JPH0566005B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing aluminum foil for electrolytic capacitors, and more specifically, to a hydration treatment performed prior to chemical conversion of the aluminum foil. [Prior Art] Electrode foils used as anodes for electrolytic capacitors, such as smooth aluminum foils or aluminum foils whose surface area has been expanded by etching, are subjected to hydration treatment prior to chemical conversion treatment to form an anodic oxide film. administered. The purpose of hydration treatment is to form a hydroxide film on the surface of aluminum foil.
This is usually done by immersing the aluminum foil in high-temperature pure water. [Problems to be Solved by the Invention] According to this, the amount of electricity used during chemical formation is saved, and the capacitance is also increased. However, good results cannot be obtained when the withstand voltage is low, and there is a restriction that it is useful only when the withstand voltage is about 150V or higher. Therefore, it has been proposed to add a small amount of alkali silicate to pure water for hydration treatment (see, for example, Japanese Patent Publication No. 1983-6250). According to this method, the hydration treatment is said to be useful even for low voltages, but tan δ (tangent of loss angle) and leakage current are not particularly improved. [Means for Solving the Problems] In order to solve the above problems, in the present invention, prior to performing a chemical conversion treatment to form an oxide film on the aluminum foil, the aluminum foil is soaked in an aqueous solution containing an amine and an acid. It is characterized by hot water treatment. In this case, the temperature of the hot water is preferably 90°C or higher. According to this, even when the voltage used is low, the amount of electricity used during chemical formation is saved, the capacitance is increased, and tan δ and leakage current are reduced. Note that the amine concentration is preferably 0.005 to 0.1 mol/l. Amines that can be used include ethylamine, diethylamine, triethanolamine, propylamine, dipropylamine, butylamine, and the like. Furthermore, examples of acids that can be used include acetic acid, benzoic acid, and boric acid. Furthermore, the pH of the aqueous solution is preferably in the range of 5 to 9. [Example] Example 1 (A) Pretreatment: Adding ethylamine and acetic acid,
The aluminum foil was immersed in an aqueous solution (liquid temperature of 98° C. or higher) with an amine concentration of 0.01 mol/l and a pH of 6 for 9 minutes to undergo hot water treatment. (B) Chemical conversion treatment; current density 10 mA/
cm ² , and a formation voltage of 380 V was applied for 40 minutes. (C) Depolarization treatment; PH9 ammonia water (liquid temperature 70℃)
immersed in it for 3 minutes. (D) Heat treatment: The sample was left in a heated atmosphere at 500°C for 2 minutes. (E) Reconstitution; same as (B) above. However, the application time is
13 minutes. (F) Depolarization treatment; same as (C) above. (G) Heat treatment; same as (D) above. (H) Reconstitution; same as (E) above. (I) Post-treatment: Immersed for 4 minutes in a mixed aqueous solution of phosphoric acid and ammonia (liquid temperature: 30°C) of pH 6.5. Example 2 (A) Pretreatment: Aluminum foil was immersed in an aqueous solution (liquid temperature of 98°C or higher) for 9 minutes to perform hot water treatment by adding ethylamine and benzoic acid to give an amine concentration of 0.01 mol/l and a pH of 6. . The subsequent steps (B) to (I) are the same as in Example 1 above. Example 3 (A) Pretreatment: Adding ethylamine and boric acid,
The aluminum foil was immersed in an aqueous solution with an amine concentration of 0.01 mol/l and a pH of 6 (liquid temperature of 98° C. or higher) for 9 minutes to undergo hot water treatment. The subsequent steps (B) to (I) are the same as in Example 1 above. Example 4 (A) Pretreatment: Aluminum foil was immersed in an aqueous solution (liquid temperature of 98° C. or higher) of 0.01 mol/mol/pH 6 for 9 minutes to perform hot water treatment by adding diethylamine and acetic acid. The subsequent steps (B) to (I) are the same as in Example 1 above. Example 5 (A) Pretreatment: Aluminum foil was immersed in an aqueous solution (liquid temperature of 98°C or higher) of 98°C or higher for 9 minutes to undergo hot water treatment by adding triethalamine and acetic acid to give an amine concentration of 0.01 mol/l and a pH of 6. did. The subsequent steps (B) to (I) are the same as in Example 1 above. Comparative Example 1 (A) Pretreatment: Aluminum foil was immersed in pure water (liquid temperature 98° C. or higher) for 9 minutes to undergo hot water treatment. subsequent
The steps (B) to (I) are the same as in Example 1 above. Comparative Example 2 (A) Pretreatment: Aluminum foil was heated with hot water containing alkali silicate at a silicon concentration of 0.1% (liquid temperature 98°C or higher)
The samples were immersed in a hot water solution for 9 minutes and treated with hot water. Subsequent (B)~
The steps up to (I) are the same as in Example 1 above. An electrolytic capacitor with a rating of 250 V and 30 μF was prototyped using the chemically formed aluminum foil (15 x 270 mm) obtained in Examples 1 to 5 and Comparative Examples 1 and 2 as an anode, and its capacitance, tanδ, and leakage current were measured. The measured results are shown in the table below.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, aluminum foil is treated with hot water in an aqueous solution containing an amine and an acid, thereby reducing the amount of electricity used during the subsequent chemical conversion treatment and increasing the capacitance. , tan δ (electrical loss angle) and leakage current reduction are achieved.

Claims (1)

[Claims] 1. An aluminum foil for an electrolytic capacitor, characterized in that, prior to performing a chemical conversion treatment to form an oxide film on the aluminum foil, the aluminum foil is subjected to hot water treatment in an aqueous solution containing an amine and an acid. manufacturing method. 2 The concentration of amine in the above aqueous solution is
The method for producing aluminum foil for electrolytic capacitors according to claim 1, wherein the content is 0.005 to 0.1 mol/l. 3. The method for producing an aluminum foil for an electrolytic capacitor according to claim 1 or 2, wherein the amine added to the aqueous solution is selected from ethylamine, diethylamine, triethanolamine, propylamine, dipropylamine, and butylamine. 4. The method for producing an aluminum foil for an electrolytic capacitor according to claim 1, wherein the acid is selected from acetic acid, benzoic acid, and boric acid. 5. The method for producing an aluminum foil for an electrolytic capacitor according to claim 1, wherein the aqueous solution has a pH of 5 to 9.