JPH07101609B2 - Method for manufacturing a flat ribbed porous carbon material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a ribbed, flat, porous carbon material containing carbon fibers, which has improved electrical and thermal conductivity in the thickness direction and high strength and can be advantageously used as an electrode substrate for a fuel cell.

BACKGROUND ART A fuel cell electrode plate having low electrical resistance is known, which is made of a material mainly made of carbon fiber and having numerous small holes for gas diffusion, and in which the thin walled portion formed in the plate-like body serves as a flow path for fuel and oxidant gas, and the thick walled portion functions as a current collector, and the carbon fibers forming the current collector are made of independent single fibers whose fiber axes are oriented substantially in the thickness direction of the thick walled portion (Japanese Patent Laid-Open Publication No. 57-210571). The following method is disclosed as an example of its manufacturing method: An aqueous dispersion of carbon fibers having a length longer than the thickness of the current collector is prepared, and
This is filtered through a filter made of stainless steel wire mesh with a mesh size of approximately 150, and the carbon fibers are deposited on the filter to form a mat of carbon fibers. If the filtration speed is increased using a vacuum pump during this filtration, the carbon fibers deposited in a mat on the filter will be aligned in the direction of filtration. This mat of carbon fibers is impregnated with a binder such as phenolic resin, and then the gas flow path is formed by heat pressing, followed by firing to carbonize the binder.

However, this method tends to result in uneven mat-like carbon fibers, making it extremely difficult to produce electrode plates with uniform physical properties. This is a serious problem, especially when producing large substrates. Furthermore, electrode plates with this structure have low strength at the boundary between the thick and thin portions, making them prone to breakage.

As a method for producing a ribbed porous carbon material, 20 to 50 wt.%
One known method involves feeding a dry mixture of a thermosetting resin (a) and 80-50% by weight of carbon fiber into a mold that mirrors the rib shape of the desired substrate in a predetermined amount to obtain the desired porosity, press-molding the mixture into shape, and then sintering the mixture (U.S. Pat. No. 4,165,349). Another known method for producing a fuel cell electrode substrate with a high porosity and a narrow pore size distribution involves mixing carbon fiber, a binder, and an organic granular material, pressure-molding the mixture using a press or roll, and then sintering the mixture (Japanese Patent Laid-Open Publication No. 117649/1983). However, these methods are prone to uneven supply of raw materials to the mold or roll, resulting in non-uniform physical properties in the resulting substrate.

Furthermore, a method for producing an electrode substrate having uniform physical properties is known in which a raw material mixture consisting of short carbon fibers, phenolic resin and a molding aid is extruded, pressure-molded by rolling or stamping, and then sintered (Japanese Patent Laid-Open Publication No. 21753/1988).

However, even the porous carbon materials produced by such methods do not fully satisfy the requirements in the field of fuel cells in terms of physical properties such as electrical resistance, thermal conductivity, and strength, and further improvements are desired.

Ribbed porous electrode substrates for fuel cells are required to have high electrical and thermal conductivity, particularly in the thickness direction of the substrate, and to be thin in order to increase the power generation capacity per unit volume of the cell and reduce power generation costs.Even if they are thin, they must have sufficient strength to withstand damage during handling when assembling the cell stack or manufacturing the substrate.

An object of the present invention is to provide a method for producing a strong, flat, ribbed porous carbon material.

Another object of the present invention is to provide a method for producing a ribbed porous carbon material having high electrical and thermal conductivity in the thickness direction.

Another object of the present invention is to provide a method for producing a ribbed porous carbon material having extremely uniform physical properties.

DISCLOSURE OF THE INVENTION The ribbed porous carbon material according to the present invention contains carbon fibers and has a rib portion and a web portion, and in the web portion the carbon fibers are oriented in the plane direction of the web portion and perpendicular to the rib portion.

Here, the orientation direction of carbon fibers does not refer to the orientation direction of a single carbon fiber, but rather to the average orientation direction of carbon fibers in the porous carbon material, more specifically, in the rib or web portion. Taking the example of orientation perpendicular to the rib in a two-dimensional plane, this average orientation direction means that, assuming the direction perpendicular to the rib is 90 degrees, the number of carbon fibers oriented in any direction between 45 degrees and 135 degrees per unit area is greater than the number of carbon fibers oriented in any other direction.

The web portion refers to a flat portion located at the bottom of the rib portion and connecting the rib portions to each other, and the carbon fibers being oriented perpendicular to the rib portion means that the carbon fibers are oriented in the direction in which the rib portion extends, in other words, perpendicular to the longitudinal direction of the rib portion.

In the ribbed porous carbon material of the present invention, the carbon fibers in the web portion are oriented in the plane direction of the web portion and perpendicular to the ribs. A porous carbon material with this structure has a high overall strength and good handleability due to the synergistic effect of the reinforcing effect against bending in a direction parallel to the ribs, which is due to the fiber orientation in the web portion, and the reinforcing effect against bending in a direction perpendicular to the ribs, which is due to the beam action of the ribs.

In the ribbed porous carbon material of the present invention, the ribs do not need to be continuous from one end of the web to the other end, and the same effect can be achieved even if they are discontinuous in places.

In the ribbed porous carbon material of the present invention, the carbon fibers are oriented in the rib portion in the thickness direction of the web portion. In a porous carbon material containing carbon fibers, the electrical and thermal conductivities in the direction of the carbon fiber orientation are greater than those in other directions, so in a ribbed porous carbon material having such a structure, the electrical and thermal conductivities in the thickness direction of the porous carbon material as a whole are improved by the orientation of the carbon fibers in the thickness direction in the rib portion.

The degree of orientation of carbon fibers in a porous carbon material containing carbon fibers can be expressed by the ratio of electrical resistance and strength measured in different directions of the porous carbon material.

When the electrical resistivity of the flat ribbed porous carbon material of the present invention is measured on the web portion from which the ribs have been scraped off, the ratio of the electrical resistivity ρ _WP measured in the direction parallel to the extending direction of the ribs within the plane of the web portion to the electrical resistivity ρ _WT measured in the direction perpendicular to the extending direction of the ribs is ρ _WP /ρ
_WT is a value greater than 1.0. The ratio ρ _WP /ρ _WT is defined as the in-plane anisotropy ratio of electrical resistivity.

The ribbed porous carbon material of the present invention is bent in a direction parallel to the rib portion, and the bending strength of the web portion is measured as F _SP
The web part with the rib part removed is bent perpendicular to the rib part and the bending strength of the web part is F.
If F _SP /F _ST , the value of F SP /F _ST is greater than 1.0.
F _SP /F _ST is defined as the anisotropic ratio of bending strength. If the anisotropic ratio of bending strength becomes too large, the resistance to bending in a direction perpendicular to the ribs of the ribbed porous carbon material may become smaller than the resistance to bending in a direction parallel to the ribs.
The anisotropic ratio of bending strength is preferably not more than 10. In order to fully utilize the reinforcing effect due to the orientation of the carbon fibers, the anisotropic ratio of bending strength is preferably not less than 1.2, and more preferably not less than 1.5.

If the area of the web portion of the ribbed porous carbon material of the present invention is S _W , its thickness is t _W , the electrical resistance and electrical resistivity in the thickness direction are R _W and ρ _W , respectively, the total projected area of the ribs onto the web portion is Sr, the height of the ribs is tr, and the electrical resistivity in the height direction of the ribs is ρ r, then the electrical resistance R in the thickness direction of the entire ribbed porous carbon material can be expressed as a model by the following: R = ρ _W t _W /S _W + ρ r tr/Sr From this formula, is obtained.

The measured electrical resistance and electrical specific resistance in the thickness direction of the web portion obtained by scraping off the rib portion of the ribbed porous carbon material are defined as R _W and ρ _W , respectively, and the measured electrical resistance in the thickness direction of the entire ribbed porous carbon material is defined as R. The value γ calculated on the right side of the above equation is defined as the electrical resistance ratio between the web portion and the rib portion. In the ribbed porous carbon material of the present invention, the electrical resistance ratio γ between the web portion and the rib portion is 1.0 or more.

This indicates that the carbon fibers are more oriented in the thickness direction in the rib portion than in the web portion.

The higher the electrical resistance ratio γ between the web and rib sections, the better, but the manufacturing method described below can reduce this value to 1.
It is possible to easily manufacture a web having a specific electrical resistance _ρW in the thickness direction of the web portion of 40 mΩ.cm or less.

In the ribbed porous carbon material of the present invention, the ribs and web are integrally molded, which further improves the mechanical strength and electrical and thermal conductivity.

The method for producing a ribbed porous carbon material of the present invention comprises extruding a molding raw material containing carbonaceous fibers and a binder into a flat plate, forming ribs on the extrudate in a direction perpendicular to the extrusion direction, and then firing the extrudate.

More specifically, in the manufacturing method of the present invention, a molding material containing carbonaceous fibers and a binder is first extruded from an extruder to produce a uniform, flat extrudate. At this time, the carbonaceous fibers are predominantly oriented in the extrusion direction. The flat extrudate is then fed, for example, into a roll or die equipped with multiple parallel grooves for rib formation, and pressurized to form ribs perpendicular to the extrusion direction (the fiber orientation direction). That is, the die or roll grooves are positioned perpendicular to the extrusion direction of the extrudate, and pressure is applied to force portions of the extrudate into the die or roll grooves to form ribs. In this case, the carbon fibers in the extrudate are oriented in the extrusion direction and positioned perpendicular to the grooves. Therefore, when the molding material near the surface of the extrudate flows into the grooves, the longitudinal displacement of the carbon fibers varies depending on their position in the extrudate's thickness direction (the displacement is greater closer to the center of the groove). As a result, the carbon fibers in the portions that flow into the grooves (the rib portions) are oriented in the thickness direction of the extrudate. However, when ribs are formed in a direction parallel to the extrusion direction, the carbon fibers in the extrudate are parallel to the grooves in the die or roll, so there is no difference in the displacement of the extrudate in the thickness direction depending on the longitudinal position of the carbon fibers as described above (there is no difference in the displacement of the extrudate in the longitudinal direction of the grooves, i.e., the longitudinal direction of the carbon fibers). Therefore, in this case, the carbon fibers in the rib portion remain perpendicular to the thickness direction of the extrudate, and are hardly oriented in the thickness direction.

In this way, a flat ribbed molded body is produced, in which the fibers in the rib portion are oriented in the thickness direction of the web portion and in the web portion are oriented in the planar direction and perpendicular to the rib portion. This ribbed molded body is then fired in an inert atmosphere to form a ribbed porous carbon material. The firing process turns the carbonaceous fibers into carbon fibers, which are bonded to each other by carbon generated from the binder, etc.

Furthermore, in the manufacturing method of the present invention, an extrudate of uniform thickness is obtained by extrusion, and then this is fed into a roll or a mold to form the ribs. This reduces unevenness in the mixing of raw materials and in the supply of raw materials to a mold or the like, and the resulting ribbed porous carbon material has extremely uniform physical properties.

The carbonaceous fiber-containing molding raw material in the manufacturing method of the present invention is composed of the following substances.

The raw material does not necessarily need to contain all of the above substances. Of the above substances, the carbonaceous fibers and binders are essential, but the fluidity-imparting agents, solid particles, and pore-modifying agents are used in appropriate combinations.

Carbonaceous fibers are carbon fibers or fibers that can be converted into carbon fibers by calcination, such as pitch fibers, polyacrylonitrile fibers, rayon fibers, etc., that have been infusible, or that have been further heat-treated in an inert atmosphere.
Carbon fibers obtained by heat treatment at 0°C or higher are preferred because they are less likely to be damaged during extrusion.

The carbonaceous fibers have an average fiber length of 0.05 to 3 mm and an aspect ratio (L
Short fibers with an aspect ratio (L/D) of 5 or more are preferred. An average fiber length exceeding 3 mm reduces the fluidity of the molding raw material during processing, making extrusion and rib formation difficult. Furthermore, the fibers tend to entangle with each other during the molding process, forming fuzz balls. This prevents the fibers from being uniformly dispersed throughout the molded body, resulting in a non-uniform porous carbon material. An average fiber length of 0.05 mm or less is also undesirable, as the strength of the resulting molded body may be insufficient. To ensure sufficient fiber orientation during extrusion and rib formation and to exert a reinforcing effect, the carbonaceous fibers preferably have an average fiber length of 0.05 mm or more and an aspect ratio (L/D) of 5 or more. A more preferred range is an average fiber length of 0.1 to 2 mm and an aspect ratio (L/D) of 10 or more. The blending amount is preferably 3 to 50% by weight of the total molding raw material.
The method for measuring the fiber length and fiber diameter will be described later.

The binder used in the present invention maintains the shape of the molded body before and during firing, and carbonizes after firing to bond the carbon fibers together.
It is preferable that the resin has a viscosity of at least about 1000 MPa, melts and flows during extrusion and rib formation, and can be prevented from melting during firing of the molded body by simple treatment such as heating or oxidation. For example, thermosetting resins such as phenol resin and furfuryl alcohol resin are preferable.
Examples include petroleum pitch, coal pitch, and mixtures of two or more of these. In particular, phenolic resin alone or in a mixture with pitch is a preferred binder because it has a high carbonization rate and is easily hardened by heating.

The fluidity-imparting agent used in the present invention melts and flows at the temperature (molding temperature) at which the binder used melts and flows, and imparts the fluidity necessary for the operations of kneading, extrusion, and rib formation to the molding material.
6) A thermoplastic resin having a melt flow rate of 30 to 500 g/10 min is used, such as ethylene-vinyl acetate copolymer resin, low molecular weight polyethylene, low molecular weight polypropylene,
Examples include coumarone resin and petroleum resin.

Furthermore, adding 1 to 5 parts by weight of a lubricant such as stearic acid to 100 parts by weight of the molding raw material is effective in facilitating kneading and extrusion.

Furthermore, the effects of the present invention can be further improved by adding particles having a particle size of 5 to 50 μm that are solid when molded to the molding material.

When a molding raw material containing such solid particles is used, the solid particles prevent the binder and/or fluidity enhancer from slipping through the gaps between the carbon fibers when the molding raw material flows, thereby allowing the molding raw material to flow as a whole. This is particularly effective when forming ribs using a mold or roll. That is, when such solid particles are included, the molding raw material flows into the parts of the mold (or roll) corresponding to the ribs as a whole. Therefore, the composition of the raw material becomes uniform in the ribs of the molded body, and the carbon fibers in the ribs are more oriented in the thickness direction of the molded body, more specifically, the web portion. On the other hand, when solid particles are not added, the binder and/or fluidity enhancer tend to flow more into the parts of the mold (or roll) corresponding to the ribs, resulting in a non-uniform raw material composition in the ribs. Furthermore, the degree of orientation of the carbon fibers in the ribs in the thickness direction of the web portion is lower than when solid particles are added. The solid particles promote fiber orientation during molding and improve the electrical and thermal conductivity of the resulting porous carbon material.

Carbonaceous particles are preferred as such solid particles. The carbonaceous particles remain as carbon even after firing of the compact and become a component of the ribbed porous carbon material, so they do not adversely affect the use of the ribbed porous carbon material. Coke and/or graphite particles, which have high electrical and thermal conductivity after firing, are particularly preferred. The average particle size of the carbonaceous particles is preferably 5 to 50 μm, more preferably 10 to 30 μm. An average particle size exceeding 50 μm is undesirable because it reduces the ability to fluidize the molding raw material as a whole and only produces a porous carbon material with low mechanical strength. Furthermore, an average particle size of 5 μm or less reduces the fluidity of the molding raw material during kneading and extrusion, making handling difficult. The amount of carbonaceous particles blended is preferably 5 to 40% by weight of the total amount of molding raw material, more preferably 10 to 30% by weight.

Furthermore, by adding a pore control material to the raw material for forming, it is possible to easily control the pore size of the resulting porous carbon material. The pore control material has the function of volatilizing or decomposing into gas during firing and then forming pores.
As the pore control material, a granular organic polymeric material that does not melt and flow even if it deforms slightly during the operations of kneading, extrusion, and rib formation is preferred, as it makes it easy to control the pores. Examples include high-density polyethylene, polymethyl methacrylate, polypropylene, polyvinyl alcohol, polystyrene, and starch. By appropriately setting the amount and particle size of the pore control material, the porosity and pore size of the porous carbon material can be controlled. In order to achieve efficient pore formation, the carbonization rate of the pore control material (the residual carbon rate after firing) should be
Preferably, it is 10% or less. A suitable pore adjusting material is high density polyethylene-polymethyl methacrylate.

An example of the blend of the above raw materials for producing a ribbed porous carbon material that is easy to operate and has well-balanced properties as a gas diffusion electrode for a fuel cell is as follows:
40% by weight, binder 20-50% by weight, fluidity improving material 0-30% by weight, carbonaceous particles 0-40% by weight, pore-forming material 0-35% by weight, and more preferably, the range is 5-30% by weight, carbonaceous fiber 25-40% by weight, binder 5-25% by weight, carbonaceous particles 10-30% by weight, pore-forming material 20-30% by weight.

The raw material components are mixed and then kneaded. Although the kneading can be performed using a molding extruder that serves both the kneading and molding functions, it is preferable to use a kneader to uniformly knead the raw material components, then form pellets, and feed these to the extruder, in order to reduce unevenness in the supply of the raw materials and produce a more uniform porous carbon material.

The raw materials for molding are kneaded and then extruded. In extrusion molding, the material is extruded into a flat plate using a flat die. When using a thermosetting resin as a binder, if the temperature during kneading or extrusion is too high or the time is too long, the binder hardens, reducing the fluidity of the raw material mixture and making these operations impossible. To avoid this situation, for example, when using phenolic resin as a binder, it is recommended to use a material with a melting point of 90
The resin to be used must be below 150°C, with a gelling time of 1 minute/150°C or above, and the kneading and extrusion must be carried out at 110°C or below for 10 minutes or less.

The rib formation is preferably carried out by pre-curing the extruded molded product at 130 to 170°C for 1 to 10 minutes using rolls or dies designed to form the desired rib in a direction perpendicular to the extrusion direction, and then holding the product at a temperature of 140 to 170°C and a pressure of 20 to 60 kg/ ^cm2 for 0.5 to 5 minutes.

The molded article obtained as described above is heated to 800°C in an inert atmosphere, i.e., in an inert gas such as nitrogen or argon, or under reduced pressure.
The molded body is then fired at a temperature of 150 to 500°C to produce a porous carbon material. It is preferable to sandwich the molded body between graphite plates during firing to prevent deformation. It is preferable to perform post-curing at a temperature of 150 to 500°C prior to firing, as this helps the molded body to maintain its shape well during firing.

In the ribbed porous carbon material of the present invention, the carbon fibers in the web portion are oriented in the plane direction of the web portion and perpendicular to the ribs, so that the reinforcing effect against bending in a direction parallel to the ribs due to the orientation of the carbon fibers in the web portion and the reinforcing effect against bending in a direction perpendicular to the ribs due to the beam action of the ribs combine to produce a ribbed porous carbon material with high overall strength and good handleability. Furthermore, the orientation of the carbon fibers in the thickness direction of the ribs improves the electrical and thermal conductivity of the porous carbon material in the thickness direction.

Furthermore, according to the present invention, a molding raw material containing carbonaceous fibers is extruded through an extruder to produce a flat plate (extrudate) of uniform thickness in which the carbonaceous fibers are oriented in the extrusion direction, and then this flat plate is fed into a roll or mold having numerous parallel grooves for forming ribs and pressed to form ribs in a direction perpendicular to the extrusion direction (the direction of fiber orientation). This easily produces a flat, ribbed molded article having a structure in which the fibers in the rib portions are oriented in the thickness direction of the web portion and in the web portion are oriented in the plane of the web portion and perpendicular to the rib portions. By firing this ribbed molded article in an inert atmosphere, it is possible to produce a ribbed porous carbon material with high strength and high electrical and thermal conductivity in the thickness direction, using an extremely highly productive method that combines extrusion with rolls or presses.

Furthermore, by adding carbonaceous particles to the molding material, it is possible to further promote the orientation of the fibers and further increase the electrical and thermal conductivity in the thickness direction.

As a result, an electrode substrate for a fuel cell with excellent properties can be easily manufactured.

The following examples are provided to illustrate, but the present invention is not limited to, the examples provided as long as they fall within the scope of the claims of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a preferred embodiment of a flat ribbed porous carbon material according to the present invention; FIG. 2 is a perspective view of the flat ribbed porous carbon material shown in FIG.
- An explanatory diagram showing the orientation of fibers in a cross section taken along line II;
FIG. 3 is an explanatory diagram schematically showing the orientation of fibers in the cross section taken along line III-III shown in FIG.

EXAMPLES Before explaining the examples, the measurement method will be clarified.

[Measurement method]

1) Fiber diameter of carbonaceous fibers Measured using a microscopic microscope.

2) Fiber length of carbonaceous fiber: The fiber length was measured on a micrograph (magnification known) of the carbonaceous fiber and corrected for the magnification.

3) Particle size of carbonaceous particles and pore-controlling materials Measured using a centrifugal sedimentation particle size distribution analyzer.

4) Melting point of phenolic resin Complies with JIS K 6910.

5) Gel time of phenolic resin Complies with JIS K 6910.

6) Carbonization rate of binder and pore adjuster Complies with JIS M 8812.

7) Melt flow rate of thermoplastic resin, based on JIS K 7210. 8) Bending strength of ribbed porous carbon material 1, F _SP , based on JIS K 6911. The porous carbon material 1 as a sample was bent parallel to the rib portion 2 shown in the figure, and the thickness of the sample when calculating the strength did not include the rib portion 2.

9) Bending strength of the web portion 3 of the ribbed porous carbon material 1 (direction perpendicular to the rib portion 2): _FST The rib portion 2 of the ribbed porous carbon material 1 is removed by cutting to obtain a flat plate-shaped sample consisting only of the web portion 3. This sample is folded in a direction perpendicular to the existing rib portion 2, and the bending strength is measured in accordance with JIS K 6911.

10) Fill the grooves 4 of the ribbed porous carbon material 1 shown in the electrical resistivity diagram of the ribbed porous carbon material 1 with gypsum so that the height is equal to the height of the rib portions 2, and place the ribbed porous carbon material 1 between two mercury electrodes from above and below in FIG.
A DC voltage E (mV) is applied between the mercury electrodes, and the current I (A) that flows at that time is measured. The thickness of the ribbed porous carbon material 1 including the rib portion 2 is defined as t (cm), and the contact area of the rib portion 2 with the mercury electrode is defined as S ( ^cm2 ), and the electrical resistivity is calculated using the following formula.

11) Electrical resistance in the thickness direction of the ribbed porous carbon material 1; R: Determined in the same manner as in 10) using the following formula.

12) Electrical resistivity of the web portion 3 of the ribbed porous carbon material 1: ρ _W , ρ _WT , ρ _WP A flat plate-shaped sample consisting of only the web portion 3 is obtained in the same manner as in 9). The electrical resistivity of this sample is measured.

The electrical resistivity through the thickness was measured without using gypsum.
The temperature is measured in the same manner as above (ρ _W ).

The electrical resistivity in the plane direction is measured in accordance with JIS R 7202 (ρ _WT , ρ _WP ).

13) Thermal conductivity of the ribbed porous carbon material 1 The ribbed porous carbon material 1 is sandwiched between copper plates, a temperature gradient is applied, and a constant amount of heat flows in a steady state (Q; kcal
/h).

The temperature difference ΔT between both sides of the ribbed porous carbon material 1 at that time
(°C) is measured.
The contact area of the surface not having the rib (one surface of the web portion 3) with the copper plate is S (m ² ), and the thickness of the porous carbon material 1 including the rib portion 2 is t (m), and the thermal conductivity is calculated using the following formula.

14) Gas permeability of ribbed porous carbon material 1 A cup of 80 mm diameter (gas passage area S; cm ² ) was placed on one side of the web portion 3 not having the rib portion 2, and a constant flow rate V (ml/
h) Air is passed through the sample, and the pressure difference ΔP
(mmAq) and calculate the gas permeability using the following formula:

Example 1: Short carbon fibers made from petroleum pitch and fired at 900°C as carbonaceous fibers: average diameter 14 μm, average fiber length 0.4 mm
0% by weight, coal pitch coke as carbonaceous particles: average particle size 20 μm
20% by weight, Novolac type powdered phenolic resin as binder: melting point 81
° C., gelation time 1.2 minutes/150 ° C., carbonization rate 54% by weight, 35% by weight, ethylene-vinyl acetate copolymer resin as fluidity imparting material:
Vinyl acetate content 19% by weight, melt flow rate 150g/1
100 parts by weight of raw materials consisting of 12% by weight of polyethylene resin as pore modifier: melting point 120°C, average particle size 80 μm, 8% by weight of polyethylene resin as pore modifier: softening point 170°C, average particle size 80 μm, 15% by weight of polymethyl methacrylate resin as pore modifier: softening point 170°C, average particle size 80 μm, to which 2 parts by weight of stearic acid was added, were uniformly mixed in a blade mixer, and then kneaded in an extruder-type kneader at a temperature of 100°C for a residence time of 5 minutes, and extruded to produce cylindrical pellets with a diameter of 3 mm. The pellets were then extruded into a 90 mm diameter extruder equipped with a coat hanger die.
The mixture was fed into an extruder with a screw length/diameter ratio (L/D) of 24 mm.
A plate having a thickness of 1.3 mm and a width of 650 mm was extruded at 40 kg/h at a temperature of 100°C. The temperature in the kneading zone was 110°C, and the residence time was 6 minutes. The extruded plate was then cut at 650 mm intervals and cut into 145 to 16 pieces.
After pre-hardening for 3 to 5 minutes in a pre-hardening oven maintained at 0°C, the upper mold is flat and the lower mold is 1.2m deep.
m, and a rectangular cross-section groove with a width of 1.0 mm, with the distance between the centers of the grooves being 2.0 m
The pre-cured plate was fed into a mold maintained at a temperature of 160°C, with the grooves of the mold, more specifically the direction of extension of the grooves of the mold, perpendicular to the extrusion direction of the plate, and pressed at a pressure of 50 kg/ ^cm2 for 3 minutes to form the rib portion 2. The molded body was removed from the mold and heated in a nitrogen atmosphere from 150°C to 500°C over 10 hours, whereupon it was pre-cured and pre-fired. The pre-fired plates were sandwiched between 10 mm thick black smoke plates at a ratio of one plate per 20 plates, and then heated to 2000°C in a vacuum furnace over 30 hours to produce the first rib.
A ribbed porous carbon material 1 as shown in the figure was produced.

Comparative Example 1 A ribbed porous carbon material was produced in the same manner as in Example, except that the ribs were formed parallel to the extrusion direction of the flat plate.

Example 2: Carbonaceous fibers (average diameter 12.5 μm, average fiber length 1 mm) made by oxidizing and infusibilizing petroleum pitch yarn and then calcining at 600° C. 38% by weight: Phenol resin used in Example 1 25% by weight: Ethylene-vinyl acetate copolymer resin used in Example 1
37% by weight of stearic acid per 100 parts by weight of the molding raw material
The mixture to which 10 parts by weight had been added was treated in the same manner as in Example 1 to produce a flat ribbed porous carbon material 1.

Comparative Example 2 A flat ribless porous carbon material was produced in the same manner as in Example 2, except that both the upper and lower dies were flat. Ribs were formed on the flat ribless porous carbon material by cutting in parallel to the extrusion direction so as to have the same dimensions as the flat ribbed porous carbon material 1 of Example 2, thereby producing a ribbed porous carbon material.

The properties obtained for each of the ribbed porous carbon materials are shown in Table 1.

As is clear from these, the ribbed porous carbon material 1 of the present invention, as shown schematically in Figs. 1 to 3, has the following characteristics:
In the rib portion 2, the carbon fibers 5 are oriented in direction A, which is the thickness direction of the web portion 3, and in the web portion 3, they are oriented in direction B, which is the surface direction of the web portion 3 and perpendicular to the rib portion 2.

Claims (3)

[Claims] [Claim 1] A method for producing a ribbed porous carbon material, which comprises extruding a molding raw material containing carbonaceous fibers and a binder into a flat plate, forming ribs on the extrudate in a direction perpendicular to the extrusion direction, and then firing the extrudate. 2. The method for producing a ribbed porous carbon material according to claim 1, wherein the ribs are formed on the extrudate by roll or press molding. 3. The method for producing a ribbed porous carbon material according to claim 1, wherein the raw material for molding further contains carbonaceous particles having a particle size of 5 to 50 μm.