.

[0016]

[Table 2]

Table 2 shows that the electrolytic solutions A to E were subjected to a high temperature load test at 115 ° C. for 2000 hours, and as a result, the capacity of each electrolytic capacitor and the loss (tan δ) which is an index of the electric resistance value were set to initial values, It shows after 1000 hours, 1500 hours, and 2000 hours. For capacities other than the initial value, the rate of change (ΔC / C) is shown.

From Table 2, there is no significant difference after 1000 hours, but after 1500 hours, the electrolytic capacitors using the electrolyte solutions A, B, C and D containing hydroxypropyl cellulose showed an increase in tan δ. It has a small amount and shows stable characteristics. Further, since the electrolytic capacitor using the electrolytic solution D shows only a slight difference as compared with the electrolytic capacitor using the electrolytic solution E to which hydroxypropyl cellulose is not added, hydroxypropyl cellulose is a solvent for the electrolytic solution. It can be seen that the addition of 4 g or more per 100 ml has a great effect of showing stable characteristics.

As described above, by adding 4 g or more of hydroxypropyl cellulose, which is a thickener, to 100 ml of γ-butyrolactone, which is a solvent of the electrolytic solution, the viscosity of the electrolytic solution is increased and leakage of the solvent is suppressed. Since the dry-up phenomenon can be prevented, the increase in tan δ of the electrolytic capacitor using this electrolytic solution can be suppressed, the heat generation of the electrolytic capacitor can be suppressed, and the life characteristics can be improved. Also,
Since the solvent is γ-butyrolactone, an electrolytic capacitor having good thermal stability and low temperature characteristics can be obtained by using this electrolytic solution.

In this example, γ-butyrolactone was used as the solvent. However, the solvent is not limited to this, and N, N dimethylformamide, N-ethylformamide, methylcarbitol, methylcellosolve, etc. may be used alone or They may be mixed and used, and it is possible to obtain an electrolytic capacitor which suppresses solvent leakage and prevents a dry-up phenomenon and has good life characteristics.

[0021]

As described above, in the electrolytic solution for driving an electrolytic capacitor of the present invention, by adding hydroxypropyl cellulose to the solvent of the electrolytic solution, an electrolytic capacitor having improved life characteristics can be obtained. Furthermore, by adding 4 g or more of hydroxypropyl cellulose to 100 ml of the solvent γ-butyrolactone of the electrolyte solution, the life characteristics can be improved and an electrolytic capacitor having good thermal stability and low temperature characteristics can be obtained. It has an excellent effect.

Claims (2)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, which comprises hydroxypropyl cellulose. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein γ-butyrolactone is used as the solvent.