JPH0633196B2 - Method for producing porous carbon material - Google Patents

Description

The present invention relates to a method for producing a porous carbon material having a high degree of pore structure and strength characteristics.

[Conventional technology]

A typical method for producing a porous carbon material is a method in which coke powder having a uniform particle size is kneaded with a binder such as tar pitch, and then crushed, molded, and fired. Since it is difficult to set the conditions for obtaining a stable porous structure, there is a drawback that mass productivity is poor.

In addition, a method of manufacturing a porous carbon plate using a carbon fiber skeleton has been developed. In this method, organic fiber for carbon fiber production and pulp, or a raw material in which carbonaceous powder is blended into paper is made into a sheet, and an organic polymer substance or a solution of an organic polymer substance in which carbonaceous powder is suspended is formed into a sheet. It is impregnated and then fired, and is suitable as an electrode material used in secondary batteries (Japanese Patent Laid-Open No. 61-236664, 61-236664).
236665 publication).

[Problems to be Solved by the Invention]

However, in the above method, since the organic fiber for producing carbon fiber used as a raw material is expensive and a complicated paper making process is required, there is a problem that the product cost rises.

The present invention provides a method for producing a high-performance porous carbon material at low cost by a simple process using inexpensive paper raw materials.

[Means for Solving the Problems]

That is, the method for producing a porous carbon material according to the present invention is a method in which a paper having an average pore diameter of 50 to 150 μm and a porosity of 50% or more is laminated to a predetermined thickness, and the residual carbon rate of 40% or more is applied to the paper. The constitutional feature is that after impregnating with a curable resin solution and heat-curing, firing and carbonization is performed in a temperature range of 1000 ° C. or higher in a non-oxidizing atmosphere.

The raw material of the present invention is a commercially available household paper leaf,
Among papers or paperboards made from paper pulp such as hybrid paper and corrugated cardboard, the average pore diameter is 50 to 150 μm, and the porosity is 5
Select and use one that has a property of 0% or more. If the average pore diameter and porosity of the raw paper are below 50 μm and 50%, respectively, it induces pore blockage in the subsequent steps from impregnation of thermosetting resin solution to firing and carbonization treatment, while When the pore size exceeds 150 μm, the strength characteristics are significantly deteriorated.

The raw papers are laminated so as to have a predetermined thickness, compressed if necessary, and then impregnated with a thermosetting resin solution by means of dipping, coating, spraying or the like.

At this time, if the raw material paper is heat-treated in advance in a temperature range of about 50 to 200 ° C. before being laminated to remove water and modify the surface, wetting with the resin solution is effectively improved.

As the thermosetting resin used for impregnation, it is necessary to select one having a residual carbon rate of 40% or more. Residual coal rate refers to the weight percentage of carbon content remaining when the resin is fired at 1000 ° C in a non-oxidizing atmosphere. If it is less than 40%, the strength of the resulting porous carbon material is improved to a practical level. It becomes extremely difficult to do so. Examples of the thermosetting resin having a seed residual carbon ratio of 40% or more include phenol formaldehyde, furfuryl alcohol, divinylbenzene and the like, all of which are effectively used for this purpose.

The thermosetting resin is made into a solution by dissolving the resin in a commonly used organic solvent such as alcohol or acetone, and the concentration of the solution is preferably set to 10 to 40% by weight. The reason for this is that when the concentration of the solution is less than 10% by weight, the strength characteristics are deteriorated, and when it exceeds 40% by weight, smooth impregnation is hindered and pores are clogged.

The impregnated material is then heat cured. A preferable condition of the heat curing treatment is to perform pre-curing at a temperature of about 80 ° C. for about 10 hours, and then raise the temperature to 180 to 300 ° C. to completely cure.

It is also possible to impregnate the thermosetting resin solution again at the pre-curing stage, or by repeating this operation, to adjust the structural characteristics such as density and porosity of the porous carbon material.

The heat-cured material is transferred to a firing furnace and subjected to a firing carbonization treatment at a temperature of 1000 ° C. or higher in a non-oxidizing atmosphere such as nitrogen, argon or carbon dioxide to obtain a porous carbon material.

[Work]

According to the present invention, the average pore diameter is 50 to 150 μm, and the porosity is 50%.
Paper with the above properties as the raw material base material, with a residual coal rate of 40
% Or more of the thermosetting resin solution is impregnated, the peculiar pore structure of the raw material base material and the binder function of the carbon content generated from the thermosetting resin solution act synergistically to produce fine particles. Realizes the formation of a high-strength porous carbon structure in which various breathable pores are uniformly distributed.

Further, when the concentration of the thermosetting resin solution is set to 10 to 40% by weight, the above action is further promoted, and a higher performance porous carbon material can be obtained.

〔Example〕

Hereinafter, the present invention will be described in comparison with examples and comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Hybrid papers (calligraphy paper) having different average pore diameters and porosities were placed in an electric dryer and heat-treated at a temperature of 100 ° C. for 12 hours. 40 sheets of raw paper after treatment are laminated in close contact (thickness: approx. 4 mm), and then phenol formaldehyde resin with a residual carbon rate of 45% [Sumilite Resin PR940] manufactured by Sumitomo Dures Co., Ltd.
It was immersed in a 20% by weight ethanol solution of 10% by weight to thoroughly impregnate the resin solution into the raw paper structure.

The impregnation is kept at a temperature of 80 ° C for 10 hours to pre-cure, and then again.
The thermosetting resin solution was impregnated and similarly pre-cured.
Subsequently, the temperature was raised to 180 ° C. and heat treatment was carried out for 1 hour to completely cure the impregnated resin.

Then, the material after curing is transferred to a firing furnace, and under a nitrogen atmosphere,
Firing and carbonization treatment was performed at a temperature of 1400 ° C. to obtain a porous carbon plate having a thickness of about 2.5 mm.

Various physical properties of each porous carbon plate thus obtained were measured and shown in Table 1 in comparison with the average pore diameter and porosity of the raw material paper used.

The respective properties were measured according to the mercury porosimetry method for average pore diameter and porosity, JIS K6911 for bending strength and flexural modulus, and JIS R7202 for apparent specific gravity and specific resistance.

The characteristics of the conventional porous carbon material using the organic fiber for carbon fiber as the raw material are also listed in Table 1 (conventional example).

Each of the examples of the present invention showed properties equal to or higher than the conventional example in strength, pore structure and specific resistance, but the comparative examples deviating from the average pore diameter or / and the porosity of the raw paper specified in the present invention are The performance was remarkably inferior.

Examples 4 to 6 and Comparative Examples 4 to 6, hybrid paper (calligraphy paper) having an average pore diameter of 60 μm and a porosity of 60% was used as a raw paper, and after heat treatment and lamination as in Examples 1 to 3, the residual carbon ratio was obtained. Further, the raw paper structure was sufficiently impregnated with the resin solution by immersing it in ethanol solutions of phenol formaldehyde resins having different concentrations.

Then, the impregnated material was pre-cured, re-impregnated, heat-cured and calcined under the same conditions as in Examples 1 to 3 to produce a porous carbon material.

The physical properties of each of the porous carbon materials thus obtained were measured and shown in Table 2 in comparison with the residual carbon rate and the solution concentration of the resin solution used.

From the results of Table 2, Comparative Example 4 in which the residual carbon content of the thermosetting resin is less than 40% has particularly low strength characteristics as compared with the examples of the present invention. Further, even when the residual coal rate was 40% or more, it was confirmed that in Comparative Examples 5 and 6 in which the concentration of the resin solution deviated from 10 to 40% by weight, the strength or the pore structure slightly deteriorated.

[Advantages of the Invention] As described above, according to the present invention, it is possible to manufacture a porous carbon material having a high degree of pore structure and strength characteristics by a simple manufacturing process using an inexpensive raw material base material. Therefore, it can be provided at low cost as a member such as a high temperature heat insulating structural material and an electrode material for a secondary battery.

Claims (2)

[Claims] 1. A paper having an average pore diameter of 50 to 150 μm and a porosity of 50% or more is laminated in a predetermined thickness, and the residual coal rate
A method for producing a porous carbon material, which comprises impregnating with 40% or more of a thermosetting resin solution, heat-curing it, and then firing and carbonizing it in a temperature range of 1000 ° C or more in a non-oxidizing atmosphere. 2. The method for producing a porous carbon material according to claim 1, wherein the concentration of the thermosetting resin solution having a residual coal rate of 40% or more is set to 10 to 40% by weight.