JP2012200638A - Deionization electrode for water flow-through capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve water purification performance while maintaining electrode strength.SOLUTION: A deionization electrode for a water flow-through capacitor is made of an electrode composition containing activated carbon, a conductive material, a binding agent, and a metal oxide having an average primary particle size of 0.05-1.0 μm.

Description

  The present invention relates to a deionization electrode used for a flowing water passing type capacitor for purifying water.

  There are many known methods for reducing ionic pollutants in purifying water such as polluted water. For example, filtration methods such as filtration membranes and reverse osmotic pressure, ion exchange, resin bed absorption, and the like have been put into practical use. However, these methods require regeneration of a deionized layer such as a filter or an ion exchange membrane. Since harmful chemical substances are used for regeneration, there are concerns about adverse environmental impacts.

  As a technique capable of reducing the environmental load, a deionization technique using a flowing water passing capacitor capable of electrically regenerating the deionization layer has been attracting attention (see Patent Documents 1 and 2). In this technique, deionization and regeneration can be performed by repeatedly charging and discharging, so that it is not necessary to use harmful chemical substances. As a deionization electrode used for such a flowing water capacitor, Patent Document 1 describes an electrode using an electrode containing activated carbon and a binder.

International Publication No. WO2009 / 062872 JP 2009-190016 A

  However, according to the study of the present inventor, since the flowing water type capacitor electrode described in Patent Document 1 is made of a hydrophobic material, the water content (water penetration) is poor, and deionization is performed. In some cases, sex was not sufficient. Moreover, although water content can be improved by reducing the amount of binders, the strength of the electrode may be insufficient.

  This invention is made | formed in view of such a point, and it aims at improving the purification | cleaning performance of water, maintaining an electrode intensity | strength.

  The deionized electrode for flowing water type capacitors according to the present invention is formed from an electrode composition containing activated carbon, a conductive material, a binder, and a metal oxide having an average primary particle size of 0.05 μm to 1.0 μm.

  In the deionization electrode for flowing water type capacitor according to the present invention, titanium oxide can be used as the metal oxide. In this case, anatase (anatase) type titanium oxide can be used as the titanium oxide.

  According to the present invention, since the electrode is formed from the electrode composition containing a metal oxide having an average primary particle size of 0.05 μm to 1.0 μm, sterilization and water content can be achieved without significantly reducing the electrode strength. Therefore, there is an effect that the water purification performance can be improved while maintaining the electrode strength.

  Hereinafter, the deionization electrode for flowing water type capacitors according to the embodiment of the present invention will be specifically described. The deionization electrode for flowing water type capacitors according to the present embodiment contains activated carbon, an electrically conductive material, a binder (binder), and a metal oxide having an average primary particle size of 0.05 μm to 1.0 μm as an electrode active material. It is formed from an electrode composition (electrode material). This deionized electrode is used as an electrode layer, which is formed of only an electrode layer or laminated on a current collector.

<Electrode composition>
The electrode composition of the present embodiment contains at least an electrode active material (activated carbon), a conductive material, a binder (binder), and a metal oxide.

(Electrode active material)
As the electrode active material, activated carbon powder is used. Specific examples thereof include activated carbon powder made from phenol resin, rayon, acrylonitrile resin, pitch, coconut shell, and the like.

  The volume average particle diameter of the electrode active material is usually 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 5 to 20 μm. These electrode active materials can be used alone or in combination of two or more.

The specific surface area of the electrode active material, ^{30 m} 2 / g or more, preferably preferably 500~5,000m ² / g, more preferably 1,000~3,000m ² / g. Since the density of the obtained electrode active material layer tends to decrease as the specific surface area of the electrode active material increases, an electrode layer having a desired density can be obtained by appropriately selecting the electrode active material.

  The shape of the electrode active material is preferably a granulated one. When the shape of the particles is spherical, a higher density electrode can be formed during electrode molding.

(Conductive material)
As the conductive material, powder of carbon black, natural graphite, artificial graphite or the like is used. Of these, ketjen black or acetylene black, which is a kind of carbon black, is preferably used since the effect of improving conductivity is large even in a small amount.

  The volume average particle diameter of the conductive material is preferably smaller than the volume average particle diameter of the electrode active material, and the range is usually 0.001 to 10 μm, preferably 0.05 to 5 μm, more preferably 0.01 to 1 μm. It is. When the volume average particle diameter of the conductive material is within this range, high conductivity can be obtained with a smaller amount of use. These conductive materials can be used alone or in combination of two or more.

  The amount of the conductive material is preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When the amount of the conductive material is within this range, the internal resistance of the obtained electrode can be lowered.

(Binder)
When the electrode is formed from a slurry, examples of the binder mixed with the slurry include polymer compounds such as halogen polymers, diene polymers, acrylate polymers, polyimides, polyamides, and polyurethanes. These binders can be used alone or in combination of two or more.

  The halogen-based polymer is a polymer containing a monomer unit containing a halogen atom. Of the halogen atoms, a fluorine polymer or a chlorine polymer containing a fluorine atom or a chlorine atom is preferred. Specific examples of the fluorine-based polymer and the chlorine-based polymer include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoro. Examples thereof include ethylene copolymers, perfluoroethylene / propene copolymers, chlorosulfonated polyethylene, and polychloroprene.

  The diene polymer is a homopolymer of a conjugated diene or a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene, or a hydrogenated product thereof. Specific examples of the diene polymer include conjugated diene homopolymers such as polybutadiene, polyisoprene and polychloroprene; conjugated diene copolymers such as butyl rubber; carboxy-modified styrene / butadiene copolymers (SBR) ), Etc .; vinyl cyanide / conjugated diene copolymers such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

  An acrylate polymer is a copolymer obtained by polymerizing a homopolymer of an acrylic ester or a methacrylic ester or a monomer mixture containing these.

  Among the above, the binder is preferably a halogen polymer or a diene polymer from the viewpoint of obtaining an active material layer excellent in bondability and strength with a current collector and acid resistance. More preferably, polytetrafluoroethylene, polychloroprene, chlorosulfonated polyethylene, and SBR are used.

  The shape of the binder is not particularly limited, but is preferably in the form of particles because it has good bondability with the current collector and can suppress deterioration in water purification performance and deterioration due to repeated use. Examples of the particulate binder include those in which binder particles such as latex are dispersed in water, and powders obtained by drying such a dispersion.

  The glass transition temperature (Tg) of the binder is preferably 50 ° C. or lower, more preferably −40 to 0 ° C. When the glass transition temperature (Tg) of the binder is within this range, it is excellent in binding property with a small amount of use, strong in electrode strength, rich in flexibility, and facilitates the electrode density by a pressing process at the time of electrode formation. Can be increased.

  When the binder is particulate, the number average particle size is not particularly limited, but is usually 0.0001 to 100 μm, preferably 0.001 to 10 μm, more preferably 0.01 to 1 μm. . When the number average particle diameter of the binder is within this range, an excellent binding force can be imparted to the electrode layer even with a small amount of use. Here, the number average particle diameter is a number average particle diameter calculated as an arithmetic average value obtained by measuring the diameter of 100 binder particles randomly selected in a transmission electron micrograph. The shape of the particles can be either spherical or irregular. These binders can be used alone or in combination of two or more.

  The amount of the binder is preferably 0.5 to 20 parts by weight, more preferably 1.0 to 15 parts by weight with respect to 100 parts by weight of the electrode active material. If the amount of the binder is less than 0.5 parts by weight, the electrode strength may be insufficient, and if it exceeds 20 parts by weight, the water content is deteriorated. In addition, the water content can be sufficient.

(Metal oxide)
The metal oxide fine particles used in the present invention have a radical generating function and do not function as an electrode active material. By containing metal oxide fine particles having a radical generating function in the electrode layer, it is possible to oxidatively decompose harmful organic compounds in water.

Examples of such metal oxides include titanium oxide (TiO ₂ ), niobium oxide (Nb ₂ O ₅ ), tungsten oxide (WO ₃ ), tin oxide (SnO ₂ ), strontium titanate (SrTiO ₃ ), zirconium oxide ( Examples thereof include metal oxides selected from the group consisting of ZrO ₂ ), zinc oxide (ZnO), bismuth oxide (Bi ₂ O ₃ ), and silicon oxide (SiO ₂ ). Among these, it is preferable to use a metal oxide selected from the group consisting of titanium oxide, zinc oxide, niobium oxide, tungsten oxide, tin oxide and strontium titanate because it has little influence on the characteristics of the capacitor. It is particularly preferable to use Further, among titanium oxides, those having an anatase type crystal structure are particularly preferable because of excellent radical generating function.

  In the present invention, these metal oxide fine particles may be used alone or in combination of two or more.

  The amount of the metal oxide is preferably 5 to 35 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the electrode active material. If the amount of the metal oxide is less than 5 parts by weight, sterilization and water content may be insufficient, and if it exceeds 35 parts by weight, the electrode strength becomes weak and the pores in the electrode decrease (the ratio of the activated carbon is reduced). The ion-capturing ability deteriorates.

  The particle size of the metal oxide is an average primary particle size (volume average), preferably 0.05 to 1.0 μm, more preferably 0.07 to 0.9 μm, and still more preferably 0.1 to 0.8 μm. It is a range. When the average primary particle size of the metal oxide is less than 0.05 μm, the electrode strength becomes weak and the surface area becomes too large and the water content may deteriorate. When the average primary particle size exceeds 1.0 μm, the surface area decreases and sterilization deteriorates. Therefore, within this range, the strength of the electrode can be maintained, and the water content and sterility can be sufficient.

  The average primary particle size of the metal oxide is determined by adding a sample powder to water using a particle size measuring device (for example, SALD2000J, manufactured by Shimadzu Corporation) using a laser diffraction scattering method, and using an ultrasonic cleaner. After being well dispersed for 3 minutes, the volume-based cumulative particle size distribution is measured to obtain a particle size corresponding to a cumulative value of 50%.

(Surfactant, organic solvent)
In addition to the electrode active material (activated carbon), the conductive material, the binder, and the metal oxide, the electrode composition may include a surfactant and / or an organic solvent having a boiling point within a specific range. Either one or both of the surfactant and the organic solvent may be contained.

  When using a surfactant, the blending amount is in the range of 0.5 to 20 parts by weight, preferably 1.0 to 10 parts by weight, and 2.0 to 5 parts per 100 parts by weight of the electrode active material. Part by weight is particularly preferred. When the blending amount of the surfactant is within this range, the durability is excellent.

  When using an organic solvent, the compounding quantity is the range of 0.5-20 weight part with respect to 100 weight part of electrode active materials, 1.0-10 weight part is preferable, 2.0-5 weight Part is particularly preferred. When the amount of the organic solvent is within this range, the durability is excellent.

  Further, it is particularly preferable to use the above surfactant and an organic solvent in combination. By using the surfactant and the organic solvent in combination, the surface tension of the electrode composition slurry is further reduced, and the productivity is improved. In this case, the total amount of the surfactant and the organic solvent is in the range of 0.5 to 20 parts by weight, preferably 1.0 to 10 parts by weight, with respect to 100 parts by weight of the electrode active material. ˜5 parts by weight is particularly preferred.

(Dispersant)
In addition to the electrode active material (activated carbon), the conductive material, the binder, and the metal oxide, the electrode composition may contain a dispersant in order to uniformly disperse these components.

  Specific examples of the dispersant include cellulose dielectrics such as carboxymethyl cellulose; poly (meth) acrylates such as sodium poly (meth) acrylate; polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide; polyvinylpyrrolidone, polycarboxylic acid, Examples thereof include oxidized starch, phosphate starch, casein, various modified starches, chitin, and chitosan derivatives. Among these, cellulose derivatives are particularly preferable.

  The cellulose derivative is a compound obtained by etherifying or esterifying at least a part of the hydroxyl group of cellulose, and is preferably water-soluble. Cellulose derivatives usually do not have a glass transition point. Specific examples include carboxymethyl cellulose, carboxymethyl ethyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Moreover, these ammonium salt and alkali metal salt are mentioned. Among these, a salt of carboxymethyl cellulose is preferable, and an ammonium salt of carboxymethyl cellulose is particularly preferable. The degree of etherification of the cellulose derivative is preferably 0.5 to 2, more preferably 0.5 to 1.5. Here, the degree of etherification is a value representing how many hydroxyl groups contained per 3 glucose units of cellulose are etherified on average. When the degree of etherification is in this range, the stability of the slurry containing the electrode composition is high, and solid matter does not easily settle or aggregate. Furthermore, the coating property and fluidity | liquidity of a coating material improve by using a cellulose derivative.

  Although the usage-amount of these dispersing agents is not specifically limited, Usually, 0.1-10 weight part with respect to 100 weight part of electrode active materials, Preferably it is 0.5-5 weight part, More preferably, it is 0.8. It is in the range of ˜2 parts by weight.

<Current collector>
As the type of material constituting the current collector, for example, metal, carbon, conductive polymer, and the like can be used, and metal is preferably used. For example, various materials proposed for applications such as batteries and capacitors can be used, and stainless steel, titanium, aluminum, copper, nickel, and the like can be used for the current collector.

  Although the thickness of a collector is not specifically limited, Although it is about 5-100 micrometers in thickness and a magnitude | size and a shape are not specifically limited, For example, it can be set as a disk about 3-30 cm in diameter.

<Formation of electrode>
The method for forming the electrode is not particularly limited. For example, (1) a composition for forming an electrode obtained by kneading activated carbon, a conductive material, a binder, and a metal oxide having an average primary particle size of 0.05 μm to 1.0 μm. (2) Activated carbon, conductive material, binder, average primary particle size 0. The method of forming a sheet with a composition for forming an electrode alone or on a base film or a current collector (kneading sheet forming method); A method of preparing a slurry-like electrode-forming composition comprising a metal oxide of 05 μm to 1.0 μm and a solvent, applying the composition on a base film or a current collector, and drying (wet molding method); (3) Prepare composite particles comprising activated carbon, conductive material, binder, and metal oxide having an average primary particle size of 0.05 μm to 1.0 μm, and use the composite particles alone or base film or current collector Obtained by sheet molding and roll pressing on the body And the like method (dry forming process).

  Although the thickness of the deionization electrode for flowing water capacitors depends on the type of flowing water capacitor used, it is usually 50 to 400 μm, preferably 100 to 350 μm, particularly preferably 150 to 300 μm. When the thickness of the electrode is within this range, the internal resistance and energy density are balanced, which is preferable.

  The electrode manufactured as described above is used as an electrode layer as it is or on a current collector and used in a flowing water type capacitor. Lamination of the electrode to the current collector can be performed, for example, by adhering the electrode to the current collector using a conductive adhesive.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in a present Example are a mass reference | standard. In Examples and Comparative Examples, various physical properties are evaluated as follows.

<Evaluation method>
(Evaluation of sterility)
The sheet-like electrodes obtained in the examples and comparative examples are punched into a circular shape having a diameter of 12 mm. Antibacterial test E. coli and Staphylococcus aureus are suspended in a phosphate buffer to obtain a suspension. Then, 75 mL of the suspension solution and the electrode punched into the circular shape were placed in a 200 mL Erlenmeyer flask, held at 25 ° C. ± 5 ° C., and subjected to vibration treatment at 330 rpm for 1 hour. The number of viable bacteria (the number of E. coli and Staphylococcus aureus) before and after vibration treatment was measured to calculate the sterilization rate, and evaluation was performed according to the following criteria.

Sterilization rate = (viable count before vibration treatment−viable count after vibration treatment) / (viable count before vibration treatment) × 100
A: Sterilization rate is 100%
B: Sterilization rate is 99% or more and less than 100% C: Sterilization rate is 95% or more and less than 99% D: Sterilization rate is less than 95% A to C are evaluated as good and D is evaluated as poor.

(Evaluation of water content in electrodes)
The sheet-like electrodes obtained in the examples and comparative examples are punched into a circular shape having a diameter of 12 mm. Then, 5 μL of a droplet was dropped on the electrode with a micropipette, and the time until the droplet was completely impregnated was measured. The measurement was performed 3 times and the average value was calculated. When the time until the droplets are completely impregnated is 10 minutes or less, it is evaluated as good when it exceeds 10 minutes. The shorter the time until the droplets are completely impregnated, the better the water content.

(Mechanical strength of electrode)
The sheet-like electrodes obtained in the examples and comparative examples were subjected to a tensile test using a dumbbell-shaped test piece at room temperature according to JIS K6251 to measure the breaking strength (MPa). The measurement was performed 3 times, and the average value was calculated. When it is 0.1 MPa or more, it is evaluated as good and when it is less than 0.1 MPa, it is evaluated as defective. Higher breaking strength means higher electrode strength.

(Electrical conductivity)
Two electrodes were punched into a circular shape having a diameter of 12 mm, and placed in a beaker containing 100 mL of tap water (the electric conductivity of tap water was 200 μS / cm) so that they were not in electrical contact. Then, after applying a voltage of 1 V between the electrodes for 1 minute, the electrical conductivity of tap water was measured using an electrical conductivity meter (trade name: ES-12, manufactured by Horiba, Ltd.). If it is 120 μS / cm or less, it is evaluated as good, and if it exceeds 120 μS / cm, it is evaluated as defective. The lower the electric conductivity of tap water after voltage application, the better the water purification performance.

<Example 1>
(Manufacture of electrodes)
100 parts of activated carbon powder (product name: Shirakaba PC manufactured by Nippon Enviro Chemicals), 6.5 parts of acetylene black (product name: Denkapak powder manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and polytetrafluoro as a binder Add 12 parts of ethylene (PTFE) (product name: D-210C, manufactured by Daikin Industries, Ltd.) and 14 parts of anatase-type titanium oxide (product name: A-110, manufactured by Sakai Chemical Co., Ltd.) as a metal oxide. Then, kneading was performed, followed by rolling, followed by heat treatment (120 ° C.) for 15 minutes to obtain a sheet-like electrode having a thickness of 0.3 mm. The average primary particle diameter (D50) of titanium oxide as a metal oxide was 0.2 μm. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation A, which was very good. The water content was 2 minutes (min) and was good. The breaking strength was 0.3 MPa, and sufficient strength was obtained. The electric conductivity was 60 μS / cm, and sufficient purification performance could be realized.

<Example 2>
(Manufacture of electrodes)
Except that the content of titanium oxide was increased to 28 parts compared to Example 1, it was the same as Example 1 described above. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation A, which was very good. The water content was 1 minute (min), which was improved over that of Example 1. The breaking strength was 0.15 MPa, which was lower than that of Example 1, but sufficient strength was obtained. The electric conductivity was 60 μS / cm, and sufficient purification performance could be realized.

<Example 3>
(Manufacture of electrodes)
Except that the content of titanium oxide was further increased from 35 parts as compared with Example 2, it was the same as Example 1 described above. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation B, and although it was lower than that of Example 1 and Example 2, it was good. The water content was 0.5 minutes (min), which could be improved as compared with Example 1 and Example 2. The breaking strength was 0.1 MPa, which was lower than that of Example 1 and Example 2, but almost sufficient strength was obtained. The electric conductivity was 90 μS / cm, which was slightly lower than that of Example 1 and Example 2, but sufficient purification performance could be realized.

<Example 4>
(Manufacture of electrodes)
Example 1 was the same as Example 1 except that the content of titanium oxide was reduced to 8 parts compared to Example 1. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation B, and although it was lower than Example 1, it was good. The water content was 5 minutes (min), which was lower than that of Example 1. The breaking strength was 0.35 MPa, which was higher than that of Example 1 and sufficient strength was obtained. The electric conductivity was 90 μS / cm, which was slightly lower than that of Example 1, but sufficient purification performance could be realized.

<Example 5>
(Manufacture of electrodes)
Except for using 14 parts of anatase-type titanium oxide (product name: TA-100, average primary particle size (D50): 0.6 μm) manufactured by Fuji Titanium as the metal oxide, the same as in Example 1 described above. . That is, titanium oxide having an average primary particle size larger than that of Example 1 was used. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation B, and although it was lower than Example 1, it was good. The water content was 2 minutes (min), which was equivalent to Example 1. The breaking strength was 0.2 MPa, which was lower than that of Example 1, but sufficient strength was obtained. The electric conductivity was 80 μS / cm, which was slightly lower than that of Example 1, but sufficient purification performance could be realized.

<Example 6>
(Manufacture of electrodes)
Except for using 14 parts of anatase-type titanium oxide (product name: PT-401M, average primary particle size (D50): 0.08 μm) manufactured by Ishihara Sangyo Co., Ltd. as the metal oxide, the same as in Example 1 described above. . That is, titanium oxide having an average primary particle size smaller than that of Example 1 was used. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation B, and although it was lower than Example 1, it was good. The water content was 2 minutes (min), which was equivalent to Example 1. The breaking strength was 0.15 MPa, which was lower than that of Example 1, but sufficient strength was obtained. The electric conductivity was 80 μS / cm, which was slightly lower than that of Example 1, but sufficient purification performance could be realized.

<Example 7>
(Manufacture of electrodes)
Except for using 14 parts of anatase-type titanium oxide (product name: ST-750, average primary particle size (D50): 1.0 μm) manufactured by Fuji Titanium as the metal oxide, the same as in Example 1 described above. . That is, titanium oxide having an average primary particle size larger than that of Example 5 was used. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation C, and although it was lower than Example 1, it was almost good. The water content was 5 minutes (min), which was lower than that of Example 1. The breaking strength was 0.1 MPa, which was lower than that of Example 1, but almost sufficient strength was obtained. The electric conductivity was 120 μS / cm, which was lower than that in Example 1, but sufficient purification performance could be realized.

<Example 8>
(Manufacture of electrodes)
As metal oxide, it carried out similarly to Example 1 mentioned above except having used 14 parts of zinc oxides (The Sakai Chemical Co., Ltd. product name: 1 type of zinc oxide, average primary particle size (D50): 0.2 micrometer). That is, zinc oxide was used in place of titanium oxide as the metal oxide. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation C, and although it was lower than Example 1, it was almost good. The water content was 10 minutes (min), which was lower than in Example 1. The breaking strength was 0.2 MPa, which was lower than that of Example 1, but sufficient strength was obtained. The electric conductivity was 100 μS / cm, which was lower than that of Example 1, but sufficient purification performance could be realized.

<Example 9>
(Manufacture of electrodes)
In a planetary mixer with a disper, 100 parts of activated carbon powder (product name: Shirahige PC manufactured by Nippon Enviro Chemicals), 6.5 parts of acetylene black (product name: Denkapak powder form, manufactured by Denki Kagaku Kogyo Co., Ltd.) After adding 100 parts each of 1.5% aqueous solution of carboxymethyl cellulose (CMC, “BSH-12” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and adjusting the solid content concentration to 40% with ion-exchanged water, 25 Mix at 60 ° C. for 60 minutes. Next, after adjusting the solid content concentration to 32% with ion-exchanged water, the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution.

  5 parts (based on solid content) of an SBR aqueous dispersion having a glass transition temperature of −6 ° C. and a particle size of 100 nm and ion-exchanged water are added to the above mixed solution, and adjusted to a final solid content concentration of 30%. Mix for 10 minutes. This was defoamed under reduced pressure to obtain a slurry composition.

  The slurry composition was applied on a 50 μm-thick PET film with a comma coater so that the film thickness after drying was about 0.3 mm, and dried for 15 minutes (at a speed of 0.5 m / min, 60 ), And after heat treatment (120 ° C.) for 15 minutes, it was peeled off from the PET film to obtain an electrode.

(Evaluation)
The sterilization property was evaluation A, which was the same as that of Example 1, and was extremely good. The water content was 1 minute (min), which was slightly lower than that of Example 1, but was good. The breaking strength was 0.15 MPa, which was lower than that of Example 1, but almost sufficient strength was obtained. The electric conductivity was 60 μS / cm, which was the same as in Example 1, and sufficient purification performance could be realized.

<Comparative Example 1>
(Manufacture of electrodes)
The procedure was the same as in Example 1 except that no metal oxide was contained. The results are shown in Table 1.

(Evaluation)
The sterility was evaluated D, which was significantly lower than Example 1 and was poor. The water content was 120 minutes (min), which was much lower than in Example 1. The breaking strength was 0.3 MPa, which was equivalent to Example 1. The electric conductivity was 160 μS / cm, which was lower than that in Example 7, and sufficient purification performance could not be realized.

<Comparative example 2>
(Manufacture of electrodes)
Except for using 14 parts of anatase-type titanium oxide (product name: MC-50, average primary particle size (D50): 0.03 μm) manufactured by Ishihara Sangyo Co., Ltd. as the metal oxide, the same as in Example 1 described above. . That is, titanium oxide having an average primary particle size smaller than that of Example 6 was used. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluation B, and although it was lower than Example 1, it was good. The water content was 2 minutes (min), which was equivalent to Example 1. However, the breaking strength was 0.03 MPa, which was much lower than those of Example 1 and Example 6, and sufficient strength could not be obtained. The electric conductivity was 90 μS / cm, which was slightly lower than that of Example 1 and Example 6.

<Comparative Example 3>
(Manufacture of electrodes)
Example 1 described above, except that 14 parts of anatase-type titanium oxide (product name: ST-750 classified by Fuji Titanium, average primary particle size (D50): 1.2 μm) was used as the metal oxide. And so on. That is, titanium oxide having an average primary particle size larger than that of Example 7 was used. The results are shown in Table 1.

(Evaluation)
The sterilization property was evaluated C, which was similar to Example 7. The water content was 10 minutes (min), which was lower than that of Example 7. The breaking strength was 0.05 MPa, which was further lower than that of Example 7, and sufficient strength could not be obtained. The electric conductivity was 160 μS / cm, which was lower than that in Example 7, and sufficient purification performance could not be realized.

<Conclusion>
The following conclusions can be drawn from the above examples and comparative examples.
(With or without metal oxide)
From the comparison between Example 1 and Comparative Example 1, in addition to the activated carbon, the conductive material, and the binder, the electrode formed from the electrode composition containing the metal oxide does not contain the metal oxide. It can be seen that the breaking strength is equivalent to that of the electrode, and the sterility, water content, and electrical conductivity are excellent.

(Type of metal oxide)
As a kind of metal oxide to be contained, from the comparison between Example 1 and Example 8, titanium oxide is superior to zinc oxide in all of sterility, water content, breaking strength, and electrical conductivity. I understand that.

(Metal oxide content)
As content of the metal oxide (titanium oxide) to be contained, from the comparison of Examples 1 to 4, with respect to 100 parts of activated carbon, at least in the range of 8 to 35 parts of titanium oxide, It turns out that it is favorable in all of breaking strength and electric conductivity. In the range of 8 to 35 parts of titanium oxide, the breaking strength deteriorates as the number of parts increases, but the moisture content improves. On the other hand, the breaking strength improves as the parts number decreases, but the moisture content deteriorates. In particular, it can be seen that the range of 14 to 28 parts of titanium oxide is excellent in all of sterility, moisture content, breaking strength, and electrical conductivity. From these tendencies, when the amount is less than 5 parts of titanium oxide, the sterility and water content are insufficient, and when it exceeds 35 parts, the breaking strength (electrode strength) and the electrical conductivity (ion capturing ability) are insufficient. It is estimated that the point is insufficient.

(Particle size of metal oxide)
The average primary particle diameter (D50) of the metal oxide (titanium oxide) to be contained is at least a particle diameter of 0.08 to from the comparison of Example 1, Example 5 to Example 7, Comparative Example 2 to Comparative Example 3. It can be seen that in the range of 1.0 μm, sterility, moisture content, breaking strength, and electrical conductivity are all good. It can be seen that when the particle size is 0.03 or less or 1.2 or more, the breaking strength is insufficient. In the range of particle size of 0.03 to 1.2 μm, sterilization deteriorates as the particle size increases or decreases with respect to particle size of 0.2 μm, and water content deteriorates as the particle size increases, and the breaking strength is With respect to the particle size of 0.2 μm, the particle size becomes worse as the particle size becomes larger or smaller, and the electric conductivity tends to deteriorate as the particle size becomes larger or smaller with respect to the particle size of 0.2 μm. From the above, the range of 0.05 to 1.0 μm is preferable, the range of 0.07 to 0.9 μm is better, and the range of 0.1 to 0.8 μm is even better. Guessed.

  The embodiments and examples described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-described embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

Claims (3)

  A deionized electrode for a flowing water type capacitor formed of an electrode composition containing activated carbon, a conductive material, a binder, and a metal oxide having an average primary particle size of 0.05 μm to 1.0 μm.   The electrode according to claim 1, wherein the metal oxide is titanium oxide.   The electrode according to claim 2, wherein the titanium oxide is an anatase type.