KR20200113975A - Carbon paper for GDL and preparation method thereof - Google Patents

Abstract

The present invention relates to a method of producing carbon fiber paper for GDL and carbon fiber paper for GDL produced by the same, and more specifically, to a method of producing carbon fiber paper for GDL, which comprises the steps of: mixing an organic solvent, carbon fiber, a thickener, a binder, and water; and molding the mixture thereof, and carbon fiber paper for GDL produced by the same. According to the present invention, the injection amount of the thickener can be minimized.

Description

Carbon fiber paper for GDL and its manufacturing method {Carbon paper for GDL and preparation method thereof}

The present invention relates to a carbon fiber paper for GDL and a method for manufacturing the same, and more particularly, to a carbon paper having uniform thickness, air permeability, and excellent electrical conductivity by dispersing carbon fibers through ultrasonic treatment. It relates to a carbon fiber paper manufacturing method and a carbon fiber paper for GDL manufactured by the manufacturing method.

In general, a polymer electrolyte membrane fuel cell (PEMFC) is applied as a fuel cell for automobiles, and this polymer electrolyte membrane fuel cell normally exhibits high output performance of at least tens of kW under various driving conditions of automobiles. To do this, it is known that hundreds of unit cells must be repeatedly stacked to form a stack, and stably operate in a wide current density range.

The polymer electrolyte membrane fuel (PEMFC) is a polymer electrolyte membrane (PEM), a catalyst, a gas diffusion layer (GDL), and an electrolyte electrode assembly (MEA). ), and a bipolar plate.

The principle that electricity is generated through the polymer electrolyte membrane-electrode assembly (MEA) is that the hydrogen supplied to the anode, the anode of the fuel cell, is separated into hydrogen ions and electrons, and then the hydrogen ions are polymerized. Through the electrolyte membrane, it moves toward the cathode, which is the cathode, and electrons move to the cathode through an external circuit, whereby oxygen molecules, hydrogen ions, and electrons react together to generate electricity and heat, and water as a reaction by-product. Will be created.

On the other hand, the water generated during the electrochemical reaction in the fuel cell plays a desirable role in maintaining the humidification of the membrane-electrode assembly when an appropriate amount is present. However, if the excess water is not properly removed, the “water overflow” at a high current density. (Flooding)" phenomenon occurs, and the overflowed water acts to prevent the efficient supply of reaction gases into the fuel cell, resulting in greater voltage loss.

Gas diffusion layer (GDL) is a polymer electrolyte membrane (PEM) that evenly supplies hydrogen and oxygen, acts as an electric conductor that moves electrons reacted in the catalyst layer from the separator plate, and polymer Since the electrolyte membrane plays a very important role in a polymer electrolyte membrane fuel cell, such as supplying or discharging moisture to maintain proper moisture, it must have conductivity, porosity and hydrophobicity, and have thermal and chemical stability.

Therefore, carbon fiber having excellent electrical conductivity, low electrical resistance, and excellent heat resistance and chemical resistance by carbonization heat treatment at high temperature is attracting attention as a material for gas diffusion layer (GDL).

However, in order to manufacture a gas diffusion layer (GDL) using carbon fiber, it must be uniformly dispersed in an aqueous solution, but due to the lack of dispersion technology, porosity distribution, gas permeability, electrical conductivity, and electrical resistance are not satisfied at the same time. There is a situation.

Korean Patent Publication No. 1304489

The present invention was derived to solve the above problems, and carbon fibers in an aqueous solution can be uniformly dispersed so that the gas diffusion layer (GDL) has a uniform thickness, air permeability, and excellent electrical conductivity. The purpose of this is the manufacturing method of carbon fiber paper for GDL and the carbon fiber paper for GDL manufactured by the manufacturing method.

In order to solve such a technical problem, the method of manufacturing a carbon fiber paper for GDL according to the present invention comprises: mixing an organic solvent, carbon fiber, a thickener, a binder, and water; And it characterized in that it comprises a step of molding.

In addition, in the method for producing carbon fiber paper for GDL according to the present invention, the step of mixing an organic solvent, carbon fiber, a thickener, a binder, and water includes: i) a first mixture of carbon fibers mixed with an organic solvent, a thickener, a binder, and A first step of preparing a second mixture by mixing water; Ii) a second step of preparing a third mixture by mixing the first mixture and the second mixture prepared in the first step; And iii) a third step of preparing a raw material mixture in a slurry state by ultrasonicating the third mixture prepared in the second step, wherein the forming step includes: iv) the raw material mixture prepared in the third step with a mesh belt A fourth step of laminating on; And v) a fifth step of dehydrating the raw material mixture stacked on the mesh belt.

In the method for manufacturing carbon fiber paper for GDL according to the present invention, after the fifth step, it may further include a sixth step of vi) hot air drying.

In the method for manufacturing carbon fiber paper for GDL according to the present invention, the organic solvent is ethanol, the thickener is carboxyl methyl cellulose, and the binder is polyvinyl alcohol. do.

According to the method of manufacturing carbon fiber paper for GDL of the present invention, since the carbon fiber is dispersed through ultrasonic treatment, the injection amount of the thickener can be minimized, and as a result, a carbon paper having a uniform thickness, breathability, and excellent electrical conductivity can be produced. It has the advantage of being able to.

1 is a flowchart illustrating a method of manufacturing carbon fiber paper for GDL according to an embodiment of the present invention.
2 is a block diagram of an apparatus for manufacturing carbon fiber paper for GDL according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention and the drawings, which will be described in detail enough to allow those of ordinary skill in the art to easily implement the present invention. For this purpose, it does not mean that the technical spirit and scope of the present invention are limited thereby.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

1 is a flowchart illustrating a method of manufacturing carbon fiber paper for GDL according to an embodiment of the present invention. As shown in Figure 1, the method of manufacturing a carbon fiber paper for GDL according to the present invention comprises the steps of mixing an organic solvent, carbon fiber, a thickener, a binder, and water; And shaping.

Specifically, the step of mixing an organic solvent, carbon fiber, a thickener, a binder, and water includes: i) a first mixture of a first mixture of carbon fibers mixed with an organic solvent, a thickener, a binder, and water to prepare a second mixture. Step, ii) a second step of preparing a third mixture by mixing the first mixture and the second mixture prepared in the first step, and iii) the third mixture prepared in the second step is ultrasonically treated to form a raw material in a slurry state. And a third step of preparing the mixture.

And the forming step includes: iv) a fourth step of laminating the raw material mixture prepared in the third step on a mesh belt, v) a fifth step of dewatering the raw material mixture stacked on the mesh belt, and ⅵ) hot air drying. It consists of six more steps.

Explaining the above steps in more detail, i) the first step is a step of preparing a first mixture and a second mixture, and the first mixture is prepared by mixing carbon fibers in an organic solvent. Here, the organic solvent may be one or two or more selected from organic solvents such as hydrocarbon-based, halogenated refractory hydrogen-based, aromatic chlorinated hydrocarbon-based, alcohol-based, aldehyde-based, ether ester-based, ketone-based, glycol ether-based organic solvent. And, preferably, ethanol.

The carbon fiber is manufactured using polyaconitrile as a precursor and is preferably chopped to have a length of 1 to 12 mm and a diameter of 1 to 10 μm, and this is to minimize surface tension in a solvent to maintain dispersibility. The first mixture composed of the above configuration is stirred in a stirrer.

The second mixture is prepared by mixing a thickener, a binder, and water. Here, it is preferable that the thickener is carboxyl methyl cellulose. The binder is preferably any one of polyvinyl alcohol, vinyl acetate (PVAC), and acrylate, and polyvinyl alcohol having a length of 3 mm and a diameter of 2 μm is used as 4 carbon fibers. It is more preferable to add it in a proportion of ~6% by weight.

The second mixture composed of the above configuration is stirred in a stirrer.

Ii) The second step is a step of preparing a third mixture by mixing the first mixture and the second mixture, and may be stirred under the same conditions as the first step.

Iii) The third step is a step of preparing a raw material mixture in a slurry state by ultrasonically treating the third mixture prepared in the second step. With the use of ultrasonic waves, even if a small amount of a thickener is added, carbon fibers are evenly dispersed throughout the mixture, so that it is possible to obtain carbon fiber paper having a uniform thickness, air permeability and excellent electrical conductivity.

Here, the ultrasonic wave is preferably adjusted to 20 ~ 200kHz.

Step iv) is a step of laminating the raw material mixture in a slurry state prepared in step iii) on a mesh belt, and as an example, the manufacturing apparatus shown in FIG. 2 may be used.

Specifically, the raw material mixture prepared in step iii) is transferred to the hopper 100 by a pump (not shown), and the spray nozzle 110 connected to one side of the hopper 100 is a mesh belt moving at a predetermined speed. (200) Spray the raw material slurry mixture to the top.

Here, it is preferable that the spray nozzle 110 of the hopper 100 is located inside the head box 300 forming a separate space by being blocked from the outside.

The step v) is a step of dehydrating the raw material mixture stacked on the mesh belt 200, and may include a first dehydration step and a second dehydration step.

Specifically, in the first dehydration step, at the moment when the raw material mixture is stacked on the mesh belt 200, the raw material mixture is dehydrated with the first vacuum dewatering device 310 located on the lower surface of the mesh belt 200, which is the opposite surface on which the raw material mixture is stacked. In this case, the vacuum pressure is preferably 50 to 80 cmHg.

If the primary dehydration is performed at the moment when the raw material mixture is stacked on the mesh belt 200 as described above, the load applied to the mesh belt 200 can be reduced, thereby reducing the maintenance cost of the device, especially the primary dehydration. Since the fiber is bonded by the mesh belt 200, even if the mesh belt 200 moves slightly inclined, the stacked raw material slurry mixture is maintained as it is, thereby obtaining a filter having a uniform thickness.

The second dehydration step is a step of further lowering the moisture of the raw material slurry mixture that has been dehydrated and at the same time inducing more dense bonding between the fibers, and a second vacuum dewatering device 400 located behind the first vacuum dewatering device 310 ), and natural gravity equation is also possible, but it is preferable to dehydrate under reduced pressure with a vacuum pressure of 10 to 40 cmHg.

Step ⅵ) is a step of hot air drying. In the dehydration step, as a step of completely drying some residual moisture to obtain a filter, it is preferable to perform hot air drying in a drying apparatus 600 maintained at a temperature of 100 to 150°C.

Thereafter, if necessary, it may be wound with the winding device 700, and any one or more of the step of additionally stacking the raw material slurry mixture on the mesh belt, the dehydration step, and the pressure step hot air drying step may be repeatedly performed.

So far, the present invention has been looked at around its preferred embodiments. Those of ordinary skill in the art to which the present invention pertains will be able to understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative point of view rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the above description, and the scope equivalent thereto should be construed as being included in the present invention.

100: hopper
110: injection nozzle
200: mesh belt
300: head box
310: first decompression dehydration device
400: second decompression dehydration device
500: pressure roller
600: drying device
700: winding device

Claims (4)

Mixing an organic solvent, carbon fiber, a thickener, a binder, and water; And
GDL carbon fiber paper manufacturing method comprising the step of molding.
The method of claim 1,
The step of mixing the organic solvent, carbon fiber, thickener, binder, and water,
I) a first step of preparing a second mixture by mixing a first mixture in which carbon fibers are mixed in an organic solvent, a thickener, a binder, and water;
Ii) a second step of preparing a third mixture by mixing the first mixture and the second mixture prepared in the first step; And
Iii) a third step of preparing a raw material mixture in a slurry state by ultrasonicating the third mixture prepared in the second step,
The forming step,
Iv) a fourth step of laminating the raw material mixture prepared in the third step on a mesh belt; And
V) A method for producing carbon fiber paper for GDL, comprising a fifth step of dehydrating the raw material mixture stacked on the mesh belt.
The method of claim 2,
After the fifth step,
Ⅵ) GDL carbon fiber paper manufacturing method, characterized in that it further comprises a sixth step of hot air drying.
The method of claim 2,
The organic solvent is ethanol, the thickener is carboxyl methyl cellulose, and the binder is polyvinyl alcohol.

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