JPS63254717A - Electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to an electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolytic solution, and particularly relates to an electrolytic capacitor that is made of electrolytic paper interposed between an anode foil and a cathode foil, and particularly to The purpose is to improve the characteristics of electrolytic capacitors, such as equivalent series resistance (ESR), without affecting the defective rate.

Generally, electrolytic capacitors, especially aluminum electrolytic capacitors, are made by interposing electrolytic paper between an anode aluminum foil and a cathode aluminum foil to form a winding, and then immersing the electrolytic paper in a predetermined electrolytic solution to electrolyze it. It is manufactured by impregnating it with liquid and sealing it. The electrolytic solution usually uses ethylene glycol, dimethylformamide, etc. as a solvent, and is made by dissolving boric acid or an organic acid salt such as ammonium adipate or ammonium hydrogen maleate in these solvents and infiltrating it from both ends of the capacitor element. are doing.

Conventional aluminum electrolytic capacitors such as those mentioned above have electrolytic paper impregnated with electrolyte, so the impedance characteristics as a capacitor, especially the equivalent series resistance (hereinafter abbreviated as ESR), are high, and therefore the resistance value of the electrolyte is usually high. In addition to making the electrolytic paper thinner or less dense, attempts are being made to change the material of the electrolytic paper from ordinary wood kraft pulp to special materials such as Manila hemp pulp and esparto pulp. However, lowering the resistance value of the electrolyte may cause corrosion to the aluminum foil.
In addition, if the electrolytic paper is made thinner or its density is lowered, the short-circuit failure rate will increase when it is wound around a capacitor element, and even if no short-circuit occurs, the short-circuit failure rate will increase after the product is commercialized and put on the market. The problem is that it is expensive.

Therefore, in order to reduce the short-circuit defect rate, the thickness of the electrolytic paper should be increased, the density should be increased, and if the density is the same, the JIS standard that indicates the degree of beating of the pulp that is the raw material.
C3F (Canadian 5
It is known that by decreasing the value of standard freeass, the pulp fibers become finer due to fibrillation, and the resulting electrolytic paper becomes finely dense, which is good for improving the short-circuit defect rate. In addition, the ES of these items
The effect on R is that when the electrolytic paper is made thicker, ESR increases in a linear manner.
It has been found that increasing the density deteriorates the ESR in a quadratic manner, while the C8F value has almost no effect. That is, in order to improve ESR, it is necessary to make the electrolytic paper thinner and lower its density, contrary to improving the short-circuit failure rate.

Therefore, in order to simultaneously achieve the objectives of improving the short failure rate and ESR, it is necessary to reduce the value of C5F in order to improve the short failure rate, considering that the value of C8F does not affect ESR. It is necessary to assume that Therefore, it would be ideal to make low-density electrolytic paper from a raw material with a small CSF value. However, when electrolytic paper is made from natural cellulose pulp such as ordinary kraft pulp, Manila hemp pulp, and esparto pulp, if the C5F value is reduced, the hydrogen bonds between fibers will increase due to fibrillation. Therefore, the density of electrolytic paper always tends to be high. Therefore, when electrolytic paper of the same thickness is made using the same paper machine, the C8F value of the paper with high density is smaller than the value of C8F of the paper with low density. As a result, the ES of electrolytic capacitor
If you use low-density electrolytic paper to improve R, C5
As the value of F increases, the short failure rate increases, while when the value of C8F becomes small, the density increases and the ESR worsens, making it difficult to improve both the short failure rate and ESR. For example, for electrolytic capacitors that are compatible with high-frequency switching power supplies that require low ESR, Manila hemp pulp electrolytic capacitors with a thickness of 40 μm and a density of 0.3 to 0.4 g/ad are used. Paper is used, and in this case, the short-circuit failure rate inevitably increases to several tens of percent. On the other hand, the electrolytic paper used in large electrolytic capacitors for large-capacity, high-voltage applications is required to withstand voltage and retain electrolyte, so it has a density of 0.
High-density paper of 7 g/cd or more or double-layered paper consisting of high-density paper and low-density paper is used.

In this case, reliability against short circuit defects is high, but E
It is inevitable that the SR will increase and the heat loss due to heat generation will also increase.

On the other hand, when an electrolytic solution using ethylene glycol as a solvent is used, the resulting electrolytic capacitor has poor electrical characteristics at low temperatures due to the high viscosity of the electrolytic solution, whereas when an electrolytic solution using dimethylformamide as a solvent is used, Although the low-temperature properties are improved, dimethylformamide is easily thermally decomposed, so there is a problem with the high-temperature properties, and furthermore, it is highly toxic, so it has the disadvantage of deteriorating workability. Therefore, in order to compensate for the drawbacks of such an electrolytic solution, an electrolytic solution using γ-butyrolactone as a solvent in place of the above-mentioned solvent has recently been developed and has come into use. The electrolytic solution using γ-butyrolactone has a low viscosity, high vapor pressure, and low toxicity, so it has the advantage of improved low-temperature characteristics and workability.

My eyes are trying to open. The biggest problem with conventional electrolytic capacitors is that if you try to prevent short-circuits and improve reliability, the ESR of the resulting electrolytic capacitor will become larger than the limit value, and the ESR will decrease. If this is attempted, the number of short-circuit defects will inevitably increase, and the reliability of the electrolytic capacitor will not be achieved. That is, the reality is that as long as conventional electrolytic paper is used, the ESR cannot be reduced without substantially increasing the short-circuit failure rate.

Therefore, when the electrolytic paper is made to maintain a density and thickness that does not cause short-circuit defects during the element winding process, the element is wound without causing short-circuit defects, and after being impregnated with electrolyte, compared to conventional swelling, If the degree of swelling of the electrolytic paper by the electrolytic solution could be significantly increased, the fibers constituting the electrolytic paper would expand, and the gaps between the fibers would become larger, which would substantially lower the density of the electrolytic paper and improve ESR. can be reduced. Moreover, since it is performed after the element winding process, there is no increase in short-circuit defects.

However, in the past, electrolytic paper would swell to some extent by impregnating it with an electrolytic solution containing ethylene glycol, dimethylformamide, etc. as a solvent, but ESR
was not associated with an improvement in ESR, and no significant effect of reducing ESR occurred.

In particular, since the electrolytic solution using γ-butyrolactone as a solvent has a low viscosity and low toxicity, the electrolytic capacitor has good low-temperature characteristics and workability, but has an extremely poor ESR. This is because γ-butyrolactone is less hydrophilic than other conventional electrolytes, so the cellulose fibers hardly swell after being impregnated with the electrolyte, and the actual density of the electrolytic paper hardly decreases. by. Especially for electrolytic capacitors whose working voltage is 50V or more, the density is 0.6 to lower the short-circuit defect rate and improve withstand voltage performance.
It is desirable to use electrolytic paper of g/aJ or more, but since the fibers of such high-density electrolytic paper are strongly bonded to each other by hydrogen bonds, it is necessary to use an electrolytic solution containing γ-butyrolactone as a solvent. Then, in addition to the high density of the electrolytic paper, it also does not swell, resulting in a significant increase in ESR. In addition, because the amount of electrolyte retained is reduced, the electrolytic capacitor is more likely to dry up and have a shorter lifespan.
In addition, variations in electrical properties such as capacity, impedance characteristics, leakage current, etc. become large. Therefore, it is necessary to use an electrolytic solution in which γ-butyrolactone is mixed with other solvents such as conventional ethylene glycol, dimethylformamide, or water. Methods such as using electrolytic paper with the lowest possible density have been used in combination, but none of these methods have been sufficiently effective in reducing ESR.

Therefore, the present invention solves the problems that conventional electrolytic capacitors have and improves ESR without affecting the short-circuit failure rate. The purpose of this invention is to provide an electrolytic capacitor that uses electrolytic paper with improved electrolytic properties.

. To achieve the above object, the present invention provides an electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolytic solution, the electrolytic solution being used as a solvent. γ
- Contains butyrolactone, and the electrolytic paper contains fibers in which organic substituents are introduced into cellulose fibers by chemical reaction, so that the electrolytic paper has a swelling degree of 5% or more and 15% with respect to γ-butyrolactone as a solvent of the electrolytic solution. Density 0.4 g/cyl to 1.0 g with solubility below
/cd, and the electrolytic solution contains dimethylformamide as a solvent, and the electrolytic paper contains fibers in which organic substituents have been introduced into cellulose fibers through a chemical reaction, thereby improving the electrolytic solution. Density 0.4 with swelling degree of 60% or more and solubility of -15% or less in dimethylformamide as a solvent.
g/cd-1, 0 g/cd, and the electrolytic solution contains ethylene glycol as a solvent, and the electrolytic paper contains fibers in which organic substituents are introduced into cellulose fibers by chemical reaction. By doing so, it has a swelling degree of 40% or more and a solubility of 15% or less in ethylene glycol as a solvent of the electrolytic solution, and a density of 0.4 g/cm3 to 1.0 g/cd. The present invention provides electrolytic capacitors.

Production 1 - According to the electrolytic capacitor according to the present invention having the above configuration, the degree of swelling of the electrolytic paper increases significantly during impregnation with the electrolytic solution after the element winding process, the fibers constituting the electrolytic paper expand, and Due to the increased gap, the density of the electrolytic paper can be substantially lowered and the ESR can be reduced. Moreover, since it is performed after the element winding process, there is no increase in short-circuit defects. Therefore, even if the thickness and density of the electrolytic paper itself were set large enough to withstand high voltages to reduce the short-circuit failure rate, the ESR of the resulting electrolytic capacitor was reduced to below the desired value. An electrolytic capacitor is obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and various embodiments of the electrolytic capacitor according to the present invention will be described below.

As a result of repeated research on the swelling of electrolytic paper, the present inventor discovered that by introducing organic substituents into the cellulose fibers that make up the electrolytic paper, the electrolytic paper swells significantly in the electrolytic solution. Based on the above, various embodiments of the present invention shown below have been realized.

The electrolytic paper used in the present invention is mainly composed of cellulose, and specifically, wood pulp fibers obtained from conifers and hardwoods, non-wood pulp fibers obtained from hemp, red hemp, sisal, espart, etc. Examples include regenerated cellulose fibers such as viscose rayon and cupra rayon. These cellulose fibers contain many hydroxyl groups (O
H), and the fibrils constituting the fibers are strongly bonded by hydrogen bonds formed between hydroxyl groups. Even when such cellulose fibers are immersed in a solvent with poor hydrophilicity such as γ-butyrolactone, the solvent cannot penetrate into the hydrogen bonds formed between the fibrils.
Therefore, the fibers hardly swell. Furthermore, even in paper made of cellulose fibers, the paper is not simply formed by the entanglement of fibers; hydrogen bonds are formed at the contact areas where the fibers are entangled, and this force also causes the fibers to adhere. 6 Therefore, the present invention introduces into cellulose fibers an organic substituent that is compatible with the various electrolytic solutions described above, thereby making it easier for the electrolytic solution to penetrate into the hydrogen bonds formed between fibrils or between fibers. The electrolytic paper itself is swollen in the electrolytic solution and the bonding force between the fibers in the electrolytic solution is weakened to increase the swelling of the electrolytic paper in the electrolytic solution.

As a chemical reaction for introducing an organic substituent, all reactions caused by cellulose can be used, such as graft polymerization reaction to cellulose and substitution reaction of hydroxyl groups in cellulose, but in particular, esterification reaction of hydroxyl groups contained in cellulose can be used. 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 an organic substituent, it is necessary that the cellulose fibers maintain the same fiber morphology as before the reaction even after the reaction is completed, and that they do not dissolve excessively in the electrolytic solution. Therefore, the chemical reactions for introducing these organic substituents are carried out under conditions that are milder than those for producing general cellulose derivatives, and in the hydroxyl substitution reaction, only one of the hydroxyl groups contained in cellulose is used. Preferably, the reaction conditions are such that only 50% or more of the hydroxyl groups are substituted.1 For example, if most of the hydroxyl groups are substituted, the resulting fibers may become brittle or may not retain their fiber morphology, and electrolytic It may not be possible to form paper.

Furthermore, when an electrolytic capacitor is manufactured using such fibers, most of the fibers dissolve when the electrolytic paper is immersed in an electrolytic solution, causing short-circuit defects in the resulting electrolytic capacitor or due to the viscosity of the electrolytic solution. This also means that the ESR increases with the increase.

Therefore, the present invention improves and reduces the ESR by increasing the degree of swelling of the electrolytic paper with respect to the electrolytic solution, thereby substantially lowering the density of the electrolytic paper after being impregnated with the electrolytic solution.
In order to prevent the swelling degree of the electrolytic paper from increasing more than necessary and resulting in a viscosity of the electrolytic solution that adversely affects ESR, conditions are appropriately selected to obtain the degree of swelling necessary to obtain a predetermined ESR value. It is something to do.

The substituent to be introduced into the cellulose fibers may be any substituent that does not contain elements that cause corrosion of electrolytic capacitors such as chlorine CL, bromine Br, and iodine, but the proportion of carbon such as alkyl groups having 8 or more carbon atoms, allyl groups, etc. If a large number of substituents are introduced, the cellulose fiber becomes extremely hydrophobic, which reduces the strength of the electrolytic paper and may cause trouble during the element winding process. In addition, the proportion of carbon is small, and the carboxyl group (
If a substituent having a dissociative polar group such as -COOH) or a sulfonic acid group (-S o3 H) is introduced, the swelling property will decrease, which is not preferable. Therefore, it is necessary to select the organic substituent to be introduced depending on the degree of polarity or hydrophilicity of the electrolytic solution. Preferably, it is an organic substituent in which one or more types of hydroxyl group, ether group, amino group, nitrile group, amide group, imide group, carbonyl group, etc. are bonded to an alkyl group, and the substituent has appropriate polarity. This is desirable. Further, in the case of a substituent consisting only of an alkyl group, it is desirable that the number of carbon atoms is 5 or less. Particularly preferred chemical reaction examples are shown below.

(A) Esterification reaction (1) Reaction with acid chloride CELL-OH+RCOCL 4 CELL-
0-C-R(2)r! ! ! Reaction with anhydride CELL-OH+RN=C=O-) CELL-0-
C-R (Note) R indicates any of CH3, C2H5, or C3H7 (7).

CF and LL represent cellulose chains.

(B) Etherification reaction (4) Reaction with alkyl halide CELL -OH+ RCL → CELL -0-R
(5) Reaction with dialkyl sulfuric acid (Note) R indicates CH3, C2H5, C3H, (7) which one.

CELL indicates a cellulose chain.

(6) Reaction with alkylene oxide (Note) R represents H, CH3, or C2Is, n is 1
CI! LL represents a cellulose chain.

(7) Reaction with vinyl compounds (Note) R is CN, CONH2, OC2H5, C0tJ
Indicates either I3 or COC2H5.

CBLL indicates cellulose chain.

(C) Acetalization reaction (8) Acetal reaction OH (Note) R is C) 13, C2H5-C3H7, c4 H9
Indicates either.

CELL indicates a cellulose chain.

As mentioned above, it is preferable to replace a part of the hydroxyl groups (OH) in cellulose with the above substituents using (A) esterification reaction, (B) etherification reaction, and (C) acetalization reaction. The electrolytic paper used in the invention does not need to be composed only of cellulose fibers into which organic substituents have been introduced;
It may be paper made by mixing ordinary cellulose fibers or other chemical fibers such as polypropylene or polyester with cellulose fibers into which organic substituents have been introduced. That is, it is sufficient that the electrolytic paper substantially contains cellulose fibers into which organic substituents have been introduced.

In producing the electrolytic paper according to the present invention, organic substituents are introduced into the cellulose fibers constituting the paper in the state of paper after papermaking, using a low-temperature plasma reaction method or radiation graft polymerization method. Also good. However, in order to remove reaction by-products when introducing organic substituents into cellulose fibers and to remove substances that cause corrosion of electrolytic capacitors, such as reaction aids, it is necessary to thoroughly wash the cellulose fibers after the reaction is complete. It is. Therefore, it is desirable to introduce an organic substituent in the fiber state and then use a method such as paper making to make electrolytic paper. There are no particular limitations on the paper-making method, and manual paper-making or mechanical paper-making methods 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 significantly in the electrolytic solution and widens the fiber gaps, thereby substantially lowering the density and reducing the ESR of the resulting electrolytic capacitor. Therefore, in the case of the present invention, the ESR reduction effect becomes greater as higher density electrolytic paper is used, and the ESR reduction effect is smaller with lower density paper (for example, a density of 0.3 g/cn? or less).

Therefore, the density of electrolytic paper is 0.4 to 1.0 g/cI+? It is better to use something of a certain degree. Furthermore, if the degree of swelling becomes extremely high, some of the fibers will dissolve in the electrolytic solution during impregnation, and the viscosity of the electrolytic solution will increase, so the viscosity of the electrolytic solution will not be such that it will adversely affect ESR. Moreover, if the density of the electrolytic paper after impregnated with electrolytic solution is substantially lowered to effectively reduce ESR, some of the fibers will be dissolved in the electrolytic solution during impregnation, and the electrolytic solution will be reduced. Since the viscosity will increase, E
ES without the viscosity of the electrolyte that would adversely affect SR, and by substantially lowering the density of the electrolytic paper after impregnated with the electrolyte.
A preferable range for effectively reducing R is that the electrolytic paper has a swelling degree of 5% or more and a solubility of 15% or less in 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 in dimethylformamide as a solvent of the electrolytic solution. Furthermore, it has a swelling degree of 40% or more and a solubility of 15% or less in ethylene glycol as a solvent of the electrolytic solution.

Below, various examples for obtaining an electrolytic capacitor according to the present invention and the results of measuring the swelling degree, solubility, etc. of the electrolytic paper used, and the ESR, short-circuit failure rate, etc. of the obtained electrolytic capacitor are shown. In addition, each measurement value of each sample was performed by the following measurement method and apparatus. □ (1) Manufacturing method of electrolytic capacitor After forming an electrolytic capacitor element by interposing electrolytic paper between the tabbed anode foil and cathode foil so that the two electrodes do not come into contact with each other and rolling it up, it is impregnated with the specified electrolyte solution. 50WV by the usual method of aging, sealing in a case, and aging.
, a 220μF 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 C2301 (electrolytic capacitor paper).

■Swelling degree The degree of swelling was determined by stacking 10 sheets of electrolytic paper as a test piece.

The thickness is measured with a micrometer (A μm), and then the test piece is immersed in γ-butyrolactone, a specified solvent, or a specified electrolyte for exactly 15 minutes. Thereafter, the test piece was taken out and its thickness was measured using a micrometer while it was still wet (BILm).

A micrometer specified in JIS C2301 (electrolytic capacitor paper) was used, and the degree of swelling was determined using the following formula.

■Solubility For solubility, use approximately 2g of electrolytic paper as a test piece, dry it at 105℃ until it reaches a constant weight, and then accurately measure its weight (Cg).
Next, the test piece is immersed in γ-butyrolactone, a predetermined solvent, or a predetermined electrolyte at 25° C. for 24 hours. After that, the test piece was passed through a 200-mesh wire mesh and taken out.
Wash on a wire mesh using deionized water. This test piece was dried again at 105° C. until it had a constant weight, its weight was accurately measured (Dg), and the solubility was determined using the following formula.

(3) Evaluation method for electrolytic capacitors ■Short-circuit failure rate After winding electrolytic paper together with anode foil and cathode foil to form an electrolytic capacitor element, use a tester to check continuity due to a short between the two electrodes without impregnating them with electrolyte. did.

The short-circuit failure rate was determined by inspecting 500-1000 devices and determining the ratio of short-circuit devices to the total number of devices.

■ESR (Equivalent Series Resistance) The ESR of an electrolytic capacitor is 1000Hz at a temperature of -40℃.
It was measured by an LCR meter at the frequency of .

■Capacitance The capacitance of the electrolytic capacitor was measured using an LCR meter at a temperature of 20°C and a frequency of 120H2.

■Leakage current The leakage current of the electrolytic capacitor is calculated by loading 50V DC.
The current value was measured after 5 minutes.

■Amount of electrolyte The difference in weight of the electrolytic capacitor before and after being impregnated with electrolyte was measured to determine the amount of electrolyte impregnated into the element.

(Example 1) 100g of Manila hemp pulp was mixed with 500ml of 2% NaOH aqueous solution.
After immersion in Q, the pulp was centrifuged to remove excess NaOH aqueous solution to give a pulp concentration of 35%.

70 g of acrylonitrile was added to this alkali-treated pulp and reacted at 20° C. with slow stirring for 2 hours to cyanoethylate the Manila hemp pulp.

After thoroughly washing this cyanoethylated Manila hemp pulp with ion-exchanged water, it was converted into C8F 670 by a PFI mill.
The product was beaten to mQ and further hand-sheeted using ion-exchanged water to produce a hand-sheet with a thickness of 40.3 μm and a density of 0.406 g/al. Next, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte was made by dissolving ammonium borodisalicylate in γ-butyrolactone, and the specific resistance was adjusted to 200Ω・am (
20°C).

(Example 2) Cyanoethylated Manila hemp pulp obtained in the same manner as in Example 1 was beaten to C8F600mQ using a PFI mill, and hand-sheeted using ion-exchanged water to a thickness of 40.8 μm.
A handmade sheet with a density of 0.508 g/j was prepared. Next, an aluminum electrolytic capacitor was manufactured using the handmade sheet as electrolytic paper. The impregnated electrolyte was prepared by dissolving ammonium borodisalicylate in a mixed solvent of 70% γ-butyrolactone and 30% dimethylformamide.
The specific resistance was adjusted to 200Ω·1 (20°C).

(Example 3) Cyanoethylated Manila hemp pulp obtained in the same manner as in Example 1 was beaten to C8C3F34O using a PFI mill, and hand-sheeted using ion-exchanged water to a thickness of 40.0 μm.
A handmade sheet having a density of 0.595 g/cof was prepared.Then, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte is γ
- Ammonium borodisalicylate is dissolved in butyrolactone, and the specific resistance is adjusted to 200Ω·ell (20°C).

(Example 4) 100 kg of coniferous wood pulp was mixed with 2% NaOH aqueous solution 0.00 kg.
5-, the pulp was squeezed using a screw press to remove excess NaOH aqueous solution to give a pulp concentration of 40%.

This alkali-treated pulp was placed in a stainless steel pressure container, and the air inside the container was replaced with nitrogen gas.
Put 50 kg of butylene oxide into a container and seal it tightly.
The softwood pulp was hydroxybutylated by reacting at 80° C. for 60 minutes.

After thoroughly washing this hydroxybutylated coniferous wood pulp with ion-exchanged water, it was refined in a double disc refiner to a C5F content of 5 mg or less, and then paper was made using a Fourdrinier paper machine using ion-exchanged water to a thickness of 25 mm. .4pm,
A paper with a density of 0.854 g/Ci was obtained.

This paper was then used as electrolytic paper to fabricate an aluminum electrolytic capacitor. The impregnated electrolyte was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water, and adjusting the specific resistance to 200Ω・01 (at 20℃).
).

(Example 5) Hydroxybutylated coniferous wood pulp obtained in the same manner as in Example 4 was used as a raw material, and paper was made using a fourdrinier/circle screen combination paper machine to form high-density paper and low-density paper. A double sheet of paper was created. During papermaking, hydroxybutylated coniferous wood pulp is beaten to less than C3F3m12 using a double disc refiner and used as a Fourdrinier papermaking raw material, with a thickness of 20.3pm and a density of 0.801g/c.
Ar high-density paper is made in the fourdrinier section, and unbeaten hydroxybutylated coniferous wood pulp is made in the circular mesh section, and the paper is made into a paper with a thickness of 60.8 μm and a density of 0.645 g/cr.
I created a double sheet of paper for i.

Next, this double-layered paper was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water, and adjusting the specific resistance to 200Ω・elm (
20°C).

(Example 6) 100 kg of Manila hemp pulp was mixed with 3% NaOH aqueous solution 0
．． 5-, the pulp was squeezed using a screw press to remove excess NaOH aqueous solution, resulting in a pulp concentration of 39%. This alkali-treated pulp was placed in a stainless steel pressure-resistant container, the air in the container was replaced with nitrogen gas, 50 kg of propylene oxide was then placed in the container, and the container was sealed and heated to 50°C.
The Manila hemp pulp was hydroxypropylated by reacting for 70 minutes. After thoroughly washing this hydroxypropylated Manila hemp pulp with ion-exchanged water, it was washed with C3F using a beater.
The product was beaten to 485 mQ, and paper was made using a cylinder paper machine using ion-exchanged water as water to obtain paper with a thickness of 40.1 μm and a density of 0.603 g/cd.

This paper was then used as electrolytic paper to fabricate 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, and adjusting the specific resistance to 200 Ω·al (20° C.).

(Example 7) Add 500 mA of acetic anhydride to 100 g of Manila hemp pulp,
The Manila hemp pulp was acetylated by reacting at 120° C. for 1 hour with stirring. After thoroughly washing this acetylated Manila hemp pulp with ion-exchanged water, it was processed into C8 in a PFI mill.
It was beaten to C3F33O and then hand-made using ion-exchanged water to give a thickness of 40.5 μm, a density of 0, and 606 g.
/cd (1) A handmade sheet was created.

Next, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the resistivity to 200 Ω·ell (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 cellulose fibers into which no organic substituent was introduced was prepared according to the conventional example described below.

(Conventional example 1) Manila hemp pulp is beaten in a PFI mill to produce C3F675m
It was set as g. This beaten pulp was hand-sheeted using ion-exchanged water to create a hand-sheet with a thickness of 41.0 μm and a density of 0.402 g/cd.

Next, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte is γ-
This is a conventional electrolytic capacitor corresponding to Embodiment 1, in which the resistivity was adjusted to 2000.degree. (20.degree. C.) by electrolyzing ammonium borodisalicylate to butyrolactone.

(Conventional Example 2) Manila hemp pulp is beaten in a PFI mill to produce C3F600
It was set as m12. This beaten pulp was hand-made using ion-exchanged water to a thickness of 39.8 μm and a density of 0.511 g/J.
I created a handmade sheet.

Next, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte is γ
- 70% butyrolactone and 30% dimethylformamide
This is a conventional electrolytic capacitor corresponding to Example 2, in which ammonium borodisalicylate is dissolved in a mixed solvent with borodisalicylate and the specific resistance is adjusted to 200Ω·1 (20° C.).

(Conventional Example 3) Manila hemp pulp is beaten in a PFI mill to produce C8F 53
It was set to 0 mQ. This beaten pulp was hand-made using ion-exchanged water to a thickness of 39.7 μm and a density of 0.603 g.
/cd handmade sheet was created.

Next, this handmade sheet was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte is γ
- This is a conventional electrolytic capacitor corresponding to Example 3, in which ammonium borodisalicylate is dissolved in butyrolactone and the resistivity is adjusted to 200Ω·1 (20° C.).

(Conventional Example 4) Coniferous wood pulp is processed into C3 using a double disc refiner.
It was beaten to F5mQ or less and made into paper using a Fourdrinier paper machine using ion-exchanged water, with a thickness of 25.1 μm and a density of 0.85.
After obtaining 6 g/c+J paper, this paper was used as electrolytic paper to manufacture an aluminum electrolytic capacitor. The impregnated electrolyte was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water to reduce the specific resistance to 20%.
It was adjusted to 0 Ω・cm (20°C), and Example 4
This is a conventional electrolytic capacitor compatible with

(Conventional Example 5) Using softwood pulp as a raw material, paper was made using a fourdrinier/cylinder combination paper machine.

Double-layered paper was created by combining high-density paper and low-density paper. For paper making, coniferous wood pulp is beaten in a double disc refiner to CSF 5 mQ or less, and used as a Fourdrinier papermaking raw material, with a thickness of 20°5 μm and a density of 0.5 μm.
High-density paper of 797 g/cd is made in the Fourdrinier section, and unbeaten softwood pulp is made in the circular mesh section to form a paper with a thickness of 60.5 μm.

A double-layered paper with a density of 0.644 g/cd was prepared.

Next, this double-layered paper was used as electrolytic paper to produce an aluminum electrolytic capacitor. The impregnated electrolyte solution was prepared by dissolving ammonium adipate in a mixed solvent of 90% ethylene glycol and 10% water, and adjusting the specific resistance to 200Ω・am (2
This is a conventional electrolytic capacitor corresponding to Example 5.

(Conventional Example 6) Manila hemp pulp is beaten with a beater to produce C3F480
It was set as mQ. This beaten pulp was made into paper using a circular mesh paper machine using ion-exchanged water as water to a thickness of 39.7 μm.
A paper with a density of 0.607 g/crl was obtained.

This paper was then used as electrolytic paper to fabricate an aluminum electrolytic capacitor. The impregnated electrolyte was prepared by dissolving ammonium hydrogen maleate in a mixed solvent of 50% dimethylformamide and 50% ethylene glycol to reduce the specific resistance to 2.
This is a conventional electrolytic capacitor corresponding to the sixth embodiment.

(Conventional Example 7) Manila hemp pulp is beaten in a PFI mill to produce C8C3F3
It was set to 8O. This beaten pulp was hand-made using ion-exchanged water to a thickness of 39.5 μm and a density of 0.605 g/cI.
I made 1 handmade sheet.

Next, use this handmade sheet as electrolytic paper.

Manufactured an aluminum electrolytic capacitor. Note that the impregnated electrolytic solution was prepared by dissolving ammonium borodisalicylate in dimethylformamide and adjusting the resistivity to 200Ω·min (20° C.), and was a 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 immersed in the solvent used in the electrolytic solution and the electrolytic solution used, and the degree of swelling was measured.

The results are shown in Table 1 together with the measurement results of thickness, density, and tensile strength, and also the capacitor characteristics of capacitance, leakage current, and ESR of the electrolytic capacitors according to Examples 1 to 7 and Conventional Examples 1 to 7. Table 2 shows the measurement results, short-circuit defect rate, and electrolyte amount.

Examples 1 and 3 Conventional examples 1 and 3: γ-butyrolactone 100
% Example - Conventional example 2: γ-butyrolactone 7
0% + dimethylformamide 30% Examples 4, 5 & Conventional Examples 4, 5: Ethylene glycol 90
%10% water 10%Example Ue Conventional Example 6 Nidimethylformamide 50%10ethylene glycol 50% Example 7 & Conventional Example 7 Nidimethylformamide 1
00% Table 2 As shown in the measurement results in Tables 1 and 2, the electrolytic paper made of cellulose fibers into which organic substituents have been introduced according to the present invention has a higher resistance to various electrolytes and γ-butyrolactone than conventional electrolytic paper. The degree of swelling of the electrolytic solution in various solvents is significantly increased, and as a result, the density of the electrolytic paper after impregnation with the electrolytic solution is substantially reduced, and the ESR is significantly improved and reduced. for example,
Example 1 has a thickness of 40.3 pm and a density of 0.406 g/cd.
, the thickness of Conventional Example 1 is 41.0 μm, the density is 0.40
Although the electrolytic paper has approximately the same thickness and density as 2 g/J, the degree of swelling in the electrolytic solution using 100% γ-butyrolactone as the solvent is 0.2% in Conventional Example 1, which shows almost no swelling. On the other hand, the swelling degree of Example 1 was 69.7%, which clearly shows that the swelling degree of the electrolytic paper was greatly increased. Furthermore, the degree of swelling increased from 54.7% to 90.7% with respect to dimethylformamide, and increased from 35.6% to 42.5% with respect to ethylene glycol. As a result, ESR is 0 for conventional example 1.
．． 72Ω, whereas in Example 1 it was 0°57Ω, which is a significant decrease. Moreover, the short defect rate is 9.0%.
8.8%, which is not only unaffected, but also a slight improvement or decrease. In addition, the amount of electrolyte was changed from 0.693g to 0.
．． The total weight has increased to 792 g, and in combination with the improved compatibility between the electrolytic paper and the electrolytic solution due to the introduction of the organic substituent, dry-up of the electrolytic solution can be prevented and the life of the electrolytic capacitor can be extended.

Furthermore, in Example 4 and Conventional Example 4, which have approximately the same thickness and density, the degree of swelling in an electrolytic solution containing 90% ethylene glycol and 10% water as a solvent is 38.6% in Conventional Example 4. , Example 4 has a large swelling of 100.1%, and as a result, the ESR of Conventional Example 4 is 12.38Ω, whereas Example 4 is greatly improved and decreased to 5.36Ω. The defective rate was also the same at 1.4%, so it was not affected.

Furthermore, in Example 6 and Conventional Example 6, which have approximately the same thickness and density, the degree of swelling in an electrolytic solution using 100% dimethylformamide as a solvent is 50.8% in Conventional Example 6, and 61% in Example 6. .9%, the degree of swelling is lower than in other examples, but the ESR is 1.86Ω to 1.08Ω.
It clearly decreases to Ω.

The degree of swelling was 0.2% for γ-butyrolactone as a solvent of the electrolytic solution, as shown in Conventional Example 6.7. As shown in Example 6.7, the degree of swelling is 5.6%, 7.5%, which is about 5% or more. % and approximately 60%
The above degree of swelling was further increased to 42.0 as shown in Example 1.2 for ethylene glycol as a solvent for the electrolytic solution.
If the swelling degree is approximately 40% or more, such as 5% or 41.4%, it is effective in improving or reducing ESR.

Furthermore, focusing on solubility, the solubility of Examples 1 to 7 is a single-digit value in the range of 3.0% to 4.7%,
As shown in Table 2, the ESR has significantly improved and decreased compared to the conventional example, which indicates that the viscosity has not increased to the extent that it has a negative effect on the ESR, and that even if the swelling degree is increased by the present invention, the ESR This clearly shows that the viscosity does not have a negative impact on the product. Therefore, it can be said that a solubility of up to about 15% is a preferable embodiment that has a remarkable effect on improving and reducing ESR.

Furthermore, depending on the type of organic substituent or the amount introduced, the tensile strength of the electrolytic paper decreases, which may cause paper breakage of the electrolytic capacitor, so in the case of the present invention.

It is preferable that the electrolytic paper has a tensile strength of at least 0.5 kg or more.

Next, Examples 1.2.3, 6.7 and Conventional Example 1.2゜3.6
．． After leaving Sample No. 7 at 105° C. for 1000 hours, the capacitance change rate was measured, and the results are shown in Table 3.

Table 3 As shown in the measurement results in Table 3, the electrolytic capacitor according to the present invention exhibits a significantly smaller decrease in capacitance than the conventional electrolytic capacitor. For example, while the rate of change in capacitance in Conventional Example 1 is -12.4%, in Example 1 it remains at approximately half -6.5%. Even in other examples, the reduction was less than half of the corresponding conventional example, and according to the present invention, the durability of electrolytic capacitors when used at high temperatures is improved, and the lifespan is clearly extended. I understand that.

11" Column Button As explained in detail above, the electrolytic capacitor according to the present invention uses electrolytic paper which contains fibers in which organic substituents have been introduced into cellulose fibers and has an increased degree of swelling with respect to an electrolytic solution. It is characterized by the presence of

The effects described below are brought about. In other words, after the element winding process is performed using electrolytic paper mainly composed of cellulose fibers, the cellulose fibers swell significantly when the impregnation process is performed, so that sheet defects are not caused during the element winding process. Even if the predetermined density of the electrolytic paper is maintained, the fibers constituting the electrolytic paper expand due to swelling after impregnation, and the gaps between the fibers become larger, so the density of the electrolytic paper can be substantially lowered. , the equivalent series resistance (ESR) can be reduced. Therefore, ESR can be improved without affecting the short-circuit failure rate. Therefore, the degree of swelling of electrolytic paper can be significantly increased even in various solvents such as ethylene glycol and mixed solvents thereof, and the density of electrolytic paper can be substantially lowered, improving and reducing ESR. can be done. In particular, it has good low temperature properties and workability, but it has poor hydrophilicity and extremely high ESR.
Even when γ-butyrolactone, which has poor performance, is used as a solvent, the electrolytic paper can be significantly swollen, the ESR can be reduced, and the range of use of γ-butyrolactone can be expanded.

Therefore, when creating a desired high-voltage capacitor, it is necessary to make the electrolytic paper maintain the desired thickness and density to improve withstand voltage performance and prevent short-circuiting, and also to prevent swelling of the electrolytic paper during impregnation. This is particularly effective in reducing ESR. Furthermore, as the fiber swells after being impregnated with the electrolytic solution, the density substantially decreases, so it is possible to increase the degree of beating of the fiber and reduce the C8F value, which also reduces the short-circuit defect rate. be. In other words, even if a high-density electrolytic paper is used with a small C8F value to reduce short-circuit defects, it will swell after being impregnated with an electrolytic solution and the density will substantially decrease, resulting in a poor ESR.
It will not have any negative impact on.

Furthermore, 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 dry-up of the electrolytic solution is prevented, and electrolysis Capacitor life can be improved.

Furthermore, in the electrolytic capacitor according to the present invention, the electrolytic paper swells significantly in the electrolyte, so the element is wound more tightly than in conventional electrolytic capacitors, making it less susceptible to vibrations caused by sound pressure, etc. Therefore, it is suitable as an electrolytic capacitor for acoustics.

Claims (3)

[Claims] (1) An electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolytic solution, wherein the electrolytic solution contains γ-butyrolactone as a solvent, and the electrolytic paper is made of cellulose fibers. By containing fibers into which organic substituents have been introduced through a chemical reaction, the fibers have a swelling degree of 5% or more and a solubility of 15% or less in γ-butyrolactone as a solvent of the electrolytic solution, and a density of 0.4 g/ cm
An electrolytic capacitor characterized in that it is ^3 to 1.0 g/cm^3. (2) In an electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolytic solution, the electrolytic solution contains dimethylformamide as a solvent, and the electrolytic paper is attached to cellulose fibers. By containing fibers into which organic substituents have been introduced through a chemical reaction, the fibers have a swelling degree of 60% or more and a solubility of 15% or less in dimethylformamide as a solvent of the electrolytic solution, and have a density of 0.4 g.
/cm^3 to 1.0g/cm^3. (3) In an electrolytic capacitor in which electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a predetermined electrolytic solution, the electrolytic solution contains ethylene glycol as a solvent, and the electrolytic paper contains cellulose fibers. By containing fibers into which organic substituents have been introduced through a chemical reaction, the fibers have a swelling degree of 40% or more and a solubility of 15% or less in ethylene glycol as a solvent of the electrolytic solution, and a density of 0.4 g/c.
An electrolytic capacitor characterized in that it has a capacitance of m^3 to 1.0 g/cm^3.