JPH0223505B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel method for manufacturing porous carbon plates. More specifically, by impregnating a sheet obtained by the papermaking method with resin and then firing it, a sheet with excellent chemical resistance, electrical conductivity, and strength is produced.
The present invention relates to a method for manufacturing bulky and thick porous carbon plates. BACKGROUND ART Conventionally, as a method for obtaining carbon fiber sheets, carbon fiber mixed paper is known, in which carbon fibers that have been fired in advance are made into paper together with pulp and a binder. However, such mixed paper has a relatively high electrical resistance value and lacks chemical resistance, making it unsuitable for applications such as electrode base materials for fuel cells. As a method for improving these properties, a method is known in which the mixed paper is impregnated with a solution of a thermosetting resin and carbonized by firing it again in an inert atmosphere.
In this method, organic substances such as pulp are carbonized by heat treatment, so fiber paper with low electrical resistance and improved chemical resistance can be obtained. However, since the carbon fibers themselves have a high modulus of elasticity, the contact portions of the fibers are not bonded together sufficiently, making it difficult to obtain carbon fiber paper with sufficiently low electrical resistance. Further, since carbon fiber has a high specific gravity, it is difficult to obtain a bulky porous plate, and it is difficult to control the bulk density and pore diameter to suit various uses.
Moreover, since two firing steps are required, it has the disadvantage of being extremely expensive, and there has been a desire to develop an inexpensive manufacturing method (Japanese Patent Publication No. 18603/1983). The present inventors previously invented a manufacturing method using a papermaking method (see Japanese Patent Application Laid-Open No. 144625/1983), but since this method uses binder fibers like the above method, a porous sheet can be obtained. It had the disadvantage of being difficult to deal with. Furthermore, the method described in JP-A-59-144625 had the disadvantage that the electrical resistance of the sheet obtained after firing was also high. Problems to be Solved by the Invention It is an object of the present invention to improve the above-mentioned drawbacks and to provide a method for producing an inexpensive, high-quality (particularly excellent electrical conductivity) porous carbon plate. Means for Solving the Problems The invention proposed herein is as follows: (1) A sheet obtained by making paper from 65 to 90% by weight of organic fibers for carbon fiber production and 10 to 35% by weight of pulp,
Impregnate with an organic polymer solution in which carbonaceous powder is suspended to obtain a sheet in which the original sheet is mixed and impregnated with 5 to 40% of carbon powder and 20 to 160% of polymer material,
After drying the impregnated sheet, it is dried in an inert gas atmosphere.
A method for producing a porous carbon plate characterized by carbonizing it by firing at a temperature of 800°C or higher, and (2) a method for producing a porous carbon plate, which is obtained by making a paper using 65 to 90% by weight of organic fibers for carbon fiber production and 10 to 35 parts by weight of pulp. on the sheet
Impregnate with an organic polymer solution in which carbonaceous powder is suspended to obtain a sheet in which the original sheet is mixed and impregnated with 5 to 40% of carbon powder and 20 to 160% of polymer material,
This method of producing a porous carbon plate is characterized in that after drying the impregnated sheet, it is hot pressed to shape and harden, and then fired and carbonized at a temperature of 800° C. or higher in an inert gas atmosphere. In the above methods (1) and (2), the impregnated sheet is
After drying, molding and curing treatment may be performed together by heating and pressing alone or by laminating a plurality of sheets. Components of the present invention will be explained in detail below. (Organic fibers) The organic fibers used in the present invention may be any organic fibers commonly used in producing carbon fibers, such as rayon, pitch fibers, lignin fibers, phenol resin fibers, and acrylic fibers. Organic fibers having a length of 0.5 to 15 deniers and a length of 1 to 15 mm are used, but from the viewpoint of paper-making properties, it is preferable to use organic fibers of 0.5 to 8 deniers and a length of 1.5 to 10 mm depending on the purpose. They are selected and used alone or in combination of two or more. (Pulp) Since the above organic fibers have weak hydrophilicity, they cannot be used alone to make paper. Therefore, pulp is added as a binder to improve paper-making properties. As the pulp used in this invention, in addition to cellulose pulp, various synthetic pulps made of synthetic resins are suitable. (Ratio of organic fiber to pulp) The ratio of organic fiber to pulp is 65 to
90% by weight and pulp in a proportion of 10 to 35% by weight (as solid content), and paper may be made by a conventional method. When the organic fiber content is less than 65% by weight, it becomes difficult to control pore diameter, porosity, etc., while when the organic fiber content is more than 90% by weight, it is difficult to form a good sheet during paper making. If the pulp is less than 10% by weight, papermaking will be poor;
It becomes difficult to form a sheet, and if it exceeds 35% by weight, a bulky sheet cannot be obtained. Preferred ranges are 75 to 90% by weight of organic fibers and 10 to 25% by weight of pulp. (Carbonaceous powder) The carbonaceous powder used for impregnating paper sheets has a particle size of 0.1 to 40 μm, preferably 0.5 μm.
~10 μm graphite or carbon black is used. (Organic polymer substances) Examples of organic polymer substances used to impregnate paper sheets include phenolic resins, epoxy resins, unsaturated polyester resins, thermosetting resins such as polydivinylbenzene, vinyl chloride resins, and chloride resins. vinylidene resin, vinyl fluoride resin,
Thermoplastic resins such as vinylidene fluoride resins and acrylic resins, as well as lignin, pitch, or tar, are also used. The desirable properties of these polymer compounds are that they dissolve in some kind of solution or melt at high temperatures during heat treatment, and that they have a carbon content of 30% by weight or more and can be used as a carbonaceous binder in carbon fibers after carbonization. It is useful for the combination of As a polymer compound having such properties, a thermosetting resin is preferable. (Mixed Impregnation Treatment) As the second stage treatment of the present invention, a mixed paper is impregnated with a solution or dispersion of the carbonaceous powder and organic polymer substance. If the amount of impregnation that adheres to the mixed paper in this process is too small, the binder effect and carbonization yield during carbonization will be poor, and if the amount of impregnation is too excessive, it will be difficult to adjust the porosity due to clogging, and furthermore, the final The product, the porous carbon plate, becomes brittle.
The preferred amount of impregnation is 5 to 40% by weight of the carbonaceous powder, 20 to 160% by weight of the organic polymer substance, and more preferably 5 to 40% by weight of the carbonaceous powder based on the weight of the mixed paper.
15-30% by weight, 60-120% by weight of organic polymeric substances
It is. (Heat Press Treatment) In the second method of the present invention, a hot press treatment is performed subsequent to the second step. Press molding is performed to provide the final product, the porous carbon plate, with the required thickness, shape, porosity, and pore size. In this case, the appropriate press heating conditions for curing the resin in the impregnated sheet by using heat treatment together are 150 to 220° C. for 1 to 60 minutes. This curing treatment made it possible to maintain a constant sheet thickness and at the same time obtain a flat sheet. Furthermore, by adjusting the press pressure, the porosity and pore diameter of the carbon plate can be changed arbitrarily. (Lamination hot press treatment) During the above press treatment, a thick carbon plate can be easily obtained by stacking a required number of thin impregnated sheets and performing the press treatment in the same manner. Lamination of porous sheets, which are prone to delamination and difficult to manufacture using conventional methods, is made possible by the present invention using press lamination and curing methods. When stacking impregnated sheets, if the sheets are stacked alternately in the vertical and horizontal directions, the sheets will have no directionality and a carbon plate with a uniform thickness and no cracks will be obtained. (Calcination Treatment) After drying or hot pressing, the impregnated sheet is heated and fired at a temperature of 800° C. or higher in an inert gas atmosphere to obtain the porous carbon plate of the present invention. (Others) In the present invention, the following chemicals may be used or the treatment steps may be performed as necessary. [Paper strength enhancer] Since the sheet obtained by the present invention is made from organic fibers and pulp, a bulky sheet can be obtained, but if the strength of the paper sheet is required, it is usually used in paper making. A small amount of paper strength enhancer may be added. The paper strength enhancer is preferably water-soluble, such as cationized starch, cationized or anionized polyacrylamide, melamine resin, urea resin, epoxidized polyamide resin, carboxy-modified polyvinyl alcohol, etc. Any resin used can be used. [Heat resistance improver] When using regenerated cellulose, such as rayon, as the organic fiber, in addition to the above-mentioned mixed impregnation treatment of carbonaceous powder and organic polymer, impregnation treatment with a heat resistance improver can be used to improve carbonization. It brings about good effects in terms of rate, strength, etc. As the heat resistance improver, any of those commonly used in producing rayon carbon fibers can be used. For example, as a metal phosphate salt,
Magnesium monophosphate, calcium monophosphate, sodium monophosphate, potassium monophosphate, etc., and as ammonium salts of various acids, ammonium chloride, ammonium sulfate, ammonium hydrogen sulfate, ammonium phosphate, hydrogen phosphate, etc. Ammonium, ammonium dihydrogen phosphate, ammonium salt of polyphosphoric acid, ammonium borate, etc. can be suitably used. [Precuring Treatment] In the present invention, the impregnated sheet may be subjected to a preliminary curing treatment before the press treatment. When precuring is performed, the organic polymeric substance within the sheet no longer flows, so that a uniform pressing process is performed. The pre-curing processing conditions are 105℃~ without complete curing.
180°C and about 1 minute to 30 minutes are suitable. [Stabilization Treatment] The impregnated sheet or the sheet that has undergone hot press treatment may be subjected to stabilization treatment prior to firing, if necessary. The stabilization treatment is performed to improve the carbonization yield of the organic fibers after the heating carbonization step. This is particularly effective when the organic fiber is acrylic fiber or pitch fiber. Stabilization treatment conditions do not need to be specifically defined, but preferably 150 to 350°C for several tens of minutes.
The treatment is carried out in air for a period of 10-odd hours, depending on the type of organic fiber used. EXAMPLES In order to facilitate understanding of the present invention, examples are provided below, but the following examples are not intended to limit the present invention. In addition, parts and % in the examples are parts by weight and % by weight, respectively. Examples 1 to 3 and Comparative Example 55 parts and 25 parts of acrylic fibers with a thickness of 7 denier and a length of 3 mm, and a thickness of 3 denier and a length of 3 mm, respectively.
A slurry was prepared by adding water to 20 parts of 400 ml of Canadian Freeness pulp (NBKP), and a sheet having a basis weight of 180 g/m ² was made using a conventional method using a circular paper machine. The above sheet was immersed in a solution consisting of carbon powder, a polymeric substance, and methanol. The carbon powder in the solution is graphite with a particle size of 6 μm,
The blending ratio is 0%, 15%, 30% of the weight of mixed paper
or 20% carbon black with a particle size of 3μm
It was a combination. In addition, the polymer substance is phenolic resin PL-2215 manufactured by Gunei Chemical Co., Ltd.
80% of the weight of the mixed paper was used. After the impregnation with the methanol solution was completed, the sheet was dried in a drying chamber at a temperature of 105°C. Next, six of the sheets were laminated and pressed using a press so that the thickness became 3.0 mm, and at the same time heat treatment was performed at a temperature of 180° C. for 15 minutes. Next, heat stabilization treatment was performed at 220℃ for 4 hours in air, and then at 1000℃.
The sample was heated and carbonized by sandwiching it between graphite plates for 1 hour in a nitrogen gas atmosphere. Example 4 55 parts and 25 parts of acrylic fibers with a thickness of 7 denier and a length of 3 mm, and a thickness of 3 denier and a length of 3 mm, respectively.
A slurry was prepared by adding water to 20 parts of Canadian Freeness 400 ml pulp (NBKP), and a sheet having a basis weight of 180 g/m ² was made using a circular wire paper machine using a conventional method. The above sheet was immersed in a solution consisting of carbon powder, a polymeric substance, and methanol. The carbon powder in the solution was graphite with a particle size of 6 μm, and the blending ratio was 30% of the weight of the mixed paper. In addition, the polymer material is Gunei Chemical Company's phenolic resin PL-
2215, and the blending ratio was 80% of the weight of the mixed paper. After completion of impregnation, the sheet was dried at a temperature of 105°C. Next, press only one sheet without stacking the above sheets so that the thickness becomes 0.5 mm,
At the same time, heat treatment was performed at 180°C for 15 minutes. then
After heat stabilization treatment in air at 220℃ for 4 hours, it was stabilized in a nitrogen gas atmosphere at 1000℃ for 1 hour.
It was heated and carbonized by sandwiching it between graphite plates. Example 5 55 parts and 25 parts of acrylic fibers with a thickness of 7 denier and a length of 3 mm, and a thickness of 3 denier and a length of 3 mm, respectively.
A slurry was prepared by adding water to 20 parts of Canadian Freeness 400 ml pulp (NBKP), and a sheet having a basis weight of 180 g/m ² was made using a circular wire paper machine using a conventional method. The above sheet was immersed in a solution consisting of carbon powder, a polymeric substance, and methanol. The carbon powder in the solution was graphite with a particle size of 6 μm, and the blending ratio was 30% of the weight of the mixed paper. In addition, the polymer material is Gunei Chemical Co., Ltd.'s phenolic resin PL.
−2215, and the blending ratio is 80% of the weight of the mixed paper
It was hot. After completion of impregnation, the sheet was dried at a temperature of 105°C. Next, the above sheets were heat stabilized in air at 220℃ for 4 hours without stacking or pressing, and then heated in a nitrogen gas atmosphere at 1000℃ for 1 hour.
The material was heated and carbonized by sandwiching it between graphite plates for a period of time. The physical properties of the sheets of Examples 1 to 5 and Comparative Example were
Shown in the table.

[Table] Effects of the Invention The first feature of the present invention is that carbon powder with good electrical conductivity is mixed with an organic polymer substance to form a solution.
Since the mixed paper is impregnated with this, the electrical conductivity of the sheet after firing is very good. The second feature is that the original sheet can be made using a normal wet paper machine, improving productivity and making it possible to obtain sheets at low cost. The third feature is that the raw material composition of the present invention has better paper-making properties than carbon fiber, so it is easy to obtain uniform and flat sheets, and furthermore, it has the advantage of being able to obtain any sheet weight. . The fourth feature is that it has become possible to manufacture porous carbon plates of any thickness by laminating thin sheets and pressing them. The fifth feature is that the pore size and porosity of the plate, which are problems when used as an electrode base material for fuel cells, can be freely and easily controlled by selecting the thickness of the raw material fiber, adjusting the blend, and press treatment. It has become possible to do so.

Claims (1)

[Scope of Claims] 1. A sheet obtained by making paper from 65 to 90% by weight of organic fibers for manufacturing carbon fibers and 10 to 35% by weight of pulp is impregnated with an organic polymer solution in which carbonaceous powder is suspended,
After obtaining a sheet that is mixed and impregnated with 5 to 40% by weight of carbonaceous powder and 20 to 160% by weight of polymeric material based on the original sheet, the impregnated sheet is dried and heated to 800℃ or higher in an inert gas atmosphere. A method for producing a porous carbon plate, characterized by carbonizing it by firing at a high temperature. 2. A sheet obtained by making paper from 65 to 90% by weight of organic fibers for carbon fiber production and 10 to 35% by weight of pulp is impregnated with an organic polymer solution in which carbonaceous powder is suspended,
After obtaining a sheet impregnated with a mixture of 5 to 40% by weight of carbonaceous powder and 20 to 160% by weight of polymeric material based on the original sheet, the impregnated sheet is dried, heated and pressed to form and harden, and then A method for producing a porous carbon plate, characterized by carbonizing it by firing at a temperature of 800°C or higher in an inert gas atmosphere. 3. Claim 2, characterized in that two or more impregnated sheets are laminated and subjected to hot press treatment.
The method for producing a porous carbon plate as described in 2.