JP3434538B2 - Method for producing glassy 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 glassy carbon material having a homogeneous and dense microstructure, and particularly a plate thickness of 5
The present invention relates to an industrial manufacturing method for producing a glassy carbon material having a thick wall shape exceeding mm with a good product yield.

[0002]

2. Description of the Related Art A glassy carbon material is a heterogeneous carbon material having a glassy dense structure structure, and is gas impermeable, wear resistant, corrosion resistant, self-lubricating and has a smooth surface as compared with general carbon materials. Since it is excellent in durability and robustness,
Utilizing these characteristics, it is useful for various industrial members in various fields such as battery electrodes, electrolysis electrodes, semiconductor manufacturing crucibles. In recent years, focusing on the property of non-contaminating material that does not allow fine particles to be separated from the tissue, it has been put to practical use in the semiconductor field such as electrodes for plasma etching of silicon wafers and members for ion implantation equipment where contamination is disliked. ing.

Generally, a glassy carbon material is produced by a method of molding a thermosetting resin liquid having a high carbonization residual ratio such as a phenol type and / or furan type, and firing and carbonizing the cured molded body in a non-oxidizing atmosphere. To be done. Since the firing carbonization process in this process proceeds in the solid phase, the volatile components generated in large quantities by the thermal decomposition of the resin molded product are discharged to the outside of the solid phase, and the process of converting into the carbide while the volume shrinks is followed. However, if the resin molded body is thick, pyrolysis gas, condensed water, etc. are not smoothly discharged from the molded body and remain in the tissue, which causes generation of pores and voids, and This causes defects such as swelling and cracking of the material. Therefore, it has been difficult to industrially manufacture a glassy carbon material having a plate thickness of 3 mm or more by the conventional technique.

As a means for solving such a problem,
For example, fibers having a low carbonization yield such as animal fibers, plant fibers, and synthetic fibers are arranged in a layer with a thermosetting resin to form a plate, and by carbonizing this, a glassy carbon plate having a wall thickness of 3 mm or more A method for manufacturing a
63-129070). However, this method cannot discharge the volatile gas components generated from the thermosetting resin in a low temperature range until the fiber layer is pyrolyzed, so that unless the condition control during firing and carbonization is adjusted very strictly, there is a defect. The appearance of the organization is inevitable. In addition, the glassy carbon material manufactured by interposing the fibrous substance of this kind has a drawback that the material is likely to be inhomogeneous because the material is not a single structure, especially for applications requiring a uniform material structure. However, there is a shortage of properties.

The inventors of the present invention, as an alternative technique for producing a thick plate-like glassy carbon material, use a phenol resin having a molecular weight of 100 or more, a viscosity of 1 to 100 poise and a gelation time of 5 to 60 minutes in an amount of 50 to 100. A method has already been developed in which heat treatment is carried out in the temperature range of ℃ for 5 hours or more, followed by molding and curing, followed by firing and carbonization in an atmosphere of non-oxidizing gas (Japanese Patent Laid-Open No. Hei 4)
-362062 publication).

[0006]

According to the above-mentioned prior art, it becomes possible to manufacture a thick glassy carbon material having a single structure having a thickness of more than 4 mm without causing a material defect. However, if the plate thickness exceeds 5 mm, many material abnormalities such as cracking, chipping, and swelling of the structure occur in the firing and carbonization stage, and there is a problem that product yield is reduced.

An object of the present invention is to solve the above problems and provide an industrial production method for producing a glassy carbon material having a plate thickness of 5 mm or more excellent in a homogeneous and dense structure with a good product yield. Especially.

[0008]

In order to achieve the above object, a method for producing a glassy carbon material according to the present invention comprises forming a thermosetting resin liquid having a composition mainly composed of a phenolic resin and heating and curing it. Afterwards, 800 ℃ in a non-oxidizing atmosphere
In the method of firing and carbonizing at the above temperature, the steps from molding of the thermosetting resin liquid to heat curing are carried out at an oxygen concentration of 25 to 7
The structural feature is that it is performed in an oxidizing atmosphere of 0% by volume.

The raw material of the present invention is a thermosetting resin liquid having a composition mainly composed of a phenolic resin, and the raw material system thereof is a phenolic resin having a molecular weight of 100 or more and a gelation time of 5 to 60 minutes. Alternatively, it is preferable to use a resin composition in which the derivative compound is mixed. Molecular weight 10
A phenol resin having a molecular weight of 0 or more is effective for obtaining a glassy carbon material having a high structural strength, and a molecular weight of less than 100 does not convert into a high-strength carbide because the crosslinked structure after curing becomes weak. The reason for selecting a property resin having a gelation time in the range of 5 to 60 minutes is that in a normal liquid thermosetting phenolic resin that gels in less than 5 minutes, the progress of curing is too rapid and unreacted substances and condensed water volatilize. Since it does not stay, it promotes the generation of a large amount of pores, and on the other hand, the gelation time of more than 60 minutes requires a long time for the curing process, which hinders industrial production and also causes a contamination phenomenon from the outside during the curing process. Is likely to occur.

Mixing furan or a derivative compound thereof with a phenol resin having the above properties to give a two-component resin composition is an element for improving the carbonization yield at the time of carbonization by firing, and is usually 40 to 40%. It is possible to improve the carbonization yield of 60% to 65-75%. As the furan derivative compound, those having a furan ring in the chemical structure and compatible with the phenol resin are used. Typical compounds include furfuryl alcohol, furfural, and furancarboxylic acid methyl ester, which may be used alone or in combination of two or more. The mixing ratio of these furan-based components to the phenol resin is appropriately determined according to the resin properties, but is generally 5 to 50% by weight.
It is set within the range of.

The above resin composition prepared by mixing a furan-based component with a phenol resin has a viscosity of 1 to 100 poise and a resin content of 5
It gives excellent results when it has a property of 0% or more. That is, when the viscosity is less than 1 poise, the structural strength after carbonization is lowered, and when it exceeds 100 poise, volatilization of condensed water does not proceed smoothly during curing and many pores occur. Further, if the resin content is less than 50%, a large amount of unreacted components will be contained during curing, which will cause material abnormalities such as cracking during the carbonization and firing stage.

The thermosetting resin liquid is molded into a desired plate shape in consideration of the shrinkage ratio so that the finally obtained glassy carbon material has a wall thickness of 5 mm or more, and is heat-cured. For molding, means such as molding, injection molding, cast molding, and multiple molding (overcoating) can be applied.

The main constituent feature of the present invention is that the steps from molding of the thermosetting resin liquid to heat curing are carried out in an oxidizing atmosphere in which the oxygen concentration is in the range of 25 to 70% by volume, more preferably 25 to 60% by volume. It is in place. Oxygen concentration is 25
If it is less than 70% by volume, the progress of the smooth condensation reaction in the molding / curing process is hindered, while if it exceeds 70% by volume, the resin component serving as the carbon source is oxidized and the residual carbon rate is reduced. Also in this case, it becomes impossible to obtain a glassy carbon material having a uniform denseness and a thickness exceeding 5 mm with a good product yield. The heating temperature during molding and curing is 350 ° C. or lower, preferably 80 to 300 ° C.

In addition, in the molding and curing process,
It is desirable to adjust the conditions so that the structure after firing and carbonization has a pore diameter of 10 μm or less and a pore content of 5% or less. If there are many pores inside the structure during the molding and hardening stages, the bubbles will expand due to the heat treatment in the firing and carbonization process, which will cause cracking and swelling of the material. Then, the application range is greatly restricted.

The resin molding thus formed is
It is packed in a heating furnace kept in a non-oxidizing atmosphere and subjected to calcination and carbonization treatment in a temperature range of 800 ° C. or higher. The material after firing and carbonization is
2000 ° C under the same non-oxidizing atmosphere as above if necessary
Graphitization is performed at the above temperature to obtain a thick glassy carbon material.

[0016]

[Function] Generally, in the curing reaction of a thermosetting resin, a decomposition condensation reaction of a methylol group, a dimethylene ether bond, etc. occurs in an initial low temperature region, and then a hydroxyl group, a methylene bond, etc. are thermally decomposed. Most of the condensation reaction proceeds while generating condensed water. If the steps from molding to curing are carried out in an oxidizing atmosphere with a high oxygen concentration, the condensation reaction is activated and the initial stage proceeds smoothly. The present invention skillfully utilizes this reaction activation function, and the most suitable oxygen concentration in this case is 25-70.
By setting the volume% range, it is possible to efficiently produce a homogeneous and dense glassy carbon material having a wall thickness of more than 5 mm.

Further, as a thermosetting resin liquid mainly composed of a phenolic resin as a raw material, furan or a derivative compound thereof is added and mixed to a thermosetting phenolic resin having a property that it is converted into a homogeneous and dense glassy carbonized structure, and the viscosity and the like. By using the composition in which is adjusted, the product yield of the thick glassy carbon material can be further improved.

[0018]

【Example】

Examples 1 to 3 and Comparative Examples 1 to 3 Phenol purified by vacuum distillation and formalin were subjected to an addition condensation reaction in the presence of ammonia to prepare a phenol resin initial condensate having a molecular weight of 132 and a gelation time of 14 minutes. Add 3 parts of furfuryl alcohol to this phenol resin solution.
0% by weight was added and mixed to prepare a resin composition having a viscosity of 40 poise and a resin content of 55%.

This resin composition was poured as a raw material resin liquid into a polypropylene vat, put in a vacuum desiccator, deaerated under a reduced pressure of 10 torr or less, and then transferred to a clean electric oven maintained at a predetermined oxygen concentration. 100
Molded and heat-cured at a temperature of ℃ 100
A plate-shaped molded body having a thickness of 7 mm and a thickness of 7 mm was obtained. This plate-shaped compact is sandwiched between high-purity graphite plates with an impurity content of less than 5 ppm [G347SS, manufactured by Tokai Carbon Co., Ltd.], and a packingless high-temperature heating furnace equipped with a high-purity graphite heater [Tokai High Heat Industrial Co., Ltd.] Manufactured by TP150] and heated to 2000 ° C. while maintaining the atmosphere in the furnace with high-purity argon gas containing less than 10 ppm of impurities to carry out calcination carbonization. Various properties of each of the obtained glassy carbon plates and the yield (20 samples) during firing and carbonization were measured, and the results are shown in Table 1 in comparison with the oxygen concentration in the atmosphere of the molding / curing process.

[0020]

[Table 1]

Examples 5-6, Comparative Examples 4-5 In the same manner as in Example 1, a phenol resin initial condensate having a molecular weight of 122 and a gelation time of 5 minutes was added to furfuryl alcohol 30.
A resin composition having a viscosity of 3 poise and a resin content of 55% was prepared by adding and mixing wt%. Using this resin composition as a raw material, a thick glassy carbon material was manufactured under the same conditions as in Example 1 except that the oxygen concentration in the molding / curing process atmosphere was changed. Various property characteristics of each of the obtained glassy carbon materials and the yield (20 samples) at the time of carbonization by firing were measured, and the results are shown in Table 2 in comparison with the oxygen concentration in the atmosphere of the molding / curing process to which they are applied.

[0022]

[Table 2]

From the results shown in Tables 1 and 2, each of the glassy carbon materials produced in the examples satisfying the requirements of the present invention is substantially a thick plate having a thickness of more than 5 mm, but substantially has pores and textures. It has homogeneous and dense material properties with no defects and has high strength, and the product yield is also excellent. On the other hand, in the comparative examples that deviate from the conditions of the present invention, the denseness of the material deteriorates, and a crack or swelling phenomenon occurs in a part of the material structure, and the yield during firing and carbonization decreases. .

[0024]

As described above, according to the present invention, the simple process improvement of keeping the oxygen concentration of the atmosphere system within a specific range during the steps from the molding of the raw material resin to the heating and curing makes it possible to obtain a high-strength and excellent homogeneous dense structure. It becomes possible to efficiently manufacture a thick plate-like glassy carbon material including the above. Therefore, it is extremely useful as an industrial manufacturing technology for glassy carbon materials for members for the semiconductor field and the like, which require a thickness of more than 5 mm and high material properties.

Claims (2)

(57) [Claims] 1. A thermosetting resin in which a thermosetting resin liquid having a composition mainly composed of a phenolic resin is molded, heat-cured, and then calcined and carbonized at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. A method for producing a glassy carbon material, characterized in that the steps of molding the liquid to heat curing are performed in an oxidizing atmosphere having an oxygen concentration of 25 to 70% by volume . 2. A thermosetting resin liquid mainly composed of a phenolic resin, wherein a phenol resin having a molecular weight of 100 or more and a gelation time of 5 to 60 minutes is mixed with furan or a derivative compound thereof to have a viscosity of 1 to 100 poises. The method for producing a glassy carbon material according to claim 1, wherein the resin composition has a content of 50% by weight or more.