Modifier for capacitor electrolyte containing (meth)acrylate, electrolyte for aluminum electrolytic capacitor using same, and aluminum electrolytic capacitor

Abstract

To provide a modifier for an electrolytic solution for a capacitor, which has an excellent effect of improving withstand voltage.SOLUTION: A capacitor electrolytic solution with excellent withstand voltage characteristics can be obtained by using, as a modifier, polyoxyalkylene (poly) glyceryl ether (meth) acrylate in which the terminal group of polyoxyalkylene (poly) glyceryl ether is modified with (meth) acrylate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a modifier for a capacitor electrolyte, and an electrolyte and an electrolytic capacitor using the same. [Background technology]

[0002] Aluminum electrolytic capacitors are made by winding an anode electrode foil, which has an insulating oxide layer formed on the surface of roughened aluminum, and a cathode electrode foil for current collection, with electrolytic paper between them, to form a capacitor element, which is then impregnated with an electrolyte and housed in an outer case. The electrolyte is inserted between the dielectric layer formed on the anode foil and the cathode foil for current collection, and its resistance is inserted in series with the electrolytic capacitor, and it is known that the characteristics of the electrolyte are a major factor that determines the characteristics of the capacitor.

[0003] Generally, electrolytes for aluminum electrolytic capacitors are prepared by dissolving a higher dicarboxylic acid or its ammonium salt, boric acid or its ammonium salt, and a polyhydric alcohol such as mannitol in an organic solvent such as ethylene glycol or γ-butyrolactone. Boric acid and polyhydric alcohols form ester compounds, and their structural properties are known to improve the withstand voltage of the electrolyte (Patent Document 1). It is also known that adding polyethylene glycol or polyethylene glycol diacrylate to the electrolyte can improve the withstand voltage (Patent Documents 2 and 3). However, in recent years, there has been an increasing demand for safety in aluminum electrolytic capacitors for electronic devices using switching power supplies. Aluminum electrolytic capacitors used in switching power supplies may be subjected to overvoltage due to unstable power supply. This can lead to capacitor rupture, fire, or combustion. To prevent this, it is necessary to further improve the spark voltage, i.e., the withstand voltage, of electrolytes for electrolytic capacitors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 09-017697 [Patent Document 2] Japanese Patent Application Publication No. 62-268121 [Patent Document 2] Japanese Patent Application Publication No. 11-074161 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a modifier for a capacitor electrolyte that is excellent in improving the withstand voltage. [Means for solving the problem]

[0006] The present inventors have found that a capacitor electrolyte with excellent voltage resistance characteristics can be obtained by using polyoxyalkylene (poly)glyceryl ether (meth)acrylate, in which the terminal group of polyoxyalkylene (poly)glyceryl ether is modified with (meth)acrylate, as a modifier, and have completed the present invention. [Effects of the Invention]

[0007] By using the modifier for capacitor electrolyte of the present invention, it is possible to produce an electrolyte for an aluminum electrolytic capacitor that has excellent withstand voltage characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes in more detail the embodiments for carrying out the present invention, but the scope of the present invention is not limited to these embodiments, and the present invention also includes embodiments to which modifications and the like are added as long as they do not deviate from the spirit of the present invention. Note that the range "to" includes the upper and lower limits.

[0009] The polyoxyalkylene (poly)glyceryl ether (meth)acrylate (hereinafter referred to as (meth)acrylate) used in the modifier of the present invention is a compound in which a polyoxyalkylene (poly)glyceryl ether and acrylic acid or methacrylic acid are ester-bonded.

[0010] The polyoxyalkylene (poly)glyceryl ether is a compound in which alkylene oxide is added to the hydroxyl groups of (poly)glycerin. Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide. It is particularly preferable to use one or more selected from ethylene oxide and propylene oxide, and it is more preferable to set the molar ratio of ethylene oxide in the alkylene oxide to 50% or more.

[0011] The (poly)glycerin constituting the polyoxyalkylene (poly)glyceryl ether has a structure in which hydroxyl groups of glycerin are ether-bonded by dehydration condensation, and the ether bond may be either linear or branched, and may contain a cyclic compound condensed within the molecule. The (poly)glycerin used preferably has an average degree of polymerization of 1 to 20, more preferably 2 to 10. Here, the average degree of polymerization is the average degree of polymerization (n) of the (poly)glycerin calculated from the hydroxyl value (OHV) by end group analysis. More specifically, the average degree of polymerization (n) is calculated from the following formulas (Formula 1) and (Formula 2). (Formula 1) Molecular weight=74n+18 (Formula 2) OHV=56110(n+2) / molecular weight The OHV in Equation 2 above is a numerical value that indicates the number of hydroxyl groups (OH groups) contained in (poly)glycerin, and refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid required to acetylate the free OH groups contained in 1 g of (poly)glycerin. The number of milligrams of potassium hydroxide is calculated in accordance with the "Standard Methods for the Analysis of Fats, Oils, and Related Materials, 2013 Edition," compiled by the Japan Oil Chemists' Society. Specific examples of (poly)glycerin include glycerin, diglycerin, triglycerin, tetraglycerin, hexaglycerin, and decaglycerin. Commercially available products include diglycerin S, PGL-S, polyglycerin #310, polyglycerin #500, and polyglycerin #750 (all manufactured by Sakamoto Pharmaceutical Co., Ltd.).

[0012] The polyoxyalkylene (poly)glyceryl ether preferably has an average addition number of alkylene oxides (AO) per OH group of (poly)glycerin of 5 to 30. By setting the average addition number of AO per OH group to 5 to 30, excellent voltage resistance characteristics can be obtained. Specific examples of polyoxyalkylene (poly)glyceryl ethers include polyoxyethylene (20) diglyceryl ether, polyoxyethylene (40) diglyceryl ether, polyoxyethylene (60) diglyceryl ether, polyoxyethylene (80) diglyceryl ether, polyoxyethylene (100) diglyceryl ether, polyoxyethylene (120) diglyceryl ether, polyoxyethylene (60) tetraglyceryl ether, polyoxyethylene (120) tetraglyceryl ether, polyoxyethylene (60) Examples of suitable glyceryl ethers include, but are not limited to, decaglyceryl ether, polyoxyethylene(120) decaglyceryl ether, polyoxypropylene(24) diglyceryl ether, polyoxypropylene(14) polyoxyethylene(100) diglyceryl ether, polyoxypropylene(25) polyoxyethylene(45) diglyceryl ether, polyoxypropylene(24) polyoxyethylene(60) tetraglyceryl ether, and polyoxypropylene(24) polyoxyethylene(240) decaglyceryl ether.

[0013] There are no particular limitations on the method for producing the (meth)acrylate of the present invention. Examples include a dehydration esterification method in which (meth)acrylic acid is reacted with the terminal hydroxyl groups of a polyoxyalkylene (poly)glyceryl ether obtained by addition reaction of a given amount of alkylene oxide to a specific (poly)glycerin by a known method, thereby obtaining an esterified product while removing the generated water from the system, and a transesterification method in which a (meth)acrylic acid ester of a lower alcohol is reacted with the terminal hydroxyl groups of the polyoxyalkylene (poly)glyceryl ether, thereby obtaining an esterified product while removing the generated lower alcohol from the system.

[0014] The electrolyte solution of the present invention preferably contains polyoxyalkylene (poly)glyceryl ether (meth)acrylate in an amount of 1 to 30% by weight, more preferably 3 to 25% by weight, and most preferably 5 to 20% by weight. A (meth)acrylate content of 1 to 30% by weight leads to an improvement in the withstand voltage of the aluminum electrolytic capacitor.

[0015] In addition to (meth)acrylate, the electrolytic solution of the present invention may contain various organic solvents, electrolytes, and additives. Examples of organic solvents include, but are not limited to, ethylene glycol, γ-butyrolactone, and glycerin. Examples of electrolytes include organic acids, inorganic acids, and salts thereof. Examples of organic acids and salts thereof include formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-vinylhexadecene-1,16-dicarboxylic acid, maleic acid, benzoic acid, phthalic acid, and their ammonium salts and amine salts. Examples of inorganic acids and salts thereof include, but are not limited to, carbonic acid, hypophosphorous acid, phosphorous acid, phosphoric acid, boric acid, perchloric acid, and their ammonium salts and amine salts. Examples of additives include, but are not limited to, polyhydric alcohols such as mannitol, hydrophilic polymeric compounds such as polyvinyl alcohol and polyvinylpyrrolidone, metal oxides such as silicon dioxide and aluminosilicate, nitro compounds such as p-nitrobenzoic acid and p-nitrophenol, and water. [Example]

[0016] Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. Examples and comparative examples of the present invention are shown below, where % is by weight.

[0017] Example 1 A reaction vessel equipped with a thermometer, stirrer, air inlet, and Dean-Stark reflux apparatus was charged with 269.6 g (0.141 mol) of polyoxyethylene (40) diglyceryl ether, 300.0 g of toluene, 15.0 g of p-toluenesulfonic acid, 0.3 g of hydroquinone monomethyl ether, 0.1 g of copper(II) chloride, 0.3 g of sodium hypophosphite, and 60.8 g (0.843 mol) of acrylic acid. The mixture was heated to a toluene reflux atmosphere with stirring and air blown in, and the dehydration esterification reaction was carried out over approximately 6 hours. After completion of the reaction, the mixture was washed with alkaline water and water, and the toluene in the organic layer was removed by vacuum distillation to obtain polyoxyethylene (40) diglyceryl ether acrylate (2G40EO4A). An electrolyte solution was prepared by mixing 2G40EO4A as a modifier with an electrolyte (diammonium 1,7-octanedicarboxylate), ethylene glycol (EG), and ion-exchanged water in the ratios shown in Table 1. The performance of the electrolyte solution was evaluated by measuring its withstand voltage and electrical conductivity, and the results are shown in Table 1.

[0018] (Electrolyte voltage resistance) The prepared electrolyte was heated to 85°C, and the rated dielectric strength was 665V and the capacitance was 0.45μF / cm 2 The anode aluminum oxide foil (104HD5B-665Vf: manufactured by Nippon Capacitor Industrial Co., Ltd.) was immersed in the electrolyte, and a current density of 0.6 mA / cm was applied using a DC stabilized power supply (PL-650-0.1: manufactured by Matsusada Precision Co., Ltd.). 2 A current was applied to the anode foil at a voltage rise rate of 1.7 V / s. The withstand voltage was evaluated by monitoring the current-voltage curve, and the voltage value at which the current value exceeded 5 mA was read as the breakdown voltage.

[0019] (Electrolyte conductivity) The temperature of the prepared electrolyte solution was adjusted to 25° C., and the electrical conductivity was measured using a conductivity meter (DS-52, manufactured by Horiba, Ltd.).

[0020] Example 2 257.8 g (0.0563 mol) of polyoxyethylene (100) diglyceryl ether, 270.0 g of toluene, 13.5 g of p-toluenesulfonic acid, 0.3 g of hydroquinone monomethyl ether, 0.1 g of copper (II) chloride, 0.3 g of sodium hypophosphite, and 24.4 g (0.338 mol) of acrylic acid were charged, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain polyoxyethylene (100) diglyceryl ether acrylate (2G100EO4A). Using 2G100EO4A as a modifier, the physical properties of the electrolyte were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0021] Example 3 240.3 g (0.0447 mol) of polyoxyethylene (100) polyoxypropylene (14) diglyceryl ether, 250.0 g of toluene, 17.5 g of p-toluenesulfonic acid, 0.3 g of hydroquinone monomethyl ether, 0.1 g of copper (II) chloride, 0.3 g of sodium hypophosphite, and 19.3 g (0.268 mol) of acrylic acid were charged, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain polyoxyethylene (100) polyoxypropylene (14) diglyceryl ether acrylate (2G14PO100EO4A). Using 2G14PO100EO4A as a modifier, the physical properties of the electrolyte were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0022] Example 4 637.6 g (0.216 mol) of polyoxyethylene (60) tetraglyceryl ether, 577.0 g of toluene, 28.2 g of p-toluenesulfonic acid, 0.7 g of hydroquinone monomethyl ether, 0.3 g of copper (II) chloride, 0.7 g of sodium hypophosphite, and 135.2 g (1.88 mol) of acrylic acid were charged, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain polyoxyethylene (60) tetraglyceryl ether acrylate (4G60EO6A). Using 4G60EO6A as the modifier, the physical properties of the electrolyte were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0023] Example 5 672.3 g (0.198 mol) of polyoxyethylene (60) decaglyceryl ether, 654.6 g of toluene, 32.0 g of p-toluenesulfonic acid, 0.8 g of hydroquinone monomethyl ether, 0.3 g of copper (II) chloride, 0.8 g of sodium hypophosphite, and 255.8 g (3.55 mol) of acrylic acid were charged, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain polyoxyethylene (60) decaglyceryl ether acrylate (10G60EO12A). Using 10G60EO12A as a modifier, the physical properties of the electrolyte were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0024] Example 6 242.8 g (0.0418 mol) of polyoxyethylene (120) decaglyceryl ether, 270.0 g of toluene, 13.5 g of p-toluenesulfonic acid, 0.3 g of hydroquinone monomethyl ether, 0.1 g of copper (II) chloride, 0.3 g of sodium hypophosphite, and 54.3 g (0.753 mol) of acrylic acid were charged, and the reaction and purification were carried out under the same conditions as in Example 1 to obtain polyoxyethylene (120) decaglyceryl ether acrylate (10G120EO12A). Using 10G120EO12A as a modifier, the properties of the electrolyte were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0025] Example 7 The properties of the electrolyte solution were evaluated in the same manner as in Example 1, except that 20% of 2G40EO4A was used as the modifier. The results are shown in Table 1.

[0026] (Comparative Example 1) An electrolyte solution was prepared in the same manner as in Example 1, except that no modifier was added, and the withstand voltage and electrical conductivity were evaluated. The results are shown in Table 1.

[0027] (Comparative Example 2) The properties of the electrolyte solution were evaluated in the same manner as in Example 1, except that the modifier was changed to 5% polyoxyethylene (40) diglyceryl ether (2G40EO). The results are shown in Table 1.

[0028] (Comparative Example 3) The properties of the electrolyte solution were evaluated in the same manner as in Example 1, except that the modifier was changed to 20% polyoxyethylene (40) diglyceryl ether (2G40EO). The results are shown in Table 1.

[0029] Comparative Example 4 The properties of the electrolyte solution were evaluated in the same manner as in Example 1, except that the modifier was changed to 5% polyethylene glycol diacrylate (PEG-2A, PEG polymerization degree 9). The results are shown in Table 1.

[0030] [Table 1]

[0031] In Examples 1 to 6, which used 5% polyoxyalkylene polyglyceryl ether acrylate as a modifier, an improvement in withstand voltage of 10 V or more was observed compared to Comparative Example 1, which did not contain any modifier. An electrolyte solution with higher withstand voltage and conductivity was obtained compared to Comparative Example 2, which used the same amount of 2G40EO. Furthermore, in Example 7, in which the amount of 2G40EO4A was increased to 20%, the withstand voltage value was 517 V, and an electrolyte solution with higher withstand voltage and conductivity was obtained compared to Comparative Example 3, which used the same amount of 2G40EO. It is believed that the acrylate modification of the terminal hydroxyl groups causes polymerization between the additives, resulting in better withstand voltage characteristics. Furthermore, in Examples 1 to 6, electrolyte solutions with higher withstand voltage were obtained compared to Comparative Example 4, which used the same amount of PEG-2A. These results demonstrate that the use of polyoxyalkylene (poly)glyceryl ether (meth)acrylate as a modifier can produce electrolyte solutions with excellent withstand voltage characteristics.

Claims

1. An electrolyte for aluminum electrolytic capacitors that uses polyoxyalkylene (poly)glyceryl ether (meth)acrylate as a modifier, which is polyoxyalkylene (poly)glyceryl ether whose terminal group has been modified with (meth)acrylate.

2. An aluminum electrolytic capacitor using the electrolytic solution according to claim 1.

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