JP3077859B2 - Method for removing surfactant from material sheet for gas diffusion electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a gas diffusion electrode used in electrolysis, fuel cells, electroplating, electrochemical reactors, etc., for producing a surface active material from a material sheet such as a reaction layer sheet or a gas diffusion layer sheet. A method for removing the agent.

[0002]

2. Description of the Related Art There are two types of gas diffusion electrodes: one consisting only of a reaction layer sheet and the other consisting of a reaction layer sheet and a gas diffusion layer sheet. Conventionally, in order to produce a gas diffusion electrode comprising only a reaction layer sheet, a hydrophilic carbon black, a water-repellent carbon black, and polytetrafluoroethylene are added and mixed with a surfactant (at this time, no surfactant is added) And then filter and dry and pulverize to add a solvent or filter to make a cake and impregnate the solvent, then form a sheet by rolling, then heat (2
(Up to 80 ° C) to evaporate and decompose and remove the solvent and surfactant to form a reaction layer sheet.Then, the reaction layer sheet is cut, and the reaction is carried out before carrying the catalyst or applying heat and pressure. The electrode is created.

In order to form a gas diffusion electrode comprising a reaction layer and a gas diffusion layer, a reaction layer sheet is prepared in the same manner as described above, while adding water-repellent carbon black and polytetrafluoroethylene to a surfactant. And mixed, then filtered, dried,
Crush and add solvent or filter to make cake and infiltrate solvent, then form sheet by rolling, then heat (up to 280 ° C) to evaporate and decompose solvent and surfactant To form a gas diffusion layer sheet, then cut the reaction layer sheet and the gas diffusion layer sheet, superimpose the two sheets, and apply heat and pressure to integrate them. ing.

[0004] In any of the above gas diffusion electrode manufacturing methods, the sheet formed by rolling is heated (280) immediately before forming the reaction layer sheet and the gas diffusion layer sheet.
The solvent and the surfactant are evaporated and decomposed to remove the solvent.In practice, however, the solvent evaporates, but the surfactant partially becomes tar-like and forms on polytetrafluoroethylene and carbon black. And it was extremely difficult to remove all the surfactant.

If the surfactant remains in the form of tar on the polytetrafluoroethylene and carbon black, water will flow through the water-repellent fine passages (water-repellent portion) in the reaction layer of the gas diffusion electrode. As a result, the contact area between the water-repellent fine passage (water-repellent portion) and the hydrophilic fine passage (hydrophilic portion) is reduced, the electrode is deteriorated, and the life is shortened. Also,
For gas diffusion layer, water-repellent fine passage (water-repellent part)
When water leaks in, water leaks in and out of the gas at the same time, so that the electrodes are deteriorated and the life is shortened.

In view of the above, recently, during the manufacturing process of a gas diffusion electrode, a solvent was heated and evaporated at a temperature at which a surfactant was not decomposed in a material sheet such as a reaction layer sheet or a gas diffusion layer sheet formed by rolling. Thereafter, as shown in FIG. 4, the material sheet 1 is immersed in a solvent tank 2, and the surfactant in the material sheet 1 elutes to a certain extent. When the solvent 3 is contaminated, the solvent 3 is sent to the distillation apparatus 4. The operation of putting the distilled clean solvent 3 into the solvent tank 2 is repeated several times or more.

However, it takes too much time until the material sheet 1 is immersed in the solvent tank 2 and the surfactant in the material sheet 1 elutes to a certain extent, and the surfactant is completely removed from the material sheet 1. In order to elute and remove the solvent, it is necessary to immerse it in the solvent tank 2 several times or more, which is very time-consuming and inefficient. Moreover, a large amount of solvent is required for the immersion treatment of the material sheet 1, and a large-sized distillation apparatus 4 is required.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention can greatly reduce the time required for eluting and removing a surfactant from a material sheet, and can use a small-sized distillation apparatus for a unit throughput of the material sheet. An object of the present invention is to provide a method for removing a surfactant from a material sheet for a diffusion electrode.

[0009]

In order to solve the above-mentioned problems, a method for removing a surfactant from a material sheet for a gas diffusion electrode according to the present invention comprises the steps of: removing a hydrophilic carbon black and / or a water-repellent carbon black; Ethylene chloride is added and mixed with a surfactant, and then filtered, dried and pulverized to add a solvent or filtered to make a cake and impregnated with the solvent, and then formed into a sheet by rolling, To remove the surfactant from the gas diffusion electrode material sheet obtained by heating and evaporating the solvent at a temperature at which the surfactant does not decompose, the solvent permeates from one surface of the gas diffusion electrode material sheet to the other surface, and passes through. The removed solvent is sent to a distillation apparatus to remove the surfactant, and the clean solvent is again transmitted from one surface of the gas diffusion electrode material sheet to the other surface to remove the surfactant in the gas diffusion electrode material sheet. Do The one in which the features.

[0010]

As described above, the method for removing a surfactant from a gas diffusion electrode material sheet according to the present invention is characterized in that a solvent permeates from one surface to the other surface of a gas diffusion electrode material sheet, and the permeated solvent is passed through a distillation apparatus. By turning, the solvent that has been cleaned by removing the surfactant is again transmitted from one surface of the gas diffusion electrode material sheet to the other surface, so that the surfactant in the gas diffusion electrode material sheet is It is efficiently eluted and removed by permeation, and the time required for complete elution and removal is greatly reduced. Further, since the amount of the solvent required for the elution removal treatment of the surfactant from the gas diffusion electrode material sheet is small, the distillation apparatus for removing the surfactant from the solvent may be small.

[0011]

EXAMPLE An example of a method for removing a surfactant from a gas diffusion electrode material sheet according to the present invention will be described. Average particle size 420
Å hydrophilic carbon black, water-repellent carbon black, and polytetrafluoroethylene dispersion having an average particle diameter of 0.3 μm in a ratio of 5: 3: 3, and a surfactant, Triton (trade name in this example) A 5% aqueous solution was added at a ratio of 120 and mixed, then poured into a filter, filtered, dried and pulverized, and a solvent, in this example, solvent naphtha was added at a ratio of 1.0: 2.0. mm-thick sheet, then heat-evaporate solvent naphtha at a temperature (60 ° C) at which the surfactant does not decompose. In order to remove the material, a gas diffusion electrode material sheet 1 is stretched in the middle and high part of the permeation tank 5 as shown in FIG. 1, and toluene 6 is transmitted from the upper surface to the lower surface of the material sheet 1 to elute Triton. , After the permeation tank 5 Toluene 6 'containing the accumulated Triton in turn through return channel 7 to the distillation device 4,
The toluene 6 that has been cleaned by removing the tritons in the distillation apparatus 4 is again passed through the supply path 8 from the upper surface to the lower surface of the material sheet 1 to elute and remove the triton in the material sheet 1. In this embodiment, when the pressure in the lower part of the permeation tank 5 is reduced, the permeation of toluene is further improved, the elution of triton is promoted, and the efficiency of elution removal of triton is improved.

Next, another embodiment will be described. Average particle size 420
水性 Water-repellent carbon black and polytetrafluoroethylene powder having an average particle diameter of 0.3 μm are arranged in a ratio of 7: 3, a 6% aqueous solution of Triton is added in a ratio of 200, mixed, and then filtered. It was poured into a vessel, filtered, dried and pulverized. Solvent naphtha was added at a ratio of 1: 1.85, and then rolled to a thickness of 0.15.
Triton is removed from the material sheet for the gas diffusion electrode (gas diffusion layer material sheet) obtained by forming a 6 mm thick sheet, and then heating and evaporating the solvent naphtha at a temperature (60 ° C) that does not decompose the surfactant. Then, as shown in FIG. 2, a gas diffusion electrode material sheet 1 'is stretched in the middle and high portions of each of the three permeation tanks 5, and toluene 6 is transmitted from the upper surface to the lower surface of the material sheet 1' so that Triton Is eluted, and after permeation, toluene 6 ′ containing Triton accumulated at the bottom of each permeation tank 5 is passed through a reflux path 7.
Through the distilling apparatus 4 to remove the tritons in the distilling apparatus 4, and clean the toluene 6 again from the upper surface to the lower surface of the material sheet 1 'through the supply path 8 to remove the triton in the material sheet 1'. . Also in this embodiment, when the pressure in the lower part of each permeation tank 5 is reduced, the permeation of toluene is further improved, the elution of Triton is promoted, and the efficiency of Triton elution removal is improved.

As can be seen from each of the above embodiments, the method of removing a surfactant from the gas diffusion electrode material sheet according to the present invention involves passing toluene 6 from the upper surface to the lower surface of the gas diffusion electrode material sheet 1, 1 '. Then, the permeated toluene 6 'is sent to the distillation apparatus 4, and the triton is removed from the upper surface of the material sheet 1, 1'. Is toluene 6
Is efficiently eluted and removed by the active permeation of, and the time until complete elution and removal is greatly reduced. Further, since the amount of toluene 6 required for elution and removal of Triton from the material sheets 1 and 1 'is small, the distillation apparatus 4 for removing Triton from toluene 6' from which Triton has been eluted may be small.

The permeation tank 5 in each of the above embodiments may be replaced with a solvent extraction tank 10 shown in FIG. That is, a plurality of inclined permeation tanks 5 ′ are provided in parallel in a large solvent extraction tank 10, and a material sheet 1 (or 1 ′) is stretched in each of the inclined permeation tanks 5 ′. By supplying toluene 6 and passing toluene 6 from the upper surface to the lower surface of the material sheet 1 (or 1 ′), triton in the material sheet 1 (or 1 ′) can be eluted and removed. 6 'reaches the distillation apparatus 4 through the reflux path 7, and the toluene 6 which has been cleaned by removing the tritons in the distillation apparatus 4 passes through the supply path 8 again from the upper surface to the lower surface of the material sheet 1 (or 1'). By doing so, the tritons in the material sheet 1 (or 1 ′) are efficiently eluted and removed by the active permeation of the toluene 6.

[0015]

As described above, according to the method for removing a surfactant from the material sheet for a gas diffusion electrode of the present invention, the surfactant in the material sheet is efficiently eluted and removed by the active permeation of the solvent. Therefore, the time required for complete elution and removal is greatly reduced. Further, since the amount of the solvent required for the elution treatment of the surfactant in the gas diffusion electrode material sheet is small, the distillation apparatus for removing the surfactant from the solvent may be small.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a method for removing a surfactant from a gas diffusion electrode material sheet of the present invention.

FIG. 2 is a view showing another embodiment of the method for removing a surfactant from a material sheet for a gas diffusion electrode of the present invention.

FIG. 3 is a view showing a modified example of a method of removing a surfactant from a gas diffusion electrode material sheet of the present invention.

FIG. 4 is a view showing a conventional method for removing a surfactant from a gas diffusion electrode material sheet.

[Explanation of symbols]

1, 1 'Material sheet for gas diffusion electrode 4 Distillation apparatus 5 Permeation tank 6 Toluene (solvent) 6' Toluene (solvent) containing triton (surfactant)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C25C 1/00-7/08 C25B 11/03 H01M 4/86-4/98

Claims (1)

(57) [Claims] 1. A hydrophilic carbon black and / or a water-repellent carbon black and polytetrafluoroethylene are mixed by adding a surfactant, and then filtered, dried and pulverized, and a solvent is added or filtered. A cake is formed, a solvent is infiltrated, a sheet is formed by rolling, and then the surfactant is removed from the gas diffusion electrode material sheet obtained by heating and evaporating the solvent at a temperature at which the surfactant does not decompose. Then, the solvent permeates from one side to the other side of the gas diffusion electrode material sheet, the permeated solvent is sent to a distillation apparatus, and the solvent that has been cleaned by removing the surfactant is re-used on one side of the gas diffusion electrode material sheet. A method for removing a surfactant from a material sheet for a gas diffusion electrode, comprising removing a surfactant from a material sheet for a gas diffusion electrode by transmitting the surfactant from the surface to another surface.