JP2014112651A - Voltage resistance improver of electrolyte for driving electrolytic capacitor, and electrolyte for driving electrolytic capacitor containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage resistance improver of an electrolyte for driving an electrolytic capacitor and the electrolyte for driving an electrolytic capacitor containing the same.SOLUTION: For polyglycerol whose glycerin concentration is 10 wt% or less, whose diglycerol concentration is 20 wt% or less, and whose average polymerization degree calculated from a hydroxyl value is from 3 to 20, polyoxyethylene polyglyceryl ether formed by addition of an ethylene oxide is used as an additive agent of an electrolyte for driving an electrolytic capacitor.

Description

  The present invention relates to a voltage resistance improver for an electrolytic solution for driving an electrolytic capacitor, and an electrolytic solution for driving an electrolytic capacitor containing the same.

  Electrolytic capacitors consist of an anode electrode foil in which an insulating oxide film layer is formed on the surface of a roughened valve metal foil such as aluminum or tantalum, and a cathode electrode foil for current collection through electrolytic paper. The capacitor element is wound to form a structure, impregnated with an electrolytic solution, and housed in an exterior case. The electrolyte intervenes between the dielectric layer formed on the anode foil and the cathode foil for current collection, and the resistance is inserted in series with the electrolytic capacitor. The characteristics of the electrolyte influence the characteristics of the electrolytic capacitor. It is known to be a major factor.

  A general electrolyte solution is composed of a composition in which an organic solvent such as ethylene glycol or γ-butyrolactone is the main component and an electrolyte such as sebacic acid or ammonium borate is dissolved. The agent is added. As an additive of this electrolytic solution, it is known that the higher the molecular weight, the higher the withstand voltage is improved because the dielectric breakdown is suppressed by protecting the oxide film of the electrode foil. In recent years, as the operating voltage of in-vehicle electrical equipment and digital home appliances has increased, the electrolytic solution for driving electrolytic capacitors must satisfy cold region specifications while having high voltage resistance. Improvement of the low temperature fluidity of the liquid is desired.

  Generally, as an electrolytic solution for driving an electrolytic capacitor for medium to high pressure, a solvent composed of ethylene glycol, an additive for improving voltage resistance, polyethylene glycol (Patent Document 1), polyoxyethylene glyceryl ether (Patent Document 2, Patent Document 3) and polyoxyethylene diglyceryl ether (Patent Document 4) are disclosed. Although these have an effect of improving withstand voltage, since the melting point increases with increasing molecular weight, the amount of addition is limited to satisfy the low temperature characteristics of the electrolytic solution for driving an electrolytic capacitor. Furthermore, although polyoxyalkylene polyglyceryl ether having a higher molecular weight (Patent Document 5) has also been shown to improve voltage endurance, it depends on the degree of polyglycerin polymerization and composition, and the difference in the number of added polyoxyalkylenes. However, there are cases where the low-temperature fluidity of the electrolytic solution for driving the electrolytic capacitor is deteriorated, or the improvement effect of the voltage resistance of the electrolytic capacitor is difficult to obtain. Therefore, there has been a demand for an additive that exhibits high solubility with respect to ethylene glycol and that can improve the voltage resistance without deteriorating the low-temperature fluidity of the electrolytic solution for driving an electrolytic capacitor.

JP 1987-268121 A JP 2004-165262 A JP 2006-12984 A Japanese Patent Publication No. 7-70444 Japanese Patent No. 2925185

  An object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor that has excellent voltage resistance and good low-temperature characteristics.

  Polyoxyl obtained by adding ethylene oxide to polyglycerin having a glycerin concentration of 10% by weight or less, a diglycerin concentration of 20% by weight or less, and an average degree of polymerization calculated from a hydroxyl value of 3 to 20. By using ethylene polyglyceryl ether as an additive for an electrolytic solution for driving an electrolytic capacitor, an electrolytic solution for driving an electrolytic capacitor having an effect of improving voltage resistance was found, and the present invention was completed.

  By using the voltage resistance improver of the electrolytic solution for driving an electrolytic capacitor of the present invention, an electrolytic capacitor excellent in voltage resistance and low temperature characteristics can be manufactured.

  Although the form for implementing this description is demonstrated in detail below, the scope of the present invention is not limited to this embodiment, and the change etc. were added in the range which does not impair the meaning of the present invention. The form also belongs to the present invention.

  The polyglycerin used in the polyoxyethylene polyglyceryl ether of the present invention is a dehydration condensation reaction of glycerin, synthesis using a glycerin-related substance such as glycidol, epichlorohydrin, glycerin halohydrin, or recovery of synthetic glycerin from a glycerin distillation residue. In general, it is obtained by a method in which a small amount of an alkali catalyst is added to glycerin and heated to a high temperature of 200 ° C. or higher and polycondensed while removing water to be purified. The reaction is a sequential intermolecular dehydration reaction, and a high polymer is produced in sequence, but the reaction composition is not homogeneous and becomes a complex mixed composition such as unreacted glycerin, diglycerin, triglycerin, and tetraglycerin. The higher the reaction temperature or the longer the reaction time, the more the reaction shifts to the higher degree of polymerization. In addition, since unreacted glycerin can be distilled by vacuum distillation and diglycerin can be distilled by molecular distillation, diglycerin is generally used as a high-purity product and has a degree of polymerization higher than that. As the glycerin, a complex multi-component mixture and a residue obtained by distilling glycerin and diglycerin are used.

  As an example, the polyglycerin composition is analyzed by weighing about 0.5 g of a polyglycerin sample and about 0.05 g of methyl palmitate (first grade reagent; Kishida Chemical) as an internal standard substance, and pyridine (special grade reagent; Chemistry) Dissolve them in about 1.8 ml, then inject 0.2 ml of TMS-HT (reagent; Tokyo Kasei Kogyo) into 20 μl of this solution. After reaction in a warm bath, 1 μL of the supernatant liquid is subjected to the following analysis. It is determined by providing.

Gas chromatograph: GC-14B (manufactured by Shimadzu Corporation)
Column: OV-1 (manufactured by GL Sciences, inner diameter 3 mm, length 1.5 m)
Column temperature: 100 ° C. to 350 ° C. (temperature increase rate 10 ° C./min)
Carrier gas: helium (50ml / min)
Injection part temperature: 350 ° C
Detector temperature: 350 ° C
Detector: FID

  The polyglycerin used in the polyoxyethylene polyglyceryl ether of the present invention has a glycerin concentration of 10% by weight or less, a diglycerin concentration of 20% by weight or less, preferably a glycerin concentration of 5% by weight or less, and a diglycerin concentration of 15% by weight. % Or less. When polyglycerin having a glycerin concentration exceeding 10% by weight or polyglycerin having a diglycerin concentration exceeding 20% by weight is used, the low-temperature fluidity of polyoxyethylene polyglyceryl ether decreases, and the electrolytic capacitor There is a risk of lowering the withstand voltage characteristics.

The polyglycerin used in the polyoxyethylene polyglyceryl ether of the present invention is one having an average degree of polymerization calculated from the hydroxyl value of 3 to 20, preferably 4 to 10. Here, the average degree of polymerization is the average degree of polymerization (n) of polyglycerin calculated from the hydroxyl value by end group analysis. Specifically, the average degree of polymerization is calculated from the following formulas (Formula 1) and (Formula 2).
(Formula 1) Molecular weight = 74n + 18
(Formula 2) Hydroxyl value = 56110 (n + 2) / Molecular weight The hydroxyl value in the above (Formula 2) is a numerical value that is an index of the number of hydroxyl groups contained in polyglycerin, and is free contained in 1 g of polyglycerin. The number of milligrams of potassium hydroxide required to neutralize the acetic acid required to acetylate the hydroxyl group. The number of milligrams of potassium hydroxide is calculated in accordance with the Japan Oil Chemists 'Society, “Established by the Japan Oil Chemists' Society, Standard Oil Analysis Test Method (I), 2003 edition”.

  The number of moles of ethylene oxide used in the polyoxyethylene polyglyceryl ether of the present invention is 20 to 100 moles, preferably 25 to 90 moles, and more preferably 30 to 80 moles. When the added mole number of ethylene oxide is less than 20 moles, the withstand voltage characteristic of the electrolytic capacitor may be lowered. On the other hand, when it exceeds 100 moles, the low temperature fluidity of polyoxyethylene polyglyceryl ether is lowered.

  The viscosity at −10 ° C. of the polyoxyethylene polyglyceryl ether used in the present invention is less than 100,000 mPa · s, preferably less than 50,000 mPa · s, and more preferably less than 30,000 mPa · s. . When the viscosity at −10 ° C. exceeds 100,000 mPa · s, the crystallinity of polyoxyethylene polyglyceryl ether is increased, so that the solubility in ethylene glycol is lowered, which may lead to a decrease in the withstand voltage characteristics of the electrolytic capacitor. is there.

  The electrolytic solution for driving an electrolytic capacitor of the present invention comprises 0.5% to 50% by weight of polyoxyethylene polyglyceryl ether, preferably 1.0% to 40% by weight, and more preferably 5.0% by weight. Contains 30% by weight. If the content is less than 0.5% by weight, the effect of improving the withstand voltage of the electrolytic capacitor may be low. On the other hand, if the content exceeds 50% by weight, the low-temperature characteristics of the electrolytic solution for driving the electrolytic capacitor will deteriorate, and the electrolytic capacitor There is a risk that the withstand voltage characteristic of the battery may be lowered.

  The electrolytic solution for driving an electrolytic capacitor of the present invention contains polyoxyethylene polyglyceryl ether, an organic solvent, and an organic acid, an inorganic acid, or a salt thereof as a solute. Examples of the organic solvent include ethylene glycol and γ-butyrolactone. Examples of organic acids or salts thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid, 2- Examples thereof include butyloctanedioic acid and its ammonium salt, sodium salt, potassium salt, and amine salt. Furthermore, examples of the inorganic acid or a salt thereof include carbonic acid, hypophosphorous acid, phosphorous acid, phosphoric acid, boric acid, perchloric acid, and ammonium salts, sodium salts, potassium salts, and amine salts thereof. However, it is not limited to them.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited only to these Examples. In addition, the polyglycerol used for this synthesis | combination is the polyglycerol A to E shown in the following synthesis examples, and the average degree of polymerization calculated from a hydroxyl value is 4.5, 6, 10, 2, 4 respectively. is there. Examples of the present invention and comparative examples are shown below. However,% is based on weight.

(Measurement of viscosity of polyoxyethylene polyglyceryl ether)
For polyoxyethylene polyglyceryl ether, using an E-type viscometer DV-II + Pro (Brookfield), the measurement temperature was −10 ° C., spindle no. The viscosity was measured under the conditions of 42, rotor rotation speed 0.5 rpm. The measured value was a value one minute after the start of rotation of the rotor.

(Evaluation of low-temperature fluidity of ethylene glycol / polyoxyethylene polyglyceryl ether mixture)
80 g of ethylene glycol and 20 g of polyoxyethylene polyglyceryl ether were weighed and mixed with stirring at 80 ° C. or lower. For those that were uniformly compatibilized with ethylene glycol, it was determined whether the low-temperature fluidity when allowed to stand at −25 ° C. for 24 hours was any of the following criteria A to C. On the other hand, those not compatibilized with ethylene glycol were determined as D of the following criteria.

(Evaluation criteria for low temperature fluidity at -25 ° C)
A: Fluidity state B: White turbidity but fluidity state C: White turbidity, solidified state D: Incompatible state with ethylene glycol

(Withstand voltage measurement using electrolyte)
Ethylene glycol was used as a solvent, 2-butyloctanedioic acid / ammonium salt as a solute, ammonium hypophosphite as an additive, and polyoxyethylene polyglyceryl ether as a withstand voltage improver to prepare an electrolytic solution. The prepared electrolytic solution was heated to 85 ° C., and an anode foil having a rated film withstand voltage of 665 V and a capacitance of 0.45 μF / cm ² (manufactured by Nippon Denki Kogyo Co., Ltd.) was immersed in the electrolytic solution. A constant current was applied to the anode foil under the condition of a current density of 0.6 mA / cm ² using Kikusui Electronics Corporation. The withstand voltage was evaluated by measuring the time-voltage rise curve when a constant current was applied, reading the voltage at which spark or scintillation was first observed, and judging the withstand voltage according to the following index. In addition, the withstand voltage of the electrolyte without adding the withstand voltage improver was 427V.

(Indicator of improvement in withstand voltage against additive)
○: 10V or more Δ: 5V or more, less than 10V ×: less than 5V

(Synthesis of polyglycerol A to E)
A refined glycerin (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.) and sodium hydroxide as a catalyst are added to a four-necked flask equipped with a thermometer and a stirrer, and reacted at 250 ° C. under a nitrogen stream to obtain a polyglycerin composition. Obtained. Subsequently, this composition was distilled under reduced pressure to obtain polyglycerols A, B and D shown in Table 1. In addition, polyglycerol C and E were obtained as what does not implement a vacuum distillation process.

Example 1
350 g (1 mol) of polyglycerin A and 2 g of potassium hydroxide were added to a pressure-resistant container equipped with a heating device to form a nitrogen atmosphere. The temperature was raised to 120 ° C., 1760 g (40 mol) of ethylene oxide was added, and the mixture was reacted at 150 ° C. for 3 hours. Thereafter, the reaction product was cooled to 100 ° C., unreacted ethylene oxide gas was distilled off under reduced pressure, and further cooled to 80 ° C., after which the catalyst was neutralized and a polyoxy having a viscosity of −14440 mPa · s at −10 ° C. Ethylene polyglyceryl ether (PGEO1) was obtained. Next, 20 g of PGEO1 was mixed with 80 g of ethylene glycol, and the low temperature fluidity evaluation at −25 ° C. was performed. Subsequently, 10.0 g of 2-butyloctanedioic acid / ammonium salt was dissolved in 82.98 g of ethylene glycol. Thereto, 0.1 g of 20% by weight aqueous solution of ammonium hypophosphite and 5.0 g of PGEO1 were added, and the water content of the electrolyte was adjusted to 2 using a Karl Fischer moisture meter KF-100 (manufactured by Mitsubishi Chemical). Prepared to 0.0%. Withstand voltage measurement was performed using the obtained electrolyte solution. These results are shown in Table 2, Table 3, and Table 4.

(Examples 2 to 10)
10 was synthesized from PGEO2 in the same manner as in Example 1 except that the kind of polyglycerin and the number of added moles of ethylene oxide were changed, viscosity measurement at −10 ° C., and further, ethylene glycol / polyoxyethylene polyglyceryl ether mixed solution Low temperature fluidity evaluation, preparation of electrolyte solution, and measurement of withstand voltage were performed. These results are shown in Table 2, Table 3, and Table 4.

(Comparative Examples 1 to 4)
PGEO 11 to 14 were synthesized in the same manner as in Example 1 except that the type of polyglycerin and the number of moles of ethylene oxide added were changed, viscosity measurement at −10 ° C., and further, ethylene glycol / polyoxyethylene polyglyceryl ether mixed solution Low temperature fluidity evaluation, preparation of electrolyte solution, and measurement of withstand voltage were performed. These results are shown in Table 5, Table 6, and Table 7.

(Comparative Example 5)
Evaluation was performed in the same manner as in Example 1 except that polyoxyethylene glyceryl ether was used instead of polyoxyethylene polyglyceryl ether. These results are shown in Table 5, Table 6, and Table 7.

(Comparative Example 6)
Evaluation was conducted in the same manner as in Example 1 except that polyethylene glycol (number average molecular weight 400) was used instead of polyoxyethylene polyglyceryl ether. These results are shown in Table 5, Table 6, and Table 7.

(Comparative Example 7)
Evaluation was conducted in the same manner as in Example 1 except that polyethylene glycol (number average molecular weight 1000) was used instead of polyoxyethylene polyglyceryl ether. These results are shown in Table 5, Table 6, and Table 7.

(Comparative Example 8)
Evaluation was performed in the same manner as in Example 1 except that polyvinyl alcohol was used instead of polyoxyethylene polyglyceryl ether. These results are shown in Table 5, Table 6, and Table 7.

  Polyoxyl obtained by adding ethylene oxide to polyglycerin having a glycerin concentration of 10% by weight or less, a diglycerin concentration of 20% by weight or less, and an average degree of polymerization calculated from a hydroxyl value of 3 to 20. It has been clarified that by using ethylene polyglyceryl ether as an additive for an electrolytic solution for driving an electrolytic capacitor, an electrolytic solution exhibiting excellent low-temperature fluidity and having a high withstand voltage can be obtained.

  By using the polyoxyethylene polyglyceryl ether of the present invention as a voltage resistance improver for an electrolytic solution for driving an electrolytic capacitor, an electrolytic capacitor excellent in voltage resistance and low temperature characteristics can be produced.

Claims (5)

  Polyoxyl obtained by adding ethylene oxide to polyglycerin having a glycerin concentration of 10% by weight or less, a diglycerin concentration of 20% by weight or less, and an average degree of polymerization calculated from a hydroxyl value of 3 to 20. A voltage resistance improver for an electrolytic solution for driving an electrolytic capacitor, which is ethylene polyglyceryl ether.   The withstand voltage improver of the electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the number of moles of ethylene oxide added to polyglycerin is 20 to 100 moles.   3. The withstand voltage improver for an electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the viscosity at −10 ° C. is less than 100,000 mPa · s.   4. An electrolytic solution for driving an electrolytic capacitor, comprising 0.5% by weight to 50% by weight of the voltage resistance improver of the electrolytic solution for driving an electrolytic capacitor according to any one of claims 1 to 3.   The electrolytic capacitor driving electrolyte comprising the electrolytic solution for driving an electrolytic capacitor according to any one of claims 1 to 3, an organic solvent, and an organic acid, an inorganic acid, or a salt thereof as a solute. Electrolytic solution.