JP2004228600A - Electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor which has improved short circuit failure rate without adversely affecting the impedance characteristics and improved productivity by using a novel electrolytic paper having a low density and highly improved tensile strength, of which space between fibers is never shielded. <P>SOLUTION: In the electrolytic capacitor which is constituted by interposing electrolytic paper between an anode foil and a cathode foil, the electrolyte paper is made from natural plant fibers having CSF value of 500 ml or more, which are used as a raw material, and then the coupling strength of the fibers is increased by impregnating and applying a paper strengthening agent into the electrolytic paper so that the refined solution of the paper strengthening agent permeates into the fibers with the space between the fibers being kept. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an electrolytic capacitor having an electrolytic paper interposed between an anode foil and a cathode foil, and in particular, has a low density and a significantly improved tensile strength, and furthermore, a gap between fibers is shielded. By using a new electrolytic paper which does not cause any problem, the short-circuit defect rate is improved without adversely affecting the impedance characteristics, and the productivity is improved.

  Generally, an electrolytic capacitor, especially an aluminum electrolytic capacitor, is formed by winding an electrolytic paper between an anode aluminum foil and a cathode aluminum foil to form a capacitor element, and immersing the capacitor element in a liquid electrolyte. It is impregnated with electrolyte and sealed. As an electrolyte, ethylene glycol (EG), dimethylformamide (DMF), γ-butyrolactone (GBL) or the like is usually used as a solvent, and an organic acid salt such as boric acid, ammonium adipate, or ammonium hydrogen maleate is dissolved in these solvents. It is manufactured by permeating the capacitor element from both ends.

  Since these conventional aluminum electrolytic capacitors impregnate the electrolytic solution into the electrolytic paper, the impedance characteristics of the capacitors, particularly the equivalent series resistance (hereinafter abbreviated as ESR), tend to be high. In addition to the means of lowering the resistance of the electrolyte, making the electrolytic paper thinner or lowering its density, other means are used to change the raw material of the electrolytic paper from ordinary wood kraft pulp to softwood pulp, manila hemp pulp, esparto pulp, etc. Have been. However, lowering the resistance value of the electrolytic solution causes corrosiveness to the aluminum foil. On the other hand, thinning or lowering the density of the electrolytic paper inevitably lowers the tensile strength and increases the short-circuit failure rate. However, even if the short circuit does not occur, there is a problem that the short-circuit defect rate after the product is put on the market and put on the market increases.

  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 pulp as a raw material is used. It is known that, when the value of (Freeness) is reduced, the fibers of the pulp become fibrillated and become finer, the resulting electrolytic paper becomes denser, the tensile strength increases, and the short-circuit failure rate is improved. In addition, it has been found that the influence of these items on the ESR deteriorates in a linear manner when the electrolytic paper is thickened, and deteriorates in a quadratic manner when the density is increased. That is, in order to improve the ESR, it is necessary to make the electrolytic paper thinner and lower 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 converted from ordinary wood kraft pulp to coniferous wood pulp, manila hemp pulp, fiber diameter of esparto pulp or the like. Attempts have been made to produce thin, low-density, dense electrolytic paper by changing to a smaller pulp. Currently, the most widely used blended paper for electrolytic paper is a blended paper of Manila hemp pulp and esparto pulp.By mixing highly rigid esparto pulp with thin fiber diameter into Manila hemp pulp, the appearance of Manila hemp is improved. Electrolytic paper having high density can be obtained even if roughness is eliminated and density is low (see Patent Document 1).

  Further, by using sisal pulp, in which the density of the paper produced is hardly increased even if the CSF is reduced by beating the raw material as a raw material of the electrolytic paper, an electrolytic paper having a low density is obtained from a raw material having a small CSF. Is provided (see 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 the burrs, and it is also important to improve the tensile strength as well as the thickness, density, denseness and pinholes. Therefore, as described above, in addition to reducing the value of CSF, heat-fused fibers having a low melting point such as vinylon binder fibers and polyethylene fibers are mixed with the raw materials and melted at the temperature in the drying step, and the adhesive strength between the fibers is reduced. Means for increasing the tensile strength, and means for increasing the tensile strength by subjecting paper mixed with thermoplastic fibers such as polypropylene fibers and nylon fibers to heat treatment by secondary processing and fusing them. In these means, in addition to the above-mentioned natural plant fibers, synthetic fibers such as viscose rayon fibers, polypropylene fibers, polyimide fibers, and aramid fibers, as well as inorganic fibers such as glass fibers and alumina silica fibers are blended to obtain a low density and With high porosity, it is possible to obtain paper having a practical level of tensile strength.

In addition, starch, vegetable gum, semi-synthetic polymer, synthetic polymer, etc. are added to the raw material suspension during the manufacturing process to increase the general tensile strength of paper, and it is fixed to the fiber surface layer and the bonding strength between fibers is increased. There are known means for increasing.
JP-B-61-45379 JP-A-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 the tensile strength is extremely increased by mixing the esparto pulp. Will decrease. For this purpose, it is necessary to reduce the CSF value of the manila hemp pulp, generate countless fibrils, increase the hydrogen bonds acting between the fibers, increase the strength of the electrolytic paper, and maintain the tensile strength. However, recently, the fibrils of Manila hemp pulp to increase the tensile strength fill the fiber gap, so even if low density paper can be made in the presence of rigid esparto pulp, it will adversely affect ESR. Has been found.

  On the other hand, according to Patent Literature 2 using sisal pulp as a raw material, since sisal pulp has a fiber diameter substantially the same as that of Manila hemp pulp, and has a higher rigidity than Manila hemp pulp, there is a problem that it is difficult to make thin paper. In addition, it has been found that, because of the appearance roughness, the tensile strength is low, and the rate of paper breakage and short-circuit failure in the element winding step increases.

  Means for increasing the bonding between fibers by blending heat-fusible fibers capable of increasing the tensile strength without reducing the numerical value of CSF and melting them in a drying step, or blending thermoplastic fibers to form a composite fiber. In the means for increasing the tensile strength by fusing in the next processing heat treatment, the binder fiber and the thermoplastic fiber are melted to form a film (film), which blocks the fiber gap and inhibits the ionic conduction of the electrolytic solution. It has been found that high tensile strength of paper results in poor ESR.

  Further, starch, vegetable gum, semi-synthetic polymer, synthetic polymer, etc. are added to the raw material suspension during the manufacturing process, which is a general means of increasing the tensile strength of paper, and the mixture is fixed to the fiber surface layer to allow the fibers to interact with each other. According to the means for increasing the bonding strength, it is effective to some extent for high-density raw materials capable of reducing the numerical value of CSF, generating microfibrils and increasing the fiber surface area. However, in recent years, it is not necessarily effective especially for reducing the ESR required for electrolytic paper. That is, it is important to manufacture the electrolytic paper at a lower density in order to reduce the ESR. Therefore, it is necessary to manufacture the raw material on the premise of an unbeaten raw material or a raw material that has been slightly beaten. This is because if the numerical value of CSF is reduced by subjecting the raw fiber to beating treatment, the density inevitably increases. Therefore, in the electrolytic paper for the purpose of reducing the ESR, the fiber surface area does not increase because the unbeaten raw material or the raw material which is 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 large increase in tensile strength cannot be expected. Insufficient tensile strength.

In addition, as long as the above-mentioned various natural plant fibers are used at 100%, the lower limit density of the electrolytic paper is 0.27 g / cm ³ , and if the density is lower than this, paper breakage occurs at the winding stage of electrolytic paper production. However, even if it can be manufactured, it is not suitable for practical use due to the frequent occurrence of paper breakage in the element winding process of the capacitor.

  On the other hand, in the manufacturing process of capacitors, there is a problem of running out of electrolytic paper at the time of winding on a capacitor element. Therefore, the improvement is required.

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

  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. At the same time, the electrolytic paper after the papermaking is impregnated with a purified solution of a paper strength enhancer, and the electrolytic paper is made from a natural plant fiber having a CSF value of 500 ml or more as a raw material. The paper is made from natural vegetable fiber with a CSF value of 500 ml or more as a raw material, and the purified paper is made by impregnating and coating the purified solution of the agent at the contact points between the fibers in the paper layer. By impregnating and applying the purified solution of the paper strength enhancer to the inside of the fibers, the purified solution of the paper strength enhancer is permeated into the fibers to increase the bonding strength between the fibers while maintaining the space between the fibers. provide

The paper-strength enhancer is one or more selected from starch, vegetable gum, semi-synthetic polymer or synthetic polymer. To 5.0% by weight or 0.1% to 3.0% by weight impregnated and applied; 300 to 650V or 500 to 650V when impurities in the electrolytic paper are evaluated by chemical conversion; A configuration in which the natural plant fiber is one or more selected from manila hemp pulp, sisal pulp, and esparto pulp, the density of the electrolytic paper is 0.20 to 0.70 g / cm ³ , and the thickness is 20. Provided is a configuration in which the thickness is from 40 to 70 μm or a density is from 0.20 to 0.35 g / cm ³ and the thickness is from 40 to 60 μm, and the tensile strength of the electrolytic paper is 1.1 kg / 15 mm or more.

  According to the present invention by the above-mentioned means, by impregnating and coating an electrolytic paper with a purified solution of a paper strength enhancer, a raw material having a degree of beating the natural plant fiber slightly or a CSF having a smaller degree of beating than the conventional ones Even when a raw material having a large CSF value of 500 ml or more is used, the paper strength enhancer is effectively fixed to the contact points between the fibers in the paper layer, and the bonding strength between the fibers increases, and the fiber strength increases. Since it penetrates into the inside, the strength of the single fiber itself can also be increased. Therefore, in the electrolytic paper, since the bonding strength of the fibers is increased while maintaining the inter-fiber space, the tensile strength can be remarkably improved without adversely affecting the ESR. As a result, it is possible to eliminate the breakage during the production of the capacitor element. it can. That is, according to the electrolytic paper of the present invention, even if the bonding strength of the fibers is increased, there is no shielding of the inter-fiber gap due to the formation of a thin film using microfibrils, heat-fused fibers and the like in the beating raw material as in the related art. Therefore, electrolytic capacitors manufactured using electrolytic paper impregnated with a purified solution of a paper strength enhancer can achieve low ESR due to thinness 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 further improved. Further, since the impurities of the paper strength agent are purified and reduced, the aluminum foil is not corroded or deteriorated.

  Hereinafter, a preferred embodiment of an electrolytic capacitor according to the present invention will be described. The present invention is characterized in that a purified solution of a paper strength agent is impregnated and applied to electrolytic paper after papermaking. Examples of the paper strength enhancer applied to the 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, methyl cellulose, carboxylate. Semi-synthetic polymers such as methylcellulose, and synthetic polymers such as polyacrylamide resin, polyethyleneimine resin, and urea resin are used. Among them, dialdehyde starch, polyacrylamide resin, and polyethyleneimine resin are particularly preferable in view of availability, economy, strength enhancing effect, workability, and the like.

  In the present invention, a purified solution of the paper strength agent is used. In the present invention, the purified solution is a dilute aqueous solution in which impurities are removed by an ion exchange resin or the like to a level that does not corrode or alter the aluminum foil. It can be used in the range of 650 V to 650 V. Further, when the temperature is in the range of 500 V to 650 V for high temperature and long life use, the reliability is increased. 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 agent may be a purified solution that meets the above conditions, and the method of the purification treatment may be any method such as an electrodialysis method, an ultrafiltration method, and a reverse osmosis method, in addition to the ion exchange resin. There may be.

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

  By the impregnated and purified solution of the paper strength enhancer, the paper strength enhancer is effectively fixed at the points of contact between the fibers in the paper layer, and the bond strength between the fibers is increased, and the fibers penetrate into the interior of the fibers. Therefore, the strength of the single fiber itself can be increased. Therefore, in the electrolytic paper, the fiber bonding strength is increased while maintaining the inter-fiber voids. Moreover, unlike the conventional method, the fibers are not beaten excessively to generate microfibrils or the fiber gap is not blocked by the formation of a film made of a heat-fused fiber or the like.

  The paper to be coated impregnated with the purified solution of the paper strength enhancer was a circular paper machine having a single circular vat (circular single-layer paper), or had two or more circular vats. Electrolytic paper in a dry paper state produced by a suitable paper machine such as a circular mesh multilayer combination machine (circular mesh multiplex paper) is used.

  After the paper making, the electrolytic paper in a dry paper state is impregnated with a purified solution of a paper strength enhancer diluted according to a 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 dewatering adjustment and thickness adjustment with a press roll, it is dried by hot air drying or cylinder dry method. Then, an electrolytic paper having a predetermined thickness and density is manufactured. This method may be secondary processing, but if it is an online method in which these facilities are installed after papermaking, mass production can be performed without impairing productivity. According to this method, for example, unlike the conventional internal addition of an anionic paper-strengthening agent to a raw material suspension, a fixing aid containing a large amount of impurities such as a sulfuric acid band or polyaluminum chloride is not required. Can be used. In addition, as the electrolytic paper to be impregnated with the purified solution of the paper strength agent, an electrolytic paper in a dry paper state after papermaking is suitable with high efficiency. Spray coating on electrolytic paper in the wet paper state is also possible, but due to the high moisture content of the wet paper, the paper strength enhancer flows out by suction dehydration or press dehydration, resulting in poor efficiency. In addition, it impairs the conventional paper making of electrolytic paper because it contaminates the dryer cylinder and the dryer cylinder. Therefore, it is appropriate to impregnate and apply the electrolytic paper in a dry paper state.

  Also, depending on the method of impregnation coating, press load, drying, and these conditions, it is possible to adjust the thickness and density of the electrolytic paper after papermaking. It becomes possible to manufacture the ultra-low density electrolytic paper that had been used. In addition, the increase in tensile strength prevents breakage in the element winding process and also firmly fixes the fine fibers in the electrolytic paper, increasing the surface strength of the electrolytic paper, cutting the electrolytic paper and winding the capacitor element. It is also possible to prevent the generation of paper dust due to the falling off of fibers in the process, and it is also possible to reduce the frequency of line cleaning and to facilitate the work in the process.

The density of the obtained electrolytic paper is suitably 0.20 to 0.70 g / cm ³ and a thickness of 20 to 70 μm, preferably 0.20 to 0.35 g / cm ³ and a thickness of 40 to 60 μm. . When the impurities in the electrolytic paper are evaluated by chemical conversion, the voltage is 300 to 650 V, preferably 500 to 650 V, and the tensile strength is suitably 1.1 kg / 15 mm or more. One of the features of the present invention is that impurities in the electrolytic paper are evaluated by chemical conversion in order to maintain high reliability of the electrolytic paper, and the evaluation criteria for the chemical conversion are satisfied.

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

  Hereinafter, specific examples, comparative examples, and conventional examples according to the present invention will be described. The electrolytic capacitor is interposed between the anode and cathode foils with tabs so that the electrodes do not come into contact with each other, wound up to form an electrolytic capacitor element, and then impregnated with a predetermined electrolytic solution. And subjected to aging to obtain a 50 WV, 220 μF aluminum dry capacitor.

Using 100% by weight of Manila hemp pulp, beaten to 720 ml of CSF to make a circular mesh 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, and then use a direct roll coater. A diluted solution of dialdehyde starch purified with an ion exchange resin is immersed in the solution, and the pressure of the dialdehyde starch is adjusted to 2.8% by weight of the paper with a press roll. An electrolytic paper having 236 g / cm ³ and a tensile strength of 1.2 kg / 15 mm was obtained. Then, a 50 WV, 220 μF electrolytic capacitor 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 was beaten into 710 ml of CSF, and papermaking was performed using a circular double-sheet 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, a dilute solution of polyacrylamide resin purified by ion exchange resin is immersed in a direct roll coater, dewatered by press roll so that the polyacrylamide becomes 1.2% by weight with respect to the paper, dried by a cylinder dryer, and dried. 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. Then, a 50 WV, 220 μF electrolytic capacitor 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, beaten to 650 ml of CSF to obtain a circular mesh double 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 paper, dilute solution of polyacrylamide resin purified by ion exchange resin is immersed in direct roll coater, adjusted to remove 0.8% by weight of polyacrylamide based on paper by press roll, and dried by 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. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

Using a mixed raw material of 50% by weight of esparto pulp and 50% by weight of manila hemp, beaten to 600 ml of CSF to obtain a circular mesh 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. After making paper, dilute solution of polyacrylamide resin purified by ion exchange resin is immersed in direct roll coater, adjusted to remove polyacrylamide to 0.5% by weight of paper by press roll, and dried by 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. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

Using a raw material mixture of 40% by weight of esparto pulp and 60% by weight of manila hemp, beaten to 500 ml of CSF, and made a single-mesh net 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, a dilute solution of polyacrylamide resin purified by ion exchange resin is immersed in a direct roll coater, and depressurization is adjusted to 0.3% by weight of polyacrylamide with respect to paper by a press roll, and then dried by a cylinder dryer. 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. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

[Comparative Example 1] → Corresponding to Example 1 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 was prepared by using 100% by weight of a raw material obtained by beating Manila hemp pulp into 720 ml of CSF. After making a double-sided paper, a dilute solution of a commercially available epoxy resin (polyamide polyamine epichlorohydrin resin) is immersed in a direct roll coater, and depressurized by a press roll so that the epoxy resin becomes 2.5% by weight of the paper. After the adjustment, hot-air drying was performed to obtain 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. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

[Conventional Example 1] → corresponding to Example 1 A cylinder dryer for a paper machine was prepared by using a mixed material of 30% by weight of raw material obtained by beating sisal pulp to 450 ml of CSF, 50% by weight of chopped glass fiber and 20% by weight of vinylon binder fiber. A vinylon binder fiber was heat-sealed on the above to produce paper having a thickness of 60.5 μm, a density of 0.235, and a tensile strength of 0.8 kg / 15 mm. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

[Conventional Example 2] → Corresponding to Example 1 Using a mixed material of 70% by weight of raw material obtained by beating Manila hemp pulp into 350 ml of CSF and 30% by weight of polypropylene fiber, a thickness of 62.3 μm, a density of 0.230 g / cm ³ , After paper having a tensile strength of 0.6 kg / 15 mm was formed, polypropylene fibers were thermally fused to produce 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. Then, a 50 WV, 220 μF electrolytic capacitor 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 pulp was beaten into 680 ml of CSF, the thickness was 50.2 μm, the density was 0.278 g / cm ³ , and the tensile strength was 0. A 7 kg / 15 mm round mesh double paper was made. Then, a 50 WV, 220 μF electrolytic capacitor 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 round mesh double paper of 0.0 kg / 15 mm was made. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

[Conventional Example 5] → Corresponding to Example 4 A mixture of 50% by weight of esparto pulp and 50% by weight of manila hemp was beaten to 560 ml of CSF, and the thickness was 40.0 μm, the density was 0.503 g / cm ³ , and the tensile strength was 3 A round mesh double paper of 0.2 kg / 15 mm was made. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

[Conventional Example 6] → Corresponding to Example 5 A mixture of 40% by weight of esparto pulp and 60% by weight of manila hemp was beaten to 440 ml of CSF, and the thickness was 30.4 μm, the density was 0.596 g / cm ³ , and the tensile strength was 3 A 0.8 kg / 15 mm round mesh double paper was made. Then, a 50 WV, 220 μF electrolytic capacitor was manufactured using this electrolytic paper.

Regarding the electrolytic paper 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 (sec / 100 cc), chemical conversion (V), paper dust generation (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 Measured by the method specified in JIS C2301 (electrolytic capacitor paper).

(2) Airtightness The airtightness was measured by a B-type tester (Gurley densometer) in accordance with the section “12.1 Airtightness” specified in JIS C2111 (Testing method for electrical insulating paper). However, an adapter having a hole portion of 6 mmψ was used. For the electrolytic paper having an air density of 1 second or less, the measurement was performed by stacking five sheets and converted to one sheet.

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

(4) Paper dust generation amount Two cutter blades are fixed at the center of the tester provided with unwinding and winding at intervals of 5 cm. The 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 on the cutter blade, and dropped off during this. The amount of paper dust was measured. The average of four measurements was displayed.

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

(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.

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

As shown in the results of Table 1, in the present invention using the electrolytic paper obtained by impregnating and applying the purified solution of the paper strength agent, the short-circuit defect rate is remarkably improved without deteriorating the chemical conversion and ESR. . For example, in Example 1, dialdehyde starch was added to circular double-walled 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, which was made using a raw material of 100% by weight of Manila hemp pulp. The purified dilute solution was impregnated and applied, and dried with hot air while the wet paper was in a swollen state to increase the thickness and further reduce the density to a thickness of 59.8 μm, a density of 0.236 g / cm ³ , and a tensile strength of 1.2 kg / 15 mm. Comparative Example 1 was manufactured by impregnating and coating an unpurified commercially available epoxy resin onto a mesh double-sheet paper formed under the same conditions, and was manufactured to have the same thickness and the same density. It uses electrolytic paper. Although both the short-circuit failure rate and the ESR are almost the same as those of the first embodiment, the chemical conversion is extremely low at 30 V, compared to 625 V of the first embodiment. 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 problem of the present invention, it is necessary that the paper strength agent used is purified.

  Conventional example 1 uses a mixed material of CSF 450 ml sisal pulp 30% by weight, chopped glass fiber 50% by weight and vinylon binder fiber 20% by weight, and the binder fiber is heat-sealed on a cylinder dryer of a paper machine. Then, the paper was formed to have substantially the same thickness and the same density as in Example 1. Although the thickness and the density are substantially the same, the ESR is improved to 0.1919 Ω / 1 kHz in Conventional Example 1 to 0.0919 Ω / 1 kHz in Example 1. In the conventional example 1, since the binder fiber is melted to form a film (film shape), which blocks the fiber gap and inhibits the ionic conduction of the electrolytic solution, the ESR is worse than that in the example 1 even at the same density. It is. In contrast, in Example 1, the interfiber space was maintained even when the purified solution of the paper strength agent was impregnated and applied, so that the ESR could be improved. Also, the tensile strength of Conventional Example 1 is 450 ml of CSF and the degree of beating is advanced, and the tensile strength of Conventional Example 1 is 0.8 kg / 15 mm, even though CSF is 720 ml. 1 has risen significantly to 1.2 kg / 15 mm. 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, but has no ESR because it does not have a film-forming effect like binder fibers. It can be seen that the results are also good.

  In Conventional Example 2, a mixed paper made of 70% by weight of Manila hemp pulp and 30% by weight of polypropylene fiber beaten to 350 ml of CSF was subjected to a heat treatment in post-processing to melt the polypropylene, and was produced. The manila hemp pulp is beaten excessively, the formation of paper balls etc. of the manila hemp pulp occurs, the short defect rate is as high as 15.2%, and the film forming action of the molten polypropylene is required. As a result, the ESR deteriorates to 0.1305 Ω / 1 kHz.

Example 2 is an electrolytic paper impregnated with a diluted solution of polyacrylamide impregnated and coated on a mesh double-sheet 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 has 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 0.1059Ω / 1 kHz. On the other hand, Conventional Example 3 is electrolytic paper of approximately the same thickness and density formed by mixing the same raw material as in Example 2 with 680 ml of CSF. Conventional Example 3 achieves a low ESR of 0.1092 Ω / 1 kHz by reducing the density to 0.278 g / cm ³ , but has a tensile strength of 0.7 kg / 15 mm and a short defect rate of 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 a purified solution of a paper strength agent, and the short-circuit failure rate was significantly reduced to 8.4%. Since the air gap is maintained, the ESR also shows a good value of 0.1059Ω / 1 kHz. Further, in the capacitor element winding process, in the conventional example 3, the electrolytic paper is frequently broken and productivity is remarkably impaired, but in the second example, the electrolytic paper is not broken.

Example 4 is an electrolytic paper coated with a dilute solution of purified polyacrylamide impregnated and coated on a mesh double-sheet paper made from a mixed material of 50% by weight of esparto pulp and 50% by weight of manila hemp pulp with CSF of 600 ml. The density is 0.506 g / cm ³ , the tensile strength is 4.4 kg / 15 mm, the amount of generated paper dust is 16 mg / 1000 m, the short-circuit defect rate is 0.6%, and the ESR is 0.1510Ω / 1 kHz. On the other hand, Conventional Example 5 is the most widely used electrolytic paper for low ESR at present, and uses electrolytic paper obtained by beating the same mixed raw material to 560 ml of CSF and making it to have approximately the same thickness and the same density. The tensile strength was 3.2 kg / 15 mm, the amount of paper dust generated 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 refining solution of the paper strength agent was impregnated and applied to improve the tensile strength significantly without excessive beating was used, and the short-circuit failure rate was significantly reduced without deteriorating the ESR. ing. Further, in the element winding step, the generation of paper dust is greatly reduced, and paper clogging, core pull-out failure, contamination of the electrolyte, and the like due to dropped paper dust can also be reduced.

  As described in detail above, the electrolytic capacitor according to the present invention can be used as 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 in that the purified solution is impregnated and applied to electrolytic paper, and the following operation and effect can be obtained. That is, the increase in tensile strength due to impregnation application of the purified solution of the paper strength enhancer promotes excessive beating of natural vegetable fibers, unlike electrolytic paper that has improved tensile strength by using heat-fused fibers, Since there is no film-forming action, the bonding strength of the fibers of the electrolytic paper is increased while maintaining the interfiber space, and the short-circuit failure rate can be significantly reduced by a large increase in the tensile strength without deteriorating the ESR. In addition, even if a raw material obtained by subjecting a natural plant fiber to slight beating or a material having a large CSF with a shallower beating degree is used, the paper strength is increased at the point of contact between the fibers in the paper layer. The agent is effectively fixed, the bonding strength between the fibers is increased, and the fibers penetrate into the interior of the fiber, so that the strength of the single fiber itself can be increased. This makes it possible to produce electrolytic paper in the ultra-low-density region, which was conventionally considered to be difficult to use in terms of strength in practical use. The paper powder trouble can be reduced by greatly reducing, and the productivity in the electrolytic capacitor manufacturing process can be remarkably improved. Furthermore, since natural plant fiber having a large CSF value can be used as a raw material, beating power can be reduced.

Claims (12)

  In an electrolytic capacitor in which electrolytic paper is interposed between an anode foil and a cathode foil, an electrolytic paper is made from natural plant fiber having a CSF value of 500 ml or more as a raw material. An electrolytic capacitor characterized by being impregnated with a purified solution of the above.   In an electrolytic capacitor in which electrolytic paper is interposed between an anode foil and a cathode foil, an electrolytic paper is made from natural plant fiber having a CSF value of 500 ml or more as a raw material. An electrolytic capacitor characterized in that the purified solution is impregnated and applied so as to be fixed to the contact points between fibers in a paper layer.   In an electrolytic capacitor in which electrolytic paper is interposed between an anode foil and a cathode foil, an electrolytic paper is made from natural plant fiber having a CSF value of 500 ml or more as a raw material. An electrolytic capacitor characterized by increasing the bond strength between fibers while maintaining the voids between fibers by impregnating the purified solution of the paper strength enhancer into the fibers by impregnating and applying the purified solution of .   The electrolytic capacitor according to claim 1, 2 or 3, wherein the paper strength enhancer is one or more selected from starch, vegetable gum, semi-synthetic polymer or synthetic polymer.   5. The electrolytic capacitor according to claim 1, wherein the paper strength enhancer is impregnated and applied to the electrolytic paper in an amount of 0.05% by weight to 5.0% by weight.   5. The electrolytic capacitor according to claim 1, wherein the paper strength enhancer is impregnated with 0.1% to 3.0% by weight of the electrolytic paper.   7. The electrolytic capacitor according to claim 1, wherein the voltage of the electrolytic paper is from 300 to 650 V when evaluated by chemical conversion.   7. The electrolytic capacitor according to claim 1, wherein the voltage of the electrolytic paper is from 500 to 650 V when evaluated by chemical conversion.   The natural plant fiber constituting the electrolytic paper is one or more selected from manila hemp pulp, sisal pulp, and esparto pulp. The method according to claim 1, 2, 3, 4, 5, 6, 7, or 8. Electrolytic capacitor. 10. The electrolytic capacitor according to claim 1, wherein the density of the electrolytic paper is 0.20 to 0.70 g / cm ³ and the thickness is 20 to 70 μm. 10. The electrolytic capacitor according to claim 1, wherein the density of the electrolytic paper is 0.20 to 0.35 g / cm ³ and the thickness is 40 to 60 μm.   The electrolytic capacitor according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the tensile strength of the electrolytic paper is 1.1 kg / 15 mm or more.