KR20060081474A - Method for manufacturing of porous carbon material - Google Patents

Abstract

The present invention relates to a method for producing a carbonaceous material comprising the step of heat treating and stirring the pitch in two stages to prepare a carbonaceous raw material, and molding and heating and pressurizing the prepared carbonaceous material in a predetermined form. In the present invention, the heat treatment step of the pitch was improved, and the uniformity of the finished carbonaceous pores was improved by molding and heat-pressing the heat treated pitch, and shortening the production time once. Therefore, the carbon material produced by the method of the present invention has a low production cost, there is an economic advantage. Such carbon materials can be economically used as materials for heat dissipation efficiency of computers, electronic products, mobile communication, heat exchangers, radiators and the like. In addition, the present invention can be used for automobile exhaust gas reducing devices, air and water purification filters, and the like.

Carbon material, carbon material raw material, pitch, pore

Description

Manufacturing method of porous carbon material {METHOD FOR MANUFACTURING OF POROUS CARBON MATERIAL}             

1 is a schematic diagram of an apparatus for producing a carbon material according to the present invention.

Figure 2 is a graph showing the degree of polycondensation of the pitch according to the temperature during the first heat treatment of the pitch according to the invention as the content of QI (Quinoline Insoluble).

Figure 3 is a graph showing the measured value of the pitch viscosity with temperature during the second heat treatment of the pitch according to the present invention.

4 is a graph showing a thermogravimetric analysis curve according to the rotational speed of the stirrer after the first and second heat treatment of the pitch according to the present invention.

5 is a graph showing the change of the functional groups according to the rotational speed of the stirrer after the first and second heat treatment of the pitch according to the present invention measured by FT-IR.

Figure 6 is a photograph observing the pore structure of the carbon material (A) prepared according to the method of the present invention and the carbon material (B) prepared by the conventional method with an electron microscope.

Figure 7 is a photograph of the pore wall surface of the carbon material (A) prepared according to the method of the present invention and the carbon material (B) prepared by the conventional method with an electron microscope.

* Explanation of symbols for the main parts of the drawings *

1: Furnace 2: SUS beaker

3: agitator 4: nitrogen gas injection site

5: outgassing area 6: thermocouple

7: PID controller

The present invention relates to a method for producing a porous carbon material, and more specifically, to heat treatment and stirring the pitch in two stages to prepare a carbon material raw material and the step of forming the molded carbon material raw material in a constant form and heat pressurized It relates to a method for producing a carbon material comprising a.

Carbon material is composed of non-graphite carbon and has hexagonal crystal structure, van der Waals bond in the c-axis direction, and covalent bond on the plane perpendicular to it. It has the property of showing anisotropy. The carbon material exhibits a thermal conductivity of 1200 W / mK at 700 ° C., which is a high value corresponding to 5 times and 4 times the thermal conductivity of copper or aluminum, which is mainly used in a thermal converter. In addition, since it has a large specific surface area and low density, it is known as an ideal material satisfying the requirements of a heat exchanger. Therefore, it can be used as a material for improving heat dissipation efficiency in the manufacture of notebook computers, portable personal terminals, heat exchangers of boilers, heat exchangers of air conditioners, heat sinks of electronic products, CPU coolers, radiators, PDP heat sinks and the like.

Thus, the carbon material exhibits high heat dissipation efficiency because not only the carbon itself has high thermal conductivity, but also the specific surface area is increased due to the pore structure generated during the manufacture of the carbon material, thereby increasing the heat dissipation area. It is known that the smaller and uniform, and the better the arrangement of the pore walls, the higher the heat dissipation efficiency.

In general, the carbon material is manufactured by heat-treating coal or petroleum pitch and heat-pressurized under high pressure conditions. The uniformity of the pore structure and the orientation of the pore walls are determined by the heat treatment conditions of the pitch, which is the starting material of the carbon material. This determines the heat release efficiency of the finished carbon material.

The first purpose of heat treatment of the pitch is to improve the arrangement of crystals in the pore wall during pore formation by breaking complex steric aromatic compounds in the pitch into linear aromatic compounds. The crystal array of the pore wall is generated when the external pressure applied and the pressure caused by the internal volatile generation are in contact with each other. In this case, the complex crystal structure of the pore wall is effectively formed by separating the complex three-dimensional aromatic compounds of the pitch linearly. In order to linearly separate a complex steric aromatic compound, heat is applied to break functional groups such as methylene (-CH ₂ ) and methyl (-CH ₃ ) groups of the aromatic compound. In general, however, when heat is applied to the pitch, these functional groups are broken and a polycondensation reaction occurs to polymerize. In other words, the molecular weight is increased to remain a complex three-dimensional aromatic compound rather than broken into a linear aromatic compound, thereby increasing the viscosity and adversely affect the pore formation. Therefore, it is important to perform heat treatment while controlling the temperature so that polycondensation does not occur.

The second purpose of heat treating the pitch is to adjust the viscosity of the pitch. Viscosity control by heat of pitch affects pore growth and coalescence during pore formation, affecting pore size and uniformity. Usually, if the viscosity is too low, the pores grow freely and coalesce, and the pore size becomes uneven. On the other hand, if the viscosity is too high, the amount of volatile contained in the pitch is small, so that pore generation is not fundamental. Therefore, it is important to have a viscosity of 500-2000 Pa.secs suitable for forming carbon foam when heat-treating the pitch.

In the prior art (Patent Nos. 2001-0023530, Published Patents 2003-0009378, Published Patents 2002-0063859), the heat treatment of the pitch is performed in one step at a low temperature of about 300 ° C, and such conditions are three-dimensional aromatics. It was possible to break the compound into a linear aromatic compound, but since the temperature was too low for effective viscosity control, there was a need to control the pore size and uniformity by raising the pressure to 1000 psi in the subsequent heat pressurization process.

  On the other hand, in the heat pressurization process for manufacturing a conventional carbon material, the pitch was charged to the heat pressurizer in the form of powder, which causes the air present between the powder particles to work together in the growth and coalescence of the pores when the pores are formed, causing unevenness of the pores. It was. Therefore, the prior art had to maintain a long vacuum in order to remove the air present in the pitch powder during the heating and pressing process, which leads to a problem that the overall process time is extended, resulting in a higher production cost of the finished carbon material. .

In order to overcome the above-mentioned problems, the present inventors have been continuously researching to simplify the process of manufacturing a carbon material and to obtain process conditions for producing excellent carbon materials. After that, the carbon material was formed under a certain pressure, and then a carbon material manufacturing method was developed. The entire process was simplified by this method, thereby reducing the time, and the finished carbon material had uniform pore size and orientation. The present invention has been completed by confirming that it has a well pore wall surface and excellent physical properties.

The technical problem to be achieved by the present invention is to provide a method for producing a carbon material that can improve the uniformity of the pores and to produce a carbon material excellent in physical properties more easily and economically.

The present invention to achieve the above technical problem,

After the first heat treatment of the pitch for 30 minutes to 10 hours at 200 ~ 300 ℃, and the carbon material raw material manufacturing step of secondary heat treatment for the first heat treatment pitch for 30 minutes to 5 hours at 450 ~ 460 ℃ It provides a method for producing a carbon material characterized by.

As used herein, the term 'carbonaceous material' refers to a material whose viscosity is controlled by heat treating coal or petroleum pitch used to produce carbonaceous material.

Hereinafter, the present invention will be described in detail.

In the carbon material manufacturing method of the present invention, after the first heat treatment of the pitch for 30 minutes to 10 hours at 200 ~ 300 ℃, the second heat treatment of the first heat treatment pitch for 30 minutes to 5 hours at 450 ~ 460 ℃ Characterized in that it comprises a raw material manufacturing step.

In the above-mentioned pitch (pitch) is a residue from the pyrolysis of organic matter or distillation of tar, in the present invention, coal or petroleum pitch is used, and specifically, coal pitch is preferably used.

In order to produce an excellent carbon material, heat treatment conditions (heat treatment temperature and time) of pitch for producing a carbon material raw material are important. In other words, in the temperature range where polycondensation does not occur in the production of carbonaceous raw materials, the chain of complex three-dimensional aromatic compounds should be broken into linear aromatic compounds to improve the crystal arrangement of the pore walls during pore formation. In addition, the carbon material raw material should have an appropriate viscosity to improve the size and uniformity of the pores of the carbon material, in the present invention, after the first heat treatment at a temperature where polycondensation does not occur, after breaking the chain of the three-dimensional aromatic compound, viscosity control These problems were solved by performing a second heat treatment at a temperature for.

In the carbon material manufacturing method of the present invention, the temperature during the first heat treatment is preferably 200 ~ 300 ℃, if the temperature is less than 200 ℃ in the above complex three-dimensional aromatic compound in the pitch hard to break the linear aromatic compound, the temperature is 300 ℃ If it exceeds, there is a problem that the polymerization by polycondensation occurs. Therefore, in order to break | disconnect with a linear aromatic compound without polycondensation occurring, it is preferable to heat-process primarily in the said temperature range. In addition, it is preferable that the first heat treatment is performed for 30 minutes to 10 hours. If the heat treatment time is less than 30 minutes, the proper decomposition degree of the steric aromatic compound is not achieved, so that the pores of the final porous carbon material are unevenly formed. This is because when the excessive time exceeds 10 hours, decomposition of the aromatic compound proceeds excessively, but excessive oxygen is introduced into the linear aromatic compound branch, resulting in a weakening of the structure of the final porous carbon material, thereby deteriorating mechanical and thermal properties.

In the carbon material manufacturing method of the present invention, the temperature during the second heat treatment is preferably 450 ~ 460 ℃, if the temperature is less than 450 ℃ in the viscosity of the pitch is too low, the size of the pores of the finished carbon material is uneven, If the temperature exceeds 460 ℃ there is a problem that the formation of pores is not fundamentally high due to the high viscosity of the pitch. Therefore, in order to maintain a suitable viscosity, the carbonaceous material is preferably heat-treated secondly in the above temperature range. In addition, the secondary heat treatment is preferably made for 30 minutes to 5 hours, but if the heat treatment time is less than 30 minutes, the viscosity is very low, there is a problem that the shape of the pores growth and coalescence is very uneven, very uneven, 5 hours This is because when the viscosity is very high and the amount of volatile is small, the generation of pores is fundamentally impossible.

In general, the heat treatment temperature of the pitch also affects the properties of the desired final porous carbon material. The porous carbon material made of a low heat treatment carbonaceous raw material has a high mechanical strength due to its dense structure, but has an amorphous thermal conductivity. On the other hand, the porous carbon material prepared from the carbon material of high heat treatment temperature has a high thermal conductivity, but the structure is not dense due to the development of crystallinity, the mechanical strength is lowered, as in the present invention after the first heat treatment at 200 ~ 300 ℃ By preparing a carbonaceous raw material by secondary heat treatment at 450 to 460 ° C, there is an advantage that the mechanical strength and thermal conductivity of the final porous carbonaceous material can be increased.

On the other hand, the aromatic compounds linearly broken in the first heat treatment step for producing a carbonaceous material may be converted back to a three-dimensional aromatic compound by the polycondensation reaction. The present invention is characterized in that the pitch is stirred at a rotational speed of 250 to 500 rpm during the heat treatment of the pitch in order to prevent such a conversion phenomenon and remain as a linear aromatic compound even after the secondary heat treatment. If the rotational speed is less than 250rpm in the stirring process, the pitch broken by the linear aromatic compound is easily converted to the three-dimensional aromatic compound, the decomposition may not be effective to the linear aromatic compound may occur, if the linear aromatic compound exceeds 500rpm It is preferable to stir at a rotational speed in the above range because oxygen molecules may be excessively introduced to cause a problem in that the final porous carbon material is not dense.

As described above, the viscosity of the carbonaceous material prepared after the second heat treatment is 500 to 2000 Pa.secs.

On the other hand, in the carbon material manufacturing method of the present invention after the heat treatment as described above, the carbonaceous material is molded into a certain shape, preferably blocks under a pressure of 0.1 ~ 0.5kgf / cm ² , and then charged in a pressure vessel, 50 Pressure of ˜150 psi, specifically 100 psi and 400 ~ 550 ℃ temperature, specifically characterized in that it further comprises the step of heat pressurized at a temperature of 500 ℃.

As described above, by forming the carbonaceous raw material under a pressure of 0.1 ~ 0.5kgf / cm ² can be removed inside the pores, therefore, in the heating and pressing process without raising the pressure to a high pressure of 1000psi without burning for a long time The uniformity of the material pores can be improved. If the pressure of the carbon material is less than 0.1kgf / cm ² when forming the raw material may not be enough to remove the air between the powders may cause a problem that the shape of the pores when forming the pores, if exceeding 0.5kgf / cm ² Since there is a problem in that the stress distribution occurs in the broken block and the internal crack develops during the carbonization process, so that a cracking phenomenon of the final porous carbon material occurs, molding under the pressure in the above range is preferable.

Carbon material manufacturing method of the present invention,

1) a step of preparing a carbonaceous raw material for the first heat treatment of the pitch at 200 to 300 ° C. for 30 minutes to 10 hours, and the second heat treatment of the first heat treated pitch at 450 to 460 ° C. for 30 minutes to 5 hours; And

2) molding the carbonaceous material into a block under a pressure of 0.1 to 0.5 kgf / cm ² , and then charging the container to a pressurized container, and heating and pressing under a pressure of 50 to 150 psi and a temperature of 400 to 550 ° C. It features.

As described above, the carbon material manufactured by heat-treating in two steps and molding into a predetermined shape and then heat-pressing has the advantage that the pore size is small and uniform, and the crystal arrangement of the pore wall is also improved, so that the heat radiation effect is high. In addition, the carbon material produced by the method of the present invention has excellent physical properties of 0.54 g / cm ^{3 in} density and 57.5 W / mK in thermal conductivity.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Example 1

Establish optimal heat treatment conditions for producing good carbon materials

1-1) Establishment of Primary Heat Treatment Condition

After finely pulverizing the coal pitch, 300 g of them were charged into an SUS container, and the quinoline insoluble (QI) content indicating the degree of polycondensation was measured while raising the temperature at a temperature increase rate of 5 ° C./min. 2 is shown. The temperature of the heat treatment apparatus (see FIG. 1) was controlled within a ± 1 ° C. error range using a PID temperature controller. During the heat treatment and cooling, a nitrogen injection tube was installed in a furnace (see FIG. 1) to maintain the inert atmosphere in order to prevent the sample from being changed at high temperature by oxidizing the sample.

As shown in Figure 2, it can be seen that the content of QI sharply increased above 300 ℃. That is, when the heat treatment at a temperature in the range of 200 ~ 300 ℃ it was confirmed that only the decomposition of the three-dimensional aromatic compound in the pitch is not accompanied by polycondensation.

1-2) Establish secondary heat treatment condition

Heat was again applied to the heat treated pitch as in Example 1-1), and the viscosity of the pitch was measured. The results are shown in FIG. 3.

As shown in FIG. 3, the viscosity rapidly increased when the secondary heat treatment temperature was 470 ° C. FIG. In addition, the viscosity was too low when the secondary heat treatment temperature was less than 450 ° C. That is, the viscosity of the carbonaceous raw material heat-treated at a temperature of 450 ~ 460 ℃ was a range of 500 ~ 2000 Pa.sec which is sufficient to have a uniform pore size and well-oriented pore wall structure.

1-3) establishment of rotation speed

The heat treated pitch was stirred while changing the rotation speed using the stirrer as in Example 1-2), and the heat weight of the pitch and the change of the functional groups were measured according to the rotation speed change, and the results are shown in FIGS. 5 is shown.

Thermogravimetry was measured using a TGA / SDTA851 thermal analysis system (Thermal Analysis System, Mettler, Switzerland). The amount of the sample used in the analysis was 7 mg, and the temperature was raised at a rate of 10 ° C./min from 25 ° C. to 1000 ° C. in an air atmosphere and a nitrogen atmosphere.

Functional group changes were measured by obtaining IR spectra using Fourier-transform IR spectroscopy (Midac, M2000).

When the steric aromatic compound in the pitch is decomposed into a linear aromatic compound, the carbonyl group (-CO) increases as the methylene (-CH ₂ ) group and the methyl (-CH ₃ ) group are removed, and the carbonyl group in the pitch When combined to increase the thermogravimetric temperature, if it is above a certain temperature at which oxidation is initiated, it is oxidized to CO ₂ and flies to reduce the thermogravimetric weight.

As shown in Figure 4, when the rotational speed is 250 ~ 500rpm initial heat weight was increased and the weight loss was large at a certain temperature. On the other hand, if there is no rotation speed, the weight decreases constantly, and the weight loss is the smallest near the oxidation start temperature. This is evidence that a significant amount of methylene and methyl groups have not been removed and at the same time the steric aromatics have not been converted to linear aromatics. Therefore, it was confirmed that the rotational speed of the stirrer is suitable for the heat treatment of the pitch is 250 ~ 500rpm.

In addition, as shown in Figure 5, when the rotational speed is 250 ~ 500rpm methylene, methyl group was effectively decomposed, the strength was weakened, it was confirmed that the strength of the carbonyl group is relatively strong.

Example 2

Manufacture of carbon materials

The coal pitch was first heat treated at 200 to 300 ° C. for 30 minutes and second heat treated at 450 to 460 ° C. for 30 minutes to prepare a carbonaceous raw material. At this time, the agitator was stirred at a rotational speed of 500 rpm during the heat treatment. The prepared carbonaceous material was molded into blocks under a pressure of 0.5 kgf / cm ₂ , and then charged into a heating pressurizer, under a pressure of 100 psi, a temperature increase rate of 5 ° C./min, and a temperature of 500 ° C. without applying a vacuum. The carbon material was manufactured by heat-pressing for 30 minutes. Total manufacturing time was 130 minutes.

Comparative Example 1

As in the conventional method, the coal pitch was heat-treated for 1 hour at a temperature range of 430 to 490 ° C., and then cooled and powdered to obtain a carbonaceous raw material. The carbonaceous material raw material in powder state was charged into a heating pressurizer and then heated. After heating at a temperature increase rate of 0.5 ° C./min to the softening point of the carbonaceous material near 200 ° C. to 300 ° C., vacuum was applied for 1 hour to remove air between the powders and to compact. The vacuum was removed and nitrogen or argon gas was injected to apply a pressure of 1000 psi. In this state, the temperature was raised to a temperature of 500 ° C. or higher at a temperature rising rate of 0.2 ° C./min, and then heated and pressurized for 60 minutes to prepare a porous carbon material. The total production time was 2560 minutes, which took 19 times more than the time for producing the carbon material according to the method of the present invention.

[Test Example 1]

Physical property comparison test of carbon material

1-1) Comparison of Pore Uniformity

The pores of the carbon material according to the present invention prepared in Example 2 and the carbon material according to the conventional method prepared in Comparative Example 1 were observed with an electron microscope (SEM, AKASHI, WB-6).

As shown in Figure 6 and 7, the carbon material prepared in the present invention was confirmed that the pore size has a uniform microstructure, both the wall surface of the pores or where the pores are oriented and orientation is well developed I could confirm it. On the other hand, the carbon material produced by the conventional method was confirmed that the pore size is uneven, the orientation of the pore wall surface is also irregular.

That is, it can be confirmed that the heat treatment method and the method of molding and charging the same as in the present invention are effective in forming a uniform pore size and well-oriented pore wall surface.

 1-2) Thermal conductivity and density measurement

Thermal conductivity and density of the carbon material prepared in Example 2 and Comparative Example 1 were measured.

Thermal conductivity was measured according to the KS L 1604 measurement method, the thermal conductivity meter was used Ultra-Rico TC-7000 (Ulava-rico TC-7000). At this time, the test specimen was manufactured in a square having dimensions of 10 mm in width and 2 mm in thickness, respectively.

In the case of density, it was weighed using 4 decimal place chemical balance (AT201, Mettler, Switzerland), and the apparent density was measured by obtaining the volume of the vernier caliper specimen. In addition, density was measured using a gas pycnometer (Gas Pycnometer, Accupyc 1330) and compared with the apparent density.

As a result of the measurement of the density and the thermal conductivity, it was confirmed that the carbon material produced by the method of the present invention had excellent physical properties with a density of 0.54 g / cm ³ and a thermal conductivity of 57.5 W / mK.

As described above, in the present invention, the heat treatment step of the pitch was improved, and the uniformity of the finished carbon material pores was improved by molding and heat-pressing the heat treated pitch, and shortening the production time once. Therefore, the carbon material produced by the method of the present invention has an economical advantage of low production cost. Such carbon materials can be economically used as materials for heat dissipation efficiency of computers, electronic products, mobile communication, heat exchangers, radiators and the like. In addition, the present invention can be used for automobile exhaust gas reducing devices, air and water purification filters, and the like.

Claims (7)

After the first heat treatment of the pitch for 30 minutes to 10 hours at 200 ~ 300 ℃, and the carbon material raw material manufacturing step of secondary heat treatment for the first heat treatment pitch for 30 minutes to 5 hours at 450 ~ 460 ℃ Method for producing a carbon material characterized in that. The method of claim 1, The pitch is characterized in that the stirring at a rotational speed of 250 ~ 500rpm Method of producing carbon material. The method of claim 1, Forming the carbonaceous raw material into a block under a pressure of 0.1 ~ 0.5kgf / cm ² , charged in a pressure vessel, and further comprising the step of heating and pressing under a pressure of 50 ~ 150psi and a temperature of 400 ~ 550 ℃ Method for producing a carbon material characterized in that. The method of claim 1, The viscosity of the carbon material raw material is characterized in that 500 ~ 2000 Pa.sec Method of producing carbon material. 1) a step of preparing a carbonaceous raw material for the first heat treatment of the pitch at 200 to 300 ° C. for 30 minutes to 10 hours, and the second heat treatment of the first heat treated pitch at 450 to 460 ° C. for 30 minutes to 5 hours; And 2) molding the carbonaceous material into a block under a pressure of 0.1 to 0.5 kgf / cm ² , and then charging the container to a pressurized container, and heating and pressing under a pressure of 50 to 150 psi and a temperature of 400 to 550 ° C. Method for producing a carbon material characterized in that. The method of claim 5, The pitch is characterized in that the stirring at a rotational speed of 250 ~ 500rpm Method of producing carbon material. The method of claim 5, The carbon material raw material viscosity is 500 ~ 2000 Pa.secs characterized in that the manufacturing method of the carbon material.

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