JP4836590B2 - Glassy carbon material and method for producing the same - Google Patents

Description

The present invention relates to a glassy carbon material and a method for producing the same, and more particularly to a glassy carbon material suitable for a fuel cell separator and a method for producing the same.
In the present specification, the term “glassy carbon material” may be used for a molded product molded using the same material or a product obtained by carbonizing and firing the molded product.

  Carbon materials are used as various industrial materials due to the excellent electrical characteristics, chemical characteristics, mechanical characteristics, etc. of the materials. Common carbon materials include graphite materials. Graphite materials have various excellent properties, but there are problems such as the phenomenon of tissue dropout due to pulverization, poor gas barrier properties, and machining that must be applied to form a structure. On the other hand, various methods have been tried to increase the functionality of graphite materials, and for example, those with improved performance such as resin-impregnated graphite materials have been proposed.

  On the other hand, there is a material called glassy carbon in the classification of carbon materials. This is also called amorphous carbon, and its appearance is black, glassy, and has a glossy shell with a glossy surface. It is hard, amorphous carbon, and has a very homogeneous and dense structure. In addition to the conductivity, chemical stability (especially acid resistance), and heat resistance that are the characteristics of general carbon materials, the material surface does not pulverize and fall off. Have different characteristics and are applied as various industrial materials.

  In general, since carbon materials are brittle materials, depending on the intended use, there is a case where the use of the materials is restricted due to the destruction of so-called materials that are cracked or cracked by tightening or pressing. As a method for improving the mechanical properties of the carbon material, for example, there is a method of improving the mechanical properties by adding a fibrous reinforcing material such as a C / C composite. However, since carbon fiber or the like is used as a reinforcing material, it leads to an increase in the cost of the product obtained, and the manufacturing method thereof is complicated. Moreover, it is difficult to manufacture a structure having a complicated shape. Therefore, it has been desired to improve the mechanical properties of the carbon material by a simple method. In particular, the glassy carbon material is superior in various mechanical properties as compared with the graphite material, but it may be easily broken because of its high rigidity, and an improvement thereof has been desired.

  In recent years, a fuel cell and a power generation system using the same have been expected as a next generation power generation device with low pollution and high power generation efficiency. The types include alkali type, phosphoric acid type, solid polymer type, molten carbonate type, and solid electrolyte type depending on the type of electrolyte. A fuel cell is composed of unit cells that generate an electromotive force by an electrochemical reaction between a hydrogen-containing gas and an oxygen-containing gas, and generally has a stack structure in which the unit cells are stacked. A carbon material is often used as a material of a member constituting a fuel cell because of its excellent characteristics. As a component, the unit is interposed between adjacent unit cells and contacts the electrodes of both unit cells. Examples thereof include a fuel cell separator (hereinafter sometimes abbreviated as “separator”) that has an action of electrically connecting cells and separating reaction gas. Some fuel cells that operate at relatively low temperatures, such as alkaline type, phosphoric acid type, and solid polymer type, have a groove for flowing cooling water on one side of the separator for the purpose of stabilizing the operating temperature. is there. Since the surface of the separator is exposed to strong acidity, a gas-impermeable carbon material having acid resistance and good conductivity is often used as the material. And it is common that the groove process for forming a gas flow path is given to the plate-shaped surface.

  A separator made of a graphite material, which is a carbon material, exhibits good performance as a member of a fuel cell because of the characteristics of the material. However, it is difficult to mold and process the graphite material, and it must be cut and processed into a shape, which is a high processing cost and is not an industrial technique. Accordingly, a method has been proposed in which a structure having a target shape is obtained by molding and processing using a thermosetting resin as a raw material, followed by carbonization firing. Since this technique can be molded, it is an industrially excellent technique. On the other hand, a plate-like separator made of the glassy carbon material has also been proposed. Although it is possible to perform cutting similar to that of a graphite separator, this is not an industrial technique. In addition, since glassy carbon has higher rigidity than graphite material, it may be desired to reduce its hardness to the same level as graphite material depending on the purpose of use.

  Various methods for modifying glassy carbon materials have been proposed. For example, Patent Document 1 describes a method in which specific element ions are implanted into the surface of a glassy carbon material to modify the carbon material and form a compressive stress layer on the surface. In Patent Documents 2 and 3, a carbon material having a turbostratic structure in a part of the structure is obtained by carbonizing after adding a metal compound to a raw material that generates non-graphitizable carbon, Proposals have been made to use this as an electrode catalyst for fuel cells. Patent Document 4 proposes a method of obtaining a graphite material by adding a transition metal salt to lignin and then carbonizing. Patent Document 5 proposes a graphite powder containing a substance containing a specific element as a highly functional carbon material.

  However, since the method described in Patent Document 1 is a method in which ions are implanted into a glassy carbon material and then only the surface portion is modified by processing, the carbon material has a complicated surface shape. Is difficult to adapt, and since the entire material is not modified, performance variations are likely to occur, and the desired mechanical properties may not be exhibited. According to the methods described in Patent Documents 2 and 3, it is possible to change the microstructure of glassy carbon, but it is difficult to adapt to a manufacturing method for obtaining a target structure by a method involving a molding process. For example, it can be said that it is difficult to apply to the industrial production of a fuel cell separator. Although the method described in Patent Document 4 is a method for producing a melt-moldable material, it is difficult to obtain a structure having a complicated shape directly because a starting material is a solution material. . Patent Document 5 proposes a method for obtaining carbon powder having excellent characteristics, but it is difficult to form a structure only from a carbon material.

As described above, Patent Documents 1 to 5 disclose methods for modifying glassy carbon, but none of them describes a method for modifying the mechanical properties of the structure.
Japanese Patent Laid-Open No. 03-122006 JP 2003-249231 A JP 2005-019332 A JP 2001-294757 A JP 2003-020418 A

  In view of this situation, an object of the present invention is to provide a glassy carbon material that can reduce mechanical properties, in particular, rigidity, and can produce a complicated shape by molding.

  As a result of diligent research to solve the above problems, the present inventors have reduced the elastic modulus of glassy carbon, and for that purpose, a specific metal compound is contained in a thermosetting resin and then carbonized. Thus, the inventors have found that the above problems can be overcome and have reached the present invention.

  That is, the gist of the present invention is a glassy carbon material characterized by a flexural modulus of 25 GPa or less, characterized in that it is the glassy carbon material described above and made of a carbide of a thermosetting resin composition. The glassy carbon material is obtained by carbonizing and baking a thermosetting resin composition containing 0.01 to 1.5% by mass of a higher fatty acid salt or complex of a transition metal as a metal component. It is characterized by being.

According to the present invention, the transition metal needs to be at least one selected from the group consisting of cobalt, nickel, iron, chromium and manganese, and the higher fatty acid is stearic acid, 12-hydroxystearic acid, montan. It is preferably at least one selected from the group consisting of acids, behenic acid, lauric acid, octylic acid, sebacic acid, undecylenic acid, ricinoleic acid, myristic acid and palmitic acid, and the complex is a phthalocyanine complex, acetyl It is preferable that it is at least one selected from acetonate complexes.

The gist of the separator for a fuel cell of the present invention is that it is formed of the glassy carbon material.
The manufacturing method of the glassy carbon material of this invention is a method for manufacturing said glassy carbon material, Comprising: It makes it a summary to include the process of shape | molding a thermosetting resin composition by injection molding.

  The glassy carbon material of the present invention is one in which the hardness of glassy carbon is reduced, that is, the bending elastic modulus of glassy carbon is lowered, and the glassy carbon having a low elastic modulus is excellent. Since it has excellent mechanical properties in addition to chemical properties, it can be used in various applications, and has an advantage that it can exhibit excellent performance as a fuel cell separator, for example.

Hereinafter, the present invention will be described in detail.
The glassy carbon material of the present invention is a material composed of glassy carbon and similar carbon, and it is necessary that the flexural modulus, which is an index of hardness, is 25 GPa or less. Glassy carbon, it is necessary that a carbon material comprising a carbide of the thermosetting resin composition. A carbon material produced using pitch or coke as a raw material is a graphite material, and its flexural modulus is 10 GPa or less, but the graphite material cannot be applied to the present invention. Since the carbon material of the present invention needs to have a low elastic modulus while having the excellent properties of a glassy carbon material, the flexural modulus needs to be 25 GPa or less, preferably 20 GPa. It is as follows.

  The thermosetting resin composition is a resin composition mainly composed of a thermosetting resin. Examples of the thermosetting resin include phenol resin, polyimide resin, melamine resin, furan resin, epoxy resin, carbodiimide resin, furfuryl alcohol resin, benzoxazine resin, urea resin, unsaturated polyester resin, and the like. Polymers can be used. Further, it may be one type of thermosetting resin, or a mixture of two or more types of thermosetting resins in which different types of resins are combined within a range that does not impair the properties other than the main component thermosetting resin. It doesn't matter. At this time, the resin mixed with the main component resin may be a low molecular weight product of the main component thermosetting resin, or may contain an additive for the purpose of improving processability, moldability and the like. Absent.

  Among these, it is most preferable to use a thermosetting resin containing a phenol resin as a main component in terms of moldability and cost. Furthermore, graphite particles, carbon black, inorganic particles, inorganic fibers, carbon fibers, carbon nanofibers, carbon nanotubes, fullerenes, glassy carbon, graphite, wood powder, cellulose particles for the purpose of improving other properties or fillers Further, it may contain a thermosetting resin cured product or the like. The thermosetting resin can be formed into a target shape by molding and curing, and can be carbonized and fired in that shape.

  Since the glassy carbon material of the present invention has a reduced hardness compared to a general glassy carbon material, it can be used as an industrial material in various applications. For example, the present invention can be applied to a fuel cell separator that is a constituent member of a fuel cell. The separator for a fuel cell has necessary properties such as electrical conductivity, gas barrier properties, and acid resistance, and can exhibit the characteristics of a glassy carbon material. At the same time, excellent performance is achieved by improving mechanical properties by lowering the elastic modulus.

The glassy carbon material of the present invention is produced by carbonizing and baking a thermosetting resin composition containing 0.01 to 1.5 mass% of a higher fatty acid salt or complex of a transition metal as a metal component. There is . The carbon material of the present invention changes the fine structure of a general glassy carbon material to lower the elastic modulus, and what plays the role is a transition metal atom. Since the transition metal atom is an atom having the ability to promote crystallization of carbon, that is, a catalyst ability, the transition metal atom is included in the thermosetting resin composition, and is subjected to carbonization and heat treatment. A carbon material can be obtained.

  As the higher fatty acid salt or complex of the transition metal, that is, the metal compound to be contained in the thermosetting resin composition, it is preferable to select a compound that does not release volatile components such as water molecules or the like with a small amount of heat treatment. When a thermosetting resin composition is processed into a desired shape by thermoforming or the like, the volatile component forms defects, making it difficult to obtain the desired molded body, or voids and cracks in the carbonization firing process. This is because the target structure cannot be obtained. Furthermore, since the higher fatty acid salt or complex of transition metal does not contain water of crystallization, it can be heated and dried and heated and melted, and can be processed into a particle shape. Has the advantage that there is no generation of bubbles and the like, and there are few defects such as bubbles in the carbonization process.

  As a method for incorporating a higher fatty acid salt or complex of a transition metal into the thermosetting resin composition, a melt-kneading method can be applied. The content is preferably 0.01 to 1.5% by mass as a metal component. When the content is less than 0.01% by mass, the ability of the transition metal to change the microstructure of the glassy carbon material becomes poor, and the required performance is hardly exhibited. Conversely, when it exceeds 1.5 mass%, the content of the transition metal compound to be contained becomes large, and it becomes difficult to produce a resin composition containing the transition metal compound. In addition, since the mass released as a volatile gas in the carbonization process for producing the target carbon material increases, the internal bubbles may become very large or the shape of the carbon material cannot be maintained due to defects. .

  In addition, it becomes possible to manufacture the carbon material of the target elasticity modulus by changing content of a metal atom component. That is, when the content of the metal atom component is increased within the above range, the elastic modulus is lowered and softened. On the contrary, when the content is decreased, the elastic modulus is increased and the degree of softness is lowered. For this reason, it is necessary to select content which expresses the target performance.

  The transition metal needs to be at least one selected from the group consisting of cobalt, nickel, iron, chromium, and manganese. These metal compounds are produced industrially and can be used. Moreover, since each metal atom has a specific catalytic ability, it is possible to select a metal atom according to the purpose. Further, only one metal component may be selected, or two or more metal components may be contained.

  The transition metal is preferably a compound in the form of a higher fatty acid salt. The higher fatty acid at this time is at least selected from the group consisting of stearic acid, 12-hydroxystearic acid, montanic acid, behenic acid, lauric acid, octylic acid, sebacic acid, undecylenic acid, ricinoleic acid, myristic acid, palmitic acid. One type is preferable. Higher fatty acid salts are industrially produced in various ways, and since the melting temperature, the metal component ratio, and the like vary depending on the type, those according to purposes can be selected. Of these, stearates are industrially produced most and are preferred from the viewpoints of moldability and cost.

  The transition metal may be a compound in the form of a complex. The complex is preferably at least one selected from a phthalocyanine complex and an acetylacetonate complex. This is because these are industrially produced compounds and can be applied to industrial products.

  Examples of the method for producing the glassy carbon material of the present invention include a method of molding a thermosetting resin composition containing a transition metal compound by injection molding, pressure molding, transfer molding or the like. Of these, injection molding is most preferable because the molding time can be shortened. Injection molding of a thermosetting resin composition is an industrially established molding technique that enables precise molding and can be applied to various industrial materials that are the object of the present invention. And the glassy carbon material of this invention can be manufactured by performing carbonization baking after shaping | molding.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.
In addition, all the metal compounds used in the following Examples and Comparative Examples have a metal oxidation number of II (+2).

Example 1
Using a phenol resin composition containing 2.0% by mass of nickel stearate in a random novolac phenolic resin (Unibex N type, manufactured by Unitika Co., Ltd.), using an injection molding machine MODEL FE80S12ASEK manufactured by Nissei Plastic Industry Co., Ltd., and injection molding. A test piece was obtained. This test piece was carbonized and fired at 1500 ° C. for 5 hours in a nitrogen atmosphere to obtain a test piece made of a glassy carbon material having a width × length × thickness = 4 mm × 40 mm × 2 mm. About this test piece, the 4-point bending elastic modulus was measured according to the method of JISR1601.

  The results are shown in Table 1.

Examples 2-5
A test piece made of glassy carbon material was obtained in the same manner as in Example 1 except for the conditions described in Table 1. That is, compared with Example 1, the metal compound and its addition amount were changed. The bending elastic modulus was similarly measured about the obtained test piece.

  The results are shown in Table 1.

Example 6
A random novolac phenol resin (Unibex N type manufactured by Unitika) containing 40% by mass of a cured phenol resin (Unibex C-10 type manufactured by Unitika) was used. This was made to contain 2.0 mass% of cobalt stearate. And other than that was carried out similarly to Example 1, and obtained the test piece made from a glassy carbon material. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Example 7
A random novolac phenol resin (Unibex N type, manufactured by Unitika) containing 30% by mass of carbon black (Tokai Carbon Co., Ltd., Seast SP) was used. And otherwise, it carried out similarly to Example 6, and obtained the test piece made from glassy carbon material. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Example 8
A random novolac phenol resin (Unibex N type manufactured by Unitika) containing 30% by mass of graphite particles (# 300 manufactured by Toyo Tanso Co., Ltd.) was used. And otherwise, it carried out similarly to Example 6, and obtained the test piece made from glassy carbon material. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Examples 9-19
In the same manner as in Example 6, a random novolac phenol resin (Unibex N type manufactured by Unitika) containing 40% by mass of a cured phenol resin (Unibex C-10 type manufactured by Unitika) was used. This was made to contain the metal compound shown in Table 1 in the ratio shown in Table 1. And other than that was carried out similarly to Example 1, and obtained the test piece made from a glassy carbon material. The bending elastic modulus was similarly measured about these test pieces.

  The results are shown in Table 1.

Comparative Example 1
A random novolac phenol resin (Unibex N type manufactured by Unitika Ltd.) which does not contain a metal compound was used as a raw material. And other than that was carried out similarly to Example 1, and obtained the test piece. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Comparative Example 2
A phenol resin composition in which 2.0% by mass of magnesium stearate, which is not a transition metal compound, was contained in a random novolac phenolic resin (Unibex N type manufactured by Unitika) as a raw material. And other than that was carried out similarly to Example 1, and obtained the test piece. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Comparative Example 3
Random novolac-based phenolic resin (Unitec N-type manufactured by Unitika) containing 40% by mass of a cured phenolic resin (Unitec C-10 type manufactured by Unitika) and containing no metal compound It was. And other than that was carried out similarly to Example 1, and obtained the test piece. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Comparative Example 4
Random novolac phenol resin (Unibex N type, manufactured by Unitika) containing 30% by mass of carbon black (Tokai Carbon Co., Ltd., Seast SP) was used as a raw material. And other than that was carried out similarly to Example 1, and obtained the test piece. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Comparative Example 5
A material containing 30% by mass of graphite particles (# 300, manufactured by Toyo Tanso Co., Ltd.) in a random novolac-based phenol resin (Unibex N type manufactured by Unitika) was used as a raw material. And other than that was carried out similarly to Example 1, and obtained the test piece. About this test piece, the bending elastic modulus was measured similarly.

  The results are shown in Table 1.

Comparative Examples 6-7
A random novolac phenol resin (Unibex N type manufactured by Unitika) containing 40% by mass of a cured phenol resin (Unibex C-10 type manufactured by Unitika) was used. This was made to contain the metal compound shown in Table 1 in the ratio shown in Table 1. And other than that was carried out similarly to Example 1, and obtained the test piece made from a glassy carbon material. The bending elastic modulus was similarly measured about these test pieces.

  The results are shown in Table 1.

  Examples 1 to 19 had good moldability, and it was possible to obtain molded products without problems. Moreover, the elastic modulus of the carbonized and fired molded article was low, and it could be used without any problem as a fuel cell separator.

  On the other hand, those of Comparative Examples 1 to 5 did not contain a higher fatty acid salt or complex of a transition metal, so a decrease in elastic modulus was not observed, and the rigidity was high when used as a carbon material. It was limited.

  Although the thing of Comparative Examples 6-7 contained the higher fatty acid salt of the transition metal, the content rate of the metal component was outside the scope of the present invention. That is, since the content rate of the comparative example 6 was too low, the bending elastic modulus was higher than the range of the present invention. Moreover, since the content rate of the thing of the comparative example 7 was too high, the test piece was not able to be created by molding defect.

  The glassy carbon material of the present invention is suitable for continuously and uniformly producing a structure such as a fuel cell separator. This glassy carbon material is lightweight, excellent in corrosion resistance, and excellent in mechanical properties, so that it can be used in a wide range of applications.

Claims (5)

A glassy carbon material comprising a carbide of a thermosetting resin composition, wherein at least one higher fatty acid salt or complex selected from the group consisting of cobalt, nickel, iron, chromium and manganese is 0.01 as a metal component A glassy carbon material obtained by carbonizing and baking a thermosetting resin composition containing ˜1.5 mass% and having a flexural modulus of 25 GPa or less. The higher fatty acid is at least one selected from the group consisting of stearic acid, 12-hydroxystearic acid, montanic acid, behenic acid, lauric acid, octylic acid, sebacic acid, undecylenic acid, ricinoleic acid, myristic acid, palmitic acid. The glassy carbon material according to claim 1 , wherein the glassy carbon material is present. Complex, vitreous carbon material of claim 1, wherein the phthalocyanine complex is at least one selected from acetylacetonate complex. A separator for a fuel cell, which is formed of the glassy carbon material according to any one of claims 1 to 3 . It is a method for manufacturing the glassy carbon material of any one of Claim 1 to 3 , Comprising: The glass-like characterized by including the process of shape | molding a thermosetting resin composition by injection molding. A method for producing a carbon material.