Method for improving the water dispersibility of conductive carbon powder and method for producing 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 method includes a step of exposing conductive carbon powder to a plasma jet or reacting it with a plasma-treated reactive gas, and the step is characterized by reacting the plasma-treated reactive gas (ionized gas) with the conductive carbon powder. By using plasma, the water dispersibility of the conductive carbon powder can be easily improved.

Description

[Technical field]

[0001] The present invention relates to a method for improving the hydrophilicity and water dispersibility of conductive carbon powder by utilizing carbon dioxide plasma, and a method for producing a colloidal solution of conductive carbon powder. [Background technology]

[0002] Conductive carbon powder has excellent properties such as high conductivity and oxidation resistance, and is used in many fields. Its surface is lipophilic, and it is mainly used in non-aqueous non-polar solvents. However, when it is used in fields such as secondary battery electrodes, paints, and printing inks, and is used together with an aqueous solution, it is necessary for it to have high dispersibility in the aqueous solution, so hydrophilic surface treatment of the powder is essential.

[0003] A typical hydrophilic treatment method for carbon powder is a chemical liquid phase treatment method. Carbon powder is immersed in a treatment solution such as acetic acid, nitric acid, or hydrogen peroxide, and reacted to bind hydroxyl or amino groups, thereby providing hydrophilic functional groups to the surface. However, this method has the disadvantage of being economically inefficient since the surface treatment method is very strict and many processes such as a purification process to remove residual substances and a drying process must be performed. Another method is an ozone treatment method in which the surface is treated in an ozone gas atmosphere, but the strong oxidizing properties of ozone cause the surface of the carbon powder to be modified. Specifically, pure 100% O 2 When only oxygen is used, high concentration ozone is generated, but when the generated ozone comes into contact with the conductive carbon powder through stirring, the surface is deteriorated, causing a problem of burning. Summary of the Invention [Problem to be solved by the invention]

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

[0005] Another object of the present invention is to provide a method for producing a colloidal solution in which conductive carbon powder is stably dispersed. [Means for solving the problem]

[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 improve the water dispersibility of conductive carbon powder very easily compared to the conventional techniques, and can improve the water dispersibility of conductive carbon powder very easily with only a simple process of exposing conductive carbon powder to a plasma jet or reacting it with a plasma-treated reactive gas. In other words, the present invention can achieve the effect that the water dispersibility of conductive carbon powder is significantly improved by only reacting it with a plasma-treated active gas.

[0007] The present invention is characterized in that the conductive carbon powder is not placed in the plasma generation area and directly exposed to the plasma generated, but rather the plasma-treated gas is moved and exposed to the conductive carbon powder, thereby causing the reaction. Here, the plasma jet means that the plasma generated in the plasma generation area is ejected in the form of a jet into the atmosphere.

[0008] Generally, plasma treatment means placing a workpiece in a plasma generation area and reacting with the workpiece, but in the present invention, plasma treatment means exposing the workpiece to the carbon powder using plasma-treated ionized gas, rather than placing carbon powder in the plasma generation area and directly exposing it. It may be thought that placing conductive carbon powder in the plasma generation area and directly exposing it to the plasma is a more effective method, but the applicant has experimentally confirmed that when the conductive carbon powder is directly exposed to the plasma generation area, the carbon powder reacts with the plasma, causing defects in the carbon powder. Therefore, in the present invention, in order to modify the characteristics of the conductive carbon powder very stably without defects, a process of exposing the conductive carbon powder to a plasma jet or reacting with a plasma-treated reactive gas can be used.

[0009] The conductive carbon powder that can be used in the present invention may be a material consisting of only carbon atoms. For example, it may be graphene, graphite, carbon nanotube (TNT), carbon black, Ketjen black, and Denka black. The present invention does not limit the size or pattern of the conductive carbon powder. Preferably, the conductive carbon powder may be particles having a size of several nanometers to several hundred micrometers, but the conductive carbon powder may have a larger or smaller size without being significantly limited in carrying out the present invention. In addition, the conductive carbon powder may have a shape such as a sphere, a tetrahedron, a cube, an octahedron, etc., but is not necessarily limited thereto.

[0010] The plasma may be carbon dioxide plasma. Generally, plasma is produced using a mixed gas in which materials such as oxygen, nitrogen, and hydrogen are mixed in a specific ratio. In the present invention, it has been confirmed that when 100% carbon dioxide plasma is used, the carbon powder is more significantly water-dispersible than when oxygen, nitrogen gas, or a mixed gas is used. When a mixed gas is used, the carbon powder may be water-dispersible, but it cannot be stably maintained in a colloidal state dispersed in an aqueous solvent as in the present invention, and there is also a significant difference in the duration of the colloid. This will be described in detail through the following examples and comparative examples.

[0011] The method of generating the plasma may be a method such as a dielectric barrier discharge, a corona discharge, a microwave discharge, an arc discharge, etc., and may be preferably a dielectric barrier discharge (DBD), but is not necessarily 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 without causing modification or defects on the surface of the conductive carbon powder.

[0013] Conventional conductive carbon powders are generally used in many fields of application, but when dispersed in an aqueous solvent, the carbon powders tend to aggregate together or are not easily dispersed even when physically stirred unless they are surface-treated due to their hydrophobic properties. Therefore, the conductive carbon powders must be surface-treated. However, the surface treatment process is complicated and the carbon powder crumbles very easily.

[0014] The colloid manufacturing method of the present invention is a method that can solve these problems, and is manufactured by exposing conductive carbon particles to a plasma jet or reacting them with a plasma-treated reactive gas, and adding the obtained conductive carbon colloid powder to an aqueous solvent and stirring it. The conductive carbon colloid powder obtained by reacting with the plasma is dispersed in the solvent to some extent even when added to the aqueous solvent without stirring, and a colloid solution in which the eh powder is stably dispersed without aggregation can be manufactured by simply stirring by hand shaking a sealed container containing the colloid powder and the aqueous solvent. Effect of the Invention

[0015] According to the present invention, the water dispersibility of carbon powder can be stably improved without defects through carbon dioxide plasma treatment, and the carbon powder can be continuously and stably dispersed in an aqueous solvent, and the excellent water dispersibility allows the carbon powder to be applied in various fields. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating a method for improving the water dispersibility of conductive carbon powder and a method for producing a colloidal solution of conductive carbon powder according to the present invention. [Diagram 2] 1 is a diagram illustrating a method for improving the water dispersibility of conductive carbon powder and a method for producing a colloidal solution of conductive carbon powder according to the present invention. [Diagram 3] 1 is a diagram for explaining an embodiment of the present invention; [Figure 4] 1 is a photograph showing a state immediately after carbon powder prepared according to an embodiment of the present invention is put into water; [Diagram 5] 1 is a photographed image showing a state after carbon powder prepared according to an embodiment of the present invention is added to water and stirred by applying physical force; [Figure 6]1 is a graph showing the experimental results of the water dispersibility stability characteristics of the carbon powder prepared according to the embodiment of the present invention over time, which shows that the plasma-treated conductive carbon powder remains stably dispersed in water even after 60 minutes. [Figure 7] 13 is a diagram showing the water dispersibility characteristics of a comparative example using mixed gas plasma according to the present invention. [Figure 8] 1 is a diagram illustrating a layer separation rate experiment of a carbon powder manufactured according to an embodiment of the present invention. [Figure 9] 1 is a graph showing the experimental results of layer separation speed of the carbon powder prepared according to the embodiment of the present invention, which shows that the layer separation speed of the plasma-treated carbon powder is about 3 to 4 times lower than that of the untreated carbon powder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention can be modified in various ways and can have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, but it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention. In describing each drawing, the same reference numerals are used for the same components.

[0018] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to specify the presence of features, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or additional possibility of one or more other features, steps, operations, components, parts, or combinations thereof.

[0019] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

[0020] 1 and 2 are diagrams illustrating a method for improving the water dispersibility of conductive carbon powder and a method for producing a colloidal solution of conductive carbon powder according to the present invention.

[0021] 1 and 2, the method for improving the water dispersibility of conductive carbon powder and the method for preparing a colloidal solution of conductive carbon powder according to the present invention may include a step of exposing conductive carbon powder to a plasma jet or reacting it with a plasma-treated reactive gas. The plasma jet means that plasma generated in a plasma generation region is jet-like ejected into the atmosphere, and the present invention is characterized in that in the step, the conductive carbon powder is not directly exposed to the generated plasma and reacted with it, but reacted with a plasma-treated active gas. If the conductive carbon powder is placed in the plasma generation region and reacted directly, the generated plasma and the conductive carbon powder react with each other, which tends to cause defects in the carbon powder. Therefore, the present invention can react with the conductive carbon powder using a plasma-treated reactive gas or an active gas, which is not the generated plasma.

[0022] Referring to Fig. 1, a conductive carbon powder plasma treatment method is shown in which conductive carbon powder is reacted with plasma-treated reactive gas. To explain this in detail, first, plasma is generated after injecting plasma generating gas into a plasma reactor, and the plasma-treated reactive gas or ionized gas is transferred to a container in which conductive carbon powder is placed and reacted with the carbon powder. At this time, the reaction can be performed by vortex rotation.

[0023] Next, another method of plasma treatment of conductive carbon powder will be described with reference to FIG. 2. Referring to FIG. 2, the water dispersibility of the carbon powder can be improved by exposing the conductive carbon powder to a plasma jet. Here, the plasma can be 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 electrodes, a plasma is formed between the parallel electrodes, and a plasma-treated reactive gas or an ionized gas can be ejected in the direction in which the carbon powder is placed to react with the carbon powder.

[0024] The shape and size of the conductive carbon powder are not particularly limited, but the conductive carbon powder may be a powder of a size of several tens of nanometers and may be spherical.

[0025] Meanwhile, 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 the carbon powder can be effectively improved compared to when a mixed gas containing nitrogen and oxygen is used.

[0026] During the above step, the carbon dioxide plasma treated reactant gas is ionized to form CO, CO 3 Radicals can be generated, which react with the surface of the conductive carbon powder to form functional groups exhibiting hydrophilicity, such as CO, C=O, and C-OOH, on the surface of the conductive carbon powder. Thus, the conductive carbon powder plasma-treated by the method of the present invention can exhibit hydrophilicity through this process, thereby improving the water dispersibility of the conductive carbon powder.

[0027] The reaction time of the plasma and the carbon powder, i.e., the plasma treatment, may be performed for about 10 to 30 minutes, but the present invention does not limit the plasma treatment time as long as it is a sufficient time to impart dispersibility to the conductive carbon powder without causing any modification or defects on the surface of the conductive carbon powder.

[0028] The carbon powder that has been plasma-treated through the above steps can be added to an aqueous solvent and stirred to prepare a carbon powder colloidal solution. Compared to carbon powder that has not been plasma-treated, the plasma-treated carbon powder can be dispersed in the aqueous solvent immediately after being added, but a colloidal solution in which the carbon powder is more effectively dispersed can be prepared by stirring. The stirring method is not particularly limited as long as it can disperse the carbon powder in the solvent. For example, the stirring can be performed using a magnet bar or a method such as a rotary or vertical reciprocating stirrer.

[0029] According to the present invention, it is possible to impart water dispersibility and hydrophilicity to conductive carbon powder by using plasma in a simpler manner than the conventional techniques, and this can be effectively applied to fields in which conductive carbon powder is used.

[0030] The present invention will be described in more detail with reference to the following specific examples and comparative examples. However, the examples are merely some of the embodiments of the present invention, and the scope of the present invention is not limited to the following examples.

[0031] Working Example

[0032] FIG. 3 is a diagram for explaining an embodiment of the present invention.

[0033] Referring to FIG. 3, in the embodiment of the present invention, conductive carbon powder (Ketjen black, KB600 JD) having a size of about 30 to 40 nm is placed in a reactor, and a plasma activated gas generator (30 Hz, 0.8 kW, CO) using a multi-stage DBD electrode is used. 2 Gas: 1 lpm, 100% CO2 After generating the plasma, the generated CO 2 The plasma was transferred to a reaction chamber and reacted with the conductive carbon powder for about 30 minutes, after which the conductive carbon powder was obtained.

[0034] 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, a non-plasma-treated conductive carbon powder was added to a container filled with water, and the water dispersibility of each was confirmed. The results are shown in Figure 4.

[0035] Referring to FIG. 4, the state immediately after each conductive carbon powder was put into water is shown. Here, the non-plasma-treated carbon powder (left side) is not dispersed and floats on the water, while the plasma-treated carbon powder (right side) is well dispersed in the water, which is a solvent. Through this, the carbon powder can be seen to be CO 2 It can be seen that the water dispersibility was improved through the plasma treatment.

[0036] Next, the containers containing each carbon powder were physically shaken (hand shaking) and their water dispersibility was checked. The results are shown in Figure 5.

[0037] Referring to FIG. 5, it can be seen that the non-plasma-treated carbon powder (left side) floats on the water or is not easily dispersed even when physically stirred, whereas the plasma-treated carbon powder (right side) is well dispersed in the water, with no carbon powder remaining at the bottom of the container or on top of the water.

[0038] To confirm the water dispersibility maintenance characteristics over time of the plasma-treated conductive carbon powder, the plasma-treated conductive carbon powder was added to a container filled with water as a solvent, physically dispersed in the water (hand shaking), and the layer separation difference over time (3, 10, 20, 30, 40, 50, and 60 minutes) was photographed. For comparison, the layer separation difference was photographed after carrying out the same process as above for non-plasma-treated conductive carbon powder, and the results are shown in Figure 6.

[0039] 6, it can be seen that the plasma-treated conductive carbon powder remains stably dispersed in water even after 60 minutes, while the non-plasma-treated conductive carbon powder remains partially floating on the water even after stirring, and after about 10 minutes, the dispersed carbon powder begins to sink to the bottom. After about 60 minutes, it can be seen that most of the carbon powder is not dispersed in water and sinks to the bottom of the glass. Thus, it can be seen that the plasma-treated conductive carbon powder according to the method of the present invention has the property of stably maintaining water dispersibility over time.

[0040] Comparative Example

[0041] Nitrogen (N 2 ) / Air mixed gas plasma (N 2 A plasma-treated carbon powder according to a comparative example of the present invention was obtained by carrying out the same process as in the example of the present invention, except that the ratio of 1 / 0.033Ipm / air was used, and the oxygen concentration in the mixed gas was 0.66%. In order to confirm the water dispersibility of the conductive carbon powder obtained above, it was dispersed in water and then the layer separation difference over time (10 and 30 minutes) was photographed. The results are shown in Figure 7.

[0042] Referring to Figure 7, when examining the colloidal solution after 10 minutes (left) and 30 minutes (right), it can be seen that only a small amount of carbon powder is dispersed in the water in the colloidal solution, with the majority either sinking to the bottom or floating on the water. Also, compared to Figure 6, it can be seen that the carbon powder treated with mixed gas plasma separates into layers over time much faster than the carbon powder treated with carbon dioxide plasma. This shows that when treated with mixed gas plasma, it is difficult to see that the carbon powder has water dispersibility, and it is difficult to see that it continues to have water dispersibility.

[0043] Additionally, the light absorbance of the plasma-treated conductive carbon powder was measured over time to specifically confirm the phase separation rate. For comparison, the phase separation rate of a non-plasma-treated conductive carbon powder was also measured and compared. The apparatus used to measure the phase separation rate is shown in FIG. 8, and the measurement of the light absorbance will be described in detail with reference to FIG. 8.

[0044] Referring to FIG. 8, the optical absorbance measurement shows that CO 2 Plasma-treated and non-plasma-treated carbon powders were added to water, and the phase separation over time was measured using an optical emission spectrometer (OES). Average values ​​of 10 samples were taken at a height of about 1 cm from the bottom of the cuvette in the 550-700 nm wavelength band and compared. The results are shown in Figure 9.

[0045] 9, it can be seen that the layer separation rate of the plasma-treated carbon powder is about 3 to 4 times lower than that of the untreated carbon powder. This shows that when the conductive carbon powder is treated using the method of the present invention, the layers do not separate even after being dispersed in a solvent, and the powder can be continuously dispersed.

[0046] Although the present invention has been described above with reference to preferred embodiments thereof, it should be understood that those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention as set forth in the claims.

Claims

1. The method includes injecting a plasma-treated reaction gas generated in a plasma reactor installed separately from the reaction vessel into a reaction vessel having conductive carbon powder disposed in an internal reaction space thereof so that the conductive carbon powder is not directly exposed to plasma, and reacting the conductive carbon powder with the plasma-treated reaction gas, The method for improving the water dispersibility of a conductive carbon powder, wherein the plasma-treated reactive gas is 100% carbon dioxide plasma.

2. 2. The method of claim 1, wherein the plasma is DBD (dielectric barrier discharge) plasma.

3. 2. The method for improving the water dispersibility of conductive carbon powder according to claim 1, wherein the reaction time between the plasma-treated reactive gas and the conductive carbon powder is 10 to 30 minutes.

4. 2. The method of claim 1, wherein the conductive carbon powder is any one selected from the group consisting of graphene, graphite, carbon nanotubes (CNT), carbon black, Ketjen black, and Denka black.

5. A first step of injecting a plasma-treated reaction gas generated in a plasma reactor installed separately from the reaction vessel into a reaction vessel having conductive carbon particles disposed in an internal reaction space thereof so that the conductive carbon particles are not directly exposed to plasma, and reacting the conductive carbon particles with the plasma-treated reaction gas to obtain a conductive carbon colloid powder; and A second step of preparing a carbon powder colloidal solution by adding the conductive carbon colloidal powder to an aqueous solvent and stirring the mixture; The method for preparing a carbon powder colloidal solution, wherein the plasma-treated reaction gas is 100% carbon dioxide plasma.

6. 6. The method for preparing a carbon powder colloidal solution according to claim 5, wherein the plasma is DBD (dielectric barrier discharge) plasma.

7. 6. The method for preparing a carbon powder colloidal solution according to claim 5, wherein the reaction time between the plasma-treated reaction gas and the conductive carbon particles is 10 to 30 minutes.

8. 6. The method of claim 5, wherein the conductive carbon particles are any one selected from the group consisting of graphene, graphite, carbon nanotubes (CNT), carbon black, Ketjen black, and Denka black.

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