JP2012134550A - Aluminum electrolytic capacitor electrolyte and manufacturing method for core solute thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum electrolytic capacitor electrolyte and a manufacturing method for its core solute, and especially a mid-to-high voltage aluminum electrolytic capacitor electrolyte having high thermal stability.SOLUTION: An aluminum electrolytic capacitor electrolyte containing a solvent and a solute is provided, the solute containing dicarboxylic acid including a branched chain in α position or a salt thereof and the solvent being a mixed solvent composed of one kind or two kinds or more selected from alcohol-, alcohol ether-, amid-, sulfone-, sulfoxide- and ester-system solvents, characterized in that the content of dicarboxylic acid including a branched chain in α position or a salt thereof is 0.1-30 mass%, preferably 2.5-15 mass%, in terms of dicarboxylic acid including a branched chain in α position. In addition, a manufacturing method for dicarboxylic acid including a branched chain in α position and an ammonium salt thereof is provided. An electrolyte derived from dicarboxylic acid including a branched chain in α position and a salt thereof exhibit still better solubility and thermal stability in ethylene glycol. An obtained capacitor is advantageous in that it has a long life and excels in low temperature performance.

Description

  The present invention relates to an electrolytic solution for an aluminum electrolytic capacitor and a method for producing the core solute thereof, and more particularly, to an electrolytic solution for a medium-high pressure aluminum electrolytic capacitor and a method for producing the core solute.

  Conventionally, in an electrolytic solution of a medium / high pressure aluminum electrolytic capacitor, ethylene glycol is used as a main solvent, and an inorganic compound such as boric acid or ammonium pentaborate is used as a main solute. Such electrolytes have the problem of low electrical conductivity, and then used as the electrolyte main solute instead of linear diacids such as azelaic acid, sebacic acid, dodecanedioic acid or their ammonium salts. In addition, the above inorganic salt and the above organic acid may be blended to form a solute, but such an electrolytic solution has a problem of poor high-temperature thermal stability. Since the conductivity of the capacitor greatly decreases over a long period of time at a high temperature, the resistance value of the capacitor rises and adversely affects the life of the capacitor. Among them, boric acid or a salt thereof reacts with ethylene glycol at a high temperature to produce water, thus adversely affecting the life of the capacitor. Furthermore, it has a solubility as low as less than 6% at room temperature, which degrades the low temperature performance of the aluminum electrolytic capacitor.

  The first object of the present invention is to provide an electrolytic solution for medium- and high-pressure aluminum electrolytic capacitors, which has high thermal stability with respect to the poor high-temperature thermal stability of the current aluminum electrolytic capacitor electrolyte and low high-temperature conductivity. It is.

  The second object of the present invention is to provide a method for producing the core solute of the electrolyte.

  The first object of the present invention is achieved by the following technique.

  An electrolytic solution of an aluminum electrolytic capacitor containing a solvent and a solute, wherein the solute contains a dicarboxylic acid containing a branched chain at the α-position or a salt thereof, and the solvent is an alcohol, alcohol ether, amide, sulfone Is a mixed solvent formed from one or two or more types selected from solvents of the type, sulfoxide type, and ester type, and among them, the content of the dicarboxylic acid or salt thereof containing a branched chain at the α-position is: An aluminum electrolytic capacitor electrolyte characterized in that it is 0.1 to 30% by mass, preferably 2.5 to 15% by mass, of a dicarboxylic acid containing a branched chain at the α-position.

Preferably, the dicarboxylic acid containing a branched chain at the α-position has the following chemical formula 1 (Formula 1).
(In the above formula, R ₁ represents a hydrocarbon group having 1 to 20 carbon atoms or a hydrogen atom, and this hydrocarbon group may be linear or branched, saturated or unsaturated, In addition, the main chain and the branched chain may contain an ether group, an ester group, a cyano group, an amide group, a hydroxy group, a carboxyl group, and the like.
R ₂ represents a hydrocarbon group having 1 to 20 carbon atoms, and this hydrocarbon group may be linear or branched, and may be saturated or unsaturated. Further, the main chain and the branched chain may include an ether group, an ester group, a cyano group, an amide group, a hydroxyl group, or a carboxyl group.
n is an integer of 2-15. )

  Preferably, the dicarboxylate containing a branched chain at the α-position is a salt formed from a dicarboxylic acid containing a branched chain at the α-position and ammonia or an amine.

  Preferably, the solvent is one or a mixture of two selected from ethylene glycol or γ-butyrolactone.

  Preferably, the electrolyte solution may further contain at least one selected from hypophosphorous acid, phosphorous acid, phosphoric acid, phosphoric acid monoalkyl ether, or ammonia or an amine salt thereof, The total content is 0.05 to 5% by mass, preferably 0.1 to 3% by mass.

  Preferably, the electrolyte solution further includes one or a mixture of two or more selected from nitro compounds such as p-nitrophenol, p-nitrobenzyl alcohol, o-nitroanisole, m-nitroacetophenone, and p-nitrobenzenecarboxylic acid. The total content thereof may be 0.05 to 15% by mass, preferably 0.1 to 4% by mass.

  Preferably, the electrolyte solution further contains another organic acid or an ammonium salt thereof such as boric acid or ammonium pentaborate, sebacic acid, azelaic acid, benzenecarboxylic acid, adipic acid, dodecanedioic acid, 1,6-dodecane. It may be at least one acid selected from diacids and 1,7-sebacic acid or an ammonium salt thereof, and the total content thereof is 1 to 20% by mass.

  Preferably, the electrolytic solution may further contain a polymer compound capable of improving a spark voltage, for example, polyethylene glycol, polyvinyl alcohol, polyvinyl alcohol borate, polyvinyl alcohol phosphate, polyvinyl pyrrolidone, and the total content thereof. The amount is usually 0.2 to 15% by mass, preferably 0.5 to 10% by mass.

  Preferably, the dicarboxylic acid or salt thereof containing a branched chain at the α-position is preferably adipic acid or pimelic acid as the main chain, that is, the dicarboxylic acid containing a branched chain at the α-position according to the present invention is It is a derivative of adipic acid or pimelic acid. Since it contains a branched chain at the α-position, esterification and amidation are less likely to occur at high temperatures, and the decrease in electrolyte electrical conductivity is slow, and in addition, the main chain is adipic acid or pimelic acid. The solubility in glycol can be greatly improved.

  The second object of the present invention is achieved by the following technique.

The dicarboxylic acid containing a branched chain at the α-position according to the present invention is produced by the following chemical formula 2 (Chemical formula 2) (chemical reaction formulas (1), (2), (3)).
(here,
R ₁ is a hydrocarbon group having 1 to 20 carbon atoms or a hydrogen atom, and this hydrocarbon group may be linear or branched, saturated or unsaturated, The main chain or branched chain may contain an ether group, an ester group, a cyano group, an amide group, a hydroxy group, a carboxyl group, etc., preferably a hydrocarbon group having 1 to 8 carbon atoms or a hydrogen atom,
R ₂ is a hydrocarbon group having 1 to 20 carbon atoms, and this hydrocarbon group may be linear or branched, saturated or unsaturated, The branched chain may include an ether group, an ester group, a cyano group, an amide group, a hydroxy group, a carboxyl group, and the like, preferably a hydrocarbon group having 1 to 8 carbon atoms,
R ₃ and R ₄ may be the same or different and each represents a hydrocarbon group having 1 to 5 carbon atoms, preferably a hydrocarbon group having 1 to 2 carbon atoms,
X is a halogen atom such as chlorine, bromine, iodine, or a sulfone group;
n is an integer of 2 to 15, preferably 2 to 3. )

Preferably, the dicarboxylic acid containing a branched chain at the α-position is obtained by the following steps.
(1) Weighing the reactant A and the base so that the molar ratio of the reactant A and the base is 0.8 to 1.2: 1 and putting it in the reaction solvent;
(2) performing a heating reaction for 1 to 10 hours at a temperature selected from the range of 30 ° C to 150 ° C;
(3) after the reaction is finished, evaporating the solvent and neutralizing with a dilute acid;
(4) separating the oil layer and obtaining intermediate product B by distillation under reduced pressure;
(5) adding the intermediate product B to a solvent, adding an equimolar base, and further adding R ₂ X;
(6) performing a heating reaction for 2 to 50 hours at a temperature selected from the range of 60 ° C to 200 ° C;
(7) after the reaction is finished, evaporating the solvent and neutralizing with acid neutral;
(8) separating the oil layer and obtaining a desired ester by distillation under reduced pressure;
(9) The obtained ester is decomposed, acidified and washed with a strong base (KOH or NaOH) to obtain a dicarboxylic acid containing a branched chain at the α-position.

  Preferably, when it is necessary to form an ammonium salt, the dicarboxylic acid containing a branched chain at the α-position is reacted with ammonia or an amine to form an ammonium salt containing a branched chain at the α-position. Since the solution is less likely to be esterified or amidated, the electrolyte solution has better thermal stability.

  Based on the preferred result, the reactant A is preferably dimethyl (ethyl) adipate, dimethyl (ethyl) pimelate, dimethyl 2-methyl-adipate or the like.

  As a preferable result, the dicarboxylic acid containing a branched chain at the α-position according to the present invention is preferably adipic acid or a derivative of pimelic acid such as α-hexyladipic acid, α-butyladipic acid, α-methyl. -Α'-butyladipic acid, α-hexylpimelic acid and the like.

  The strong base used in the chemical reaction formulas (1) and (2) of Chemical Formula 2 (Chemical Formula 2) is alkali metal or alkaline earth metal alkoxide, alkali metal or alkaline earth metal hydride, alkali metal or alkaline earth. Selected from hydrocarbon group compounds of alkali metals, ammonia or amine compounds of alkali metals or alkaline earth metals, in which the ratio of base to reactant A in chemical reaction formula 1 is 0.8 to 1.2: 1, preferably 1.0. In ˜1.10: 1, the base is slightly overdose, and in the chemical reaction formula 2, the molar ratio of the base to the reactant B is 1: 1. In the two chemical reaction formulas, the bases may be the same or different, and examples of the base include sodium methoxide, sodium ethoxide, sodium hydride, potassium tert-butoxide, sodium triphenylmethane, and the like.

  The solvents of the chemical reaction formulas (1) and (2) of the chemical formula 2 (Chemical Formula 2) may be the same or different, and are alcohol-based, ether-based, alcohol ether-based, amide-based, sulfone-based, sulfoxide-based and the like. Preferred are methanol, ethanol, tert-butanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran and the like.

The reaction molar ratio of R ₂ X and B is theoretically 1: 1, preferably 0.8 to 1.2: 1, more preferably 1.0 to 1.1: 1, and R ₂ X is equivalent or slightly overdose.

  The reaction temperature of the chemical reaction formula (1) of the chemical formula 2 (Chemical Formula 2) is selected from the range of 30 ° C. to 150 ° C., preferably 40 ° C. to 80 ° C., and the reaction time is 1 to 10 hours, preferably 2 to 7 hours.

  The reaction temperature of the chemical reaction formula (2) of the chemical formula 2 (Chemical Formula 2) is selected from the range of 60 ° C. to 200 ° C., preferably 70 to 150 ° C., and the reaction time is 2 to 50 hours, preferably 5 to 30 hours.

After the reaction of the reactant A with the strong base and the solvent is completed, the reaction solution is neutralized with an acid and the oil layer is separated, and an intermediate product B is obtained by distillation under reduced pressure. Then, the intermediate product B is added to a solvent and a strong base, and further reacted with R ₂ X. The reaction solution is neutralized with an acid, an oil layer is separated, and an ester is obtained by distillation under reduced pressure. The ester is decomposed into an acidic form by concentrated NaOH or KOH, and after acidification, it is washed to obtain a dicarboxylic acid containing a branched chain at the α-position according to the present invention. The dicarboxylic acid is reacted with ammonia or an amine to form an ammonium salt. The dicarboxylic acid or salt becomes a medium-high pressure solute according to the present invention.

  The technical means provided based on the present invention has several advantages over the prior art.

  An electrolytic solution obtained from a dicarboxylic acid containing a branched chain at the α-position or a salt thereof according to the present invention has better solubility and thermal stability in ethylene glycol.

  The medium-high pressure aluminum electrolytic capacitor containing the electrolytic solution has an advantage of having a long life and excellent low-temperature performance. In the embodiments of the present invention, specific effects of the present invention will be described in detail and analyzed.

  Hereinafter, in order to further explain the contents of the present invention, the present invention will be described in detail based on specific examples.

Example 1
Diethyl adipate 70 g (0.4 mol) was charged into a 500 ml three-necked flask, 210 g of diethylene glycol dimethyl ether was added, and 23 g (0.43 mol) of sodium methoxide was added with stirring. After the end of the solvent was evaporated. The residue was neutralized with H ₂ SO ₄ and the oil layer was separated, and 40 g of intermediate product B was obtained by distillation under reduced pressure. Further, 140 g of tert-butanol was added, and 49 g of bromohexane was added dropwise under reflux (80-85 ° C.) to react for 24 hours. After the reaction was completed, tert- butanol was evaporated, neutralized neutralized with H ₂ SO _4, and especially the oil layer was distilled under reduced pressure using concentrated NaOH solution to decompose the acid form by heating. After neutralizing with H ₂ SO ₄ , washing and drying were performed to obtain 47 g of 2-hexyladipic acid. The total yield is about 51%.

Example 2
Diethyl adipate 70 g (0.4 mol) was charged into a 500 ml three-necked flask, 210 g of diethylene glycol dimethyl ether was added, and 23 g (0.43 mol) of sodium methoxide was added with stirring. After the end of the solvent was evaporated. The residue is neutralized with H ₂ SO ₄ and the oil layer is separated, and 41 g of intermediate product B is obtained by distillation under reduced pressure. , 140 g of tert-butanol was added, and 42 g of bromobutane was added dropwise under reflux (80-85 ° C.) to react for 24 hours. After the reaction was completed, tert-butanol was distilled off, and neutralized with H ₂ SO ₄ . The oil layer was separated, distilled under reduced pressure, and decomposed to the acidic form using concentrated NaOH solution by heating. After neutralizing with H ₂ SO ₄ , washing and drying were performed to obtain 37 g of 2-butyladipic acid. The yield is about 46%.
The obtained acid is reacted with ammonia to form an ammonium salt, which is prepared into an ethylene glycol solution to obtain an electrolytic solution. In order to explain the effect, Table 1 shows the results compared with a conventional ethylene glycol solution of ammonium sebacate.

Example 3
An ammonium salt of the acid obtained in Example 1 was prepared to prepare 250 g of a 5% ethylene glycol solution, and 0.1% ammonium hypophosphite and 0.4% p-nitrobenzyl alcohol were further added to prepare an electrolytic solution. . The obtained electrolyte solution was charged into a 500 ml stainless steel bottle, sealed, and kept at 105 ° C. to measure each parameter. The results are shown in Table 2.

Comparative Example 1
To 250 g of 5% ammonium sebacate ethylene glycol solution, 0.1% ammonium hypophosphite and 0.4% p-nitrobenzyl alcohol were added, and the mixture was placed in a 500 ml stainless steel bottle, sealed, and kept at 105 ° C. for measurement. The results are shown in Table 2.

  The results of analyzing the data in Tables 1 and 2 are as follows.

  The ammonium salt of the acid obtained in Example 1 can be prepared in a 20% ethylene glycol solution at room temperature and a clear solution is obtained. In contrast, when ammonium sebacate was prepared in a 10% ethylene glycol solution, the solute precipitated at room temperature, so the solute according to the present invention has better solubility in the ethylene glycol solution.

  The initial conductivity value of the electrolytic solution obtained in Example 3 is 1610 μS / cm at 30 ° C., but since the electrical conductivity of the electrolytic solution of Comparative Example 1 is 2010 μS / cm at 30 ° C., the initial value is Comparative Example 1 The electrolytic solution is higher. After constant temperature at 105 ° C. for 500 hours, the conductivity of Example 3 electrolyte was reduced by 35% to be 1040 μS / cm at 30 ° C., but Comparative Example 1 was the same so that it was 690 μS / cm. % Decreased. After 105 ° C. and 1172 hours, the electrolyte of Example 3 decreased by 43% so that the conductivity at 30 ° C. was 921 μS / cm, but Comparative Example 1 was 598 μS / cm under the same conditions. Decreased by 70%. Compared with an electrolytic solution based on a 5% ethylene glycol solution of ammonium sebacate, the electrolytic solution based on a 5% ethylene glycol solution of an ammonium salt of an acid according to the present invention has a relatively slow decrease in conductivity. Even though the electrolyte based on ammonium sebacate has a higher initial value of conductivity, the electrolyte based on the ammonium salt of the acid according to the present invention has a higher conductivity after the temperature is maintained. From the above, it can be seen that the electrolytic solution obtained from the acid according to the present invention and its ammonium salt has better thermal stability.

The foregoing embodiments are the best modes for carrying out the present invention, and the present invention is not limited to these embodiments. In short, various modifications made without impairing the gist of the present invention still belong to the technical scope of the present invention.

Claims (3)

A method for producing a dicarboxylic acid containing a branched chain at the α-position,
The dicarboxylic acid containing a branched chain at the α-position is represented by the following chemical formula 3 (Chemical Formula 3):
(In the above formula,
R ₁ is a hydrocarbon group having 1 to 20 carbon atoms or a hydrogen atom,
R ₂ is a hydrocarbon group having 1 to 20 carbon atoms,
n is an integer of 2-15. )
And,
Including three reactions of the following chemical formula 4
(here,
R ₁ is a hydrocarbon group having 1 to 20 carbon atoms or a hydrogen atom,
R ₂ is a hydrocarbon group having 1 to 20 carbon atoms,
R ₃ and R ₄ are hydrocarbon groups having 1 to 5 carbon atoms,
X is a chlorine, bromine, iodine or sulfone group,
n is an integer of 2-15. )
A process for producing a dicarboxylic acid containing a branched chain at the α-position. (1) Weighing the reactant A and the base so that the molar ratio of the reactant A and the base is 0.8 to 1.2: 1 and putting it in the reaction solvent;
(2) performing a heating reaction for 1 to 10 hours at a temperature selected from the range of 30 ° C to 150 ° C;
(3) after the reaction is finished, evaporating the solvent and neutralizing with a dilute acid;
(4) separating the oil layer and obtaining intermediate product B by distillation under reduced pressure;
(5) adding the intermediate product B to a solvent, adding an equimolar base, and further adding R ₂ X;
(6) performing a heating reaction for 2 to 50 hours at a temperature selected from the range of 60 ° C to 200 ° C;
(7) after the reaction is finished, evaporating the solvent and neutralizing with acid neutral;
(8) separating the oil layer and obtaining an ester compound by distillation under reduced pressure;
(9) The obtained ester compound is decomposed, acidified and washed with a strong base, and then a dicarboxylic acid containing a branched chain at the α-position is obtained;
A dicarboxylic acid containing a branched chain at the α-position is produced by a production method comprising:
The method for producing a dicarboxylic acid containing a branched chain at the α-position according to claim 1. The salt of a dicarboxylic acid containing a branched chain at the α-position is a salt formed from a dicarboxylic acid containing a branched chain at the α-position and ammonia or an amine.
The aluminum electrolytic capacitor electrolyte according to claim 1 or 2, wherein