Porous carbon-based material

Abstract

To provide a porous carbon-based material with which generation of fine powder can be prevented even when precursor powder having wide particle size distribution is used, and to provide a production method of the porous carbon-based material.SOLUTION: In a porous carbon-based material having secondary particles constituted by carbon-based particles and a carbonaceous binder making the carbon-based particles combine with each other, the secondary particles are not existing independently but combined with each other. A production method of the porous carbon-based material includes: a raw material forming step to obtain raw material powder by kneading the carbon-based particles and pitch with softening point of 70-200°C; a molding step to obtain a molding with a specified shape by putting the raw material powder in a molding tool and heating it to a temperature higher than the softening point; and a sintering step to sinter the molding.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a porous carbon-based material and a method for manufacturing the porous carbon-based material.

Background Art

[0002] Carbon-based materials have corrosion resistance and heat resistance against various chemicals, and thus are widely used in fields such as semiconductor manufacturing equipment, various electrode materials, the metallurgical field, electrodes for electrical discharge machining, and high-temperature furnaces.

[0003] Among such carbon-based materials, dense and high-strength isotropic graphite materials obtained by using fine particle raw materials and isotropically molding them at a high molding pressure are widely used. On the other hand, in fields such as filters and catalyst carriers, porous carbon-based materials are required, and various measures have been taken to reduce the density and increase the strength.

[0004] Patent Document 1 discloses a method for manufacturing a porous carbon molded body for solving the problem that a porous carbon-based material easily generates fine powder due to weak strength and pollutes the environment such as water and air. In this manufacturing method, when manufacturing a porous carbon molded body having a porosity of 20% or more, a ratio of open pore volume to total pore volume of 50% or more, and a flexural strength of 10 kg / cm 2 or more, a carbonaceous powder having a flexural strength of 100 kg / cm 2 or more when the molded body molded at a molding pressure of 1 ton / cm 2 is fired up to 1000 °C is used for molding, firing, or graphitization.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The invention described in Patent Document 1 is an invention that solves the problem of the generation of fine powder by forming, firing, or graphitizing using a carbonaceous powder having certain characteristics to obtain a high-strength carbonaceous carbon formed body. However, originally, for the raw material for manufacturing a porous body, coarse particles and fine particles are widely distributed, and when manufacturing a porous carbon-based material, the fine particles are likely to be released without being incorporated into the material, becoming a source of fine powder.

[0007] In view of the above problems, an object of the present invention is to provide a porous carbon-based material capable of preventing the generation of fine powder and a method for manufacturing the porous carbon-based material even when using raw material powder with a wide particle size distribution.

Means for Solving the Problems

[0008] The porous carbon-based material of the present invention is a porous carbon-based material in which carbon-based particles and a carbonaceous binder that binds the carbon-based particles to each other form secondary particles, and the secondary particles are bonded to each other without being independent.

[0009] In the porous carbon-based material of the present invention, since the secondary particles are bonded to each other without being independent, it is possible to suppress particles that have fallen off from the inside from coming out to the outside of the material.

[0010] Further, the porous carbon-based material of the present invention is preferably in the following aspect.

[0011] The porous carbon-based material has a maximum pore diameter of 50 to 1000 μm.

[0012] When the maximum pore diameter is 50 μm or more, it can be suitably used for various applications as a porous carbon-based material. When the maximum pore diameter is 1000 μm or less, a sufficient specific surface area can be obtained, and the surface inside the pores can be sufficiently utilized.

[0013] The porous carbon-based material has a bulk density of 1.0 to 1.5 g / cm 3 and is.

[0014] If the bulk density is 1.0 g / cm 3 or more, sufficient strength to maintain the shape as a porous material can be obtained. If the bulk density is 1.5 g / cm 3 or less, a sufficient pore volume can be obtained, so that the porous material can exhibit sufficient functions.

[0015] The porous carbon-based material has a flexural strength of 2 to 30 MPa. If the flexural strength is 2 MPa or more, it has sufficient strength and is thus suitably used as a structure, various components, etc. If the flexural strength is 30 MPa or less, it can be easily processed, so that the desired shape can be easily obtained.

[0016] Subsequently, the method for producing a porous carbon-based material of the present invention comprises a raw material step of kneading carbon-based particles and a pitch having a softening point of 70 to 200°C to obtain raw material powder, a molding step of putting the raw material powder into a mold and heating it to a temperature higher than the softening point to obtain a molded body having a predetermined shape, a firing step of firing the molded body, and includes.

[0017] According to the method for producing a porous carbon-based material of the present invention, since carbon-based particles and a pitch having a softening point of 70°C or more are kneaded to obtain raw material powder, they do not adhere to each other at room temperature, and the particle size can be adjusted to a predetermined particle size at room temperature. Further, since a pitch having a softening point of 200°C or less is kneaded, it is not necessary to expose it to a high temperature even when melting the pitch for kneading, and the condensation reaction hardly proceeds at the stage of melting the pitch, and an increase in the softening point can be prevented.

[0018] In addition, in order to obtain a porous carbon-based material, since the fusion action mainly by heat is the center and hardly any pressure is applied, a porous body in which secondary particles having a wide particle size distribution are bonded to each other can be obtained, and continuous pores are easily formed, and the volatile components contained in the raw material powder can be removed without accumulating inside in the subsequent firing step.

[0019] Moreover, the method for producing the porous carbon-based material of the present invention preferably has the following embodiments.

[0020] The method for producing the porous carbon-based material further includes a graphitization step after the firing step.

[0021] By providing the graphitization step, a porous carbon-based material that is chemically stable and has low reactivity can be obtained, and it can be suitably used in applications where graphitic quality is desired.

[0022] In the shaping step, heating is performed for 10 minutes or more.

[0023] By heating for 10 minutes or more in the shaping step, the fusion of the pitch is promoted, and the secondary particles can be surely bonded to each other. Also, in the shaping step, since the raw material powder can be heated directly from the heat source through the mold, fusion can occur earlier than the polymerization of the pitch due to condensation, and strong bonding can be achieved.

[0024] In the firing step, the formed body is fired while being buried in a packing material having an average particle size larger than the average particle size of the raw material powder.

[0025] In the firing step, the pitch is likely to melt and deform, which causes the generation of volatile components from the pitch. However, by burying the formed body in the packing material, deformation is suppressed. Furthermore, since the average particle size of the packing material is coarser (larger) than that of the raw material powder, the generated volatile components can be quickly discharged, and densification due to carbonization of the volatile components in the material and sealing of pores can be prevented, and cracks and foaming can be prevented.

[0026] The average particle size of the raw material powder is 50 to 1500 μm.

[0027] By setting the average particle size of the raw material powder to 50 to 1500 μm, a porous carbon-based material having a large specific surface area and high strength can be obtained.

Advantages of the Invention

[0028] According to the porous carbon-based material of the present invention, since the secondary particles are bonded to each other without being independent, it is difficult for the secondary particles to fall off from the inside of the material, and it is suppressed from coming out of the material.

[0029] Also, according to the method for producing a porous carbon-based material of the present invention, since a carbon-based particle and a pitch having a softening point of 70 °C or higher are kneaded to obtain a raw material powder, they do not adhere to each other at room temperature, and the particle size can be adjusted to a predetermined particle size at room temperature. Furthermore, since a pitch having a softening point of 200 °C or lower is kneaded, it is not necessary to expose the pitch to a high temperature even when melting the pitch for kneading, and it is possible to prevent the softening point from rising because the condensation reaction hardly proceeds at the stage of melting the pitch.

[0030] In addition, in the manufacturing process, a fusion action mainly by heat is used and the material is hardly pressurized, so a porous body in which secondary particles having a wide particle size distribution are bonded to each other can be obtained, and continuous pores are likely to be formed, and the volatile components contained in the raw material powder can be removed without accumulating inside in the subsequent firing process.

Brief Description of the Drawings

[0031]

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Embodiments for Carrying Out the Invention

[0032] To explain the porous carbon-based material and the manufacturing method of the porous carbon-based material of the present invention, Embodiments 1 and 2 of the present invention and the conventional porous carbon-based material and the conventional isotropic graphite material will be described while comparing the manufacturing methods, the structure of the materials, etc.

[0033] Fig. 1(a) shows the manufacturing process of the carbonaceous porous carbon-based material according to Embodiment 1 of the present invention, and Fig. 1(b) shows the manufacturing process of the graphite-based porous carbon-based material according to Embodiment 2 of the present invention.

[0034] As shown in Fig. 1(a), the carbonaceous porous carbon-based material of Embodiment 1 is manufactured through a raw material process of kneading carbon-based particles and a pitch with a softening point of 70 to 200 °C to obtain raw material powder, a molding process of putting the raw material powder into a mold and heating it to a temperature higher than the softening point to obtain a molded body with a predetermined shape, and a firing process of firing the molded body.

[0035] As shown in Fig. 1(b), the graphite-based porous carbon-based material of Embodiment 2 is manufactured through a graphitization process of further graphitizing the carbonaceous porous carbon-based material of Embodiment 1.

[0036] (Raw material process) In the kneading process of the present embodiment, as shown in Fig. 2(a), carbon-based particles and a pitch with a softening point of 70 to 200 °C are kneaded to obtain the raw material powder shown in Fig. 2(b). The raw material powder is an aggregate of particles in which the carbon-based particles are bonded to each other by a binder and corresponds to secondary particles obtained through a firing process or a graphitization process. The carbon-based particles are not particularly limited, and for example, pulverized carbon-based particles such as pitch coke, graphite, and glassy carbon can be used. Among them, pitch coke has good compatibility with pitch and can obtain a strong bond, and can be preferably used as the carbon-based particles of the present invention.

[0037] The raw material powder obtained in the raw material process may be used for molding as it is, but if there is an appropriate particle size range for the porous carbon-based material, the particle size adjustment may be performed in the raw material process. As the method for particle size adjustment, techniques such as classification and pulverization can be used. When performing particle size adjustment by pulverization, by making the carbon-based particles sufficiently smaller than the particle diameter of the raw material powder, the generation of an exposed surface without the adhesion of the binder after pulverization can be prevented.

[0038] The average particle size of the desirable carbon-based particles is 50 to 500 μm. When the average particle size of the carbon-based particles is 50 μm or more, the amount of pitch required in the raw material process can be reduced, and in the subsequent firing process, the disappearance of pores due to the deformation of secondary particles and foaming due to the generated gas can be prevented. The average particle size of the carbon-based particles is preferably 70 μm or more, more preferably 100 μm or more. Also, when the average particle size of the carbon-based particles is 500 μm or less, the generation of exposed surfaces not covered by the binder can be prevented. The average particle size of the carbon-based particles is preferably 400 μm or less. In addition, the average particle size of the carbon-based particles can be measured with a laser diffraction particle size distribution analyzer.

[0039] The pitch used in this embodiment has a softening point of 70 to 200 °C. By kneading the carbon-based particles and the pitch with a softening point of 70 °C or more to obtain the raw material powder, it is possible to suppress the adhesion of the raw material powder at room temperature and adjust the particle size of the raw material powder so as to have a predetermined particle size at room temperature. The softening point is preferably 90 °C or more, more preferably 100 °C or more. Also, by kneading the carbon-based particles and the pitch with a softening point of 200 °C or less to obtain the raw material powder, it is not necessary to expose the raw material powder to a high temperature for kneading, and it is possible to suppress the progress of the condensation reaction at the stage where the pitch melts during kneading and prevent the increase in the softening point. The softening point is preferably 180 °C or less, more preferably 160 °C or less.

[0040] In this embodiment, the kneading temperature is preferably 150 to 300 °C and higher than the softening point of the pitch. By setting the kneading temperature to 150 °C or higher and higher than the softening point of the pitch, the pitch can be sufficiently melted and the carbon-based particles can be bonded to each other. The kneading temperature is more preferably 180 °C or more. By setting the kneading temperature to 300 °C or less, polycondensation of the pitch can be prevented and the moldability of the raw material powder can be ensured. The kneading temperature is more preferably 280 °C or less.

[0041] In addition, in order to obtain a porous carbon-based material, the fusion action mainly by heat is the center and it is hardly pressurized. Therefore, even if the secondary particles have a wide particle size distribution, a porous body in which they are bonded to each other can be obtained, continuous pores are likely to be formed, and the volatile components contained in the raw material powder can be removed without accumulating inside in the subsequent firing process.

[0042] In this embodiment, it is preferable to end kneading at the stage of uniformly mixing while melting the pitch. Specifically, the kneading time is preferably 30 minutes or less. When the kneading time is 30 minutes or less, polycondensation of the pitch can be suppressed and a decrease in the adhesiveness of the raw material powder can be prevented. The kneading time is more preferably 20 minutes or less, and even more preferably 10 minutes or less.

[0043] (Particle size adjustment) The raw material powder (Fig. 2(b)) obtained in the raw material process is preferably subjected to particle size adjustment as necessary. By performing particle size adjustment, a porous carbon-based material with a predetermined porosity and particle size distribution can be obtained. As the method of particle size adjustment, methods such as classification and pulverization can be used. When adjusting the particle size by pulverization, since the raw material powder in which the carbon-based particles are solidified with pitch is pulverized, many secondary particles with an adhesive force in which the carbon-based particles are entangled with pitch are obtained. On the other hand, raw material particles without adhesive force such as those in which the carbon-based particles are broken or the pitch as a binder is peeled off are also obtained at the same time. In the method for producing the porous carbon-based material of the present invention, since it is mainly molded by the fusion action by heat, even such raw material powder without adhesive force can be bonded to each other without being independent.

[0044] The average particle diameter of the raw material powder used in this embodiment is preferably 50 to 1500 μm. When the average particle diameter of the raw material powder is 50 μm or more, pores of sufficient size can be obtained, and a porous carbon-based material that is easy to use for various applications can be obtained. The average particle diameter of the raw material powder is more preferably 80 μm or more, and even more preferably 100 μm or more. When the average particle size of the raw material powder is 1500 μm or less, when it is put into a mold and molded, the size of the unevenness formed on the surface can be reduced, and a porous carbon-based material with a smooth surface can be obtained. The average particle size of the raw material powder is more preferably 1200 μm or less, and even more preferably 1000 μm or less.

[0045] (Forming step) In the forming step of the present embodiment, the obtained raw material powder (Fig. 2(b)) is put into a mold (Fig. 2(c)), heated to a temperature higher than the softening point of the pitch, and a molded body having a predetermined shape shown in Fig. 2(d) is obtained. As shown in Fig. 2(d), in the present embodiment, since it is held in a state of being heated to a temperature higher than the softening point of the pitch, even small raw material powders or raw material powders from which the binder has peeled off are bonded to each other without being released and integrated.

[0046] In the present embodiment, since heat is applied to the raw material powder, even raw material powders without adhesion force can be incorporated into secondary particles and integrated, and the generation of independent and free carbon-based particles can be suppressed.

[0047] In the forming step of the present embodiment, the desirable heating time is 10 minutes or more. Since molding is performed by the action of heat in the forming step, by increasing the heating time, the raw material powder can be softened more and firmly fused. The heating time is more preferably 20 minutes or more, and even more preferably 40 minutes or more.

[0048] The shaping process of this embodiment does not necessarily have to be separately prepared as a shaping process, and the initial stage of the subsequent firing process can be used as the shaping process. For example, as shown in Fig. 9, raw material powder can be put into a strong container, covered, and then buried in a packing material and fired. In Fig. 9(a), a combustible container is filled with raw material powder. In Fig. 9(b), the above-mentioned container is buried in a firing container filled with a packing material. In Fig. 9(c), the temperature is raised, and the raw material powder melts and is shaped and fired to obtain a fired body. The container preferably has air permeability so that the generated product gas does not accumulate, but it may also be a material that becomes air permeable when heated. At the initial stage of firing, the raw material powders fuse with each other and are shaped into a predetermined shape. When the temperature is further increased, the generated product gas passes through the air-permeable container and is discharged to the outside, and at the same time, the shaped body thermally shrinks as the temperature rises. Also, the container is preferably combustible. If the container is combustible, the container will carbonize during the firing process and no longer retain the original shape. Since it is buried in the packing material, the packing material can follow the shrinkage of the shaped body, preventing deformation. As an air-permeable and combustible container, cardboard with a large number of holes drilled to ensure air permeability can be used.

[0049] In addition, in the shaping process of this embodiment, not only heat but also pressure may be used in combination for shaping. By applying pressure, the shape of the mold can be transferred, and a porous carbon-based material with high dimensional accuracy can be obtained.

[0050] Hereinafter, in order to clarify the features of the present invention, the conventional porous carbon-based materials and the conventional dense isotropic carbon-based materials (isotropic graphite materials) will be described, particularly focusing on the shaping process.

[0051] In the conventional porous carbon-based material, carbon-based particles and pitch shown in Fig. 3(a) are kneaded to obtain raw material powder shown in Fig. 3(b). Then, the forming steps shown in Figs. 3(c) and (d) and the firing step shown in Fig. 3(e) are performed. Fig. 3(c) shows the stage before forming, and Fig. 3(d) shows the stage after forming. In the conventional method, the forming steps shown in Figs. 3(c) and (d) are mainly performed by the action of pressure without melting the pitch. Therefore, strong bonding occurs at the contact points of the particles to which pressure is applied, while strong bonding cannot occur at the contact points of the particles to which no pressure is applied. In the production of the porous carbon-based material, since coarse raw material powder is used, large voids are formed at the stage of filling the mold, and it is difficult for sufficient pressure to be applied to the raw material powder that has entered the large voids. For this reason, it cannot be integrated with other particles and becomes free secondary particles, which do not contribute to the strength of the material and become foreign substances that only generate particles.

[0052] Also, in the conventional isotropic graphite material, carbon-based particles and pitch shown in Fig. 4(a) are strongly kneaded to obtain a massive kneaded product as shown in Fig. 4(b). The kneaded product is finely pulverized to obtain raw material powder shown in Fig. 4(c). Then, as shown in Figs. 4(d) and (e), after the raw material powder is formed under high pressure to obtain a formed body, through the firing step shown in Fig. 4(f) and graphitization as necessary, an isotropic graphite material is obtained. Note that Fig. 4(d) shows the stage before forming, and Fig. 4(e) shows the stage after forming.

[0053] In the conventional graphite-based isotropic carbon-based material (isotropic graphite material), since the raw material powder after pulverization is fine, large voids are unlikely to be formed during forming, and since pressure is easily propagated evenly, free particles are unlikely to be generated. Also, since the voids themselves are fine, even if there are secondary particles in a free state, they are confined inside and are unlikely to cause particles.

[0054] (Firing Step) The firing step of the present embodiment according to the present invention heats the obtained formed body (Fig. 2(d)) in an inert atmosphere to obtain a fired body shown in Fig. 2(e). In the present embodiment, the fired body becomes a porous carbon-based material.

[0055] The firing temperature is preferably, for example, 700 to 2000 °C. By performing the firing at 700 °C or higher, volatile components can be sufficiently removed from the molded body, making it possible to use it as a porous carbon-based material. The firing temperature is more preferably 800 °C or higher, and even more preferably 900 °C or higher.

[0056] The carbon-based material has an appropriate graphitization degree according to its use. For example, for electrolytic electrodes, a carbonaceous material with a low graphitization degree is desirable, and for casting, a graphite material with a high graphitization degree is preferred. By performing the firing at 2000 °C or lower, sufficient hardness can be imparted to the porous carbon-based material, and for example, a porous carbon-based material that can be used in electrolytic electrodes can be obtained. The firing temperature is more preferably 1800 °C or lower, and even more preferably 1500 °C or lower.

[0057] In the manufacturing method of the present embodiment according to the present invention, since the raw material powder is softened in the molding step, the pitch is not sufficiently polycondensed at the stage of the raw material step. For this reason, although it contains a large amount of volatile components, since it is porous at the stage after molding, the decomposition gas can be quickly diffused to the outside, preventing densification due to carbonization of the volatile components inside the molded body and sealing of pores, and preventing cracks.

[0058] In the firing step of the present embodiment according to the present invention, it is preferable that the average particle diameter of the packing material is coarser (larger) than that of the raw material powder. When the average particle diameter of the packing material is coarser than that of the raw material powder, the tar-like product generated from the molded body does not stay in the molded body and diffuses quickly, promoting the formation of pores in the porous body.

[0059] The porous carbon-based material obtained through the above steps has secondary particles bonded to each other without being independent at least inside the material, and the presence of free particles is suppressed. Therefore, it is possible to suppress the leakage of particles and fine powder from the surface of the material.

[0060] (Graphitization step) Embodiment 2 (see Fig. 1(b)): After the firing process, graphitization is further performed to obtain a graphitic porous carbon-based material. The temperature of graphitization is preferably 2000 to 3500 °C. By performing graphitization at a temperature of 2000 °C or higher, the machinability is improved, and cutting and machining with hardened steel can be easily performed. Further, by performing graphitization, for example, the corrosion resistance against molten metal or the like can be increased, and the thermal conductivity and thermal shock resistance can be increased, and it can be suitably used also in applications such as metallurgy and casting. The temperature of graphitization is more preferably 2200 °C or higher, and even more preferably 2500 °C or higher.

[0061] In this embodiment, the maximum pore diameter is preferably 50 to 1000 μm. When the maximum pore diameter is 50 μm or more, it can be suitably used in various applications as a porous carbon-based material. The maximum pore diameter is more preferably 80 μm or more, and even more preferably 100 μm or more. When the maximum pore diameter is 1000 μm or less, a sufficient specific surface area can be obtained, and the surface inside the pores can be sufficiently utilized. The maximum pore diameter is more preferably 800 μm or less, and even more preferably 500 μm or less. The maximum pore diameter can be measured by the mercury intrusion method.

[0062] (Example) As carbon-based particles, 100 parts by weight of amorphous pitch coke having an average particle diameter of 300 μm and 25 parts by weight of pitch having a softening point of 150 °C as a binder were used as raw materials and kneaded with a continuous kneader. The temperature of the continuous kneader was set to 250 °C. The pitch introduced into the continuous kneader was quickly melted and mixed with the carbon-based particles to obtain a kneaded product. The kneading time of the continuous kneader was 1 minute, and the pitch hardly advanced polycondensation.

[0063] Next, the obtained kneaded product was roughly pulverized and passed through a 2 mm sieve for particle size adjustment. The average particle diameter of the obtained raw material powder was 900 μm.

[0064] The obtained raw material powder was filled into a metal mold with an opening of 600 x 300 mm and a depth of 80 mm, a metal lid was placed on it, the surroundings were heated to 200°C, and after holding for 120 minutes, the lid was slowly pressed down to adjust the overall shape. The pressure applied at this time was only the weight of the lid, and was 2 kPa.

[0065] After cooling, the mixture was removed from the mold, packed into a calcination can, buried in packing coke with an average particle size of 5 mm, and calcined at 900°C.

[0066] Comparative Example 1 A porous carbon material was produced in the same manner as in the example, except that the molding step was performed at 100° C. under a surface pressure of 15 MPa by stamping.

[0067] Comparative Example 2 60 parts by weight of pitch was added as a binder to 100 parts by weight of amorphous pitch coke with an average particle size of 15 μm as carbon particles, and the mixture was kneaded for 200 minutes. During the kneading process, the pitch polycondensed and its softening point rose to 200° C. or higher. In this comparative example, a powdery raw material powder was not obtained in the raw material process, and a lump-like hard kneaded product was obtained, which could not be used as the raw material powder in the molding process as it is.

[0068] The resulting kneaded material was pulverized to obtain a raw material powder with an average particle size of 25 μm. The raw material powder was filled into a rubber bag and CIP molded at a molding pressure of 100 MPa. The obtained molded body was fired at 900°C to obtain a dense carbonaceous material.

[0069] Table 1 shows the physical properties of the carbonaceous materials obtained in the Examples and Comparative Examples. Fig. 5 shows the pore distributions in the Examples and Comparative Examples. The Examples show a large average pore diameter, although there is no significant difference in porosity between Comparative Examples 1 and 2. The Examples also show a higher bending strength than Comparative Example 1.

[0070] [Table 1]

[0071] Figure 6 shows a polarized light micrograph of the cross-section of the porous carbon-based material obtained in the example. In the structure of the example, the particles fused together with heat during molding and the corners became rounded, and no free secondary particles were observed. Also, even when ultrasonic cleaning was performed using water, no particles were generated from the pores. That is, it is understood that the secondary particles are bonded to each other without being independent.

[0072] Figure 7 shows a polarized light micrograph of the cross-section of the porous carbon-based material obtained in Comparative Example 1. In the porous carbon-based material obtained in Comparative Example 1, fine secondary particles that caused the particles remained inside the pores (free secondary particles). Furthermore, when ultrasonic cleaning was performed using water in the same manner as in the example, the generation of particles from the pores was confirmed.

[0073] Figure 8 shows a polarized light micrograph of the cross-section of the carbon-based material obtained in Comparative Example 2. In the dense carbon-based material obtained in Comparative Example 2, there were no large pores in the first place, and the presence of free secondary particles that caused the particles could not be confirmed. Even if free secondary particles were present, it is considered that they were confined inside fine pores and were difficult to flow out to the outside. In addition, when ultrasonic cleaning was performed using water in the same manner as in the example, the generation of particles from the pores was confirmed. It is presumed that the particles inside the pores were drawn out by the strong cleaning power.

Claims

1. A porous carbon-based material in which carbon-based particles and a carbonaceous binder that binds the carbon-based particles to each other constitute secondary particles, The secondary particles are bonded to each other without being independent, The porous carbon-based material has a maximum pore diameter of 50 to 1000 μm.

2. The porous carbon-based material according to claim 1, having a bulk density of 1.0 to 1.5 g / cm ３ 3.

3. The porous carbon-based material according to claim 1 or 2, having a flexural strength of 2 to 30 MPa.

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