JP2011165949A - Separator for electrolytic capacitor, and electrolytic capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for an electrolytic capacitor high in piercing strength even if it is thin, and to provide an electrolytic capacitor low in short circuit failure rate and ESR and small in variation of the ESR. <P>SOLUTION: The separator for an electrolytic capacitor is formed of a wet nonwoven fabric using a 80 mesh woven metal having a wire diameter of 0.14 mm and an opening of 0.18 mm as a sieving plate, and containing a solvent spun cellulose fiber having a modified freeness degree of 0-250 ml measured in conformity to JIS P8121 except for setting of sample concentration of 0.1% and an acrylic short fiber as essential constituents, and having a void content of 62.0-86.0%. The electrolytic capacitor includes the same. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrolytic capacitor separator and an electrolytic capacitor.

  Conventionally, as an electrolytic capacitor separator using an electrolytic solution, a paper separator in which a paper strength enhancer is attached to paper mainly composed of hemp pulp or esparto pulp (for example, see Patent Documents 1 to 3), regenerated cellulose A paper separator made of a fiber beating raw material and natural pulp (see, for example, Patent Document 4) is used. Moreover, the separator containing the chemical fiber with little thermal deterioration in electrolyte solution is disclosed (for example, refer patent document 5). These separators have a problem that, when the thickness is reduced in order to lower the ESR, the piercing strength is weakened, so that the burr at the edge portion of the electrode foil is likely to penetrate and the short-circuit defect rate is increased. It was.

JP 2001-267182 A Japanese Patent Application Laid-Open No. 2004-200395 JP 2004-228600 A Japanese Patent No. 3466206 JP 2002-367863 A

  In view of the above circumstances, an object of the present invention is to provide an electrolytic capacitor separator that is thin but has high piercing strength, and an electrolytic capacitor that has a low short-circuit defect rate and low ESR, and has small variations in ESR.

  As a result of intensive studies to solve this problem, the inventors of the present invention contain solvent-spun cellulose fibers having a modified freeness in a specific range and acrylic short fibers as essential components, and a specific range of empty fibers. A separator for electrolytic capacitors made of a wet nonwoven fabric having porosity has a strong piercing strength, and the electrolytic capacitor equipped with the separator has an excellent low short-circuit defect rate and low ESR, and has a small variation in ESR, leading to the present invention. It is a thing.

  That is, the present invention was measured in accordance with JIS P8121, except that an acrylic short fiber and an 80 mesh wire net having a wire diameter of 0.14 mm and an aperture of 0.18 mm were used as a sieve plate, and the sample concentration was 0.1%. Electrolytic capacitor characterized by comprising a solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml as an essential component and comprising a wet nonwoven fabric having a porosity of 62.0 to 86.0% It is a separator.

  The present invention is an electrolytic capacitor comprising the electrolytic capacitor separator of the present invention.

  The separator for an electrolytic capacitor of the present invention is a modified method measured according to JIS P8121, except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as a sieve plate, and the sample concentration is 0.1%. Since it comprises a solvent-spun cellulose fiber having a freeness of 0 to 250 ml and an acrylic short fiber as essential components and is made of a wet nonwoven fabric having a porosity of 62.0 to 86.0%, the thickness is small. Also, the puncture strength is strong, the penetration of the burr of the electrode foil can be suppressed, and the pores of the separator are uniformly formed, so that the electrolyte is not biased in the separator and the holding amount can be prevented from being insufficient. Therefore, the electrolytic capacitor including the separator has a low short-circuit defect rate and low ESR, and the variation in ESR is small.

It is a graph showing the relationship between Canadian standard freeness of solvent-spun cellulose fibers and modified freeness (freeness measured in accordance with JIS P8121 except that the sample concentration is 0.03%). Modified drainage of solvent-spun cellulose fiber (measured in accordance with JIS P8121 except that 80 mesh wire mesh with a wire diameter of 0.14 mm and mesh size of 0.18 mm was used as the sieve plate, and the sample concentration was 0.1%. It is a graph showing modified freeness).

  In the present invention, the expression “separator” means an electrolytic capacitor separator.

  The acrylic short fiber in the present invention has a fiber length of 1 to 10 mm, and preferably 1 to 6 mm. If the fiber length is less than 1 mm, it may be easy to drop off from the separator or the puncture strength may be insufficient. If the fiber length is longer than 10 mm, the fibers may come together and the formation may become uneven. The fineness of the acrylic short fibers is preferably 0.05 to 1.0 dtex. If the fineness is less than 0.05 dtex, the puncture strength of the separator may be insufficient, and if it is greater than 1.0 dtex, the separator may have excessively high porosity or uneven thickness. Acrylic in the present invention is composed of a polymer of 100% acrylonitrile, and acrylonitrile is copolymerized with (meth) acrylic acid derivatives such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, and vinyl acetate. It refers to what you let me. Acrylic short fibers are excellent in resistance to electrolyte. The separator of this invention becomes strong in puncture strength by containing an acrylic short fiber.

  The modified freeness in the present invention means the freeness measured by changing either or both of the sample concentration and the sieve plate with respect to the Canadian standard freeness measurement method defined in JIS P8121. To do. So far, the relationship between Canadian standard freeness and modified freeness of natural cellulose fibers such as conifer wood pulp, hardwood wood pulp, hemp pulp and esparto pulp has been reported. The relationship between standard freeness and modified freeness has not been clarified. The inventors of the present invention refined solvent-spun cellulose fibers using a refiner, and measured Canadian standard freeness and modified freeness for each degree of refinement. It has been found that it is different from the drainage behavior of natural cellulose fibers disclosed in JP 2000-331663 A.

  FIG. 1 shows the relationship between Canadian standard freeness and modified freeness of solvent-spun cellulose fibers. In FIG. 1, the standard freeness means the Canadian standard freeness of JIS P8121, and the modified freeness means the filter measured according to JIS P8121 except that the sample concentration is 0.03%. It means water content. The horizontal axis in FIG. 1 indicates the degree of miniaturization, and the degree of miniaturization progresses toward the right. The Canadian standard freeness is constant at 0.5 ml until the degree of refinement, but the freeness increases with further refinement. On the other hand, the modified freeness increases as the degree of refinement progresses. This drainage behavior is the drainage behavior of natural cellulose fibers disclosed in JP 2000-331663 A, that is, the Canadian standard freeness and modified freeness decrease as the degree of refinement progresses. The drainage behavior is quite different. The reason why the degree of freezing increases as the degree of refinement increases is that the fiber length of the solvent-spun cellulose fiber decreases as the refinement progresses, and there is less entanglement between the fibers especially when the sample concentration is low. This is because it becomes difficult to form a fiber network, and the solvent-spun cellulose fibers themselves pass through the holes in the sieve plate. In other words, in the case of solvent-spun cellulose fibers that have been refined, an accurate freeness cannot be measured by the measuring method of JIS P8121. In more detail, natural cellulose fibers are in a state where many fine fibrils are torn apart from the trunk of the fiber as the degree of refinement progresses, so fibers tend to be entangled with each other via fibrils, and a fiber network is easily formed. On the other hand, the solvent-spun cellulose fiber is easily finely divided in parallel to the long axis of the fiber by the refining treatment, and the uniformity of the fiber diameter in each fiber after division is high, so that the average fiber length becomes shorter. It is considered that the fibers are less likely to be entangled with each other and it is difficult to form a fiber network.

  Therefore, the present inventors have studied to measure the exact freeness of solvent-spun cellulose fibers. FIG. 2 shows the modified freeness measured by changing both the sample concentration and the sieve plate. That is, the modified freeness measured by using an 80-mesh wire net instead of the sieve plate specified in JIS P8121, and setting the sample concentration to 0.1%. The wire diameter of 80 mesh was 0.14 mm in diameter, and a wire mesh (manufactured by PULP AND PAPER RESEARCH INSTITUTE OF CANADA) having an opening of 0.18 mm was used. The zero on the horizontal axis in FIG. 2 means solvent-spun cellulose fibers that have not been refined at all. As can be seen from FIG. 2, as the degree of refinement progresses, the freeness decreases, and the solvent-spun cellulose fibers are prevented from coming off, and the freeness can be measured more accurately. Hereinafter, the modified freeness in the present invention is based on JIS P8121, except that an 80 mesh wire net having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as a sieve plate, and the sample concentration is 0.1%. This means the measured modified freeness, and is simply expressed as “modified dryness” unless otherwise specified.

  Solvent-spun cellulose fibers with a modified freeness of 0 to 250 ml have a thin fiber diameter and high uniformity, so the pore diameter of the separator is relatively uniform, and the electrolyte is not evenly distributed or retained in the separator. Can be prevented. The solvent-spun cellulose fiber of the present invention preferably has a modified freeness of 0 to 200 ml, more preferably 0 to 160 ml. If the modified freeness exceeds 250 ml, the refinement process is insufficient, the fiber division does not proceed sufficiently, and the proportion of the original thick fiber diameter remains large, so a large through-hole is formed in the separator. The burrs at the edge portions of the electrode foil are likely to penetrate and the short-circuit defect rate is increased.

  To obtain solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml, disperse solvent-spun cellulose short fibers in water at an appropriate concentration, and use this as refiner, beater, mill, milling device, high-speed rotating Rotating blade type homogenizer that gives shearing force by blade, double-cylindrical high-speed homogenizer that generates shearing force between a cylindrical inner blade that rotates at high speed and a fixed outer blade. By passing through an ultrasonic crusher or the like, the conditions such as the shape of the blade, the sample concentration, the flow rate, the number of treatments, the treatment speed, and the like may be adjusted for fine processing.

  The length weighted average fiber length of the solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml in the present invention is preferably 0.2 to 3.0 mm. If it is less than 0.2 mm, the fiber length is too short, and it may be easy to fall off the separator. If it exceeds 3.0 mm, the refinement is insufficient, the ratio of the thick fiber diameter increases, the through hole tends to open in the separator, the fiber is kinked, the texture and the thickness vary, and the ESR Variation may increase. The length-weighted average fiber length of the solvent-spun cellulose fiber in the present invention can be measured using a commercially available fiber length measuring device that is obtained by utilizing the deflection characteristics obtained by applying laser light to the fiber.

  The total content of the short acrylic fiber and the solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml in the separator of the present invention is preferably 40 to 100% by mass. If it is less than 40% by mass, the puncture strength may be insufficient, the ESR of the electrolytic capacitor equipped with the separator may be high, or the ESR may be highly variable. The ratio of the short acrylic fiber and the solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml in the separator of the present invention is preferably 1: 9 to 8: 1 and more preferably 3:17 to 3: 1. preferable. When the ratio of the acrylic short fibers is less than 1: 9, the puncture strength of the separator may be insufficient, and when it is more than 8: 1, it may be difficult to reduce the thickness of the separator or ESR may be increased.

  The separator of the present invention may contain fibers other than acrylic short fibers and solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml. For example, short fibers and fibrils made of polyamide, solvent-spun cellulose and regenerated cellulose short fibers, natural cellulose fibers, pulped and fibrillated natural cellulose fibers, solvent-spun cellulose fibers having a modified freeness of more than 200 ml, glass, Inorganic fibers made of alumina, silica and the like.

  The polyamide may be an aliphatic polyamide, an aromatic polyamide, or a wholly aromatic polyamide, but is preferably a wholly aromatic polyamide having excellent heat resistance. The short fiber of polyamide, solvent-spun cellulose or regenerated cellulose preferably has a fiber length of 1 to 10 mm, more preferably 1 to 6 mm. If the fiber length is less than 1 mm, it may be easy to fall off from the separator, and if it is longer than 10 mm, the fibers may come together and the formation may become uneven. The fineness of the short fibers of polyamide, solvent-spun cellulose and regenerated cellulose is preferably 0.01 to 2.0 dtex. If it is less than 0.01 dtex, the strength of the fiber itself is weak and the separator may break easily. If it is thicker than 2.0 dtex, it may be difficult to reduce the thickness of the separator.

  The natural cellulose fiber pulped product or fibrillated product preferably has a modified freeness of 0 to 400 ml. When the modified freeness exceeds 400 ml, the ratio of the thick fiber diameter increases, and the thickness unevenness is likely to occur in the separator. The average fiber diameter of the inorganic fibers is preferably 0.1 to 10.0 μm, and more preferably 0.1 to 3.0 μm. If the average fiber diameter is less than 0.1 μm, the inorganic fibers are likely to be broken, so that they may be easily detached from the separator, and if it is thicker than 10.0 μm, it may be difficult to reduce the thickness of the separator. The average fiber length of the inorganic fibers is preferably 0.1 to 10.0 mm, and more preferably 0.1 to 5.0 mm. If the average fiber length is less than 0.1 mm, the inorganic fibers may easily fall off from the separator, and if it is longer than 10.0 mm, the texture and thickness of the separator may be likely to be uneven.

  The separator of the present invention has a porosity of 62.0 to 86.0%. The porosity means a value obtained by dividing the value obtained by subtracting the density of the separator from the specific gravity of the separator by the specific gravity of the separator and multiplying by 100. The specific gravity of the separator is calculated from the specific gravity and ratio of the fibers constituting the separator. When the porosity is less than 62.0%, the retention of the electrolytic solution is deteriorated and the ESR of the electrolytic capacitor is increased. If the porosity is larger than 86.0%, the short-circuit defect rate increases and the variation of ESR increases.

  The separator of the present invention can be produced by a wet papermaking method. One layer may be used, or two or more layers may be combined. Specifically, a slurry in which a predetermined fiber is dispersed at a predetermined concentration is prepared, and a circular paper machine, a long paper machine, an inclined paper machine, a short paper machine, an inclined short paper machine, and a combination thereof are combined. What is necessary is just to make wet paper using any of a paper machine. After wet papermaking, heat treatment, calendering, thermal calendering, etc. are performed as necessary.

  In order to set the porosity of the separator of the present invention to 62.0 to 86.0%, the density of the separator may be adjusted so as to obtain a desired porosity based on the specific gravity of the separator. When the content of thick fibers is increased, the density of the separator is reduced and the porosity is increased. When the thickness is reduced by calendering to increase the density of the separator, the porosity decreases. Increasing the content of fibers with a high specific gravity tends to increase the porosity.

  The separator of the present invention preferably has a thickness of 15 to 100 μm, more preferably 20 to 60 μm. If the thickness is less than 15 μm, it may be broken during handling or processing, or a hole may be formed. If it is thicker than 100 μm, the ESR of the electrolytic capacitor may increase.

  The separator of the present invention preferably has a Gurley air permeability of 0.02 to 3.00 s / 100 ml, and more preferably 0.10 to 2.00 s / 100 ml. The Gurley air permeability is measured according to JIS P8117. If the Gurley air permeability is less than 0.02 s / 100 ml, the burrs on the edge of the electrode foil are likely to penetrate, and the short-circuit defect rate of the electrolytic capacitor increases, and the deviation of the ESR occurs due to the uneven electrolyte in the separator. May become larger. If it is larger than 3.00 s / 100 ml, the ESR of the electrolytic capacitor may increase.

  The separator of the present invention preferably has an average puncture strength of 0.40 N or more, and more preferably 0.50 N or more. If the average piercing strength is less than 0.40 N, the short-circuit defect rate may be increased due to damage to the separator or the opening of the electrolytic capacitor. The piercing strength means a maximum load until a metal rod having a diameter of 1 mm is lowered at a constant speed perpendicular to the separator and the metal rod penetrates the separator. The average puncture strength is the average value obtained by measuring the puncture strength at any five or more locations of the separator sample.

  The electrolytic capacitor in the present invention uses a valve metal having an insulating oxide film formed on the surface of an aluminum foil as an anode, and uses an aluminum foil without an oxide film as a cathode. It refers to a structure in which an electrolyte is disposed between them.

  Solvents for the electrolyte include water, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol phenyl ether, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, diethylene Acetone alcohol, benzyl alcohol, amyl alcohol, glycerin, γ-butyrolactone, α-acetyl-γ-butyrolactone, β-butyrolactone, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetoamide , Hexamethylphosphoric amide, acetonitrile, acrylonitrile, adiponitrile, 3-methoxypropionitrile, N-methyl-2-oxazolidinone, 3,5-dimethyl-2-oxazolidinone, ethylene carbonate, propylene carbonate, dimethylsulfone, ethylmethyl Examples include sulfone, diethylsulfone, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane. These solvents are used alone or in combination. Ethylene glycol or γ-butyrolactone is preferable.

  Examples of the electrolyte of the electrolytic solution include boric acid, succinic acid, adipic acid, pimelic acid, maleic acid, benzoic acid, phthalic acid, salicylic acid, suberic acid, azelaic acid, sebacic acid, undecanoic acid, 2-methyl azelaic acid, 1,6 -Decanedicarboxylic acid, 5,6-decanedicarboxylic acid, salts of these acids (e.g. ammonium adipate, ammonium hydrogen maleate dimethylamine, 2-butyloctanedioic acid ammonia, hydrogen phthalate 1-ethyl-2,3- Dimethyl imidazolium, etc.), tetramethylammonium hydroxide, ethylmethylamine, diethylamine, trimethylamine, diethylmethylamine, ethyldimethylamine, triethylamine, tetramethylammonium, triethylmethylammonium, tetraethylammonium, carbon number 1-11 Imidazole compounds quaternized with an alkyl group or an arylalkyl group, benzimidazole compounds, alicyclic amidine compound and the like are used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to an Example.

Example 1
Slurry 1 shown in Table 1 was prepared, wet papermaking was performed using a circular paper machine, and a calendar process was performed to produce the separator of Example 1.

Examples 2, 4, 7, 8
Slurries 2, 3, 6, and 7 shown in Table 1 were prepared, and wet papermaking was performed using a circular paper machine to produce separators of Examples 2, 4, 7, and 8.

Examples 3, 5, 6, 9-12
The separators of Examples 3, 5, 6, and 9 to 12 were used in the same manner as in Example 1 except that the slurry 2, 4, 5, and 8 to 11 shown in Table 1 were used and the calendar treatment was performed by adjusting the calendar pressure. Produced.

(Comparative Examples 1, 2, 5, 7, 8)
Slurries 12, 13, 15, 17, and 18 shown in Table 1 were prepared, and wet paper making was performed using a circular paper machine, and separators of Comparative Examples 1, 2, 5, 7, and 8 were produced.

(Comparative Examples 3, 4, 6)
Slurries 2, 14, and 16 shown in Table 1 were prepared, wet papermaking was performed using a circular paper machine, and calendering was performed by adjusting the calender pressure to produce separators of Comparative Examples 3, 4, and 6.

(Comparative Example 9)
The slurry 19 shown in Table 1 was prepared, and three layers were laminated using a triple-lined net paper machine, and a polyacrylamide diluted solution was immersed using an on-machine direct roll coater. The separator of Comparative Example 9 was produced by pressing with a press roll so that the adhesion amount was 3.0 mass% and drying. Polyacrylamide was used in which anionic impurities were previously removed and the total amount of cations was purified to 25 ppm or less.

  A1 to A6 in Table 1 mean solvent-spun cellulose fibers, and their modified freeness is as shown in Table 1. B1 is acrylic short fiber having a fineness of 0.1 dtex and a fiber length of 3 mm (product name: Bonnell), B2 is acrylic short fiber having a fineness of 0.4 dtex and a fiber length of 5 mm (product name: Bonnell), B3 means an acrylic short fiber (manufactured by Mitsubishi Rayon, trade name: Bonnell) having a fineness of 1.0 dtex and a fiber length of 5 mm. C1 means a solvent-spun cellulose short fiber having a fineness of 1.7 dtex and a fiber length of 4 mm (trade name: Tencel, manufactured by Lenzing). D1 means a linter fiber having a modified freeness of 270 ml and a length-weighted average fiber length of 0.21 mm. E1 is a polyester short fiber having a fineness of 0.1 dtex and a fiber length of 3 mm (made by Teijin Fibers, trade name: TM04PN), E2 is a polyester short fiber having a fineness of 0.5 dtex and a fiber length of 5 mm (made by Teijin Fibers, trade name: TA04N) means. F1 means Manila hemp, and its Canadian standard freeness is as shown in Table 1. F2 means esparto pulp, and its Canadian standard freeness is as shown in Table 1. The modified freeness of F1 and F2 were both 800 ml. The specific gravity of solvent-spun cellulose fiber, solvent-spun cellulose short fiber, linter fiber, Manila hemp, and esparto pulp was 1.50. The specific gravity of the acrylic short fiber was 1.17. The specific gravity of the polyester short fiber was 1.40.

  The separators of Examples and Comparative Examples were evaluated by the following test methods, and the results are shown in Table 2.

<Thickness>
The thickness of the separator was measured according to JIS C2111.

<Density>
The density of the separator was measured according to JIS C2111.

<Porosity>
The porosity of the separator was calculated by dividing the value obtained by subtracting the density of the separator from the specific gravity of the separator by the specific gravity of the separator and multiplying by 100.

<Air permeability>
Using a Gurley permeability meter having a circular hole with an outer diameter of 28.6 mm, the time required for 100 ml of air to pass through the separator was measured at any five or more locations per sample, and the average value was obtained.

<Average puncture strength>
Mounted on a 40mmφ fixed frame installed on a desktop material testing machine (trade name: STA-1150, manufactured by Orientec Co., Ltd.), and a metal needle (manufactured by Orientec Co., Ltd.) with a diameter of 1.0mm on the sample surface It was lowered until it penetrated at a constant speed of 50 mm / min. The maximum load (N) at this time was measured at five or more arbitrary locations, and the average value was defined as the average puncture strength.

<Electrolytic capacitor>
Using an aluminum foil subjected to chemical etching on the anode and an unchemically etched aluminum foil as the cathode, the separators of Examples 1 to 12 and Comparative Examples 1 to 9 are respectively sandwiched between them to produce a winding element. did. An electrolytic solution in which γ-butyrolactone was dissolved so that the concentration of 1,2,3,4-tetramethylimidazolinium phthalate was 30% by mass was injected into the winding element and sealed. Electrolytic capacitors 1 to 12 and Comparative Examples 1 to 9 were produced.

  The electrolytic capacitors of Examples and Comparative Examples were evaluated by the following test methods, and the results are shown in Table 3.

<ESR>
The ESR of the electrolytic capacitor was measured using an LCR meter at a frequency of 20 ° C. and 1 kHz, and an average value of 100 capacitors was calculated.

<Variation>
The standard deviation of ESR of the electrolytic capacitor was used as an index of variation. The smaller the standard deviation value, the smaller the variation and the better.

<Short defective rate>
A winding element was produced by sandwiching the separators of Examples and Comparative Examples between the anode and the cathode, and the presence or absence of conduction between both electrodes was confirmed by a tester without impregnating the electrolyte. The proportion of conductive winding elements in 100 winding elements was defined as a short-circuit defect rate.

<Defect rate after reflow>
The electrolytic capacitor was immersed in a solder bath at 260 ° C. for 30 seconds, subjected to reflow treatment, taken out and allowed to cool, and then ESR was measured. The ratio of electrolytic capacitors in which the separator was short-circuited due to melting or deformation or the ESR showed an abnormal value was defined as the defective rate after reflow.

  The separators of Examples 1 to 12 contain acrylic short fibers and solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml as essential components, and are wet with a porosity of 62.0 to 86.0%. Since it consists of a nonwoven fabric, the average puncture strength was strong and excellent. The electrolytic capacitors of Examples 1 to 12 including the separators of Examples 1 to 12 were excellent in that the short-circuit defect rate and ESR were low, and the variation in ESR was small.

  Since the separator of Comparative Example 1 does not contain solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml and contains solvent-spun cellulose fibers having a modified freeness of 260 ml, the separator has a large through-hole. Since the burr of the electrode foil was easily penetrated, the electrolytic capacitor of Comparative Example 1 provided with the separator had a slightly high short-circuit defect rate. In addition, since the electrolyte was biased in the separator, the ESR variation was large.

  Since the separator of Comparative Example 2 did not contain acrylic short fibers and the porosity exceeded 86.0%, the puncture strength was remarkably weak, and the burr of the electrode foil was easy to penetrate. Comparative Example 2 provided with the separator The electrolytic capacitor had a high short-circuit defect rate. In addition, since the electrolyte was biased in the separator, the ESR variation was large.

  Since the separator of Comparative Example 3 had a porosity of less than 62.0%, the amount of electrolyte retained was insufficient, and the electrolytic capacitor of Comparative Example 3 equipped with the separator had high ESR.

  Since the separators of Comparative Examples 4 and 8 do not contain any solvent-spun cellulose fiber having a modified freeness of 0 to 250 ml, Comparative Example 4 having a large through-hole and easy penetration of burr on the electrode foil. The electrolytic capacitors No. 8 and No. 8 had a high short-circuit defect rate. In addition, since the electrolyte was biased in the separator, the ESR variation was large.

  The separator of Comparative Example 5 does not contain acrylic short fibers, and mainly contains polyester short fibers having a problem with the electrolytic solution resistance. Therefore, the polyester short fibers are dissolved in the electrolytic solution during the reflow treatment, The electrolytic capacitor of Comparative Example 5 provided with the separator had a defect rate of 100% after reflow.

  Since the separator of Comparative Example 6 does not contain short acrylic fibers and is composed of 100% solvent-spun cellulose fiber having a modified freeness of 80 ml, the puncture strength is weak, and the electrolytic capacitor of Comparative Example 6 equipped with the separator is short. The defective rate was high.

  The separator of Comparative Example 7 contains acrylic short fibers and solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml, but the porosity is more than 86.0%. The electrolytic capacitor of Example 7 had a high short-circuit defect rate.

  The separator of Comparative Example 9 does not contain short acrylic fibers, solvent-spun cellulose fibers having a modified freeness of 0 to 250 ml, and consists of Manila hemp and esparto having a Canadian standard freeness of 640 ml (modified freeness of 800 ml). Therefore, the puncture strength was weak, and the electrolytic capacitor of Comparative Example 9 equipped with the separator had a high short-circuit defect rate. Moreover, since the electrolyte was biased in the separator, the ESR variation was large.

Claims (2)

  A solvent having a modified freeness of 0 to 250 ml measured according to JIS P8121, except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as the sieve plate, and the sample concentration is 0.1%. A separator for an electrolytic capacitor, comprising a spun cellulose fiber and an acrylic short fiber as essential components, and comprising a wet nonwoven fabric having a porosity of 62.0 to 86.0%.   An electrolytic capacitor comprising the electrolytic capacitor separator according to claim 1.

Images