JP2008184718A - Activated carbon sheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active carbon sheet in which function of active carbon is maintained and to provide a method for producing the sheet. <P>SOLUTION: The active carbon sheet has a base material containing fibrous or powdery active carbon and inorganic oxide microparticles fixed on the base material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an activated carbon sheet, and by fixing inorganic oxide fine particles on the surface of a substrate containing activated carbon, it is possible to solve the problems caused by the surface activity unique to activated carbon without causing a decrease in the function of activated carbon. The activated carbon sheet and the manufacturing method thereof.

  Activated carbon has been used for various applications as an adsorbent. In recent years, in order to create a clean and comfortable environment, various organic compound gas processing measures such as VOC (Volatile Organic Com-ound), dust-related defect countermeasures in semiconductor-related workplaces, etc., and humidity as a measure against dry skin Development for control applications is being planned.

  Activated carbon is also used in backup power supplies for instantaneous power outages, hybrid vehicle engine assist, and electric double layer capacitor electrode materials that have begun to be used for energy recovery in elevators.

However, a drastic solution to the problems caused by the surface activity inherent to activated carbon has not been made, and it has been achieved to date. The activated carbon often ignites when left in the atmosphere due to the surface activity of the activated carbon. Moreover, activated carbon is used as the polarizable electrode of the electric double layer capacitor, and various proposals for improving the capacitance have been made (for example, see Patent Document 1 and Patent Document 2). When activated carbon is used as an electrode material for an electric double layer capacitor, activated carbon does not cause a chemical reaction, so it is difficult to structurally degrade, but it induces electrolyte degradation due to the surface activity of activated carbon. May cause aging.
JP 2004-149399 A JP 2001-217162 A

  An object of this invention is to solve the subject resulting from the surface activity intrinsic | native on activated carbon mentioned above, without reducing the function of activated carbon.

  As a result of intensive studies in view of conventional problems, the present inventors fixed a small amount of inorganic oxide fine particles on a sheet containing activated carbon, thereby igniting due to the surface activity inherent to activated carbon or deterioration of the electrolytic solution, etc. It was found that the problem can be solved. This small amount refers to a low fixed amount below a predetermined amount, and within this low fixed amount range, the surface treatment effect such as flame retardant by fixing is higher than that of a high fixed amount, and the activated carbon has. It has been found that the performance such as adsorption does not deteriorate.

  In addition, as examples of applications, the application to a honeycomb rotor member of a dehumidifying or air purifying apparatus that adsorbs and desorbs moisture in the atmosphere, unpleasant odor components, gaseous harmful components, etc. at high speed, or The inventors have found an activated carbon sheet of activated carbon suitable for use in extending the life by applying the multilayer capacitor to an electrode material, and a method for producing the same.

  That is, the first invention of the present invention provides an activated carbon sheet in which inorganic oxide fine particles are fixed to a substrate containing fibrous or powdered activated carbon.

  The second invention of the present invention provides an activated carbon sheet in which inorganic oxide fine particles are fixed to a substrate containing 50% by mass or more and 85% by mass or less of fibrous or powdered activated carbon.

  Furthermore, a third invention of the present invention provides the activated carbon sheet according to the first invention, wherein the content of the fibrous or powdered activated carbon in the substrate is 75% by mass or more and 85% by mass or less. It is.

  Furthermore, a fourth invention of the present invention is the invention according to any one of the first to third inventions, wherein the average particle diameter of the inorganic oxide fine particles is 50 nm or more and 300 nm or less, and the inorganic oxide fine particles have a weight of the substrate. The activated carbon sheet which is the fixed amount of 0.1 mass% or more and 10 mass% or less as a reference | standard is provided.

  Furthermore, a fifth invention of the present invention provides the activated carbon sheet according to any one of the first to fourth inventions, wherein the surface of the inorganic oxide fine particles is chemically bonded to a silane compound having an unsaturated bond. Is.

  Furthermore, the sixth invention of the present invention includes a step of forming a substrate containing fibrous or powdered activated carbon, and inorganic oxide fine particles having an average particle diameter of 50 nm or more and 300 nm or less dispersed on the surface of the substrate. A method for producing an activated carbon sheet comprising: a step of applying the slurry, and a step of fixing the inorganic oxide fine particles by removing the solvent contained in the slurry by heating and drying from the substrate sheet coated with the slurry. is there.

  Furthermore, a seventh invention of the present invention provides the method for producing an activated carbon sheet according to the sixth invention, wherein the step of fixing the inorganic oxide fine particles includes a step of irradiating active energy rays.

  According to the activated carbon sheet in which the inorganic oxide fine particles are fixed and the method for producing the same according to the present invention, the inorganic oxide fine particles are fixed to the base material containing the fibrous or powdered activated carbon, thereby having the activated carbon. Functions such as flame retardancy and reduced charge / discharge cycle life can be exhibited without impairing the functions such as the moisture absorption / desorption performance and the capacitor capacity derived from the specific surface area of the activated carbon.

  Hereinafter, embodiments of the present invention will be described in detail.

  The substrate of the activated carbon sheet of each embodiment of the present invention is a sheet containing at least one of fibrous or powdered activated carbon, such as papermaking, coating, roll rolling, etc. under blending conditions depending on the application. Molded by the manufacturing method.

  FIG. 1 is an enlarged view of a part of a cross section of an activated carbon sheet 100 according to an embodiment of the present invention. In addition, this figure demonstrates typically an example of the activated carbon sheet 100 of this embodiment, Comprising: The exact structure of a substance is not shown. The activated carbon sheet 100 of the present embodiment is configured by fixing the inorganic oxide fine particles 2 on at least one surface of the substrate 4 including the fibrous or powdered activated carbon 1. FIG. 1 shows an example in which the inorganic oxide fine particles 2 are also fixed to both the front and back surfaces of the base material 4 and the gaps in the thickness direction of the base material 4.

  The substrate 4 is composed of fibrous or powdered activated carbon 1 and an additive for binding the activated carbon 1, imparting strength as a sheet, or exhibiting the function of activated carbon. In the present embodiment, pulp, fibers, resin, and the like, which are components constituting the substrate 4 other than the activated carbon 1, are referred to as a binder 3.

  FIG. 2 schematically illustrates a part of a cross section of another embodiment of the activated carbon sheet 100 according to the embodiment of the present invention. In FIG. 2, the activated carbon 1 and the binder 3 are densely packed in the cross-sectional thickness direction of the substrate 4, and the inorganic oxide fine particles 2 are fixed to both the front and back surfaces of the substrate 4.

  As mentioned above, mechanical means such as punching, optical means such as laser, etching, etc. on the base material 4 formed by a manufacturing method such as papermaking, coating, roll rolling under the blending conditions according to the application The porous sheet in which a large number of openings are provided on the surface of the substrate 4 can be used as the substrate 4 by chemical means such as the above. In addition, a sheet made of woven fabric or knitted fabric made of synthetic fiber in which powdered activated carbon 1 is blended can be used as the substrate 4.

  The fibrous or powdered activated carbon 1 preferably has a function such as adsorptivity or electric double layer capacitance.

(First embodiment)
Next, the activated carbon sheet according to the first embodiment of the present invention will be described in detail below. The activated carbon sheet 100 of the present embodiment is mainly used as a honeycomb rotor dehumidifying member for humidity control.

  For example, in the case of desiccant dehumidification, the base material 4 of the activated carbon sheet 100 of the present embodiment is made of various pulps or synthetic short fibers (wood pulp, polyethylene pulp, rayon pulp, vinylon pulp, polyvinyl alcohol fiber by a papermaking method. , Polyacrylonitrile fiber, polyvinyl chloride fiber, polyolefin fiber, polyacrylonitrile fiber, etc.), glass fiber, and a binder 3 made of a resin binder such as a small amount of acrylic, etc. are blended together with activated carbon 1, It is manufactured by papermaking a slurry mixed so as to be distributed almost uniformly.

  The activated carbon 1 in the activated carbon sheet 100 of this embodiment needs to have a hygroscopic property. In order to make paper and use for desiccant, it is preferable that activated carbon 1 is blended at a content of 50% by mass or more as a constituent in the papermaking raw material as a base component, and mixed papermaking is used as a base material, more preferably. May contain activated carbon 1 in the base material 4 at a content of 50% by mass or more and 85% by mass or less.

  When the content of the activated carbon 1 is less than 50% by mass, the strength as a mixed paper is sufficient, but the adsorption performance is inferior. In addition, when the content of the activated carbon 1 is more than 85% by mass, the activated carbon is dropped, and the paper-made paper is hardened. Therefore, the corrugated honeycomb is processed in the post process in the vicinity of the top of the unevenness formed by the gears. The crack becomes easy to run, and the corrugating workability is significantly reduced.

  The activated carbon 1 of the present embodiment is preferably a powder having a particle size of 100 μm or less or a short fiber having a diameter of 100 μm or less and a length of 30 mm or less in consideration of ease of papermaking. For papermaking, add a suitable amount of reinforcing materials such as pulp, fibrous or powdered activated carbon, and glass fiber for the purpose of ensuring the strength of the structure, and round the dilute slurry obtained by mixing these mixtures with water. Roll up with a paper machine such as a net.

  Since the inorganic oxide fine particles 2 fixed to the mixed paper which is the base material 4 of the present embodiment touches the gas to be adsorbed first, it is preferable that the inorganic oxide fine particles 2 have flame retardant and hygroscopic properties. In addition, although details are shown in the Examples, the fixed amount of the inorganic oxide fine particles 2 is preferably 0.1% by mass or more and 10% by mass or less based on the weight of the substrate 4. Even if it fixes exceeding 10 mass%, a flame retardance does not change, but a flame retardance grade falls rather as a fixed amount increases. Moreover, when it is less than 0.1% by mass, sufficient flame retardancy cannot be obtained.

  As the inorganic oxide fine particles 2 used in the present embodiment, inorganic oxides such as titanium dioxide, zeolite, silica sand, aluminosilicate, silica gel, diatomaceous earth, and manganese dioxide can be used. In particular, for desiccant dehumidification, those exhibiting hygroscopicity are preferred.

  The inorganic oxide fine particles 2 used in the present embodiment preferably have a small particle size, can be appropriately fixed to the activated carbon mixed paper as the base material 4, and are fixed in the honeycomb rotor processing step. The average particle size is preferably 300 nm or less so that 2 is not easily detached or peeled off.

  When the particle diameter of the inorganic oxide fine particles 2 is larger than 300 nm, it is difficult to fix the inorganic oxide fine particles 2 to the base material 4 or to be easily detached even if fixed, and it is difficult to obtain durability. In addition, when the average particle size of the inorganic oxide fine particles 2 is less than 50 nm, the activated carbon surface activity cannot be controlled due to the activity of the particles due to the particle size being too small. The average particle diameter of the inorganic oxide fine particles 2 used in is preferably 50 nm or more.

  In order to make the adhesion to the substrate 4 stronger, the surface of the inorganic oxide fine particles 2 is treated with a silane monomer having an unsaturated bond and chemically bonded (hereinafter referred to as “silane monomer-coated inorganic oxidation”). It is preferable to use a material fine particle ”. Here, the unsaturated bond may be a reactive functional group such as a vinyl group, an epoxy group, a styryl group, a methacrylo group, an acryloxy group, or an isocyanate group.

  Examples of silane monomers used in this embodiment include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, 2 -(3,4 epoxy cyclohexyl) ethyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3- And acryloxypropyltrimethoxysilane.

  The inorganic oxide fine particles 2 or the silane monomer-coated inorganic oxide fine particles 2 used in the present embodiment are used in a state of being dispersed in a solvent such as methanol or isopropyl alcohol. Dispersion in a solvent is performed by stirring and dispersion using a homogenizer or a magnetic stirrer, pulverization / dispersion using a ball mill, sand mill, high-speed rotation mill, jet mill, or the like, or dispersion using ultrasonic waves.

  For fixing the inorganic oxide fine particles 2 to the activated carbon mixed paper as the base material 4, the slurry in which the inorganic oxide fine particles 2 are dispersed is applied to the activated carbon mixed paper as the base material 4 and the solvent is evaporated by heating and drying. -Evaporate and remove. As a method for coating, known methods such as brush coating, spraying, dipping, and various coater methods may be used.

  Immobilization of the silane monomer-coated inorganic oxide fine particles 2 on the activated carbon mixed paper as the base material 4 is performed by applying a slurry in which the silane monomer-coated inorganic oxide fine particles 2 are dispersed to the base material 4 to evaporate and volatilize the solvent. After that, by irradiating active energy rays such as radiation, electron beam, and ultraviolet rays, a part of the unsaturated bond is covalently bonded to the base material, so that a stronger fixation is achieved by so-called graft polymerization. Can do. Alternatively, graft polymerization using a peroxide catalyst instead of active energy rays, or immobilization by chemical bonding by graft polymerization using heat or light energy may be used.

  Silane monomer-coated inorganic oxide fine particles 2 are sufficiently dispersed by adding the required amount of inorganic oxide fine particles to an organic solvent such as methanol, ethanol, acetone, toluene, xylene or the like. Can be obtained. If the amount of the silane monomer used is 0.1% by mass or more with respect to the weight of the inorganic oxide fine particles 2, the effect is exhibited, but in order to fix firmly, the amount is 1% by mass or more and 10% by mass or less. Is preferred.

  The activated carbon sheet 100 in which the inorganic oxide fine particles 2 or the silane monomer-coated inorganic oxide fine particles 2 are fixed to the activated carbon mixed paper as the base material 4 is processed into a shape suitable for dehumidification. In particular, for desiccant use for dehumidification that is incorporated into equipment, corrugation processing is performed using a corrugated cardboard manufacturing method, and laminated into a block and shaped into a block, or rolled into a rotor. used.

  The activated carbon sheet 100 of this embodiment is excellent in flame retardancy and, when used in a desiccant device, exhibits excellent performance without impairing the dehumidifying performance of activated carbon as a honeycomb rotor dehumidifying member for humidity control.

(Second Embodiment)
Next, an embodiment in which the activated carbon sheet of the second embodiment of the present invention is mainly used for an electric double layer electrode material sheet will be described.

  In the case of the use of an electric double layer electrode material sheet, the base material 4 in the activated carbon sheet 100 of the present embodiment is, for example, PTFE (polytetrafluoroethylene), polyvinylidene fluoride (PVDF), Then, a small amount of carbon black, artificial graphite powder or the like as a conductive material is blended and sufficiently kneaded to form a paste, and then formed into a sheet by rolling or the like. Alternatively, there is a manufacturing method in which activated carbon, a binder resin, and a conductive material are coated with an organic solvent and the organic solvent is removed to form the base material 4.

  When used for an electric double layer electrode material sheet, the activated carbon 1 needs to be excellent in performance as an electric double layer capacitor electrode. The electric double layer capacitor has a structure in which a pair of positive and negative polarizable electrodes made of activated carbon or the like are opposed to each other through a porous separator through which ions pass in a solution containing electrolyte ions. When a DC voltage is applied, the anion in the solution is attracted to the electrode polarized to the positive (+) side, and the cation in the solution is attracted to the electrode polarized to the negative (−) side. The electric double layer formed in (1) is used as electric energy.

  As described above, it is said that the electric double layer capacitor is excellent in power density and excellent in cycle life characteristics of charge / discharge because it does not involve a chemical reaction in principle.

On the other hand, the electrolyte solution used for this electric double layer capacitor includes aqueous systems such as sulfuric acid, sodium sulfate, sodium hydroxide, and potassium hydroxide, and non-aqueous systems such as BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ^{− and the} like. Quaternary ammonium salt or quaternary phosphonium salt as an electrolyte, ethers such as diethyl ether, ethylene glycol monomethyl ether, dibutyl ether, etc., amides such as formamide, N-methylformamide, etc., or 1,2 dimethoxyethane, ethylene carbonate, γ -It can be used as a solution dissolved in an organic solvent such as butyl lactone, propylene carbonate or acetonitrile.

  As the porous separator that transmits ions interposed between the electrodes, a microporous polyethylene or polypropylene film, a nonwoven fabric made of these fibers or glass fibers, or the like can be used.

  As the electrolyte solution used in the electric double layer capacitor, the aqueous system can be used only at a low voltage of about 1V due to restrictions on electrolysis of water, and the organic and non-aqueous systems that can be used at a high voltage of about 3V are more moisture in the manufacturing process. Non-aqueous systems have become mainstream in recent years because of the large energy capacity that needs to be managed. Non-aqueous organic electrolytes gradually deteriorated by the action of active sites on the surface of activated carbon, which is an electrode, when charging and discharging are repeated, and the charge / discharge cycle life characteristics are lowered, and improvement has been demanded.

  The electrode material using the activated carbon sheet of the present embodiment exhibits an effect of extending the life particularly in a non-aqueous organic electrolytic solution system.

  When the activated carbon sheet 100 of the present embodiment is rolled into an electric double layer electrode material, the capacitor capacity increases as the amount of activated carbon increases because it is a structure as described above, but PTFE which is a binder. There is an upper limit to the content of activated carbon due to manufacturing restrictions such as kneading and pasting with carbon black as a conductive material.

  In the activated carbon sheet 100 of this embodiment, it is preferable to make the content rate of the activated carbon 1 in the base material 4 into 75 mass% or more and 85 mass% or less. That is, when the content rate of the activated carbon 1 in the base material 4 is less than 75% by mass, the performance as an electric double layer capacitor is not sufficient, and the content rate of the activated carbon 1 in the base material 4 is 85% by mass. If it exceeds 1, the electrode material sheet becomes brittle, and the handling property of the sheet deteriorates, which hinders the manufacturing process.

  In the base material 4 obtained through kneading, pasting, and rolling, the inorganic oxide fine particles 2 or the silane monomer-coated inorganic oxide fine particles 2 are fixed on the surface by the method described above. In order to dislike moisture in organic capacitor electrode applications, the inorganic oxide fine particles 2 are preferably titanium oxide fine particles obtained by a chlorine method that hardly absorb moisture, or fine particles obtained by pulverizing silica sand or the like.

  The average particle diameter of the inorganic oxide fine particles 2 of the present embodiment is preferably 50 nm or more and 300 nm or less. If it is less than 50 nm, the activity is too high due to the specific surface area of the fine particles, which is not preferable. Moreover, when it exceeds 300 nm, it will become difficult to fix to the base material sheet 4.

  The fixed amount of the inorganic oxide fine particles 2 of the present embodiment is preferably 0.1% by mass or more and 10% by mass or less based on the weight of the substrate 4.

  If the fixed amount is close to zero, the surface activity of the activated carbon cannot be controlled, and if the fixed amount is too large, the control effect is reduced or almost lost.

  Immobilization of the silane monomer-coated inorganic oxide fine particles 2 to the substrate 4 is performed by applying a slurry in which the silane monomer-coated inorganic oxide fine particles 2 are dispersed to the substrate 4 and evaporating and evaporating the solvent. By irradiating an active energy ray such as an electron beam or an ultraviolet ray, stronger immobilization can be performed by chemical bonding by so-called graft polymerization in which a part of the unsaturated bond is covalently bonded to the substrate. Alternatively, graft polymerization using a peroxide catalyst instead of active energy rays, or immobilization by chemical bonding by graft polymerization using heat or light energy may be used.

  The silane monomer-coated inorganic oxide fine particles 2 are sufficiently obtained by adding the required amount of the inorganic oxide fine particles 2 to an organic solvent such as methanol, ethanol, acetone, toluene, xylene or the like. Obtained by dispersing. If the amount of the silane monomer used is 0.1% by mass or more based on the inorganic oxide fine particles 2, the effect is exhibited. However, in order to firmly fix the silane monomer, it is preferably 1% by mass or more and 10% by mass or less. .

  The non-aqueous capacitor using the electrode material made of the activated carbon sheet 100 of the present embodiment thus obtained exhibits performance excellent in long-term charge / discharge cycle characteristics.

  Next, the activated carbon sheet of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

[First embodiment]
(Preparation of base material using mixed paper for desiccant dehumidification rotor)
An activated carbon powder manufactured by Kuraray Chemical Co., Ltd. was used as a raw material for mixed paper used as a base material, and was used as a pulverized powder having a particle size of 10 μm so as to be suitable for papermaking. In addition, as a fiber material for papermaking, wood pulp (NBKP: softwood bleached kraft pulp) treated with ordinary beaters, etc., organic synthetic fiber pulp (vinylon pulp) for papermaking, and diameter made by Nippon Sheet Glass Co., Ltd. Short glass fibers of about 10 μm were used. In addition, in order to ensure papermaking properties, a slurry of activated carbon powder, fiber material for papermaking, and water is diluted with a large amount of water using an acrylic resin binder manufactured by Showa Denko K.K. A substrate made of mixed paper was rolled up.

  Table 1 shows the composition of the base material and the characteristics of the base material. The base material composition shown in Table 1 is the weight ratio of the base material as a finished product. Here, as a characteristic of the base material, the tensile strength was measured by measuring a breaking strength when a strip sample having a width of 15 mm was cut out in the paper making direction (longitudinal direction) and pulled at a speed of 1 mm / min. In addition, a strip sample having a width of 15 mm was bent by hand, and the presence or absence of cracks was visually observed to evaluate workability and handleability.

Under all blending conditions, it was possible to obtain a base material made of mixed paper with a good texture of 120 g / m ² . Substrate No. 1 to 4 were judged to be able to withstand the fixing and corrugation processing of inorganic oxide fine particles in the subsequent process, but in No5 where the activated carbon content exceeded 85%, cracks occurred in the bending test.

For bases No. 1 to No. 4 having a base weight of 120 g / m ² shown in Table 1, 3-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.) was used as a silane coupling agent in an ethanol solution slurry in which silica gel was dispersed as inorganic oxide fine particles. 3% by mass of KBM-503) manufactured by Co., Ltd. was added to the inorganic oxide fine particles and stirred overnight, and a coupling agent was condensed on the silica gel surface to chemically bond it to the silica gel surface. A base material, which is a mixed paper, was immersed in this slurry, dried at 110 ° C. for 10 minutes, and then fixed by irradiation with an electron beam of 5 Mrad at an acceleration voltage of 200 kV. The amount of immobilization was adjusted by the number of immersions to obtain four levels of activated carbon sheets with a fixed amount of 0.1 mass%, 5 mass%, 10 mass%, and 12 mass%.

  The adhesion of the inorganic oxide fine particles of the obtained activated carbon sheet was evaluated visually by repelling the surface of the sheet with a finger and determining whether or not powder fall off due to impact. All activated charcoal sheets did not fall off and showed good adhesion. The amount of immobilization was obtained by applying the slurry to the mixed paper as a base material, drying and measuring the mass, and calculating from the difference from the mass with the base material.

  Moisture absorption characteristics are as follows: 3g of sample was evacuated at 80 ° C for 1 hour, allowed to cool, and the rate of increase in weight due to moisture absorption under the conditions of 20 ° C and moisture of 15g / kg-DA (dry air) The change was measured by a so-called McBain balance method. Here, as a reference for the weight increase rate, the weight of the base material was calculated from the area of the base material. The properties and evaluation results of the obtained sheet-like adsorbent are shown in Table 2.

  Flame retardancy was performed based on UL94 standards. That is, a 125 × 10 mm strip sample was suspended, and the lowermost position was heated and ignited with a gas burner and allowed to stand, and the remaining flame time was evaluated. The results are shown in Table 2. In Table 2, the average particle size of the inorganic oxide fine particles and the evaluation results of only the base material on which the inorganic oxide fine particles are not fixed are also shown for comparison.

  Compared to the hygroscopic properties of only the base material on which inorganic oxide fine particles are not fixed (activated carbon sheet No. 1-1, 4-1), the base material on which inorganic oxide fine particles are fixed absorbs moisture from the same base material. Excellent characteristics. Moreover, when the compounding quantity of the activated carbon in an activated carbon sheet | seat becomes 50 mass% or more, it will show sufficient moisture absorption characteristics (activated carbon sheet No.2-1, 2-2, 2-3, 2- 4, 3-1, 3-2, 3-3, 4-2, 4-3, 4-4).

  Regarding flame retardancy, when the particle diameter of the inorganic oxide fine particles is 50 nm or more and 300 nm or less and the fixed amount of the inorganic oxide fine particles is 0.1 mass% or more and 10 mass% or less (activated carbon sheet No. 2-2, In 2-3, 3-1, 3-2, 4-2, 4-3), the flame retardancy is improved.

[Second Embodiment]
(Creation of base sheet for use in electric double layer capacitors)
Resin-type activated carbon with an average particle diameter of 20 μm obtained by the KOH activation method, PTFE (polytetrafluoroethylene) manufactured by Mitsui DuPont Fluorochemical Co., Ltd., and Ketjen Black manufactured by Mitsubishi Chemical as a highly conductive carbon black, The paste was sufficiently kneaded with a roll blender under the blending conditions shown in Table 3 to fiberize PTFE, which was rolled to obtain a sheet-like substrate having a thickness of 0.5 mm.

  Table 3 shows the composition of the base material and the characteristics of the base material. In addition, the compounding composition of the base material shown in Table 3 is a weight ratio in the base material as a finished product.

  In the base material No. 9 in which the content of activated carbon exceeded 85% by mass, cracks occurred when the paste was sandwiched between release films and the sheet was peeled off from the release film after rolling.

  Using base materials No. 6, 7 and 8 as electric double layer capacitor applications, toluene solution slurry in which titanium oxide fine powder was dispersed as inorganic oxide fine particles, 3-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent KBM-503) manufactured by Co., Ltd. was added to the inorganic oxide fine particles in an amount of 3% by mass and stirred overnight, and a coupling agent was condensed on the titanium oxide surface to chemically bond with the titanium oxide surface.

  Substrate Nos. 6, 7, and 8 were immersed in this slurry, pulled up, dried at 110 ° C. for 10 minutes, and then irradiated with an electron beam at an acceleration voltage of 200 kV for 5 Mrad to immobilize titanium oxide on the substrate sheet. The immobilization amount was adjusted by the number of immersions.

  The activated carbon sheet thus obtained and a disk having a diameter of 20 mm are punched out from each sheet on which the comparative inorganic oxide fine particles are not fixed, and vacuum-dried at 200 ° C. for 15 hours to obtain the performance as a polarizable electrode. A sample for evaluation was used.

  The sheet-like electrode was assembled into an evaluation cell as shown in FIG. 3 and evaluated in a glove box in which high-purity argon was circulated.

  In FIG. 3, 11 is an upper lid made of aluminum, 12 is an O-ring made of Viton (registered trademark), 13 is a current collector plate made of aluminum, and 14 is an insulating material using Teflon (registered trademark). Reference numeral 15 denotes an aluminum container, 16 denotes an aluminum spring, and 18 denotes a polypropylene porous separator through which an electrolyte passes. 17 is a polarizable electrode sample for performance evaluation, and the electric capacity was evaluated using the activated carbon sheet of the present invention as an electrode.

As the electrolytic solution, trade name LIPASTE-P / EAFIN (1 mol / liter) manufactured by Toyama Pharmaceutical Co., Ltd. using propylene carbonate as a solvent and (C ₂ H ₅ ) ₄ NBF ₄ as an electrolyte was used. The measurement temperature was room temperature.

  The charge / discharge characteristics were measured by using a charge / discharge test apparatus HJ-101SM6 manufactured by Hokuto Denko Co., Ltd., and repeatedly charging / discharging at 0 to 3.0 V under a current condition of 250 mA (64 mA / cm 2). The electric capacity per mass (F / g) of the polarization electrode of the double layer capacitor was calculated. The durability was evaluated based on the ratio of the electric capacity after 200 charge / discharge cycles based on the second charge / discharge electric capacity where the electric capacity is stabilized.

  As can be seen from Table 4, the electric capacity (F / g) at the second charge does not differ greatly between the sheets due to the same base material. In the electrode using the base material No. 6 with the activated carbon content of less than 75%, the initial capacity of the second charge is small (sheet No. 6-1 and 6-2), which is insufficient as an electric double layer capacitor.

  Electrodes (sheets No. 7-1 and 8-1) in which inorganic oxide fine particles are not fixed, electrodes having an immobilization amount of less than 0.1% by mass (sheet No. 7-2), and immobilization amount of 10% by mass Electrodes (sheets No. 7-7, 8-7), electrodes having an average particle size of inorganic oxide fine particles of less than 50 nm (sheets No. 7-3, 8-2), electrodes exceeding 300 nm (sheets No. 7-6, 8) -6) and the electrodes according to the sheet Nos. 7-4, 7-5, 8-3, 8-4, 8-5, a large difference is seen in the capacity maintenance rate for the second charge / discharge 200th, It turned out that it becomes an electric double layer capacitor excellent in cycle life characteristic by using the electrode by the activated carbon sheet of the present invention.

It is the schematic diagram which expanded the cross section of the activated carbon sheet of embodiment of this invention partially. It is the schematic diagram which expanded the cross section of the other form of the activated carbon sheet of embodiment of this invention partially. It is an evaluation apparatus of an electric double layer electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Activated carbon sheet 1: Activated carbon 2: Inorganic oxide fine particle 3: Binder 4: Base material 11: Aluminum top lid 12: Viton O-ring 13: Aluminum collector plate 14: Insulating material 15: Aluminum container 16: Aluminum spring 17: Polarizable electrode sample for performance evaluation 18: Polypropylene porous separator through which electrolyte passes

Claims (7)

A substrate containing activated carbon in fiber or powder form,
Inorganic oxide fine particles fixed to the substrate;
The activated carbon sheet characterized by having.   2. The activated carbon sheet according to claim 1, wherein a content of the fibrous or powdered activated carbon in the base material is 50% by mass or more and 85% by mass or less.   The activated carbon sheet according to claim 1, wherein a content of the fibrous or powdered activated carbon in the base material is 75% by mass or more and 85% by mass or less. The inorganic oxide fine particles have a fixed amount of 0.1% by mass to 10% by mass based on the weight of the base material, and
The activated carbon sheet according to any one of claims 1 to 3, wherein an average particle diameter of the inorganic oxide fine particles is 50 nm or more and 300 nm or less.   The activated carbon sheet according to any one of claims 1 to 4, wherein the surface of the inorganic oxide fine particles is chemically bonded to a silane compound having an unsaturated bond. Forming a substrate containing fibrous or powdered activated carbon;
Applying a slurry in which inorganic oxide fine particles having an average particle diameter of 50 nm to 300 nm are dispersed on the surface of the substrate;
Removing the solvent contained in the slurry by heat drying from the substrate coated with the slurry, and fixing the inorganic oxide fine particles to the substrate;
A method for producing an activated carbon sheet, comprising: The step of fixing the inorganic oxide fine particles to the surface of the base material,
The method for producing an activated carbon sheet according to claim 6, comprising a step of irradiating active energy rays.

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