JPH0253992A - Production of cellular carbon board - Google Patents

Abstract

PURPOSE:To obtain the subject carbon board excellent in chemical resistance, electric conductivity, gas permeability, strength, etc., by wet forming organic fibers for producing carbon fibers into sheets of paper, applying a binder thereto and thermally carbonizing the resultant sheets of paper at a specific temperature or above. CONSTITUTION:(A) Organic fibers, such as rayon or pitch fibers, having preferably 0.5-15 denier and 3-50mm length for producing carbon fibers are dispersed in water to provide a slurry, which is then wet formed into sheets of paper. (B) A binder, such as acrylic emulsion, is then applied thereto by spraying or dipping to provide a precursor sheets of desired dimensions or shape, which is subsequently placed in (C) an atmosphere of an inert gas and thermally carbonized at >=800 deg.C to afford the objective carbon board.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a porous carbon plate, and more specifically, a porous carbon plate having a high bulk and excellent chemical resistance, electrical conductivity, gas permeability, and strength. The present invention relates to a method of manufacturing a thick porous carbon plate.

[Conventional technology]

BACKGROUND ART Conventionally, as a method for producing a porous carbon plate, a method is known in which pre-fired carbon fibers are made into paper together with fibrillated fibers such as pulp and a binder to make carbon fiber mixed paper. However, such mixed paper has relatively low electrical conductivity +IU and lacks chemical resistance, making it unsuitable for applications such as fuel cell electrodes. 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 then heated and carbonized again in an inert gas atmosphere. In this method, organic substances such as pulp are carbonized by heat treatment, so fiber paper with high electrical conductivity and improved chemical resistance can be obtained. However, since the carbon wAw1' itself has a high modulus of elasticity, the contact portions between the carbon fibers are not sufficiently bonded, and it has therefore been difficult to obtain a porous carbon plate with sufficient electrical conductivity.

Further, since carbon fiber has a high specific gravity, bulky porous carbon plates cannot be obtained, and it is difficult to control the bulk density and pore diameter to suit various uses. Moreover, fiberization,
Moreover, since a firing process is required at each stage of forming the sheet, it has the disadvantage of being extremely expensive. Furthermore, with this method, it is difficult to make a thick sheet of uniform thickness, and since carbon fiber is not hydrophilic and has high elasticity, it has poor adhesion to pulp and has the disadvantage of weak sheet strength. Therefore, it was necessary to mix binder fibers other than pulp (
(Japanese Patent Publication No. 53-18603), the present inventors previously proposed a method for manufacturing porous carbon plates using a wet papermaking method (
JP-A-59-133094) uses binder fibers in the same manner as the above-mentioned method, and therefore has the disadvantage that it is difficult to obtain a porous sheet. In addition, binder fibers and the like adhere to the dryer and canvas during paper making, making regular operation difficult.

Furthermore, even in the wet papermaking method (Japanese Patent Application Laid-Open No. 61-12918) that does not use binder fibers, in the case of normal wet papermaking,
It is necessary to mix bulbs for fiber-to-fiber adhesion, and as more bulbs are added, the density of the paper sheet increases, making it difficult to make bulky sheets and making it difficult to make carbon plates with high porosity. It was difficult.

[Problem to be solved by the invention]

The present invention improves the above-mentioned drawbacks, and provides a porous carbon plate of any average pore diameter and any porosity, which is excellent in chemical resistance, electrical conductivity, gas permeability, and strength, and is generally used. The purpose of this paper is to provide a method of manufacturing the paper at low cost using a conventional paper machine.

[Means to solve the problem]

The above object, according to the present invention, includes a step of wet-paper-making an aqueous slurry substantially consisting of organic fibers for producing carbon fibers to produce a paper sheet, and an operation of applying a binder to the paper-making sheet 1. This is achieved by a method for manufacturing a porous carbon plate characterized by comprising a step of heating and carbonizing at a working temperature to create a precursor sheet having the same shape and dimensions.

FIG. 1 shows a process diagram of a method for manufacturing a porous carbon plate according to the present invention. However, in the figure, the steps indicated by a double frame are essential steps for the present invention, and the steps indicated by a single frame are preferable optional steps.

General auxiliary operations such as drying can be inserted as appropriate between each step.

The organic fibers for producing carbon fibers used in the present invention are organic fibers commonly used as raw materials for producing carbon fibers, such as ordinary rayon, pinch fibers, lignin fibers, phenolic resin fibers, and acrylic fibers. The thickness is 0.
5 to 15 denier, length 3 m to 50 m++, preferably thickness 1.5 to 50 m from the viewpoint of manufacturability and pore diameter after firing.
Select one with a length of 10 denier and 5 to 20 dragons depending on the purpose.

A dispersion medium such as water, which is commonly used in wet paper making, is added to one type or a combination of two or more of the above organic fibers to form a slurry. In the present invention, the dispersoid of the slurry consists essentially of the above-mentioned machine fibers. If necessary, fibrillated binder fibers such as bulbs may be added to the dispersoid in an amount of less than 10% by weight, preferably 5% by weight or less, to assist in handling strength of the paper sheet.

The above slurry is subjected to wet paper making using a conventional method. That is,
The papermaking method may be any method that can be used for normal wet papermaking, such as hand papermaking, circular wire, long wire, and inclined wire, and especially when it is desired to obtain a sheet with high uniformity, the papermaking density may be lowered. A press treatment is usually performed on the wet paper after dewatering with a wire mesh or the like, but the press treatment can be omitted when it is not necessary or when it is difficult to carry out.

According to the present invention, the tensile strength of the wet paper made without substantially using binder pulp or the sheet after applying the binder and before drying is weak, so open draw must be minimized as much as possible. If necessary, it is best to carry it in a canvas or felt bag.

Dry the wet paper if necessary. For drying, in addition to cylinder type dryers such as the multi-tube type and Yankee type used in normal wet paper machines, it is also possible to use panto dry sea, honeycomb dryers, hot air dryers, infrared dryers, etc. can. Dryers using hot air or red wire produce bulky sheets, which is convenient when producing sheets with high porosity.

A binder is applied to the wet paper or the dried sheet by spraying or dipping with an adhesive to form a bonded sheet.

As the binder, an emulsion-based adhesive such as an acrylic emulsion or a phenol emulsion, a water-soluble adhesive, or an organic solvent-based adhesive can be used.

In order to further increase the strength of the porous carbon plate finally obtained, the bonding sheet may be impregnated with a solution of an organic polymer substance, if necessary. Organic polymer substances used for impregnation include, for example, phenol resins, epoxy resins, unsaturated polyester resins, furan resins, thermosetting resins such as polystyrene, vinyl chloride resins, vinylidene chloride resins, vinyl fluoride resins, and fluoride resins. Thermoplastic resins such as vinylidene resins, acrylic resins, and even lignin, pitch, or tar are also used. 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 is preferably a thermosetting resin. If the amount of impregnation adhering to the sheet is too small, the effect on the strength of the porous carbon plate will be small and the carbonization yield during carbonization will decrease. On the other hand, if the amount of impregnation is too excessive, the pores will be clogged, making it difficult to adjust the porosity and making it brittle. The preferred amount of impregnation is 20 to 160% by weight, more preferably 60 to 120% by weight of the solid content of the organic polymer substance based on the dry weight of the paper sheet.

By using an organic polymer material for impregnation as the binder, impregnation can be performed simultaneously in the bonding step. At this time, the amount of impregnation can be increased by further impregnating separately.

When using regenerated cellulose, such as rayon, as an organic fiber for producing carbon fibers, impregnation treatment with a heat resistance improver is performed in addition to the mixed impregnation treatment with the organic polymer described above. As the heat resistance improver, any one commonly used in producing rayon carbon fibers can be used.

For example, phosphate metal salts include monobasic magnesium phosphate, monobasic calcium phosphate, monobasic sodium phosphate, monobasic potassium phosphate, etc., and various vinegar ammonium salts include ammonium chloride, ammonium sulfate, ammonium hydrogen sulfate, Ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium salt of polyphosphoric acid, ammonium borate, etc. can be suitably used.

The joining sheet or the sheet impregnated with an organic polymer substance may be subjected to heating carbonization treatment as it is after necessary drying, or may be subjected to pressing treatment as necessary before heating carbonization. Before the press treatment, the bonded sheet may be precured by heating. Pre-curing makes it difficult for the organic polymeric substance within the sheet to flow, allowing for more uniform pressing. The heating conditions for preliminary curing are 10, which does not completely cure.
5°C to 180°C and about 1 minute to 30 minutes are suitable. Pressing process is performed to obtain the required thickness of the final porous carbon plate.
This is carried out to impart shape, porosity, and pore size, and at that time, it is preferable to simultaneously perform heat treatment to harden the resin in the sheet after bonding and impregnation. This curing process makes it easier to maintain a constant sheet thickness and at the same time obtain a flat sheet. Furthermore, the thickness, porosity, and pore diameter of the carbon plate can be arbitrarily changed by adjusting the press pressure or the thickness of the swazer. Appropriate conditions for this heat curing are 150 to 220°C and 1 to 60 minutes.

At the time of the above-mentioned press treatment, if the press treatment is performed in the same manner with a required number of bonded sheets, preferably three or more bonded sheets stacked one on top of the other, a thick carbon plate can be easily obtained. When stacking the bonded 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.

After the bonding sheet is optionally subjected to the above-mentioned impregnation, preliminary curing, and press treatment, it may be subjected to a stabilization treatment by heating, if necessary, before heating and carbonization. The stabilization treatment is performed to improve the carbonization yield and graphitization rate of the organic fiber after the heating carbonization step, and is particularly effective when the organic fiber is an acrylic fiber or a pinch fiber.

The heating conditions for the stabilization treatment are a temperature of about 150 to 350°C;
A suitable time period is from several tens of minutes to several hundreds of hours, and is carried out in an oxygen-containing gas atmosphere such as air, although this may vary depending on the type of organic fiber used for boat fishing.

The precursor sheet created through the above steps is carbonized by heating at a temperature of 800° C. or higher in an inert gas atmosphere to obtain a porous carbon plate.

〔Example〕

The present invention will be explained in more detail by way of examples.

However, the following examples are not intended to limit the scope of the present invention. In addition, parts and % in the examples are parts by weight and % by weight, respectively.

Next LLL 50 parts by weight of acrylic fibers with a thickness of 7 denier and a length of 3 mm.Water was added to 50 parts by weight of acrylic fibers with a thickness of 3 denier and a length of 3 mm to form a slurry, and the slurry was made into a slurry using a circular mesh paper machine. A wet paper sheet having a weight of 50 g/m on absolute dry basis was prepared by the method, and a polymer substance (phenol resin emulsion) was spray-coated as an adhesive onto this sheet, and then dried with a Yankee dryer. This sheet was impregnated with a methanol solution of a polymeric substance (phenol resin, Gunei Chemical PL-2215) at a solid content of 70% based on the weight of the acrylic fibers, and then dried at a temperature of 105°C. . Next, it was sandwiched between five crane graphite plates without laminating or pressing.
After heat stabilization treatment in air at ℃ for 4 hours, 10
Carbonization was performed by heating in a nitrogen gas atmosphere at 00° C. for 1 hour while temporarily sandwiching graphite.

Ryuu 1 50 parts by weight of acrylic fibers with a thickness of 7 denier and a length of 10 m, and 50 parts by weight of acrylic fibers with a thickness of 3 denier and a length of 10 m, were made into a slurry using an inclined wire paper machine using a conventional method. Paper is made into wet paper with an absolute dry equivalent weight of 150 g/m,
A polymer substance (phenol resin emulsion) was spray-coated as an adhesive onto this sheet, and then dried with a hand dryer. Next, this Sea I was pressed without stacking and pressurized to 1.51 cm, and at the same time, heated at 180°C.
Heat curing treatment was performed for 15 minutes. Next, after heat stabilization treatment was performed in air at 220° C. for 4 hours, heating carbonization was performed for 1 hour in a nitrogen gas atmosphere at 1000° C. by temporarily sandwiching graphite.

Acanthitis 1 Add water to 50 parts by weight of acrylic fibers with a thickness of 7 denier and a length of 31 cm, and 50 parts by weight of acrylic fibers with a thickness of 3 denier and a length of 3 mm to make a slurry, and make a slurry using a circular mesh paper machine in a conventional manner. A wet paper sheet with an absolute dry weight of 150 g/m was made, and a polymeric substance (phenol resin emulsion) was spray-coated as an adhesive on this sheet, and then dried with a Yankee dryer. This sheet is coated with a polymer material (
A methanol solution of phenolic resin, Gunei Kagakuen, -2215) was added to the solid content of 87% (based on the weight of acrylic fiber).
It was impregnated with a coating weight of = J and dried at a temperature of 105°C. Next, five sheets of this sheet were laminated and pressurized to 3.5 ***, and at the same time, heat curing treatment was performed at 180° C. for 15 minutes. Next, after performing heat stabilization treatment in air at 220° C. for 4 hours, heating carbonization was performed for 1 hour in a nitrogen gas atmosphere at 1000° C. by placing it between a graphite plate.

Table 1 shows the manufacturing conditions including conditions other than the above and the quality of the obtained porous carbon plates for each example.

Table 1 (Continued) [Effects of the Invention] In the method of the present invention, a paper sheet is produced without substantially using fibrillated fibers, so a sheet with low density can be obtained, and carbon fibers are used. 800° because it doesn't
Since about half of the sheet weight is removed as gas during heating and carbonization, a porous carbon plate with always high porosity can be easily obtained. For example, in conventional carbon plates made from carbon fiber paper sheets, the porosity was limited to 70%, but with the method of the present invention, carbon plates with a porosity of 75 to 85% can be easily obtained. A carbon plate with excellent gas permeability and liquid permeability can be obtained.

Furthermore, since the paper sheet can be easily produced using a normal wet paper machine, productivity is improved and the sheet 1- can be obtained at low cost.

In addition, the manufacturing method of the present invention has less unevenness in basis weight than the method based on carbon fiber paper making, and can easily produce uniform and flat sheets, and has uniform gas permeability and liquid permeability, making it suitable for fuel cells, secondary It can be used as an electrode base material that is extremely suitable for batteries and the like.

Furthermore, a porous carbon plate of any thickness can be easily manufactured by laminating thin-haired sheets and pressing them.

In addition, by selecting the size of raw Nemi 1 fiber, adjusting the blending and press processing conditions, 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, can be freely adjusted. And it can be easily controlled.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of a method for manufacturing a porous carbon plate according to the present invention.

Claims (1)

[Scope of Claims] 1. A step of producing a paper sheet by wet paper-making an aqueous slurry consisting essentially of organic fibers for producing carbon fibers, which includes an operation of applying a binder to the paper sheet, and forming the paper sheet into a predetermined size and shape. A method for producing a porous carbon plate, comprising the steps of: creating a precursor sheet; and heating and carbonizing the precursor sheet at a temperature of 800° C. or higher in an inert gas atmosphere.