JPH0353768B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an electrolytic solution for an electrolytic capacitor, and more particularly to an electrolytic solution for an electrolytic capacitor using a halogen-free quaternary ammonium salt as an electrolyte. (Prior art and its problems) A general method for synthesizing a quaternary alkylammonium salt is KX (X is a halogen), which is produced by reacting a halogen tetraalkylammonium and a desired anion together with KOH in an organic solvent. There is a method in which the solvent is removed after filtration, and a method in which a tetraalkylammonium hydroxide obtained by treating a halogenated tetraalkylammonium with wet silver oxide and a desired anion are used. however,
These methods include _R4NX , KX, KOH, _H2O ,
Because it contains impurities such as AgX, it cannot be used as an electrolyte for electrolytic capacitors, so it had to be purified. This purification method includes recrystallization method and anion exchange method.
Although KX, KOH, and H ₂ O can be removed by the recrystallization method,
R ₄ NX has a tendency to dissolve in the solvent used for recrystallization.
Since it is the same as R ₄ NA (A is an anion other than halogen), it cannot be removed. With the anion exchange method, it is difficult to remove halogens to a level that can be used in electrolytes for electrolytic capacitors, and there are drawbacks such as an increase in Na ions due to the contamination of NaOH used to regenerate the anion exchange resin. Ta. Therefore,
Electrolytic solutions using electrolytes produced by these methods suffer from corrosion, destruction of sealing parts, liquid leakage, etc., and are difficult to put into practical use. Therefore, an object of the present invention is to provide an electrolytic capacitor using a tetraalkylammonium salt, which is provided by a manufacturing method that completely eliminates the presence of halogens and alkali metal ions in the electrolyte used in the electrolytic capacitor. is to provide. (Means for Solving the Problems) In order to achieve the above object, the electrolytic solution for electrolytic capacitors of the present invention has the general reaction formula () (In the formula, R ₁ , R ₂ , and R ₃ represent C ₁ to C ₄ alkyl groups.) Tetraalkylammonium carbonate obtained by the reaction is electrolyzed under a cation exchange membrane, and the resulting water It is characterized by using a tetraalkylammonium salt synthesized from a tetraalkylammonium oxide compound as a raw material as an electrolyte. In the above-mentioned tetraalkylammonium salt, halogen and alkali hydroxide, which are the main causes of corrosion of electrolytic capacitors, destruction of sealing parts, liquid leakage, etc., are excluded from the manufacturing raw materials. Examples of tetraalkylammonium salts include salts of phenols and organic acids, such as phenols,
Examples include propionic acid, maleic acid, acetoacetic acid, and the like. (Example) Next, the present invention will be specifically explained using preferred examples, but it goes without saying that the present invention is not limited to these examples. Example 1 Synthesis example of tetraalkylammonium hydroxide Tetramethylammonium carbonate obtained from trimethylamine and dimethyl carbonate was made into a 10% aqueous solution and electrolyzed using a cation exchange membrane to obtain tetramethylammonium hydroxide.
That is, the electrolytic cell was separated into a cathode chamber with a stainless steel cathode and an anode chamber with a graphite anode by using Nafion Membrane 427 manufactured by DuPont as a cation exchange membrane as a diaphragm, and a 10% aqueous solution of tetramethylammonium carbonate was circulated into the anode chamber. Then, pure water was circulated through the cathode chamber and electrolysis was carried out at a current density of 0.1 A/cm ² until 10% by weight of tetramethylammonium hydroxide was obtained in the cathode chamber. Triethyl methyl ammonium carbonate obtained from triethylamine and dimethyl carbonate was treated in the same manner as above to obtain triethyl methyl ammonium hydroxide. Tripropyl methylammonium carbonate obtained from tripropylamine and dimethyl carbonate was treated in the same manner as above to obtain tripropyl methylammonium hydroxide. Trimethyl ethylammonium carbonate obtained from dimethyl ethylamine and dimethylamine was treated in the same manner as above to obtain trimethyl ethylammonium hydroxide. Example 2 Preparation of tetramethylammonium phenolate An equivalent amount of phenol was added to the aqueous solution of tetramethylammonium hydroxide obtained in Step 2 to obtain a tetramethylammonium phenolate solution, and the water was removed under reduced pressure to form tetramethylammonium phenolate. Got enolate. Example 3 Preparation of triethyl methyl ammonium malate: Triethyl methyl ammonium malate was obtained by treating the triethyl methyl ammonium hydroxide aqueous solution obtained in step 1 with maleic acid in the same manner as in Example 2. The tripropyl methylammonium hydroxide aqueous solution obtained in Example 4 and propionic acid were treated in the same manner as in Example 2 to obtain tripropyl methylammonium propionate. The aqueous solution of trimethyl ethylammonium hydroxide obtained in Example 5 and acetoacetic acid were treated in the same manner as in Example 2 to obtain trimethyl ethylammonium acetoacetate. Control Example 1 KC1 produced by reacting tetramethylammonium chloride and phenol together with KOH in ethyl alcohol is filtered out and then desolvated and dehydrated. Furthermore, the product was re-extracted with propyl alcohol and the solvent was removed, which was further recrystallized from propyl alcohol to obtain tetramethylammonium phenolate. Control Example 2 Triethyl methyl ammonium malate was obtained using triethyl methyl ammonium chloride and maleic acid in the same manner as in Control Example 1. Control Example 3 Tripropyl methyl ammonium propionate was obtained by treating tripropyl methyl ammonium chloride and propionic acid in accordance with Control Example 1. Control Example 4 Trimethyl ethylammonium acetoacetate was obtained using trimethyl ethylammonium chloride and acetoacetic acid in the same manner as in Control Example 1. Example 6 Examples 2, 3, 4, and 5; and Control Example 1,
The halogen concentration of each of the tetraalkylammonium salts obtained in 2, 3 and 4 was measured and the results were as follows. Halogen concentration (wt%) Example 2 0.001 or less 3 Same as above 4 Same as above 5 Same as above Control example 1 1.44 2 0.82 3 0.67 4 0.98 Example 7 Examples 2, 3, 4 and 5; Each tetramethylammonium salt is N,
Each of the electrolytes was dissolved in N-dimethylformamide to give a 10% by weight electrolytic solution, which was impregnated into a wound capacitor element and subjected to a life test at high temperatures. The results are shown in Table 1.

[Table] ... cannot be measured due to severe corrosion.
* Number of corrosion occurrences for 20 sample capacitors.
(Effects of the Invention) According to the present invention, a tetraalkylammonium salt can be used for electrolytic capacitors, thereby providing an excellent electrolytic solution for electrolytic capacitors that is extremely stable in terms of life.

Claims (1)

[Claims] 1 General reaction formula () (In the formula, R ₁ , R ₂ , and R ₃ represent C ₁ to C ₄ alkyl groups.) Tetraalkylammonium carbonate obtained by the reaction is electrolyzed under a cation exchange membrane, and the resulting water An electrolytic solution for electrolytic capacitors whose electrolyte is a tetraalkylammonium salt synthesized from a tetraalkylammonium oxide compound. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the tetraalkylammonium salt is a salt of phenols or organic acids.