Method for improving water dispersibility of conductive carbon powder and method for preparing colloidal solution of conductive carbon powder

Abstract

The present invention discloses a method for improving the water dispersibility of conductive carbon powder and a method for preparing a colloidal solution of conductive carbon powder. The present invention includes the steps of exposing the conductive carbon powder to a plasma jet or reacting with a plasma-treated reaction gas, wherein the step is characterized in that the plasma-treated reaction gas (ionized gas) reacts with the conductive carbon powder, and the water dispersibility of the conductive carbon powder can be easily improved by using plasma.

Description

Technical Field

[0001] The invention relates to a method for improving the hydrophilicity and water dispersibility of conductive carbon powder by using carbon dioxide plasma and a method for preparing a colloid solution of conductive carbon powder. Background Art

[0002] Conductive carbon powder has excellent properties such as high conductivity and oxidation resistance, so it is used in many fields. And because the surface is lipophilic, it is mainly used in non-aqueous non-polar solvents. However, when used in the fields of secondary battery electrodes, coatings, printing inks, etc., it is necessary to improve the dispersibility of the aqueous solution when used with aqueous solutions. Therefore, the powder must be treated with hydrophilic surface.

[0003] A representative method for treating carbon powder to be hydrophilic is a chemical liquid treatment method. The carbon powder is immersed in a treatment liquid such as acetic acid, nitric acid, or hydrogen peroxide to react, so that hydroxyl groups or amino groups are bonded, thereby imparting hydrophilic functional groups to the surface. However, this method has the disadvantage of poor economic benefits because the surface treatment method is very complicated and requires many processes such as a purification process to remove residues and a drying process. As another method, there is an ozone treatment method for surface treatment under an ozone atmosphere, but there is a problem of denaturing the surface of the carbon powder due to the strong oxidizing properties of ozone. Specifically, when only pure 100% carbon dioxide (O2) (oxygen) is used, a high concentration of ozone will be generated. When the generated ozone is stirred and contacted with the conductive carbon powder, the surface will deteriorate and a burning phenomenon (burning) will occur. Summary of the invention

[0004] An object of the present invention is to provide a method for easily improving the water dispersibility of carbon powder by using carbon dioxide plasma only through a simple process.

[0005] Another object of the present invention is to provide a method for preparing a colloidal solution in which conductive carbon powder is stably and well dispersed.

[0006] The method for improving the water dispersibility of conductive carbon powder to achieve one object of the present invention is a novel method that can easily improve the water dispersibility of conductive carbon powder compared to the prior art, and the method can easily improve the water dispersibility of conductive carbon powder by a simple process of exposing the conductive carbon powder to a plasma jet or reacting with a plasma-treated reactive gas. In other words, according to the present invention, the water dispersibility of conductive carbon powder can be significantly improved by reacting with a plasma-treated reactive gas alone.

[0007] The present invention is characterized in that the conductive carbon powder is not directly exposed to the formed plasma after being arranged in the plasma generation area for reaction, but the plasma-treated gas is moved and exposed to the conductive carbon powder for reaction. Here, the plasma jet refers to the plasma generated in the plasma generation area being ejected into the atmosphere in a jet shape.

[0008] Generally speaking, plasma treatment refers to placing the treated object in a plasma generating area and then reacting it. However, in the present invention, plasma treatment does not mean directly placing the carbon powder in the plasma generating area and exposing it directly, but refers to exposing the carbon powder to the ionized gas treated with plasma. Although it is believed that it is more effective to place the conductive carbon powder in the plasma generating area and then directly expose it to the plasma, the applicant has confirmed through experiments that when directly exposed to the plasma generating area, the carbon powder reacts with the plasma and defects occur in the carbon powder. Therefore, in the present invention, in order to improve the properties of the conductive carbon powder very stably without defects, a process of exposing it to a plasma jet or reacting it with a plasma-treated reactive gas can be used.

[0009] The conductive carbon powder that can be used in the present invention can be a material composed only of carbon atoms. For example, graphene, graphite, carbon nanotubes (TNT), carbon black, Ketjenblack, and acetylene black (Denka black) can be used. In the present invention, the size or shape of the conductive carbon powder is not limited. Preferably, the conductive carbon powder can be particles with a particle size of several nanometers to hundreds of microns, but even if the size is larger or smaller than the size, there is no particular limitation when implementing the present invention. In addition, the conductive carbon powder can have a sphere, a tetrahedron, a cube, an octahedron, etc., but is not limited thereto.

[0010] The plasma may be a carbon dioxide plasma. Usually, plasma uses a mixed gas of materials such as oxygen, nitrogen, and hydrogen mixed at a specific ratio, but in the present invention, it is confirmed that when 100% carbon dioxide plasma is used, the water dispersibility of carbon powder is significantly improved compared to when oxygen, nitrogen, or a mixed gas is used. When a mixed gas is used, although water dispersibility can be formed in carbon powder, it is impossible to stably maintain a colloidal state dispersed in a water-based solvent as in the present invention, and there is also a significant difference in the duration of the colloidal state. This is described in detail through the following embodiments and comparative examples.

[0011] The plasma may be generated by dielectric barrier discharge, corona discharge, microwave discharge, arc discharge, etc., but preferably, dielectric barrier discharge (DBD) plasma may be used. However, the present invention is not limited thereto.

[0012] The plasma treatment may be performed for 10 to 30 minutes. In the present invention, the plasma treatment time is not limited as long as it is a sufficient time to impart dispersibility within a range where the surface of the conductive carbon powder is not denatured or scratched.

[0013] Generally, existing conductive carbon powder is used in various application fields, but when it needs to be dispersed in a water-based solvent for application, due to the hydrophobic nature of the carbon powder, if it is not subjected to a surface treatment process, the carbon powder will agglomerate with each other or cannot be well dispersed even with physical stirring. Therefore, the conductive carbon powder must be subjected to a surface treatment process. However, there are problems such as the surface treatment process being complicated or the carbon powder being very easy to break.

[0014] The colloid preparation method of the present invention is a method capable of solving these problems, and the conductive carbon particles are exposed to a plasma jet or reacted with a plasma-treated reaction gas, and the obtained conductive carbon colloid powder is added to a water-based solvent and stirred. The conductive carbon colloid powder obtained by the plasma reaction will show a state of being dispersed in the solvent to a certain extent even if it is added to the water-based solvent without stirring, and a stably dispersed colloid solution can be prepared without agglomeration of eh powder only by simple stirring of hand shaking of a sealed container containing the colloid powder and the water-based solvent.

[0015] Effects of the Invention

[0016] According to the present invention, the water dispersibility of carbon powder can be stably improved by carbon dioxide plasma treatment without any defects, and the carbon powder can be continuously and stably dispersed in a water-based solvent. Therefore, the physical properties obtained due to the excellent water dispersibility can be applied to various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 and Figure 2 It is a diagram for explaining the method for improving the water dispersibility of the conductive carbon powder and the method for preparing the colloidal solution of the conductive carbon powder according to the present invention.

[0018] Figure 3 It is a figure for demonstrating the Example of this invention.

[0019] Figure 41 is a diagram showing an image taken immediately after the carbon powder prepared according to the example of the present invention was put into water.

[0020] Figure 5 The figure shows an image of a state where the carbon powder prepared according to an example of the present invention is put into water and then stirred by applying physical force.

[0021] Figure 6 : is a graph showing the results of a water dispersibility safety characteristic test of the carbon powder prepared according to an example of the present invention over time. It can be confirmed that the plasma-treated conductive carbon powder remains stably dispersed in water even after 60 minutes.

[0022] Figure 7 This is a graph showing the results of water dispersibility characteristics of a comparative example using the mixed gas plasma of the present invention.

[0023] Figure 8 1 is a diagram for explaining a layer separation speed experiment of carbon powder prepared according to an example of the present invention.

[0024] Fig. 9 is a graph showing the experimental results of the layer separation rate of the carbon powder prepared according to the embodiment of the present invention. It can be confirmed that the layer separation rate of the plasma-treated carbon powder is reduced by about 3 to 4 times compared with the untreated carbon powder. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The present invention can be modified in many ways and can have many forms, so specific embodiments are illustrated in the drawings and described in detail in this specification. However, it should be understood that this does not limit the present invention to a specific disclosure method, but includes all modifications, equivalent technical solutions and alternative solutions included in the concept and technical scope of the present invention. When describing the drawings, similar components are marked with similar reference numerals.

[0026] The terms used in this application are only used to illustrate specific embodiments and are not intended to limit the present invention. Unless the context clearly indicates a different meaning, a singular expression includes a plural expression. In this application, terms such as "including" or "having" are used to specify the existence of features, steps, actions, constituent elements, parts, or combinations thereof recorded in the specification, and shall not be understood as excluding in advance the existence or additional possibility of one or more other features or steps, actions, constituent elements, parts, or combinations thereof.

[0027] Unless otherwise defined, all terms used in this application, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the invention belongs. Terms defined in commonly used dictionaries should be interpreted as having the same meaning as that in the context of the relevant art, and, unless explicitly defined in this application, should not be interpreted in an idealized or overly formalized sense.

[0028] Figure 1 and Figure 2 It is a diagram for explaining the method for improving the water dispersibility of the conductive carbon powder and the method for preparing the colloidal solution of the conductive carbon powder according to the present invention.

[0029] refer to Figure 1 and Figure 2 According to the method for improving the water dispersibility of the conductive carbon powder and the method for preparing the colloidal solution of the conductive carbon powder of the present invention, the conductive carbon powder may include the step of exposing the conductive carbon powder to a plasma jet or reacting with a plasma-treated reactive gas. The plasma jet refers to spraying the plasma generated in the plasma generation area into the atmosphere in a jet shape. In the present invention, in the step, the conductive carbon powder is not directly exposed to the generated plasma for reaction, but reacts with the plasma-treated active gas. When the conductive carbon powder is arranged in the plasma generation area and reacts directly, the generated plasma reacts with the conductive carbon powder, making it easy to produce defects in the carbon powder. Therefore, in the present invention, a plasma-treated reactive gas or an activated gas can be used instead of the generated plasma to react with the conductive carbon powder.

[0030] refer to Figure 1 , a conductive carbon powder plasma treatment method for reacting conductive carbon powder with a plasma-treated reaction gas is shown. Specifically, first, a plasma-generating gas is injected into a plasma reactor, and then plasma is generated, and the plasma-treated reaction gas or ionized gas is moved to a container configured with conductive carbon powder and reacted with the carbon powder. At this time, the reaction can be carried out by vortex rotation.

[0031] Next, refer to Figure 2 , other methods of plasma treatment of conductive carbon powder will be described. Figure 2, the water dispersibility of the conductive carbon powder can be improved by exposing the conductive carbon powder to a plasma jet. Here, the plasma can use a dielectric barrier discharge (DBD) plasma, and the plasma electrode can be composed of two parallel metal electrodes. When a current is applied to the metal electrode, plasma is formed between the parallel electrodes, and the plasma-treated reaction gas or ionized gas is ejected in the direction where the carbon powder is disposed, so that it can react with the carbon powder.

[0032] The shape and size of the conductive carbon powder are not particularly limited. The conductive carbon powder may be a powder with a size of several tens of nanometers and may have a spherical shape.

[0033] In addition, the plasma may be carbon dioxide plasma. Preferably, the plasma may be 100% carbon dioxide plasma. When 100% carbon dioxide plasma gas is used, the water dispersibility of carbon powder can be effectively improved compared with the case of using a mixed gas containing nitrogen and oxygen.

[0034] In the step, the reaction gas treated with carbon dioxide plasma is ionized to generate CO and CO3 free radicals, which react with the surface of the conductive carbon powder to form hydrophilic functional groups such as CO, C=O, C-OOH, etc. on the surface of the conductive carbon powder. Therefore, through the process, the conductive carbon powder treated with plasma according to the method of the present invention can show hydrophilicity, thereby improving the water dispersibility of the conductive carbon powder.

[0035] The reaction time of the plasma and the carbon powder, i.e., the plasma treatment, can be performed for about 10 to 30 minutes. However, in the present invention, the plasma treatment time is not limited as long as it is sufficient to impart dispersibility to the conductive carbon powder without causing surface denaturation and defects on the conductive carbon powder.

[0036] According to the steps, the plasma-treated carbon powder is stirred after adding the conductive carbon colloid powder to a water-based solvent, thereby preparing a carbon powder colloidal solution. Compared with the carbon powder not treated with plasma, the carbon powder treated with plasma can be dispersed in the solvent after adding it to the water-based solvent, but a more effectively dispersed colloidal solution can be prepared by stirring. The stirring is not particularly limited as long as the method can disperse the carbon powder in the solvent. For example, the stirring can be performed using a magnetic rod, or methods such as rotary and vertical reciprocating stirring can be used.

[0037] According to the present invention, water dispersibility and hydrophilicity can be imparted to conductive carbon powder by using plasma in an easier method than in the related art, which can be effectively applied to the fields where the conductive carbon powder is used.

[0038] The present invention is described in more detail below by specific examples and comparative examples. However, the examples of the present invention are only partial examples of the present invention, and the scope of the present invention is not limited to the following examples.

[0039] Example

[0040] Figure 3 It is a figure for demonstrating the Example of this invention.

[0041] refer to Figure 3 In an embodiment of the present invention, conductive carbon powder (Ketjenblack, KB600JD) with a size of about 30 to 40 nm is placed in a reactor, 100% CO2 plasma is generated using a plasma active gas generator (30 Hz, 0.8 kW, 1 lpm of CO2 gas) using a multi-stage DBD electrode, and then the generated CO2 plasma is moved to a reaction chamber and reacted with the conductive carbon powder for about 30 minutes. Then, the conductive carbon powder obtained by the reaction is obtained.

[0042] In order to confirm the water dispersibility of the plasma-treated conductive carbon powder, the powder was added to a container filled with water, and, for comparison, the conductive carbon powder not treated with plasma was added to a container filled with water, and then the water dispersibility was confirmed respectively. The results are shown in Figure 4 .

[0043] refer to Figure 4 , showing the state of each conductive carbon powder just after being put into water, it can be confirmed here that the carbon powder that has not been treated with plasma (left) floats on the water surface without being dispersed, while the carbon powder that has been treated with plasma (right) is well dispersed in the water as a solvent. It can be seen that the water dispersibility of carbon powder can be improved by CO2 plasma treatment.

[0044] Next, the container containing each carbon powder was physically stirred (hand shaking), and then the water dispersibility of each was confirmed. The results are shown in Figure 5 .

[0045] refer to Figure 5 It can be confirmed that even with physical stirring, the carbon powder that has not been treated with plasma (left) appears to float on the water surface or is difficult to disperse, but the carbon powder that has been treated with plasma (right) is well dispersed in the water as a solvent, and there is no carbon powder that is not dispersed at the bottom of the container or in the water.

[0046] In order to confirm the water dispersibility persistence of the plasma-treated conductive carbon powder over time, the plasma-treated conductive carbon powder was added to a container containing water as a solvent, physically dispersed in the water (hand shaking), and the difference in layer separation according to time (3, 10, 20, 30, 40, 50 and 60 minutes) was photographed. In addition, for comparison, the same process as above was performed on the conductive carbon powder that was not plasma-treated, and the difference in layer separation was photographed, and the results are shown in FIG. Figure 6 middle.

[0047] refer to Figure 6 It can be confirmed that the conductive carbon powder treated with plasma remains stably dispersed in water after 60 minutes, while the conductive carbon powder not treated with plasma partially floats on the water after being stirred. After about 10 minutes, the dispersed carbon powder begins to sink to the bottom. After about 60 minutes, most of the carbon powder is not dispersed in water but sinks to the bottom of the glass. It can be seen that the conductive carbon powder treated with plasma by the method of the present invention has the characteristic of stably maintaining water dispersibility over time.

[0048] Comparative Example

[0049] The same process as in the embodiment of the present invention was performed except that nitrogen (N2) / air mixed gas plasma (N2 / air was 1 / 0.033Ipm, and the oxygen concentration in the mixed gas was 0.66%) to obtain the plasma-treated carbon powder according to the comparative example of the present invention. In order to confirm the water dispersibility characteristics of the conductive carbon powder obtained above, the layer separation difference over time (10 minutes and 30 minutes) after dispersion in water was photographed. The results are shown in Figure 7 .

[0050] refer to Figure 7 , observing the colloidal solution after 10 minutes (left) and 30 minutes (right), only a small amount of carbon powder is dispersed in the water, while most of it sinks to the bottom or floats on the water surface. Figure 6 By comparison, it can be seen that the speed of layer separation over time for the carbon powder treated with mixed gas plasma is significantly faster than the speed of layer separation for the carbon powder treated with carbon dioxide plasma. It can be seen that when the mixed gas plasma is used for treatment, it is difficult to see that the carbon powder has water dispersibility and it is difficult to see that it has sustained water dispersibility.

[0051] In addition, the layer separation rate was confirmed by measuring the absorbance of the plasma-treated conductive carbon powder over time. For comparison, the layer separation rate of the conductive carbon powder that was not plasma-treated was also measured and compared. Figure 8 A device for measuring the layer separation speed is shown, referring to Figure 8 Describe absorbance measurements in detail.

[0052] refer to Figure 8 , carbon powder treated with CO2 plasma and carbon powder not treated with plasma were put into water respectively, and then the layer separation over time was measured by optical emission spectrometer (OES). At a height of about 1 cm from the bottom of the cuvette, 10 average values ​​were taken in the 550 to 700 nm band and compared. The results are shown in Fig. 9 .

[0053] refer to Fig. 9 It can be confirmed that the layer separation speed of the plasma-treated carbon powder is reduced by about 3 to 4 times compared with the untreated carbon powder (Untreated). It can be seen that when the conductive carbon powder is treated by the method of the present invention, the layer can be continuously dispersed without separation even after being dispersed in a solvent.

[0054] Although the preferred embodiments of the present invention have been described above, a person skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as described in the claims.

Claims

1. A method for improving the water dispersibility of conductive carbon powder, characterized in that: include: injecting a plasma-treated reaction gas into a reaction chamber, wherein the conductive carbon powder is disposed in the reaction chamber, and the plasma-treated reaction gas is formed in a plasma chamber disposed separately from the reaction chamber so that the conductive carbon powder is prevented from being directly exposed to plasma, and The conductive carbon powder is reacted with the plasma treated reaction gas, wherein the plasma is 100% carbon dioxide plasma.

2. The method for improving water dispersibility of conductive carbon powder according to claim 1, characterized in that: The plasma is a dielectric barrier discharge plasma.

3. The method for improving water dispersibility of conductive carbon powder according to claim 1, characterized in that: The plasma treatment is performed for 10 minutes to 30 minutes.

4. The method for improving water dispersibility of conductive carbon powder according to claim 1, characterized in that: The conductive carbon powder is one selected from graphene, graphite, carbon nanotubes, carbon black, Ketjen black and acetylene black.

5. A method for preparing a carbon powder colloidal solution, characterized in that: include: The first step is to inject a plasma-treated reaction gas into a reaction chamber, wherein the conductive carbon powder is disposed in the reaction chamber, the plasma-treated reaction gas is formed in a plasma chamber disposed separately from the reaction chamber so that the conductive carbon powder is prevented from being directly exposed to plasma, and the conductive carbon powder is reacted with the plasma-treated reaction gas to obtain a conductive carbon colloidal powder, wherein the plasma is 100% carbon dioxide plasma; and In the second step, the conductive carbon colloid powder is added into a water-based solvent and stirred to prepare a carbon powder colloid solution.

6. The method for preparing a carbon powder colloidal solution according to claim 5, characterized in that: The plasma is a dielectric barrier discharge plasma.

7. The method for preparing a carbon powder colloidal solution according to claim 5, characterized in that: The plasma treatment is performed for 10 minutes to 30 minutes.

8. The method for preparing a carbon powder colloidal solution according to claim 5, characterized in that: The conductive carbon powder is one selected from graphene, graphite, carbon nanotubes, carbon black, Ketjen black and acetylene black.

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