JPH05310471A - Production of impenetrative carbonaceous plate - Google Patents

Abstract

PURPOSE:To obtain a carbonaceous plate excellent in impenetrativeness, material strength and corrosion resistance by putting a primary form comprising carbonaceous powder and a thermosetting resin on a heated flat plate to make the form into a plate and by curing this plate under pressure followed by baking. CONSTITUTION:Firstly, a feedstock component comprising carbonaceous powder and a thermosetting resin is kneaded under a vacuum to make a primary forming. Second, the resulting primary form is put on a flat plate kept at 80-200 deg.C, followed by repeating pressurizing/depressurizing cycle to make the form into a plate. Then, the plate is made to descend under a pressure of 20-250 kgf/cm<2> and carbonized under baking in a nonoxidative atmosphere. For the extent of depressurization, lowering of the resultant pressure level to a level lower than that just before pressurization is enough; however, for the purpose of the effective proceeding of reaction by-product volatilization, it is desirable that the resulting pressure level on depressurization be regulated to <=0.5 based on 1 of the level just before pressurization (pref. 0kgf/cm<2> or so).

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 an impermeable carbonaceous plate suitable for use as a separator member for fuel cells and chlorine-zinc secondary batteries.

[0002]

2. Description of the Related Art Carbonaceous plates having a high degree of impermeability to gases and liquids and, at the same time, excellent corrosion resistance and conductivity are useful as separator members for fuel cells, particularly phosphoric acid fuel cells. Although various processes have been proposed in the past for the production technology of the impermeable carbonaceous plate intended for the separator member, practically, it is thermosetting so that the matrix part is finally converted into glassy carbon. The method of using a hydrophilic resin as a raw material component is excellent.

For example, as a manufacturing technique of this type, a kneaded product of a thermosetting resin prepolymer and a carbonaceous filler is molded into a plate, and the molded plates are laminated in multiple stages with a mold-releasing material of a resin sheet interposed therebetween. Heating at 100 ° C for 10 hours or more, and heating at 150 to 200 ° C for 1 to 10 kgf /
a step of treating for 1 to 30 minutes while applying a pressure of cm ³ ;
A method comprising a step of heating at 180 to 300 ° C for 5 hours or more and then firing and carbonizing in a non-oxidizing atmosphere (Japanese Patent Publication No. 3-35).
No. 262) or a method in which cellulosic paper impregnated with a thermosetting resin is laminated and pressure-bonded, and then cured and fired (Japanese Patent Laid-Open No. Sho 62-242, No.
No. 60-161144) is known.

However, each of the above methods has problems. That is, according to the former method, since the material is carbon powder / glassy carbon composite material, it is satisfactory in terms of material properties such as high strength, high corrosion resistance and low electrical resistance required for the fuel cell separator. In addition to the complicated molding and curing steps, it takes a long time to manufacture, and the manufacturing cost rises. On the other hand, the latter method does not have the drawbacks in terms of the manufacturing process like the former because the manufacturing process is relatively simple, but the material to be manufactured is substantially glassy carbon alone, There is a problem in terms of material that electrical resistance is high, fracture toughness is low, and the characteristics required as a fuel cell separator are not satisfied.

[0005]

As described above, in the prior art for producing an impermeable carbonaceous plate using a thermosetting resin as a raw material component, either the manufacturing process or the product material is solved. There are remaining issues to be solved.

In view of such circumstances, the inventors of the present invention have conducted intensive research focusing on the steps of plate molding and curing treatment in the case of using a thermosetting resin as a raw material component, and as a result, have led to the development of the present invention. The purpose is to obtain an impermeable carbonaceous plate satisfying the material characteristics required for a separator member for a fuel cell or a chlorine-zinc secondary battery with high productivity through a relatively simple process. It is to provide a manufacturing method of.

[0007]

In order to achieve the above object, the method for producing an impermeable carbonaceous plate according to the present invention comprises kneading a carbonaceous powder and a raw material component mainly composed of a thermosetting resin under vacuum. 80-
Place on a flat plate kept at 200 ° C, repeat the pressurization and depressurization cycle to form a plate, and then 20 to 250 kg.
The structural feature is that the plate is cured under a pressure of f / cm ² and then calcined and carbonized in a non-oxidizing atmosphere.

Among the raw material components of the present invention, carbonaceous powder serves as a filler, and powder of coke, graphite, glassy carbon or carbon black is used. These carbonaceous powders are preferably used as fine powders having an average particle size of 50 μm or less. Examples of the thermosetting resin include phenol resins, xylene resins, furan resins, polyimide resins and the like, which have a high carbonization rate and are converted into glassy carbon by a firing carbonization treatment, and powders and / or liquids in a prepolymer state. Applied as.
The raw material components of the present invention are mainly composed of these carbonaceous powders and thermosetting resins, but in addition to these, additives such as kneading aids and molding aids can be added as necessary. These additives are preferably organic substances that volatilize in the firing and carbonization step, for example, methyl cellulose, carboxymethyl cellulose, sodium lignin sulfonate and the like as a kneading aid, and higher alcohols such as glycerin as a molding aid are suitable. Used for. The mixing ratio of the raw material components is determined by the target characteristics of the material to be obtained, but the mixing ratio of the main raw material is preferably in the range of 50 to 200 parts by weight with respect to 100 parts by weight of the carbonaceous powder.

These raw material components are subjected to a kneading treatment in a vacuum and primary molding into an appropriate shape. As process conditions,
It is preferable to set the degree of vacuum to 100 Torr or less and set the temperature to 30 to 100 ° C. In this process, kneading and molding can be performed separately, but using a kneading and molding machine with an integrated kneading mechanism and molding mechanism improves work efficiency and effectively degass mixed gas components. As a result, the material characteristics can be improved. The processing means suitable for the purpose of the present invention is a kneading extrusion molding apparatus having a structure including a kneading section consisting of a twin screw, a vacuum deaeration chamber and a molding section of a single screw, and the raw material components kneaded in advance are added. Then, the kneading and the extrusion molding are continuously performed. In the step, the carbonaceous powder filler and the thermosetting resin prepolymer are uniformly dispersed in the kneading step, and at the same time, the resin serves as a binder to sufficiently wet the filler, and in the molding step, it is contained in the air and raw materials mixed during kneading. The volatile components are smoothly removed.

The obtained primary compact is placed on a flat plate kept at 80 to 200 ° C., and a cycle of pressurization and pressure reduction is repeated to form a plate. This process is a stage to densify the material by repeating plate formation by pressurization and removal of reaction by-products by pressure reduction. If the holding temperature of the flat plate is less than 80 ° C, the softening of the resin component becomes insufficient,
If the temperature exceeds 200 ° C., the curing reaction of the resin will proceed too rapidly, making smooth plate molding difficult. The pressurization / depressurization cycle is repeated at least twice, preferably 3 to 5 times. The pressure at the time of pressurization is set in consideration of the temperature of the flat plate, the fluidity of the primary forming body, etc., but usually 10 to 2
It is adjusted within the range of 50 kgf / cm ² . It is sufficient to lower the pressure lower than the pressure applied, but in order to promote the volatilization of reaction by-products, the pressure is adjusted to 1 or less and 0.5 or less. It is desirable to do.
A suitable pressure for pressure reduction is 0 kgf / cm ² or a range close to it.

Then, the plate on the flat plate is placed on the plate 20-25.
It is cured while applying a pressure of 0 kgf / cm ² . The plate is cured under pressure so that the entire cured state becomes uniform and the strain due to the difference in heat shrinkage during carbonization is eliminated, so that it is possible to prevent the phenomenon such as deformation and cracking during firing and carbonization in the subsequent step. .. The plate after pressure curing is heated to a temperature range of 150 to 300 ° C. as necessary to complete curing.

The above-mentioned plate molding and hardening treatment steps are usually carried out by using a pressing device having a heating plate as a flat plate. However, in order to prevent the phenomenon that the primary molded body is fused to the heating plate, heat treatment is performed. A silicone or fluorine release agent is applied to the board surface in advance, or a release sheet made of polyethylene, polypropylene, polyfluoroethylene, etc. or release paper coated with these resin components is applied between the primary molding and the hot plate. It is preferable to lay it on. Also, if a spacer with a predetermined dimensional accuracy is attached to the hot platen,
It is effective for ensuring the accuracy of plate thickness.

The cured plate molded body is subjected to firing carbonization treatment in a non-oxidizing atmosphere to convert the resin component into glassy carbon. The firing carbonization temperature is usually 800 to
Although the temperature is 2000 ° C., the material can be graphitized by heating to 2000 ° C. or higher if necessary. A lead hammer furnace, gas replacement furnace, etc. are used for the treatment, and the plate molded body is covered with a packing material such as coke powder to block oxygen, or the inside of the furnace is replaced with an inert gas such as nitrogen or argon. It is done in the state where it did.

[0014]

According to the process of the present invention, first of all, the raw material components are sufficiently kneaded in the steps of kneading the raw material components under vacuum and the primary molding process, and at the same time, air and volatile gas components contained in the raw materials are removed. , The material becomes more compact. The dense primary molded product is formed into a plate by softening the molded product by pressurization in the repeated process of pressurizing and depressurizing cycles on the subsequent flat plate. At this time, the resin component rapidly hardens to generate a large amount of reaction by-products such as water, which makes the tissue porous,
In the next step of reducing the pressure, reaction by-products are smoothly removed from the tissue by volatilization. Therefore, in the process of repeating the pressurization / depressurization cycle, the tissue is further compacted and formed into a plate shape. Then, since the plate is cured under pressure to obtain a uniform cured state without distortion, a normal carbonaceous plate is manufactured without deformation or cracking phenomenon in the final firing carbonization treatment.

Due to the synergistic effects of the respective steps, the carbon powder / glassy carbon composite structure is formed through the molding / curing process which is simplified as compared with the prior art, and the excellent impermeability, A carbonaceous plate having material strength and corrosion resistance can be manufactured with high productivity.

[0016]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 3 100 parts by weight of graphite fine powder having an average particle diameter of 12 μm was used as a powdery phenol resin in a prepolymer state [Sumitomo Dures Co., Ltd.].
Manufactured by PR311] and mixed for 5 minutes using a V-type mixer. Liquid phenol resin prepolymer [PR940] manufactured by Sumitomo Dures Co., Ltd. was added to this mixture.
After mixing parts by weight and pre-kneading with a kneader having a Z-type kneading blade, this is put into a kneading extrusion molding device having a structure in which the kneading part and the molding part are integrated via a vacuum deaeration chamber. The mixture was kneaded and extruded under the conditions of a temperature of 40 ° C. and a vacuum degree of 50 Torr for primary molding.

The obtained primary molded body was placed on a heating plate (flat plate) of a press machine on which a Teflon sheet was laid, and a pressurizing / pressurizing cycle was repeated three times by a plunger to form a plate. Then, the plate was cured while being pressurized to 100 kgf / cm ² to obtain a plate molded body having a length and width of 850 mm and a thickness of 1 mm. This plate molded body is heated at 180 ° C with an electric dryer.
After heating to complete the curing, put it in an electric furnace with both sides sandwiched by graphite plates, wrap the surrounding area with coke powder, and heat to 1300 ° C at a heating rate of 20 ° C / hour. A firing carbonization process was performed. The produced carbonaceous plate had a dense structure with no deformation or cracks.
Various properties of this impermeable carbonaceous plate were measured, and the results are shown in Table 1 in comparison with the conditions of kneading molding and pressurization / pressurization cycle.

Comparative Example 1 Kneading and molding were carried out under normal pressure, and the pressurization / reduction cycle conditions were 80 kgf / cm ² when pressure was applied and 40 kgf / cm when pressure was decreased.
^A carbonaceous plate was produced under the same conditions as in Example except that the number was changed to 2. The obtained carbonaceous plate had a rough surface structure. The various characteristics are also listed in Table 1 in comparison with the manufacturing conditions.

Comparative Example 2 A primary fired body, which was kneaded and molded under vacuum under the same conditions as in Example, was directly subjected to a pressure / pressure reduction cycle treatment of 100 kg.
A carbonaceous plate was manufactured by curing under pressure of f / cm ² under the same conditions as in Example. It was confirmed that the texture of the obtained carbonaceous plate had numerous holes. The various characteristics are also listed in Table 1 in comparison with the manufacturing conditions.

[0021]

[Table 1]

From the results shown in Table 1, it is recognized that in the examples satisfying the requirements of the present invention, a carbonaceous plate having high density, excellent strength, gas impermeability and low electric resistance can be obtained. Particularly, good results were obtained under the condition that the pressure reduction pressure during the pressure / pressure reduction cycle was 0 kg / cm ² . On the other hand, in Comparative Example 1 in which the kneading / molding step was performed under normal pressure and Comparative Example 2 in which the pressurizing / decreasing cycle was not applied to the molding / curing step, the characteristics were significantly deteriorated.

[0023]

As described above, according to the present invention, due to the manufacturing process simplified as compared with the prior art, the structure is dense, high strength, high corrosion resistance, low electrical resistance and excellent quality are obtained. A permeable carbonaceous plate can be manufactured. Therefore, it is useful as a manufacturing technique for various carbon members such as separator members for fuel cells and chlorine-zinc based secondary batteries, which are required to have a dense structure and impermeability.

Claims (2)

[Claims] 1. A raw material component mainly composed of carbonaceous powder and a thermosetting resin is kneaded in a vacuum for primary molding, and the primary molded body is placed on a flat plate kept at 80 to 200 ° C. Repeated pressurization and depressurization cycle to plate, then 20
A method for producing an impermeable carbonaceous plate, which comprises curing the plate under a pressure of ˜250 kgf / cm ² , and then subjecting the plate to firing carbonization in a non-oxidizing atmosphere. 2. The impermeable carbonaceous plate according to claim 1, wherein the pressure ratio during the pressurization / reducing cycle is set such that the pressure during depressurization is 0.5 or less with respect to the pressure during pressurization of 1. Production method.