JPH0360478A - Production of porous carbon sheet - Google Patents

Abstract

PURPOSE:To easily and inexpensively obtain the carbon sheet excellent in electric conductivity, heat conductivity and uniformity by forming a slurry obtained by mixing specified fibers, wood pulp, etc., and a dispersion medium into a sheet, then impregnating the sheet with an org. polymeric material, drying and heating the sheet. CONSTITUTION:The carbon fiber producing org. fiber (A) consisting of >=1 kind among rayon, etc., and having 0.5-15 denier and 3-20mm length, the wood pulp, beatable fiber or binder fiber (B) by <=30wt.% based on the component A and a dispersion medium (C) are mixed to obtain a slurry. The slurry is wet-formed into a sheet (D). One or plural sheets D are laminated, and the laminate is punched at >=50 units/cm<2> by a needle having <=2mm maximum diameter to obtain a treated sheet (E). The sheet E is impregnated with 20-160wt.% of an org. polymeric material such as a furan resin to obtain an impregnated sheet (F). The sheet F is precured at 105-180 deg.C for 1-30min, heated at >=800 deg.C in an inert gas atmosphere, baked and carbonized to produce the porous carbon sheet.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a porous carbon plate, and more specifically, the present invention relates to a method for manufacturing a porous carbon plate. The present invention relates to a method for manufacturing quality carbon plates.

[Conventional technology]

Conventionally, as a method for obtaining carbon fiber sheets used in the production of porous carbon plates, there has been known a method of making carbon fiber mixed paper, in which paper is made from carbon fibers that have been mined in advance 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 performances, the above-mentioned mixed paper is impregnated with a thermosetting resin solution,
Again, a method of heating and carbonizing in an inert atmosphere is known. 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 sufficiently bonded, and it has therefore been difficult to obtain carbon fiber paper with sufficiently low electrical resistance.

Furthermore, since carbon fiber has a high specific gravity, it is difficult to obtain a highly porous plate, and it is difficult to control the material to a high density and pore diameter suitable for various uses. Moreover, since two firing steps are required, the product has the disadvantage of being extremely expensive, and there has been a desire to develop an inexpensive manufacturing method. In addition, with the above method, it is difficult to make thick sheets with uniform thickness, and carbon fiber is not hydrophilic and has high elasticity.
It had the drawbacks of poor adhesion to pulp and weak sheet strength. Therefore, it was necessary to incorporate binder fibers other than pulp (Japanese Patent Publication No. 53-18603).

The present inventors previously developed a wet papermaking method (Japanese Patent Application No. 57-226494), but as with the above method, binder fibers were used, so it had the disadvantage that it was difficult to obtain a porous sheet. Ta. Furthermore, this method has the disadvantage that binder fibers and the like adhere to the dryer and canvas during paper making, making regular operation difficult. Furthermore, sheets made in this manner inevitably have fibers lying on the sheet surface due to the manufacturing method. For this reason, the thermal conductivity and electrical conductivity in the thickness direction penetrating the sheet are about 1/10 to 1/20 compared to the respective values in the direction along the sheet. This was a major problem when conductivity was required in the translayer direction.

[Problem B to be Solved by the Invention] The present invention improves the above-mentioned drawbacks and can produce porous carbon plates with any average pore diameter and any porosity using commonly used paper machines and needle punch equipment. It is an object of the present invention to provide a method for manufacturing at low cost with a single firing step.

[Means to solve the problem]

According to the present invention, the above object is achieved by applying a dispersion medium to one or more organic fibers for producing carbon fibers and wood pulp or beatable fibers or binder fibers in an amount of 30% by weight or less based on the organic fibers. The added slurry is subjected to wet paper making, one or more of the obtained wet paper sheets are stacked and needle punched, and the needle punched sheet is impregnated with a solution of an organic polymer substance to form an impregnated sheet. , After drying this impregnated sheet, 8
This is achieved by a method for producing a porous carbon plate, which is characterized in that carbonization is performed by heating to a temperature of 00°C or higher. The configuration of the present invention will be explained in more detail.

The organic fibers for producing carbon fibers used in the present invention include ordinary carbon fibers such as ordinary rayon, pitch fiber, lignin fiber, phenolic resin fiber, acrylic fiber, etc. It is also possible to use organic fibers that are commonly used in such cases, and two or more of these may be used in combination with beatable fibers or fibrillated fibers, or beatable or fibrillated fibers alone. May be used in The organic fiber for carbon fiber used in this paper making method is 0.5 to 15 denier and 3 mm to 20 In[ll] in length, preferably 1.5 to 10 denier in length and 3 mm to 20 In[ll] in terms of manufacturing and pore diameter after firing. Those with a diameter of 5 to 15 mm are selected depending on the purpose and used alone or in combination of two or more. If necessary, unbeaten fibers are mixed therein.

Pulp, Vine - The wood pulp used here may be from softwood or hardwood, but softwood is preferable.Chemical pulp is better than mechanical pulp. It is better to proceed.

The beatable fiber may be any type of fiber that has been beaten or can be beaten, such as polyethylene, polyacrylonitrile, aramid fiber, etc.

Examples of the binder fiber include polyvinyl alcohol, but any binder fiber that can bond the fibers after papermaking may be used.

Needle Punch The diameter of the needle used for needle punching is 2ξ or less at its maximum diameter, preferably 0.5 mm or less. Bunch processing is required with a needle density of at least 10 needles/cnN or more, preferably 50 needles/ci or more.

Furthermore, by laminating the sheets and subjecting them to needle punching, a single sheet can have the required basis weight, and pressurized heat bonding after resin impregnation can be made unnecessary.

Examples of organic polymer substances used for impregnating the salmon sheet include phenol resin, epoxy resin, unsaturated polyester resin, furan resin, thermosetting resin such as polydivinylbenzene, vinyl chloride resin, and vinylidene chloride resin. , thermoplastic resins such as vinyl fluoride resin, vinylidene fluoride resin, acrylic resin, and even lignin, pitch, or tar. The desirable properties of these polymer compounds are that they are soluble in some kind of solvent 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 bonding, and thermosetting resins are preferred.

A sheet is impregnated with a solution of the organic polymer material. If the amount of impregnation adhering to the sheet is too small, the binder effect and carbonization yield during carbonization will be poor, and if it is too much, it will become clogged, making it difficult to adjust the porosity and making it brittle. The amount of impregnation is 20 to 1% of the weight of the sheet.
60% is preferable, and 60 to 120% is more preferable.

When using regenerated cellulose, such as rayon, as the organic fiber, in addition to the above-mentioned mixed impregnation treatment with the organic polymer, impregnation treatment with a heat resistance improver can be used in combination to achieve good effects in terms of carbonization yield, strength, etc. bring. As the heat resistance improver, any of those commonly used in producing rayon carbon fibers can be used. For example, metal phosphates include monobasic magnesium phosphate, monobasic calcium phosphate, monobasic sodium phosphate, monobasic potassium phosphate, etc., and ammonium salts of various acids include ammonium chloride, ammonium sulfate, ammonium hydrogen sulfate, phosphoric acid Ammonium, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium salt of polyphosphoric acid, ammonium borate, etc. can be suitably used.

The press-impregnated sheet may be subjected to heating carbonization treatment after drying, or press treatment may be performed as necessary before heating carbonization. The impregnated sheet may be precured before pressing. When pre-curing is performed, the organic polymeric substance within the sheet no longer flows, so that uniform pressing can be performed. Pre-curing treatment conditions are 105°C to 180'C without complete curing.
, about 1 minute to 30 minutes is suitable. Press molding is performed to give the final carbon plate the required thickness, shape, porosity, and pore size, and at this time, heat treatment is also used to harden the resin in the impregnated sheet. The hardening process during pressing made it possible to maintain a constant sheet thickness and at the same time obtain a flat sheet. Further, by adjusting the press pressure or the thickness of the spacer, the thickness, porosity, and pore diameter of the carbon plate can be arbitrarily changed. During the above press treatment, a thick carbon plate can be easily obtained by stacking a required number of thin impregnated sheets, preferably two or more sheets, and performing the press treatment in the same manner. When stacking the impregnated sheets, if the sheets are stacked alternately in the vertical and horizontal directions, the sheet orientation will be eliminated and a carbon plate with a uniform thickness without cracks will be obtained. Press heating conditions are 150-220℃5
A suitable time is 1 to 60 minutes.

The impregnated sheet or the sheet subjected to the above press treatment is subjected to stabilization treatment if necessary, and then fired to obtain the porous carbon plate of the present invention. The stabilization treatment is performed in order to improve the carbonization yield and graphitization rate of the organic fiber after the heating carbonization step. This is particularly effective when the organic fiber is acrylic fiber or pitch fiber. The stabilization treatment conditions are not particularly specified, but
Preferably, the treatment is carried out in the air at 150 to 350° C. for several tens of minutes to several tens of hours, depending on the type of organic fiber used. The above-mentioned stabilized sheet is then 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.

[For production]

In the present invention, a sheet obtained by a papermaking method is needle-punched so that some of the fibers are oriented in a direction perpendicular to the sheet surface, and after being impregnated with resin, the sheet is fired, so that the fibers are oriented perpendicularly to the sheet surface. On the other hand, we manufacture sublime thick porous carbon plates with good electrical and thermal conductivity.

[Examples] In order to make the present invention easier to understand, Examples are shown below, but the following Examples do not limit the present invention. In addition, parts and % in the examples are parts by weight and % by weight, respectively.

1 Arashi Kami Wood Pulp (NBKP) Canadian Freeness 25
Add water to 20 parts by weight of the acrylic fibers beaten to 0- and 80 parts by weight of acrylic fibers with a thickness of 3 denier and a length of low to obtain a slurry, and make a slurry using a conventional method on a circular paper machine to give a basis weight of 100 g.
/nf sheet was made. Stack 5 of these sheets and
．． Needle punching was performed using a needle with a thickness of 5 mm at a density of 50 needles per square centimeter. This was impregnated with a polymeric substance (phenol resin, crowd chemical Pi, -2215, 70% of the weight of the mixed paper) in a methanol solution.
It was dried at a temperature of 0.05°C.

After drying, the two sheets were stacked and heat pressed to a thickness of 3.5 mm, and after being heat-stabilized in air at 220°C for 4 hours between five plates of graphite, the sheets were heated to 1000°C. The material was heated and carbonized by sandwiching it between graphite plates in a nitrogen gas atmosphere for 1 hour, and then heat-treated at 2800° C. in an argon gas atmosphere to obtain a porous carbon plate.

Ura Ekiso 1 Wood Pulp (NBKP) Canadian Freeness 25
A slurry was obtained by adding water to 20 parts by weight of the acrylic fibers beaten to 0d and 80 parts by weight of acrylic fibers having a thickness of 3 tenier and a length of 10 nu++.
A sheet of QQg/rrf was made. Five of these sheets were stacked and needle punched using a needle with a thickness of 0.5 mm at a density of 150 needles per square centimeter.
215 (70% of the weight of the mixed paper) was impregnated with a methanol solution and dried at a temperature of 105°C. These two sheets were stacked, heat pressed, made to a thickness of 3.5 mm, sandwiched between 5Tm graphite plates, heated and stabilized in air at 220°C for 4 hours, and then placed in a nitrogen gas atmosphere at 1000°C. The material was heated and carbonized by being sandwiched between graphite plates for an hour, and then heat treated at 2800''C in argon gas to obtain a porous carbon plate.

Ta.

Bun JJL History Wood Pulp (NBKP”) Canadian Freeness 2
A slurry was obtained by adding water to 20 parts by weight of the acrylic fibers beaten to 50 d and 80 parts by weight of acrylic fibers having a thickness of 3 denier and a length of 1 Owa, and then processed using a circular paper machine in a conventional manner to obtain a slurry with a basis weight of 10 d.
A sheet of 0 g/+rf was made. These 10 sheets were stacked and needle-punched using a gauge with a thickness of 0.5ξ at a density of 150 needles per square centimeter.
215 (70% of the weight of the mixed paper) was impregnated with a methanol solution and dried at a temperature of 105°C. This one piece, 51
Place between 1IIIl graphite plates and heat at 220"C for 4 hours.
After heat stabilization treatment in air, heat carbonization was performed by sandwiching between graphite plates for 1 hour in a nitrogen gas atmosphere of 1000"C, and then heat treatment was performed at 2800 °C in argon gas to form porous carbon. Got the board.

For comparison of effectiveness, the following method without needle punching was performed.

Canadian Freeness 25 for wood pulp (NBKP)
A slurry was obtained by adding water to 20 parts by weight of the acrylic fibers beaten to 0IIIft and 80 parts by weight of acrylic fibers having a thickness of 3 denier and a length of 10 nun, and using a circular paper machine in a conventional manner to obtain a slurry with a basis weight of 100 g/rrf. A sheet was made. This sheet is coated with polymeric substances (phenol resin, Crowd Chemistry PL-22).
15 (70% of the weight of the mixed paper) was impregnated with a methanol solution and dried at a temperature of 105°C. Laminate 10 sheets of this,
It was heat pressed to a thickness of 3.5ξ, sandwiched between 5 mIn graphite plates, heated and stabilized in air at 220°C for 4 hours, and then heated in a nitrogen gas atmosphere at 1000°C for 1 hour. It was heated and carbonized by sandwiching it between graphite plates, and then heat treated at 2800℃ in argon gas.
A porous carbon plate was obtained.

The density, electrical resistance in the through-layer direction (thickness direction), and thermal conductivity of the porous carbon plates obtained in Examples 1 to 3 and Comparative Example were measured. These manufacturing conditions and the above measurement results are summarized in Table 1.

Table [Effects of the Invention] The present invention uses fibers such as regenerated cellulose fibers, pitch fibers, acrylic fibers, etc., which are normally used as raw materials for manufacturing carbon fibers, and beatable fibers, such as wood fibers, and After the obtained sheet needle punching is impregnated, the sheets are preferably laminated, pressed, and heated to form a thick porous carbon plate.

The first feature of the present invention is that by needle-punching the original sheet, the fibers can be oriented perpendicularly to the sheet, and the electrical conductivity in the through-layer direction after firing is improved.
And thermal conductivity can be improved. This seems to be because heat and electricity flow easily along the fibers.

The second feature is that the original sheet can be manufactured using a normal wet paper machine, and conventional needle punches can be used, making it possible to obtain inexpensive sheets. Further, the manufacturing method of the present invention can easily produce a uniform and flat sheet with less unevenness in basis weight compared to carbon fiber papermaking methods using dry papermaking methods, such as carding methods, and wet papermaking methods.

Thirdly, by laminating with needle punching, there is no need to use hot press for adhesion, and since there is no compression, the density can be lowered and a sheet with high porosity can be obtained. Furthermore, there is an advantage that the sheet weight can be adjusted arbitrarily. Furthermore, it is also possible to manufacture a porous carbon plate of any thickness by laminating thin sheets using hot press and performing an adhesive treatment. In addition, by selecting the thickness of the raw fibers, adjusting the blending and press processing, it is possible to freely and easily adjust the pore size and porosity of the plate, which is a particular problem when used as an electrode base material for fuel cells and secondary batteries. It became possible to control it.

Claims (1)

[Claims] 1. A slurry prepared by adding a dispersion medium to one or more organic fibers for producing carbon fibers and 30% by weight or less of wood pulp, beatable fibers, or binder fibers is wet-paper-formed. One or more sheets of wet-processed paper are piled up and subjected to needle punching treatment, the needle punched sheet is impregnated with a solution of an organic polymer substance to form an impregnated sheet, and this impregnated sheet is dried. A method for producing a porous carbon plate, which comprises carbonizing the plate by heating it to a temperature of 800° C. or higher in an inert gas atmosphere.