JP3131911B2 - Method for producing thick porous carbon material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thick porous carbon material having good porosity and high strength skeletal structure.

[0002]

2. Description of the Related Art Porous carbon materials, which are lightweight and have excellent properties such as conductivity, heat resistance and chemical resistance, have been widely used as filter materials, battery electrode materials, adsorbent materials, heat insulating materials and other industrial materials. Although they are used in the field, industrial filters are being widely used, taking advantage of the above characteristics, high porosity and controlled porosity.

Conventionally, as a typical technique for producing a porous carbon material, a process of kneading coke powder having a uniform particle size with a carbonizable binder such as tar pitch, followed by pulverization, molding, and calcining carbonization is known as a typical method. However, since it is difficult to set conditions for providing a uniform and stable pore structure, there is a disadvantage that mass productivity is poor. In addition, since the obtained material cannot be given sufficient strength, there has been a practical problem such as detachment of carbon powder during use.

[0004] In this respect, a technique for producing a porous carbon material (Japanese Patent Application Laid-Open No. 50-25808) in which a mixed sheet formed by molding carbon fibers together with pulp and a binder component is impregnated with a thermosetting resin liquid and then calcined and carbonized. Since the carbon fibers form the reinforcing skeleton and the thermosetting resin is converted into a glassy carbon structure, the material strength can be effectively increased. However, in this method, there are difficulties in controlling bulk density, pore diameter, porosity, and the like, and in addition, there is a problem that the production cost rises because expensive carbon fiber is used as a raw material.

Therefore, instead of expensive carbon fibers, organic fibers as raw materials are used, and an organic polymer substance or carbonaceous powder is suspended in a sheet formed by mixing pulp, carbonaceous powder, or the like. A method of impregnating the impregnated organic polymer substance and then performing a baking treatment (JP-A-61-236664, JP-A-61-236664)
236665). However, in this method, it is difficult to obtain a uniform and controlled pore structure because many locally closed voids are formed in the tissue.

[0006] The inventors of the present invention have previously proposed a production technique for obtaining a porous carbon material having both good porosity and high skeletal strength by making a heat-volatile substance containing α-cellulose as a main component. Process and the residual carbon ratio of 40 in the sheet
% Of the thermosetting resin solution, a step of semi-curing the impregnated sheet at a temperature of 50 to 150 ° C., a step of laminating the semi-cured sheets and uniformly heating the entire surface to reduce the sheet thickness. A method has been developed which comprises a step of compressing to 70 to 20% and a step of calcining and carbonizing the compressed sheet at a temperature of 800 ° C. or more in a non-oxidizing atmosphere (Japanese Patent Application No. 1-321729).
No.)

[0007]

According to the above prior art, a good quality porous carbon material can be obtained in accordance with the purpose. In this case, the heating did not reach the central portion of the compressed laminated sheet, and there was a problem in the process that involved difficulty in molding. For this reason, a porous carbon material having a thickness exceeding 50 mm could not be produced smoothly.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and, in addition to having good porosity and structure strength, to efficiently use a thick porous carbon material required in recent industrial filter materials. It is to provide a method for good manufacturing.

[0009]

In order to achieve the above object, a method for producing a thick porous carbon material according to the present invention comprises the steps of: providing 60 to 90 parts by weight of an organic substance containing α-cellulose as a main component; Sheet forming step of dispersing 10 to 40 parts by weight in water to make paper, immersing the formed sheet in a thermosetting resin solution with a residual carbon ratio of 40% or more, semi-curing, and heating the required number of semi-cured sheets A primary molding step of laminating under compression, a secondary molding step of laminating a plurality of primary molded bodies under heat compression with the same semi-cured sheet interposed on the joining surface as in the above step, and the obtained secondary molding It is characterized in that it comprises a carbonization step in which the body is calcined and carbonized at a temperature of 800 ° C. or more in a non-oxidizing atmosphere.

Hereinafter, each step will be described in detail. (1) Sheet Forming Step The organic material mainly composed of α-cellulose as a main raw material of the present invention becomes a filler component of a sheet during papermaking, and contains 90% of α-cellulose content in addition to ordinary wood pulp. Rayon pulp can be used. As the pulp properties, it is preferable to select a pulp having a fiber shape having a thickness of 3 to 10 deniers and a length of 5 to 10 mm from the viewpoint of ensuring paper formability and high pore structure. The water-soluble papermaking binder is a component that functions as a binder for sheet formation in the papermaking process. For example, softwood pulp such as red pine, spruce pine, fir pine, larch, fir, hemlock and the like are suitably used.

The mixing ratio of the raw materials is set in the range of 60 to 90 parts by weight of the organic substance mainly composed of α-cellulose and 10 to 40 parts by weight of the water-soluble paper binder. If the amount of the water-soluble paper binder with respect to the organic substance falls below the above range, the papermaking moldability deteriorates, and if it exceeds the range, the formation of a porous structure is inhibited.

In the sheet forming step of the present invention, the above-mentioned two-component raw materials are mixed and dispersed in water, and then formed into a sheet by using an appropriate papermaking apparatus such as a long net type or a round net type. The process is performed.

(2) Primary forming step Next, the formed sheet is immersed in a thermosetting resin solution having a residual carbon ratio of 40% or more. The residual carbon ratio of thermosetting resin refers to the weight percent of carbon remaining when the resin is fired at a temperature of 800 ° C in a non-oxidizing atmosphere. If this is less than 40%, the resulting porous carbon It becomes difficult to improve the strength of the material to a practical level. Thermosetting resins with a residual carbon ratio of 40% or more include phenolic resins, furan resins,
A polyimide resin or the like can be used, and all of them have a function of being converted into a glassy carbon structure after firing and carbonizing to increase the skeletal strength of the structure. The organic solvent used for the solution of the thermosetting resin is selected according to the type of the resin, but usually has a low viscosity such as methanol, ethanol, acetone, and methyl ethyl ketone, has high permeability, and easily evaporates. Are applied. If the resin concentration of the solution is less than 5% by weight, the strength properties decrease, and if the resin concentration exceeds 40% by weight, the viscosity increases and impregnation property is impaired, and pores are clogged to adjust porosity and pore diameter. It will be difficult to do. Therefore, it is desirable to set the resin concentration in the range of 5 to 40% by weight.

The sheet after the immersion treatment is passed through a drier maintained at a temperature of 50 to 150 ° C. to volatilize and remove unreacted substances such as moisture and reaction products together with an organic solvent component, and at the same time, a resin component supported on the sheet. Is semi-cured. Subsequently, a required number of semi-cured sheets are laminated, and lamination molding is performed while uniformly heating the entire surface. If the number of laminations is too large, heating is not performed up to the center, and uneven curing due to a temperature difference is likely to occur, which causes warpage of the primary molded body, swelling and cracking during firing and carbonization, and the like. Suitable lamination conditions are to adjust the number of laminated semi-cured sheets so that the thickness as a primary molded body is within 40 mm. It is industrially advantageous for the lamination molding operation to employ a method of hot pressing with a hydraulic press or a pneumatic press via a flat heating plate. The temperature at the time of molding is slightly different depending on the properties of the resin, but the molding is carried out smoothly within a range of about 80 to 200 ° C., and at the same time, the resin is cured. In this molding stage, the thickness of the semi-cured sheet is 70-20% of that before compression.
It is desirable to provide a compression condition such that the compression ratio becomes as follows. Practical strength performance is difficult to obtain with a low compression ratio of about 70% or less, while a high compression rate of less than 20% results in a denser structure and reduced porosity. .

(3) Secondary Forming Step Next, laminate molding is performed under heating and compression with the same semi-cured sheet used in the primary forming step interposed between a plurality of primary molded bodies. The semi-cured sheet in this step functions as a layer member for joining the primary molded bodies to be laminated. The lamination molding operation is generally performed in accordance with the primary molding process.However, if the compression ratio of the interposed semi-cured sheet becomes larger than the compression ratio in the primary molding process, the structure density of the joining layer portion increases and the material structure becomes uneven. Conversely, if the compression ratio is extremely smaller than the compression ratio in the primary molding step, phenomena such as interface peeling and breakage will occur during use or processing due to insufficient bonding force. Therefore, the compression of the semi-cured sheet at this stage is less than the compression ratio during the primary molding process.
It is preferable to set the value in the range of 80 to 100%.

(4) Carbonization step The obtained secondary compact is transferred to a firing furnace maintained in a non-oxidizing atmosphere such as nitrogen, argon, carbon dioxide, etc.
Bake at a temperature of 800 ° C or higher. At this stage, the heat volatilization component is volatilized, and at the same time, the thermosetting resin component is carbonized and converted into glassy carbon. In addition, the carbonization step includes:
When the secondary molded body is sandwiched between graphite plates having a smooth surface and given an appropriate weight while being held in a pressurized state, the occurrence of thermal deformation such as warpage can be prevented. The applied pressure is slightly different depending on the thickness of the secondary molded article to be treated, but is preferably set in the range of 15 to 50 g / cm ² . If it is less than 15 g / cm ² , the effect of weight will not be exhibited, and 50
If it exceeds g / cm ² , the porosity decreases due to the collapse of the tissue.

[0017]

According to the present invention, first, the molded sheet obtained in the sheet molding step is laminated and hot-pressed at the stage where the impregnated resin component is semi-cured in the primary molding step, and is molded into a plate-like molded body having a constant thickness. The number of semi-cured sheets to be laminated in this primary molding step can be appropriately adjusted within a range in which the heating effect sufficiently reaches the central part during molding, so that molding always proceeds smoothly and primary molding of a uniform structure Formed as a body. In the subsequent secondary molding step, a plurality of sheets are laminated and hot-pressed with a semi-cured sheet of the same composition interposed in the subsequent secondary molding step, and the secondary molding is formed to a desired thickness after carbonization via the bonding layer. Get the body. Through these primary molding and secondary molding processes,
A thick and homogeneous structure forming precursor is formed.

In the carbonization step, the organic matter containing α-cellulose as a main component in the secondary molded product is mostly volatilized by heat and contributes to the formation of pores, and at the same time, a part thereof remains carbonized to form a tissue skeleton. I do. In addition, the thermosetting resin impregnated in the sheet is carbonized and converted into glassy carbon, and adheres to the above-mentioned tissue skeleton to fulfill the function of enhancing the tissue strength. At this time, since the primary molded body and the layer for joining the primary molded body are sheets having the same composition, the carbonized material is a porous carbon material having a uniform uniform structure as a whole after carbonization.

By such a series of actions, it is possible to efficiently produce a porous carbon material having a thickness of more than 50 mm while having a high tissue strength while having a uniform and fine porous property.

[0020]

【Example】

Examples 1 to 7 (1) Sheet forming process 80 parts by weight of rayon pulp (manufactured by Daiwa Spinning Co., Ltd.) having a thickness of 5 denier and a length of 25 mm, and 20 parts by weight of bleached softwood pulp (NBKP) were stirred and mixed in water. After being uniformly dispersed, the paper is formed using a fourdrinier paper machine, dried, and dried to 200 mm length and width.
A sheet having 0.21 mm and an average pore diameter of 100 μm was formed.

(2) Primary molding step The molded sheet is sufficiently immersed in a 20% by weight solution of a phenolic resin ("Sumilite Resin PR940" manufactured by Sumitomo Durez Co., Ltd.) having a residual carbon ratio of 45% dissolved in acetone. Continue 1
The impregnated resin component was semi-cured in a dryer maintained at 00 ° C. Then, the sheets in the semi-cured state are laminated, and
Was placed on a temperature-controlled soaking plate and compressed from above to form a primary molded body (flat plate). In this case, the compression ratio is 40-65
The compression conditions were set so as to vary in the range of%.

(3) Secondary molding step A plurality of primary molded articles are heated to a temperature of 120 ° C., laminated with the semi-cured sheet used in the primary molding step interposed between the interfaces, and compressed. A secondary formed body (thick flat plate) was formed under the same conditions as in the primary forming step except that the ratio was changed.

(4) Carbonization Step The obtained secondary molded body is sandwiched between graphite plates having a smooth surface and packed in an electric firing furnace under a certain load, and the periphery is covered with coke packing. 10 under oxidizing atmosphere
A calcined carbonization treatment was performed at a temperature of 00 ° C.

Various characteristics were measured for each of the porous carbon materials manufactured as described above, and the results are shown in Table 1 in comparison with the fluctuation conditions at the time of manufacturing. Among various properties, the average pore diameter and porosity are determined by a mercury intrusion method, the bulk density is JIS R7222, and the specific resistance is JIS R7.
202, the bending strength was measured according to JIS K6911, respectively. The structure was observed visually and by scanning electron microscope.

[0025]

[Table 1]

From the results shown in Table 1, each of the porous carbon materials of each example exhibited good pore properties and structural strength despite having a thickness exceeding 50 mm. However, in Example 5 in which the number of laminated semi-cured sheets during the primary forming step was extremely large, the bending strength was reduced, and the structure was warped or swelled, and the sheet forming compression ratio in the secondary forming step was lower than that in the primary forming step. In the large embodiment 6, the density of the bonding layer portion is increased, the homogeneity of the material is reduced, and the pressure applied during the carbonization process is 15 g / cm ^2.
In Example 7 below, a decrease in strength and warpage of the structure were observed.

[0027]

As described above, according to the present invention, it is possible to efficiently produce a porous carbon material having excellent porosity and tissue strength and having a thickness exceeding 50 mm.
Therefore, it is extremely useful for applications such as industrial filter materials, large-sized adsorbents, and heat insulating materials.

Claims (2)

(57) [Claims] An organic substance containing α-cellulose as a main component.
A sheet forming process in which 60 to 90 parts by weight and a water-soluble papermaking binder are dispersed in water to form a paper by dispersing 10 to 40 parts by weight in water. The molded sheet is half-cured after being immersed in a thermosetting resin solution having a residual carbon ratio of 40% or more. A primary molding step of laminating and molding the required number of the semi-cured sheets under heat compression; and a laminating and molding of a plurality of primary molded bodies under heat compression with the same semi-cured sheet interposed in the bonding surface as in the above step. A method for producing a thick porous carbon material, comprising: a next forming step; and a carbonization step of firing and carbonizing the obtained secondary formed body at a temperature of 800 ° C. or more in a non-oxidizing atmosphere. 2. The compression ratio of the semi-cured sheet in the primary molding step is reduced.
Performed under the condition of 70 to 20%, and the compression ratio of the semi-cured sheet in the secondary molding process is 80 to 80% of the compression ratio of the primary molding process.
100%, carbonization process 15 ~ 50g / cm
^2. The method for producing a thick porous carbon material according to claim 1, wherein the method is performed while applying a pressure load of ² .