JP5939543B2 - Method for producing porous carbon material - Google Patents

Description

  The present invention relates to a method for producing a porous carbon material.

  Carbon materials are useful in various industrial fields because they exhibit excellent heat resistance and high temperature strength in a non-oxidizing atmosphere and have high conductivity and chemical stability. In addition, the porous carbon material having an increased porosity is excellent in gas permeability and lightness, and thus is used in applications such as various filters, fuel cells, and heat insulating materials. As the heat insulating material, for example, vacuum It is used as a heat insulating material of a high-temperature heat treatment furnace for a reduced pressure atmosphere such as a non-oxidizing atmosphere.

  Of the above carbon materials, the use of a porous carbon material for the purpose of enhancing gas permeability has been studied. For example, a porous carbon material in which carbon short fibers or carbon black is used as a skeleton material and bound with a resin. Is being considered.

  As a method for producing the porous carbon material, for example, a short carbon fiber and a cellulose fiber for a binder are wet-papered to form a sheet and impregnated with a phenol resin to prepare a prepreg, and the obtained prepreg is laminated, There has been proposed a method in which a porous molded body is obtained by hot pressing and then fired (see Patent Document 1 (Japanese Patent Laid-Open No. 5-194056)).

  Further, as a method for producing the porous carbon material, the self-curing modified novolak resin and the carbon fiber are sufficiently stirred in an aqueous medium, uniformly dispersed, formed into a sheet by a sheet machine, dehydrated and dried, and then heated. There has been proposed a method in which a low-density molded body is formed by pressure molding and then fired (see Patent Document 2 (Japanese Patent Laid-Open No. 6-122570)).

  However, the porous carbon material formed by laminating the sheeted material as described above has low strength (bending strength) in the laminating direction because it is difficult to obtain sufficient adhesion between the main surfaces of the sheet. There was a technical problem that could only be obtained.

Japanese Patent Laid-Open No. 5-194056 JP-A-6-122570

  As a method for producing a porous carbon material having high strength in the laminating direction, a shape corresponding to the porous carbon material to be obtained is obtained by mixing carbon short fibers and binder resin powder in a volatile solvent and hot pressing. A method of firing after obtaining a molded body having the above is also conceivable.

  However, in this method, short carbon fibers are aggregated into a bundle to form a fiber bundle, so that the dispersibility of the short carbon fibers, which are the skeleton material, is reduced, and a porous carbon material having sufficient strength is obtained. I can't.

  In order to suppress the agglomeration of the above short carbon fibers, a method of dry mixing the short carbon fibers and the binder resin powder is also conceivable. However, the dry mixing of the short carbon fibers and the binder resin powder is longer than the wet mixing. It requires mechanical mixing for a long time, is easy to cause breakage of short carbon fibers and flocculent aggregation, and can be uniformly dispersed with a mixer or the like to prepare a mixture in which short carbon fibers and binder resin powder are in close contact with each other. Even when the obtained mixture is taken out of the container or the subsequent treatment, the short carbon fibers and the binder resin powder are easily separated and scattered, It turned out that it was difficult to manufacture easily.

  Under such circumstances, the present invention provides a method for easily producing a porous carbon material in which short carbon fibers are uniformly dispersed, excellent in bending strength, and having conductivity and heat insulation controlled within a desired range. Is intended to provide.

As a result of intensive studies by the present inventors in order to solve the above technical problem, 30 to 250 parts by mass of thermosetting resin powder is added to 100 parts by mass of carbon short fibers having an average fiber length of 0.3 to 50 mm. While spraying and adding 5 to 40 parts by mass of water to 100 parts by mass of short fibers, the mixture powder is stirred and mixed by dry mixing to form a mixed powder, and the obtained mixed powder is hot-pressed, It is found that the above problem can be solved by performing a heat treatment at 300 to 3000 ° C. in a non-oxidizing atmosphere to obtain a porous carbon material having a bulk density of 0.15 to 1.20 g / cm ^3. Based on this, the present invention has been completed.

That is, the present invention
(1) 30 to 250 parts by mass of thermosetting resin powder with respect to 100 parts by mass of carbon short fibers having an average fiber length of 0.3 to 50 mm, and 5 to 40 parts by mass of water with respect to 100 parts by mass of the carbon short fibers. While mixing by spraying, stirring and mixing by dry mixing to form a mixed powder,
After hot pressing the obtained mixed powder,
Heat treatment is performed at 300 to 3000 ° C. in a non-oxidizing atmosphere,
A method for producing a porous carbon material, characterized by obtaining a porous carbon material having a bulk density of 0.15 to 1.20 g / cm ³ ;
(2) The method for producing a porous carbon material according to (1), wherein the carbon short fibers are polyacrylonitrile-based carbon short fibers from which a surface sizing agent has been removed in advance.
(3) The specific resistivity of the obtained porous carbon material is 100 to 100,000 μΩ · m, and the thermal conductivity is 0.2 to 3.0 W / m · K, as described in (1) or (2) above A method for producing a porous carbon material is provided.

  According to the present invention, there is provided a method for easily producing a porous carbon material in which short carbon fibers are uniformly dispersed, has excellent bending strength, and has conductivity and heat insulation controlled within a desired range. Can do.

In the method for producing a porous carbon material of the present invention, 30 to 250 parts by mass of thermosetting resin powder is added to 100 parts by mass of the carbon short fibers with respect to 100 parts by mass of carbon short fibers having an average fiber length of 0.3 to 50 mm. On the other hand, while adding 5 to 40 parts by mass of water by spraying, the mixture is stirred and mixed by dry mixing to form a mixed powder. Heat treatment is performed at ˜3000 ° C. to obtain a porous carbon material having a bulk density of 0.15 to 1.20 g / cm ³ .

  In the production method of the present invention, the carbon short fiber is not particularly limited. For example, a polyacrylonitrile carbon fiber obtained by carbonizing a polyacrylonitrile fiber, a pitch carbon fiber obtained by carbonizing a pitch fiber, and a rayon system. One or more types selected from rayon-based carbon fibers obtained by carbonizing fibers, phenol resin-based carbon fibers formed by carbonizing phenol resin fibers, and the like can be given.

In the production method of the present invention, the short carbon fiber has an average fiber length of 0.3 to 50 mm, preferably 1 to 30 mm, and more preferably 3 to 25 mm.
When the average fiber length of the short carbon fiber is shorter than 0.3 mm, the filling property of the short carbon fiber is improved (the carbon fiber is easily filled), the bulk density of the obtained porous carbon material is increased, and the heat insulating performance. Tends to decrease. On the other hand, when the average fiber length of the short carbon fibers exceeds 50 mm, the carbon fibers become bulky, and it becomes difficult to uniformly fill the mold, so that variations in the characteristics of the obtained porous carbon material tend to increase.

  In addition, in this application document, the average fiber length of carbon short fiber means the arithmetic mean value when the fiber length of 20 carbon short fibers selected arbitrarily is measured by image analysis using a microscope.

In the production method of the present invention, the fiber diameter (fiber cross-sectional diameter) of the short carbon fiber is preferably 1 to 15 μm, and more preferably 5 to 10 μm.
In addition, in this application document, the cross-sectional diameter of the short carbon fiber is measured by image analysis using a scanning electron microscope for the cross-sectional diameter of 10 carbon short fibers arbitrarily selected (maximum diameter of the short carbon fiber cross-section). It means the arithmetic average value.

  In the production method of the present invention, the short carbon fibers are preferably those obtained by removing the surface sizing agent in advance.

  As the carbon fiber, for the purpose of imparting appropriate bundling property to the carbon fiber, one having a surface provided with a sizing agent mainly composed of various thermoplastic resins is widely used. In, by using short carbon fibers from which the surface sizing agent has been removed in advance, uniform dispersion of the short carbon fibers in the thermosetting resin powder can be easily performed.

Examples of the method for removing the sizing agent include a method of washing with an organic solvent compatible with the sizing agent in addition to the heat treatment.
When removing the sizing agent by heat treatment, heat treatment may be performed at a temperature equal to or higher than the decomposition temperature of the sizing agent so as not to damage the short carbon fibers, for example, heating at 300 to 400 ° C. in an oxidizing atmosphere, The method of heat-processing at 600-1000 degreeC in non-oxidizing atmosphere can be mentioned.
In the case where the sizing agent is washed with an organic solvent, for example, an organic solvent compatible with the sizing agent such as acetone, methanol, ethanol or the like is appropriately selected, and then a washing treatment method such as a dipping method can be used.

In the production method of the present invention, the thermosetting resin powder is stirred and mixed with the short carbon fibers.
In the production method of the present invention, the thermosetting resin constituting the thermosetting resin powder is not particularly limited. For example, a phenolic resin represented by a resol type phenol resin, a novolac type phenol resin, or furfuryl. Furan resins such as alcohol resin, furfuryl alcohol furfural resin, furfuryl alcohol phenol resin, polyimide resin, polycarbodiimide resin, polyacrylonitrile resin, pyrene-phenanthrene resin, polyvinyl chloride resin, bifunctional aliphatic alcohol ether type epoxy Resins and epoxy resins such as polyfunctional phenol type epoxy resins, urea resins, diallyl phthalate resins, unsaturated polyester resins, melamine resins, etc. can be mentioned, and these can be used alone or in combination of two or more. It can be.

  In the production method of the present invention, as the thermosetting resin constituting the thermosetting resin powder, a phenolic resin or an epoxy resin having a residual carbon ratio of 40% or more is preferably used from the viewpoint of moldability and price. it can.

In the production method of the present invention, the average particle size of the thermosetting resin powder is preferably 5 to 100 μm, more preferably 10 to 80 μm, and still more preferably 20 to 50 μm.
If the average particle size of the thermosetting resin powder is less than 5 μm, the fine powdered thermosetting resin will be secondary agglomerated, making it difficult to uniformly disperse the short carbon fibers, and thermosetting. When the average particle diameter of the resin powder exceeds 100 μm, the thermosetting resin powder is unevenly distributed during the stirring and mixing, and the characteristic variation of the obtained porous carbon tends to increase.
In the case of using a block-shaped or marble-shaped (large average particle diameter) thermosetting resin as a production raw material, a thermosetting resin powder having a desired average particle diameter is prepared by performing a treatment such as pulverization. be able to.

  In addition, in this application document, the measurement of the average particle diameter of a thermosetting resin powder means the value measured using the laser diffraction type particle size distribution measuring apparatus (Shimadzu Corporation SALD-2100).

  In the production method of the present invention, the thermosetting resin powder functions as a binder for binding the short carbon fibers by heat curing, and is porous that is carbonized during heat treatment and integrated with the short carbon fibers. Form a carbon material.

In the production method of the present invention, when the short carbon fibers and the thermosetting resin powder are mixed with stirring, a phenol resin curing agent may be further mixed.
The phenol resin curing agent is not particularly limited as long as it has a phenol structure in the molecule, and novolak such as phenol novolac resin, cresol novolac resin, xylene type phenol resin, dicyclopentadiene type phenol resin, bisphenol type novolac resin, etc. Resin, bisphenols such as bisphenol A, bisphenol F, bisphenol S, tetrabromobisphenol A, the bisphenols are polymerized with diglycidyl ether of the bisphenols, or the latter is an excess of epichlorohydrin and the above bisphenols And bisphenol-based resins obtained by reacting with the above.

In the production method of the present invention, when the carbon short fibers and the thermosetting resin powder are mixed with stirring, a curing accelerator may be further mixed.
Examples of the curing accelerator include one or more selected from phosphorus compounds, tertiary amines, imidazoles, organic acid metal salts, Lewis acids, amine complex salts, and the like.

In the production method of the present invention, 30 to 250 parts by mass of thermosetting resin powder is agitated and mixed with 100 parts by mass of short carbon fibers having an average fiber length of 0.3 to 50 mm to form a mixed powder.
In the production method of the present invention, it is preferable that 40 to 240 parts by mass of thermosetting resin powder is stirred and mixed with 100 parts by mass of short carbon fibers having an average fiber length of 0.3 to 50 mm to form a mixed powder.

When the amount of the thermosetting resin powder used is within the above range, a porous carbon material having a desired porosity and strength can be obtained.
When the amount of the thermosetting resin powder used is less than 30 parts by mass with respect to 100 parts by mass of the short carbon fibers, not only the moldability is likely to deteriorate, but also a binder made of the thermosetting resin powder during the heat treatment described later. The force is reduced, and it becomes difficult to maintain the shape of the obtained molded body. Moreover, when the usage-amount of a thermosetting resin powder exceeds 250 mass parts with respect to 100 mass parts of carbon short fibers, the specific resistance value of the obtained porous carbon material becomes large, and it becomes easy to reduce electroconductivity.

In the production method of the present invention, when a phenol resin curing agent is further mixed at the time of mixing the short carbon fibers and the thermosetting resin powder, the phenol resin curing agent is, for example, a polyfunctional phenol type epoxy as a thermosetting resin powder. When resin powder is used, the equivalent ratio of all phenolic hydroxyl groups in the phenol resin to all epoxy groups in the epoxy resin (total phenolic hydroxyl groups in the phenol resin / total epoxy groups in the epoxy resin) is 0.7 to 1. It is preferable to mix so that it may become 0.5, It is more preferable to mix so that it may become 0.9-1.1, It is further more preferable to mix so that it may become about 1.0.
When the equivalent ratio is less than 0.7 or exceeds 1.5, the residual amount of unreacted thermosetting resin powder or phenol resin curing agent increases, and the thermosetting efficiency is lowered.

  In the production method of the present invention, when a curing accelerator is further mixed at the time of mixing the short carbon fibers and the thermosetting resin powder, the curing accelerator is, for example, a polyfunctional phenol type epoxy resin as a thermosetting resin powder. When using powder, it can add normally in 0.05-3 mass parts with respect to 100 mass parts of thermosetting resin powder.

  In the production method of the present invention, the method of mixing the short carbon fibers and the thermosetting resin powder is not particularly limited as long as the short carbon fibers and the thermosetting resin powder can be uniformly stirred and mixed by dry mixing. It can carry out using a well-known stirring apparatus.

As said stirring apparatus, the apparatus which has the stirring blade for mixing in a stirring container can be mentioned, For example, 1 or more types chosen from a high speed mixer, a Laedige mixer, a Henschel mixer, etc. can be mentioned.
In the production method of the present invention, the stirring time in the stirring and mixing is not particularly limited as long as the short carbon fibers and the thermosetting resin powder can be stirred and mixed uniformly. For example, 30 to 300 seconds is preferable. . Moreover, it is preferable that the rotation speed of the stirring apparatus at the time of the said stirring and mixing is about 100 to 1000 rotations / minute.

  In the production method of the present invention, the short carbon fiber and the thermosetting resin powder are mixed with stirring in the presence of 5 to 40 parts by mass of water with respect to 100 parts by mass of the carbon fiber. It is preferable to carry out in the presence of ~ 35 parts by mass of water, more preferably in the presence of 15 to 30 parts by mass of water.

By stirring and mixing the carbon short fibers and the thermosetting resin powder in the presence of 5 to 40 parts by mass of water with respect to 100 parts by mass of the carbon fibers, the carbon short fibers and the curable resin powder are strengthened. When the mixed powder obtained by stirring and mixing is discharged from the mixer or put into a mold and moved, the thermosetting resin powder is separated from the carbon short fibers and scattered. It can be effectively suppressed.
When the amount of water used in the stirring and mixing is less than 5 parts by mass with respect to 100 parts by mass of carbon fiber, it becomes difficult to fix the short carbon fibers and the thermosetting resin powder, and the amount exceeds 40 parts by mass. In this case, the surface tension of water tends to cause the carbon fibers to be oriented in one direction to be bundled (easy to be bundled), resulting in variations in characteristics of the obtained porous carbon material.

  In the production method of the present invention, the stirring and mixing of the carbon short fibers and the thermosetting resin powder is stirred and mixed while water is sprayed and added to the carbon short fibers and the thermosetting resin powder.

The method of spraying water on the short carbon fibers and the thermosetting resin powder is not particularly limited as long as it is a method capable of spraying uniformly on the stirring target, and spraying so that the spray droplets are as fine as possible. It is preferable to spray so that the average diameter of the spray droplets is 20 μm or less.
The apparatus for spraying water on the short carbon fiber and the thermosetting resin powder is not particularly limited, and is selected from, for example, a one-fluid nozzle such as a fogger, a two-fluid nozzle using a gas as a spray medium, and an ultrasonic atomizing nozzle. One or more of these may be mentioned.

  The time for spraying water on the short carbon fiber and the thermosetting resin powder is not particularly limited as long as it is shorter than the stirring and mixing time of the short carbon fiber and the thermosetting resin powder, and is, for example, 15 to 60 seconds. It is preferable.

  In the production method of the present invention, a mixed powder containing fixed powder in which the short carbon fibers and the thermosetting resin powder are fixed can be formed by the stirring and mixing.

In the production method of the present invention, the bulk density of the powder mixture is preferably 0.005~0.2g / cm ^3, more preferably 0.01~0.15g / cm ^3, 0. More preferably, it is 05-0.1 g / cm < ³ >.
In this application document, the bulk density of the mixed powder is determined by filling the mixed powder into a container with a known volume, measuring the mass (g), and dividing the mass by the volume (cm ³ ) of the container. Means the value calculated by.

  In the production method of the present invention, the mixed powder is hot-press molded.

In the production method of the present invention, the hot pressing is preferably performed in a molding die having a molding surface corresponding to the shape of the porous carbon material to be obtained.
In the production method of the present invention, the amount of the mixed powder charged into the mold during hot pressing is the volume of the porous carbon material obtained after the heat treatment described later, taking into account the residual carbon ratio of the thermosetting resin powder. The density is controlled to be 0.15 to 1.20 g / cm ³ .

  In the production method of the present invention, the molding temperature and molding time at the time of hot-pressure molding are temperatures at which the thermosetting resin powder is melted to bind the short carbon fibers together, and the resulting binder can be handled. If there is no particular limitation.

  120-250 degreeC is preferable, for example, the molding temperature at the time of hot-pressure shaping | molding has more preferable 130-220 degreeC, and 150-200 degreeC is further more preferable. Further, the molding time at the time of hot pressing is preferably 5 to 60 minutes, more preferably 7 to 45 minutes, and further preferably 10 to 30 minutes.

  The molding pressure at the time of hot-pressure molding is suitably about 1 MPa or more and less than 20 MPa, more preferably 1 MPa to 15 MPa, and further preferably 1 MPa to 10 MPa. Further, the obtained hot-pressed product may be further machined as necessary, and may be appropriately cured at a temperature of about 200 to 300 ° C. as necessary.

In the production method of the present invention, heat treatment is performed at 300 to 3000 ° C. in a non-oxidizing atmosphere after the hot pressing process.
Examples of the non-oxidizing atmosphere include a vacuum atmosphere and a nitrogen atmosphere in addition to a rare gas atmosphere such as an argon gas atmosphere and a helium gas atmosphere.
The heat treatment temperature is preferably 700 to 3000 ° C, more preferably 1500 to 2800 ° C.
The time for performing the heat treatment is preferably 1 to 36 hours, more preferably 2 to 24 hours, and further preferably 3 to 12 hours.

In the production method of the present invention, a sufficiently calcined and carbonized porous carbon material can be obtained by performing the heat treatment subsequent to the hot pressing process.
When the heat treatment temperature is less than 300 ° C., carbonization is insufficient and organic matter tends to remain, whereas when the heating temperature exceeds 3,000 ° C., graphitization proceeds and post-processing becomes difficult.
In the production method of the present invention, the target porous carbon material can be obtained by performing the heat treatment, and secondary processing may be performed as necessary.

In the production method of the present invention, the resulting porous carbon material, bulk density, a 0.15~1.20g / cm ^3, it is preferable that 0.15~1.0g / cm ^3.

  In the production method of the present invention, the bulk density of the obtained porous carbon material is the average fiber length of the short carbon fibers, the average particle diameter of the thermosetting resin powder, the mixing amount of the short carbon fibers and the thermosetting resin powder, It can be adjusted to a desired range by controlling the pressure during pressure forming.

  In the production method of the present invention, the porous carbon material has the bulk density of the porous carbon material controlled within the above range, so that the porous carbon material has gas permeability, specific resistivity, thermal conductivity, and the like within a desired range. The material can be provided easily.

In addition, in the manufacturing method of this invention, a bulk density shall mean the value calculated by a following formula.
Bulk density (g / cm ³ ) = mass of porous carbon material (g) / dimensional volume of porous carbon material (cm ³ )

  In the production method of the present invention, the obtained porous carbon material is suitably one having a specific resistivity of 100 to 100,000 μΩ · m, more preferably 100 to 10,000 μΩ · m, More suitable is 100 to 1,000 μΩ · m.

  In the production method of the present invention, when the specific resistivity is within the above range, a porous carbon material having desired conductivity can be provided.

  In this application document, the specific resistivity of the porous carbon material is measured in the longitudinal direction at room temperature on a test piece having a length of 30 mm, a width of 30 mm, and a thickness of 2 to 5 mm according to the four-terminal voltage drop method. It means a value measured when a voltage drop of 0.5 to 3.0 mm between terminals is measured with a surface pressure of 1 MPa and a direct current of 1.0 A.

  In the production method of the present invention, it is appropriate that the obtained porous carbon material has a thermal conductivity of 0.2 to 3.0 W / m · K, and 0.2 to 2.0 W / m · K. Some are more suitable, and those with 0.2 to 1.0 W / m · K are even more suitable.

  In the production method of the present invention, when the thermal conductivity is in the above range, a porous carbon material having desired heat insulation can be provided.

  In addition, in this application document, the thermal conductivity of the porous carbon material is a laser flash method using a thermal constant measuring device (TC-7000, manufactured by ULVAC-RIKO) for a test piece having a diameter of 10 mm and a thickness of 1 to 2 mm. It shall mean the value when measured by.

  In the production method of the present invention, the porous carbon material to be obtained is suitably one having a porosity of 40 to 90%, more preferably 50 to 80%, and 60 to 70%. Is more appropriate.

  In the production method of the present invention, when the porosity is within the above range, a porous carbon material having desired gas permeability can be provided.

In the present application documents, the porosity (%) is the percentage of the pore volume to the total volume of the porous carbon material, expressed as a percentage, and the dry weight W (g) and volume V of the porous carbon material. (Cm ³ ) is measured, then the porous carbon material is powdered and the true density ρ (g / cm ³ ) of the porous carbon material is measured, and the value calculated by the following formula is meant And
Porosity (%) = [1-W / (ρ × V)] × 100

  According to the present invention, there is provided a method for easily producing a porous carbon material in which short carbon fibers are uniformly dispersed, has excellent bending strength, and has conductivity and heat insulation controlled within a desired range. Can do.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

Example 1
Thermosetting phenol resin powder (Gunei Chemical Industry Co., Ltd.) having an average particle size of 40 μm with respect to 100 parts by mass of polyacrylonitrile-based short carbon fibers (cut fiber T-008 manufactured by Toray Industries, Inc.) having an average fiber length of 6 mm and a fiber diameter of 7 μm 100 parts by mass of Residtop PGA-2411 manufactured by Co., Ltd. was charged into a high speed mixer, and 20 parts by mass of water was added to 100 parts by mass of the short carbon fibers using a commercially available fogger nozzle (Sauter average particle size: 15 μm). A mixed powder was formed by carrying out a stirring and mixing treatment for 5 minutes at a stirring speed of 60 times / minute while spraying. The obtained mixed powder does not agglomerate short carbon fibers by the above stirring and mixing, and the short carbon fibers and the thermosetting resin powder are fixed while the short carbon fibers are uniformly diffused in the thermosetting resin powder. It was something that was made.
An amount of 0.8 g / cm ³ of porous carbon material obtained from the obtained mixed powder is sampled and charged into a mold having a predetermined molding surface shape, and at a temperature of 180 ° C., 5 MPa A hot-pressure molded product having a length of 250 mm, a width of 250 mm, and a height of 6 mm was obtained by performing a hot-pressure molding treatment at a molding pressure of 20 mm.
When the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into a mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed.
The above hot-pressed product was heat-treated at 2000 ° C. for 5 hours under a nitrogen atmosphere to obtain a target porous carbon material.
The production conditions are described in Table 1, and the bulk density, volume resistivity and thermal conductivity of the obtained porous carbon material are shown in Table 2.

(Example 2)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 3 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle 40 parts by mass of a thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was added to a high speed mixer and mixed by stirring. From the obtained mixed powder, 0.2 g / The target porous carbon material was obtained in the same manner as in Example 1 except that the amount of the cm ³ porous carbon material obtained was collected and hot-press molded.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

(Example 3)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 12 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle 240 parts by mass of a thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was added to a high-speed mixer and mixed by stirring. From the obtained mixed powder, 0.9 g / The target porous carbon material was obtained in the same manner as in Example 1 except that the amount of the cm ³ porous carbon material obtained was collected and hot-press molded.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

Example 4
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 6 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle size 100 mass parts of thermosetting phenol resin powder (Gunei Chemical Industry Co., Ltd., Residtop PGA-2411) having a diameter of 40 μm was put into a high-speed mixer, and a commercially available fogger nozzle (Sauter average particle diameter: 15 μm) was used. Stirring and mixing while spraying 35 parts by mass of water with respect to 100 parts by mass of the short carbon fibers, and collecting 1.2 g / cm ³ of porous carbon material from the obtained mixed powder. A target porous carbon material was obtained in the same manner as in Example 1 except that hot pressing was performed.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

(Example 5)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 3 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle 40 parts by mass of a thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was put into a high-speed mixer, and a commercially available fogger nozzle (Sauter average particle size: 15 μm) was used. Stirring and mixing while spraying 7 parts by mass of water with respect to 100 parts by mass of the carbon short fibers, and collecting 0.2 g / cm ³ of a porous carbon material from the obtained mixed powder. A target porous carbon material was obtained in the same manner as in Example 1 except that hot pressing was performed.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

(Example 6)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 6 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle size Except for changing the heat treatment temperature from 2000 ° C to 700 ° C by adding 100 parts by weight of thermosetting phenol resin powder with a diameter of 40 µm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) to a high speed mixer and stirring and mixing. Obtained a porous carbon material of interest as in Example 1.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

(Example 7)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 48 mm and a fiber diameter of 7 μm from which a sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle size 150 parts by mass of thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was put into a high speed mixer and mixed by stirring. From the obtained mixed powder, 1.0 g / The target porous carbon material was obtained in the same manner as in Example 1 except that the amount of cm ³ porous carbon material was obtained and hot-press molded and the heat treatment temperature was changed from 2000 ° C. to 300 ° C. Obtained.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

(Example 8)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 6 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle size 150 parts by mass of thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was added to a high speed mixer and mixed by stirring. From the obtained mixed powder, 0.9 g / The target porous carbon material was obtained in the same manner as in Example 1 except that the amount of the obtained cm ³ porous carbon material was collected and hot-press molded, and the heat treatment temperature was changed from 2000 ° C. to 1000 ° C. Obtained.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
A porous carbon material was prepared in the same manner using polyacrylonitrile-based short carbon fibers that had been washed away with acetone instead of removing the sizing agent by heat treatment, but the polyacrylonitrile-based carbon from which the sizing agent was removed by heat treatment was used. There was no difference in properties from the porous carbon material obtained using short fibers.

Example 9
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 6 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle size 150 parts by mass of epoxy resin powder having a diameter of 30 μm (Pernox Co., Ltd., Perpowder PCE-750) was charged into a high-speed mixer and mixed by stirring. From the obtained mixed powder, 0.9 g / cm ³ of porous material was obtained. The target porous carbon material was obtained in the same manner as in Example 1 except that the amount of carbon material obtained was collected and hot-press molded and the heat treatment temperature was changed from 2000 ° C to 1000 ° C.
The mixed powder obtained in the stirring and mixing process does not agglomerate the short carbon fibers by the stirring and mixing, and the short carbon fibers and the thermosetting resin are uniformly diffused in the thermosetting resin powder. The resin powder was fixed.
Further, when the fixed matter of the short carbon fiber and the thermosetting resin powder was taken out from the high-speed mixer, inserted into the mold and subjected to hot-pressure molding, scattering due to separation of the fixed matter was not confirmed. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.

(Comparative Example 1)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 3 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle 70 parts by mass of thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was put into a high-speed mixer and stirred and mixed without spraying water. A target porous carbon material was obtained in the same manner as in Example 1 except that an amount of 0.9 g / cm ³ of porous carbon material obtained from the body was collected and subjected to hot pressing.
In the mixed powder obtained in the stirring and mixing process, the short carbon fibers and the thermosetting resin powder are not sufficiently fixed, and the thermosetting resin powder scatters when the mixture is taken out from the mixer. Even when the mixed powder was filled in the mold, the thermosetting resin powder was non-uniform, falling to the bottom.
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
In addition, when the above-mentioned porous molded body was repeatedly produced and the reproducibility of the characteristics of the porous carbon material was confirmed, the specific resistance value and the thermal conductivity varied greatly, and could not be put to practical use. there were.

(Comparative Example 2)
For 100 parts by mass of polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 12 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle 140 parts by mass of thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was put into a high-speed mixer, and 45 parts by mass of water with respect to 100 parts by mass of the carbon short fibers. In the same manner as in Example 1, except that the amount of the porous carbon material of 0.5 g / cm ³ obtained from the mixed powder was collected by hot pressure molding. The intended porous carbon material was obtained.
In the mixed powder obtained in the stirring and mixing process, short carbon fibers aggregated in a bundle like the wet mixing process, and were dispersed non-uniformly in the thermosetting resin powder. .
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
In addition, when the above-mentioned porous molded body was repeatedly produced and the reproducibility of the characteristics of the porous carbon material was confirmed, the specific resistance value and the thermal conductivity varied greatly, and could not be put to practical use. there were.

(Comparative Example 3)
For 100 parts by mass of a polyacrylonitrile-based carbon short fiber (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 0.1 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in advance in a nitrogen atmosphere, 80 parts by mass of thermosetting phenol resin powder having an average particle size of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) was charged into a high speed mixer and mixed by stirring. The target porous carbon was obtained in the same manner as in Example 1 except that an amount of 4 g / cm ³ of porous carbon material was obtained and subjected to hot pressing, and the heat treatment temperature was changed from 2000 ° C. to 2200 ° C. I got the material.
The manufacturing conditions are shown in Table 1, and the bulk density, volume resistivity and thermal conductivity are shown in Table 2 as characteristics of the obtained porous carbon material.
The obtained porous carbon material had a bulk density as large as 1.4 g / cm ³ and a thermal conductivity as large as 2.6 W / m · K, and thus the desired heat insulation performance could not be obtained.

(Comparative Example 4)
For 100 parts by mass of polyacrylonitrile-based carbon short fibers (cut fiber manufactured by Toray Industries, Inc.) having an average fiber length of 100 mm and a fiber diameter of 7 μm from which the sizing agent has been removed by heat treatment at 600 ° C. in a nitrogen atmosphere in advance, the average particle The object is the same as in Example 1 except that 200 parts by mass of thermosetting phenol resin powder having a diameter of 40 μm (Resitop PGA-2411 manufactured by Gunei Chemical Industry Co., Ltd.) is put into a high speed mixer and stirred and mixed. When trying to obtain a porous carbon material, the mixed powder obtained by stirring and mixing was bulky and could not be hot-press molded.
The production conditions are listed in Table 1.

The porous carbon materials obtained in Examples 1 to 9 are high because they are formed by hot pressing and integrating the short carbon fibers in a state of being uniformly dispersed between the thermosetting resins. While having bending strength, it was excellent in gas permeability from being porous.
The porous carbon materials obtained in Examples 1 to 9 were mixed with a predetermined amount of carbon short fibers having a predetermined average fiber length and a thermosetting resin powder with stirring to form a mixed powder. Since the obtained mixed powder has been subjected to hot-press molding and heat treatment in a non-oxidizing atmosphere so as to have a bulk density in a predetermined range, it has predetermined electrical conductivity and heat insulation Met.
Furthermore, in Example 1 to Example 9, it is possible to easily produce a porous carbon material while suppressing the aggregation of short carbon fibers and the occurrence of scattering of short carbon fibers and thermosetting resin powder in the production process. it can.

  On the other hand, in Comparative Example 1, since the mixed powder was produced without spraying water, the short carbon fiber and the thermosetting resin powder were not sufficiently fixed, and the mold was removed when being taken out from the mixer. The thermosetting resin powder was scattered at the time of charging, and the porous carbon material could not be easily produced. Further, since the mixed powder is not uniform, the characteristics of the obtained porous carbon material vary, and cannot be put to practical use.

  Further, in Comparative Example 2, since the spray amount of water was too large, the short carbon fibers aggregated and a uniform mixed powder could not be obtained. For this reason, the characteristics of the obtained porous carbon material vary, and cannot be put to practical use.

In Comparative Example 3, a predetermined amount of a mixed powder obtained by using short carbon fibers having an average fiber length as short as 0.1 mm was weighed and heated so that the bulk density was as high as 1.4 g / cm ^3. Since the pressure forming treatment and the heat treatment were performed, only a porous carbon material having a thermal conductivity of 2.6 W / m · K and a poor heat insulating property was obtained.

  In Comparative Example 4, since the mixed powder was prepared using carbon short fibers having a large average fiber length of 100 mm, the mixed powder became bulky and could not be hot-press molded.

  The porous carbon material obtained in Examples 1 to 9 can be suitably used as, for example, an electrode material for a fuel cell or a separator material.

  According to the present invention, there is provided a method for easily producing a porous carbon material in which short carbon fibers are uniformly dispersed, has excellent bending strength, and has conductivity and heat insulation controlled within a desired range. It is intended.

Claims (3)

30 to 250 parts by mass of thermosetting resin powder is sprayed on 100 parts by mass of carbon short fibers having an average fiber length of 0.3 to 50 mm, and 5 to 40 parts by mass of water is sprayed on 100 parts by mass of carbon short fibers. While mixing, agitation and mixing by dry mixing to form a mixed powder,
After hot pressing the obtained mixed powder,
Heat treatment is performed at 300 to 3000 ° C. in a non-oxidizing atmosphere,
A method for producing a porous carbon material, comprising obtaining a porous carbon material having a bulk density of 0.15 to 1.20 g / cm ³ .   The method for producing a porous carbon material according to claim 1, wherein the carbon short fibers are polyacrylonitrile-based carbon short fibers from which a surface sizing agent has been previously removed.   The porous carbon material according to claim 1 or 2, wherein the obtained porous carbon material has a specific resistivity of 100 to 100,000 µΩ · m and a thermal conductivity of 0.2 to 3.0 W / m · K. Manufacturing method.