KR102254960B1 - Synthetic method of multi-walled carbon nanotubes conductive dispersion liquid using milling process - Google Patents

Abstract

The present invention relates to a method of manufacturing a multi-walled carbon nanotube conductive dispersion using a milling process, and more particularly, to a method of manufacturing a multi-walled carbon nanotube conductive dispersion with improved dispersibility using mechanical milling. To this end, the present invention is the first solution and Ammonium Carbonate ((NH₄)₂CO₃) mixed and stirred with Iron(III) Nitrate Nonahydrate (Fe(NO₃)₃9H₂O) and Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O). After preparing a second solution in which Aluminum Hydroxide (Al(OH)₃) is dissolved, the mixture is stirred, filtered and dried to form a metal catalyst; A synthesis step of synthesizing carbon nanotubes by putting the metal catalyst in a CVD synthesizer; A milling step of putting the carbon nanotubes in a milling device and milling by adding an aqueous dispersant, an antifoaming agent, and a solvent to prepare a carbon nanotube solution; And a dispersion step of dispersing a dispersant, a binder, a co-solvent, a wetting agent, and a solvent in the carbon nanotube solution to prepare a conductive dispersion. It is preferably characterized in that it comprises a.

Description

Synthetic method of multi-walled carbon nanotubes conductive dispersion liquid using milling process

The present invention relates to a method of manufacturing a multi-walled carbon nanotube conductive dispersion using a milling process, and more particularly, to a method of manufacturing a multi-walled carbon nanotube conductive dispersion with improved dispersibility using mechanical milling.

Carbon nanotubes are in the spotlight in a wide variety of fields, such as being used as materials such as electronics, environment, sensors, energy, and displays due to their excellent electrical, mechanical, and optical properties. Carbon nanotubes are nanomaterials that have a one-dimensional shape with a large aspect ratio (length/diameter) in micrometers compared to several nm in diameter, and a unique structure in the form of a tube.It is a modified form of graphite and is wound in a tube shape. The single-walled structure is called a single-walled carbon nanotube, and in the case of a material wound in the form of a multi-layered tube, it is called a multi-walled carbon nanotube.

Because carbon nanotubes are nano-sized particles and have high viscosity, it is difficult to uniformly disperse carbon nanotubes, so it is difficult to properly use their intrinsic properties.In order to improve low dispersibility, van der Waals between tubes is difficult. Agglomeration should be suppressed by breaking the bond.

In addition, when carbon nanotubes are manufactured as a composite with a metal or a polymer, there is a problem in that it is difficult to manufacture a composite due to poor wettability, which is the degree to which liquid spreads over a solid surface. Therefore, in order to make an excellent composite using carbon nanotubes, many studies are being conducted to improve the structure of the composite, such as a method for improving surface modification or a method for dispersing, to suit the purpose.

One of the methods for manufacturing the composite is the mechanical stirring method, which physically functionalizes the surface of the carbon nanotubes with strong shearing force, and has the advantage of improving dispersibility.Therefore, studies on the mechanical stirring method are continuously being conducted. It has been reported that the dispersion state of the nanotubes affects the properties of the composite. In addition, developing a method that can grasp the properties of the physical properties according to the state of carbon nanotube dispersion is an important part of the application of carbon nanotubes. Therefore, the method of milling by effectively dispersing and mixing carbon nanotubes with materials There is a lot of research going on.

Meanwhile, SD (Spray Drying) method, one of the most common methods of converting liquids into powder forms, generates colloidal fluids in the form of fine droplets (sprays) and dry them using a high temperature gas medium. This is the process of obtaining spherical powder particles. In general, a two fluid nozzle is used to obtain a fine powder, and the two fluid nozzle has the advantage of generating droplets of a size of tens to hundreds of microns in large quantities.

The properties of the metal catalyst powders obtained by the SD method largely depend on the pressure of the air-fluid nozzle that injects the fluid and the high temperature gas medium and the properties of the spray solution. By changing these manufacturing conditions, it is possible to manufacture metal catalyst particles having various properties such as dense particles, hollow particles, and particles with many pores. Since the metal catalyst powder prepared by the SD method has a large surface area, and multi-walled carbon nanotube growth nuclei can be formed in front of and behind the metal catalyst, a high carbon nanotube synthesis yield can be obtained, thereby improving productivity.

In the DP method (Deposition precipitation), which is another method of manufacturing a metal catalyst, a precursor salt solution of a metal catalyst and a pH adjuster react in the carrier dispersion to form a precipitate, which is adsorbed and solidified on the surface of the support. The uniformity of the metal catalyst and the synthesis yield of carbon nanotubes are remarkable, which cannot be compared with the metal catalysts prepared by the immersion method and the impregnation method, so it can be said to be the most suitable method for the production of a metal catalyst for producing carbon nanotubes.

In addition, in order to minimize the distribution of the length and diameter of the carbon nanotubes, a ball milling treatment, which is one of the mechanical milling treatment processes, may be used. The increase in contact between the carbon nanotubes and the bendng bond of the carbon nanotubes through the ball milling process changes the electrical properties of the carbon nanotubes, thereby increasing the resistance of the multi-walled carbon nanotubes. The length decreases exponentially. Since carbon nanotubes with such a short length have excellent dispersing power, they are suitable for preparing dispersions. Therefore, ball milling is considered an effective process that can disperse carbon nanotubes or mix them with other materials to make them complex. In addition, since there is an advantage of further increasing the convenience of storage and use of carbon nanotube materials, many studies have been conducted on this.

There are various milling methods such as attritor mill, horizontal mill, vibration mill, horizontal mill, etc. for these milling methods, and very different results can be obtained depending on the device. In the case of the wet milling process of carbon nanotubes, water-based milling treatment and organic milling Since the conditions of each researcher such as the process of additives such as treatment and working process conditions are different, various and systematic studies are required.

Dispersant is a generic term for surfactants generally used in applications requiring a dispersing action, and those exhibiting a dispersing effect by giving a remarkable change in the properties of solids and liquids are called dispersants. The dispersant has the function of wetting the solid particles in the dispersion medium, aiding in grinding and preventing re-aggregation of the particles. Important factors affecting the stabilization of dispersion include the type and concentration of the dispersant, and the dispersant is adsorbed on the surface of the solid particles and has a charge or causes a steric stabilization effect to prevent agglomeration due to collisions between solid particles. do.

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In order to solve the above-described problem, the method of manufacturing a multi-walled carbon nanotube conductive dispersion using a milling process according to the present invention is made through a milling process for carbon nanotubes so that the carbon nanotubes can be applied to various applications. In preparing a carbon nanotube dispersion, the purpose is to find and provide conditions that can achieve the most ideal dispersion and combination.

Another object of the present invention is to synthesize a multi-walled carbon nanotube using a metal catalyst prepared by the DP method or the SD method, and then apply a mechanical milling treatment for a certain period of time to obtain a conductive dispersion of multi-walled carbon nanotubes with improved dispersibility. It is an object of the present invention to provide a manufacturing method.

Another object of the present invention is to provide a method for preparing a dispersion in which a multi-walled carbon nanotube conductive dispersion is easily mixed with other materials and has increased wettability.

The technical problem to be achieved by the present invention is not limited to the technical problems mentioned above, and other technical problems that are not mentioned can be clearly understood by those of ordinary skill in the technical field to which the present invention belongs from the following description. There will be.

The manufacturing method of the multi-walled carbon nanotube conductive dispersion using the milling process according to the present invention invented to achieve the above object is Iron(III) Nitrate Nonahydrate(Fe(NO₃)₃9H₂O) and Cobalt(II) Nitrate Hexahydrate(Co (NO₃)₂6H₂O) was mixed and stirred, the second solution was dissolved in Ammonium Carbonate ((NH₄)₂CO₃), and the third solution was dissolved in Aluminum Hydroxide (Al(OH)₃). 3, a metal catalyst manufacturing step of mixing the first solution and the second solution to prepare a stirred mixed solution, and filtering and drying the mixed solution to produce a metal catalyst; A synthesis step of synthesizing carbon nanotubes at a temperature of 700 to 750°C by putting the metal catalyst in a CVD synthesizer; A milling step of adding the carbon nanotubes to a milling device, adding an aqueous dispersant, an antifoaming agent, and a solvent, followed by milling to prepare a carbon nanotube solution; And a dispersion step of dispersing a dispersant, a binder, a co-solvent, a wetting agent, and a solvent in the carbon nanotube solution to prepare a conductive dispersion. It is preferably characterized in that it comprises a.

In addition to the above-described features, the first solution contains 25.02 parts by weight of Iron(III) Nitrate Nonahydrate (Fe(NO3)₃9H₂O) and 7.55 parts by weight of Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O) based on 100 parts by weight of the solvent. Dissolves parts by weight, and the second solution dissolves 100 parts by weight of Ammonium Carbonate ((NH₄)₂CO₃) based on 100 parts by weight of the solvent, and the third solution is Aluminum Hydroxide (Al(OH)₃) based on 100 parts by weight of the solvent. It is also preferable to further include a feature of dissolving 50 parts by weight.

Meanwhile, in the manufacturing method of the multi-walled carbon nanotube conductive dispersion liquid using the milling process according to the present invention, the metal catalyst manufacturing step includes Iron(III) Nitrate Nonahydrate (Fe(NO3)₃9H₂O), Cobalt(II). A metal catalyst precursor solution in which nitrate hexahydrate (Co(NO₃)₂6H₂O) and aluminum nitrate nonahydrate (Al(NO₃)₃ are dissolved in a solvent is mixed with air to prepare a two-fluid, and then the two-fluid is injected into the reactor and sprayed. It is also possible to be characterized by drying.

In this case, the mass ratio of Iron(III) Nitrate Nonahydrate (Fe(NO₃)₃9H₂O), Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O) and Aluminum nitrate nonahydrate (Al(NO₃)₃) in the metal catalyst precursor solution is 1000: 250: 1200 is included, the temperature of the reaction furnace is 800 ℃, it is preferably characterized in that the pressure of the air flow is 3.5kgf.

The method for preparing a conductive dispersion of multi-walled carbon nanotubes using the milling process according to the present invention is to synthesize the multi-walled carbon nanotubes using a metal catalyst prepared by the DP method or the SD method, and then mechanically milling for a certain period of time. There is an effect of obtaining a multi-walled carbon nanotube conductive dispersion with improved dispersibility.

In addition, the manufacturing method of the conductive dispersion of multi-walled carbon nanotubes using the mechanical milling conditions according to the present invention increases the bulk density and improves the scattering property by performing the milling process, so that mixing with other materials is easy and the wettability is increased. There is an effect that can prepare a multi-walled carbon nanotube conductive dispersion.

In addition, the method of manufacturing a multi-walled carbon nanotube conductive dispersion using mechanical milling conditions according to the present invention is a multi-walled carbon nanotube material with increased convenience in use because the scattering property is improved and electrical conductivity is increased through a milling process. There is an effect of manufacturing a method for preparing a conductive dispersion of wall carbon nanotubes.

In addition, the method for preparing a multi-walled carbon nanotube conductive dispersion according to the present invention obtains a high synthesis yield because multi-walled carbon nanotube growth nuclei can be formed in front of and behind the metal catalyst due to the use of the metal catalyst prepared by the SD method. There is an effect that can be improved productivity.

1 is a flow chart of a process for preparing a catalyst according to the DP method in a method for preparing a conductive dispersion of multi-walled carbon nanotubes according to the present invention.
2 is a flow chart of a process of preparing a catalyst according to the SD method in the method for preparing a conductive dispersion of multi-walled carbon nanotubes according to the present invention.
3 is a table showing the contents and uses of the raw materials introduced in the milling step of the dispersion prepared in the embodiment of the present invention.
Figure 4 is a photograph of the milling processing equipment used in the manufacturing embodiment of the present invention.
5 is a scanning electron microscope (SEM) photograph of a multi-walled carbon nanotube synthesized through Preparation Example 1 of the present invention.
6 is a scanning electron microscope (SEM) photograph of a multi-walled carbon nanotube synthesized through Preparation Example 2 of the present invention.
7 is a table analyzing the characteristics of a multi-walled carbon nanotube according to Example 1 of the present invention.
8 is a table analyzing the characteristics of a multi-walled carbon nanotube according to Example 2 of the present invention.
9 is a graph of an aggregate diameter of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
10 is a graph of bundle lengths of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
11 is a graph of bundle diameters of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
12 is a graph of bulk density of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
13 is a graph of paste viscosity of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
14 is a 1 pass surface resistance graph of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.
15 is a 2 pass surface resistance graph of multi-walled carbon nanotubes prepared according to Preparation Examples 1 and 2 of the present invention.

Hereinafter, the present invention will be described in detail so that the above-described objects and features become clear, and accordingly, a person of ordinary skill in the technical field to which the present invention pertains will be able to easily implement the technical idea of the present invention. In addition, in describing the present invention, when it is determined that a detailed description of the known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be provided as it is already well known in the technical field among the known technologies related to the present invention. I will omit it.

In addition, the terms used in the present invention have selected general terms that are currently widely used as much as possible, but there are terms arbitrarily selected by the applicant in certain cases, and in this case, the meaning of the terms has been described in detail in the description of the corresponding invention. It should be noted that the present invention should be understood as the meaning of the term, not the name of. The terms used in the description of the embodiments are only used to describe specific embodiments, and are not intended to limit the embodiments. Singular expressions include plural expressions unless the context clearly indicates otherwise.

The embodiments may be changed in various forms and may have various additional embodiments, in which specific embodiments are indicated in the drawings and related detailed descriptions are described. However, this is not intended to limit the embodiments to a specific form, and it should be understood to include all changes, equivalents, or substitutes included in the spirit and scope of the embodiments.

In the description of various embodiments, expressions such as “first,” “second,” “first,” or “second” may modify various elements of the embodiments, but do not limit the corresponding elements. For example, the expressions do not limit the order and/or importance of corresponding elements. The above expressions may be used to distinguish one component from another component.

The method for preparing a conductive dispersion of multi-walled carbon nanotubes using a milling process according to the present invention is to synthesize a multi-walled carbon nanotube (MWCNT) by preparing a metal catalyst, and milling the synthesized multi-walled carbon nanotubes. It is preferable to disperse and prepare a conductive dispersion. In the present invention, as a method of manufacturing a metal catalyst used for synthesis of the multi-walled carbon nanotubes, a method of manufacturing by DP (deposition precipitation) and SD (Spray Drying) The method of manufacturing by the method is presented at the same time, and it is possible to selectively apply one of the two methods.

In the case of using a metal catalyst prepared by the DP method, which is one of the metal catalyst manufacturing methods, it can be effectively applied to mass production of carbon nanotubes because the synthesis yield is remarkably improved when synthesizing carbon nanotubes. The metal catalyst made by the phosphorus SD method has an excellent synthesis yield of carbon nanotubes because the growth nuclei of carbon nanotubes can be formed in front and rear of the metal catalyst. There is an effect that carbon nanotubes can be synthesized. In addition, in the case of manufacturing a dispersion through milling of multi-walled carbon nanotubes, it can be used as various electronic, environment, sensor, energy, and display materials in industrial sites because of the advantages of improving electrical conductivity and dispersibility.

Hereinafter, a method of preparing a conductive dispersion of multi-walled carbon nanotubes according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings. 1 is a flowchart illustrating a process of preparing a multi-walled carbon nanotube and a dispersion after preparing a metal catalyst by the DP method in the process of preparing a multi-walled carbon nanotube conductive dispersion according to the present invention. As shown in FIG. 1, in the method of manufacturing a multi-walled carbon nanotube conductive dispersion using a milling process according to the present invention, it is preferable to first perform the metal catalyst manufacturing steps (s110 to s160) by the DP method.

Therefore, first of all, it is necessary to perform the process of making the first solution (step s110) by putting Iron(III) Nitrate Nonahydrate (Fe(NO₃)₃9H₂O) and Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O) in a solvent. desirable. Here, the solvent used to make the first solution is DI water, but with respect to 100 parts by weight of the DI water, 25.02 parts by weight of the Iron(III) Nitrate Nonahydrate and 7.55 parts by weight of Cobalt(II) Nitrate Hexahydrate are put in order and magnetic stirrer It is preferable to dissolve for 20 minutes by using to dissolve until a complete aqueous solution is obtained.

After that, it is preferable to perform a process (step s120) of making a second solution in which Ammonium Carbonate ((NH₄)₂CO₃) is dissolved in a solvent. Here, the solvent used to make the second solution is also preferably DI water, and 100 parts by weight of the Ammonium Carbonate is added to 100 parts by weight of the DI water and dissolved using a bath sonic for about 2 hours, and the solid content is completely It is preferable to dissolve until it dissolves and becomes a complete aqueous solution. After that, it is preferable to perform a process (step s130) of making a third solution in which Aluminum Hydroxide (Al(OH)₃) is dissolved in a solvent. The solvent used to make the third solution is also preferably DI water, and 50 parts by weight of the Aluminum Hydroxide is added to 100 parts by weight of the DI water, and the mixture is stirred with a mechanical stirrer until completely mixed. After the first solution, the second solution, and the third solution are prepared, it is preferable to prepare a mixed solution obtained by mixing the first solution and the second solution in the third solution (step S140). As for the mixed solution, it is preferable to add the first solution and the second solution prepared using a dropping funnel while stirring the third solution with a mechanical stirrer.

Next, it is preferable to undergo a filtration process (step s150) of filtering the mixed solution. In the filtration process, the mixed solution is filtered using a filtering device, and a filter paper is placed on the Buchner Funnel, and the mixed solution is added. It is advisable to filter it in two or three times. After passing through the filtration process (step s150), it is preferable to go through a drying process (step s160). In the drying process (step s160), after dropping the cake filtered on the filter paper and putting it in an oven, it is at a temperature of 150 degrees for 16 hours. It is desirable to dry it longer.

It is preferable to use iron (Fe) and cobalt (Co) as the metal catalyst used in the method for preparing the multi-walled carbon nanotube conductive dispersion liquid using the milling process according to the present invention. Therefore, as described above, the first solution obtained by dissolving Iron(III) Nitrate Nonahydrate, which is a precursor material of iron, and Cobalt(II) Nitrate Hexahydrate, which is a precursor material of cobalt, is prepared and used.

Meanwhile, the first solution prepared by the above method is solidified in the form of metal oxide or metal hydroxide particles when mixed with the second solution in which Ammonium Carbonate, a pH adjusting agent, is dissolved, and when mixed in the third solution in which Aluminum Hydroxide is dissolved. It is adsorbed on the third solution, and may be precipitated in the mixed solution in the form of metal catalyst particles of a mixture of a metal oxide (or metal hydroxide) and the third solution. Therefore, when the first solution and the second solution are added to the third solution, a metal catalyst must be prepared by adjusting a preferable amount, which is an appropriate amount of a pH adjusting agent to form a precipitate of a metal oxide or a metal hydroxide from a transition metal precursor. This is because it is suitable to induce quantitative precipitation of metal components only when is added. Therefore, in the present invention, the component ratio (weight) of each of Iron(III) Nitrate Nonahydrate, Cobalt(II) Nitrate Hexahydrate, Ammonium Carbonate, and Aluminum Hydroxide used to prepare the first solution, the second solution, and the third solution It is preferable to set it as 250.2: 75.5: 2000: 1000.

After performing the metal catalyst manufacturing step (steps s110 to s160), it is preferable to undergo a synthesis step (step s170) of synthesizing carbon nanotubes heated by injecting a mixed gas into the metal catalyst in a CVD synthesis device. . In the synthesis step (step s170), it is preferable to proceed for about 30 minutes at a synthesis temperature of 750°C. In the synthesis step (s170 step), it is preferable to synthesize the multi-walled carbon nanotubes through a chemical vapor deposition method capable of a continuous process.

Then, it is preferable to prepare a carbon nanotube solution by subjecting the synthesized multi-walled carbon nanotubes to a milling process for a certain period of time (s180). To this end, it is preferable to use the prepared multi-walled carbon nanotubes as a raw material and add a water-based dispersant and an antifoaming agent, etc., as shown in Figure 3, as shown in the content and use of the input raw material in the milling process (S1). As described above, it is preferable to perform the milling process while filling the remaining 88.71% with DI water after adding 3.75% of the aqueous dispersant Solspers-46000 and 4.04% of the aqueous antifoaming agent to 3.50% of carbon nanotubes. Figure 4 is a photograph of the milling equipment used in the manufacturing embodiment of the present invention.

After that, it is preferable to make a dispersion by dispersing the carbon nanotube solution (s190). To this end, it is preferable to prepare a conductive dispersion of multi-walled carbon nanotubes by adding a dispersant, a binder, a co-solvent, a wetting agent, and water to disperse the carbon nanotubes. As shown in the content and use (S2), for 24.66% of the multi-walled carbon nanotube dispersion, Disponil 32 1.64% as a dispersant, HU-580 6.14% as a binder, IE349 4.09% as a slip agent, and 1-PrOH 1.90% as a co-solvent And 0.23% of NMP and 1.06% of BYK-346 as a wetting agent, and 60.28% of DI water is preferably added to prepare a dispersion, but the types of the added dispersant, binder, slip agent, co-solvent, wetting agent, and solvent are limited. It does not become.

2 is a flowchart illustrating a process of manufacturing a multi-walled carbon nanotube and a dispersion after preparing a metal catalyst by the SD method in the process of preparing a multi-walled carbon nanotube conductive dispersion according to the present invention. Here, as shown in FIG. 2, the metal catalyst manufacturing step (s210 to s230 process) is first performed by the SD method. First, Iron(III) Nitrate Nonahydrate(Fe(NO₃)₃9H₂O), Cobalt(II) Nitrate Hexahydrate It is preferable to perform a process (step s210) of making a metal catalyst precursor solution in which (Co(NO₃)₂6H₂O) and aluminum nitrate nonahydrate (Al(NO₃)₃) are dissolved in a solvent. Here, the solvent used to make the metal catalyst precursor solution is DI water, and the mass of the Iron(III) Nitrate Nonahydrate, Cobalt(II) Nitrate Hexahydrate and Al(NO3)₃) with respect to 10kg (10L) of DI water It is preferable to mix with each of 1000g, 250g, and 1200g, and then stir with a mechanical stirrer until completely mixed (s210 process). Next, it is preferable to simultaneously put the metal catalyst precursor solution into the reaction furnace with air and dry it (s220 to s230 process), and at this time, in order to adjust the size of the metal catalyst to 5 to 8 μm. It is desirable to keep the temperature at 800°C all the time.

Next, it is preferable to undergo a synthesis step (step s240) of synthesizing carbon nanotubes heated by introducing a mixed gas to the metal catalyst in a CVD synthesis apparatus. In the synthesis step (step s240), it is preferable to set the synthesis temperature to 750° C. and proceed for about 30 minutes. In the synthesis step (step s240), it is preferable to synthesize the multi-walled carbon nanotubes through a chemical vapor deposition method capable of a continuous process.

In addition, it is preferable to prepare a carbon nanotube solution by subjecting the synthesized multi-walled carbon nanotubes to a milling process for a certain period of time, similar to the method for preparing a conductive dispersion through the DP method (s250). To this end, it is preferable to use the prepared multi-walled carbon nanotubes as a raw material and add a water-based dispersant and an antifoaming agent, etc., as shown in Figure 3, as shown in the content and use of the input raw material in the milling process (S1). As described above, it is preferable to perform the milling process while filling the remaining 88.71% with DI water after adding 3.75% of the aqueous dispersant Solspers-46000 and 4.04% of the aqueous antifoaming agent to 3.50% of carbon nanotubes.

It is preferable to disperse the milled carbon nanotube solution to make a dispersion (s260). The milling treatment was 3 hours, 6 hours, and 9 hours, and for this purpose, water was added as a dispersant, a binder, a co-solvent, a wetting agent, and a solvent to disperse the multi-walled carbon nanotubes to prepare a conductive dispersion of the multi-walled carbon nanotubes. It is preferable to do, as shown in Fig. 3, as shown in the content and use of the input raw material in the dispersion process (S2), for 24.66% of the multi-walled carbon nanotube dispersion, Disponil 32 1.64% as a dispersant and HU-580 as a binder. It is preferable to prepare a dispersion by adding 6.14%, IE349 4.09% as a slip agent, 1-PrOH 1.90% and NMP 0.23% as a co-solvent, and 1.06% BYK-346 as a wetting agent, and DI water 60.28%.

The reason for preparing a carbon nanotube dispersion by adding a dispersant is that nano-sized carbon nanotubes tend to agglomerate due to the Van der Waals action, so the dispersant penetrates the carbon nanotube bundle and weakens the interaction between the tube and the tube. Since it plays a role in improving the dispersion of carbon nanotubes and controlling the viscosity of the dispersion, the dispersant is preferably a surfactant or an aqueous dispersant that relieves the tension of the interface.

Types of additives that can be further added to the dispersion to increase dispersibility include wetting agents, slip agents, antifoaming agents, and binders, and wetting agents are surfactants that reduce the surface energy that solid substances are likely to get wet with water. As an additive to make the film or sheet slip well, it provides the necessary lubrication action to reduce the coefficient of friction, and the antifoaming agent is another surface-active material that has stronger adsorption properties than the surfactant, and the binder (binder) increases elasticity and adhesiveness. It is a substance added to increase The additive added for the purpose of enhancing the dispersibility of the dispersion prepared by the present invention can be any solution having the same effect in addition to the above-described specific solution. Thus, the added dispersant, binder, slip agent, and antifoam agent according to the present invention can be used. , The wetting agent and the solvent are not specified as the above-described substances.

Hereinafter, the present invention will be described in more detail through Examples, Experimental Examples, and Manufacturing Examples. It should be understood that the embodiments and the like described below are illustratively shown to aid understanding of the present invention, and the present invention may be variously modified and implemented differently from the exemplary embodiment described herein. As described above, it is obvious to those of ordinary skill in the art that various changes and modifications can be made within the scope of the present invention and the scope of the technical idea, and it is natural that such modifications and modifications fall within the appended claims.

[Example 1] Synthesis of multi-walled carbon nanotubes with metal catalyst prepared by DP method

A metal catalyst was prepared using the DP method. Among the raw materials, Iron(Ⅲ) Nitrate Nonahydrate (hereinafter referred to as FeN) is a Daejeongsa product, and the manufacturer of Cobalt(II) Nitrate Hexahydrate (hereinafter referred to as CoN) is JUNSEI, and the manufacturer of Ammonium Carbonate (hereinafter referred to as NH₄) is Samjeon, Aluminum Hydroxide (hereinafter, Al OH)₃) was manufactured by KC.

(1) 250.2 g of FeN and 75.5 g of CoN were sequentially added to 1 L of DI water and stirred for 20 minutes using a magnetic stirrer to make a complete aqueous solution to prepare a first solution. At this time, the impeller's rotational speed was set to 350.

(2) 2 kg of Ammonium Carbonate (hereinafter referred to as NH₄) was added to 2L of DI water and dissolved to prepare a second solution, which was made into a complete aqueous solution using bath Sonic for 2 hours.

(3) After adding 2L of DI water to a large-capacity beaker, 1kg of Al(OH)₃ was added to mix, and a third solution was prepared by stirring for 5 minutes using a mechanical stirrer. At this time, the impeller's rotational speed was set to 850.

(4) While stirring the third solution with a mechanical stirrer, the first solution and the second solution were dropped for 20 minutes using a dropping funnel to prepare a mixed solution.

(5) The thus prepared mixed solution was filtered using a vacuum filtering device. Two filter papers were placed on 2 sets of Buchner Funnel, and the process was repeated by dividing the solution by half.

(6) The cake filtered on the silver foil was dropped, and the temperature was set to 150°C in a box-type oven and dried for 16 hours to obtain a metal catalyst.

(7) The metal catalyst was put in a CVD synthesis apparatus and synthesized at 750° C. for 30 minutes to obtain a multi-walled carbon nanotube.

[Example 2] Synthesis of multi-walled carbon nanotubes with a metal catalyst prepared by the SD method

Multi-walled carbon nanotubes were synthesized using the SD method. Among the raw materials, Iron(III) Nitrate Nonahydrate (hereinafter referred to as FeN), which is a product of Daejeongsa, and the manufacturer of Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O or less CoN) is the product of Daejeongsa such as JUNSEI and Aluminum nitrate nonahydrate Was used.

(1) 1,000 g of FeN, 250 g of CoN and 1200 g of AIN were added to 10 L of DI water, stirred for 30 minutes using a mechanical stirrer, and dissolved to prepare a metal catalyst precursor solution. It was confirmed that the solution was completely in an aqueous solution state, and if the solid content was not completely dissolved, the above dissolution operation was repeated until completely dissolved.

(2) A metal catalyst was obtained by mixing the metal catalyst precursor solution and air using a two-fluid nozzle, spraying it into a reaction furnace, and drying it, and the temperature of the reaction furnace was 800°C. In order to keep the temperature in the reaction furnace uniform, the temperature was measured at three locations above and below, and the temperature of 800°C was continuously maintained. In order to keep the size of the sprayed metal catalyst constant at 5-8 μm, the pressure of the air-fluid nozzle was 3.5 kgf and sprayed.

(3) The metal catalyst was put in a CVD synthesis apparatus and synthesized at 750° C. for 30 minutes to obtain a multi-walled carbon nanotube.

[Manufacturing Example 1] Preparation of dispersion from multi-walled carbon nanotubes prepared according to Example 1

A conductive dispersion of multi-walled carbon nanotubes was prepared using the multi-walled carbon nanotubes prepared in Example 1 as a raw material.

(1) To 3.50% of the multi-walled carbon nanotubes, 3.75% of Solspers-46000 as an aqueous dispersant and 4.04% of Dynol 604 as an aqueous antifoam were added, and the remaining 88.71% was mixed with DI water.

(2) The mixed solution was divided into 3 parts, placed in a milling machine, and milled to make a carbon nanotube solution. The milling time for each was changed to 3 hours, 6 hours and 9 hours.

(3) A dispersant, a binder, a co-solvent, a wetting agent, and water were added to each of the three milled carbon nanotube solutions, and then dispersed to prepare three conductive dispersions. At this time, the blending ratio is 1.64% of Disponil 32 as a dispersant, 6.14% of HU-580 as a binder, 4.09% of IE349 as a slip agent, 1.90% of 1-PrOH, 0.23% of NMP, as a wetting agent with respect to 24.66% of the carbon nanotube solution. 1.06% of BYK-346 was added and 60.28% of DI water was added.

[Manufacturing Example 2] Preparation of dispersion from multi-walled carbon nanotubes prepared according to Example 2

With respect to the multi-walled carbon nanotubes prepared in Example 2, in the same manner as in Preparation Example 1, three types of conductive dispersions were each prepared through a milling process.

Various experiments were conducted on each of the prepared multi-walled carbon nanotube dispersions, and the optimal milling process time was found by grasping the degree and shape of dispersion according to the milling time in the milling process. The differences in shape and properties such as bulk density, aggregate diameter, bundle length and bundle diameter were analyzed for the tube. In addition, SEM photographs were analyzed to determine bulk density, bundle length, bundle diameter, and aggregate diameter, which are external characteristics against the shape of carbon nanotubes. In addition, the sheet resistance was analyzed for the composite sheet obtained after the milled multi-walled carbon nanotubes were mixed with a polymer resin and subjected to an extruder process. In addition, by burning the composite sheet and observing the shape of the carbon nanotubes dispersed inside, the correlation between the dispersibility was identified, and the change of the material according to the milling treatment was investigated. Hereinafter, each experimental example and its results will be described.

[Experimental Example 1] SEM photo observation

SEM photographs were analyzed to determine bulk density, bundle length, bundle diameter, and aggregate diameter, which are the external characteristics of the shape of carbon nanotubes. FIG. 5 is a photograph of synthesizing multi-walled carbon nanotubes with a metal catalyst prepared by the DP method, and FIG. 6 is a photograph of synthesizing multi-walled carbon nanotubes with a metal catalyst prepared by the SD method. For each of the multi-walled carbon nanotubes before milling and the multi-walled carbon nanotubes after milling for 3 hours, 6 hours and 9 hours, the aggregate diameter, bundle length, and bundle diameter were determined by SEM images of 100 and 1000 times. This is the picture I observed.

When looking at the observed shape of the multi-walled carbon nanotubes, an image of the bundles being rounded after the milling process is shown.This is because the aggregates and bundles are crushed by physical force during the milling process, resulting in shortening of the multi-walled carbon nanotubes. In addition, it was determined that the multi-walled carbon nanotubes pulverized during the drying process were re-aggregated.

[Experimental Example 2] Bulk density measurement

Bulk density is one of the most important properties of multi-walled carbon nanotubes, and an appropriate level of bulk density is required for applications of multi-walled carbon nanotubes. Therefore, to measure the bulk density, the weight of the multi-walled carbon nanotube was measured using a measuring cylinder, and after tapping was performed 100 times, the bulk density was measured by checking the scale by checking the capacity.

7 shows the bulk density measurement results and error ranges before and after milling for the multi-walled carbon nanotubes made by applying the DP method according to Preparation Example 1, and FIG. 8 shows the SD method according to Preparation Example 2. Bulk density measurement results before and after milling for multi-walled carbon nanotubes made by applying are shown along with the error range. And Figure 12 is a graph comparing the bulk density of the multi-walled carbon nanotubes prepared according to Preparation Example 1 and the multi-walled carbon nanotubes prepared according to Preparation Example 2. As shown in FIGS. 7, 8, and 12, it was confirmed that the bulk density increased as the milling treatment time increased.

[Experimental Example 3] Measurement of aggregate diameter, bundle diameter and bundle length

Using a SEM (Scanning Electron Microscope), the appearance of the multi-walled carbon nanotube before milling and the milling process were divided into 3 hours, 6 hours and 9 hours, and then 100, 1000 times images were taken. And the SEM image was analyzed to measure the aggregate diameter, bundle length, and bundle diameter. 7 shows the measurement results and error ranges before and after milling for the multi-walled carbon nanotubes made by applying the DP method according to Manufacturing Example 1, and FIG. 8 shows the SD method according to Manufacturing Example 2 The measurement results before and after milling for the multi-walled carbon nanotubes made are shown along with the error range.

As shown in Figure 7, the aggregate diameter of the multi-walled carbon nanotubes in Preparation Example 1 decreased from about 32.2 μm to 23.3 μm from before milling to 6 hours after milling, and after 9 hours of milling, the aggregate diameter was again 26.1. It can be seen that it rises to μm. Bundle length was 45.1μm, 55.5μm, 33.7μm, and 44.2μm, respectively, from before milling treatment to 45.1μm, 55.5μm, 33.7μm, and 44.2μm. Could. In the case of the bundle diameter, it was confirmed that it was 6.2 μm, 5.1 μm, 3.5 μm, and 4.8 μm, respectively, depending on the milling treatment time from before the milling treatment, which decreased up to 6 hours after the milling treatment, and then increased again after the 9 hours milling treatment.

And, as shown in FIG. 8, the aggregate diameter of the multi-walled carbon nanotubes in Preparation Example 2 was reduced from 48.0 μm before milling to 40.4 μm and 36.3 μm at 3 hours and 6 hours of milling treatment, respectively, and 36.6 at 9 hours of milling treatment. There was little change compared to 6 hours in μm. The bundle length decreased from 79.2 μm before milling to 35.8 μm and 27.3 μm at 3 hours and 6 hours after milling treatment, respectively, and after 9 hours of milling treatment, the bundle length showed a tendency to increase again to 30.4 μm. And the bundle diameter decreased from 8.8μm before milling to 1.6μm and 1.1μm after 3 hours and 6 hours of milling treatment, respectively, and 1.2μm after 9 hours of milling treatment, showing no significant change compared to 6 hours. .

Looking at the measurement results, the aggregate diameters of the multi-walled carbon nanotubes obtained through the 6-hour milling process among the multi-walled carbon nanotubes obtained in Preparation Example 1 and Preparation Example 2 were 23.3 μm and 36.3 μm, respectively, and the bundle diameter was The bundle lengths of 3.5 μm and 1.1 μm were 33.7 μm and 27.3 μm, and the characteristics of the multi-walled carbon nanotube were found to be the best. In addition, through this external analysis, the external factors that influence the variance were analyzed, and it was found that the characteristics of the appearance were correlated with the van der Waals force. That is, it was shown that the multi-walled carbon nanotubes synthesized through Preparation Examples 1 and 2 were physically pulverized through milling treatment and then agglomerated upon drying was weakened, which was weakly formed by the van der Waals force. Be judged to be. Therefore, when the multi-walled carbon nanotubes were milled, it was judged that the cohesive strength was lower and the dispersing power was higher than before the milling treatment.

[Experimental Example 4] Viscosity Characteristics

The viscosity characteristics were measured using a Brookfield cone/paste viscometer, and the multi-walled carbon nanotubes were compared before and after milling, and measured using a paste prepared with a content of 3.7%.

The viscosity characteristic measurement results are also shown in Figs. 7 and 8. As shown in Fig. 7, looking at the viscosity characteristics of the multi-walled carbon nanotubes in Preparation Example 1, the multi-walled carbon nanotubes were 7,656 cP after 3 hours of milling treatment. It exhibited a higher viscosity value than 7,084cP before the furnace milling treatment. It was determined that as the milling treatment was performed, the bundle length of the multi-walled carbon nanotubes was shortened and the specific surface area increased. As a result, the viscosity increased because more solvent was required for the increased specific surface area. However, after 6 hours of milling treatment, the viscosity rapidly decreased to 3,559 cP, and after 9 hours of milling treatment, it was confirmed that the viscosity slightly increased to 4,520 cP. This rapid decrease in viscosity after 6 hours of milling treatment is that after 3 hours of milling treatment, the length of the multi-walled carbon nanotubes is further shortened by the physical force and dispersed to form a uniform distribution and thus the viscosity is lowered. As a result, it was judged that lowering the viscosity would lead to an increase in wettability.

And looking at the viscosity characteristics of the multi-walled carbon nanotubes in Preparation Example 2, as shown in FIG. 8, from 12,250 cP before the milling treatment to 13,512 cP at the time of 3 hours of milling treatment, and 5,640 cP after 6 hours of milling treatment. Fell sharply. And after 9 hours of milling process, it showed a phenomenon of increasing again to 7,825cP. This phenomenon showed a result similar to the viscosity characteristics of the multi-walled carbon nanotubes prepared in Preparation Example 1. As a result, it was judged that during the milling treatment, the bundle length of the multi-walled carbon nanotubes was shortened due to the physical force, and the specific surface area increased, so that more solvent was required for the increased specific surface area, resulting in an increase in viscosity.

[Experimental Example 5] Sheet resistance characteristics

Polyethylene (PE) of LDPE5321 was added to 2 wt% of each of the multi-walled carbon nanotubes (MWCNT) prepared in Preparation Examples 1 and 2, respectively, in a twin extruder to produce pellets. It was carried out with the equipment of Twin Extruder, and the melting temperature was carried out at 150℃. The feeder and twin extruder's own rpm were set to 5 and 200, respectively, and the sheet resistance was measured by making the MWCNT/PE composite in the form of a sheet in a hot press as a pellet form. In the hot press process, 100g of pellets were weighed, heated at 180°C for about 2 minutes, and cooled for 2 minutes to make a sheet. The sheet made in this way was subjected to a 4-probe sheet resistance measuring device to measure the sheet resistance value at each of the upper, middle, and lower parts of 9 locations to analyze the electrical conductivity. In order to find out the electrical conductivity in the MWCNT/PE composite, extrusion evaluation was performed for 3, 6 and 9 hours before milling and for each milling treatment time, and the extrusion evaluation was divided into 1 pass and 2 pass.

The sheet resistance measurement results are also shown in FIGS. 7 and 8. As shown in FIG. 7, when the extrusion evaluation is performed with the MWCNT/PE composite prepared according to Preparation Example 1, in the case of 1 pass, at 4.33 Ω/m 2 before milling. After 3 hours of milling treatment, it gradually decreased to 3.62Ω/㎡, and after 6 hours of milling treatment, it gradually decreased to 3.08Ω/㎡, and after 9 hours of milling treatment, it increased to 3.48Ω/㎡ again. However, in the case of 2pass, it was found that the change in sheet resistance of 1pass was less than the change in sheet resistance of 1pass, from 2.84Ω/㎡ before milling to 2.96Ω/㎡ after 3 hours milling treatment and 2.55Ω/㎡ after 6 hours milling treatment. The change in the sheet resistance characteristics according to the milling time was determined because the length of the material was shortened through physical pulverization of the MWCNT through the milling treatment and existed at an appropriate level to form a network in the composite. Therefore, if a multi-walled carbon nanotube dispersion is prepared after 6 hours of milling, a dispersion having excellent dispersing power can be prepared because the sheet resistance is small.

As shown in Fig. 8, when extrusion evaluation is performed using multi-walled carbon nanotubes before and after milling according to Preparation Example 2, in the case of extrusion evaluation 1 pass, 6.13 Ω in a 3 hour milling process than 4.81 Ω/㎡ before milling. It was shown that the sheet resistance value increased to /㎡. However, after 6 hours of milling process, the result value decreased to 4.11 Ω/㎡, and after 9 hours of milling treatment, it was found that it increased to 5.49 Ω/㎡ again. Extrusion evaluation 2pass shows similar results to 1pass. After milling for 3 hours at 2.65Ω/㎡ before milling, the sheet resistance value of 3.29Ω/㎡ increases, but when milling for 6 hours, it is 2.37Ω/㎡ before milling. It was confirmed that the foam resistance value of the MWCNT/PE composite was lowered. However, after 9 hours of milling treatment, the sheet resistance value again increased to 2.87Ω/㎡. Through the extrusion evaluation, the sheet resistance value of the MWCNT/PE composite was best observed in the 6-hour process after the milling process, and it was confirmed that the 6-hour milling process was the most appropriate process condition.

9 to 15 are shown in graphs by comparing each characteristic by milling the multi-walled carbon nanotubes manufactured by the DP method and the SD method. The analyzed items are factors affecting dispersion, etc.FIG. 9 is an aggregate diameter, FIG. 10 is a bundle length, FIG. 11 is a bundle diameter, FIG. 12 is a bulk density, FIG. 13 is a viscosity, and FIG. 14 is an extrusion evaluation 1pass, and FIG. 15 is For the extrusion evaluation (2pass), the properties of the multi-walled carbon nanotubes were compared.

In FIG. 9, the aggregate diameter was compared and shown according to the type of multi-walled carbon nanotubes. As shown in FIG. 9, although there is a difference in the size of the aggregate diameter, it can be seen that the characteristics of the two materials show similar trends. In Fig. 10, the bulk density increases and decreases as the milling processing time increases, and in Figs. 11 and 12, both the bundle length and the bundle diameter show the shortest length when the milling processing time is a 6-hour process. It shows an increase or decrease again after 9 hours. In the case of the viscosity characteristics of FIG. 13, it was confirmed that the viscosity of the two materials increased during the 3 hour process after the milling treatment, and the viscosity decreased during the 6 hours and 9 hours process treatment. In addition, the extrusion evaluation results shown in FIGS. 14 and 15 show that the composite of the multi-walled carbon nanotubes, which was milled for 6 hours, has the lowest sheet resistance when compared for each material of the multi-walled carbon nanotubes and for 1 pass and 2 passes, respectively. It shows excellent results.

Based on the results of the experiment, as the external characteristics of the multi-walled carbon nanotubes, it was found that as the aggregate diameter, bundle diameter, and bundle length decrease, the dispersibility increases in polymer composites and pastes that require application of the material. With the increase of, the scattering property of the multi-walled carbon nanotubes also increased, resulting in improved inconvenience in use. If the multi-walled carbon nanotubes are milled for 6 hours, dispersibility and wettability are higher than that of the material before the milling treatment, and the convenience of use is much better.Therefore, a multi-walled carbon nanotube conductive dispersion solution with these advantages can be prepared. will be.

Although the present invention has been described with various examples described above, the present invention is not necessarily limited to these examples, and various modifications may be made without departing from the spirit of the present invention. Therefore, the examples disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these examples. The scope of protection of the present invention should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (5)

delete delete Iron(III) Nitrate Nonahydrate(Fe(NO₃)₃9H₂O) and Cobalt(II) Nitrate Hexahydrate(Co(NO₃)₂6H₂O) were mixed and stirred, the first solution, Ammonium Carbonate ((NH₄)₂CO₃) dissolved in the second solution, and After each preparing a third solution in which Aluminum Hydroxide (Al(OH)₃) is dissolved, the first solution and the second solution are mixed with the third solution to make a stirred mixed solution, and the mixed solution is filtered and A metal catalyst manufacturing step of drying to form a metal catalyst;
A synthesis step of synthesizing carbon nanotubes at a temperature of 700 to 750°C by putting the metal catalyst in a CVD synthesizer;
A milling step of putting the carbon nanotubes in a milling device, adding an aqueous dispersant, an antifoaming agent, and a solvent, followed by milling to prepare a carbon nanotube solution; And
A dispersing step of dispersing a dispersant, a binder, a co-solvent, a wetting agent, and a solvent in the carbon nanotube solution to prepare a conductive dispersion; Including,
The metal catalyst manufacturing step is a metal catalyst obtained by dissolving Iron(III) Nitrate Nonahydrate (Fe(NO₃)₃9H₂O), Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O) and aluminum nitrate nonahydrate (Al(NO₃)₃) in a solvent. A method for producing a conductive dispersion of multi-walled carbon nanotubes, characterized in that a precursor solution is mixed with air to prepare a two-fluid, and then the air-fluid is sprayed and dried in a reaction furnace to form a metal catalyst. The method of claim 3,
The metal catalyst precursor solution has a mass ratio of each of the solvent, Iron(III) Nitrate Nonahydrate(Fe(NO3)₃9H₂O), Cobalt(II) Nitrate Hexahydrate (Co(NO₃)₂6H₂O) and Aluminum nitrate nonahydrate (Al(NO₃)₃). : 1000: 250: 1200, characterized in that the method for producing a multi-walled carbon nanotube conductive dispersion The method of claim 3,
The temperature of the reaction furnace is 800°C and the injection pressure of the airflow body is 3.5kgf.

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