JPH08283084A - Production of porous carbon plate - Google Patents

Abstract

PURPOSE: To obtain a production method by which a porous carbon plate having a pore size gradient excellent in phosphoric acid electrolyte retention properties and gas permeability can be produced at a low cost through using a conventional paper-making method and an impregnation method. CONSTITUTION: In this production, at least two paperlike felted sheets having different bulk density from each other within the range of 0.1 to 0.5g/cm<3> are formed by using a mixture of 20 to 95 pts.wt. of organic fiber for producing carbon fiber and 5 to 80 pts.wt. of pulp. Then, these paperlike felled sheets are impregnated with an organic polymer material solution and thereafter, dried to form dried impregnated sheets. Subsequently, with the impregnated sheet formed from the felled sheet having the lowest bulk density and the impregnated sheet formed from the felled sheet having the highest bulk density as the outermost layers, the impregnated sheets are laminated in order of bulk density of the felted sheets from which they are formed, from lower to higher to form a laminate. The resulting laminate is successively subjected to hot-press treatment, oxidation treatment in air and heating and carbonization treatment in an inert gas atmosphere at >=800 deg.C to produce the objective porous carbon plate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel method for producing a porous carbon plate. More specifically, the organic fiber for producing carbon fiber and pulp are mixed to obtain an impregnated sheet from a papermaking sheet that is paper-made. The impregnated sheets are sequentially laminated, and after hot press treatment,
By carbonizing, a bulky and thick porous carbon plate having excellent chemical resistance, electrical conductivity, gas permeability and strength, in which the pore diameter changes in the thickness direction, is produced. It is about the method.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a porous carbon plate having a pore diameter gradient, there are two types of coarse or dense after firing because a coarse and dense two-layer structure is provided in JP-A-59-46763. There is known a porous carbon plate having a two-layer structure in which two sheets, a rough sheet and a dense sheet, are laminated before firing, press-formed, and fired. The present inventors disclosed a method by a wet papermaking method in Japanese Patent Laid-Open No. 61-195875, but this method can only obtain a porous plate having a two-layer structure, and has sufficient phosphoric acid electrolyte retention and gas. It was not possible to obtain a porous carbon plate that is permeable, lightweight and has high bending strength.

[0003]

DISCLOSURE OF THE INVENTION The present invention improves the phosphoric acid electrolyte retention and gas permeability which are the above-mentioned drawbacks, and at the same time, a porous carbon plate having a pore diameter gradient is usually used in a papermaking method. An object of the present invention is to provide a method for inexpensively producing a high-quality porous carbon plate having high electric conductivity and excellent chemical resistance by using the sheet forming equipment according to the above and the impregnating sheet forming equipment according to the impregnation method.

[0004]

The present invention has a fineness of 0.0
Using 1 to 30 denier and 20 to 95 parts by weight of organic fibers for producing carbon fibers having a fiber length of 0.2 to 15 mm, and 5 to 80 parts by weight of pulp, a tightness of 0.1 to 0.5 g / cm ³
In the range of, at least two types of papermaking sheets having different tenacity, a step of impregnating the papermaking sheet with a solution of an organic polymer substance, a step of producing a dried impregnated sheet, and a papermaking sheet having the lowest tenacity Between the impregnated sheet and the impregnated sheet prepared from the papermaking sheet having the highest tenacity, a step of laminating the impregnated sheets in the order of decreasing paperboard tenacity to prepare a laminated sheet, and subjecting the laminated sheet to a hot press treatment. After that, the method is characterized by including a step of forming a precursor sheet by oxidizing in air, and a step of heating and carbonizing the precursor sheet at a temperature of 800 ° C. or higher in an inert gas atmosphere. This is achieved by the method for manufacturing a porous carbon plate.

The organic fibers for producing carbon fibers used in the present invention include ordinary rayon fibers, pitch fibers, lignin fibers, phenol resin fibers, acrylic fibers, and other organic fibers used as a raw material when producing ordinary carbon fibers. And has a fineness of 0.01 to 30 denier, preferably 0.1
~ 15 denier and 0.2 ~ 15 m fiber length
m, preferably 0.5 to 5 mm, is selected according to the target tightness and used alone or in combination of two or more.

For the formation of a papermaking sheet, a paper stock obtained by mixing 60 to 95 parts by weight of organic fibers for producing carbon fibers and 5 to 40 parts by weight of pulp is used to make paper, circular nets, Fourdrinier, slanted wires, etc. An ordinary wet papermaking method can be used, and the papermaking concentration may be lowered to obtain a papermaking sheet having a good texture. When the strength of the wet paper sheet is weak after dehydration with a wire mesh,
By adding beaten natural pulp, strength is increased and wet paper sheet breakage can be prevented. Further, usually, the dewatering press treatment is performed in the wet papermaking process, but the dewatering press treatment may not be performed.

The multi-cylinder type used in ordinary wet paper machines,
In addition to the cylinder type dryer such as the Yankee type, a hot air type dryer such as a band dryer and a honeycomb dryer, an infrared type dryer and the like can be used.
When a hot-air dryer or an infrared dryer is used, the papermaking sheet becomes bulky and a papermaking sheet with low tenacity is obtained.

In the case of papermaking, when the tensile strength of the wet paper is weak, it is preferable to use a canvas or felt if necessary.

Examples of the organic polymer substance to be impregnated in the papermaking sheet include phenol resin, epoxy resin, unsaturated polyester resin, furan resin, thermosetting resin such as polydivinylbenzene, vinyl chloride resin, vinylidene chloride resin, Thermoplastic resins such as vinyl fluoride resin, vinylidene fluoride resin, acrylic resin, or such as lignin, pitch or tar are used.

The preferred properties of these organic polymeric substances are that they dissolve in an organic solvent or melt at a high temperature during heat treatment, and that they have a carbon content of 30% by weight or more, and have a carbonaceous binder after carbonization. As it contributes to the bond in the carbon fiber, a thermosetting resin is preferable.

A papermaking sheet is impregnated with the solution or dispersion of the above organic polymer to obtain an impregnated sheet. If the amount of impregnation adhered to the papermaking sheet is too small, the binder effect and the carbonization yield during carbonization will be poor, and if it is too much, it will cause clogging, making it difficult to adjust the porosity and making the porous carbon plate brittle. . The preferable impregnated adhesion amount is 20 to 160% by weight of the weight of the papermaking sheet.

The pore diameter obtained by the present invention is, for example, about 8 μm in the case of a porous carbon plate obtained from a papermaking sheet alone containing 80% by weight of an organic fiber having a fineness of 0.1 denier and 20% by weight of a natural pulp. A porous carbon plate obtained by using a papermaking sheet alone containing 80% by weight of an organic fiber having a fineness of 3 denier and 20% by weight of a natural pulp has a thickness of about 27 μm and 80% by weight of an organic fiber having a fineness of 10 denier. With a porous carbon plate obtained by using a papermaking sheet alone containing 20% by weight of natural pulp, the thickness is about 50 μm.

In order to impart a pore diameter gradient in the thickness direction of the porous carbon plate, an impregnated sheet made from the papermaking sheet having the lowest tenacity and an impregnated sheet made from the papermaking sheet having the highest tenacity are provided. , Laminating impregnated sheets in ascending order of papermaking sheet, make a laminated sheet, heat press, oxidize in air, heat carbonize in an inert gas atmosphere, and perforate with pore diameter gradient. Quality carbon plate.

The hot press treatment is carried out in order to impart a predetermined thickness, shape, density and pore diameter gradient in the thickness direction to the porous carbon plate.

In the porous carbon plate obtained as described above, the side obtained from the papermaking sheet having the smallest tenacity has the large pore diameter and the side obtained from the papermaking sheet having the greatest tenacity is
The pore diameter becomes smaller, and a pore diameter gradient is given in the thickness direction of the porous carbon plate.

The side of the porous carbon plate with the larger pore diameter is
The gas permeability is good, and the smaller pore size side has better phosphoric acid electrolyte retention, and is suitable for use as a carbon electrode on the separator side.

By the hot pressing and heat carbonization treatment, it became possible to keep the thickness of the porous carbon plate constant and at the same time obtain a flat porous carbon plate. Further, by adjusting the pressing pressure or the thickness of the spacer at the time of pressing, it is possible to arbitrarily change the thickness and the pore diameter of the entire porous carbon plate.

The heating conditions in the hot press treatment are 15
0-220 degreeC and 1-60 minutes are preferable. The laminated sheet that has been subjected to the hot press treatment is subjected to an oxidation treatment in air to improve the carbonization yield and the graphitization rate, and then carbonized at a temperature of 800 ° C. or higher in an inert gas atmosphere. The porous carbon plate of the invention is obtained.

Here, the oxidation treatment is performed after the hot pressing step, but the conditions of the oxidation treatment are not particularly limited.
It is suitable to treat in air at 50 to 350 ° C. for 10 minutes to 20 hours.

[0020]

EXAMPLES The constitution and effects of the present invention will be further described with reference to examples, but of course the present invention is not limited to these modes. In the examples, "parts" means "parts by weight". The apparent density of the porous carbon plate was measured by polishing the surface of the carbon plate, and the pore size in the depth direction was measured using a mercury porosimeter. Further, the bending test was measured by a three-point bending test method.

EXAMPLE A slurry consisting of 80 parts of polyacrylonitrile fiber having a fineness of 10 denier and a fiber length of 3 mm and beaten conifer bleached kraft pulp to a Canadian freeness of 250 ml to obtain 20 parts of slurry was prepared with a 250 mm square hand-making machine. A papermaking sheet having a basis weight of 200 g / m ² and a tenacity of 0.18 g / cm ³ is made by a method, and the papermaking sheet is made of a phenol resin (trademark: KP743 manufactured by Arakawa Chemical Industry Co., Ltd.), and the adhesion amount per papermaking sheet is 50. The impregnated sheet A is impregnated so that the content becomes%.

A slurry comprising 80 parts of polyacrylonitrile fiber having a fineness of 5 denier and a fiber length of 3 mm and beaten conifer bleached kraft pulp to 250 ml of Canadian freeness to obtain 20 parts of slurry was prepared by a conventional method with a 250 mm square hand-making machine. Basis weight 200g / m ² , tenacity 0.20
A papermaking sheet of g / cm ³ is produced, and the papermaking sheet is phenolic resin (trademark: KP743 manufactured by Arakawa Chemical Industry Co., Ltd.)
Then, impregnation is performed so that the amount of adhesion per paper making sheet becomes 50%, and this is used as impregnation sheet B.

A slurry consisting of 80 parts of polyacrylonitrile fiber having a fineness of 3 denier and a fiber length of 3 mm and 20 parts of bleached softwood kraft pulp with a Canadian freeness of 20 ml was obtained by a conventional method with a 250 mm square hand-making machine. Basis weight 200g / m ² , tenacity 0.22
A papermaking sheet of g / cm ³ is produced, and the papermaking sheet is phenolic resin (trademark: KP743 manufactured by Arakawa Chemical Industry Co., Ltd.)
Then, impregnation is performed so that the amount of adhesion per paper making sheet is 50%, and this is referred to as impregnation sheet C.

A slurry consisting of 80 parts of polyacrylonitrile fiber having a fineness of 0.5 denier and a fiber length of 3 mm and beaten conifer bleached kraft pulp to 250 ml of Canadian freeness to obtain 20 parts of slurry was prepared with a 250 mm square hand-making machine. According to the method, the basis weight is 200 g / m ² , the tenacity is 0.
A 25 g / cm ³ papermaking sheet is made into paper, and the papermaking sheet is impregnated with a phenolic resin (trademark: KP743 manufactured by Arakawa Chemical Industry Co., Ltd.) so that the adhered amount per papermaking sheet is 50%. And

Four sheets of the impregnated sheet A, four sheets of the impregnated sheet B, four sheets of the impregnated sheet C, and four sheets of the impregnated sheet D are sequentially laminated on each other to form a laminated sheet,
Heat-press at 180 ° C. for 15 minutes, then oxidize at 220 ° C. for 4 hours in air to prepare a precursor sheet.
It is sandwiched between graphitized carbon plates in a nitrogen gas atmosphere at 000 ° C. for 1 hour and heated, and then in an argon gas atmosphere, the temperature is set to 2
Graphitization was performed at 800 ° C. for 30 minutes to obtain a porous carbon plate.

Comparative Example 1 16 sheets of impregnated sheets A were sequentially laminated to form a laminated sheet, and then subjected to oxidation treatment and graphitization treatment under the same conditions as in Example 1 to obtain a porous carbon plate.

Comparative Example 2 Sixteen impregnated sheets C were sequentially laminated to form a laminated sheet, and then oxidation treatment and graphitization treatment were performed under the same conditions as in Example 1 to obtain a porous carbon plate.

[0028]

[Table 1]

[0029]

INDUSTRIAL APPLICABILITY The present invention uses a porous carbon plate having a pore diameter gradient with sheeting equipment by a papermaking method and an impregnation sheeting equipment by an impregnation method which are commonly used, and has high electric conductivity and chemical resistance. It becomes possible to inexpensively produce an excellent high-quality porous carbon plate, the porous carbon plate according to the present invention does not change the apparent density and bending strength even if a pore diameter gradient is applied, Can contain a large amount of phosphoric acid electrolyte in a large portion, and has good gas permeability,
Further, the phosphoric acid electrolyte retainability is large in the portion having a small pore diameter, which is effective as a fuel cell electrode.

Claims (1)

[Claims] 1. An organic fiber 20 for producing a carbon fiber having a fineness of 0.01 to 30 denier and a fiber length of 0.2 to 15 mm.
~ 95 parts by weight, and 5-80 parts by weight of pulp,
A step of producing at least two kinds of papermaking sheets having different tenacity within a range of the tenacity of 0.1 to 0.5 g / cm ³ , and impregnating the papermaking sheet with a solution of an organic polymer substance to prepare a dried impregnated sheet The laminated sheet is formed by stacking the impregnated sheet made from the papermaking sheet with the lowest tenacity and the impregnated sheet made from the papermaking sheet with the highest tenacity, in the order of the tightest papermaking sheet. A step of producing a precursor sheet by subjecting the laminated sheet to a hot press treatment and then an oxidizing treatment in air, and a heating carbonization treatment of the precursor sheet at a temperature of 800 ° C. or higher in an inert gas atmosphere. A method of manufacturing a porous carbon plate, comprising: