JPS59195514A - Molded impermeable carbon body and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a molded carbon body having high strength and impermeable to gas and liq. by molding a composition consisting of thermosetting resin powder, graphite powder and a thermosetting resin soln. to a prescribed shape, drying and curing the molded body, and carbonizing and calcining it in a nonoxidizing atmosphere. CONSTITUTION:Thermosetting resin powder is blended with graphite powder and a thermosetting resin soln. so that carbonaceous matter after carbonization and calcination is composed of 5-50wt% graphite and the balance vitreous carbon formed by the carbonization and calcination of the thermosetting resin. An aqueous or org. soln. of thermosetting resin is used as said thermosetting resin soln. An emulsion or a suspension may be used. The blend is molded to a prescribed shape. The molded body is dried and cured, and it is carbonized and calcined in a nonoxidizing atmosphere to manufacture a molded impermeable carbon body consisting of graphite and vitreous carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an impermeable carbon molded article and a method for producing the same.

Impermeable carbon molded bodies, which are highly impermeable to gases and liquids, have low electrical resistance and excellent chemical resistance in addition to these properties, making them widely used in industrial fields such as electronics, nuclear power, and aerospace. Among them, because of the above-mentioned characteristics, it can be suitably used as a separator plate for phosphoric acid fuel cells, which have been attracting attention in recent years.

In a phosphoric acid fuel cell, for example, a pair of porous electrode plates carrying a required catalyst are arranged with a matrix impregnated with phosphoric acid as an electrolyte sandwiched between them, and a separating plate is arranged on the outside of each of the porous electrode plates. A unit cell is formed and a large number of unit cells are stacked. For example, in the case of a fuel cell called a ribbed electrode type, ribs are formed on the separation plate side of each electrode, and fuel gas or oxidant gas is supplied to the grooves between these ribs. That is, a gaseous fuel such as hydrogen scum is supplied to the grooves of one electrode, and a gaseous oxidizing agent such as air or oxygen is supplied to the grooves of the other electrode, thereby carrying out a cell reaction. Therefore, since one separator plate is supplied with fuel on one side and oxidizer on the other side, the separator plate is immediately impermeable to gases to prevent these gases from mixing. In addition, in order to function as a current collector for a fuel cell constructed by stacking unit cells as described above, it is necessary to have high conductivity and to have a large stacked structure in the form of a thin layer. It is necessary to have compressive strength and bending strength.

However, all of the conventionally known impermeable carbon molded bodies are insufficient in the above-mentioned required characteristics. For example, JP-A No. 51-20991 discloses that fine powder of cured phenolic resin and phenol/aldehyde initial condensate are kneaded, molded and hardened, and then carbonized and fired to produce substantially only glassy carbon. A method for obtaining a carbon molded body consisting of the following is disclosed. However, in this way f-W
The resulting molded product lacks denseness as a molded product because the resin undergoes significant shrinkage during the firing process.
Therefore, the gas impermeability is not sufficient, and furthermore, when the thickness is reduced to about 0.4 to 1.511V, which is preferable for an actual separation plate, the strength is poor.

On the other hand, various impermeable carbon molded bodies whose carbonaceous substance is graphite are already known. For example, an impermeable carbon molded body can be obtained by impregnating the voids of a graphite molded body obtained by carbonization firing with an impregnating material such as pitch, cool, or resin, and then firing it again to carbonize the impregnating material. Although it is known, according to this method, cracks often occur in the resulting carbonized and fired product due to the difference in thermal shrinkage rate between the graphite molded body and the impregnated material.

Furthermore, JP-A-57-72273 discloses a method for obtaining an impermeable carbon molded body made entirely or substantially of graphite by molding graphite powder with a phenol resin liquid and firing at a high temperature. Even if this method is used, as mentioned above, the difference in thermal shrinkage between the graphite and the binder will cause cracks or cracks during firing. Repeat and include d・l
The number of culms increases, and the molding cost also becomes the market price.

The present invention has been made in order to solve the various problems mentioned above.The present invention has been made in order to solve the various problems mentioned above. The purpose of the present invention is to provide a carbon molded body and a method for manufacturing the same.

The impermeable carbon molded article according to the present invention is characterized in that carbonaceous graphite accounts for 5 to 50% by weight, and the remainder consists of glassy carbon formed by carbonizing and firing a thermosetting resin. , such an impermeable carbon molded body according to the present invention:
Thermosetting resin powder, graphite powder, and thermosetting resin are mixed so that graphite accounts for 5 to 50% by weight of the carbon after carbonization firing, and the remainder consists of glassy carbon formed by carbonization firing of thermosetting resin. Molding the liquid and other compositions into the desired shape,
After drying and hardening, it is produced by carbonizing and firing in a non-oxidizing atmosphere.

7) In the invention, the thermosetting resin powder is 800 to 2000'(preferably') in a non-oxidizing atmosphere.
4 Thermosetting resin powder that changes into vitreous carbon by carbonization firing at a temperature of 1000~1500'C, usually containing phenolic resins, furan resins, xylene resins, melamine resins, aniline resins, etc. Resin powder is used, and in particular, 1'5) powder of phenolic resin is preferably used. Further, as the thermosetting resin liquid, for example, an aqueous or organic adhesive such as a phenol resin, a xylene resin, a melamine resin, a urea resin, an epoxy resin, or a furan resin is used. In addition, the resin liquid includes emulsion ltν and (U suspension) in addition to molten liquid ν.

In the present invention, the aqueous 4AJ fat liquid is preferably used for convenience of drying, although it is not limited to l+.

The above-mentioned thermosetting resin No. 5] powder and resin liquid can be used alone or as a mixture of two or more, or the thermosetting resin powder and the 4AJ fat liquid in the resin liquid are the same resin. That is desirable. This resin liquid facilitates kneading of the thermosetting resin powder and graphite powder and molding into a desired shape, and after curing, it is baked together with the thermosetting resin powder to form amorphous glass. Forms carbon and graphite 7 trifuses.

As described above, both the thermosetting resin powder and the thermosetting resin in the resin liquid change into vitreous carbon by carbonization firing in a non-oxidizing atmosphere, but in the method of the present invention, graphite is converted into glassy carbon after carbonization firing. Graphite accounts for 5 to 50% of the carbonaceous material contained.
, and the remainder consists of the thermosetting resin powder and thermosetting resin liquid (41). It is preferable to form a uniform composition by blending and kneading, and furthermore, the thermosetting resin powder used here has an average particle size of 50 μm or less, and the graphite powder is mixed with this thermosetting resin powder. It is preferable that the average particle size is 1/2 or less of the average particle size of 1.

According to the present invention, the resin component in the thermosetting resin powder and resin liquid is dehydrogenated and shrinks when carbonized by firing, or graphite powder that does not substantially heat shrink is present in the above range. In addition, preferably when the thermosetting 111 fat powder and graphite have an average particle size within the above range,
The so-called close packing of graphite is achieved in the molded body, and a dense molded body excellent in both gas impermeability and strength can be obtained. In the molded body obtained by carbonization firing, when the amount of graphite in the total amount of carbonaceous material formed from graphite and the above thermosetting resin is less than 5% by weight, close packing of graphite in vitreous carbon occurs. is not achieved,
On the other hand, when it exceeds 50% by weight, the thermosetting resin powder and the thermosetting resin in the resin liquid cannot be densified by firing, and rather the strength of the vitreous carbon that binds the graphite powder is extremely reduced. At the same time, the gas impermeability of the obtained molded article also decreases. Also, even when the average particle diameter of the thermosetting resin powder exceeds 50 μm, dense and strong molding is possible. It is difficult to understand. If the average particle size of graphite is larger than 1/2 of the average particle size of the thermosetting resin powder used, internal stress will occur when the cured thermosetting resin and resin liquid are carbonized and fired, and the stress will also be reduced to 1M. This will reduce the strength of the molded body.

In the method of the present invention, thermosetting resin 4''Ij powder, graphite and hardenable, !3] fat liquid are uniformly kneaded and shaped into a desired shape by an appropriate method such as pressing, extrusion, or rolling. After molding, it is dried to volatilize the solvent in 4A1 resin, and then heated to harden the resin.The temperature for drying this resin liquid and curing the resin is determined as appropriate depending on the resin liquid used. If necessary, the resin liquid may be cured by heating to obtain a molded body, and then this molded body may be further impregnated with the resin liquid, dried, and heated to be cured.

The molded body thus formed at °C is then carbonized and fired in a non-oxidizing atmosphere. The atmosphere is usually
Helium, argon, nitrogen, etc. are used. Heating for carbonization and firing to obtain an impermeable carbon molded body is performed at temperatures ranging from about 200°C to about 500°C to about 60°C, for example, as described in JP-A-57-72273+U.
It is preferable to heat at a slow temperature increase rate of several tens of degrees C/hour until the temperature reaches 0 degrees Celsius. Thereafter, the impermeable carbon molded body of the present invention is heated to a predetermined carbonization firing temperature at a heating rate within the above range or higher, and is heated to a predetermined carbonization firing temperature for a predetermined time or every time it is formed. Temperature is at least 800℃
is required, and preferably the temperature is 1000 to 1500°C. The required firing time also depends on the shape and dimensions of the molded product, and virtually all thermosetting fats are carbonized,
All you have to do is fire it for a long enough time to turn it into glassy carbon.
Usually, it is several hours to several tens of hours.

In the present invention, in order to further increase the strength of the molded product obtained, a substance having good bonding properties to the carbon matrix of the molded product, such as carbon fluff, silicon carbide, titanium carbide, tungsten carbide, etc., is used. Appropriate amounts of metal carbide, carbon fiber, etc. can be added to a molding raw material consisting of thermosetting resin powder, graphite, and thermosetting resin liquid, and this can be molded, dried, and fired as described above.

As described above, according to the present invention, graphite and thermosetting resin are mixed so that graphite occupies a predetermined proportion on the back of the carbonaceous material made of vitreous carbon formed from graphite and thermosetting resin after carbonization firing. The powder and thermosetting resin are mixed and kneaded, molded, and carbonized to convert the thermosetting resin into glassy carbon. It is uniformly dispersed in the glassy carbon matrix formed by the process, giving a dense carbon molded body without cracking, and the impermeable carbon molded body thus obtained has excellent impermeability to gases and liquids. In addition, it has excellent strength such as laminated compressive strength and bending strength, and conductivity.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Phenol-formaldehyde resin powder with an average particle diameter of 39 μrn and graphite powder with an average particle diameter of 12 μm containing 99% or more of fixed carbon were carbonized and fired to form a carbon consisting of vitreous carbon and graphite formed from a thermosetting resin. Of these, 44% of phenol contains graphite in the proportion shown in Table 1.
1 fat liquid (concentration 50%) was uniformly kneaded and formed into a thin plate. After drying this at a temperature of 30°C for 4 hours,
The thermosetting resin is cured by heating to a temperature of 0°C for 6 hours,
Then, it was charged into a firing furnace and heated at 700° under an argon atmosphere.
Heating at a heating rate of 40°C/hour to a temperature of C, then heating at a rate of 100°C/hour to a temperature of 1300°C, and holding at a temperature of An impermeable carbon molded body having a length of 100 mm and a width of 70 mm was obtained.

Table 1 shows the hydrogen permeability, longitudinal electrical resistance, bending strength, and lamination compressive strength of each of the molded bodies thus obtained.

In addition, in Table 1, examples (graphite amount 1 in carbonaceous material
5 market weight%) and comparative example (graphite amount 0 insect amount% in carbonaceous material)
) Electron micrograph (1000x) of the surface of the molded product obtained in
are shown in FIGS. 1 and 2, respectively. According to the impermeable carbon molded article of the present invention, the carbonaceous material is dense and there are substantially no voids, whereas the molded product of the comparative example has voids in the carbonaceous material.

Example 2 Example 1 Odor (,4 AI Jl!, i lIk as ljt of so:1-nol (41 fat liquid (70% 1-%) and furan resin dk (30 LI bow f>6) Compound (combination, jl 4!j fat θY2 degree ↓ Schiff using 5 shiron)
Soi Example 1 and 111 were used for carbonization firing.
j: Glassy carbon formed from 4H curable 4Lj fat and black≦゛(1 and carbonaceous carbon, black ε1) or the same contained in a small proportion in Table 2. Ij1 saw the transparent carbon molded body.

The hydrogen permeability, longitudinal electrical resistance, bending strength, and lamination compressive strength of each of these molded bodies are listed in Table 2.

Example 3 In the same manner as in Example 1, except that furan resin powder with an average particle size of 41 μm was used as the thermosetting resin powder and furan resin liquid (80% urine content) was used as the resin liquid, By carbonization firing - (carbonaceous backside consisting of glassy carbon formed from thermosetting resin and black JD, graphite or not shown in Table 3; impermeability of the same dimensions included in lily-coating) The carbon molded body is f4j.

For each of these molded bodies, hydrogen permeability, electrical resistance in the longitudinal direction of the molded body, bending strength, and t1'! The layer compressive strength is shown in Table 3.

[Brief explanation of the drawing]

Figure 1 is a small-scale electron micrograph (1000x) of the surface of the impermeable carbon molded body according to Example 1 of the present invention, and Figure 2 is a comparative example of the impermeable carbon molded body that does not contain graphite. This is an electron micrograph (1000x magnification) showing the surface of . Patent applicant Kobe Co., Ltd.! l! ! ! Copper Works Agent Patent Attorney Itsube Makino

Claims (4)

[Claims] (1) An impermeable carbon molded body characterized in that graphite accounts for 5 to 50% by weight of the carbonaceous material, and the remainder consists of vitreous carbon formed by carbonizing and firing a thermosetting resin. (2) Thermosetting resin powder and graphite powder are mixed so that graphite accounts for 5 to 50% by weight of the carbon after carbonization firing, and the remaining 91S consists of glassy carbon formed by carbonization firing of thermosetting resin. 1. A method for producing an impermeable carbon molded body, which comprises molding a composition comprising a thermosetting resin liquid into a desired shape, drying and curing the composition, and then carbonizing and firing it in a non-oxidizing atmosphere. (3) Impermeability according to claim 2, characterized in that the thermosetting resin powder has an average particle diameter of 50 μm or less, and the graphite has an average particle diameter of 1/2 or less of the powder. A method for producing a carbon molded body. (4) The method for producing an impermeable carbon molded body according to claim 2, wherein the firing temperature is 800 to 2000°C.