JPWO2013069146A1 - Electrolytic capacitor separator and electrolytic capacitor - Google Patents

Abstract

An object of the present invention is to provide a thin, uniform, dense and low-impurity film made of cellulose as a raw material, and to provide an electrolytic capacitor that is reduced in size and / or increased in capacity by using the film as a separator. A cellulose solution in which cellulose is dissolved in an amine oxide solvent is formed into a film and immersed in water or a poor solvent of an amine oxide solvent to coagulate and regenerate the cellulose. The regenerated cellulose is washed with water to remove the amine oxide solvent and then dried to obtain a thin, uniform and dense cellulose film with few impurities. The obtained cellulose film is used as a separator to be interposed between an anode aluminum foil and a cathode aluminum foil and wound to produce a capacitor element. The capacitor element is immersed in a liquid electrolyte solution to impregnate the electrolyte, and the case Then, the electrolytic capacitor is provided with a reduced size and / or increased capacity by sealing and aging. [Selection figure] None

Description

  The present invention relates to a separator for an electrolytic capacitor and an electrolytic capacitor, for example, a separator for an aluminum electrolytic capacitor capable of realizing a reduction in size and / or an increase in capacity using a cellulose film as a separator, and an electrolytic capacitor using the separator. .

  In general, an aluminum electrolytic capacitor is manufactured by winding a separator between an anode aluminum foil and a cathode aluminum foil to produce a capacitor element. The capacitor element is impregnated with an electrolytic solution, placed in a case, sealed, and then aged. And making it.

  The dielectric of the aluminum electrolytic capacitor is an extremely thin oxide film formed by electrolytic oxidation (chemical conversion) on the surface of the anode aluminum foil. By impregnating the separator in the capacitor element with the electrolytic solution, the electrolytic solution becomes a true cathode, and the oxide film on the surface of the anode aluminum foil becomes a dielectric.

The capacitance of the capacitor is represented by the following formula (1).
C = ε · S / d Formula (1)
C: Capacitance (F)
ε: dielectric constant of dielectric (F / m)
S: Area of electrode (m ² )
d: Distance between electrodes (m)

  Since the relative permittivity [ε in equation (1)] depends on the type of dielectric, in order to increase the capacitance [C in equation (1)] of the aluminum electrolytic capacitor, the area of the electrode [expression (1) It is effective to increase the S] and reduce the distance between the electrodes [d in equation (1)]. Since an oxide film has a high withstand voltage per unit thickness and can form an oxide film having an arbitrary thickness, an aluminum electrolytic capacitor has a smaller distance d between electrodes than other capacitors such as a ceramic capacitor and a film capacitor. Further, by etching the anode aluminum foil, the effective area can be increased by about 20 to 120 times as compared with the apparent area, so that the area S of the electrode is large. Therefore, aluminum electrolytic capacitors have the greatest feature that they can realize a small size and a large capacity compared to other capacitors.

  In the aluminum electrolytic capacitor, the main role of the separator is to isolate both electrode foils and hold the electrolytic solution. The material of the separator is required to have electrical insulation, and hydrophilicity and lipophilicity are required for holding various types of electrolytes. Cellulose has both of these characteristics, and electrolytic paper, which is cellulose paper, is used for the separator.

  In recent years, energy conservation policies and oil alternative energy policies not only in Japan but also in other countries have expanded the use of energy efficient inverter circuits, etc. in all environmental fields such as wind power generation, solar cells, hybrid vehicles, electric vehicles, and various energy-saving devices. It is continuing. Also, in home appliances, many devices such as air conditioners, refrigerators, washing machines, and lighting devices are converted into inverters for the purpose of energy saving.

  Here, the inverter is a variable speed device that highly controls the rotation of the motor by controlling the frequency and voltage. In the inverter, an aluminum electrolytic capacitor is used for the purpose of smoothing fluctuations included in the direct current output from the rectifier. Aluminum electrolytic capacitors account for a large volume ratio among inverter components, and there is a strong demand for further miniaturization.

Aluminum electrolytic capacitors are also used for smoothing inputs such as switching power supplies. A switching power supply is a conversion device that outputs an alternating current input from a commercial power supply as an arbitrary direct current. Even in a power source such as a switching power source, there are restrictions on the installation space of the aluminum electrolytic capacitor and there is a demand for downsizing the power source.
There are many cases where a plurality of aluminum electrolytic capacitors are used, and if the capacity is increased with the same size, the number of mounted capacitors can be reduced. Therefore, there is a strong demand for higher capacity in conjunction with downsizing. In aluminum electrolytic capacitors, further downsizing or higher capacity is an important development point common to various fields.

  The element of the aluminum electrolytic capacitor is manufactured by winding a separator between the anode aluminum foil and the cathode aluminum foil, so if the separator is thinned, the element of the same volume is a dielectric because the length of the anode aluminum foil can be increased. The area of the oxide film [S in the above formula (1)] can be increased, and the capacity of the aluminum electrolytic capacitor can be increased. Moreover, since the volume of the element is reduced by making the separator thinner without changing the area of the oxide film [S in the above formula (1)] at the same capacity, it is possible to reduce the size of the aluminum electrolytic capacitor.

  Causes of short-circuiting of aluminum electrolytic capacitors include penetration and breakage of the separator due to burrs at the tab portion, electrode foil end, or burr between the electrode foil and the lead wire connection, and damage to the separator due to mechanical stress such as vibration and impact. , Electrical stress such as spark discharge, aging process during capacitor production, oxide film dielectric breakdown derived from oxide film defects, and the like. Making the separator thinner reduces the resistance to these short-circuit causes (hereinafter short-circuit resistance). In order to maintain the same short-circuit resistance even if the separator is thinned, it is effective to make the separator more uniform and dense and to increase the density.

In the case of medium- and high-pressure aluminum electrolytic capacitors, electrolytic paper having a sufficiently high density and thickness is used as a separator to ensure short-circuit resistance. Since the risk of short-circuiting increases as the operating voltage increases, a high density electrolytic paper having a density of 0.70 to 1.00 g / cm ³ without the presence of pinholes made from a raw material with high fiber beating using a long net paper machine ( (Hereinafter referred to as “long web single paper”) or a high density layer formed with a paper web machine and a low density layer formed with a circular paper machine on a paper machine. Electrolytic paper (hereinafter referred to as “long web double paper”) is used (Patent Document 1).

  In the high-density layer of these long net single paper and long net circular double paper, generally softwood kraft pulp that has been highly beaten with a large amount of electric power and beating time is used as a raw material. The cross-section of the softwood kraft pulp is a flat shape with a size of about 10 μm × 40 μm in an unbeaten state. it can. Paper disperses fibers in water and forms a paper layer on a papermaking net, so that a more uniform and dense paper layer can be formed as the fiber diameter is subdivided to subdivide the fiber diameter.

  However, it is difficult to make the diameters and lengths of all the fibers uniform even with higher beating. Therefore, paper becomes a sheet in which fibers of various sizes are bonded by physical entanglement and hydrogen bonding, and it is difficult to make a completely uniform structure inside the paper, and there is a limit to improving uniformity and compactness. .

  Electrolytic paper is also limited in terms of thinning. In the paper manufacturing process, on the paper making wire, during the initial dewatering, many fine fibers pass through the net and gradually form a paper layer, and the drainage speed becomes slower. The fibers are retained on the wet paper and a dense paper layer can be formed gradually. Since the thickness of the paper depends on the diameter of the raw material fiber and the number of the overlapping fibers, in order to make a thin paper, it is necessary to use a raw material in which the ratio of the fibers having a small fiber diameter is increased.

  Highly beaten raw material with a small fiber diameter has a short fiber length. For example, when making paper of 10 μm or less, a lot of fibers come out under the net at the time of initial dehydration, so the yield rate decreases. At the same time, there will be pinholes and irregularities. There are no fibers in the pinhole, and in the formation unevenness, the fibers are unevenly distributed, and there are portions where the fibers are few. If there are pinholes or uneven formation in the separator, the electric charge concentrates on the part and a short circuit occurs. Further, paper having a thickness of 10 μm or less also causes frequent sheet breakage troubles in the paper making process because the number of physical adhesion points between fibers is reduced and the wet paper strength and dry paper strength are insufficient.

Since the density of the paper is calculated by the following formula (2), the density increases as the thickness decreases with the paper having the same basis weight (weight of paper per 1 m ² : g / m ² ).
Density (g / cm ³ ) = basis weight (g / m ² ) / thickness (μm) Formula (2)

However, even when beaten further than the high beating raw material with a density of about 1.00 g / cm ³ , which is the highest density of the long bead single paper or the long net double paper, the fibers that fall out under the net during paper making However, it is difficult to improve the density by making it thinner because the fiber form forming the paper layer hardly changes with the increase in the ratio.

  The density can be increased by calendering post-processing after papermaking. However, even if the density is increased by this method, the fibers constituting the paper are only compressed in the thickness direction and the fiber size and surface density are reduced. Since there is no change, the short circuit resistance is not improved.

A typical example of a uniform sheet-like molded product is a film.
Since the separator for an aluminum electrolytic capacitor needs to hold an electrolytic solution, a film such as a polyethylene (PE) film or a polypropylene (PP) film that cannot be impregnated inside, or a polyvinyl alcohol (PVA) film A film that dissolves in such an electrolyte cannot be used as a separator. The aluminum electrolytic capacitor separator is required to have dimensional stability and chemical stability at a temperature of 100 ° C. or higher. PE film, PP film, PVA film and the like are difficult to use as a separator from the viewpoint of heat resistance.

  A typical viscose film in which cellulose is dissolved in an alkali such as sodium hydroxide and carbon disulfide is formed on a typical film that has the same cellulose as electrolytic paper. The cellulose is neutralized with an acid such as sulfuric acid. There is a cellulose film (cellulose film produced by the viscose method) produced by regenerating as above.

  Since the cellulose film produced by this viscose method is a film, it has a dense structure and a higher density than the electrolytic paper. Moreover, since it is a cellulose, it has hydrophilic property and lipophilicity. In the case of electrolytic paper, the low-density layer of the long-mesh round paper double paper mainly plays the role of holding the electrolytic solution. Since the hydrogen bond between the fibers and the cellulose molecules is broken and swells, the electrolyte can be retained. Cellulose films produced by the viscose method have high density, so there are no voids in the dry state, but when immersed in the electrolyte, hydrogen bonds between cellulose molecules are broken and swell, so that the electrolyte can be retained. .

However, since the cellulose film produced by the viscose method involves a chemical reaction that generates carbon disulfide gas in the process of regenerating cellulose, pinholes are easily formed. The cellulose film produced by the viscose method having a thickness of about 20 μm has about 10 pinholes / cm ² having a diameter of 10 μm or more, and the number of pinholes increases as the thickness decreases. Cellulose film produced by the viscose method has pinholes, so when compared with electrolytic paper of the same thickness, cellulose film produced by the viscose method is less short-circuit resistant than electrolytic paper with a lower density. Lower.

Moreover, the cellulose film produced by the viscose method contains sulfate in terms of the production method. When a separator having a high sulfate content is used, sulfate ions are eluted in the electrolytic solution, which corrodes an oxide film serving as an insulator for the anode aluminum foil of the aluminum electrolytic capacitor. The missing portion of the oxide film causes a short circuit failure and an increase in leakage current. For the above reasons, it is not suitable to use a cellulose film produced by the viscose method as a separator for an aluminum electrolytic capacitor.
Moreover, in order to make the viscosity of the cellulose solution at the time of manufacture the cellulose film produced by the viscose method, it is necessary to reduce the polymerization degree of cellulose. The decrease in the degree of polymerization decreases the strength of the cellulose film and the resistance to the electrolytic solution.

  Another typical regenerated cellulose production method is a copper ammonia rayon method. The copper ammonia solution used for producing the copper ammonia rayon is prepared by adding an ammonia solution and sodium hydroxide to copper sulfate. A cellulose film of the copper ammonia rayon method is manufactured by dissolving cellulose in a copper ammonia solution and extruding it into dilute sulfuric acid.

  The cellulose film produced by the copper ammonia rayon method contains a large amount of copper ions in addition to containing sulfate ions. When a separator with a high copper ion content is used, copper ions dissolve into the electrolyte, and when reverse voltage is applied while the capacitor is repeatedly charging and discharging, it precipitates as copper oxide on the defects in the oxide film of the anode aluminum foil. However, a failure that becomes a dendrite and penetrates the separator to cause a short circuit occurs. For these reasons, it is not suitable to use a copper ammonia rayon cellulose film as a separator for an aluminum electrolytic capacitor.

  Other cellulose solvents include lithium chloride / dimethylacetamide cellulose solvent, lithium hydroxide / urea cellulose solvent (Non-patent Document 1), sodium hydroxide / urea cellulose solvent (Patent Document 2), sodium hydroxide / thio. Urea-based cellulose solvents (Patent Document 3), ionic liquids and the like are known. However, cellulose films using lithium chloride / dimethylacetamide cellulose solvents have a high chlorine content, and lithium hydroxide / urea cellulose solvents, sodium hydroxide / urea cellulose solvents, and sodium hydroxide / thiourea cellulose solvents are practical. Moreover, since dilute sulfuric acid is used in the coagulation bath for neutralization of alkali, the sulfate content increases.

It is known that 1-butyl-3-methylimidazolium salt having an ionic liquid, such as Cl ⁻ , Br ⁻ , SCN ⁻ , BF ₄ ⁻ and PF ₆ ⁻ as an anion, dissolves cellulose (Non-patent Document 2). ) The ionic liquid that dissolves cellulose uses reactive chlorine and other halogens as anions. Since residual components of chlorine and halogen corrode the oxide film of the anode aluminum foil more than sulfate ions, it is not suitable to use a cellulose film produced using these ionic liquids as a separator. In addition, since the ionic liquid is very expensive, it is not suitable for manufacturing a constituent member of an aluminum electrolytic capacitor characterized by being inexpensive.

Japanese Patent No. 3693299 Patent publication 2008-542560 Patent Publication No. 2009-508015

Cellulose Experiments and Analytical Methods 15th Cell Dissolution and Regeneration Gelation of Cellulose in Alkaline-Urea Solvents Shigenori Kuga, CAI Jie Cellulose Communications Vol. 15 No.2 (2008) CMC Publishing Ionic Liquid II Chapter 13 Solubilization of Slightly Soluble Substances Yukinobu Fukaya, Hiroyuki Ohno

  It is an object of the present invention to provide a thin, uniform and dense film made of cellulose as a separator for an aluminum electrolytic capacitor and having few impurities. Another object of the present invention is to provide an aluminum electrolytic capacitor that is reduced in size and / or increased in capacity by using the cellulose film as a separator.

  As a means for solving the above object, for example, the following configuration is provided. That is, the separator for electrolytic capacitors is a film using cellulose as a raw material.

  And, for example, a film using cellulose as a raw material forms a cellulose solution in which cellulose is dissolved in an amine oxide solvent into a film shape, and the cellulose is coagulated by immersing in water or a poor solvent of an amine oxide solvent. It is a cellulose film obtained by regenerating, washing the regenerated cellulose with water to remove the amine oxide solvent and then drying.

For example, the amine oxide solvent is N-methylmorpholine-N-oxide. Furthermore, for example, the film thickness is 3 to 20 μm.
For example, the chlorine content of the film is 2 ppm or less. Alternatively, the sulfate content of the film is 10 ppm or less.

Or it is set as the electrolytic capacitor characterized by interposing the separator of the structure described above between anode foil and cathode foil.
For example, the separator is interposed between an anode aluminum foil and a cathode aluminum foil to produce a capacitor element. The capacitor element is immersed in a liquid electrolyte solution and impregnated with an electrolyte, and then placed in a case. Thereafter, the aluminum electrolytic capacitor is provided which is reduced in size and / or increased in capacity by sealing and aging.

  According to the present invention, the density, uniformity, and density can be improved, and a very dense and uniform film can be provided. By using this film as a separator for an electrolytic capacitor, The short-circuit resistance can be greatly improved, and the electrolytic capacitor can be further reduced in size and / or increased in capacity.

It is the plot figure which extracted and showed the relationship between the thickness of the separator of a 160 WV aluminum electrolytic capacitor, and the defect rate after aging. It is the plot figure which extracted and showed the relationship between the thickness of the separator of a 160 WV aluminum electrolytic capacitor, and the electrostatic capacitance of an aluminum electrolytic capacitor. It is the plot figure which extracted and showed the relationship between the thickness of the separator of a 160 WV aluminum electrolytic capacitor, and the impedance characteristic of an aluminum electrolytic capacitor.

It is the plot figure which extracted and showed the relationship between the thickness of the separator of a 450 WV aluminum electrolytic capacitor, and the defect rate after aging. It is the plot figure which extracted and showed the thickness of the separator of the 450 WV aluminum electrolytic capacitor, and the electrostatic capacitance of an aluminum electrolytic capacitor. It is the plot figure which extracted and showed the relationship between the thickness of the separator of a 450 WV aluminum electrolytic capacitor, and the impedance characteristic of an aluminum electrolytic capacitor.

  In an aluminum electrolytic capacitor according to an embodiment of the present invention, a cellulose film manufactured using an amine oxide cellulose solution is used as a separator interposed between an anode aluminum foil and a cathode aluminum foil.

  Tertiary amine oxide is preferably used as the amine oxide that is the main component of the amine oxide solvent applied to the embodiments of the present invention. As the tertiary amine oxide, any tertiary amine oxide can be used as long as it dissolves cellulose and mixes with water and is stable to water. It is particularly preferable to use N-methylmorpholine-N-oxide (hereinafter referred to as NMMO) from the standpoint of ease of recovery and purification. Here, the tertiary amine oxide which is stable to water means that it does not cause a chemical reaction with water.

  The composition of the cellulose solution used in one embodiment of the present invention according to the present invention preferably has a concentration range of 70 to 95% by weight of NMMO, 2 to 28% by weight of water, and 2 to 20% by weight of cellulose. When the ratio of NMMO is less than 70% by weight, dissolution of cellulose becomes difficult. If the concentration of cellulose in the solution is less than 2% by weight, a large amount of cellulose solution is required to produce a cellulose film, resulting in poor production efficiency. If the concentration exceeds 20% by weight, the viscosity of the cellulose solution increases. This is unsuitable for the production of thin films.

  Within this range, cellulose can be dissolved well and a uniform solution can be obtained. However, the dissolution conditions differ depending on the type of solvent, molding apparatus, and molding conditions, so the composition of the cellulose solvent is limited to this. is not.

  The melting temperature is preferably in the range of 75 ° C or higher and lower than 150 ° C. When the temperature is 75 ° C. or lower, a good cellulose solution cannot be obtained. When the temperature is 150 ° C. or higher, NMMO and cellulose may be decomposed. In particular, it is more preferable to perform dissolution at 120 ° C. or lower.

  The cellulose base used is chlorine-free (TCF) bleached or unbleached so that the chlorine content of the cellulose film is 2 ppm or less. If the chlorine content in the separator is more than 2 ppm, the corrosiveness to the oxide film becomes strong, causing a short circuit failure and an increase in leakage current, so that it is not suitable as a separator for an aluminum electrolytic capacitor. Here, the chlorine content is a value measured by the method described in JIS C 2300 Electrical Cellulose Paper Part 2 Test Method Chlorine Content Ion Chromatography (Extraction Method).

  Moreover, in order to make the sulfate content of a cellulose film into 10 ppm or less, it is preferable to use a cellulose with a sulfate content of 200 ppm or less. Sulfate is reduced in the washing step when forming a film, which will be described later. However, if cellulose with a content of 200 ppm or more is used, the sulfate content in the cellulose film may exceed 10 ppm when washing is insufficient. is there. When the sulfate content in the separator exceeds 10 ppm, the corrosiveness to the oxide film becomes strong, causing short circuit failure and increase in leakage current. In addition, let sulfate content here be the value which measured the extract used for the above-mentioned chlorine content measurement with the ion chromatograph.

  Wood pulp, non-wood pulp, mercerized pulp, dissolving pulp, and regenerated cellulose can be used as the cellulose base material. Among these, one kind or a combination of two or more kinds can be used, and paper produced from these cellulose base materials can also be used. It is particularly preferable to use dissolving pulp or cotton linter pulp as the cellulose base material. Dissolving pulp and cotton linter pulp have an α-cellulose content of 90% or more and high cellulose purity, and are therefore suitable for producing a uniform and homogeneous cellulose film. It is possible to adjust the properties of the cellulose film obtained by the difference in chemical properties and physical properties of the cellulose substrate.

  The cellulose solution is extruded through a heated extrusion die and fed through a slight air gap between the heated extrusion die and the coagulation bath into a coagulation bath composed of water or a poor solvent of NMMO. When no air gap is provided, the heated extrusion die is cooled by the coagulation bath, and the cellulose solution is solidified inside the extrusion die and clogging occurs.

  As a film forming method, in addition to the heat extrusion die, a method of casting on a heated substrate with a predetermined clearance, or a method of transferring and forming a film on a substrate using a heated roll may be used. After regenerating cellulose in a coagulation bath, it is washed with ion-exchanged water and dried to obtain a cellulose film that is thin, uniform and dense and has few impurities. Since the obtained cellulose film has hydrophilicity and lipophilicity, the hydrogen bond between cellulose is cut | disconnected and swollen by being immersed in electrolyte solution, and electrolyte solution can be hold | maintained inside.

  The thickness of the cellulose film is preferably 3 to 20 μm. The separator greatly affects the impedance characteristics of the aluminum electrolytic capacitor. Since the density of the cellulose film is higher than that of the electrolytic paper, the impedance characteristics tend to be deteriorated as compared with the electrolytic paper having the same thickness. However, when the separator is replaced from the electrolytic paper to the cellulose film, since the cellulose film thinner than the electrolytic paper can be used, the distance between the electrodes is shortened. Therefore, the impedance characteristics are improved, and the deterioration due to the density increase can be offset. However, since the impedance characteristic deteriorates in a quadratic function as the thickness of the cellulose film increases, the thickness that can be used as a separator is 20 μm or less.

  On the other hand, since the mechanical strength is remarkably reduced in a cellulose film having a thickness of less than 3 μm, problems occur in the manufacturing process, such as fracture in the film manufacturing process and the aluminum electrolytic capacitor element manufacturing process. Further, it is weak against burrs on the anode aluminum foil and the cathode aluminum foil, and it is difficult to use as a separator because of its low short-circuit resistance.

  The cellulose film thus obtained is used as a separator to be interposed between an anode aluminum foil and a cathode aluminum foil, and wound to produce a capacitor element. The capacitor element is immersed in a liquid electrolyte solution to obtain an electrolyte. After impregnating and placing in a case, it is sealed and aged to produce an aluminum electrolytic capacitor that is reduced in size and / or increased in capacity.

[Measurement method and evaluation method of separator characteristics]
The measurement method and evaluation method of each experimental result as a separator described in each example, comparative example, and conventional example are as follows.

  The thickness, density, tensile strength, and chlorine content were determined in accordance with the test method of JIS C 2300 [electrical cellulose paper]. In the measurement of the thickness, 10 samples were stacked and the thickness was measured at three or more points using an automatic stop type outside micrometer, and the average value per sheet was calculated. In the measurement of the density, the measurement was performed according to the B method (method for obtaining the density in the absolutely dry state). In the measurement of the chlorine content, the manufactured extract was measured according to 17.2.4.2 ion chromatographic method according to the 5th method of 2.1.2.4.2 extraction. The sulfate content was also measured using the same method as the chlorine content.

[Production method of aluminum electrolytic capacitor]
A capacitor element is manufactured by winding a separator so that the anode aluminum foil and the cathode aluminum foil subjected to the etching process and the oxide film formation process do not come into contact with each other. After putting in, an aluminum electrolytic capacitor having a diameter of 10 mm, a height of 20 mm, and a rated voltage of 160 WV or 450 WV was manufactured.

[Defect rate after capacitor aging]
About 1000 capacitor samples, aging was performed by gradually increasing the pressure to about 110% of the rated voltage. The defective rate was determined by dividing the number of defective capacitors including abnormal appearance such as aging short, explosion-proof valve operation, liquid leakage, and swelling of the sealing portion by 1000.

[Capacitance of aluminum electrolytic capacitor]
The capacitance of the electrolytic capacitor was measured using an LCR meter at a frequency of 20 ° C. and 120 Hz.
[Impedance of aluminum electrolytic capacitor]
The impedance of the electrolytic capacitor was measured using an LCR meter at a frequency of 20 ° C. and 1 kHz.

[Example 1]
150 g of TCF dissolving pulp having a polymerization degree of 600 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 78 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 2.2% by weight of cellulose, 71.9% by weight of NMMO, and 25.9% by weight of water.

  This cellulose / NMMO solution was extruded using a T-die type extruder with a slit width of 0.25 mm, passed through an air gap of 10 mm, and then immersed in a coagulation bath of 20% by weight of NMMO in a poor solvent. Played.

  The regenerated cellulose was washed with 3 baths of ion-exchanged water, and then dried with a drum dryer to produce a cellulose film. The obtained cellulose film had a thickness of 3.1 μm, a chlorine content of 1.1 ppm, a sulfate content of 5.1 ppm, and a tensile strength of 9.8 N / 15 mm.

[Example 2]
150 g of TCF cotton linter pulp having a polymerization degree of 1500 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 105 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 2.9% by weight of cellulose, 94.7% by weight of NMMO, and 2.4% by weight of water.

  This cellulose / NMMO solution was extruded using a T-die type extruder with a slit width of 0.50 mm, passed through an air gap of 10 mm, and then immersed in a coagulation bath of ion-exchanged water to regenerate the cellulose. Thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 7.9 μm, a chlorine content of 1.5 ppm, a sulfate content of 3.3 ppm, and a tensile strength of 21.6 N / 15 mm.

Example 3
1300 g of a TCF dissolving pulp having a polymerization degree of 600 having a sulfate content of 195 ppm was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 120 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 19.8% by weight of cellulose, 74.6% by weight of NMMO, and 5.6% by weight of water.
This cellulose / NMMO solution was extruded with a slit width of 0.15 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 2. The obtained cellulose film had a thickness of 13.8 μm, a chlorine content of 0.6 ppm, a sulfate content of 9.5 ppm, and a tensile strength of 37.2 N / 15 mm.

Example 4
600 g of TCF dissolving pulp having a polymerization degree of 600 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 95 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 9.8% by weight of cellulose, 80.0% by weight of NMMO, and 10.2% by weight of water.
This cellulose / NMMO solution was extruded with a slit width of 0.30 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 17.3 μm, a chlorine content of 1.8 ppm, a sulfate content of 5.9 ppm, and a tensile strength of 46.1 N / 15 mm.

Example 5
600 g of TCF cotton linter pulp having a polymerization degree of 1500 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring this mixed liquid of pulp and NMMO, the temperature was raised to 110 ° C., and the water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 10.5% by weight of cellulose, 85.8% by weight of NMMO, and 3.8% by weight of water.
This cellulose / NMMO solution was extruded with a slit width of 0.35 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 19.7 μm, a chlorine content of 1.2 ppm, a sulfate content of 6.7 ppm, and a tensile strength of 51.9 N / 15 mm.

[Comparative Example 1]
150 g of TCF dissolving pulp having a polymerization degree of 600 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 95 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 2.7% by weight of cellulose, 88.2% by weight of NMMO, and 9.1% by weight of water.
This cellulose / NMMO solution was extruded with a slit width of 0.15 mm using a T-die type extruder, and a cellulose film was prepared in the same manner as in Example 1. The obtained cellulose film had a thickness of 2.3 μm, a chlorine content of 0.5 ppm, a sulfate content of 4.8 ppm, and a tensile strength of 3.7 N / 15 mm.

[Comparative Example 2]
600 g of TCF dissolving pulp having a polymerization degree of 600 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring this mixed liquid of pulp and NMMO, the temperature was raised to 110 ° C., and the water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 10.4% by weight of cellulose, 84.9% by weight of NMMO, and 4.7% by weight of water.
This cellulose / NMMO solution was extruded with a slit width of 0.40 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 22.0 μm, a chlorine content of 0.8 ppm, a sulfate content of 5.5 ppm, and a tensile strength of 57.8 N / 15 mm.

[Comparative Example 3]
600 g of a TCF dissolving pulp having a polymerization degree of 650 having a sulfate content of 250 ppm was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring the mixed liquid of this pulp and NMMO, the temperature was raised to 120 ° C., and water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 10.2% by weight of cellulose, 83.3% by weight of NMMO, and 6.5% by weight of water.

  This cellulose / NMMO solution was extruded with a slit width of 0.30 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 14.8 μm, a chlorine content of 1.1 ppm, a sulfate content of 12.3 ppm, and a tensile strength of 23.5 N / 15 mm.

[Comparative Example 4]
600 g of ECF dissolving pulp having a polymerization degree of 600 was added to 7000 g of a 70% by weight NMMO aqueous solution. While stirring this mixed liquid of pulp and NMMO, the temperature was raised to 100 ° C., and the water was evaporated to obtain a cellulose / NMMO solution. The composition of the solution was 9.8% by weight of cellulose, 80.0% by weight of NMMO, and 10.2% by weight of water.

  This cellulose / NMMO solution was extruded with a slit width of 0.30 mm using a T-die type extruder, and thereafter, a cellulose film was produced in the same manner as in Example 1. The obtained cellulose film had a thickness of 15.1 μm, a chlorine content of 2.3 ppm, a sulfate content of 5.8 ppm, and a tensile strength of 22.5 N / 15 mm.

[Comparative Example 5]
When the physical properties of the cellulose film produced by the viscose method using the dissolving pulp were evaluated, the thickness was 15.5 μm, the chlorine content was 122 ppm, the sulfate content was 512 ppm, and the tensile strength was 32.3 N / 15 mm. there were.

[Comparative Example 6]
The physical properties of a commercially available polypropylene (PP) film were evaluated. The thickness was 14.3 μm, the chlorine content was 0.2 ppm, the sulfate content was 0.1 ppm, and the tensile strength was 28.4 N / 15 mm. .

[Comparative Example 7]
When the physical properties of a cellulose film prepared by the viscose method using cotton linter pulp were evaluated, the thickness was 18.8 μm, the chlorine content was 126 ppm, the sulfate content was 485 ppm, and the tensile strength was 30.4 N / 15 mm. Met.

[Conventional example 1]
The raw material, which was beaten unbleached softwood kraft pulp to a CSF of 5 ml or less with a beating machine, was made with a long net paper machine to produce a single long net with a thickness of 10.1 μm and a density of 0.83 g / cm ³ . The obtained long net single paper had a chlorine content of 0.3 ppm, a sulfate content of 3.8 ppm, and a tensile strength of 16.7 N / 15 mm.

[Conventional example 2]
The raw material obtained by beating unbleached softwood kraft pulp with a beater to a CSF of 5 ml or less was made with a long paper machine to produce a single long paper sheet having a thickness of 15.0 μm and a density of 0.85 g / cm ³ . The obtained long net single paper had a chlorine content of 0.2 ppm, a sulfate content of 4.2 ppm, and a tensile strength of 26.5 N / 15 mm.

[Conventional example 3]
A material obtained by beating softwood kraft pulp until CSF5ml following beater and paper stock of fourdrinier, thickness 20.1Myuemu, while paper density paper density 0.85 g / cm ³ at Fourdrinier part, round net portion in thickness the raw material beaten softwood kraft pulp CSF400ml 20.1μm, combined paper making and paper making paper of density 0.61 g / cm ^3, the total thickness 40.2Myuemu, the overall density of 0.75 g / cm ³ A long-mesh double mesh paper was produced. The obtained long web double paper had a chlorine content of 0.5 ppm, a sulfate content of 5.4 ppm, and a tensile strength of 66.6 N / 15 mm.

[Conventional Example 4]
The raw material, which was beaten unbleached softwood kraft pulp to a CSF of 5 ml or less with a beater, was made with a long net paper machine to produce a single long net with a thickness of 20.1 μm and a density of 0.86 g / cm ³ . The obtained long net single paper had a chlorine content of 0.6 ppm, a sulfate content of 4.7 ppm, and a tensile strength of 34.3 N / 15 mm.

[Conventional Example 5]
Conveying softwood kraft pulp to a CSF of 5 ml or less with a beating machine is used as a papermaking raw material for a long net, and while making high density paper with a thickness of 25.2 μm and a density of 0.85 g / cm ^{3 on} the long net, in thickness the raw material beaten softwood kraft pulp CSF400ml 34.8μm, combined paper making and paper making paper of density 0.67 g / cm ^3, the total thickness 60.0, the overall density of 0.75 g / cm ³ A long-mesh double mesh paper was produced. The obtained long web double paper had a chlorine content of 0.5 ppm, a sulfate content of 6.1 ppm, and a tensile strength of 110.7 N / 15 mm.

  Using the cellulose film obtained in Examples 1 to 5, the cellulose film obtained in Comparative Examples 1 to 6, the PP film, and the electrolytic paper obtained in Conventional Examples 1 to 3, 1000 160 WV aluminum electrolytic capacitors were manufactured, The defect rate was measured, and the impedance and capacitance were measured.

Table 1 shows the physical properties of the cellulose films obtained in Examples 1 to 5, the cellulose film PP film obtained in Comparative Examples 1 to 6 and the electrolytic paper obtained in Conventional Examples 1 to 3, and the evaluation results of the aluminum electrolytic capacitors. Table 1 is a table showing a list of characteristic measurement results of each example, comparative example, and conventional example.

  When the 2.3 μm-thick cellulose film obtained in Comparative Example 1 was used, the cellulose film was frequently broken in the aluminum electrolytic capacitor element manufacturing process, and the aluminum electrolytic capacitor could not be manufactured. It is considered that the tensile strength value was as small as 3.7 N / 15 mm, so that it could not withstand the winding tension in the element manufacturing process.

  When the PP film of Comparative Example 6 was used, the PP film could not hold the electrolytic solution and did not function as an aluminum electrolytic capacitor.

  FIG. 1 shows the measurement results of the defect rate of a 160 WV aluminum electrolytic capacitor using the cellulose films obtained in Examples 1 to 5, the cellulose films obtained in Comparative Examples 2 to 5 and the electrolytic paper obtained in Conventional Examples 1 to 3. Show. FIG. 1 is a plot showing the relationship between the thickness of a separator of an aluminum electrolytic capacitor of 160 WV and the defect rate after aging.

  As shown in FIG. 1, in a 160 WV aluminum electrolytic capacitor, a 13.8 μm-thick cellulose film obtained in Example 3, a 17.3 μm-thick cellulose film obtained in Example 4, and Example 5 The defective rates of the aluminum electrolytic capacitors using the cellulose film obtained with the obtained thickness of 19.7 μm were all 0%. The defective rate of the aluminum electrolytic capacitor using the 7.9 μm-thick cellulose film obtained in Example 2 is 0.8%, and the aluminum electrolysis using the 3.1 μm-thick cellulose film obtained in Example 1 is used. The defective rate of the capacitor was 2.3%. The defective rate of the aluminum electrolytic capacitor using the cellulose film having a thickness of 22.0 μm obtained in Comparative Example 2 was 0%.

  The defective rate of the aluminum electrolytic capacitor using the long-mesh circular double-ply paper having a thickness of 40.2 μm obtained in Conventional Example 3 which is generally used as a separator for 160 WV aluminum electrolytic capacitor was 0%. Defect rate of aluminum electrolytic capacitor using 10.1 μm thick long net single paper obtained in Conventional Example 1 and aluminum electrolytic capacitor using 15.0 μm thick long net single paper obtained in Conventional Example 2 Were 54.8% and 19.2%, respectively, and the defect rate was significantly higher than that of a cellulose film having the same thickness. Since the cellulose film is uniform and dense, it has high short-circuit resistance compared to electrolytic paper having the same thickness. Therefore, a cellulose film having a thickness that cannot be used with electrolytic paper can be used as a separator.

  The defective rate of the aluminum electrolytic capacitor using the cellulose film having a sulfate content of 12.3 ppm obtained in Comparative Example 3 was 45.1%. The defective rate of the aluminum electrolytic capacitor using the cellulose film having a chlorine content of 2.3 ppm obtained in Comparative Example 4 was 84.6%. The cellulose film usable as a separator for an aluminum electrolytic capacitor has a chlorine content and a sulfate content of 2 ppm or less and 10 ppm or less, respectively.

  In addition, the cellulose film produced by the viscose method of Comparative Example 5 had a large chlorine content and sulfate content, and the defect rate of an aluminum electrolytic capacitor using this cellulose film as a separator was 100%. Aluminum electrolytic capacitors are not suitable.

  160 WV using the cellulose film obtained in Examples 1 to 5, the cellulose film obtained in Comparative Example 2, and the electrolytic paper obtained in Conventional Example 3 in which the defective rate after aging of the aluminum electrolytic capacitor was 3.0% or less The measurement result of the electrostatic capacity of the aluminum electrolytic capacitor is shown in FIG. FIG. 2 is a plot showing an extracted relationship between the separator thickness of the 160 WV aluminum electrolytic capacitor and the capacitance of the aluminum electrolytic capacitor.

  As the separator becomes thinner, the area of the anode aluminum foil can be increased in an element of the same size, so that the capacitance of the aluminum electrolytic capacitor increases. As shown in FIG. 2, the capacitance of the aluminum electrolytic capacitor using the long-mesh circular double paper having a thickness of 40.2 μm obtained in Conventional Example 3 was 33.0 μF. The capacitance of the aluminum electrolytic capacitor using the obtained 3.1 μm thick cellulose film was 47.7 μF, and the improvement rate of the capacitance was 44.4%.

  The capacitance of the aluminum electrolytic capacitor using the 13.8 μm-thick cellulose film obtained in Example 3 was 42.3 μF, and the long net-type double-net network having the thickness of 40.2 μm obtained in Conventional Example 3 was obtained. Compared with the aluminum electrolytic capacitor using paper, the capacitance was improved by 28.2%. The defect rates of the aluminum electrolytic capacitor using the long-mesh round net double paper obtained in Conventional Example 3 and the aluminum electrolytic capacitor using the cellulose film obtained in Example 3 are both 0%. By using the cellulose film of the present invention, the capacitance of the aluminum electrolytic capacitor can be improved without increasing the defective rate of the aluminum electrolytic capacitor.

  160 WV using the cellulose film obtained in Examples 1 to 5, the cellulose film obtained in Comparative Example 2, and the electrolytic paper obtained in Conventional Example 3 in which the defective rate after aging of the aluminum electrolytic capacitor was 3.0% or less The measurement result of the impedance characteristic (1 kHz) of the aluminum electrolytic capacitor is shown in FIG. FIG. 3 is a plot showing an extracted relationship between the thickness of the separator of the 160 WV aluminum electrolytic capacitor and the impedance characteristic (1 kHz) of the aluminum electrolytic capacitor.

  As shown in FIG. 3, the impedance at 1 kHz of the aluminum electrolytic capacitors using the cellulose films obtained in Examples 1 to 5 is 2.55Ω, 2.91Ω, 3.89Ω, 4.82Ω, and 5.84Ω, respectively. However, the impedance at 1 kHz of the aluminum electrolytic capacitor using the cellulose film having a thickness of 22.0 μm obtained in Comparative Example 2 was 9.83Ω. When the thickness of the cellulose film is increased, the impedance characteristics of the aluminum electrolytic capacitor deteriorate in a quadratic function. Therefore, the thickness of the cellulose film that can be practically used as a separator is 20 μm or less.

  For thicknesses of 20 μm or less where the rate of deterioration of impedance is small, the distance between the electrodes can be shortened because a cellulose film thinner than electrolytic paper can be used, so that the impedance characteristics at 1 kHz are improved, and the deterioration due to density increase is offset. Can do. In addition, when an element of the same size is manufactured, the impedance reduction effect due to the increase in capacity also occurs, so the impedance of the aluminum electrolytic capacitor may be lower when using a thin cellulose film than when using thick electrolytic paper. .

  Using the cellulose film obtained in Examples 3 to 5, the cellulose film obtained in Comparative Example 7 and the electrolytic paper obtained in Conventional Examples 4 to 5, 1000 450 WV aluminum electrolytic capacitors were produced, and the defect rate was similarly obtained. Measure and measure capacitance and impedance.

Table 2 shows the physical properties of the cellulose films obtained in Examples 3 to 5, the cellulose film obtained in Comparative Example 7, and the electrolytic paper obtained in Conventional Examples 4 to 5 and the evaluation results of the aluminum electrolytic capacitors. Table 2 is a table showing a list of characteristic measurement results of each example, comparative example, and conventional example.

  FIG. 4 shows the measurement results of the defective rate of 450 WV aluminum electrolytic capacitors using the cellulose films obtained in Examples 3 to 5, the cellulose film obtained in Comparative Example 7, and the electrolytic paper obtained in Conventional Examples 4 to 5. FIG. 4 is a plot diagram showing the relationship between the separator thickness of the 450 WV aluminum electrolytic capacitor and the impedance characteristics of the aluminum electrolytic capacitor.

  As shown in FIG. 4, the defective rate of the aluminum electrolytic capacitor using the 60.0 μm-thick long net double paper obtained in the conventional example 5 that is generally used as a separator for a 450 WV aluminum electrolytic capacitor. Was 0%. The defective rate of the aluminum electrolytic capacitor using the 19.7 μm-thick cellulose film obtained in Example 5 was 0%, but the 20.1 μm-thick long net single paper obtained in Conventional Example 4 was used. The defective rate of the aluminum electrolytic capacitor used was 35.7%.

  A 450 WV aluminum electrolytic capacitor separator is required to have extremely excellent short-circuit resistance. When electrolytic paper is used, it is necessary to secure a distance between the electrodes with a thick electrolytic paper as in Conventional Example 5 in order to completely separate the anode aluminum foil and the cathode aluminum foil, but the cellulose film is dense and uniform. Therefore, a separator having a thickness of 20 μm or less can be used.

  In addition, the cellulose film of the comparative example 7 had many chlorine content and sulfate content, and the defective rate of the aluminum electrolytic capacitor which used this cellulose film as a separator was 100%.

  The capacitance of a 450 WV aluminum electrolytic capacitor using the cellulose film obtained in Examples 3 to 5 and the electrolytic paper obtained in Conventional Example 5 in which the defective rate after aging of the aluminum electrolytic capacitor was 3.0% or less. The measurement results are shown in FIG. FIG. 5 is a plot showing an extracted relationship between the separator thickness of the 450 WV aluminum electrolytic capacitor and the capacitance of the aluminum electrolytic capacitor.

  As shown in FIG. 5, the electrostatic capacity of the aluminum electrolytic capacitor using the cellulose film obtained in Examples 3 to 5 is the same as that of the aluminum using the long-mesh circular double paper obtained in the conventional example 5. They increased by 48.9%, 44.7%, and 40.4%, respectively, compared with the capacitance of the electrolytic capacitor.

  Impedance characteristics (1 kHz) of a 450 WV aluminum electrolytic capacitor using the cellulose film obtained in Examples 3 to 5 and the electrolytic paper obtained in Conventional Example 5 in which the defective rate after aging of the aluminum electrolytic capacitor was 3.0% or less The measurement results of) are shown in FIG. FIG. 6 is a plot showing the relationship between the separator thickness of the 45 WV aluminum electrolytic capacitor and the impedance characteristic (1 kHz) of the aluminum electrolytic capacitor.

  As shown in FIG. 6, the relationship between the thickness of the separator and the impedance of the aluminum electrolytic capacitor at 1 kHz is plotted for a 450 WV aluminum electrolytic capacitor. The impedance of the aluminum electrolytic capacitor using the cellulose film of Example 3 is 24.09Ω, the impedance of the aluminum electrolytic capacitor using the cellulose film of Example 4 is 30.37Ω, and the aluminum electrolytic capacitor using the cellulose film of Example 5 The impedance of was 38.43Ω. The impedance of the aluminum electrolytic capacitor using the long-mesh circular double paper of Conventional Example 5 was 39.57Ω. Even in a 450 WV aluminum electrolytic capacitor, it can be estimated that when the thickness of the cellulose film is greater than 20 μm, the impedance characteristics tend to deteriorate greatly.

  As is clear from the present embodiment and examples, it is possible to provide a film in which cellulose is regenerated by dissolving the cellulose base material and separating the cellulose to the molecular chain level and then regenerating the cellulose. Film can be produced. Further, since this film does not have voids unlike high-density electrolytic paper, it is possible to further increase the density compared to electrolytic paper. Therefore, when compared with electrolytic paper having the same thickness, the denseness, uniformity and density are improved, so that the short-circuit resistance is greatly improved.

  In addition, the cellulose film produced using the amine oxide cellulose solution does not contain impurities that corrode the anodic oxide film of the aluminum electrolytic capacitor. Furthermore, by using cellulose that is TCF bleached or unbleached and has a sulfate content of 200 ppm or less as the dissolving cellulose, the chlorine content that can be used as a separator for an aluminum electrolytic capacitor is 2 ppm or less and the sulfate content is 10 ppm or less. A cellulose film can be obtained.

  When producing a cellulose film from an amine oxide-based cellulose solution, no chemical reaction is involved, so no gas is generated unlike the viscose method, and no bubbles are contained in the film. Therefore, even a thin cellulose film does not have pinholes, and short circuit resistance can be ensured.

  Since the cellulose film according to the embodiment of the present invention is uniform and dense, it has higher short-circuit resistance than electrolytic paper having the same thickness, and short-circuit resistance can be ensured even if the thickness is reduced. For this reason, the capacitor manufactured using the cellulose film according to the embodiment of the present invention thinner than the conventional electrolytic paper has a short circuit resistance equal to or higher than that of the conventional electrolytic paper capacitor and low impedance. To realize. That is, by using a cellulose film having a thickness of 20 μm or less as a separator for an aluminum electrolytic capacitor, it is possible to reduce the size and / or increase the capacity without deteriorating the impedance characteristics of the aluminum electrolytic capacitor.

  Furthermore, since a cellulose film having a thickness of 10 μm or less, which is the limit thickness of electrolytic paper, has sufficient short-circuit resistance, the conventional electrolytic paper can be used as a separator by using this cellulose film as a separator for an aluminum electrolytic capacitor. As a result, it is possible to further reduce the size and / or increase the capacity of an aluminum electrolytic capacitor that could not be realized when used as a capacitor.

Claims (7)

A separator for an electrolytic capacitor, which is a film using cellulose as a raw material. A film using cellulose as a raw material is formed into a film form of a cellulose solution in which cellulose is dissolved in an amine oxide solvent, and the cellulose is coagulated and regenerated by immersing in water or a poor solvent of an amine oxide solvent. The separator for an electrolytic capacitor according to claim 1, which is a cellulose film obtained by washing the regenerated cellulose with water to remove the amine oxide solvent and then drying. 3. The separator for an electrolytic capacitor according to claim 2, wherein the amine oxide solvent is N-methylmorpholine-N-oxide. 4. The electrolytic capacitor separator according to claim 1, wherein the film has a thickness of 3 to 20 [mu] m. The separator for an electrolytic capacitor according to any one of claims 1 to 4, wherein the film has a chlorine content of 2 ppm or less. The separator for an electrolytic capacitor according to any one of claims 1 to 5, wherein a sulfate content of the film is 10 ppm or less. An electrolytic capacitor comprising the separator according to claim 1 interposed between an anode foil and a cathode foil.

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