JPH0335262B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing an impermeable carbon plate useful for separators of fuel cells, chlorine-zinc secondary batteries, and the like. [Prior Art] Carbon plates, which have excellent gas and liquid impermeability, also have excellent electrical properties, and are therefore suitable as separators for fuel cells, particularly phosphoric acid fuel cells. Conventionally, this impermeable carbon plate has been produced by preforming a kneaded mixture of carbon filler and thermosetting prepolymer, then forming it into a plate shape using methods such as roll rolling, and then hardening and firing. was. However, in the above method, after forming into a plate shape, the material must be hardened during processing, and this process usually takes a long time, posing problems in mass production. Furthermore, in order to increase the throughput in a single pressure curing process, if uncured plates are stacked in multiple stages and the curing process is performed, the plate thickness accuracy will decrease due to uneven pressure distribution and uneven temperature distribution. There was a problem. [Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and solves the above-mentioned problems, that is, improves the productivity of impermeable carbon plates and makes it possible to improve thickness accuracy. The purpose of the present invention is to provide a new manufacturing method. [Means for Solving the Problems] The present inventor has conducted extensive research in order to solve the above problems, and found that carrying out the curing reaction of thermosetting resin in stages improves productivity and accuracy. The present inventors have discovered that it is effective in improving That is, the present invention uses a kneaded product containing at least a thermosetting resin prepolymer and a carbonaceous filler,
Manufacture of an impermeable carbon plate characterized by forming plates, stacking them in multiple stages, then subjecting the stacked plates to multi-stage hardening treatment, and carbonizing and firing the plates after hardening in a non-oxidizing atmosphere. It's a method. The thermosetting resin prepolymer used in the present invention may be any of those known to be usable in the production of conventional impermeable carbon plates, such as phenolic resins, xylene resins, furan resins, etc. Examples include prepolymers of thermosetting resins such as resins, urea resins, melamine resins, aniline resins, epoxy resins, and unsaturated polyester resins. Further, as the carbonaceous filler in the present invention, carbonaceous powders such as coke powder, graphite powder, glassy carbon powder, and carbon black are used. The resin kneaded product of the present invention contains at least the above-mentioned resin prepoly and carbonaceous filler, but other additives may be blended as kneading and molding aids, etc., as necessary. Such additives are preferably those that can be decomposed and volatilized during the carbonization firing process, such as methylcellulose, carboxymethylcellulose, carboxymethylstarch, hydroxyethylcellulose, hydroxypropylcellulose, sodium ligninsulfonate, calcium ligninsulfonate, polyvinyl Alcohol, polyacrylic ester, polymethacrylic ester, guar gum, alginate,
These include paraffin oxide and calcium stearate. The resin kneaded material can be prepared from a thermosetting resin prepolymer, a carbonaceous filler, and other necessary additives using a known method and kneading device. The resin kneaded material is preformed using a mold or an extrusion molding machine, and then rolled into an uncured plate-shaped molded product. Next, the plates are stacked in multiple stages and a curing process begins, with a releasable material interposed between the plates so that the stacked plates do not stick to each other. As such a releasable material, a resin sheet such as polyethylene, polypropylene, polytetrafluoroethylene, etc. is preferably used. In the present invention, the curing reaction of the plate is not completed in one step, but is carried out in stages. First, the material formed into a plate shape is heated to 50 to 100℃.
When treated at a temperature of 10 hours or more, the binder resin undergoes a mild polycondensation reaction, making it possible to form a homogeneous structure without forming large local pores inside the material. Moreover, at this time, the thickness accuracy ensured during molding can be maintained without deterioration. Furthermore, polycondensation reaction by-products can be dissipated in this step. Next, the mixture is heated at 150 to 200°C and subjected to a pressure of 1 to 10 kg/cm ² for 1 to 30 minutes. If this step is carried out without the above steps, many bubbles and holes will be generated in the plate. In addition, dimensional accuracy also decreases. In this step, in addition to correcting the slight surface waviness generated in the previous step, it also has the effect of uniformizing the hardening state within the plate. If the cured state is non-uniform, localized blistering may occur during the firing process. The molded product cured in this way has a further 180~
Hardening is completed by heat treatment at a temperature of 300°C for 5 hours or more. With conventional technology, the work hardening process takes 10 to 50 hours or more, and the productivity is low, with the amount of processing being about 1 to 3 sheets at a time, and in order to increase the processing amount, it is necessary to stack 4 or more sheets. Dimensional accuracy (thickness) also decreases. In the present invention, by carrying out the curing reaction in stages as described above, a homogeneous plate without generation of pores can be obtained, and the thickness accuracy thereof can also be significantly improved. As a result of improving thickness accuracy according to the present invention, it is possible to omit the processing step for ensuring thickness accuracy after the completion of the firing process, which will be described next, and furthermore, it is possible to omit the processing step for ensuring thickness accuracy after the completion of the firing process, which will be described next. It is possible to laminate the laminate into multiple layers, and it is possible to significantly reduce costs. The final step in the present invention is a carbonization firing step of the plate. After the hardening process, the plate is heated in a non-oxidizing atmosphere, such as a helium, argon, or nitrogen gas atmosphere, at a temperature of 1,000 to 2,000°C or more than 3,000°C in some cases.
Carbonized and fired at high temperatures up to ℃. This firing step itself can be carried out under known conditions. EXAMPLES The present invention will be explained in further detail by way of Examples below. [Example] 100 parts by weight of graphite fine powder (average particle size 4 μm), 48 parts by weight of powdered phenolic resin (PR11078 manufactured by Sumitomo Durez Co., Ltd.), and liquid phenolic resin (manufactured by Sumitomo Durez Co., Ltd.)
PR940) 52 parts by weight and 2 parts by weight of carboxymethylcellulose are mixed, kneaded in a kneader, and then extruded using a screw-type kneading extruder. In this case, the temperature of the kneaded material is 30-60
Keep at ℃. Extrusion molded products are made using a rolling machine.
It was formed into a plate shape of 800×80×1 ^tmm . The obtained uncured plates were sandwiched between aluminum plates with a polyethylene sheet interposed between them, and stacked in 20 layers in a hot air circulation oven. In the oven at 80℃
After treatment for 15 hours, a pressure of 2 kg/cm ² was applied using a hot press, and treatment was performed at 180°C for 5 minutes. Next, post-curing treatment is performed at 220° C. for 7 hours in the heating oven to complete curing of the plate. Furthermore, the plate is sandwiched between graphite plates in an electric furnace, and the surrounding area is covered with coke powder to create a non-oxidizing atmosphere inside the electric furnace, and then firing is performed at 8°C/hr to 1300°C. The fired plate was dense, had good thickness accuracy, and had high strength. For comparison, the manufacturing conditions were the same as above, but without pressure treatment in the intermediate process (Comparative Example 1), and when curing was performed using the conventional pressure curing method (Comparative Example 2). The results are shown in the table below together with the results of the present invention. In Comparative Example 2, plates formed by the same method as the present invention were stacked in three stages and treated using a press under a pressure of 7 kg/cm ² at 60°C for 50 hours, then at 80°C for 12 hours, and then at 220°C for 5 hours. Post-curing was performed.
Note that Comparative Example 2 was fired at a temperature increase rate of 5° C./hr.

[Table] [Effects of the Invention] As explained above, according to the present invention, it is possible to manufacture an impermeable carbon plate that is dense and has significantly superior thickness accuracy, and the productivity has also been improved compared to the conventional method. It can be greatly improved.

Claims (1)

[Claims] 1. Molding plates from a kneaded material containing at least a thermosetting resin prepolymer and a carbonaceous filler, stacking the plates in multiple stages via resin sheet releasable material, and then heating the stacked plates at 50 to 100°C.
A multi-stage curing process consisting of heating for 10 hours or more at 150-200℃ while applying a pressure of 1-10Kg/ ^cm2 for 1-30 minutes, and heating at 180-300℃ for 5 hours or more. 1. A method for producing an impermeable carbon plate, which comprises subjecting the plate to a treatment and then carbonizing the plate in a non-oxidizing atmosphere after hardening.