JPS6046815B2 - Electrolyte for driving electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving electrolytic solution that constitutes an aluminum electrolytic capacitor together with electrodes, and particularly aims to provide a driving electrolytic solution that is less likely to damage the electrodes.

A drawback of conventional aluminum electrolytic capacitors is that leakage current increases over time when left unloaded at high temperatures.

This phenomenon occurs because the drive electrolyte damages the oxide film on the anode, deteriorating its voltage resistance.If the deterioration is significant, the electrolytic capacitor may be destroyed by the load after being left for a long time. There is a fear. On the other hand, the demand for loss reduction for electrolytic capacitors has recently become particularly strong, and it has therefore become necessary to use a driving electrolyte with high activity, and the fear of deterioration is also increasing.

In view of this, the present invention attempts to provide a driving electrolytic solution with extremely low electrolytic deterioration by incorporating a special compound as a result of various studies. There have been many examples of using dicarboxylic acids with two carboxyl groups in driving electrolytes, but all of them are chain compounds or aromatic compounds, and all of them have an aluminum anodic oxide film. The current situation is that the leakage current increases significantly after being left in a high-temperature, unloaded state, and that it has not yet been possible to obtain fully satisfactory results.

Therefore, the present inventors focused on dicarboxylic acids, which are alicyclic unsaturated compounds, and their salts, and as a result of conducting several experiments, they were able to develop a driving electrolyte with extremely small changes in leakage current over time. , the gist of which is that the number of carbon atoms in the cyclic structure is 6 to 7 among alicyclic unsaturated compounds,
1 or 2 double bonds in a 6-membered ring or 3 in a 7-membered ring
It is characterized by containing at least one type of organic acid having two carboxyl groups or a salt thereof. In the present invention, among dicarboxylic acids of alicyclic unsaturated compounds, the number of carbon atoms in the cyclic structure is limited to 6 to 7. It is thought that there is a good possibility that dicarboxylic acids (dicarboxylic acids with 6 or more carbon atoms) have the same properties as those with carbon atoms of 6 or more, but unfortunately, those with less than 6 carbon atoms contain large amounts of halogens that have a strong oxide film deterioration effect during the manufacturing process. Because halogens are retained as impurities, and it is difficult to remove halogens, it is not possible to obtain samples of good quality that do not contain halogens. This is due to circumstances in which the intended effects of the present invention could not be confirmed under the current difficult circumstances.

Alicyclic unsaturated compounds with a cyclic structure having 6 to 7 carbon atoms include dicarboxylic acid-based organic compounds such as cyclohexene, cyclohexadiene, and cycloheptatriene, that is, anhydrous 4
-cyclohexene 1,2-dicarboxylic acid 3,5-cyclohexadiene-1,2-dicar diphonic acid anhydride 1,3,
There are 6-cycloheptatriene-1,2-dicarboxylic acids, etc., and all of them have been found to have effective effects, but in the case of industrialization, cyclohexene dicarboxylic acids are preferred due to economic efficiency and easy availability of products with good purity. Compounds are optimal.

When a dicarboxylic acid compound of an alicyclic unsaturated compound is added to the driving electrolyte, the reason why the property of causing oxides on the aluminum surface disappears is not clear, but it is probably due to a large number of hydrogen atoms in the cyclic structure. It is presumed that this is related to the existence of the component as a component.

The content of this compound in the electrolyte in the present invention is 0.1
The effect is observed at % by weight, and the effect increases as the amount increases, but when it exceeds 10%, it becomes difficult to dissolve, and when it exceeds 50%, crystal precipitation occurs, making it difficult to use.

Examples of the present invention will be described below, and a comparison with a conventional method will be shown below.

Example 1 1 Commercially available etched aluminum foil (purity 99.99%)
) to the commonly used ammonium hydrogen phosphate 1.5g/
l? Anode (anode foil area: 147 cm) was anodized in a chemical solution at 85°C at a DC voltage of 62 cm to form a voltage-resistant oxide film.
rn×27'') was obtained, and this anode and a commercially available etched aluminum foil for a cathode were rolled up with a commercially available separator paper interposed therebetween to create a capacitor element.

2 The above capacitor elements were impregnated by immersing them in the following two types (A, B) of driving electrolytes (85° C.).

The driving electrolytic solution A below is a commonly used electrolytic solution containing a salt of adipic acid, which is a dicarboxylic acid with a chain structure, as a main component, and the driving electrolytic solution B below is an electrolytic solution according to the present invention. It is an electrolyte. Ingredients of A (expressed in weight%) Ethylene glycol 77.6% Ammonium adipate 10.5% Water
11.9% 85% phosphoric acid is added to 1' of the above solution at a ratio of 30 mg.

Component B 70y of ammonium dicarboxylate of cyclohexene was added to the electrolytic solution 1e of A above.

An electrolytic capacitor was assembled by enclosing a capacitor element impregnated with three electrolytes in an aluminum case with an outer diameter of 13 mm and a length of 26 mm.

4 The capacitor completed above was aged in a constant temperature bath at 85° C. by applying a DC voltage of 58 V for 8 hours.

5 After leaving the aged capacitor in the atmosphere at 200C for 2 hours, a DC voltage of 50V was applied, the leakage current was measured after 1 minute, and the capacitance was then measured.

3 This capacitor was placed in a constant temperature bath at 85° C. and subjected to no-load aging treatment for 500 hours, and then the same measurements as in Section 5 were performed again.

7 The measurement results according to items 5 and 6 above are as follows.

From the above results, it is understood that the stabilizing effect when using the driving electrolyte according to the present invention is extremely significant.

Example ■ 1 In Example 1, the anodization voltage was changed to 16V, the aging voltage was changed to 11.5V, the leakage current measurement voltage was changed to 10V, and the electrolytes A and B were selected as follows, and the other conditions were the same. did.

Ingredients of A (expressed in weight%) Ethylene glycol 74.5% Ammonium formate 5.4% Ammonium adipate 8.7% Water
11.4%, compared to 11 dissolved above, 8
Add 30 mg of 5% phosphoric acid.

Component B 37y of cycloheptatriene dicarboxylic acid was added to the electrolytic solution 1e of A above, and this was dissolved in P with aqueous ammonia.
Adjusted so that the H value is 7.

2 The results obtained in the same manner as in Example 1 are as follows.

As is clear from the above results, the same effects as in Example 1 are observed when cycloheptatriene dicarboxylic acid is used.

Example (1) In Example (2) above, the electrolytes A and B were selected as follows, and the aging time was 2 hours, and the other conditions were the same.

Ingredient A (indicates weight%) Ethylene glycol 74.3% Ammonium adipate 9.8% Water
Add 85% phosphoric acid at a ratio of 30 m9 to 1' in which 15.9% of the above was dissolved.

Component B 70y of cyclohexadiene dicarboxylic acid was added to the electrolytic solution 1' of A above, and the pH value was adjusted to 7 with aqueous ammonia.

2 The results obtained in the same manner as in Example 2 are as follows.

As is clear from the above results, the same effects as in Examples 1 and 2 were observed, and the aging time was
A similar effect can be obtained even if the length is shortened to 14, and this is understood to be advantageous in terms of work efficiency.

As described in detail above, according to the present invention, the increase in leakage current can be kept low for a long period of time, and the invention is effective in stabilizing the performance of the capacitor.

Claims (1)

[Claims] 1. Among alicyclic unsaturated compounds, the number of carbon atoms in the cyclic structure is 6 to 7, and the number of double bonds is 1 to 2 in a 6-membered ring, or 3 in a 7-membered ring. and carboxyl group 2
1. An electrolytic solution for driving an electrolytic capacitor, characterized in that it contains at least one kind of an organic acid or a salt thereof. 2 The amount of the compound described in claim 1 is 0.1
An electrolytic solution for driving an electrolytic capacitor having a concentration of 50 to 50% by weight.