JPH077741B2 - Electrolytic capacitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor obtained by impregnating an electrolytic paper interposed between an anode foil and a cathode foil with a predetermined electrolytic solution, and particularly to a short circuit defective rate thereof. The characteristics of the electrolytic capacitor such as the equivalent series resistance (ESR) are improved without affecting the.

Conventional Technology and Its Deficiencies Generally, electrolytic capacitors, particularly aluminum electrolytic capacitors, are formed by winding electrolytic paper between an anode aluminum foil and a cathode aluminum foil, and then immersing the electrolytic paper in a predetermined electrolytic solution. It is manufactured by impregnating it with electrolyte and sealing it. The electrolyte is usually made by using ethylene glycol, dimethylformamide, etc. as a solvent, and by dissolving organic acid salts such as boric acid or ammonium adipate, ammonium hydrogen maleate, etc. in these solvents and making it penetrate from both ends of the capacitor element. is doing.

Since the conventional aluminum electrolytic capacitors as described above have electrolytic paper impregnated with an electrolytic solution, the impedance characteristics as a capacitor, especially the equivalent series resistance (abbreviated as ESR below)
, Which usually lowers the resistance of the electrolytic solution, thins the electrolytic paper, or lowers the density, but also changes the material of the electrolytic paper from ordinary wood kraft pulp to special materials such as Manila hemp pulp and esparto pulp. And so on. However, lowering the resistance value of the electrolytic solution causes corrosiveness to the aluminum foil, and thinning the electrolytic paper or lowering the density increases the short-circuit failure rate when winding it around the capacitor element. Even if no short circuit occurs, the short defect rate after being commercialized and put on the market is high.

Therefore, in order to reduce the short-circuit defect rate, the thickness of electrolytic paper should be increased, the density should be increased, and in the case of the same density, JIS P 8121 shall indicate the degree of beating of the raw material pulp.
It is known that if the value of CSF (Canadian Standard Freeness) is reduced, the pulp fibers become finer due to fibrillation, and the resulting electrolytic paper becomes dense, which is good for improving the short-circuit failure rate. Also for these items
The effect on ESR is that when the electrolytic paper is thickened, the ESR deteriorates linearly, and when the density is increased, the ESR deteriorates quadratically.However, it was found that the CSF value has almost no effect. ing. That is, in order to improve the ESR, it is necessary to make the electrolytic paper thin and reduce its density, contrary to the improvement of the short circuit defect rate.

Therefore, in order to achieve the objectives of both the improvement of short-circuit defect rate and the improvement of ESR at the same time, it is necessary to reduce the value of CSF in order to improve the short-circuit defect rate, considering that the CSF value does not affect ESR. Must be assumed. Therefore, it is ideal to make electrolytic paper with a low density and low density CSF. However, when an electrolytic paper is produced from pulp composed of natural cellulose such as ordinary kraft pulp, Manila hemp pulp, and esparto pulp,
If the value of CSF is made small, hydrogen bonds that act between fibers increase due to fibrillation, and therefore the density of electrolytic paper always increases. Therefore, when electrolytic paper of the same thickness is made with the same paper machine, the CSF value of high-density paper is smaller than that of low-density paper. As a result, if a low density electrolytic paper is used to improve the ESR of the electrolytic capacitor, the CSF value will increase,
While the short-circuit defect rate increases, when the value of CSF is small, the density becomes higher and the ESR becomes worse.As a result, it is difficult to improve both the short-circuit defect ratio and ESR at the same time. there were. For example, an electrolytic capacitor that is suitable for high frequency switching power supplies that require low ESR has a thickness of 40 μm and a density of 0.3 to 0.4 g / cm.
³ Manila hemp pulp electrolytic paper is used, and in this case, the short-circuit failure rate is inevitably increased to several tens of percent.
On the other hand, electrolytic paper used in large-scale electrolytic capacitors for large-capacity and high-voltage is required to have withstand voltage and electrolyte retention.
High density paper with a density of 0.7 g / cm ³ or more or double paper consisting of high density paper and low density paper is used.In this case, reliability against short circuit failure is high, but ESR increases and heat loss due to heat generation also occurs. I can't help getting bigger.

On the other hand, when the electrolytic solution using the ethylene glycol as a solvent is used, the electrical characteristics at low temperature of the obtained electrolytic capacitor are not good because the viscosity of the electrolytic solution is large, while the electrolytic solution using dimethylformamide as a solvent is used. Although low-temperature characteristics are improved, dimethylformamide has a problem in high-temperature characteristics because it is easily decomposed by heat, and is also highly toxic, resulting in poor workability. Therefore, in order to make up for the drawbacks of the electrolytic solution, an electrolytic solution using γ-butyrolactone instead of the solvent has been developed and used in recent years. Since the electrolytic solution using γ-butyrolactone has a low viscosity, a high vapor pressure, and a low toxicity, it has an advantage of improving low-temperature characteristics and workability.

Problems to be Solved by the Invention The biggest problem with such a conventional electrolytic capacitor is that the ESR of the obtained electrolytic capacitor becomes larger than the limit value if short circuit failure is to be prevented and reliability is to be obtained. However, if an attempt is made to lower the ESR, short-circuit defects will inevitably increase, and the reliability of the electrolytic capacitor cannot be obtained. That is, as long as the conventional electrolytic paper is used, the ESR cannot be reduced without substantially increasing the short-circuit defect rate.

Therefore, the density and the thickness that prevent short-circuit failure during the element winding process are maintained in the electrolytic paper, and the element is wound without causing the short-circuit failure and impregnated with the electrolytic solution, and then compared with the conventional swelling. If the degree of swelling of the electrolytic paper by the electrolytic solution can be significantly increased, the fibers that make up the electrolytic paper will expand and the gaps between the fibers will increase, so the density of the electrolytic paper can be substantially reduced and the ESR Can be reduced. Moreover, since it is after the element winding step, short-circuit defects are not increased.

However, conventionally, electrolytic paper was swollen to some extent by impregnating an electrolytic solution using ethylene glycol, dimethylformamide, etc. as a solvent, but it was not associated with improvement of ESR, and ESR was also improved. There was no significant reduction effect.

In particular, since the electrolytic solution using γ-butyrolactone as a solvent has low viscosity and weak toxicity, the low temperature characteristics and workability of the electrolytic capacitor are good, but the ESR is extremely poor. This is because γ-butyrolactone is less hydrophilic than other conventional electrolytic solutions, so that the cellulose fibers after being impregnated with the electrolytic solution hardly swell, and the substantial density of the electrolytic paper is hardly reduced. by. In particular, in the case of an electrolytic capacitor with a working voltage of 50 V or higher, it is desirable to use electrolytic paper with a density of 0.6 g / cm ³ or higher in order to reduce the short circuit defect rate and improve the withstand voltage performance. In high-electrolytic paper, the fibers are strongly bonded to each other by hydrogen bonds.Therefore, when an electrolytic solution using γ-butyrolactone as a solvent is used, the ESR increases significantly because the electrolytic paper does not swell in addition to its high density. Will be lost.
In addition, since the amount of electrolyte retained is small, dry-up of the electrolytic capacitor is likely to occur and the life is short, and variations in electrical characteristics such as capacitance, impedance characteristics, and leakage current become large. Therefore, γ-butyrolactone is used in combination with conventional ethylene glycol, an electrolytic solution in which other solvent such as dimethylformamide or water is mixed, or a method of using electrolytic paper having a density as low as possible is used in combination. It is not fully effective in reducing ESR.

Therefore, the present invention eliminates the problems that such conventional electrolytic capacitors have, and in order to improve the ESR without affecting the short-circuit defect rate, the degree of swelling of electrolytic paper with respect to various electrolytic solutions is remarkable. The purpose of the present invention is to provide an electrolytic capacitor using an electrolytic paper which is improved.

Means for Solving the Problems In order to achieve the above object, the present invention provides an electrolytic capacitor obtained by impregnating an electrolytic paper interposed between an anode foil and a cathode foil with a predetermined electrolytic solution. Is the solvent γ
-Butyrolactone is included, and the electrolytic paper contains fibers in which organic substituents are introduced into the cellulose fibers by a chemical reaction, whereby the swelling degree of 5% or more and 15% with respect to γ-butyrolactone as a solvent of the electrolytic solution. the following electrolytic capacitor and the electrolytic solution, wherein the solubility is the density 0.4g / cm ³ ~1.0g / cm ³ a includes dimethylformamide, and the electrolytic paper chemistry cellulose fibers By containing fibers introduced with an organic substituent by having a swelling degree of 60% or more and a solubility of 15% or less with respect to dimethylformamide as a solvent of the electrolytic solution, a density of 0.4 g / cm ^{3 to} 1.0 g / electrolytic capacitor and the electrolytic solution, characterized in that cm is ³ comprises ethylene glycol as a solvent, and conductive organic substituents wherein the electrolytic paper by a chemical reaction in the cellulose fibers Is a density 0.4g / cm ³ ~1.0g / cm ³ has a degree of swelling of 40% or more of the ethylene glycol and 15% or less of the solubility of the solvent of the electrolyte by containing the incoming fibers The present invention provides an electrolytic capacitor characterized by the above.

According to the electrolytic capacitor of the present invention having the above structure, the degree of swelling of the electrolytic paper is significantly increased during the impregnation of the electrolytic solution after the element winding step, the fibers constituting the electrolytic paper expand, and the gap between the fibers is increased. Is large, the density of the electrolytic paper can be substantially reduced, and the ESR can be reduced. Moreover, since it is after the element winding step, short-circuit defects are not increased. Therefore, even if the thickness and density of the electrolytic paper itself are set large enough to withstand high voltage and the short-circuit defect rate is reduced, the ES of the obtained electrolytic capacitor is reduced.
An electrolytic capacitor in which R is reduced to a desired value or less can be obtained.

Examples The configuration of the electrolytic capacitor according to the present invention and various examples will be described below.

As a result of repeated studies on swelling of electrolytic paper, the present inventor found that the electrolytic paper significantly swells in the electrolytic solution by introducing an organic substituent into the cellulose fiber constituting the electrolytic paper, and based on this finding. Based on this, various embodiments of the present invention described below have been embodied.

The electrolytic paper used in the present invention is mainly composed of cellulose, specifically, wood pulp fibers obtained from conifers, hardwoods, non-wood pulp fibers obtained from Manila hemp, red hemp, sisal and esparto grass, viscose rayon. , Regenerated cellulose fibers such as cupra rayon. These cellulose fibers have many hydroxyl groups (O
H) is contained and the fibrils constituting the fiber are strongly bonded by the hydrogen bond formed between the hydroxyl groups. Even if such a cellulose fiber is immersed in a solvent having a low hydrophilicity such as γ-butyrolactone, the solvent cannot penetrate into the hydrogen bond portion formed between the fibrils,
Therefore, the fibers hardly swell. In addition, even paper composed of cellulosic fibers does not mean that the paper is formed simply by the entanglement of the fibers, but hydrogen bonds are formed at the contact parts where the fibers are entangled, and the fibers also bond by this force. ing.

Therefore, the present invention introduces an organic substituent into the cellulose fiber, which is easily compatible with the various electrolytic solutions, and facilitates the infiltration of the electrolytic solution into the hydrogen-bonded portion formed between the fibrils or between the fibers, thereby electrolyzing the fiber itself. The solution is swollen and the binding force between the fibers in the electrolytic solution is weakened to increase the swelling of the electrolytic paper in the electrolytic solution.

As the chemical reaction for introducing the organic substituent, all the reactions caused by cellulose such as graft polymerization reaction to cellulose and substitution reaction of hydroxyl group of cellulose can be used, but especially esterification reaction of hydroxyl group contained in cellulose It is suitable to use an etherification reaction or an acetalization reaction because the reaction can be easily carried out. In addition, in the chemical reaction for introducing the organic substituent, it is necessary that the cellulose fiber retains the same fiber morphology as that before the reaction even after the reaction, and does not excessively dissolve in the electrolytic solution. Therefore, the chemical reaction for introducing these organic substituents is carried out under conditions that are reduced as compared with the reaction for producing a general cellulose derivative, and in the hydroxyl group substitution reaction, one of the hydroxyl groups contained in cellulose is Reaction conditions are preferred in which only parts are replaced. For example, when most of the hydroxyl groups, such as 50% or more, are substituted, the resulting fibers may be brittle or may not retain their fiber form, and electrolytic paper may not be formed. Furthermore, when an electrolytic capacitor is manufactured using such fibers, most of the fibers are dissolved when the electrolytic paper is immersed in the electrolytic solution, causing a short circuit failure of the obtained electrolytic capacitor and the viscosity of the electrolytic solution. It also means that the ESR increases with the increase. Therefore, the present invention is to increase the swelling degree of the electrolytic paper with respect to the electrolytic solution, to substantially reduce the density of the electrolytic paper after impregnating the electrolytic solution to improve and reduce the ESR, and the swelling degree of the electrolytic paper. The conditions are selected so that the degree of swelling for obtaining a predetermined ESR value can be obtained so that the viscosity of the electrolytic solution is not increased more than necessary and adversely affects the ESR.

Substituents to be introduced into cellulose fibers are chlorine CL, bromine
Substituents that do not contain elements that cause corrosion of electrolytic capacitors such as Br and iodine I may be used, but if a substituent with a large proportion of carbon such as an alkyl group or an allyl group having 8 or more carbon atoms is introduced, the cellulose fiber becomes extremely hydrophobic. As a result, the strength of the electrolytic paper decreases, which may cause a trouble during the element winding process. In addition, the proportion of carbon is low, and the carboxyl group (-CO
(OH), a sulfonic acid group (—SO ₃ H) or the like is not preferable because a substituent having a dissociative polar group is introduced, the swelling property decreases. Therefore, it is necessary to select an organic substituent to be introduced according to the degree of polarity or hydrophilicity of the electrolytic solution. Preferably a hydroxyl group to an alkyl group, an ether group,
An organic substituent having one or more kinds such as an amino group, a nitrile group, an amide group, an imide group or a carbonyl group bonded thereto, and a substituent having an appropriate polarity is desirable. Further, it is preferable that the substituent consisting of only an alkyl group has 5 or less carbon atoms. The particularly preferable chemical reaction examples are shown below.

(A) Esterification reaction (1) Reaction with acid chloride (2) Reaction with acid anhydride (3) Reaction with isocyanate (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(B) Etherification reaction (4) Reaction with alkyl halide CELL-OH + RCL → CELL-OR (5) Reaction with dialkyl sulfuric acid (Note) R indicates any of CH ₃ , C ₂ H ₅ , and C ₃ H ₇ .

CELL indicates a cellulose chain.

(6) Reaction with alkylene oxide (Note) R indicates any of H, CH ₃ , and C ₂ H ₅ . n represents an integer of 1 or more. CELL indicates a cellulose chain.

(7) Reaction with vinyl compounds (Note) R indicates any of CN, CONH ₂ , OC ₂ H ₅ , COCH ₃ , and COC ₂ H ₅ .

CELL indicates a cellulose chain.

(C) Acetalization reaction (8) Acetal reaction (Note) R represents any one of CH ₃ , C ₂ H ₅ , C ₃ H ₇ , and C ₄ H ₉ .

CELL indicates a cellulose chain.

As described above, it is preferable that a part of the hydroxyl group (OH) in the cellulose is substituted with the above-mentioned substituent by utilizing the esterification reaction (A), the etherification reaction (B) and the acetalization reaction (C).
Further, the electrolytic paper used in the present invention does not have to be a paper composed only of cellulose fibers having an organic substituent introduced therein, and ordinary cellulose fibers or other chemical fibers such as polypropylene and polyester and cellulose fibers having an organic substituent introduced therein are used. It may be a paper prepared by mixing and. That is, it suffices that the electrolytic paper substantially contains the cellulose fiber having the organic substituent introduced therein.

Then, in the production of the electrolytic paper according to the present invention, a low temperature plasma reaction method or a radiation graft polymerization method is used to introduce an organic substituent into the constituent cellulose fibers in the paper state after paper making. Is also good. However, in order to remove reaction by-products when introducing organic substituents into cellulose fibers and to remove substances such as reaction aids that cause corrosion of electrolytic capacitors, it is necessary to thoroughly wash the cellulose fibers after the reaction is completed. Is. Therefore, it is desirable to prepare an electrolytic paper by a method such as papermaking after introducing an organic substituent in a fiber state. The papermaking method is not particularly limited, and a handmade or mechanical papermaking method such as a cylinder paper machine, a Fourdrinier paper machine and a former can be used.

As described above, the electrolytic paper according to the present invention swells remarkably in the electrolytic solution, and the fiber gap is widened, whereby the density is substantially lowered and the ESR of the obtained electrolytic capacitor can be reduced. Therefore, in the case of the present invention, the higher the density of electrolytic paper, the greater the effect of reducing ESR, and the lower the density (for example, 0.3 g /
Paper with a density of less than ³ cm3 has a small effect of reducing ESR. Therefore, it is preferable to use electrolytic paper having a density of about 0.4 to 1.0 g / cm ³ . When the degree of swelling further increases extremely, a part of the fibers is dissolved in the electrolytic solution at the time of impregnation, and the viscosity of the electrolytic solution increases, so that the viscosity of the electrolytic solution does not adversely affect the ESR, Moreover, if the density of the electrolytic paper after impregnation with the electrolytic solution can be effectively lowered and the ESR can be effectively reduced, part of the fiber is dissolved in the electrolytic solution during impregnation, Since the viscosity is increased, the viscosity of the electrolytic solution does not adversely affect the ESR, and the ESR can be effectively reduced by substantially lowering the density of the electrolytic paper after impregnating the electrolytic solution. As a preferable range, the electrolytic paper has a swelling degree of 5% or more and a solubility of 15% or less with respect to γ-butyrolactone as a solvent of the electrolytic solution. Further, it has a swelling degree of 60% or more and a solubility of 15% or less with respect to dimethylformamide as a solvent of the electrolytic solution. Furthermore, for ethylene glycol as the solvent of the electrolyte
It has a swelling degree of 40% or more and a solubility of 15% or less.

Below, various examples for obtaining the electrolytic capacitor according to the present invention and the results of measuring the swelling degree, the solubility, etc. of the used electrolytic paper, the ESR of the obtained electrolytic capacitor, the short circuit failure rate, etc. are shown. Each measured value of each sample was measured by the following measuring method and apparatus.

(1) Method for producing electrolytic capacitor Electrolytic paper is interposed between the tabbed anode foil and cathode foil so that both electrodes do not come in contact with each other and wound to form an electrolytic capacitor element, which is then impregnated with a predetermined electrolytic solution. By encapsulating it in a case and aging it with a normal method of 50 WV, 22
A 0 μF aluminum dry electrolytic capacitor was manufactured.

(2) Evaluation method of electrolytic paper Thickness, density and tensile strength Thickness, density and tensile strength were measured by the method specified in JIS C 2301 (electrolytic capacitor paper).

Swelling degree The swelling degree was obtained by stacking 10 sheets of electrolytic paper into a test piece, measuring its thickness with a micrometer (A μm), and then measuring the test piece with γ.
Immerse in butyrolactone or in the given solvent or electrolyte for exactly 15 minutes. After that, the test piece was taken out, and the thickness thereof was measured with a micrometer in a wet state (B μm). A micrometer specified by JIS C2301 (electrolytic capacitor paper) was used, and the swelling degree was calculated by the following formula.

Solubility About 2 g of electrolytic paper is used as a test piece, it is dried to a constant weight at 105 ° C and its weight is accurately measured (Cg), and then the test piece is γ-butyrolactone, or a specified solvent or a specified solvent. Immerse in electrolyte for 24 hours at 25 ℃. Then the test piece
It is filtered with a 200-mesh wire mesh and taken out, and washed on the wire mesh with ion-exchanged water. This test piece is again at 105 ℃
The sample was dried to a constant weight with, the weight was accurately measured (Dg), and the solubility was calculated by the following formula.

(3) Evaluation Method of Electrolytic Capacitors Short Circuit Failure Rate After winding electrolytic paper with anode foil and cathode foil to form an electrolytic capacitor element, conduction by short circuit between both electrodes was confirmed with a tester without impregnating electrolytic solution. .
Short defect rate was inspected for 500 to 10,000 elements,
The ratio of the short elements to the total number of elements was calculated.

ESR (Equivalent Series Resistance) The ESR of an electrolytic capacitor is L at a frequency of 1000HZ at a temperature of -40 ° C.
It was measured by a CR meter.

Capacitance The capacitance of an electrolytic capacitor is LCR at a frequency of 120Hz at a temperature of 20 ° C.
It was measured by a meter.

Leakage current Leakage current of electrolytic capacitor is 5V when 5V DC is loaded.
After a minute, the current value was measured.

Amount of Electrolyte Solution The weight difference of the electrolytic capacitor before and after impregnation with the electrolyte solution was measured to determine the amount of electrolyte solution impregnated into the element.

(Example 1) 100 g of Manila hemp pulp was immersed in 500 ml of a 2% NaOH aqueous solution and then centrifuged to remove excess NaOH aqueous solution to obtain a pulp concentration of 35%. 70 g of acrylonitrile was added to the alkali-treated pulp, and the mixture was slowly stirred at 20 ° C. for 2 hours to cyanoethyl the hemp pulp. This cyanoethylated Manila hemp pulp was thoroughly washed with ion-exchanged water, beaten to 670 ml of CSF with a PFI mill, and hand-drawn with ion-exchanged water to give a thickness of 40.3 μm and a density.
A 0.406 g / cm ³ handmade sheet was prepared. Next, an aluminum electrolytic capacitor was manufactured using this handmade sheet as electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to increase the specific resistance.
It is adjusted to 200 Ω · cm (20 ° C).

(Example 2) The cyanoethylated Manila hemp pulp obtained in the same manner as in Example 1 was beaten to CSF 600 ml with a PFI mill, and hand-drawn with ion-exchanged water to give a thickness of 40.8 μm and a density of 0.508 g / c.
A handmade sheet of m ³ was created. Next, an aluminum electrolytic capacitor was manufactured using this handmade sheet as electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in a mixed solvent of 70% γ-butyrolactone and 30% dimethylformamide to obtain a specific resistance of 200 Ω · cm (20
C)).

(Example 3) The cyanoethylated Manila hemp pulp obtained in the same manner as in Example 1 was beaten to 540 ml of CSF with a PFI mill, and hand-drawn with ion-exchanged water to obtain a thickness of 40.0 μm and a density of 0.595 g / c.
A handmade sheet of m ³ was created. Next, an aluminum electrolytic capacitor was manufactured using this handmade sheet as electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone to give a specific resistance of 200 Ω ・ c.
It is adjusted to m (20 ℃).

(Example 4) 100 kg of softwood wood pulp was immersed in 0.5 m ^{3 of a} 2% NaOH aqueous solution, and then pressed with a screw press to remove excess NaOH aqueous solution to a pulp concentration of 40%. The alkali-treated pulp was placed in a stainless steel pressure resistant container, and the air in the container was replaced with nitrogen gas. Then 1,2-butylene oxide 50k
g was placed in a container, sealed, and reacted at 80 ° C. for 60 minutes to hydroxybutylate the softwood wood pulp.

After thoroughly washing this hydroxybutylated softwood wood pulp with ion-exchanged water, it was beaten with a double disc refiner to a CSF of 5 ml or less, and further paper-made with a Fourdrinier paper machine using ion-exchanged water as a water source, with a thickness of 25.4 μm, Density 0.85
4 g / cm ³ of paper was obtained.

Then, this paper was used as an electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water to adjust the specific resistance to 200 Ω · cm (20 ° C).

(Example 5) Hydroxybutylated softwood wood pulp obtained in the same manner as in Example 4 was used as a raw material, and was paper-made by a Fourdrinier / Round-net combination paper machine to combine high-density paper and low-density paper. Created a double paper by. Those beaten up CSF5ml following double disc refiner hydroxy butylated softwood wood pulp during paper making and paper stock of fourdrinier, thickness 20.3Myuemu, while paper density paper density 0.801 g / cm ³ in fourdrinier portion , Unbeaten hydroxybutylated softwood wood pulp is made into paper in the cylinder part and combined to give a thickness of 60.8μ.
m, and a density of 0.645 g / cm ³ was prepared.

Then, this double paper was used as an electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water to adjust the specific resistance to 200 Ω · cm (30 ° C).

Example 6 100 kg of Manila hemp pulp was dipped in 0.5 m ^{3 of a} 3% NaOH aqueous solution, and then squeezed with a screw press to remove excess NaOH aqueous solution to a pulp concentration of 39%. The alkali-treated pulp was placed in a stainless steel pressure resistant container, and the air in the container was replaced with nitrogen gas. Next, 50 kg of propylene oxide was put in a container and sealed, and the mixture was reacted at 50 ° C. for 70 minutes to hydroxypropyl the Manila hemp pulp. After thoroughly washing this hydroxypropylated Manila hemp pulp with ion-exchanged water, beaten it to a CSF of 485 ml with a beater, paper-making with a cylinder paper machine using ion-exchanged water as water, and a thickness of 40.1
A paper having a thickness of 0.6 m and a density of 0.603 g / cm ³ was obtained. Then, this paper was used as an electrolytic paper to manufacture an aluminum electrolytic capacitor.
The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol to adjust the specific resistance to 200 Ω · cm (20 ° C).

(Example 7) 500 ml of acetic anhydride was added to 100 g of Manila hemp pulp and reacted at 120 ° C for 1 hour while stirring to acetylate the Manila hemp pulp. This acetylated Manila hemp pulp was thoroughly washed with ion-exchanged water, beaten to 530 ml of CSF with a PFI mill, and hand-drawn with ion-exchanged water to give a thickness of 40.5.
A handmade sheet having a thickness of μm and a density of 0.606 g / cm ³ was prepared.

Next, an aluminum electrolytic capacitor was manufactured using this handmade sheet as electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the specific resistance to 200 Ω · cm (20 ° C). In addition to the above Examples 1 to 7, in order to compare the electrolytic paper according to the present invention with a conventional electrolytic paper, a conventional electrolytic paper using a cellulose fiber in which an organic substituent is not introduced is described below. It was created by the conventional example described in.

(Conventional Example 1) Manila hemp pulp was beaten with a PFI mill to obtain 675 ml of CSF.
The beaten pulp was handmade using ion-exchanged water to prepare a handmade sheet having a thickness of 41.0 μm and a density of 0.402 g / cm ³ .

Next, an aluminum electrolytic capacitor was manufactured using this handmade sheet as electrolytic paper. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusting the specific resistance to 200Ω · cm (20 ° C).
It is an electrolytic capacitor of a conventional example corresponding to the first embodiment.

(Conventional Example 2) Manila hemp pulp was beaten with a PFI mill to obtain 600 ml of CSF. The beaten pulp was handmade using ion-exchanged water to prepare a handmade sheet having a thickness of 39.8 μm and a density of 0.511 g / cm ³ . Next, this handmade sheet was used as electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolyte was 70% γ-butyrolactone and dimethylformamide.
Ammonium borodisalicylate was dissolved in a mixed solvent with 30% to adjust the specific resistance to 200 Ω · cm (20 ° C.), which is the conventional electrolytic capacitor corresponding to Example 2.

(Conventional Example 3) Manila hemp pulp was beaten with a PFI mill to obtain CSF (530 ml). The beaten pulp was handmade using ion-exchanged water to prepare a handmade sheet having a thickness of 39.7 μm and a density of 0.603 g / cm ³ . Next, this handmade sheet was used as electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in γ-butyrolactone and adjusted the specific resistance to 200 Ω · cm (20 ° C.), which is a conventional electrolytic capacitor corresponding to Example 3.

(Conventional Example 4) CSF5 of coniferous wood pulp with a double disc refiner
After beating up to less than ml and making paper with a Fourdrinier paper machine using ion-exchanged water, a paper with a thickness of 25.1 μm and a density of 0.856 g / cm ³ was obtained. I made an electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water to adjust the specific resistance to 200 Ω · cm (20 ° C.). An example electrolytic capacitor.

(Conventional Example 5) Softwood wood pulp was used as a raw material and papermaking was carried out by a fourdrinier / cylinder combination paper machine to prepare a double paper by combining high-density paper and low-density paper. When making paper, softwood wood pulp was CS with a double disc refiner.
Thawed up to F5 ml or less is used as a long-net papermaking raw material.
While making high density paper of 20.5 μm and density of 0.797 g / cm ³ in the Fourdrinier area, unbeaten coniferous wood pulp is made in the cylinder area and combined to make a thickness of 60.5 μm and a density of 0.644 g / cm 3. ^{I made 3} double sheets of paper.

Then, this double paper was used as an electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water to adjust the specific resistance to 200 Ω · cm (20 ° C.), which corresponds to Example 5. It is a conventional electrolytic capacitor.

(Conventional Example 6) Manila hemp pulp was beaten with a beater to obtain 480 ml of CSF. This beaten pulp was made with a cylinder paper machine using ion-exchanged water as a water source, and had a thickness of 39.7 μm and a density of 0.607 g / cm ³
Got the paper.

Then, this paper was used as an electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium hydrogen melenate in a mixed solvent of dimethylformamide 50% and ethylene glycol 50% to give a specific resistance of 200Ω.
It is an electrolytic capacitor of the conventional example corresponding to Example 6, which is adjusted to cm (20 ° C.).

(Conventional Example 7) Manila hemp pulp was beaten with a PFI mill to obtain 580 ml of CSF. The beaten pulp was handmade using ion-exchanged water to prepare a handmade sheet having a thickness of 39.5 μm and a density of 0.605 g / cm ³ . Next, this handmade sheet was used as electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide to adjust the specific resistance to 200 Ω · cm (20 ° C.), which is the conventional electrolytic capacitor corresponding to Example 7.

The electrolytic papers used in Examples 1 to 7 and Conventional Examples 1 to 7 obtained as described above were dipped in the solvent used for the electrolytic solution and the electrolytic solution used, and the swelling degree was measured. The results are shown in Table 1 together with the measurement results of thickness, density and tensile strength. In addition, Table 2 shows the measurement results of the capacitance, leakage current, ESR capacitor characteristics, short-circuit failure rate, and electrolytic solution amount of the electrolytic capacitors according to Examples 1 to 7 and Conventional Examples 1 to 7.

As shown in the measurement results of Table 1 and Table 2, the electrolytic paper made of the cellulose fiber having the organic substituent introduced therein according to the present invention is different from conventional electrolytic papers in various electrolytic solutions and electrolytic solutions such as γ-butyrolactone. The degree of swelling is remarkably increased with respect to various solvents, and as a result, the density of the electrolytic paper after impregnation with the electrolytic solution is substantially reduced, and the ESR is remarkably improved and reduced. For example, Example 1 has a thickness 40.3Myuemu, a density of 0.406 g / cm ^3, the conventional example 1 thickness 41.0Myuemu, density 0.402 g / cm ³ and approximately the same thickness, but the electrolytic paper of the same density , Γ-butyrolactone as solvent
The degree of swelling in an electrolyte solution using 100% is 0.2 in Conventional Example 1.
%, And the degree of swelling in Example 1 was 69.7%, which means that the degree of swelling of the electrolytic paper was clearly increased. Furthermore, the degree of swelling increased from 54.7% to 90.7% for dimethylformamide, and the degree of swelling increased from 35.6% to 42.5% for ethylene glycol. As a result, ESR is 0.72 in Conventional Example 1.
In contrast to Ω, the value of Example 1 is 0.57Ω, which is a large decrease. Moreover, the short-circuit defect rate is not affected from 9.0% to 8.8%, and it is improving but decreasing slightly. The amount of electrolyte has also increased from 0.693g to 0.792g,
Combined with the introduction of the organic substituent to improve the compatibility between the electrolytic paper and the electrolytic solution, it is possible to prevent the electrolytic solution from drying up and prolong the life of the electrolytic capacitor.

Further, in Example 4 and Conventional Example 4 having substantially the same thickness and the same density, the swelling degree with respect to the electrolytic solution obtained by adding 10% water to 90% ethylene glycol as a solvent is 38.6% in Conventional Example 4, whereas the swelling degree in Example 4 is 38.6%. No. 4 was swollen as large as 100.1%, and as a result, the ESR was 12.38Ω in Conventional Example 4, while Example 4 was
Is greatly improved and decreased to 5.36Ω, and the short-circuit defect rate is 1.4%, which is not affected.

Further, in Example 6 having substantially the same thickness and the same density, and in Conventional Example 6, the degree of swelling in the electrolytic solution using dimethylformamide 100% as a solvent was 50.8% in Conventional Example 6 and 61.9% in Example 6. Although the degree of swelling is less than in the other examples, the ESR is clearly reduced from 1.86Ω to 1.08Ω.

The degree of swelling was 0.2% with respect to γ-butyrolactone as the solvent of the electrolytic solution as shown in Conventional Examples 6 and 7, and the degree of swelling that was hardly swelled in the past was as shown in Examples 6 and 7.
Swelling degree of 5.6% and 7.5%, which is about 5% or more, and Examples 6 and 7 for dimethylformamide as a solvent of the electrolytic solution.
72.7%, 60.1%, about 60% or more, and 42.5%, 41.4%, about 40% or more for ethylene glycol as a solvent of the electrolytic solution as shown in Examples 1 and 2. If it has a swelling degree of, it is effective in improving and reducing ESR.

Further focusing on the solubility, the solubilities of Examples 1 to 7 are single-digit numerical values in the range of 3.0% to 4.7%, but as shown in Table 2, the ESR is greatly improved and reduced as compared with the conventional example. Also from the fact that the viscosity does not increase to the extent that it adversely affects the ESR and the swelling degree is increased by the present invention, the ESR is increased.
It clearly shows that the viscosity does not adversely affect. Therefore, it can be said that a preferable embodiment having a solubility of about 15% exerts a remarkable effect on the improvement and reduction of ESR.

Further, the tensile strength of the electrolytic paper decreases depending on the type of organic substituent or the amount of introduction thereof, which may cause paper breakage of the electrolytic capacitor.
It preferably has a tensile strength of 0.5 kg or more.

Next, Examples 1, 2, 3, 6, 7 and Conventional Examples 1, 2, 3,
After leaving 6 and 7 at 105 ° C. for 1000 hours, the rate of change in capacitance was measured, and the results are shown in Table 3.

As shown in the measurement results of Table 3, the electrolytic capacitor according to the present invention has a significantly smaller decrease in capacitance than the electrolytic capacitor of the conventional example. For example, the capacitance change rate of Conventional Example 1 is -12.4%, whereas in Example 1 it is about half, -6.5%. This also applies to the other examples in which the reduction is less than half that of the corresponding conventional example. According to the present invention, the durability of the electrolytic capacitor when used at high temperatures is improved, and the life is obviously long. I understand.

EFFECTS OF THE INVENTION As described in detail above, the electrolytic capacitor according to the present invention is characterized by using electrolytic paper containing fibers in which an organic substituent is introduced into cellulose fibers and having a higher degree of swelling in an electrolytic solution. Therefore, the following operational effects are brought about. That is, after performing the element winding step using an electrolytic paper mainly composed of cellulose fibers, since the cellulose fibers are significantly swelled when the impregnation step is performed, a predetermined shortage not causing a short circuit defect during the element winding step. Even if the density is maintained, the fibers that make up the electrolytic paper expand due to swelling after impregnation and the gaps between the fibers increase, so the density of the electrolytic paper can be substantially reduced, and the equivalent series The resistance (ESR) can be reduced. Therefore, the ESR can be improved without affecting the short circuit defect rate. Therefore, the swelling degree of the electrolytic paper can be remarkably increased even with various solvents such as ethylene glycol and mixed solvents thereof, and the density of the electrolytic paper can be substantially reduced to improve the ESR. Can be made.
In particular, low-temperature characteristics and workability are good, but even when γ-butyrolactone, which has poor hydrophilicity and extremely poor ESR, is used as a solvent, it is possible to significantly swell the electrolytic paper and reduce ESR. Therefore, the range of use of γ-butyrolactone can be expanded.

Therefore, even when creating a desired high-voltage capacitor, the electrolytic paper can be kept at the desired thickness and density to improve the withstand voltage performance and prevent short-circuit defects from occurring. ESR can be reduced and the effect is particularly great. Furthermore, since the density is reduced by swelling after impregnation with the electrolyte, it is possible to increase the degree of beating of the fiber and reduce the value of CSF, and it is also possible to reduce the short circuit failure rate. is there.
That is, even if the CSF value is reduced to use high-density electrolytic paper in order to reduce short-circuit defects, it does not adversely affect the ESR because it swells after impregnation with the electrolytic solution and the density decreases substantially. .

Further, according to the present invention, the wettability of the electrolytic paper with respect to the electrolytic solution and the retention of the electrolytic solution are improved, and the amount of the electrolytic solution impregnated by swelling is also increased, so that the dry-up of the electrolytic solution is prevented, The life of the capacitor can be improved.

Further, in the electrolytic capacitor according to the present invention, the electrolytic paper swells remarkably in the electrolytic solution, so that the element is tightly wound in comparison with the conventional electrolytic capacitor and is less susceptible to vibration due to sound pressure. It is also suitable as an acoustic electrolytic capacitor.

Claims (3)

[Claims] 1. An electrolytic capacitor comprising an electrolytic paper interposed between an anode foil and a cathode foil impregnated with a predetermined electrolytic solution, wherein the electrolytic solution contains γ-butyrolactone as a solvent, and the electrolytic paper is By containing a fiber in which an organic substituent is introduced into a cellulose fiber by a chemical reaction, it has a swelling degree of 5% or more and a solubility of 15% or less with respect to γ-butyrolactone as a solvent of the electrolytic solution, and has a density of 0.4 g. / cm ³
Electrolytic capacitor characterized by being ~ 1.0 g / cm ³ . 2. An electrolytic capacitor comprising an electrolytic paper interposed between an anode foil and a cathode foil and impregnated with a predetermined electrolytic solution, wherein the electrolytic solution contains dimethylformamide as a solvent, and the electrolytic paper is cellulose. Since the fiber contains a fiber having an organic substituent introduced by a chemical reaction, the content of the fiber is 60% with respect to dimethylformamide as a solvent of the electrolytic solution.
Density 0.4g / c with above swelling and solubility below 15%
An electrolytic capacitor characterized by having m ^{3 to} 1.0 g / cm ³ . 3. An electrolytic capacitor comprising an electrolytic paper interposed between an anode foil and a cathode foil and impregnated with a predetermined electrolytic solution, wherein the electrolytic solution contains ethylene glycol as a solvent, and the electrolytic paper is cellulose. Density 0.4g / cm with a swelling degree of 40% or more and a solubility of 15% or less with respect to ethylene glycol as a solvent of the electrolytic solution by containing fibers into which organic substituents are introduced by a chemical reaction. ³
Electrolytic capacitor characterized by being ~ 1.0 g / cm ³ .