JP2008156145A - Method for manufacturing porous carbon material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous carbon material which has a large pore diameter and a high porosity, specifically a pore diameter of ≥60 μm and a porosity of ≥75%, and an excellent handleability. <P>SOLUTION: The porous carbon material is manufactured by impregnating with a thermosetting resin solution a mixed paper prepared by mixing a cellulose fiber of 10-90 pts.wt., a thermovolatile organic fiber of 10-90 pts.wt. to which the permeability of a thermosetting resin solution is low and a sheeting binder of 5-30 pts.wt. and sheeting, semi-setting, laminating to have a required thickness, and then firing at a temperature of ≥800°C in a non-oxidizing atmosphere. Preferably, the mixed paper is impregnated with the thermosetting resin solution so that the amount of adhesion of the thermosetting resin becomes 5-50 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a porous carbon material having a large pore diameter and a high porosity, for example, a porous carbon material having a pore diameter of 60 μm or more and a porosity of 75% or more.

  Carbon materials have excellent heat resistance and strength in a non-oxidizing atmosphere, and have high conductivity, thermal conductivity, and chemical stability, and are widely used as various industrial materials. Carbonized carbon materials are lightweight and widely used as filters, heat insulating materials, catalyst carriers, electrode materials for fuel cells, and the like.

  As a technique for producing a porous carbon material, a sheet obtained by papermaking carbon fiber together with pulp is impregnated with a thermosetting resin solution, laminated, cured, molded and fired and carbonized (for example, Patent Document 1) ) Has been known for a long time. However, since this method uses expensive carbon fibers, the manufacturing cost increases, and it is difficult to control the pore properties.

  In order to eliminate this difficulty, a method of using an organic fiber for carbon fiber production instead of carbon fiber, impregnating an organic polymer substance into a paper sheet made by blending pulp and the like, and then performing a baking process (for example, patents) Document 2) has been proposed. However, according to this method, a locally closed void portion is easily formed in the tissue, and it is difficult to obtain a homogeneous and controlled pore property.

  In view of this, a method has been developed in which an inexpensive organic papermaking sheet mainly composed of cellulose is impregnated with a thermosetting resin solution, and the resin-impregnated sheet is laminated to perform hot pressing and firing carbonization. For example, Patent Document 3 discloses a step of making a sheet by making a thermally volatile material mainly composed of α-cellulose, a step of impregnating the sheet with a thermosetting resin solution, and heating the impregnated sheet to be semi-cured. There has been proposed a method for producing a porous carbon material comprising a step of performing, a step of laminating a semi-cured sheet and compressing while heating, and a step of firing and carbonizing.

Patent Document 4 discloses a sheet forming step of making paper by dispersing 60 to 90 parts by weight of an organic substance containing α-cellulose as a main component and 10 to 40 parts by weight of a water-soluble papermaking binder in water, and forming a residual carbon ratio of the formed sheet. A primary molding step of immersing in a 40% or more thermosetting resin solution and then semi-curing and laminating the required number of the semi-cured sheets under heat compression, and a plurality of primary molded bodies in the same half as the above-mentioned steps A secondary molding step in which a cured sheet is interposed in the joining surface and laminated and molded under thermal compression, and a carbonization step in which the obtained secondary molded body is calcined and carbonized at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. A method for producing a thick porous carbon material has been proposed.
JP-A-53-018603 JP 61-012918 A Japanese Patent Laid-Open No. 03-183672 Japanese Patent Laid-Open No. 05-051280

  In general, the porous properties required for a porous carbon material vary depending on its application. For example, in a gas diffusion layer, a filter or a catalyst carrier of a fuel cell, the porous carbon material has a large pore diameter and a high porosity. The demand for is strong.

  However, the porous carbon material produced by the above prior art has a pore diameter and a porosity which are not sufficient. For example, a porous carbon material having a porosity such that the pore diameter exceeds 60 μm and the porosity exceeds 75% is used. It is difficult to manufacture. If a carbon material having a high pore diameter and a high porosity is simply produced, it is possible to some extent by reducing the pressing pressure when forming a laminate of resin-impregnated sheets, but the resulting porous carbon The material is easily peeled between the layers, and the material becomes brittle and becomes impractical.

  Therefore, the present inventor has intensively studied to solve the above problems, and has a large pore diameter and high porosity by using a mixed paper mixed with a specific heat-volatile organic fiber, and has excellent handling properties. It was found that a porous carbon material having the same material properties can be produced.

  That is, the present invention has been completed based on this finding, and its purpose is to provide a porous carbon material having a large pore diameter and a high porosity, specifically, a pore diameter of 60 μm or more and a porosity of 75% or more. It is to provide a method for producing a porous carbon material having good handling properties.

  The method for producing a porous carbon material according to the present invention for achieving the above object comprises 10 to 90 parts by weight of cellulose fibers and 10 to 90 parts by weight of thermally volatile organic fibers having low permeability of the thermosetting resin solution. Part, a mixed paper made by mixing 5 to 30 parts by weight of a papermaking binder, impregnated with a thermosetting resin solution and semi-cured, then laminated to a desired thickness and cured, and then non-oxidized It is structurally characterized to be fired at a temperature of 800 ° C. or higher in a neutral atmosphere.

Moreover, in the said structure, it is preferable to impregnate a thermosetting resin solution to a mixed paper so that the adhesion amount of the thermosetting resin to a mixed paper may be 5-50 g / m < ² >.

  According to the present invention, a large pore size and a high porosity can be obtained by using a mixed paper obtained by mixing and making cellulose fiber and a low volatility organic thermosetting fiber and a paper binder with a specific ratio. For example, it is possible to produce a porous carbon material having a pore diameter of 60 μm or more and a porosity of 75% or more and having excellent handling properties.

  The mixed paper impregnated with the thermosetting resin solution is a paper obtained by mixing cellulose fibers, thermally volatile organic fibers, and a papermaking binder.

  Cellulose fibers can be used regardless of fiber diameter, fiber length, cross-sectional shape, etc., as long as they are cellulose fibers such as pulps such as wood pulp and rayon pulp, and regenerated fibers. Note that 10 to 90 parts by weight of the cellulose fiber is an indispensable component that forms a skeleton of the porous carbon material together with the thermosetting resin, and the strength is weak when it is less than 10 parts by weight. This is because the shape retention is lost, and when it exceeds 90 parts by weight, the porosity is lowered.

  The heat-volatile organic fiber needs to have low permeability of the thermosetting resin solution. The thermally volatile organic fiber is a substance that volatilizes, decomposes and disappears during firing, which is a process for producing a porous carbon material, and forms a void to form a porous property. Cellulose fibers also have the property of volatilizing when heat-treated, but when impregnating the thermosetting resin solution, in order to absorb the thermosetting resin solution up to the inside of the fiber itself, All remains without being volatilized and removed, and on the other hand, a part of the skeleton is formed as a carbide after calcination, and the voids of the porous carbon material are closed, and the porosity is deteriorated.

  Therefore, in the present invention, the use of a thermally volatile organic fiber having low wettability with the thermosetting resin solution and low permeability to the inside of the fiber, the fiber itself is impregnated when impregnating the thermosetting resin solution. Very little resin solution is absorbed and taken into the interior. Therefore, most of the thermally volatile organic fiber is volatilized and removed after firing, so that the amount of carbide remaining after firing becomes extremely small, and the deterioration of the pore property can be effectively suppressed.

  This thermally volatile organic fiber must be insoluble in a dispersion medium such as water when mixed paper is made, and insoluble in a solvent that dissolves the thermosetting resin when impregnated with the thermosetting resin solution. . Further, a resin that does not soften or melt at a temperature of about 50 to 150 ° C. at which the resin is semi-cured is used.

  Examples of such thermally volatile organic fiber include polypropylene fiber, polyolefin fiber, polyester fiber, polyethylene fiber, and nylon fiber. When the mixed paper is made, the weight ratio of the thermally volatile organic fiber is 10 to 90 parts by weight. When the weight ratio is less than 10 parts by weight, the porosity and the pore diameter are lowered. Increasing the strength decreases, making it unusable for handling.

  The papermaking binder functions as a binder between cellulose fibers and thermally volatile organic fibers at the time of papermaking, and is used to enhance the handling properties of the mixed paper. As the papermaking binder, for example, softwood pulps such as red pine, spruce, todomatsu, larch, fir, and tsuga are used. The reason why the weight ratio of the papermaking binder is 5 to 30 parts by weight is that 5 parts by weight or more is necessary to ensure the handling property of the mixed paper, while if it exceeds 30 parts by weight, the gap of the mixed paper is reduced. In addition, the pore diameter and porosity of the porous carbon material are lowered.

  These cellulose fiber, thermally volatile organic fiber, and papermaking binder are dispersed in an aqueous medium in a desired weight part ratio within the above-mentioned parts by weight, and the aqueous dispersion may be a long mesh type or a round net type. After mixed paper making with a wet paper machine, it is dried to produce mixed paper.

  Next, the mixed paper is impregnated with the thermosetting resin solution. The thermosetting resin to be impregnated is used with a high residual carbon ratio, for example, phenolic, furan or polyimide resins having a residual carbon ratio of 40% by weight or more, and these thermosetting resins are used in combination. A thermosetting resin solution is prepared by dissolving in an appropriate organic solvent. As the organic solvent, alcohols that do not dissolve cellulose fibers, thermally volatile organic fibers and papermaking binders and have low viscosity and high permeability are suitable, and the resin concentration is adjusted to an appropriate concentration in consideration of impregnation properties and the like. . The impregnation of the mixed paper with the thermosetting resin solution is performed by immersing the mixed paper in the thermosetting resin solution or by applying the thermosetting resin solution to the mixed paper.

  The mixed paper impregnated with the thermosetting resin solution is heated to a temperature of about 50 to 150 ° C. depending on the resin type, and after semi-curing the resin component, it is laminated to a desired thickness, and is about 100 to 200 ° C. The resin component is cured by heating to a temperature. The resin component impregnated in the mixed paper and cured is baked and converted into glassy carbon, and the skeleton of the porous carbon material is reinforced to improve the strength.

In this case, the impregnation amount of the thermosetting resin solution is preferably impregnated so that the adhesion amount of the thermosetting resin to the mixed paper is 5 to 50 g / m ² . If the adhesion amount is less than 5 g / m ² , the amount of carbonization during firing is small, so that the strength of the porous carbon material is significantly reduced. On the other hand, if it exceeds 50 g / m ² , the amount of carbon after firing increases, and the porous carbon material As a result, the pore size and porosity are reduced.

  The cured laminate is baked at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere by a conventional method, and a porous carbon material is produced by carbonizing the thermosetting resin.

  Examples of the present invention will be specifically described below in comparison with comparative examples.

Example 1
Recycled rayon fiber (17DTEX × 10mm, manufactured by Daiwabo Rayon Co., Ltd.) as a cellulose fiber, polypropylene fiber (17DTEX × 10mm, manufactured by Daiwabo Polytech Co., Ltd.) as a thermally volatile organic fiber, and softwood pulp (NBKP) as a papermaking binder. An aqueous dispersion was prepared by stirring and mixing with 23000 parts by weight of water at a ratio of 50 parts by weight, 20 parts by weight of polypropylene fibers, and 30 parts by weight of softwood pulp. This dispersion was subjected to mixed paper making in accordance with a pulp test handsheet preparation method (JIS P8209).

A phenolic resin (Sumilite Resin PR940, manufactured by Sumitomo Bakelite Co., Ltd.) is used as the thermosetting resin, and a resin solution having a resin concentration of 20% by weight is prepared using methanol as the solvent. The amount of phenolic resin adhering to the above mixed paper Was impregnated at 45 g / m ² . Thereafter, the solvent was removed by air drying, and the phenol resin was semi-cured at a temperature of 150 ° C.

  Next, 6 sheets of this mixed paper were laminated, and a curing process was performed while pressing at 12O <0> C for 12 hours with a spacer interposed so as not to apply excessive pressure. Then, it put into the electric furnace of nitrogen atmosphere, baked and carbonized at the temperature of 1000 degreeC for 12 hours, and manufactured the porous carbon material.

Example 2
In Example 1, the porous material was made in the same manner as in Example 1 except that 30 parts by weight of the recycled rayon fiber, 40 parts by weight of polypropylene fiber, 30 parts by weight of the papermaking binder, and 5 sheets were laminated. Carbon material was manufactured. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated so as to be 40 g / m ² .

Example 3
In Example 1, the porous material was made in the same manner as in Example 1 except that the recycled rayon fiber of the papermaking material was 20 parts by weight, the polypropylene fiber was 50 parts by weight, the papermaking binder was 30 parts by weight, and the number of laminated sheets was 5. Carbon material was manufactured. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated to be 35 g / m ² .

Comparative Example 1
In Example 1, porous charcoal was produced in the same manner as in Example 1 except that 70 parts by weight of recycled rayon fiber as a papermaking raw material, 30 parts by weight of papermaking binder, no addition of polypropylene fiber, and the number of laminated sheets were 8. Made the material. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated so as to be 40 g / m ² .

Comparative Example 2
In Example 1, porous carbon was produced in the same manner as in Example 1, except that 70 parts by weight of the polypropylene fiber for papermaking, 30 parts by weight of papermaking binder, no added rayon fiber, and 4 laminated sheets were used. Made the material. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated so as to be 40 g / m ² .

Comparative Example 3
A porous carbon material was prepared in the same manner as in Example 2, except that the amount of phenolic resin adhering to the mixed paper was impregnated to be 55 g / m ^{2 in} Example 2.

Comparative Example 4
A porous carbon material was prepared in the same manner as in Example 2, except that the amount of phenol resin adhered to the mixed paper in Example 2 was impregnated to be 3 g / m ² .

Comparative Example 5
A porous carbon material was prepared in the same manner as in Example 1 except that 5 parts by weight of the polypropylene fiber for papermaking, 10 parts by weight of papermaking binder, 95 parts by weight of regenerated rayon fiber, and 5 laminated sheets were used. Manufactured. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated so as to be 40 g / m ² .

Comparative Example 6
A porous carbon material was prepared in the same manner as in Example 1 except that 95 parts by weight of the polypropylene fiber for papermaking, 10 parts by weight of papermaking binder, 5 parts by weight of regenerated rayon fiber, and 5 laminated sheets were used. Manufactured. In addition, the impregnation amount of the phenol resin to the mixed paper was impregnated so as to be 40 g / m ² .

With respect to these porous carbon materials, the pore diameter and the porosity were measured by the following methods, and the obtained results are shown in Table 1.
Measuring device: manufactured by Shimadzu Corporation, pore sizer 9320,
Measurement conditions: pressure 0-30 Psi, mercury surface tension 485 dyn / cm, mercury contact angle 130 °,
The porosity is calculated from the pore volume having a pore diameter of 300 to 10 μm.

  From Table 1, the porous carbon materials of Examples 1 to 3 all had a pore diameter of 60 μm or more, a porosity of 75% or more, and good handling properties. In contrast, the porous carbon material of Comparative Example 1 has a small pore diameter, and the porous carbon material of Comparative Example 2 has a problem in handling properties.

  In Comparative Example 3, the pore diameter and the porosity decreased due to the blockage of the pores by the resin, and the porosity was particularly decreased. In Comparative Example 4, both the porosity and the pore diameter were good, but peeling between the laminated layers was caused and the handling property was lowered.

  In the sample of Comparative Example 5, both the pore diameter and the porosity decreased. In Comparative Example 6, the handling property was remarkably deteriorated, and the pore diameter, the porosity measurement and the bending strength test with a mercury porosimeter could not be performed.

Claims (2)

  10 to 90 parts by weight of cellulose fiber, 10 to 90 parts by weight of thermally volatile organic fiber with low permeability of the thermosetting resin solution, and 5 to 30 parts by weight of paper-making binder are mixed into a mixed paper. A porous carbon material characterized in that it is impregnated with a curable resin solution and semi-cured, then laminated to a desired thickness and cured, and then fired at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. Manufacturing method. Adhesion amount of the thermosetting resin into the mixing paper is impregnated with a thermosetting resin solution to the mixed paper so that 5 to 50 g / m ^2, the production method of the porous carbon material according to claim 1, wherein.