JP2006245629A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor in which short circuit failure rate is improved without having an adverse effect on the impedance characteristics by employing a novel electrolytic sheet having low density and tensile strength enhanced sharply without covering the air gap between fibers, and productivity is enhanced. <P>SOLUTION: In the electrolytic capacitor where an electrolytic sheet is interposed between an anode foil and a cathode foil, the electrolytic sheet is made of unbeaten or slightly beaten natural vegetable fibers by a cylinder machine. It is then impregnated, under dry sheet state, with refining solution of paper force reinforcement agent from which impurities are removed thus obtaining an electrolytic capacitor having a density of 0.20-0.70 g/cm<SP>3</SP>, tensile strength of 1.1 kg/15 mm or above, and a thickness of 20-70 μm where the impurity of the electrolytic sheet is 500-650 V when it is evaluated by chemical treatment properties, and ESR is 0.2 Ω/1 kHz or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolytic capacitor configured by interposing electrolytic paper between an anode foil and a cathode foil, and in particular, has a low density and a greatly improved tensile strength, and further, inter-fiber voids are shielded. By using a novel electrolytic paper that does not occur, the short defect rate is improved without adversely affecting the impedance characteristics, and the productivity is improved.

  In general, electrolytic capacitors, particularly aluminum electrolytic capacitors, are formed by winding electrolytic paper between an anode aluminum foil and a cathode aluminum foil to form a capacitor element, and this capacitor element is immersed in a liquid electrolyte. It is made by impregnating with electrolyte and sealing. As an electrolytic solution, ethylene glycol (EG), dimethylformamide (DMF), or γ-butyrolactone (GBL) is usually used as a solvent, and organic acid salts such as boric acid, ammonium adipate, and ammonium hydrogen maleate are dissolved in these solvents. It is manufactured by infiltrating from both ends of the capacitor element.

  Since these conventional aluminum electrolytic capacitors are impregnated with electrolytic solution in electrolytic paper, the impedance characteristics as a capacitor, in particular, the equivalent series resistance (hereinafter abbreviated as ESR) is likely to be high, so that the impedance characteristics are improved. In addition to the means to lower the resistance of the electrolyte or to reduce the thickness or density of the electrolytic paper, the means to change the raw material of the electrolytic paper from ordinary wood craft pulp to conifer wood pulp, manila hemp pulp, esparto pulp, etc. It has been. However, lowering the resistance value of the electrolyte causes corrosiveness to the aluminum foil. On the other hand, thinning the electrolytic paper or lowering the density inevitably reduces the tensile strength and increases the short-circuit defect rate. Even if there is no short circuit, there is a drawback that the short defect rate after being commercialized and put on the market becomes high.

  Therefore, in order to reduce the short-circuit defect rate, the thickness of the electrolytic paper is increased, the density is increased, and in the case of the same density, CSF (Canadian Standard) according to JIS P 8121 indicating the degree of beating of the raw material pulp. It is known that if the value of (Freeness) is reduced, the pulp fibers become fibrillated and become finer, the resulting electrolytic paper becomes dense, the tensile strength increases, and the short-circuit defect rate is improved. Further, it has been found that the effect of these items on ESR is that the ESR is linearly deteriorated when the electrolytic paper is thickened, and that the ESR is deteriorated quadratically when the density is increased. That is, in order to improve 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 both the objectives of improving the short defect rate and improving the ESR, as described above, the raw material of the electrolytic paper is changed from a normal wood craft pulp to a softwood wood pulp, a Manila hemp pulp, an esparto pulp, or the like. Attempts have been made to produce a thin, low density and dense electrolytic paper by changing to a smaller pulp. The most commonly used blended paper as an electrolysis paper is a blend of Manila hemp pulp and esparto pulp. By mixing esparto pulp with a thin fiber diameter and high rigidity into Manila hemp pulp, the appearance of Manila hemp is improved. Even if the roughness is eliminated and the density is low, a dense electrolytic paper can be obtained (see Patent Document 1).

  Furthermore, by using a sisal pulp that does not easily increase the density of the paper that has been made by beating the raw material as the raw material for the electrolytic paper and reducing the numerical value of the CSF, an electrolytic paper having a low density with a raw material having a low CSF is obtained. (Refer to Patent Document 2).

  Further, in order to improve the short-circuit defect rate, it is necessary to improve the resistance of the electrolytic paper to foil burrs. It is also important to improve the tensile strength along with the thickness, density, denseness, and pinholes. Therefore, as described above, in addition to reducing the value of CSF, low melting point heat fusion fibers such as vinylon binder fiber and polyethylene fiber are mixed in the raw material and melted at the temperature in the drying process, and the adhesive strength between the fibers There are known means for increasing the tensile strength by imparting a tensile strength, and means for increasing the tensile strength by subjecting paper mixed with thermoplastic fibers such as polypropylene fiber and nylon fiber to heat treatment by secondary processing and fusing. In these means, in addition to the above-mentioned natural plant fiber, in addition to synthetic fibers such as viscose rayon fiber, polypropylene fiber, polyimide fiber, and aramid fiber, inorganic fibers such as glass fiber and alumina silica fiber are also blended at low density, and It is possible to obtain a paper having a high level of tensile strength with a high porosity.

In order to increase the general tensile strength of paper, starch, vegetable gum, semi-synthetic polymer, synthetic polymer, etc. are added to the raw material suspension during the manufacturing process, and fixed to the fiber surface layer to bond the fibers together. Means for increasing the value are known.
Japanese Examined Patent Publication No. 61-45379 Japanese Patent Laid-Open No. 62-126622

  However, in Patent Document 1 in which the Manila hemp pulp and the esparto pulp are mixed, since the esparto pulp is very rigid, the compatibility with the Manila hemp pulp is poor, and mixing the esparto pulp has extremely high tensile strength. It will decrease. Therefore, it is necessary to reduce the CSF value of the Manila hemp pulp, increase the hydrogen bond acting between the fibers by generating an infinite number of fibrils, increase the strength of the electrolytic paper, and maintain the tensile strength. However, recently, the fiber gaps are filled by the fibrils of Manila hemp pulp to increase this tensile strength, so even if low density paper can be made in the presence of rigid esparto pulp, it will adversely affect ESR. It has been found that there is.

  On the other hand, according to Patent Document 2, which uses sisal pulp as a raw material, sisal pulp has a fiber diameter that is substantially the same as that of Manila hemp pulp and has higher rigidity than Manila hemp pulp. Moreover, it has been found that due to the appearance roughness, the tensile strength is low, and the paper breakage and short-circuit defect rate in the element winding process increases.

  Also, means for mixing heat-bonded fibers that can increase the tensile strength without reducing the CSF value and melting them in a drying process to increase the bonding between the fibers, or mixing the thermoplastic fibers, In the means to increase the tensile strength by fusing by the heat treatment of the next processing, the binder fiber and thermoplastic fiber are melted to form a film (film shape), shielding the fiber gap and hindering the ionic conduction of the electrolyte solution, so low density It has been found that even if the tensile strength of paper is strong, the ESR results in deterioration.

  Furthermore, starch, vegetable gums, semi-synthetic polymers, synthetic polymers, etc. are added to the raw material suspension during the manufacturing process, which is a general means for increasing the tensile strength of paper, and fixed on the fiber surface layer so that the mutual fiber The means for increasing the bond strength is effective to some extent for a high-density raw material that can reduce the CSF value to generate microfibrils and increase the fiber surface area. However, it is not always effective for the low ESR required especially for electrolytic paper in recent years. That is, it is important to produce electrolytic paper at a lower density in order to lower the ESR. For this reason, it is necessary to produce the raw material based on unbeaten raw materials or raw materials that have been slightly beaten. This is because the density increases inevitably if the raw fiber is beaten and the CSF value is reduced. Therefore, in the electrolysis paper aiming at low ESR, the surface area of the fiber does not increase because an unbeaten raw material or a raw material that has been slightly beaten is used. Therefore, even if the paper strength enhancer is internally added to the raw material suspension during the manufacturing process, the fixing yield is extremely poor, and a significant increase in tensile strength cannot be expected. As an electrolytic paper for the purpose of reducing ESR, The tensile strength is not sufficient.

In addition, as long as 100% of the above-mentioned various natural plant fibers are used, the lower limit density of the electrolytic paper is 0.27 g / cm ³ , and if the density is lowered below this, paper breakage occurs at the winding stage of electrolytic paper production. Even if it can be manufactured, the current situation is that it is not suitable for practical use because of frequent paper cutting in the capacitor element winding process.

  On the other hand, in the process of manufacturing a capacitor, there is a problem of electrolytic paper breakage when winding it on the capacitor element, and in particular, the factor that significantly impedes the productivity due to the increase in electrolytic paper breakage with the shift to low density paper due to the recent low ESR. There is a need for improvement.

  Therefore, the present invention has been made in view of the above circumstances, and has a low density and a greatly improved tensile strength, and by using a novel electrolytic paper that does not shield inter-fiber voids. It is an object of the present invention to provide an electrolytic capacitor that improves the productivity by improving the short-circuit defect rate without adversely affecting the impedance characteristics and eliminating the paper breakage in the capacitor element winding process.

In order to achieve the above object, the present invention provides an electrolytic capacitor in which electrolytic paper is interposed between an anode foil and a cathode foil. The electrolytic paper is made of natural plant fibers that have been unbeaten or slightly beaten. In addition to making paper using a circular paper machine as a raw material, and impregnating and applying a purified solution of a paper strength enhancer from which impurities have been removed in a dry paper state after paper making, the density is 0.20 to 0.70 g / cm ³ , An electrolytic capacitor having a tensile strength of 1.1 kg / 15 mm or more, a thickness of 20 to 70 μm, 500 to 650 V when an impurity of electrolytic paper is evaluated by chemical conversion, and an ESR of 0.2 Ω / 1 kHz or less is provided. Then, a structure in which the degree of beating of natural plant fibers is 500 ml to 720 ml in terms of CSF, and a paper strength enhancer purified solution from which impurities are removed is impregnated and applied so as to be fixed at the contact points between the fibers in the paper layer. By impregnating and applying a refined solution of the paper strength enhancer from which the impurities are removed, the refined solution of the paper strength enhancer is infiltrated into the inside of the fiber, and the bond strength between the fibers is maintained while maintaining the inter-fiber gap. Provide increased configuration.

  Electrolytic paper is made of round net single paper or round net multiple paper, and as a paper strength enhancer, guar gum, locust bean gum, tragacanth gum, corn starch, potato starch, wheat starch, tapioca starch, dialdehyde starch, cationic starch, methylcellulose , Carboxymethylcellulose, polyacrylamide resin, polyethyleneimine resin, or urea resin is used. The paper strength enhancer is impregnated and applied to 0.05% by weight to 5.0% by weight of the electrolytic paper, and the fiber constituting the electrolytic paper is selected from Manila hemp pulp, sisal hemp pulp, and esparto pulp Or more than one.

  According to the present invention by the above means, by impregnating and applying the paper strength enhancer purified solution to the electrolytic paper, the paper strength enhancer purified solution is allowed to permeate the inside of the fiber, and the interfiber gap is maintained. Since the bond strength between fibers can be increased and the strength of single fibers can be increased, raw materials that have not been beaten or slightly beaten natural plant fibers, or CSF 500 ml to 720 ml that has a lower beating degree than before. Even if a raw material with a large CSF value is used, the paper strength enhancer is effectively fixed at the contact point between the fibers in the paper layer, the bond strength between the fibers is increased, and the paper strength enhancer is purified. Since the solution penetrates to the inside of the fiber, the strength of the single fiber itself can be greatly increased. Therefore, the electrolytic paper increases the fiber bond strength while maintaining the inter-fiber gap, so that the tensile strength can be remarkably improved without adversely affecting the ESR, and as a result, there is no paper break when the capacitor element is manufactured. it can. That is, according to the electrolytic paper according to the present invention, even if the bond strength of the fibers is increased, there is no shielding of the inter-fiber gaps due to the formation of a thin film by the microfibrils or heat-bonded fibers in the beating raw material as in the prior art. Therefore, electrolytic capacitors manufactured using electrolytic paper impregnated and coated with a refined solution of paper strength enhancer can achieve low ESR due to its thin and low density, and at the same time improve tensile strength by increasing fiber bond strength As a result, the short-circuit defect rate can be significantly reduced, and the productivity can be improved. Further, since the impurities of the paper strength enhancer are refined and reduced, the aluminum foil is not corroded or altered.

  The best embodiment of the electrolytic capacitor according to the present invention will be described below. In the present invention, natural vegetable fibers subjected to unbeaten or slight beating are used as raw materials to make paper with a circular paper machine, and in a dry paper state after paper making, impregnated and applied with a purified solution of a paper strength enhancer from which impurities have been removed. It has a special feature. Then, one or more natural plant fibers selected from Manila hemp pulp, sisal hemp pulp, and esparto pulp are used.

  Paper strength enhancers to be applied to electrolytic paper include vegetable gums such as guar gum, locust bean gum, tragacanth gum, starches such as corn starch, potato starch, wheat starch, tapioca starch, dialdehyde starch, cationic starch, methylcellulose, carboxy Semi-synthetic polymers such as methylcellulose, synthetic polymers such as polyacrylamide resin, polyethyleneimine resin, urea resin are used. Among them, dialdehyde starch, polyacrylamide resin, and polyethyleneimine resin are particularly preferable in view of availability, economy, strength enhancement effect, workability, and the like.

  In the present invention, a purified solution of the paper strength enhancer is used. In the present invention, the purified solution is a diluted aqueous solution in which impurities are removed to a level that does not corrode or alter the aluminum foil, and when the impurities in the electrolytic paper are evaluated by chemical conversion, it is 300 V for general use. It can be used in the range of ˜650 V, and the reliability is increased by setting the range of 500 V to 650 V as the corresponding one for high temperature and long life. The paper strength enhancer itself is not limited to the above-described one as long as it is purified as an aqueous solution, and an appropriate one can be used. Further, the paper strength enhancer may be a purified solution that meets the above conditions, and the purification treatment method may be any method such as an electrodialysis method, an ultrafiltration method, a reverse osmosis method, in addition to an ion exchange resin. There may be.

  The paper strength enhancer is impregnated and applied in an amount of 0.05% to 5.0% by weight, preferably 0.1% to 3.0% by weight, based on the electrolytic paper. In this range, it was possible to obtain a novel electrolytic paper having a target low density and a significantly improved tensile strength and in which inter-fiber voids are not shielded.

  By this refined solution of the paper strength enhancing agent applied by impregnation, the paper strength enhancing agent is effectively fixed at the contact point between the fibers in the paper layer, the bond strength between the fibers is increased, and the fibers penetrate into the inside of the fibers. Therefore, the strength of the single fiber itself can be increased. Accordingly, the electrolytic paper increases the fiber bond strength while maintaining the interfiber gap. In addition, it is not excessively beaten as in the prior art to generate microfibrils, and there is no shielding of fiber gaps due to film formation of heat-fusible fibers or the like, and it can be thin with low density and high tensile strength.

  The coated paper to be impregnated and coated with the refined solution of the paper strength enhancer had a circular net paper machine (single net single paper) having one circular net bat part, or two or more circular net bat parts. Electrolytic paper in a dry paper state produced by an appropriate paper machine such as a circular net multilayer combination machine (circular multi-layer paper) is used.

  After the paper making, the dried electrolyzed paper is impregnated with a purified solution of a paper strength enhancer diluted according to the target strength. As a coating method, it is immersed in a coating method such as a direct roll coater, dip coater, spray coater, kiss roll coater, etc., and after adjusting the liquid removal and thickness with a press roll, it is dried by hot air drying, cylinder drying method, etc. Thus, electrolytic paper having a predetermined thickness and density is manufactured. This method may be secondary processing, but if it is an on-line method in which these facilities are installed after paper making, mass production can be performed without impeding productivity. According to this method, for example, an anion, a nonion, a cation, and the like, which do not require a fixing agent having a large amount of impurities such as a sulfuric acid band and polyaluminum chloride, as in an internal addition of an anionic strength enhancer to a conventional raw material suspension, Any paper strength enhancer can be used. In addition, as the electrolytic paper for impregnating and applying the purified solution of the paper strength enhancer, the dry paper-type electrolytic paper after papermaking is efficient and suitable. Although it is possible to apply it by spraying onto electrolytic paper in the wet paper state, the moisture content of the wet paper is high, so that the paper strength enhancer flows out by suction dehydration or press dehydration, which is not efficient. Since it contaminates the dryer cylinder and the conventional paper making of electrolytic paper, it is appropriate to impregnate and apply to electrolytic paper in a dry paper state.

  In addition, depending on the impregnation application, press load, drying method and these conditions, it is possible to adjust the thickness and density of the electrolyzed paper after paper making. It becomes possible to produce the ultra-low density electrolytic paper that had been used. In addition, the tensile strength increases to prevent paper breaks in the element winding process, and the fine fibers in the electrolytic paper are firmly fixed to increase the surface strength of the electrolytic paper. Generation of paper dust due to fiber dropping in the process can also be prevented, and the frequency of line cleaning can be reduced to facilitate the work of the process.

The density of the obtained electrolytic paper is 0.20 to 0.70 g / cm ³ and thickness is 20 to 70 μm, preferably 0.20 to 0.35 g / cm ³ and thickness is 40 to 60 μm. . In addition, when the impurities of the electrolytic paper are evaluated by chemical conversion properties, it is appropriate to use 300 to 650 V, preferably 500 to 650 V, and a tensile strength of 1.1 kg / 15 mm or more. In order to maintain the high reliability of the electrolytic paper, it is one of the features of the present invention that impurities in the electrolytic paper are evaluated by chemical conversion and satisfy the evaluation standard of chemical conversion.

  The electrolytic paper obtained in this manner is wound between an anode aluminum foil and a cathode aluminum foil, and then impregnated with a liquid electrolyte and sealed to produce an electrolytic capacitor.

  Various specific examples, comparative examples, and conventional examples according to the present invention are shown below. The electrolytic capacitor is a case in which electrolytic paper is interposed between the tabbed anode foil and the cathode foil so that both electrodes do not come in contact with each other and wound to form an electrolytic capacitor element, and then impregnated with a predetermined electrolytic solution. And was aged to obtain a 50 WV, 220 μF aluminum dry capacitor.

Using 100% by weight of Manila hemp pulp, beaten to 720 ml of CSF, and after making circular double paper with a thickness of 49.9 μm, a density of 0.275 g / cm ³ , and a tensile strength of 0.6 kg / 15 mm, using a direct roll coater A diluted solution of dialdehyde starch purified with an ion exchange resin is dipped, adjusted to remove liquid so that the dialdehyde starch is 2.8% by weight with respect to the paper with a press roll, and then dried with hot air to have a thickness of 59.8 μm and a density of 0.8. An electrolytic paper having 236 g / cm ³ and a tensile strength of 1.2 kg / 15 mm was obtained. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

A mixed raw material of 70% by weight of Manila hemp pulp and 30% by weight of sisal hemp pulp is beaten into 710 ml of CSF, and papermaking is performed with circular double paper having a thickness of 47.6 μm, a density of 0.286 g / cm ³ , and a tensile strength of 0.6 kg / 15 mm. Then, dilute the diluted solution of polyacrylamide resin purified with ion exchange resin with a direct roll coater, adjust the liquid removal to 1.2% by weight with respect to the paper with a press roll, and then dry with a cylinder dryer and dry. An electrolytic paper having a thickness of 50.0 μm, a density of 0.275 g / cm ³ , and a tensile strength of 1.4 kg / 15 mm was obtained. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

Using a mixed raw material of 60% by weight of esparto pulp and 40% by weight of Manila hemp, beating into 650 ml of CSF, a double mesh paper having a thickness of 39.6 μm, a density of 0.348 g / cm ³ , and a tensile strength of 0.8 kg / 15 mm After making the paper, immerse the diluted solution of polyacrylamide resin purified with ion exchange resin with a direct roll coater, adjust the liquid removal with a press roll so that the polyacrylamide is 0.8% by weight with respect to the paper, and then dry with a cylinder dryer An electrolytic paper having a thickness of 40.2 μm, a density of 0.346 g / cm ³ , and a tensile strength of 1.8 kg / 15 mm was obtained. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

A mixed raw material of 50% by weight of esparto pulp and 50% by weight of Manila hemp is beaten into 600 ml of CSF, and a circular double paper having a thickness of 41.9 μm, a density of 0.482 g / cm ³ and a tensile strength of 3.0 kg / 15 mm is obtained. After making the paper, immerse the diluted solution of polyacrylamide resin purified with ion exchange resin with a direct roll coater, adjust the liquid removal to 0.5% by weight with respect to the paper with a press roll, and then dry with a cylinder dryer An electrolytic paper having a thickness of 40.0 μm, a density of 0.506 g / cm ³ , and a tensile strength of 4.4 kg / 15 mm was obtained. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

Using a mixed raw material of 40% by weight of esparto pulp and 60% by weight of Manila hemp, beating into 500 ml of CSF, and making a single piece of circular mesh paper having a thickness of 30.6 μm, a density of 0.592 g / cm ³ , and a tensile strength of 3.3 kg / 15 mm After that, immerse the diluted solution of polyacrylamide resin purified with ion exchange resin with a direct roll coater, adjust the liquid removal to 0.3% by weight with respect to the paper with a press roll, and dry with a cylinder dryer. An electrolytic paper having a thickness of 30.3 μm, a density of 0.603 g / cm ³ , and a tensile strength of 4.7 kg / 15 mm was obtained. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Comparative Example 1] → Corresponding to Example 1 Using 100% by weight of a raw material obtained by beating Manila hemp pulp into 720 ml of CSF, a circle having a thickness of 50.2 μm, a density of 0.277 g / cm ³ , and a tensile strength of 0.6 kg / 15 mm After making the mesh double paper, immerse the diluted solution of commercially available epoxy resin (polyamide polyamine epichlorohydrin resin) with a direct roll coater, and remove with a press roll so that the epoxy resin is 2.5% by weight with respect to the paper. After the adjustment, electrolytic paper having a thickness of 59.0 μm, a density of 0.237 g / cm ³ , and a tensile strength of 1.1 kg / 15 mm was obtained by hot air drying. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 1] → Corresponding to Example 1 A cylinder dryer of a paper machine using a mixed raw material of 30% by weight of sisal pulp beaten to CSF 450ml, 50% by weight of chopped glass fiber and 20% by weight of vinylon binder fiber The vinylon binder fiber was heat-sealed to make a paper having a thickness of 60.5 μm, a density of 0.235, and a tensile strength of 0.8 kg / 15 mm. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 2] → Corresponding to Example 1 Using a mixed raw material of 70% by weight raw material of Manila hemp pulp in 350 ml of CSF and 30% by weight of polypropylene fibers, a thickness of 62.3 μm, a density of 0.230 g / cm ³ , After making a paper having a tensile strength of 0.6 kg / 15 mm, polypropylene fibers were heat-sealed to produce a paper having a thickness of 60.1 μm, a density of 0.238 g / cm ³ , and a tensile strength of 1.0 kg / 15 mm. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 3] → Corresponding to Example 2 A mixed raw material of 70% by weight of Manila hemp pulp and 30% by weight of sisal hemp pulp was beaten into 680 ml of CSF, thickness 50.2 μm, density 0.278 g / cm ³ , and tensile strength 0. A 7 kg / 15 mm circular mesh double paper was made. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 4] → Corresponding to Example 3 Using a mixed raw material of 60% by weight of esparto pulp and 40% by weight of Manila hemp, beaten to 610 ml of CSF, thickness 39.9 μm, density 0.347 g / cm ³ , tensile strength 1 A 0.0kg / 15mm circular double paper was made. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 5] → Corresponding to Example 4 Using a mixed raw material of 50% by weight of esparto pulp and 50% by weight of Manila hemp, beating into 560 ml of CSF, thickness 40.0 μm, density 0.503 g / cm ³ , tensile strength 3 A 2 kg / 15 mm circular mesh double paper was made. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

[Conventional Example 6] → Corresponding to Example 5 Using a mixed raw material of 40% by weight of esparto pulp and 60% by weight of Manila hemp, beating into 440 ml of CSF, thickness 30.4 μm, density 0.596 g / cm ³ , tensile strength 3 A circular mesh double paper of 8 kg / 15 mm was made. Next, an electrolytic capacitor of 50 WV and 220 μF was manufactured using this electrolytic paper.

Regarding the electrolytic papers and electrolytic capacitors obtained in Examples 1 to 5, Comparative Example 1 and Conventional Examples 1 to 6, the thickness (μm), density (g / cm ³ ), tensile strength (kg / 15 mm), The air density (seconds / 100 cc), chemical conversion (V), paper dust generation amount (mg / 1000 m), short-circuit defect rate (%), and ESR (Ω / 1 kHz) were measured. In addition, the measuring method and its apparatus are as follows.

(1) Thickness, density, and tensile strength of electrolytic paper The electrolytic paper was measured by the method defined in JIS C2301 (electrolytic capacitor paper).

(2) Air density The air density was measured with a B-type tester (Gurley densometer) in accordance with the section "12.1 Air density" defined in JIS C2111 (electrical insulating paper test method). However, an adapter having a hole portion of 6 mmφ was used. Moreover, about the electrolysis paper with a gas density of 1 second or less, it measured by superposing | stacking 5 sheets, and converted into 1 sheet.

(3) Chemical conversion 50 g ± 1 g of electrolytic paper was boiled in 1000 ml of ion-exchanged water for 1 hour, the extract was concentrated to 100 ml, cooled, and then added to a clean sample solution containing 0.35 g of adipic acid. Using 99% plain aluminum foil as both electrodes, the voltage after 10 minutes was measured at a constant current of 60 mA to obtain chemical conversion. At this time, as a blank test, it was confirmed that 1000 ml of ion-exchanged water was concentrated to 100 ml, 0.35 g of adipic acid was dissolved, and the value after 10 minutes measured by the above operation was within the range of 600V to 650V. It was.

(4) Amount of paper dust generated Two cutter blades are fixed at an interval of 5 cm in the center of a tester provided with unwinding and winding. Electrolytic paper cut into a record roll with a width of 18 mm was set on the unwinding side, pulled out with a tension of 0.5 kg, moved to the 1000 m winding side at a speed of 10 m / min while rubbing the cutter blade, and dropped during this time. The amount of paper dust was measured. The average value of 4 times was displayed.

(5) Short-circuit defect rate After the electrolytic paper was wound up with the anode foil and the cathode foil to form an electrolytic capacitor element, continuity due to a short between both electrodes was confirmed with a tester without impregnating the electrolytic solution. The short defect rate was inspected for about 1000 elements, and the ratio of the short elements to the total number of elements was defined as the short defect rate.

(6) ESR (Equivalent Series Resistance)
The ESR of the electrolytic capacitor was measured by an LCR meter at a frequency of 20 ° C. and 1000 HZ.

  The evaluation results of the electrolytic papers and electrolytic capacitors of Examples 1 to 5 obtained as described above are shown in Table 1, and the evaluation results of the electrolytic paper and electrolytic capacitors of Comparative Example 1 and Conventional Examples 1 to 6 are shown in Table 2.

As shown in the results of Table 1, in the present invention using the electrolytic paper formed by impregnating and applying a purified solution of a paper strength enhancer, the short defect rate is remarkably improved without deteriorating the chemical conversion and ESR. . For example, in Example 1, dialdehyde starch was formed on a circular double paper having a thickness of 49.9 μm, a density of 0.275 g / cm ³ , and a tensile strength of 0.6 kg / 15 mm. Impregnated and applied with the purified diluted solution, dried with hot air in the swollen state of the wet paper and increased in thickness to further reduce the thickness 59.8 μm, density 0.236 g / cm ³ , tensile strength 1.2 kg / 15 mm Comparative Example 1 was produced by impregnating and applying a commercially available epoxy resin that was not refined to a circular double paper made under the same conditions. Electrolytic paper is used. Both the short-circuit defect rate and the ESR are substantially the same values as in Example 1, but the chemical conversion is extremely low at 30 V compared to 625 V in Example 1. This is due to the chlorine content contained in the epoxy resin composition, indicating that it is not at a practical level as electrolytic paper. Therefore, in order to solve the problems of the present invention, it is necessary that the paper strength enhancer to be used is purified.

  Conventional example 1 uses a mixed raw material of CSF 450 ml of sisal pulp 30% by weight, chopped glass fiber 50% by weight and vinylon binder fiber 20% by weight. The binder fiber is heat-sealed on a paper machine cylinder dryer. The paper was made to have substantially the same thickness and the same density as in Example 1. In spite of substantially the same thickness and the same density, the ESR is improved to 0.0919 Ω / 1 kHz in the first example compared to 0.1175 Ω / 1 kHz in the conventional example 1. In Conventional Example 1, since the binder fiber is melted to form a film (film), the fiber gap is shielded and the ionic conduction of the electrolytic solution is obstructed, so the ESR is worse than that of Example 1 even at the same density. It is. On the other hand, in Example 1, the ESR can be improved because the inter-fiber voids are maintained even when impregnated with a refined solution of a paper strength enhancer. Moreover, although the conventional example 1 advanced the degree of beating with CSF450ml, although Example 1 is CSF720ml, the tensile strength is 0.8kg / 15mm in the prior art example 1 and 1 in the example 1. .2kg / 15mm and soaring. As a result, the short-circuit defect rate is 17.5% in Conventional Example 1 and 7.2% in Example 1. From this, the low density electrolytic paper impregnated with the refined paper strength enhancer significantly increases the tensile strength of the paper and improves the resistance to foil burrs. It turns out that it is also good.

  Conventional example 2 was manufactured by melting and melting polypropylene by heat-treating a mixed paper of 70% by weight of Manila hemp pulp and 30% by weight of polypropylene fiber beaten to CSF 350ml. Therefore, Manila hemp pulp is beaten excessively, resulting in poor formation of Manila hemp pulp paper balls, etc., and the short defect rate is high at 15.2%. As a result, the ESR deteriorates to 0.1305Ω / 1 kHz.

Example 2 is an electrolytic paper impregnated with a dilute solution of purified polyacrylamide on a circular double-ply paper made from a mixed raw material of 70% by weight of Manila hemp pulp and 30% by weight of sisal pulp as CSF 710 ml, and having a thickness of 50.0 μm. The density is 0.275 g / cm ³ , the tensile strength is 1.4 kg / 15 mm, the short-circuit defect rate is 8.4%, and the ESR is 0.1059 Ω / 1 kHz. On the other hand, Conventional Example 3 is an electrolytic paper having substantially the same thickness and the same density produced by making the same mixed raw material as in Example 2 as CSF 680 ml. Conventional Example 3 achieves a low ESR of 0.1092 Ω / 1 kHz by making the density as low as 0.278 g / cm ³ , but the tensile strength is 0.7 kg / 15 mm, and the short-circuit defect rate is 30.4. % Has risen significantly. On the other hand, in Example 2, the tensile strength was increased to 1.4 kg / 15 mm by impregnating and applying the purified solution of the paper strength enhancer, and the short-circuit defect rate was significantly reduced to 8.4%. Since the air gap is maintained, the ESR shows a good numerical value of 0.1059Ω / 1 kHz. Also, in the capacitor element winding process, in the conventional example 3, the electrolytic paper breakage frequently occurs and the productivity is remarkably hindered, but in the second embodiment, the electrolytic paper breakage does not occur.

Example 4 is an electrolytic paper impregnated with a dilute solution of purified polyacrylamide on a circular double-ply paper made from a mixed raw material of 50% by weight of esparto pulp and 50% by weight of Manila hemp pulp as CSF 600 ml. The density is 0.506 g / cm ³ , the tensile strength is 4.4 kg / 15 mm, the amount of paper dust generated is 16 mg / 1000 m, the short-circuit defect rate is 0.6%, and the ESR is 0.1510 Ω / 1 kHz. On the other hand, Conventional Example 5 is currently the most commonly used electrolytic paper for low ESR, which uses electrolytic paper that is beaten to the same mixed raw material up to 560 ml and made into paper with approximately the same thickness and density. The tensile strength was 3.2 kg / 15 mm, the amount of paper dust was 68 mg / 1000 m, the short-circuit defect rate was 2.5%, and the ESR was 0.1541 Ω / 1 kHz. As can be seen from the data, Example 4 in which the tensile strength was greatly improved by impregnating and applying a refined solution of a paper strength enhancer without excessively refining significantly reduced the short-circuit defect rate without deteriorating ESR. ing. In addition, in the element winding process, the generation of paper dust is greatly reduced, and paper jamming due to falling paper powder, poor centering, and electrolyte contamination can be reduced.

  As described in detail above, the electrolytic capacitor according to the present invention is a paper strength enhancer such as vegetable gum, starch, semi-synthetic polymer, synthetic polymer, etc., in which impurities are reduced to a level that does not corrode or discolor aluminum foil. It is characterized by impregnating and applying the purified solution to the electrolytic paper, and the following effects can be obtained. That is, the increase in tensile strength by impregnating and applying a refined solution of a paper strength enhancer is different from electrolytic paper in which natural plant fibers are excessively beaten or heat-bonded fibers are used to improve tensile strength, Since there is no film-forming action, the electrolytic paper increases the fiber bond strength while maintaining the inter-fiber voids, and can significantly reduce the short-circuit defect rate by greatly increasing the tensile strength without deteriorating the ESR. In addition, even if raw materials with a slight beating of natural plant fibers or raw materials with a large CSF value with a shallower beating degree than before are used, the paper strength is increased at the contact point between the fibers in the paper layer. Since the agent is effectively fixed, the bond strength between fibers is increased, and the fibers penetrate into the fibers, so that the strength of the single fiber itself can be increased. Therefore, it is possible to manufacture electrolytic papers in the ultra-low density region, which was conventionally difficult to use in practical use. It is possible to reduce paper dust troubles by greatly reducing the amount of electricity and to significantly improve the productivity in the electrolytic capacitor manufacturing process. Furthermore, since the natural plant fiber having a large CSF value can be used as a raw material, the beating power can be reduced.

Claims (8)

In an electrolytic capacitor in which electrolytic paper is interposed between the anode foil and the cathode foil,
The electrolytic paper is made with a circular net paper machine using natural beet fiber that has been unbeaten or slightly beaten as a raw material, and impregnated with a purified solution of a paper strength enhancer from which impurities have been removed in the dry paper state after paper making. When applied, the density is 0.20 to 0.70 g / cm ³ , the tensile strength is 1.1 kg / 15 mm or more, the thickness is 20 to 70 μm, and 500 to 650 V when impurities in the electrolytic paper are evaluated by chemical conversion, An electrolytic capacitor having an ESR of 0.2Ω / 1 kHz or less.   The electrolytic capacitor according to claim 1, wherein the degree of beating of the natural plant fiber is 500 ml to 720 ml in terms of CSF.   3. The electrolytic capacitor according to claim 1 or 2, wherein the purified solution of the paper strength enhancing agent from which impurities are removed is impregnated and applied so as to be fixed at a contact point between fibers in the paper layer.   Impregnating and applying the purified solution of the paper strength enhancer from which impurities have been removed allows the purified solution of the paper strength enhancer to penetrate into the interior of the fiber, increasing the bond strength between the fibers while maintaining the inter-fiber voids. The electrolytic capacitor according to claim 1, 2 or 3.   5. The electrolytic capacitor according to claim 1, 2, 3 or 4, wherein the electrolytic paper is a circular net single paper or a circular net multiple paper.   The paper strength enhancer is selected from guar gum, locust bean gum, tragacanth gum, corn starch, potato starch, wheat starch, tapioca starch, dialdehyde starch, cationic starch, methylcellulose, carboxymethylcellulose, polyacrylamide resin, polyethyleneimine resin, urea resin The electrolytic capacitor according to claim 1, 2, 3, 4 or 5, wherein one or more of them are used.   The electrolytic capacitor according to claim 1, 2, 3, 4, 5 or 6, wherein a paper strength enhancer is impregnated with 0.05 to 5.0% by weight of electrolytic paper.   The electrolytic capacitor according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the fiber constituting the electrolytic paper is one or more selected from Manila hemp pulp, sisal hemp pulp, and esparto pulp.