WO2012067097A1 - Fire retardant electrolytic capacitor - Google Patents

Abstract

In the present invention, microcapsules of a fire retardant are produced by encapsulating the fire retardant, which comprises a phosphate ester or a condensate thereof, in a resin that melts at or above 150°C, and the microcapsules of the fire retardant are added into a capacitor element. The resin that configures the microcapsule shells comprises at least one resin selected from: epoxy resin, phenol resin, polyphenylene sulfide, polyimide, polyaramide, melamine resin, polyruea, or polyurethane. As the fire retardant, for example, trimethyl phosphate, tritolyl phosphate, or cresyldiphenyl phosphate is used.

Description

Flame retardant electrolytic capacitor

The present invention relates to a flame retardant electrolytic capacitor that minimizes the combustion of the electrolytic capacitor during safety valve operation.

When an excessive electrical stress is applied to the electrolytic capacitor, the safety valve with an explosion-proof function operates, but there is a risk that the capacitor element will burn by igniting the gasified electrolyte due to a spark generated by a short circuit or the like. It was.

Therefore, as described in Patent Document 1, a technique is known in which a phosphoric acid ester is added to an electrolytic solution to impart flame retardancy and suppress the generation of combustible gas.

Japanese Patent Laid-Open No. 3-180014

However, the technique described in Patent Document 1 is that the phosphate ester disappears during the safety valve operation due to the hydrolysis of the phosphate ester, and the flame retardant effect cannot be sufficiently exhibited. However, when the electrode foil is attacked, the electrode foil is dissolved and the pressure resistance is lowered.

Thus, even though it has been known to use phosphate ester as a flame retardant, it is known that phosphate ester is microencapsulated and present in an electrolyte without hydrolysis for a long period of time. It wasn't.

With such a technical background, there has been a demand for the appearance of an electrolytic capacitor using a microcapsule that satisfies the following conditions and having a flame retardant added thereto.
(1) Even if it is in contact with moisture in the electrolytic solution for a long period of time, hydrolysis of the phosphoric ester within the shell and the moisture in the electrolytic solution is surely prevented without being dissolved or destroyed.
(2) The microcapsules existing in the capacitor are dissolved by self-heating due to the malfunction of the electrolytic capacitor, and the phosphate ester inside the shell is released.

The present invention has been proposed in order to solve the problems of the conventional techniques as described above. An object of the present invention is to prevent hydrolysis of phosphate ester over a long period of time by encapsulating a flame retardant comprising a phosphate ester or a condensate thereof in a microcapsule, and when the electrolytic capacitor becomes hot, An object of the present invention is to provide a flame retardant electrolytic capacitor in which a capsule is dissolved and a flame retardant is dissolved in an electrolytic solution to suppress combustion of a capacitor element.

In order to solve the above-mentioned problems, the electrolytic capacitor of the present invention is to prepare a microcapsule of a flame retardant by encapsulating a flame retardant comprising a phosphate ester or a condensate thereof in a resin that dissolves at 150 ° C. or higher. A microcapsule of a flame retardant is contained in a capacitor element.

Further, the resin constituting the shell of the microcapsule is at least one selected from an epoxy resin, a phenol resin, polyphenylene sulfide (hereinafter referred to as PPS), polyimide (hereinafter referred to as PI), polyaramid, melamine resin, polyurea or polyurethane. It is characterized by that.

And the moisture content contained in a capacitor | condenser element is 35 weight% or less, It is characterized by the above-mentioned.

The amount of the flame retardant added is 3 to 20% by weight with respect to the electrolytic solution.

Phosphate esters or condensates used as flame retardants are trimethyl phosphate, trihexyl phosphate, tri-n-butyl phosphate, triethyl phosphate, methyl polyphosphate, poly-n-butyl phosphate, ethyl polyphosphate, phosphorus It is characterized by being one or more of trityl acid, cresyl diphenyl phosphate.

According to the present invention, a microencapsulated flame retardant is produced by encapsulating a flame retardant composed of a phosphate ester or a condensate thereof in a resin that dissolves at 150 ° C. or higher. Prevents hydrolysis of flame retardants. In addition, by containing the microencapsulated flame retardant in the capacitor element, when the electrolytic capacitor becomes hot due to an abnormality such as a short circuit, the microcapsule dissolves and the flame retardant dissolves into the electrolyte. Suppresses the combustion of the capacitor element.

As the flame retardant microcapsules, those obtained by the following production method can be used.
(1) Chemical methods such as interfacial polymerization method and in-situ polymerization method (2) Physicochemical methods such as submerged drying method and coacervation method (3) Mechanical methods such as dry mixing method and spray drying method

As the shell of the microcapsule, among the above resins, PPS, PI, polyaramid, melamine resin, polyurea or polyurethane is preferable. These resins exhibit stable non-dissolving performance with respect to the solvent, solute, and phosphoric acid ester encapsulated therein. Therefore, when these resins are used, the flame retardant is not leaked into the electrolytic solution and hydrolyzed even after a long period of time, and the function as the flame retardant is not lost.

If the melting point of the shell material of the microcapsule is less than 150 ° C., the microcapsule may be destroyed or dissolved in the normal use state of the electrolytic capacitor. In addition, when the melting point of the shell material of the microcapsule exceeds the combustion temperature of the capacitor element, the flame retardant is added to the electrolyte solution without destruction or dissolution of the microcapsule when the electrolytic capacitor reaches an abnormally high temperature state. May not be released.

The size of the microcapsule is 0.02 to 100 μm, preferably 0.02 to 0.05 μm. When the thickness is 0.02 μm or less, it is difficult to produce a heat-resistant microcapsule. When the thickness exceeds 100 μm, the characteristics of the electrolytic capacitor, particularly the impedance characteristics in the high frequency region, are affected.

As the solvent used in the electrolytic solution of the present invention, a protic polar solvent, an aprotic polar solvent, and a mixture thereof can be used. Protic polar solvents include monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (ethylene glycol) Propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.). Examples of aprotic polar solvents include amides (N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, hexamethylphosphoricamide, etc.), lactones (γ-butyrolactone, δ-valerolactone, γ-valerolactone, etc.), sulfolanes (sulfolane, 3-methylsulfolane, 2 , 4-dimethylsulfolane, etc.), cyclic amides (N-methyl-2-pyrrolidone, etc.), carbonates (ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.), sulfoxides (dimethylsulfoxide, etc.) , -Imidazolidinone series [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di (n-propyl ) -2-imidazolidinone, etc.), 1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone, etc.)] and the like. Among these, use of γ-butyrolactone is preferable because impedance characteristics are improved, and use of ethylene glycol is preferable because voltage resistance characteristics are improved.

As the solute of the electrolytic solution used in the present invention, an organic acid or an inorganic acid or a salt thereof can be used alone or in combination.

Organic acids include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, enanthic acid, malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, Aliphatic dicarboxylic acids such as dodecanedioic acid, 1,6-decanedicarboxylic acid, undecanedioic acid, tridecanedioic acid, maleic acid, citraconic acid, and itaconic acid, benzoic acid, phthalic acid, salicylic acid, toluic acid, and pyromellitic acid Aromatic carboxylic acids such as can be used.

As the inorganic acid, boric acid, phosphoric acid, silicic acid and the like can be used.

Examples of the organic acid and inorganic acid salts mentioned above include ammonium salts, monoalkylamines such as ammonium, methylamine, ethylamine, and propylamine, dialkylamines such as dimethylamine, diethylamine, ethylmethylamine, and dibutylamine, and trimethylamine. , Trialkylamines such as triethylamine, tributylamine and ethyldiisopropylamine, quaternary ammonium salts such as tetramethylammonium, triethylmethylammonium and tetraethylammonium, imidazolium salts such as ethyldimethylimidazolium and tetramethylimidazolium, ethyldimethyl Imidazolinium salts such as imidazolinium and tetramethylimidazolinium can be used. In addition, phosphonium salts and the like can be used.

In addition, in order to stabilize the life characteristics of electrolytic capacitors, fragrances such as nitrophenol, nitrobenzoic acid, nitroacetophenone, nitrobenzyl alcohol, 2- (nitrophenoxy) ethanol, nitroanisole, nitrophenetol, nitrotoluene, dinitrobenzene, etc. Group nitro compounds can be added.

In addition, for the purpose of improving the safety of electrolytic capacitors, nonionic surfactants that can improve the withstand voltage of electrolytic solutions, polyoxygens obtained by addition polymerization of polyhydric alcohols and ethylene oxide and / or propylene oxide An alkylene polyhydric alcohol ether compound and polyvinyl alcohol can also be added.

In addition, by adding polysaccharides (mannitol, sorbit, pentaerythritol, etc.), complex compounds of boric acid and polysaccharides, colloidal silica, etc. to the electrolytic solution for aluminum electrolytic capacitors of the present invention, the withstand voltage is further improved. Can be measured.

Examples of phosphoric acid esters or condensates used as flame retardants include trimethyl phosphate, trihexyl phosphate, tri-n-butyl phosphate, triethyl phosphate, methyl polyphosphate, poly-n-butyl phosphate, ethyl polyphosphate, Tolyl phosphate, cresyl diphenyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, methyl trimethylene phosphate, trimethylol ethane phosphate, methyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, 2-ethylhexyl acid phosphate, iso Decyl acid phosphate, monoisodecyl phosphate, 2,6,7-trioxa-1-phosphabicyclo [2,2,2] octane 1-oxide, 3,9-dimethoxy 2,4,8,10-tetraoxa-3,9-diphosphaspiro [5,5] undecane, or compounds represented by the formulas of [Chemical Formula 1] to [Chemical Formula 3], and any one of these Or a combination of several types can be used.

Among the above-mentioned phosphate esters, preferred are trimethyl phosphate, trihexyl phosphate, tri-n-butyl phosphate, triethyl phosphate, methyl polyphosphate, poly-n-butyl phosphate, ethyl polyphosphate, phosphoric acid. It is tritolyl and cresyl diphenyl phosphate, and a good flame retardant effect can be obtained.

The amount of flame retardant added is 3 to 20% by weight, preferably 5 to 10% by weight, with respect to the electrolyte. When the total amount of the flame retardant in the microcapsule exceeds 20% by weight with respect to the electrolytic solution, it adversely affects the characteristics of the electrolytic capacitor, particularly the impedance in the high frequency region. When the amount is less than 3% by weight, even if the microcapsules are dissolved and the flame retardant leaks, the total amount of the flame retardant is insufficient and the flame retardant effect cannot be exhibited.

According to the present invention, by adding a microcapsule encapsulating a flame retardant into an electrolyte containing water, hydrolysis of the phosphate ester which is a flame retardant does not occur even in an electrolyte containing moisture. The flame retardant effect can be obtained over a long period of time. In particular, when the amount of moisture in the element is 35% by weight or less, it is difficult to obtain a flame retardant effect due to moisture, and in the case of containing a small amount of moisture, by containing a microencapsulated flame retardant in the element, flame retardant The effect is noticeable. Here, the water | moisture content in the capacitor | condenser element in this application contains not only the water | moisture content contained in electrolyte solution but the water | moisture content adhering to a separator or electrode foil.

In addition, as a method of containing the microencapsulated flame retardant in the capacitor element, it may be added to the electrolyte solution and dispersed, or may be attached in advance to a separator, an electrode foil or the like. When the microcapsules are dispersed in the electrolytic solution, it is preferable that the size of the microcapsules is 0.02 to 0.05 μm because the microcapsules are easily dispersed in the electrolytic solution. Moreover, when making it adhere to a separator or electrode foil, the magnitude | size of 0.05 micrometer or more may be sufficient. When the microencapsulated flame retardant is attached in advance to a separator, an electrode foil or the like, the microcapsules are dispersed in the capacitor element. Further, if a large amount of the microencapsulated flame retardant is attached to a place where the wound separator or electrode foil is disposed near the safety valve of the electrolytic capacitor, it is easy to suppress the combustion of the capacitor element when the capacitor element is ignited. In this way, the arrangement state of the microencapsulated flame retardant in the capacitor element can be controlled by attaching the microencapsulated flame retardant in advance to a separator, an electrode foil, or the like. Furthermore, since the microencapsulated flame retardant is attached to a separator, electrode foil, or the like, the arrangement state in the capacitor element can be maintained for a long period of time. Further, the effect of the present invention can be obtained even when a microencapsulated flame retardant is attached in advance to a capacitor case and contained in an electrolytic capacitor.

Examples 1 to 4 of the present invention will be described below. Table 1 shows the composition of the electrolytic solution for electrolytic capacitors in Examples 1 to 4 and Comparative Examples of the present invention. In Examples 1 and 2 and Comparative Examples 1-1 and 1-2, the electrolytic solution A was used, and the water content in each element was 3% by weight. In Examples 3 to 4 and Comparative Examples 2-1 to 2-2, the electrolytic solution B was used, and the amount of water in each element was 7% by weight. However, for Examples 1 to 4, a microencapsulated flame retardant encapsulating trimethyl phosphate as a flame retardant with PPS was added to the electrolyte, and phosphoric acid was used in Comparative Examples 1-2 and 2-2. Trimethyl was added as is. In Comparative Example 1-1 and Comparative Example 2-1, no flame retardant was added.

In Examples 1 and 2 and Comparative Examples 1-1 and 1-2, a device having a diameter of 10 mm and a length of 20 mm and a 35 V-680 μF was used. In Examples 3 to 4 and Comparative Examples 2-1 to 2-2, elements having a diameter of 10 mm and a length of 20 mm and 400 V-10 μF were used.

The electrolyte solutions shown in Table 1 were prepared by a conventional method, and ammonia gas was injected into the electrolyte solution B to adjust the pH. And the electrode extraction means was connected to the anode electrode foil which performed the etching process and the chemical conversion process, and the cathode electrode foil which performed only the etching process, and it wound through the separator, and formed the capacitor | condenser element. After this capacitor element is impregnated with an electrolytic solution, it is stored in a bottomed cylindrical outer case, a sealing body made of elastic rubber is attached to the opening of the outer case, the outer case is sealed by drawing, and the electrolytic capacitor is sealed. Produced.

Table 2 shows the amount of flame retardant added to the electrolyte solution, the amount of flame retardant added in the microcapsule to the electrolyte solution, presence or absence of initial self-extinguishing performance, and rating for 500 hours at 105 ° C. Indicates the presence or absence of self-extinguishing performance after voltage is applied. In the present application, the ignition means was brought close to the capacitor element taken out from the case, a flame was applied for 10 seconds, the ignition means was separated from the capacitor element, and the presence or absence of self-extinguishing performance was confirmed. Here, a circle indicates that there is self-extinguishing performance, and a cross indicates that there is no self-extinguishing performance. In the case of having self-extinguishing performance, the combustion reaction is not observed after the ignition means is separated from the burning capacitor element. Further, when there is no self-extinguishing performance, the combustion reaction does not disappear and continues to burn even after the ignition means is separated from the burning capacitor element.

In Comparative Examples 1-1 and 2-1 to which no trimethyl phosphate was added, the capacitor element continued to burn even after the ignition means was released in the initial stage. Further, in Comparative Examples 1-2 and 2-2, although it was confirmed that the initial fire extinguishing means was immediately extinguished and the self-extinguishing performance was confirmed, the rated voltage was applied at 105 ° C. for 500 hours. For the capacitor, the capacitor element continued to burn after the ignition means was released. This is because the flame retardant component is present in the capacitor element in the initial stage, but after application of the rated voltage, trimethyl phosphate reacts with the moisture in the element and hydrolyzes, and exists as a flame retardant component. It seems to be because it has not. On the other hand, Examples 1 to 4 to which the microencapsulated flame retardant was added were extinguished after releasing the ignition means even after application of the rated voltage, and it was confirmed that they had self-extinguishing performance. This is because trimethyl phosphate is present in the microcapsule even after the rated voltage is applied, and by bringing the ignition means closer, the microcapsule dissolves and the trimethyl phosphate dissolves, suppressing the combustion of the capacitor element, and It is thought that fire extinguishing performance was demonstrated.

Next, Examples 5 to 8 of the present invention will be described. Examples 5 and 6 use tolyl phosphate as a flame retardant instead of trimethyl phosphate in Examples 1 to 4, and Examples 7 and 8 use cresyl diphenyl phosphate as a flame retardant. It is a thing. Moreover, as electrolyte solution, the electrolyte solution B shown in Table 2 was used, and the moisture content in each element was 7 weight%. Other conditions were set in the same manner as in Examples 3 to 4, and the presence or absence of the self-extinguishing performance of the capacitor was confirmed.

Table 3 shows the amount of the flame retardant added in the microcapsules with respect to the electrolytes of Examples 5 to 8, presence / absence of initial self-extinguishing performance, and presence / absence of self-extinguishing performance after applying the rated voltage at 105 ° C. for 500 hours. Indicates.

As can be seen from Table 3, even when tolyl phosphate or cresyl diphenyl phosphate is used as the flame retardant, it is difficult to use the electrolytic capacitor over a long period of time as in the case of trimethyl phosphate in Examples 1 to 4. It was confirmed that the fuel effect lasted.

In Examples 5 to 8, the electrolytic solution B containing ethylene glycol as the main solvent was used, but the same effect was obtained even when using the electrolytic solution A containing γ-butyrolactone as the main solvent.

In this embodiment, a wound capacitor is used, but the present invention is not limited to this, and a microencapsulated flame retardant may be added to the multilayer capacitor.

Claims (5)

1. A microencapsulated flame retardant is produced by encapsulating a flame retardant comprising a phosphate ester or a condensate thereof in a resin that dissolves at 150 ° C. or higher, and the microencapsulated flame retardant is contained in a capacitor element. And flame retardant electrolytic capacitor.
2. The resin constituting the shell of the microcapsule is composed of at least one selected from epoxy resin, phenol resin, polyphenylene sulfide (PPS), polyimide (PI), polyaramid, melamine resin, polyurea or polyurethane. Item 2. A flame retardant electrolytic capacitor according to Item 1.
3. 3. The flame-retardant electrolytic capacitor according to claim 1, wherein the amount of water contained in the capacitor element is 35% by weight or less.
4. 4. The flame retardant electrolytic capacitor according to claim 1, wherein the amount of the flame retardant added is 3 to 20% by weight with respect to the electrolytic solution.
5. Phosphate esters or condensates used as flame retardants are trimethyl phosphate, trihexyl phosphate, tri-n-butyl phosphate, triethyl phosphate, methyl polyphosphate, poly-n-butyl phosphate, ethyl polyphosphate, phosphorus The flame-retardant electrolytic capacitor according to any one of claims 1 to 4, which is one or more of tritolyl acid and cresyl diphenyl phosphate.