JP2001106575A - Process for producing carbonaceous compound and graphite carbon composite formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process of a carbonaceous compound and a graphite carbon composite formed body which has very low gas permeability and is appropriately used as a solid polymer type fuel cell separator sheet having a complicated shape. SOLUTION: This production process involves: dry-blending the constituent particles of a fine particle component consisting essentially of carbonaceous compound particles each of which contains a self-sintering ingredient and has a <=10 μm average particle size, and fine graphite carbon particles each having a 10-70 μm average particle size; adding a binder aqueous solution to the blended fine particle component to obtain a mixture; granulating the mixture into dry granules having 0.5-20 mm granule size; subjecting the granules to press forming into a green body; and subjecting the green body to heat treatment in a non- oxidizing atmosphere to produce the objective graphite carbon composite formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention granulates and forms a mixture of carbonaceous compound fine particles exhibiting self-sintering properties when heated and at least one type of graphitic carbon fine particles selected from the group consisting of artificial graphite and natural graphite. And a method for producing a carbonaceous compound / graphitic carbon composite molded article obtained by heating.

The present invention is a particularly important elemental characteristic among physical characteristics such as bending strength, electric conductivity, thermal conductivity, gas permeability and the like required for a separator plate of a polymer electrolyte fuel cell. Provided is a method for producing a carbonaceous compound / graphitic carbon composite molded article characterized by extremely low gas permeability. According to the present invention, a formed shape having a complicated shape, which is found in a grooved separator plate of a fuel cell, is formed into a single piece by a press, and heat treatment is performed on the formed shape. The carbonaceous compound / graphitic carbon composite molded article of the above can be produced extremely efficiently on an industrial scale.

[0003]

2. Description of the Related Art Various methods for producing a composite material comprising a carbonaceous compound, a so-called pitch compound, and graphitic carbon have been proposed. The purpose of compounding a carbonaceous compound with graphitic carbon is various. It is mentioned that the characteristics of graphite can be imparted to the fired molded body by these combinations. In addition, the effect of supplementing the weakness of graphitic carbon with a carbonaceous compound (for example, in a phosphoric acid fuel cell, a molded body made of graphitic carbon alone has low strength, and a large amount of corrosion current flows under operating conditions. As a result, the molded product collapses, but the system in which the carbonaceous compound is dispersed in the vicinity of the graphitic carbon is 1000-1000.
In a system in which a carbonaceous compound is converted to carbonaceous carbon by being subjected to a heat treatment at 1500 ° C., the crystal end faces of the graphitic carbon grains are protected,
Has the effect of dramatically reducing corrosion current).

Further, it is known that a carbonaceous carbon / graphitic carbon composite molded article can have the same dimensions of a formed article / carbonized molded article by appropriately setting the abundance ratio of carbonaceous carbon / graphitic carbon. . Utilizing this characteristic, even if a complicated shape is given at the time of the formed body and firing is performed, no distortion or cracking occurs due to shrinkage, and a fired body having the same shape as the formed body can be obtained.

The present inventors have recently paid attention to the characteristics of carbonaceous carbon / graphitic carbon as power generators for automobiles and homes, and polymer electrolyte fuel cells which are being developed by automobile manufacturers and electric appliance manufacturers. Intensive investigations have been made to utilize it in the production of gas separator plates having a complicated shape used for manufacturing. We have already developed a number of new methods for producing carbonaceous carbon / graphitic carbon composite compacts.

[0006]

SUMMARY OF THE INVENTION The grooved carbonaceous carbon / graphitic carbon composite molded body obtained in the research conducted by the present inventors has been studied in detail in a later study. It became clear that there was a problem with the gas permeation amount, which is the lifeline of the plate. In the previous study, a 25 mm square test piece was cut out from a 200 mm square grooved carbonaceous carbon / graphitic carbon molded body obtained by carbonization at 1200 ° C.
The gas permeation amount was measured in a region of 5 mmφ under a nitrogen back pressure of 1 kg / cm ² to obtain a gas permeation amount suitable for the separator plate.

When a plate-shaped carbonized molded article of 200 mm square was manufactured and the gas permeation amount was measured, the gas permeation amount was extremely large, and it was found that the structure was not suitable for gas separator applications. In the case of a gas pressurized diameter of 15 mmΦ in a 25 mm square, gas leaks from the side surface of the carbonized molded body,
It was apparent that a small amount of gas permeation was observed. Further, when the pore distribution of the carbonized molded article was measured by a mercury intrusion method, it was found that pores having a radius of about 0.6 μm were selectively formed in any of the carbonized molded articles produced by the prior art. Was done. The fact that the granulated powder used as a raw material of the molded article did not completely collapse was generated from the observation of the cross section of the molded article by a scanning electron micrograph, which was also revealed.

[0008]

Means for Solving the Problems The present inventors have intensively studied the factors that deteriorate the gas permeability of a carbonaceous carbon / graphitic carbon composite molded article for use in polymer electrolyte fuel cells, and the following factors are complex. I found that they were acting in a way. (1) The size of the granulated powder is an important controlling factor. That is, in the previous study, the granulated powder particle diameter was set to 0.5 mm or less. However, when the particle diameter becomes smaller, even if a constant pressure is applied during press molding, the pressure applied to each particle becomes relatively small. For small particles, the molding pressure is dispersed in the intergranular space. As a result, it was found that since the shape of the formed body was formed without completely crushing the granulated powder, many inter-granules where gas permeation was easy were formed, and the gas permeation amount was increased.

Therefore, in order to secure an extremely low gas permeation amount, which is the object of the present invention, it is essential that the granules are easily crushed at the time of pressurization and no intergranular space is left. The present inventors have conducted intensive studies on the diameter of the granulated powder and the gas permeability = the presence or absence of unbroken particles in the formed product. As a result, the granulated powder diameter is 0.5 to 20 mm, preferably 1 to 10 mm,
More preferably, it has been found that the unbroken particles in the formed form are drastically reduced when distributed over 1 to 5 mm.

(2) It has been found that the compressive fracture strength of the granulated powder is also an important controlling factor. That is, when a large granulated powder satisfying the condition (1) has an extremely high compressive strength, it is hardly crushed even when a molding pressure is applied, and eventually voids between the particles remain to allow gas to escape from there. The amount will be increased. To reduce the compressive strength of the granules, it is necessary to solve two factors at the same time. When the granulating agent exerts a strong binding force inside the dried granules, the particles are less likely to be crushed. Specifically, this corresponds to the case where the granulating agent in a dry state exhibits a dense bonding state like a resin film.

Polyethylene glycol 4000, which was mentioned as a preferred granulating agent in the previous study, was dissolved in water, placed in a dish, and heated to 110 ° C. to form a film-like melt. Upon cooling to room temperature, a crack-free integral film like a resin film was formed. In view of the above characteristics of polyethylene glycol 4000, it can be easily inferred that the granulated body produced by using the polyethylene glycol 4000 does not exhibit easy disintegration and the gas permeability is increased.

In fact, previous studies have shown that polyethylene glycol 4
The gas permeability of the molded product granulated and molded at 000 was larger than that of sucrose. On the other hand, when the aqueous solution of sucrose used as a preferable granulating agent in the previous study was heated to 110 ° C, a beautiful molten film was formed at 110 ° C, but countless fine cracks were generated in the process of cooling to room temperature. The membrane easily disintegrated into fine pieces by simply pressing with a fingertip. That is, it was found that sucrose was an extremely preferable granulating agent in that it had appropriate characteristics as a granulating agent, but was able to maintain the particle strength at an appropriate stage at the stage of forming.

(3) As a result of further intensive studies, it has been found that the sucrose content in the granules is also a factor that controls the easy disintegration of the granules. Granules obtained by adding less than 1 part by weight of sucrose to 100 parts by weight of a composite powder comprising 30 parts by weight of carbonaceous compound fine particles and 70 parts by weight of graphitic carbon fine particles gave relatively hard particles.

However, dry granules obtained by adding 1 to 30 parts by weight of sucrose, preferably 2 to 18 parts by weight, more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the composite powder, can be pressed with a fingertip. To give easily disintegrable particles. The above tendency was also observed for methylcellulose. However, the solubility of methylcellulose in water cannot satisfy the requirement of the preferred range of the amount of the granulating agent to be added in the present invention in the entire region, and there is a problem that the use of an organic solvent such as methyl alcohol is indispensable in a mass use region. Thus, the most preferred embodiment of the invention is granulation with an aqueous sucrose solution.

(4) It has been found that the gas permeation amount of the carbonaceous compound / graphitic carbon composite molded article is governed by the firing temperature of the composite molded article in addition to the above granulation conditions. The present inventors have considered in the previous research that achieving a low corrosion current value required for a conventional phosphoric acid fuel cell also in a polymer electrolyte fuel cell is an essential issue, The product was obtained by carbonization at 1600 ° C.

However, a subsequent investigation showed that the operating temperature of the polymer electrolyte fuel cell was as low as about 100 ° C., and there was no corrosive substance such as phosphoric acid near the separator plate, and the composition was close to pure water. It was found that it was not necessary to substantially consider the corrosion current from the fact that was maintained. Further, in the prior art disclosed in the field in recent years, in order to reduce the amount of gas permeation, technology development in which a product of a type obtained by coating and curing graphitic carbon with an insulating phenol resin has become mainstream has been performed. From this, it was found that the small volume resistivity of the molded article which the present inventors regarded as an essential matter was not a controlling factor in the polymer electrolyte fuel cell.

That is, carbonization at 1200 to 1600 ° C., which the present inventors considered as essential operations for maintaining the corrosion current value and the volume specific resistance value at the same level as the phosphoric acid type fuel cell separator, is unnecessary. It was revealed. The present inventors evaluated the firing temperature dependency of the gas permeation amount of the green composite molded article. As a result, the green composite molded body is heated to 500 ° C., which is a temperature range in which the carbonaceous carbon compound is solidified by evaporation of volatile components in the carbonaceous compound and polymerization due to partial decomposition polymerization.
The gas permeation amount of the “carbonaceous carbon compound / graphitic carbon composite molded article” obtained by stopping the baking at 600 ° C. is in a temperature range where hydrogen is lost from the carbonaceous carbon compound and carbonaceous carbon is formed. It was found that the gas permeation amount was smaller than that of the “carbonaceous carbon / graphitic carbon composite molded article” obtained by firing at a certain 900 ° C. or higher. Gas permeation of 900 ° C fired product is 500 ~
The cause of the phenomenon that the amount of gas permeated by the product fired at 600 ° C. is larger than that of the product fired at 600 ° C. is assumed as follows.

When a single formed body of the carbonaceous compound fine particles constituting the composite formed body is heated and baked, it finally changes into a carbonaceous carbon formed body.
In the heating temperature range of ℃, the volatile light components contained in the carbonaceous compound are released, and the heavy components remaining in the polycondensation reaction are polymerized while releasing the decomposition gas and transformed into carbonaceous compounds. It is known that there is.

In this temperature range, it is known that the linear shrinkage of the compact is only a few percent. This phenomenon is called a carbonaceous compound
When it is applied to the graphitic carbon composite molded body, it is 500-6
In the 00 ° C. region, the linear shrinkage of the carbonaceous compound is small, and only the effect of suppressing the thermal swelling of the coexisting graphitic carbon molded article and making the dimensions of the green / fired molded article substantially the same is exhibited. You can think. The polycondensed and polymerized carbonaceous compound obtained at 500 to 600 ° C. gives a shape as a glassy solid. The vitreous solidified material has poor gas permeability and provides a carbonaceous compound / graphitic carbon composite molded article having a low gas permeability which is the object of the present invention.

When the carbonaceous compound that has undergone the polymerization process at 500 to 600 ° C. is further heated, the carbonaceous compound releases hydrogen in the temperature range of 700 to 900 ° C. and is converted into carbonaceous carbon. It is known that, during the carbonization process, a linearly compacted carbonaceous compound gives a linear shrinkage of 10% or more and shrinks by about 30% in volume. On the other hand, the composite molded body containing 70% of graphitic carbon, which is a typical composition of the present invention, has a linear shrinkage of only about 1% even at 900 ° C.

The difference between the amount of linear shrinkage of the carbonaceous carbon compact and the amount of shrinkage of the composite compact given baking at around 900 ° C. is considered to be due to the apparent impairment of graphitic carbon contraction of the carbonaceous carbon. . However, even in such a case, since the carbonaceous compound itself has a large amount of shrinkage, 500 to 600 ° C.
It is presumed that the vitreous solid derived from the carbonaceous compound formed in the region cracks, the gas passage is formed in a large amount, and the function as a gas impermeable body is reduced.

(5) As another means for obtaining a low-gas-permeability molded product aimed at by the present invention, a self-sintering carbonaceous material having an average particle size of 10 μm or less, preferably 1 to 7 μm, obtained as a result of the above-mentioned results. The use of a mixture obtained by stirring and mixing the compound fine particles and the graphitic carbon fine particles having an average particle size of 10 to 70 μm, preferably 15 to 50 μm in a dry state is conventionally useful. In such a mixture, the carbonaceous compound is evenly distributed around the graphitic carbon fine particles, and once melted and solidified at the time of firing at 500 to 600 ° C., a gas-permeable resistor close to vitreous is efficiently formed on the entire molded body. It is effective for (6) As an embodiment of the present invention, the carbonaceous compound / graphitic carbon composite formed form obtained by the present invention is subjected to high-speed cutting with a normal cutting machine to form a complicated polymer electrolyte fuel cell separator plate shape. A method of obtaining the desired molded product by baking under the heating conditions required by the present invention after the application is also effectively adopted.

As described above, the present invention mainly comprises a carbonaceous compound particle having an average particle diameter of 10 μm or less and a graphitic carbon fine particle having an average particle diameter of 10 to 70 μm containing a component exhibiting self-sintering property when heated. Mixing, granulating,
In a method for producing a carbonaceous compound / graphitic carbon composite molded article by molding and heating, the fine particle composition is mixed in a dry state, and the obtained homogeneous mixed powder is dissolved in a water-soluble carbonaceous compound and graphitic carbon. An aqueous solution containing at least one kind of an additive for bonding particles to a compound having tackiness is added and granulated, and water of the obtained granules is removed, and the obtained granules have a diameter of 0.5 to 20 mm. A method for producing a carbonaceous carbon compound / graphitic carbon composite molded body, characterized in that the dried granulated body of the above is molded using a press molding machine, and the obtained formed body is subjected to a heat treatment under a non-oxidizing atmosphere. Is what you do.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Embodiments will be roughly described in terms of raw materials, mixing / granulation, molding, and firing systems. Raw material system (1) As the graphitic carbon fine particles, both artificial graphite and natural graphite are used. Specifically, at least one type of graphite selected from the group consisting of flaky and earthy natural graphite and artificial graphite Carbon fine particles can be used. Artificial graphite is more preferred in terms of both physical properties and supply stability of graphite. Various artificial graphites supplied from the graphite molded body manufacturing industry can also be selected.

(2) The particle size of the graphitic carbon fine particles can be selected widely from the viewpoint of moldability. However, the volume resistivity,
From the viewpoint of simultaneously satisfying various physical properties such as thermal conductivity, strength of the molded body, dimensional stability of the formed green body and the fired green body, and gas permeability, even if it is too large or small, the object of the present invention is not met. The average particle size of the graphite fine particles can be selected from the range of 10 to 70 μm, preferably 15 to 50 μm.
Representative commercial products that can be used in the present invention include Timcal KS44 for artificial graphite, and CPB and CPB refined products of Japan Graphite for natural graphite.

(3) One of the controlling factors for producing a product having the same dimensions as the molded product and the carbonized molded product, which is a feature of the present invention, is the graphite carbon content, and there is a suitable range. Specifically, the content of the graphitic carbon fine particles in the composite powder composition comprising the self-sinterable carbonaceous compound fine particles and the graphitic carbon fine particles is 90 to 50 parts by weight, preferably 85 to 60 parts by weight,
More preferably, it can be selected from 80 to 65 parts by weight.

Note that the range of the graphite carbon content is also a factor governed by the self-sinterability of the carbonaceous compound, and is comprehensively determined in consideration of the characteristics of the self-sinterable carbonaceous compound. As a matter of course, there is room for improvement in the graphite-derived properties such as apparent bulk density, electric conductivity, and thermal conductivity as the content of the graphitic carbon is higher. However, if the sintering characteristics of the self-sintering carbonaceous compound and the average particle diameter described below are inappropriate,
Graphitic carbon swells during carbonization and may not be able to make use of the unique characteristics of graphitic carbon, so an appropriate design is required.

(4) The carbonaceous compound having a self-sintering property used in the present invention can be selected from various commercially available products. Preferred self-sinterable carbonaceous compounds have a γ component (quinoline-soluble toluene-insoluble component) content of 3 to
30% by weight, preferably 5 to 25% by weight, of the carbonaceous compound is used. If the content of the γ component is too small, the desired bending strength cannot be exhibited within the required range of the predetermined physical property value. On the other hand, if it is too high, for example 100, like coal tar
The fact that the material melts at a temperature of not more than ° C and cannot maintain the shape of the molded body and the uneven distribution of the self-sintering carbonaceous compound occurs cannot be used in the present invention.

Commercially available carbonaceous compounds having self-sintering properties which can be used in the present invention include TGP series and MPC series manufactured by Osaka Kasei, MCMB manufactured by Osaka Gas, KMFC manufactured by Kawasaki Steel, KS manufactured by Kureha Chemical and the like. Can be mentioned. Also, a high softening point pitch can be used as long as the content of the γ component is satisfied. There is no problem if the self-sintering carbonaceous compound is made of either coal tar or petroleum heavy oil as a starting material as long as the content range of the γ component required by the present invention is satisfied. In addition, there is no problem even if the material has an increased oxygen content by air oxidation, such as MPC-1 manufactured by Osaka Kasei Co., Ltd.

(5) The average particle size of the carbonaceous compound having self-sintering properties is an important factor that governs the bending strength and gas permeability of the carbonaceous compound / graphitic carbon composite molded article in the practice of the present invention. . The particle size effect of the product “TGP3000” commercially available from Osaka Kasei is shown below. TGP3000 is positioned as a pulverized product of self-sintering mesophase-containing pitch having a γ content of 21% (under 300 mesh sieve).

Even if TGP3000 is used as it is, a sintered body can be obtained. However, "TGP3000 (300
Mesh sieve) / artificial graphite powder with average particle size of 25 μm =
The bending strength of the 1000 ° C. fired product of the composite molded product obtained by mixing “3/7” was 100 kg / cm ² or less, and could not satisfy the bending strength required for the fuel cell separator plate. The gas permeability of the product was also in an inappropriate range. "TGP3000" was subjected to jet mill pulverization to obtain pulverized products having an average particle size of 10, 7, 3, and 1 µm, and a molded product was produced at the above ratio.
g / cm ² were obtained, and the gas permeability also decreased in proportion to the decrease in particle size. A preferable average particle size capable of comprehensively satisfying various physical properties was 7 μm or less. Particularly preferred average particle size was 3 μm or less.

This phenomenon is caused by the fact that the particle diameter of the self-sintering carbonaceous compound fine particles is reduced, so that the surface of the large graphitic carbon particles is filled with the self-sintering carbonaceous compound powder without gaps, and sintered by a firing treatment. By doing so, it is considered that the effect of improving strength and reducing the amount of gas permeation by forming a homogeneous glassy carbonaceous compound as a gas permeation resistor appears. That is, 70% of graphite particles having an average particle size of 25 μm (specific gravity = 2.2), and 30 of self-sintering carbon particles having an average particle size of 50 μm (specific gravity = 1.8) 30.
%, There is a calculation result that there are 15 graphitic carbon particles for one self-sintering carbonaceous compound particle.

Therefore, it is apparent that the effect of the presence of the self-sintering carbonaceous compound particles that contribute to sintering cannot be expected very much in the above-mentioned particle size relationship. By changing the average particle size of the self-sintering carbonaceous compound particles to 10, 7, and 3 μm, the graphitic carbon particles 1
The calculation is such that there are 8, 24, and 303 self-sinterable carbonaceous compound grains per piece. In the case of 10 μm, the calculation is such that one-third of the surface of one graphitic carbon particle is covered with self-sinterable carbonaceous compound particles. 7 and 3 μm respectively
It is a calculation that the surface of 2, 1 is covered with the self-sinterable carbonaceous compound particles. From the experimental results, it was found that half of the surface of the graphitic carbon
It can be seen that the required values of the bending strength and the gas permeability are satisfied in a situation where the calculated value of coating with the self-sintering carbonaceous compound particles is obtained. The effect is more complete with a 3 μm product.

It seems that the same effect can be obtained when the particle size of the carbonaceous compound is 7 μm or more as the size of the graphitic carbon particles increases. Since unacceptable problems such as gas permeability and groove smoothness occur, the particle size itself of the graphitic carbon particles is limited. As a result, the average particle size of the self-sintering carbonaceous compound is 7 μm. Is a preferred upper limit.

Mixing / granulation system The thickness of the separator plate is a weight controlling factor of the polymer electrolyte fuel cell system, and the thinner it is, the more preferable. For purposes such as automotive applications, it is premised to secure a huge number of separator plates having extremely uniform physical properties, and it is necessary to industrially form by a high-speed automatic unmanned press. In large-scale and homogeneous production by automatic unmanned presses, the flowability of powder supplied to a mold is a very important controlling factor. Granulated powder is indispensable in order to ensure quick and uniform flow of the powder supplied to the mold. With a simple mixture of graphitic carbon particles and carbonaceous compound particles, a mold cannot be filled quickly and uniformly, and the purpose of uniform mass production cannot be achieved.

(6) In the present invention, the operation of uniformly mixing fine self-sintering carbonaceous compound particles having a size of 1 to 10 μm and graphitic carbon particles having a size of 10 to 70 μm is performed by changing the surface of the graphitic carbon particles to self-sintering carbon. Coating with compound particles is extremely important in expressing the required properties in a molded article. Difficulties are associated with uniform mixing of the fine particles used in the present invention.

That is, when a mixing device with compression such as a crusher is used, it is remarkable for graphitic carbon particles having a flaky structure and exhibiting self-forming property by compression, particularly natural graphite particles having flakes. Before mixing with the self-sintering carbonaceous compound particles, the graphitic carbon particles adhere to each other, and it is virtually impossible to exhibit the desired characteristics that only the composite powder assuming uniform mixing is exhibited. .

On the other hand, in a mixer such as a ball mill, in which the pulverizing function is prioritized, the raw material itself is pulverized, and the performance of the compact is expressed on the premise that graphite carbon particles and carbon compound particles having a predetermined particle size are present. It becomes difficult. In a stirring and mixing device typified by a high-speed mixer, the above-mentioned problems hardly occur because the powder is mixed in a free floating state by using a rotary blade.

The present inventors have searched for optimal mixing conditions with a high speed mixer (Fukae Powtech). The mixture of carbonaceous compound particles and graphitic carbon particles is at least 50 ° C.
Preferably, two kinds of powders dried at around 100 ° C. are dried at room temperature to 100 ° C., preferably in a temperature range of 50 to 80 ° C.
It is obtained by mixing mainly using an agitator while purging the inside of the mixing tank with dry air or nitrogen gas so that moisture does not enter the mixing tank.

(7) While mixing the obtained mixed powder at room temperature, an aqueous solution containing a particle binding additive composed of a compound soluble in water and sticking to a carbonaceous compound and graphitic carbon is formed into a granulating liquid. A granulated body is formed by adding as.
Granulation can be easily achieved by using sucrose and using an aqueous solution in which sucrose is dissolved for the granulation liquid. The amount of sucrose used is 1 to 50 parts by weight, preferably 3 parts by weight, per 100 parts by weight of the mixed powder.
An embodiment of the present invention has a diameter of from 0.5 to 20 mm, preferably from 1 to 10 mm, more preferably from 1 to 5 mm, from 30 to 30 parts by weight, and the diameter of the granulated body from which moisture has been removed by drying after granulation.

(8) Granulation is achieved by adding an aqueous solution containing sucrose and / or methylcellulose, preferably sucrose as a granulating agent, to the powder after mixing, with stirring. A small amount of ions that remain in the separator and inactivate protons of the polymer membrane of the polymer electrolyte fuel cell, specifically, Ca ions, Na ions, and K ions, means that the granulating agent and the Required for granular liquids. (9) On an industrial scale, mixing and granulation are preferably performed separately. This can eliminate complicated steps such as mixing tank drying and adhering matter removal when the dry powder is introduced into an apparatus using water, and the mixing and granulating steps can be performed almost unattended.

Molding System In many fuel cell separator plates, a flow path for fuel gas (hydrogen) and oxidant (air) having a complicated shape is formed on the surface thereof. The shape varies from the information disclosed in the patent gazette. Many proposals have been made by manufacturers such as those having a flow path formed on only one side and those having formed on both sides. Although it is obvious to those who handle carbon molding materials, it is extremely difficult to form such a complicated shape on a carbonized or graphitized plate. It has to be an expensive product. Furthermore, mass production is extremely difficult for high hardness materials such as glassy carbon. An object of the present invention is to form a complicated shape in one shot at the time of automatic press forming by engraving such a complicated shape on a press die pressing surface in advance. In addition, a method in which the formed body is formed in advance in the form of a flat plate and is subjected to high-speed processing at least 10 times that of the carbonized formed body can be selected as an embodiment of the present invention.

Although it is technically possible to give a complicated shape by one-shot molding, there are usually problems such as the shrinkage generated during carbonization destroying the complicated shape and deforming the entire plate. Is not suitable for practical use. The method proposed by one of the present inventors, for example, Japanese Patent Publication No. 6-102
No. 530 discloses a method of molding a fuel cell separator using a graphite mold. Patent No. 2
JP-A-56659 discloses a method for mass-producing a thin-walled, bottomed, complex molded body by combining granulation means. In the present invention, a self-sinterable carbonaceous compound having a β content of about 21% derived from coal tar called TGP3000 as a representative example is combined with graphite to form a molded article having substantially zero dimensional difference between the formed article and the carbonized article. Whether or not a composite powder for a plate could be obtained was examined.

(10) TGP3000 is 200 to 400
It is a material that generates a large amount of decomposition gas components at ℃, and has unique physical properties as a so-called mesophase-containing pitch. However, it is known that a molded body made of TGP alone exhibits extremely high strength. The above-described TGP300 powdered into various particle sizes is mixed with artificial graphite “KS44” manufactured by Timcal Co., Ltd. in various ratios using a high-speed mixer, and then granulated with sucrose outside ratio of 10%, and dried at 110 ° C. to form granulated powder. Molded at a pressure of 1.5 ton / cm ² under an inert gas atmosphere.
The temperature was raised to 600 ° C. at a rate of 0.2 ° C./min to obtain a fired molded body, and dimensional changes before and after firing were observed.

As a result, the average particle size of TGP3000 was 3 μm.
The product had TGP3000 = 30% and KS44 = 70%, and the linear shrinkage before and after firing was substantially zero. TGP3
Although the optimum value slightly fluctuated due to the change of the average particle size of 000, a composition having a substantially zero linear shrinkage can be set within the range of TGP = 26 to 30%. If a composition with a linear shrinkage of zero can be set, one-shot molding of a complex-shaped product similar to the previously developed technology can be achieved.
This is made possible by the re-pulverized GP3000, a special but mass-produced product.

The present inventors used commercially available self-sinterable carbon materials “KMFC” and “MCMB” to dry dry and wet granulate the components of the present invention and prepared them through the dry mixing and wet granulation processes. The same test was performed on the granulated powder, and TGP3000
Similarly, a composition having a linear shrinkage of zero can be found. In the automatic press molding, the lower punch is moved to a predetermined position after a slightly larger amount than the predetermined amount of the granulated material is put into the mold frame based on the bulk density of the dried granulated material and the compaction density at the time of molding. It is a general technique to brush the granulated powder overflowing to the upper surface of the mold by brushing to determine the filling amount, and to shift to a predetermined pressing operation. In this case, it is important that the bulk density of the granulated powder is constant in order to keep the product thickness constant. An important factor is also the flowability of uniformly filling the mold frame in a short time.

The so-called spring-back phenomenon, in which the molded product obtained by molding gives a slightly larger size than the mold, is well known. It is known that when this phenomenon occurs, the probability of breakage when the molded body is removed from the mold increases, but as a countermeasure this is a technique within the range of common sense in the industry, but it is a technique called a punching allowance in the mold. By applying a large taper, breakage can be avoided.

The formed body swelled from the mold size by springback can be linearly contracted to the same level as the mold size by applying the preferable firing conditions of the present invention. It is also possible to obtain a fired molded body with the expanded dimensions. In the firing of a formed product in which a complicated shape is stamped in advance, it is more preferable to select the firing size as it is in the swollen shape.

In any case, the mixing ratio of the self-sinterable carbonaceous compound can be selected by a material design that is set to a level that gives a desired linear shrinkage. Incidentally, the influence of the molding pressure on the springback amount can be almost ignored.
It was also confirmed that the molding pressure in the range of 0.5 to 2 ton / cm ² did not affect the linear shrinkage rate under the firing conditions of the present invention.

The combination of the above two findings makes it possible, as an embodiment of the present invention, to imprint a complicated shape on the formed feature during molding. That is, 1mm width on both sides,
In the case of a grooved separator having a large number of grooves with a depth of about 1 mm, for materials with different linear shrinkage during firing depending on the molding pressure, finely adjust the charged amount of granulated powder according to the presence or absence of grooves, and make it uniform over the entire molding surface Molding pressure must be ensured. However, for high-volume, high-speed production, fine adjustment of the charged amount is substantially impossible in the essential embodiment of the present invention. Therefore, the molding pressure fluctuates greatly in the vicinity of the groove, which directly affects the linear shrinkage ratio during firing, and causes distortion and cracking of the fired molded body. The reason why the influence of the molding pressure on the amount of linear shrinkage in the carbonaceous compound / graphitic carbon composite molded article of the present invention is substantially zero is that the swelling of the flake graphite upon heating acts as a buffer mechanism to absorb fluctuations in the molding pressure. It is presumed that it is.

The range of the self-sintering carbonaceous compound slightly varies depending on the starting material, heat treatment method and content of the γ component.
Light components (vorat) contained in the temperature range of 50 to 500 ° C.
The remaining components are polymerized by a partial polycondensation reaction to form a non-fusible polymer compound while releasing hydrogen and the aromatic hydrocarbons are released from the polymer hydrocarbon compound while the temperature reaches 800 to 900 ° C. It is well known that the transition to carbonaceous carbon, which is a large aggregate of fused aromatic rings, is performed.

In the present invention, the self-sintering carbonaceous compound volatilizes its volatile light component, and a part of the remaining high-boiling compound undergoes a polycondensation reaction to change into a non-melting high-molecular carbonaceous compound. By performing heat treatment in an inert atmosphere up to the temperature, a carbonaceous compound / graphitic carbon composite molded body is obtained. That is, one of the features of the present invention is that the heating temperature range of the formed body is 400 to 7
The temperature is limited to 00 ° C, preferably 450 to 650 ° C. If the amount of gas generated from volatile matter and decomposition products of high-boiling substances is too large in the course of the temperature of the molded body reaching 500 to 600 ° C., if the amount of gas generated is too large, the molded body itself is caused by the internal pressure caused by the gas retained inside the molded body. Swelling and sometimes lose their form as a compact.

On the other hand, the area of the formed body and the molding pressure are also major controlling factors for the swelling of the formed body due to the staying gas. In a preferred embodiment of the present invention, the escape resistance of the gas in the thickness direction is extremely large because the flaky graphite is superimposed in the thickness direction, and the momentum gas escapes in the lateral direction, so that the larger the area and the higher the molding pressure, the more the gas. Becomes difficult to come off. Further, the decomposition and swelling characteristics of the granulating agent used in the preferred embodiment of the present invention are also important factors to be considered in determining the heating rate.

That is, sucrose and methylcellulose of various degrees of polymerization are mentioned as preferred granulating agents in the present invention, but these compounds have the property of melting at 200 ° C. or lower and partially swelling. Further, in the temperature range of 200 to 300 ° C., a solidification and swelling phenomenon of sucrose, which is known in carmela baking, occurs. Therefore, in performing the calcination of the present invention, it is necessary to raise the temperature in the temperature range up to 300 ° C. at an appropriate rate in consideration of the content of the granulating agent.

In consideration of the factors relating to the above-mentioned swelling, the rate of temperature rise in firing the green compact of the present invention is from 0.01 to 3 ° C./min, preferably from 0.05 to 3 ° C., from room temperature to the desired firing temperature range. To 2 ° C / min, more preferably 0.1 to 1 ° C / min. When oxygen contacts the compact during firing, the self-sintering carbonaceous compound absorbs oxygen and becomes an oxygen-containing carbonaceous compound in a temperature range of 200 to 500 ° C. In this case, a difference in linear shrinkage from the carbonaceous compound which has not been oxidized can be caused, so that the oxygen content of the carbonaceous compound causes distortion and breakage of the molded body.

Further, contact with oxygen at 400 ° C. or more promotes selective combustion of carbonaceous compounds among the constituent components of the composite molded article. For this reason, the composite molded article loses its self-sintering property and in the worst state does not form a molded article. Therefore, it is one of the indispensable embodiments of the present invention to suppress the intrusion of oxygen during firing in the temperature range.

As a method for suppressing the oxygen erosion of the carbonaceous compound in the heating temperature range required by the present invention, a conventionally known technique, for example, an inert gas (preferably nitrogen gas) atmosphere heating can be mentioned. . "Coke Please", which is used as a filler for carbonization reactions, which are commonly used
Does not have the ability to inhibit oxygen intrusion in this temperature range. Therefore, the present inventors have prepared an oxygen permeation inhibiting layer obtained by mixing linseed oil with coke please disclosed in Japanese Patent Application Laid-Open No. Hei 5-186265. A method of substantially eliminating oxygen penetration up to a temperature of 500 ° C. by setting the temperature at 500 ° C. can also be used in combination with heating in a nitrogen atmosphere. Oxygen erosion of the composite molded body can be completely suppressed by a method of mixing a powder having an appropriate size (for example, TGP2000) of the carbonaceous compound of the present invention with coke breath and including the formed form. In this case, nitrogen may be added.

[0058]

EXAMPLES The contents of the present invention will be described more specifically with reference to the following examples. Example 1 A mixing tank containing 75 g of self-sintering carbonaceous compound fine particles having an average particle diameter of 3 μm (TGP3000 manufactured by Osaka Kasei Co., Ltd., which was pulverized by a jet mill), which reached a constant drying weight in a hot air circulation type drier kept at 110 ° C. High-speed mixer (LFS-GS-2J) manufactured by Fukae Powtech Co., Ltd.
), And while blowing out dry nitrogen from the agitator and chopper shafts, the artificial graphite (SFG44) 1 manufactured by Timkar having an average particle size of 25 μm under stirring conditions of an agitator rotation speed of 800 rpm and a chopper rotation speed of 1000 rpm.
75 g was charged with a spatula in 5 minutes, and stirring was continued for another 5 minutes. Observation through the viewing window of the lid revealed that the powder was mixed smoothly.

After the temperature of the mixing tank was set to 25 ° C., an aqueous solution for granulation consisting of 27.5 g of sucrose and 155 g of water was fed with an agitator rotation speed of 300 rpm and a chopper rotation speed of 3000 r.
The mixture was injected at pm into the mixture during mixing for 2 minutes and granulation continued for 3 minutes. The obtained granules were dried with a hot-air circulation dryer set at 110 ° C. for 4 hours and cooled to room temperature. Dry granules having a grain diameter of 1 to 3 mm were obtained.

Pressing up and down on a 2-axis 600-ton press
Both flat and horizontal 200 mm vertical and horizontal molds are installed.
Was placed. 210 g of the dried granules are charged and degassing operation is performed.
1.5 ton / cm after^Two Molded with a molding pressure of 3.0m
m were obtained. Flat placed in a stainless steel container
The upper and lower sides of the compact are sandwiched between graphite plates with a thickness of 50 mm having a smooth surface.
And filled around the formed form and inside the container. Inner volume 15
Place the vessel in a 0L muffle furnace and place an alumina
Every minute while supplying nitrogen at a supply rate of 5 L / min from Ip
Heat to 500 ° C at a rate of 0.15 ° C and hold for 2 hours
After that, the furnace was cooled to room temperature under a nitrogen stream. The resulting carbonaceous material
The compound / graphitic carbon composite flat molded product is the size of the raw flat molded product.
This gave a coefficient of linear expansion of 0.04% compared to the method. The obtained result
No distortion or destruction was observed in the form. Obtained flat plate
Nitrogen back pressure of 1 kg in the center of the form within 15 mmΦ
/ Cm ^Two The amount of gas leaked from the corresponding part on the back side supplied by G
I asked. 2 × 10 as gas permeability^-Fivecc / min
/ Atm / cm^Two I got

[0061]

Industrial Applicability The present invention provides a method for efficiently producing a carbonaceous compound / graphitic carbon composite molded article having an extremely small gas permeability, and is intended to provide a separator for a polymer electrolyte fuel cell having a complicated shape. This facilitates the production of boards.

Claims (10)

[Claims] 1. A composite powder comprising a carbonaceous compound particle having an average particle diameter of 10 μm or less and a graphitic carbon fine particle having an average particle diameter of 10 to 70 μm containing a component exhibiting self-sintering property when heated. Mixing, granulating, molding and heating to produce a carbonaceous compound / graphitic carbon composite molded body, wherein the fine particle composition is mixed in a dry state, and the obtained homogeneous mixed powder is dissolved in water-soluble and carbon Granules obtained by adding an aqueous solution containing at least one kind of additive for binding particles to a porous compound and a compound having adhesiveness to graphitic carbon, and removing water from the obtained granules. A carbonaceous carbon compound / graphitic carbon composite molded body characterized in that a dried granulated body having a diameter of 0.5 to 20 mm is molded using a press molding machine, and the resulting formed body is subjected to heat treatment in a non-oxidizing atmosphere. Manufacturing method. 2. The carbonaceous compound particles having a self-sintering property have a γ component (quinoline-soluble toluene-insoluble component) content of 3 to 3.
The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1, which is 30% by weight. 3. The composite powder has a carbonaceous compound fine particle content of 10 to 10.
The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1, which is a composition containing 50 parts by weight and 90 to 50 parts by weight of graphitic carbon fine particles. 4. An average particle size of carbonaceous compound fine particles containing a component exhibiting self-sintering property is 1 to 7 μm, and an average particle size of graphitic carbon fine particles is 15 to 50 μm.
3. The method for producing a carbonaceous compound / graphitic carbon composite molded article according to 1.). 5. The carbonaceous compound fine particles are subjected to a thermal reaction of a graphitic hydrocarbon compound of coal-derived tar and / or petroleum-derived tar to give a desired γ component content and then pulverized to give a desired particle size. The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1. 6. The carbonaceous compound / graphitic carbon composite molding according to claim 1, wherein the amount of the additive for binding particles to each other is 1 to 50 parts by weight based on 100 parts by weight of “carbonaceous compound + graphitic carbon”. How to make the body. 7. The method for removing water from a granulated body in air is 50 to 12
The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1, which is carried out at 0 ° C. 8. The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1, wherein the particle diameter of the dried granulated substance is 1 to 10 mm. 9. The method for producing a carbonaceous compound / graphitic carbon composite molded article according to claim 1, wherein the heat treatment of the formed body in a non-oxidizing atmosphere is performed in a temperature range of 400 to 700 ° C. 10. The carbonaceous compound according to claim 1, wherein the non-oxygen atmosphere of the formed form is formed by a mixture of a carbonaceous compound powder and coke breath forming the formed form.
A method for producing a graphitic carbon composite molded article.