JPH06263559A - Production of porous carbon plate - Google Patents

Abstract

PURPOSE:To obtain a porous carbon plate having physical properties excellent in homogeneity in a remarkably shortened forming time by pressurizing a powdery material containing a thermosetting resin, a curing agent and carbon fiber, then depressurizing the material, thermosetting the material and subsequently burning the thermoset material. CONSTITUTION:A powdery material for forming a porous carbon plate containing (A) a powdery thermosetting resin, (B) a powdery curing agent and (C) powdery carbon fiber is press formed, then depressurized, subsequently thermoset and subsequently burned to produce a porous carbon plate. The components (A) and (B) are preferably powder having <=150mum particle diameter. The fiber of the component (C) is preferably carbon fiber having <=20 aspect ratio (L/D). A method for press forming the powdery material under 5-50kg/cm<2>, providing a flat plate, then depressurizing the plate, thermosetting the formed plate at 100-200 deg.C and subsequently burning the plate is preferred. Thereby, the porous carbon plate of stabilized quality is obtained at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous carbon plate, and the obtained porous carbon plate is used for an electrode material such as a phosphoric acid fuel cell, a heat resistant material and a corrosion resistant filter.

[0002]

2. Description of the Related Art Among various fuel cells attracting attention as an energy-saving and pollution-free next-generation power generation system, a phosphoric acid fuel cell using phosphoric acid as an electrolyte is most practically used as a first generation fuel cell. The development is being advanced to the stage of conducting a verification test. In a phosphoric acid fuel cell, the cell body is composed of a stack of electrode plates, a separator, a cooling plate, etc., and most of them use carbon materials. In addition to having high mechanical strength and excellent handleability, this is an electrolyte (phosphoric acid) at a reaction temperature of about 200 ° C.
It is characterized by excellent durability against heat, excellent thermal conductivity, and excellent porosity (for electrode plates) and gas impermeability (for separators). Because the carbon material also has.

The inner carbon electrode plate is porous in order to retain phosphoric acid and to permeate gas, is excellent in heat conduction and electric conduction in the thickness direction, and is easy to handle. It is necessary to have strength, and a porous carbon plate having these properties is used.

Conventionally, as a method for producing a porous carbon plate, a method in which a fibrous substance is used as a main material, and this is molded and cured into a plate shape with a binder such as a resin, and then baked, is generally used. As the fibrous substance, organic fibers such as pulp, polyacrylonitrile, and phenol resin, or carbon fibers such as carbonaceous fibers and graphite fibers are used alone or in combination. When using organic fibers, in order to prevent shrinkage of the material in the firing process, some infusibilizing treatment such as forming an oxide film on the fiber surface is performed, or composite with carbon fiber that does not shrink in the firing process Measures such as to be taken. As the carbon fiber, a general-purpose carbon fiber from an optically isotropic pitch, a high-performance carbon fiber from an optically anisotropic pitch, or a carbon fiber starting from an organic fiber such as polyacrylonitrile or rayon is used. .

In addition to the above, a so-called powder method has been conventionally used as a method for producing a porous carbon plate having a thickness of 1 mm or more. This powder method uses carbon fiber as the starting material,
After mixing powder such as graphite and a powdery binder and filling the mold, the temperature is applied by a hot press and the pressure is applied,
This is a method in which after sufficient heat curing is carried out, it is taken out from the press, after cooling it is released from the mold to obtain a molded plate, and then baked.

[0006]

A problem in the production of a porous carbon plate by a powder method using a powdery substance is that a so-called pressing die capable of withstanding high temperatures and high pressures is required. The step of forming the material into a formed plate of a predetermined shape still requires a long time using such a press, and the obtained porous carbon plate often has an uneven portion in terms of density and the like. These problems are major problems in terms of manufacturing cost and quality stabilization when the powder method is used in manufacturing a porous carbon plate.

[0007]

Means for Solving the Problems As a result of intensive studies to solve these problems, the inventors of the present invention firstly pressurize these powder materials once, then depressurize them, and then heat-cure them before firing. More preferably, the powdery thermosetting resin and the powdery curing agent used in the above method have a particle size of 150 μm or less and the carbon fiber has an aspect ratio (L / D) of 20 or less. By
The present invention has been completed by solving the problems of the conventional powder method and finding that a porous carbon plate of low cost and stable quality can be obtained.

That is, according to the present invention, a powder material for forming a porous carbon plate containing a powdery thermosetting resin, a powdery hardening material and a powdery carbon fiber is pressure-molded, depressurized and then heat-cured. The present invention provides a method for producing a porous carbon plate, which comprises firing and then firing.

The powdery thermosetting resin used in the present invention is preferably one which can be prepared to have a particle size of 150 μm or less and has a high residual carbon rate. Specific examples include epoxy resin, phenol resin, unsaturated polyester resin, furan resin,
Examples thereof include thermosetting resins such as polyimide resin and pitches, and among them, phenol resin and pitches are preferable from the viewpoint of high residual carbon rate.

Further, the powdery curing agent accelerates curing of the thermosetting resin, and preferably has a particle size of 150 μm.
What can be prepared below is preferable. Specific examples include hexamine and methylmelamine. Thermosetting resin,
In the case of any of the curing agents, if the powder size is larger than 150 μm, the required homogeneity cannot be obtained in the mixture of these resins and carbon fibers, and in the case of the curing agent, the homogeneity is present alone and remains It often causes a non-uniform portion such as a pinhole in the porous carbon plate.

The carbon fiber used in the present invention preferably has an aspect ratio (L / D) of 20 or less,
The starting material, manufacturing method, etc. are not particularly limited. In general, it is preferable to use pitch-based carbon fiber because it has a high carbonization yield and is easy to manufacture with a low aspect ratio. If the aspect ratio exceeds 20, it tends to be difficult to uniformly disperse the powdery resin or the like. The amount ratio of the carbon fiber to the thermosetting resin and the curing agent may be set so as to satisfy the desired physical properties such as bulk density, strength, thermal conductivity and electric resistance, and is not particularly limited. Specifically, carbon fiber / (thermosetting resin + curing agent) is often used in the range of 20/80 to 50/50.

As a method for molding the powder material in the present invention, it is essential to press once, depressurize, and then heat and heat cure to obtain a molded plate. Here, the method of pressurization is not particularly limited to the type of device as long as the required pressure can be applied. Specifically, press or pressure roll
Lar or the like is used. The pressure to be applied is not particularly limited as long as it is a pressure capable of uniformly powder-forming the powder material, but a range of 5 to 50 kg / cm ² is preferable in terms of quality and cost. In the present invention, it is essential to apply the above pressure, depressurize, and then heat cure by heating. However, after depressurizing, without using a press,
It is possible to place a weight in the range of 0.1 kg / cm ² or less on the molding plate. It suffices that the temperature and time required for heat curing be secured for heating, and there is no particular limitation on the heating method and device. Specifically, a batch type or continuous type dryer, a multi-stage dryer or the like is used. Regarding the temperature, it is sufficient that heat curing can be achieved, and the range of 100 to 200 ° C. is preferably used.

According to the production method of the present invention, it is not necessary to heat while applying high pressure with a press or the like, and the product obtained by pressure molding in a short time is continuously subjected to a multi-stage batch dryer or a continuous dryer. It is possible to heat-set in large quantities or continuously.

The shaped plate obtained as described above is fired at a temperature of 800 ° C. or higher in a vacuum or an inert gas atmosphere to obtain a porous carbon plate.

As a method for producing a grooved porous carbon plate, if a flat porous carbon plate is prepared in advance and then grooves are formed by cutting or the like, the yield is not good. In some cases, a method of producing a molding die (having a groove) and heating it with a press or the like while applying pressure for a long time to obtain a molded plate before firing is adopted. However, in addition to the durability performance against high temperature and high pressure, precision is required at the time of making the mold, so that there is a drawback that the cost becomes considerably high. In the method of the present invention, pressure molding is performed in a short time, and after depressurization, heat curing is performed by heating to obtain a molded plate before firing. Therefore, the grooved mold may be one that can withstand pressure for a short time. Yes The cost reduction effect in the production of porous carbon plates is extremely large. The firing step does not require a grooved carbon plate as a spacer, and the desired porous carbon plate can be produced by sandwiching between the grooveless carbon plates and firing.

[0016]

EXAMPLES Next, the present invention will be further described with reference to examples. In the examples,% is based on weight unless otherwise specified.

Example 1 As a powdery thermosetting resin, a novolac phenol resin (Ceradic 4331S manufactured by Dainippon Ink and Chemicals Co., Ltd.) pulverized to a particle size of 150 μm or less was pulverized to 35%, similarly, a particle size of 150 μm or less. Prepared hexamine (Sumitomo Chemical Co., Ltd.) 2%, aspect ratio (L / D) is 1
2 (156 μm / 13 μm) pitch-based carbon fiber (Donakabo S made by Donac Co., Ltd.) 63% of homogeneously mixed powder material containing 63% was filled in a mold having an area of 2500 cm ² and then a thickness of 1.8 mm was obtained. Until about 2 by press
Pressure molding was performed for 0.5 minutes at a pressure of 0 kg / cm ² . This is depressurized and then about 15 in a multi-stage dryer at 160 ° C.
After heating for a minute, a molded plate was obtained. The time from setting in the press to removal as a molded plate was about 20 minutes. The formed plate was sandwiched between carbon plates in a vacuum firing furnace, heated to 2000 ° C. at 2 ° C./min in a vacuum atmosphere, and held for 30 minutes for firing. The obtained porous carbon plate was a homogeneous porous carbon plate having the physical properties shown in Table 1.

Example 2 As a powdery thermosetting resin, a phenol formaldehyde resin (Velpar S899 manufactured by Kanebo Co., Ltd.) prepared to have a particle size of 150 μm or less was pulverized to 30% and similarly to a particle size of 150 μm or less. Hexamine (Sumitomo Chemical Co., Ltd.) 0.5%, aspect ratio (L / D) 10 (130 μm)
(13 μm) pitch-based carbon fiber (Donakabo S manufactured by Donac Co., Ltd.) of 69.5% and homogeneously mixed powder material (485 g) is filled in a mold having an area of 2500 cm ^{2 to have} a thickness of 2.2 mm. Up to about 10 kg / c with a pressure roller
Pressure molding was performed at a pressure of m ² . The molded product was subsequently heated for about 5 minutes in a belt-conveying continuous dryer set at 180 ° C. to obtain a heat-cured molded plate. The time from setting the powder sample to taking it out as a molded plate was about 7 minutes. The formed plate was sandwiched between carbon plates and heated in a vacuum firing furnace at 2 ° C./min to 2000 ° C. in a vacuum atmosphere and held for 30 minutes for firing. The obtained porous carbon plate was a homogeneous porous carbon plate having the physical properties shown in Table 1.

Example 3 As in Example 1, 250 g of a homogeneously mixed powder material was used.
Groove width 1.5mm, groove height 0.8mm, groove spacing 1.5
Area with 2500 mm parallel grooves, area 2500 cm ²Mold
After filling in, press about 30 to a thickness of 1.5 mm
kg / cm²It pressure-molded at the pressure of 0.5 minutes. Then
This is depressurized and then in a multi-stage dryer at 160 ° C for about 15 minutes
A molded plate was obtained by heating. This formed plate is carbonized in a vacuum firing furnace.
Sandwiched between plates, up to 2000 ° C at 2 ° C / min in a vacuum atmosphere
The temperature was raised and held for 30 minutes for firing. The obtained porous charcoal
The base plate has excellent physical properties as shown in Table 1 that is uniform and has uniform groove formation.
It was a porous carbon plate.

Comparative Example 1 415 g of the powder material homogeneously mixed as in Example 1 was filled in a mold having an area of 2500 cm ² , set in a hot press, heated to 160 ° C., and about 20 kg until the thickness became 1.8 mm. Pressure molding was performed at a pressure of / cm ² . After maintaining the thickness at 160 ° C. for 15 minutes, it was cooled and released from the mold. This formed plate is sandwiched between carbon plates in a vacuum firing furnace and heated to 2000 ° C. at 2 ° C./minute in a vacuum atmosphere.
It was held for minutes and baked. The obtained porous carbon plate was a homogeneous porous carbon plate having the physical properties shown in Table 1. However, in this comparative example, it took about 2 hours from setting in the hot press to taking out the molded plate.

Comparative Example 2 In the same kind and amount ratio as in Example 1, the size of powder of thermosetting resin and curing agent is 300 to 400 μm, and the aspect ratio of pitch-based carbon fiber is 30 (390 μm / 13 μm).
A porous carbon plate was produced in the same manner as in Comparative Example 1 by using the m). Table 1 shows the physical properties of the obtained porous carbon plate. In the observation of the surface state, there were many irregularities, the bulk density and the gas permeability varied in physical properties, and the bending strength was reduced by about 20% as compared with Example 1. In addition, in this comparative example,
It took about 2 hours from setting in the hot press to taking out as a molded plate.

[0022]

[Table 1]

[0023]

As compared with the conventional method for producing a porous carbon plate by the powder method, the physical properties of the obtained porous carbon plate are excellent in homogeneity, and the molding time can be greatly shortened, so that the manufacturing cost is greatly reduced. Is possible.

Claims (4)

[Claims] 1. A porous carbon plate-forming powder material containing a powdery thermosetting resin, a powdery hardener and a powdery carbon fiber is pressure-molded, depressurized, and then heat-cured. A method for producing a porous carbon plate, which comprises firing. 2. The production method according to claim 1, wherein the powdery thermosetting resin and the powdery curable material are powders having a particle diameter of 150 μm or less. 3. The powdery carbon fiber has an aspect ratio (L /
D) The production method according to claim 1 or 2, wherein the carbon fiber is 20 or less. 4. A powder material for forming a porous carbon plate is used in an amount of 5 to 50.
The manufacturing method according to claim 1, 2 or 3, wherein after pressure-molding to kg / cm ² , a flat plate is formed, depressurization is performed, then heat curing is performed at 100 to 200 ° C., and then firing is performed.