JPH0195512A - Fire retardant electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve safety against any fire accident by using a solvent including phosphate ester for an electrolytic solution. CONSTITUTION:A phosphate ester is utilized as a solvent or an adjuvant solvent for an electrolytic solution. In particular, there is preferable a capacitor with use of an electrolytic solution including in combination a solvent involving phosphate ester and a solute such as quaternary ammonium salt or quaternary phosphonium salt. The ratio of the phosphate ester to the electrolytic solution is 15wt.% or more or preferably 30wt.% or more for improving the fire retardancy of the capacitor by adding it to a prior electrolytic solution as an adjuvant solvent. Hereby, the safety against a fire can be improved.

Description

[Detailed description of the invention] Industrial applications The present invention relates to flame-retardant electrolytic capacitors.

According to the present invention, a flame-retardant XS capacitor with high safety can be obtained.

1st doubt: oam Electrolytic capacitors use anodized films of aluminum, tantalum, etc. as dielectrics. For example, the element structure of a general aluminum electrolytic capacitor is
As shown in the picture, it is a band-shaped aluminum foil grass with an anodized film formed on it! A strip of aluminum 15 and electrode foil 1 on which no anodized film is formed are wound into a cylindrical shape with a separator grinder 4 interposed therebetween. Then, this capacitor element 1 is impregnated with an electrolytic solution, and as shown in FIG. 2, it is sealed with an outer ant case 6 and a sealing material 7 to form an electrolytic capacitor.

Conventionally, ethylene glycol,
A solution prepared by dissolving an ammonium salt such as boric acid or carboxylic acid in an organic solvent such as N,N-dimethylformamide or r-butyrolactone is used, but these materials are non-shielding and easily flammable.

Problems to be Solved by the Invention In the above-mentioned electrolytic capacitor, when the internal pressure of the element increases due to heat, overvoltage, etc., the wL solution may leak from the sealing part, or the explosion-proof valve may operate, causing the electrolyte to leak. Sometimes I get bubbles. Therefore, sparks from a short circuit in the electrolytic capacitor itself or sparks from other electronic components can ignite the leaked electrolyte, damaging equipment or creating a fire trap. Particularly in recent years, with the high-density packaging of electronic devices, the risk has increased9, and in conjunction with the trend toward unmanned operation of electronic devices, there is a demand for highly safe electrolytic capacitors that will not cause fires.

On the other hand, phosphorus compounds, halides, antimony oxide, etc. are known as flame retardants for glass sticks, but when imparting flame retardancy to electrolyte solutions, the basic performance of the electrolyte solution (usage temperature range, conductivity, spark voltage, compatibility with electrodes, etc.).

For example, solid materials reduce conductivity and halides cannot be used because they corrode the electrodes.

Means for Solving the Problems The present inventors have discovered that phosphorus compounds, especially lower phosphoric acid esters,
By using it as a solvent or a co-solvent for the electrolytic solution, they succeeded in obtaining an S-flammable electrolytic capacitor without significantly reducing the electrical performance, thereby completing the present invention.

That is, the present invention provides an electrolytic capacitor comprising an anode provided with an insulating oxide layer by anodic oxidation, a cathode, a substrate, and an electrolytic solution containing a solute in an organic solvent. A flame-retardant electrolytic capacitor comprising an electrolytic solution using a solvent is provided. Among these, capacitors using an electrolytic solution using a combination of a solvent containing a phosphoric acid ester and a quaternary ammonium salt or a quaternary phosphonium salt as a solute are particularly preferred.

The phosphoric acid esters used in the present invention include trialkyl phosphates (1) represented by the following general formula, monocyclic phosphates in which alkyl groups are bonded to each other (
II) and bicyclic phosphate (@).

(In the formula, Rt-R is a straight-chain or branched alkyl group having carbons S1.1 to 4, and R1-R3 may be different from each other. -(C)- is a straight-chain or branched The alkyl group is 6, k, !, m, n indicate the number of carbon atoms, kw2-8, I
l,, m, nxO is an integer of ~12. ) Specific examples include trimethyl phosphate, dimethylethyl phosphate, methylethylglobil phosphate, methyldiethyl phosphate, triethyl phosphate, trigmivir phosphate, tributyl phosphate,
Examples of the compound represented by the general formula (1) include methylethylene phosphate and medeltrimetherene phosphate, and examples of the compound represented by the general formula (II) include -luethane phosphate. Among these, phosphoric acid esters with small molecular weights are preferable because they dissolve solutes well and have high electrical conductivity. In particular, trimethyl phosphate has the highest electrical conductivity, is nonflammable, and has a low phosphorus content in its molecular structure. It is the most preferable because it has the highest flame retardant effect.

Although the proportion of the phosphoric ester in the electrolytic solution varies depending on the required performance of the electrolytic capacitor, an electrolytic capacitor with the highest flame retardance can be obtained when the entire solvent is phosphoric ester. In order to improve the flame retardance by adding it to a conventional electrolytic solution as a co-solvent, it is necessary to add at least 15 fIk%, preferably 3
It is preferable to use 0% by weight or more.

Examples of the solvent to be mixed with the above phosphoric acid ester include N-methylformamide, N-ethylformamide, N,N-dimethylformamide, N,N-diethylformamide, N-
-methylacetamide, N-ethylacetamide, N,
Amide solvents such as N-dimethylacetamide, N,N-diethylacetamide, N-methylpyrrolidinone, carbamate solvents such as N-methyloxazolidinone, N,N'
- urea solvents such as dimethylimidazolidinone, lactone solvents such as r-buterolactone, β-butyrolactone, r-valerolactone, δ-valerolactone, carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, ethylene glycol, furopylene glycol , alcohol solvents such as chrycerin and methylcellosolve, nitrile solvents such as 3-methoxypropionitrile, and sulfolane solvents such as sulfolane and 3-methylsulfolane. In some cases, less than about 10% water may be added.

Further, as the solute, conventionally known alkali metal salts, ammonium salts, amine salts, quaternary ammonium salts, and quaternary phosphonium salts of inorganic acids and organic acids can be used. Specific examples include boric acid, carbonic acid, silicic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, nitric acid,
Inorganic acids such as sulfuric acid, sulfite, thiocyanic acid, cyanic acid, borohydrofluoric acid, hydraunic acid, arsenic hydrofluoric acid, antimony hydrofluoric acid, perchloric acid, and formic acid, acetic acid, and oxalic acid. , malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, dimethylmalonic acid, diethylmalonic acid , cifropylmalonic acid, 3.3-dimethylglutaric acid, 3-methyladipic acid, 1.6-decanedicarboxylic acid, 1゜2-cyclohexanedicarboxylic acid, maleic acid, citraconic acid, benzoic acid, phthalic acid, trimellitic acid, Examples include anions of organic acids such as pyromellitic acid, salicylic acid, r-resorcinic acid, p-nitrobenzoic acid, phenol, picric acid, methanesulfonic acid, benzenesulfonic acid, and trifluoromethanesulfonic acid.

On the other hand, cationic components include lithium, sodium,
Examples include potassium, an ammonium ion represented by the following general formula (If/), and a quaternary phosphonium ion represented by the following general formula (V).

(In the formula, Rx-Ra is a hydrogen atom or a hydrocarbon group having 1 to 1 carbon atoms. R, -as is a hydrocarbon group having 1 to 10 carbon atoms. R1 to R8 may be different from each other. (They may be the same, or may be combined with each other to form a term.) Specifically, as represented by general formula (IV),
Ammonium, diethylammonium, triethylammonium, )! J propylammonium, ethanol ammonium, shetanol ammonium, triethanol ammonium, cypa hexyl ammonium, piperidinium, 1#5-'; azabicyclo (4,3,0)
nonenium-5,1,8-diazabicyclo(5,4,0
) undecenicum-7, tetramethylammonium, methyltriethylammonium, dimethyldiethylammonium, trimethylethylammonium, tetraethylammonium, tetrabutylammonium, N,N-diethylammonium, N-methyl-N-ethylpyridinium, N,N-dimethylpyridinium Peridinium, benzyltrimethylammonium, N-ethylpyridinium, N, N
Examples of compounds represented by the general formula (V), such as '-dimethylimidazolium, include tetramethylphosphonium, methyltriethylphosphonium, tetraethelphosphonium, tetrapropylphosphonium, and tetraethelphosphonium ions. The amount of solute is below the saturation concentration, preferably 0.1 to 40% by weight.

In the above-mentioned combination of solvent and solute, the aprotic solvent other than water and the phosphoric acid solvent mentioned above and the phosphoric acid ester solvent used in the present invention do not dissolve the alkali metal salt or ammonium salt, so the aprotic solvent and the phosphoric acid When using a mixed solvent of ester solvents, it is preferable to use amine salts, quaternary ammonium salts, and quaternary phosphonium salts.

Among these, those using quaternary ammonium salts or quaternary phosphonium salts as solutes are particularly preferred from the viewpoint of solubility and electrical conductivity.

As shown in FIG. 1, the electrolytic capacitor of the present invention consists of a strip-shaped aluminum anode foil 2 with an anodized film formed thereon and a strip-shaped aluminum cathode foil old strip without an anodized film formed on Manila paper, kraft paper, or polypropylene. The paper is wound into a cylindrical shape with a separator 4 in which these materials are mixed. Then, this capacitor element unit is impregnated with the electrolytic solution containing the phosphoric acid ester, and as shown in FIG.
It is sealed with a sealing material such as PT or IIR to become a flame-retardant electrolytic capacitor. Also, large ones have lug terminals.

Therefore, when evaluating the flame retardance of an electrolytic capacitor as a whole, it is difficult to evaluate the flammability of a capacitor element impregnated with electrolyte by looking at its flammability when it ignites.
This corresponds to the worst case where the element is exposed, so
This is suitable as a method for evaluating the flame retardancy of electrolytic capacitors.

@ The present invention will be explained in more detail below by giving examples and comparative examples.

As a method for evaluating the flame retardance of electrolytic capacitors, the burning rate of a separator impregnated with electrolyte, the 7 ramming time and burnout when the capacitor element, excluding the outer case and sealing rubber, is impregnated with electrolyte and ignited are evaluated. Weight was used. The flash point of the electrolyte was also measured using a Bensky-Martens closed tester.

Example 1 Electrolyte solution (20% by weight of tetraethelammonium hydrogen maleate dissolved in trimethyl phosphate solvent)
Electrical conductivity σ at 5°C = 8.9mS/eN1.5mAz
- Spark voltage Vs = 170V, flash point z, >lso℃
) with a width of 1.5 m, a length of 320 mm, a thickness of 40 μ, and a density of o, et/-. It was fixed horizontally on a sample holding stand with a support needle, and a fire was ignited at one end with a matchstick, but the fire was immediately extinguished within 10 m.

9. Capacitor element impregnated with this electrolyte (aluminum electrode 1.18 f, separator 0.369, electrolyte 0.
82 f: Capacitance C at 25°C and 120Hz when using a 12.5■σ×20th capacitor
80μF1 dielectric loss tangent D = 0.074, leakage current 5-minute value LC; 13μA), back color flame height 25wa (D 11
wm EB's Bunsen burner ignited it for 5 seconds, and when I took it out, it immediately extinguished. The weight loss at this time is 0.0
At 4f, for the weight of the electrolyte and separator before ignition,
It was a disaster with 3% burnout.

Comparative Example 1 Electrolyte solution (e =
13.7 ms/m, Va depth 83 Vs Zp=100
℃) under the same conditions as in Example 1, soaked manila paper and directly fired it with a matchstick, and determined the burning speed from the burning time of 300 cm, and found that V = 13.0 m/sec.

In addition, this electrolyte was impregnated into the same capacitor element as in Example 1 (C = 981 μF, D = 0.064, LC = 13
μA), the 7 ramming time t when ignited by the burner is 9
After 5 seconds, the burnout rate W of the electrolyte and separator was 98%.

Examples 2 to 6 The same solute as in Example 1 was used, and the solvents were triethyl phosphate (Example 2), a mixed solvent of T-butyrolactone and trimethyl phosphate (Example 3), and a mixed solvent of r-butyrolactone and triethyl phosphate (Example 3). Example 4), a mixed solvent of γ-butyrolactone and tripropyl phosphate (Example 5), or a mixed solvent of r-butyrolactone and tributyl phosphate (Example 6)
) The results when K was changed are shown in Table 1, and all showed high flame retardancy.

Comparative Examples 2 to 4 The same solute as in Example 1 was used, and the solvent was propylene carbonate (Comparative Example 2), N,N-dimethylformamide (Comparative Example 3), or ethylene glycol (Comparative Example 4).
) are shown in Table 1, and all of them were extremely flammable.

Examples 7 to 12 In a solvent containing trimethyl phosphate, dimethylammonium hydrogentetatalate (Example 7), monotetraethylamphentium borate (Example 8), N-methyl-N-ethylpyrroliborofluoride When using 1 solution in which dizinium (Example 9), tetramethylammonium hydrogen azelaate (Example 1O), triethylammonium hydrogen hydrogen maleate (Example 11), or ammonium adipate (Example 12) was used. The results are shown in Table 1, and the h deviation also showed high flame retardancy regardless of the type of solute.

Comparative Example S Table 1 shows the results when using a tS solution in which 20i 11% tetramethylammonium hydrogen 7-talate was dissolved in a γ-butyrolactone solvent, and it was extremely flammable.

Reference Examples 1 to 9 Table 2 shows the results using only Manila paper and only solvent.

In addition, in Tables 1 and 2, the following abbreviations were used.

GBL: r-butyrolactone PC: Propylene carbonate DMF: N,N-dimethylformamide EG: Ethylene glycol TMP nitrimethyl phosphate TEP:) Liethyl phosphate TBP: ) Butyl phosphate (blank below)

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing the structure of elements of a general aluminum electrolytic capacitor and how they are housed in an exterior case. L capacitor element, 2 anode foil, 1 cathode foil. Front separator, 5- lead terminal, 6- outer case, 7. Sealing material, a Electrolytic capacitor patent applicant Mitsubishi Yuka Co., Ltd. Agent Patent attorney Masahisa Hase Patent attorney Takaya Yamamoto

Claims (1)

[Claims] 1. An electrolytic capacitor consisting of an anode provided with an insulating oxide layer by anodization, a cathode, a spacer, and an electrolytic solution containing a solute in an organic solvent, including an electrolytic solution using a solvent containing a phosphate ester. A flame-retardant electrolytic capacitor made of