JPS6042212A - Manufacture of heat resistant impermeable carbonaceous material - Google Patents

Abstract

PURPOSE:To manufacture a heat resistant impermeable carbon article by oxidizing the surface of pulverized coke or graphite, kneading the coke or graphite with a specified resin as a binder, molding the kneaded material, and calcining the molded body in an inert gaseous atmosphere. CONSTITUTION:When a carbon article with high gas impermeability used as the partition wall member of a phosphoric acid type fuel cell is manufactured, fine powder of petroleum coke, pitch coke, artificial graphite, natural graphite or the like having <=100mesh particle size is prepd. The surface of the pulverized carbonaceous material is uniformly oxidized, and 100pts.wt. of the material as filter are kneaded with 14-80pts.wt. precondensate of a thermosetting resin having at least 40% rate of residual carbon such as phenol resin or furan resin. The kneaded material is molded into a prescribed shape by a hot press molding method, and the molded body is calcined at 900-1,300 deg.C in an inert gaseous atmosphere to obtain a carbon article with remarkably high gas impermeability without reducing heat resistance, corrosion resistance and electric conductivity peculiar to carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ij thermophilic carbonaceous material useful for use in partition members of phosphoric acid fuel cells, etc.

Although carbonaceous materials inherently have excellent heat and corrosion resistance as well as electrical conductivity, the m-weave has an extremely porous structure, so it cannot be used in highly gas-impregnated materials such as diaphragms for phosphoric acid fuel cells. It cannot be applied as is to applications that require transparency. Methods to solve this problem include methods of impregnating a carbonaceous base material with a thermosetting resin liquid and curing it to close the skeletal pores (resin impregnation method), kneading carbonaceous powder with a large amount of a thermosetting resin binder, and heating it. Method of forming a dense structure by pressure forming (
However, since the materials obtained by these methods have a large amount of 411 fat component present in their structure, they have high heat and corrosion resistance and high electrical conductivity, which are unique to carbonaceous materials. There are drawbacks to setting back.

Also known is a method (resin bonding firing method) in which the molded body obtained by the resin bonding method described above is further fired in an inert atmosphere. When using this method, the intervening resin component is eventually carbonized, so heat resistance and corrosion resistance and electrical conductivity are restored, but the degree of gas impermeability that is problematic is limited to the starting material filler and resin. It is largely controlled by the properties of the binder.

The present invention was developed as a result of multifaceted studies on the optimal conditions for imparting gas impermeability in the resin bonding firing method.
Coke or graphite fine powder of 0.00 mesh or less is used as a filler, and an initial charge of a thermosetting resin having a residual carbon content of at least 404 is added and mixed, and after hot-pressure molding, the molded body is placed in an inert atmosphere. It is characterized by being fired inside.

Fillers that serve as starting materials are carbonaceous materials such as petroleum coke, pitch coke, artificial graphite obtained by graphitizing these cokes at 2,800 to 3,000°C, and unburned graphite, which are finely ground to a particle size of 100 mesh or less. Use fine powder whose surface has been uniformly oxidized in advance. Homogeneous surface oxidation is achieved by dry oxidation, in which fine filler powder is exposed to high-temperature oxidizing gas (e.g., air heated to 500°C or higher) while flowing or rolling, or evenly sprayed with it. Alternatively, a wet oxidation method is applied in which fine filler powder is immersed and stirred in nitric acid, hydrogen peroxide solution, permanga/potassium acid bath solution, etc., and then washed with water.

For the binder, an initial charge of a thermosetting resin having a residual carbon content of at least 40% is selectively used, and a phenolic resin, a furan resin, or a mixed resin thereof is particularly effectively used.

The resin binder is added in an amount of 18 to 40 parts by weight per 100 parts of fine filler powder, and thoroughly kneaded.

The filler fine powder has been subjected to a level surface oxidation treatment JJl! Since its surface area is significantly larger than that of K, and active functional radicals represented by carboxyl groups are generated on the entire surface, the binder resin component during the kneading stage is This effectively improves the mutual adhesion between the wire and the wire, and converts it very smoothly into a homogeneous cross-wire configuration with high bonding strength. At this time, by applying a pressure of 0.1 Kg/cA or more from the top of the kneaded material, the kneading can proceed more uniformly and quickly.

The kneaded material is subjected to preliminary treatments such as drying, pulverization, and division as it is, and then molded by hot pressure molding. Appropriate heat and pressure conditions include a heating temperature of 120-270℃.
By setting the temperature and the load pressure in the range of 100 to 800 F/-, a dense texture sufficient to impart gas impermeability after firing is formed under these conditions.

The molded body is then packed into a firing furnace such as a beam-done furnace and heated to a temperature of 900 to 130°C while maintaining the surrounding area in an inert atmosphere.
It is fired at a temperature of 0°C, and if necessary, it is further transferred to a graphitization furnace and graphitized at 2800 to 3000°C.

During firing, the resin component present in the molded body carbonizes with thermal decomposition shrinkage, but throughout this process, the highly bonded state based on the mutual adhesion of the filler and binder during the kneading stage is maintained without damage. It functions to provide sufficient rigidity and compactness to obtain a highly gas-impermeable tissue.

As described above, according to the present invention, a high-grade heat-resistant and impermeable carbonaceous material can be constantly and stably produced due to its unique functions, so it can be applied to the manufacturing method of diaphragms for phosphoric acid fuel cells. It is extremely effective.

Hereinafter, the present invention will be explained based on examples.

Fruit B (li Example 1) Petroleum coke powder and artificial graphite powder obtained by graphitizing it at 2800°C are finely ground to a particle size of 150 mesh or less, and placed in a rotary drum and rolled while being rotated.
Oxidation was carried out for 12 minutes by continuously introducing air heated to 0°C. After each fine powder (filler), which had undergone homogeneous surface oxidation in this way, was put into a kneader, resol type phenol was added. The initial charge of the resin (residual carbon content: 49%) was added as bi/goo, and the mixture was stirred and kneaded for 2 hours.

The amount of resin binder blended at this time was 10% of filler fine powder.
The amount was 22.5 parts by weight based on 0 parts by weight.

Next, the mixed wire was filled into a mold arranged in a 550 mm order in the vertical and horizontal directions, and molded into an rA-shaped body under heat and pressure conditions of a heating temperature of 140° C., a load pressure of 300 V, and g/cM.

Each of the plate-shaped compacts was transferred to a lead-burning furnace, the outer periphery was covered with a coke backing, and fired at a temperature of 1000° C. while maintaining an inert atmosphere inside the furnace.

The obtained carbonaceous material had a volume shrinkage of around 90 modulus compared to the molded product before firing due to the thermal decomposition and carbonization of the binder resin component, but it was extremely strong and dense with no cracks or cavities observed in the structure. It had a structure.

For comparison, a carbonaceous material was manufactured under the same conditions as above without surface oxidation treatment. In this case, internal cracks (occurring) occurred during the firing stage.

Various physical properties of the carbonaceous material thus produced were measured, and the results are compared and shown in the table below.

In the characteristic tests, the gas permeability was determined as N passing through a sample thickness of 5 mm under a pressure of IKg/crA, and the amount of gas permeation (cc, 4 nin).

From the results in the above table, the carbonaceous material manufactured by the example of the present invention (with surface oxidation treatment) has a high degree of gas impermeability, and is also superior to the comparative example (without surface oxidation treatment) in other characteristics. It turns out that there is.

Example 2 Natural graphite fine powder adjusted to a particle size of 150 mesh or less was immersed in nitric acid with a concentration of 60 parts, wet oxidized for 2 hours with intermittent stirring, washed with water, and dried. After the fine powder filler subjected to homogeneous surface oxidation in this way was put into a mixer, 220 parts by weight of a furan resin initial condensate (residual carbon ratio: 47 parts) was added as a binder to 100 parts by weight of the filler. The mixture was stirred and kneaded for hours.

Next, the mixed wire was filled into a mold with a width of 550mm, and hot-pressure molding was carried out under the conditions of a heating temperature of 180°C and a load pressure of 500L9/1tit.

After firing the plate-shaped molded body in a lead hammer furnace in the same manner as in Example 1, it was further transferred to a graphitization furnace and graphitized at 2800°C.

B: The carbonaceous material processed by J has a strong and dense structure with no cracks or cavities, and has an apparent specific gravity of 1.87 f/crd.
Electrical specific resistance 720 μΩα, bending strength 610 Kg/c
It had heat-resistant and impermeable properties with a gas permeability of 0.00 CC/min.

Patent applicant Masaya Takahata, patent attorney representing Tokai Carbon Co., Ltd. (procedural amendment (spontaneous) July 20, 1980 Manabu Shiga, Commissioner of the Patent Office!, Indication of the case 1988 Patent Application No. 136767 2) Title of the invention: Process for producing heat-resistant impermeable carbonaceous material 3; Relationship with the amended case Patent applicant: 2-3 Higashi Kita-Aoyama-chome, Minato-ku, Tokyo / h Carhon Co., Ltd. President and Director Kunibe Ito 1 Agent 2-3 Kita-Aoyama-chome, Minato-ku, Tokyo (Hill as mentioned above) Column 3 of "Detailed Description of the Invention" of the Specification Contents of the amendment As shown in the attached sheet (1) 5 lines from the bottom of page 1 of the specification Correct "1 heat resistance" to "1 heat resistance" of eyes.

that's all

Claims (1)

[Claims] l. Filler is coke or fine graphite powder with a particle size of 100 mesh or less, which has been homogeneously surface oxidized in advance, and an initial condensate of a thermosetting resin having a residual carbon content of at least 40 mm is added and kneaded, followed by heating. 1. A method for producing a heat-resistant and impermeable carbonaceous material, which comprises pressure-molding and then firing the molded product in an inert atmosphere.