JPH0369615A - Preparation of porous carbon plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Conventional technology]

Conventionally, as a method for obtaining a carbon #a fiber sheet, carbon fiber mixed paper is known, in which carbon fibers that have been fired and carbonized in advance are made into paper together with a valve 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 above-mentioned mixed paper is impregnated with a thermosetting resin solution and heated and carbonized again in an inert atmosphere. In this method, organic substances such as bulbs 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, 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 a firing process is required at each stage of fiberization and sheet formation, it has the disadvantage of being extremely expensive, and therefore, 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, so it has the disadvantage of poor adhesion to pulp and weak sheet strength. . Therefore, it was necessary to mix binder fibers other than pulp (Special Publications Publication No. 1973-
18603). In addition, the present inventors previously applied for a method using a papermaking method (Japanese Patent Publication No. 57-226494), but in this method, the sheet is immersed in a resin solution and impregnated with resin, so the sheet strength is maintained to a certain extent in the solution. This strength improvement measure required an increase in the wood pulp content. Increasing the wood pulp content increased the density, making it difficult to obtain a sublime sheet. Moreover, the cost of this impregnation treatment was also large, and some kind of improvement was required.

[Problem to be solved by the invention]

The present invention improves the above-mentioned drawbacks, and at the same time produces a porous carbon plate of any average pore diameter and any porosity using commonly used sheet forming equipment, at low cost and with high electrical conductivity and chemical resistance. The purpose is to provide a method for manufacturing products of excellent high quality.

[Means to solve the problem]

The above object, according to the present invention, includes a step of applying an organic polymer substance to an organic fiber for carbon fiber production in an amount of 5 to 200% based on the weight of the organic fiber, and drying the organic fiber after the application. a step of forming the dried organic fiber into a sheet by a wet method or a dry method, and a step of carbonizing the sheet by heating it to a temperature of 800° C. or higher in an inert gas atmosphere. This is achieved by a method of manufacturing a porous carbon plate characterized by:

The configuration of the present invention will be explained in detail below.

Organic fibers The organic fibers for carbon fibers used in the present invention include ordinary rayon, pitch fibers, lignin fibers, phenolic resin fibers, acrylic fibers, and other organic fibers that are commonly used as raw materials for producing carbon fibers. Yes, 0.5-1
5 denier, length 3 mm to 50 mm, preferably 1.5 to 10 denier, length 5 to 20 IIl [o] from the viewpoint of manufacturing and pore diameter after firing, etc., selected depending on the purpose, singly or in combination. Use the above in combination.

Organic polymeric substance The organic polymeric substance applied to the organic fibers described above must be dissolved in some kind of solvent or melted at high temperatures during heat treatment.
and has a carbon content of 30% by weight or more, and after carbonization, serves as a carbonaceous binder for bonding within carbon fibers, such as thermosetting resins such as phenol resins, epoxy resins, unsaturated polyester resins, furan resins, and polydivinylbenzene. Polymer resins are preferred.

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, phosphate metal salts include monobasic magnesium phosphate, monobasic calcium phosphate, monobasic hexathorium phosphate, monobasic potassium phosphate, etc., and ammonium salts of various acids include ammonium chloride, ammonium sulfate, and ammonium hydrogen sulfate. , ammonium phosphate, heptammonium phosphorus M hydrogen phosphate, ammonium dihydrogen phosphate, ammonium salt of polyphosphoric acid, ammonium borate, and the like can be suitably used.

The amount of the organic polymer substance applied is 5 to 200% based on the weight of the organic fiber.

If it does not contain at least 5% resin, intra-sheet adhesion or inter-sheet adhesion during heating will be insufficient;
If this is applied, the resin will flow out when heated, giving the sheet two-sided properties, blocking the holes and worsening gas permeability.

When a thermosetting resin is used as the dried organic polymer material, it is dried at a temperature and for a time that does not cause thermosetting.

Sheet bottom shape (1) In the case of wet papermaking, the papermaking method can be any method that can be used for wet papermaking, such as hand papermaking, round netting, fourdrinier, inclined wire, etc. If you want to obtain a sheet with good uniformity, the paper density It is better to lower it. If the strength is weak after dewatering with a wire mesh, adding 5% to 40% of beaten wood valve will increase the strength and connect the sheets.

Usually, the wet paper is subjected to a pressing process, but the pressing process can be omitted when it is not necessary or difficult to carry out.

Drying process after wet papermaking In addition to cylinder dryers such as the multi-tube type and Yankee type used in normal wet paper machines, band dryers, honeycomb dryers, isothermal air dryers, infrared dryers, etc. can be used. A hot air dryer or a dryer using infrared rays makes the sheet bulky and is convenient for producing sheets with high porosity.

Wet paper made without using a connecting valve has low bow strength, so open draw must be minimized as much as possible. If necessary, it may be carried using canvas or felt.

(2) When using the dry method, the random web method or card method is usually used, but
Either method may be used. The organic fiber for carbon fiber used in the random web method has a denier of 0.5 to 15,
Length 3 mm to 150 mm, preferably 1.5 to 8 denier from the viewpoint of manufacturing and pore diameter after firing, length 5 to 102 mm
mm mm depending on the purpose and used alone or in combination of two or more.

The organic fiber for carbon fiber used in the card method is 0.5 to 1
5 denier, length 3mm to 150mm preferably manufactured,
A material having a length of 1.5 to 8 dennies and a length of 51 to 102 mm is selected depending on the purpose from the viewpoint of the pore diameter after firing, etc., and is used alone or in combination of two or more kinds.

Mechanical bonding methods for fibers include needle punching, stitch bonding, and the like, but any method that mechanically entangles fibers may be used. It is also good to use a base fabric when fixing the sheet. A method of fixing the fibers by utilizing the adhesive properties of the applied polymeric substance can also be used.

The treated sheet after sheet formation may be subjected to heating carbonization treatment as it is after drying, or may be subjected to press treatment as necessary before heating carbonization. The press treatment is performed to give the final carbon plate the necessary thickness, shape, porosity, and pore size, and at this time, it is preferable to use heat treatment in combination to harden the resin in the sheet.

This curing treatment 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 pressing process, if the required number of thin sheets, preferably 3 or more, are stacked together and the press process is performed in the same manner,
A thick carbon plate can be easily obtained. When stacking the sheets, if the sheets are stacked alternately in the vertical and horizontal directions, the orientation of the sheets is eliminated, and a carbon plate with a uniform thickness and no cracks can be obtained.

Appropriate heating conditions for applying the heating effect by pressing are 150 to 220° C. and 1 to 60 minutes.

The sheet or the sheet subjected to the above press treatment is optionally subjected to oxidation treatment by heating in air, and then fired to obtain the porous carbon plate of the present invention.

The oxidation treatment is performed to improve the carbonization yield and graphitization rate of the organic fiber after the heating carbonization step. It is particularly effective in the case of organic fibers such as guacrylic fibers and pitch fibers. The oxidation treatment conditions are not particularly specified, but are preferably 150 to 350°C;
The treatment is carried out in air for a period of time ranging from several 10 minutes to 10-odd hours, depending on the type of organic fiber used.

The sheet obtained above was heated and carbonized in an inert gas atmosphere for 80 minutes.
A porous carbon plate is obtained by heating and firing at a temperature of 0° C. or higher.

Since these organic resins and fibers burn out when heated in the air, they are heated and carbonized in an inert gas such as N2 gas or Ar gas. The processing temperature is such that at least electrical conductivity is achieved8
Carbonization treatment is performed at a temperature of 00°C or higher, but in order to obtain high electrical conductivity and chemical resistance, the temperature is 1300°C or higher, preferably 2300°C or higher.
Perform heat treatment above ℃.

The present invention will be explained in more detail below with reference to Examples. However, the following examples do not limit the present invention.

In addition, parts and % in the examples are parts by weight and % by weight, respectively.

Example 1 Polymer JR (phenolic resin, Crowd Chemical PL-2215, 80% solid content based on the weight of the fiber) was applied to 3-denier acrylic fiber using a methanol solution, and then dried at a temperature of 105°C. The fibers were cut into 51 mm pieces, made into a sheet by a random web method, and then needle punched to make a sheet of 500 g/m'. on this sheet. The sheets were then pressed 2. without being laminated. A spacer was placed so that the distance was 0 mm, pressure was applied, and at the same time heat treatment was performed at 180° C. for 15 minutes. Next, the mixture was heated and stabilized in air at 220°C for 4 hours, and then heated and carbonized by being sandwiched between graphite plates for 1 hour in a nitrogen gas atmosphere at 1000°C.

Example 2 A polymer substance (phenolic resin, Crowd Chemical PL-2215, 80% solid content based on the weight of the fiber) was applied to 3-denier acrylic fiber using a methanol solution, and after drying at a temperature of 105°C, After cutting into 3 mm pieces, 85 parts of this fiber and 15 parts of LBKP of 300 mm of frozen charcoal were used to make a sheet of 180 g/m'' using a Fourdrinier paper machine.Then, the sheet was not laminated and was pressed to zero. A spacer was placed so that the thickness was .5 mm, pressurized, and heat treated at 180°C for 15 minutes.Next, heat stabilization treatment was performed in air at 220°C for 4 hours, and then in a nitrogen gas atmosphere at 1000°C. de1
The material was heated and carbonized by sandwiching it between graphite plates for a period of time.

Example 3 A polymer substance (phenolic resin, Crowd Chemical PL-2215, 80% solids based on the weight of the fiber) was applied to 3-denier acrylic fiber using a methanol solution, and after drying at a temperature of 105°C, After cutting into 3 mm pieces, 85 parts of this fiber and 15 parts of LBKP of 300 g of frozen charcoal were used to make a sheet of 180 g/m' using a Fourdrinier paper machine. Next, 10 of the sheets were stacked and pressed in 4. A spacer was placed so as to be OM, pressure was applied, and heat treatment was performed at 180t for 15 minutes at the same time. Next, heat stabilization treatment was performed in air at 220°C for 4 hours, and then stabilized for 1 hour in a nitrogen gas atmosphere at 1000°C.
The material was heated and carbonized by sandwiching it between graphite plates for a period of time.

Example 4 A polymer substance (phenolic resin, Crowd Chemical PL-2215, solid content 30% based on the weight of the fiber) was applied to 3-denier acrylic fiber using a methanol solution, and after drying at a temperature of 105°C, After cutting into 3 mm pieces, 85 parts of this fiber and 15 parts of LBKP of 300 rn1 of frozen charcoal were used to make a sheet of 130 g/m' using a fourdrinier paper machine. Chemistry PL-2
215 (solid content: 50% based on the weight of the sheet) was impregnated with a methanol solution and dried at a temperature of 105°C. Next, without stacking the sheets, a spacer was placed using a press to give a thickness of 0.5 mm, and at the same time heat 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 by sandwiching between graphite plates for 1 hour in a nitrogen gas atmosphere at 1000°C.

The results of Examples 1 to 4 are summarized in Table 1.

Table 1 [Effects of the Invention] According to the present invention, fibers such as regenerated cellulose fibers, pitch fibers, acrylic fibers, etc., which are normally used as raw materials for producing carbon fibers, are coated with a resin, formed into a sheet, and preferably made into a single sheet. A thick porous carbon plate can be obtained by laminating a plurality of sheets and performing heat molding treatment using a press.

The first feature of the present invention is that it is not necessary to perform an impregnation treatment on the original sheet, so that manufacturing costs can be reduced.

Second, since carbon fibers are not used, about half of the carbon fibers disappear as gas when fired at 800° C. or higher, making it easier to obtain porous carbon plates with extremely high porosity. For example, in conventional carbon plates obtained from carbon fiber papermaking, the porosity was limited to 70%, but with the method of the present invention, the porosity was 75%.
It has become possible to easily obtain a carbon plate with a porosity of ~85%, and a carbon plate with good gas permeability and liquid permeability.

The third feature is that the original sheet can be manufactured using a normal wet paper machine, improving productivity and making it possible to obtain sheets at low cost.

The fourth feature is that because the sheet is only impregnated with resin, the four holes of the sheet are less likely to collapse and have good gas permeability.
It is a convenient electrode for secondary batteries, etc.

Fifth, it is also possible to manufacture a porous carbon plate of any thickness by laminating thin sheets and pressing them.

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 step of applying an organic polymer substance to an organic fiber for carbon fiber production in an amount of 5 to 200% based on the weight of the organic fiber, a step of drying the organic fiber after the application, Porous, characterized by comprising the steps of forming the dried organic fiber into a sheet by a wet or dry method, and carbonizing the sheet by heating it to a temperature of 800° C. or higher in an inert gas atmosphere. A method for manufacturing quality carbon plates.