WO2005109553A2

WO2005109553A2 - Curable composition, cured product thereof and molded product thereof

Info

Publication number: WO2005109553A2
Application number: PCT/JP2005/008562
Authority: WO
Inventors: Kentaro Seki; Nobutoshi Sasaki; Hiroshi Uchida
Original assignee: Showa Denko K.K.
Priority date: 2004-05-07
Filing date: 2005-04-28
Publication date: 2005-11-17
Also published as: WO2005109553A3

Abstract

A curable composition comprising: at least, (A) a hydrocarbon compound having a plurality of carbon-carbon double bonds, wherein a silyl group is added to at least a part of the carbon-carbon double bonds; and (B) a carbonaceous material. There is provided a curable composition capable of providing a cured product having a high electro-conductivity, which is excellent in thermal resistance, electro-conductivity, moldability (such as those in compression molding, transfer molding, injection molding and injection compression molding), and in particular, excellent in hydrothermal resistance.

Description

DESCRIPTION

CURABLE COMPOSITION, CURED PRODUCT THEREOF AND MOLDED PRODUCT THEREOF

This Application claims the priority of application based on U.S. Provisional Application Serial No. 60/571,518 (filed on May 17, 2004).

Technical Field The present invention relates to a curable composition, and particularly to a curable composition suitably usable for a separator for fuel cells. More particularly, the present invention relates to a curable composition capable of providing a cured product having hydrothermal (or hot water) resistance, which is excellent in hydrothermal resistance, electro- conductivity, and moldability, and also relates to a cured product, a molded product, and a separator for a fuel cells, to be obtained from such a curable composition, and a molded (or shaped) product thereof, and to a process for producing the fuel cell separator.

Background Art Heretofore, certain materials such as metals and carbon materials have been used in fields where high electro-conductivity is required. Among these, carbon materials are free from corrosion unlike metals, and are excellent in electro-conductivity, thermal resistance, lubricity, heat conductivity, durability, etc.

Therefore, carbon materials have played an important role in various fields such as electronics, electrochemistry, energy and transportation equipments, etc. Also, composite materials based on combination of a carbon material and a polymer material have made remarkable progress, and permit high performance and high function to be achieved in various materials. Particularly, the degree of freedom of mold workability is expanded due to combination of a carbon material and a polymer material, and this is one reason why carbon materials have been developed in fields where electro-conductivity is required. Examples of the usage or application for carbon materials in which high electro-conductivity is required, may include: electronic materials for components such as circuit boards, resistors, and electrodes, and various members such as heaters, members constituting heat generating device, and dust collecting filter elements. In these applications, high thermal resistance is also required in addition to electro-conductivity. On the other hand, in view of environmental problems, fuel cells have attracted much attention as clean power generating devices, because they generate electric power by a reverse reaction of electrolysis using hydrogen gas and oxygen gas, and they produce no exhaust materials other than water. Also in this field, carbon materials and polymer materials can play an important role.- Fuel cells can be classified into several kinds depending on the type of electrolyte to be used. Among these kinds of fuel cells, solid polymer electrolyte-type fuel cells can work at a low temperature, and therefore, are most promising for automobile application and for public or civilian uses. A fuel cell of this type is constructed by stacking_,.unit cells, each of which comprises, e.g., a polymer electrolyte, a gas diffusion electrode, a catalyst, and a separator, and is thus capable of achieving high output power generation. In the fuel cell having the above construction, the separator is always in contact with water that is produced by the reaction for power generation. It is said that the operating temperature of the above- described solid electrolyte type fuel cell is about 80°C. Nonetheless, in applications of fuel cells in which a long operating period is expected, the separator is required to have high thermal resistance (in particular, hydrothermal resistance) so as to be able to bear the use thereof for a long period. In addition, the separator to be used for such an application to partition the unit cells, has typically at least one flow channel (or groove) formed thereon, to which a fuel gas (hydrogen, etc.) and an oxidant gas (oxygen, etc.) are supplied and from which the produced water (steam) is discharged. Therefore, the separator is required to have high gas impermeability in order to be capable of perfectly separating these gases, and is also required to have high electro-conductivity to minimize the internal resistance. Further, the separator is required to be excellent in heat conductivity, durability, strength, etc. In order to satisfy these requirements, the material for the separator has been heretofore studied with respect to using both metals and carbon materials. Metals have a problem in corrosion resistance thereof, and therefore, an attempt has been made to cover the surface thereof with a noble metal or carbon. However, with such a construction, sufficiently high durability cannot be obtained, and moreover, the cost for covering the metal becomes another problem. On the other hand, a large number of carbon materials have been studied as carbon materials for fuel cell separators, and examples thereof include a molded article obtained by press molding an expanded graphite sheet, a molded article obtained by impregnating a carbon sintered body with a resin and curing (or hardening) the resin, a vitreous carbon obtained by baking a heat curable resin, and a molded article obtained by mixing a carbon powder and a resin and molding resultant mixture. For example, JP-A-8-222241 (Patent Document 1; the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a complicated process such that a binder is added to a carbon powder and mixed under heating, the mixture is molded in CIP (Cold Isostatic Pressing) process, baked and graphitized, and the isotropic graphite material thus obtained is impregnated with a heat curable resin and is subjected to a curing treatment, and grooves are engraved therein by cutting. JP-A-60-161144 (Patent Document 2) discloses a technique of impregnating a paper containing carbon powder or carbon fiber with a heat curable resin, stacking and pressing the resultant papers and baking the stacked body. JP-A-2001- 68128 (Patent Document 3) discloses a technique of injection molding a phenol resin into a separator-shaped mold and baking the molded resin. The materials which have been subjected to a baking treatment as in these examples, can exhibit a high electro-conductivity and a high thermal resistance, but the baking treatment takes a long time and the productivity is low, and these materials also have a problem that they have a poor bending (or Flexural) strength. Further, when cutting of these materials is required, the mass productivity is further reduced and the cost is increased so that these materials can be hardly expected to become popular in the future. On the other hand, a molding method has been considered as means that can be expected to achieve high mass productivity and low cost. The material applicable thereto is generally a --composit.e .material.__of a carbonaceous material and a resin. For example, JP-A-58- 53167 (Patent Document 4), JP-A-60-37670 (Patent Document 5), JP-A-60-246568 (Patent Document 6), JP-B-64-340 (Patent Document 7: the term "JP-B" as used herein means an " examined Japanese patent application") and JP-B-6- 22136 (Patent Document 8) disclose a separator comprising graphite, carbon, and a heat curable resin such as phenol resin. JP-B-57-42157 (Patent Document 9) discloses a bipolar separator comprising a heat curable resin such as epoxy resin, and an electro-conductive substance such as graphite, and JP-A-1-311570 (Patent Document 10) discloses a separator obtained by blending an expanded graphite and a carbon black with a heat curable resin such as phenol resin and furan resin. In addition, JP-A- 11-154521 (Patent Document 11) discloses a separator capable of preventing the deterioration in the use thereof at a high temperature by using the brominated epoxy resin as a fire retardant. [Patent Document 1] JP-A 08-222241 [Patent Document 2] JP-A 60-161144 [Patent Document 3] JP-A 2001-068128 [Patent Document 4] JP-A 58-053167 [Patent Document 5] JP-A 60-037670 [Patent Document 6] JP-A 60-246568 [Patent Document 7] JP-B 64-000340 [Patent Document 8] JP-B 06-022136 [Patent Document 9] JP-B 57-042157 [Patent Document 10] JP-A 01-311570 [Patent Document 11] JP-A 11-154521

The various cured products as described above which comprise heat curable resins and carbonaceous materials do not have sufficient performance in view of high thermal resistance that is required in many applications such as electrodes, heaters, heat generating device members, and fuel cell separators. In addition, and particularly in the .case of a fuel cell separator, it is required to have a hydrothermal resistance in addition to a thermal resistance. However, the above mentioned conventional cured products comprising heat curable resin and carbonaceous materials do not have sufficient performance in view of high hydrothermal resistance that is required in the fuel cell separator application. Thus, the heat curable resin having an ester bond or an urethane bond in the structure thereof can be hydrolyzed in some cases by the hot water produced from the fuel cell. Therefore, when the conventional cured product comprising a heat curable resin and a carbonaceous material is used in applications such as automobiles or household electric appliances that are expected to be used for a long period, it has not been possible to obtain a product having sufficient durability. Disclosure of Invention An object of the present invention is to provide a curable composition that solves above-mentioned problems associated with the prior art. Another object of the present invention is to provide a curable composition capable of providing a cured product having a high electro-conductivity, which is excellent in thermal resistance, electro-conductivity, moldability (such as those in compression molding, transfer molding, injection molding and injection compression molding) , and in particular, excellent in hydrothermal resistance. A further object of the present invention is to provide a low cost cured product to be obtained by molding the above curable composition, which is excellent in thermal resistance, hydrothermal resistance, electro- conductivity, and heat radiating property, and to provide a molded product, and a fuel cell separator, and a process for producing same. As a result of earnest study conducted to solve above-mentioned problems, the present inventors have found that a hydrocarbon compound having a plurality of carbon-carbon double bonds (in particular, 1,2-polymer product of a diene compound) in which a silyl group is added to at least a part of the carbon-carbon double bonds, in combination with a carbonaceous material, provides a cured product that is excellent not only in moldability but also in hydrothermal resistance and electro-conductivity. The present invention has been accomplished based on such a discovery. The present invention may include, for example, the following embodiments [l]-[26]. [1] A curable composition comprising: at least, (A) a hydrocarbon compound having a plurality of carbon-carbon double bonds, wherein a silyl group is added to at least a part of the carbon-carbon double bonds ; and (B) a carbonaceous material. [2] A curable composition according to [1] , further comprising: (C) a hydrocarbon compound having a plurality of carbon-carbon double bonds. [3] A curable composition according to [1] or [2], further comprising: (D) a reactive monomer. [4] A curable composition according to any one of [l]-[3], wherein the silyl group is an organo-silyl group. [5] A curable composition according to [4], wherein the organo silyl group is represented by the following formula (1) : R,

Si ^•R. (1)

^R3 (wherein Ri, R₂, and R₃ each represents, independently of each other, a hydrogen atom, .an_^alkyl, alkoxy, or aryl group) . [6] A curable composition according to [5], wherein

Ri_/ 2_f and R₃ are each, independently of each other, an alkyl group with carbon number 1-6. [7] A curable composition according to [5] or [6], wherein R_l R₂, and R₃ are the same alkyl group. [8] A curable composition according to any one of [l]-[7], wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is a polymer having a carbon-carbon double bond in the side chain thereof. [9] A curable composition according to [8], wherein the polymer having a carbon-carbon double bond in the side chain, has a main chain containing 60 mole% or more of saturated monomer units. [10] A curable composition according to [9], wherein the monomer unit is a diene compound. [11] A curable composition according to [10] , wherein the diene compound is at least one kind selected from the group consisting of: butadiene, pentadiene, and isoprene. [12] A curable composition according to [11], wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is 1, 2-polybutadiene or 3,4- polyisoprene . [13] A curable composition according to [1] , wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is a polymer containing 60 mole% or more of a monomer unit represented by the following formula (2) or (3) :

[14] A curable composition according to any one of [1]-[12], wherein the carbonaceous material (B) is one kind or a combination of two or more kinds selected from the group consisting of: natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, vapor phase grown carbon fiber, and carbon nanotube. [15] A curable composition according to any one of

[1]-[13], wherein the carbonaceous material (B) has a powder electric resistivity of 0.1 Ωc or less in the direction at right angle to the direction of applied pressure in a state in which the carbonaceous material is pressurized so as to provide a bulk density of 1 g/cm³. [16] A curable composition according to any one of [1]-[13], wherein the carbonaceous material (B) contains 0.05 mass % to 10 mass % of boron. [17] A curable composition for a fuel cell separator, comprising a curable composition according to any one of [1]-[15]. [18] A hydrothermally resistant electro-conductive cured product which has been obtained by curing the curable composition according to any one of [1]-[16]. [19] A hydrothermally resistant electro-conductive cured product according to [18], which has a glass transition temperature of 160°C or higher, and a bending strength of 30 MPa or more in accordance with JIS K 6911. [20] A hydrothermally resistant electro-conductive cured product according to [18] or [19], which has a rate of mass change of -1.5% to + 1.5%, when a test piece of the cured product having a size of 30 mm x 30 mm x 3 mm is subjected to a hydrothermal resistance test at 180°C for 168 hours. [21] A hydrothermally resistant electro-conductive molded product which has been obtained by curing the curable composition according to any one of [1]-[17], wherein at least one flow channel is formed on one side or both sides thereof. [22] A fuel cell separator^' which has ^'been obtained by curing and molding the curable composition according to [17], wherein at least one flow channel is formed on one side or both sides thereof. [23] A fuel cell separator according to [22], which has a glass transition temperature of 160°C or higher, and a bending strength of 30 Mpa or more in accordance with JIS K 6911, and which has a rate of mass change in the range of -1.5 % to +1.5% when a test piece having a size of 30 mm x 30 mm x 3 mm is subjected to a hydrothermal test at 180°C for 168 hours. [24] A process for producing the hydrothermally resistant electro-conductive molded product according to [21] , wherein the molded product is produced by any of compression molding, transfer molding, injection molding and injection compression molding. [25] A process for producing the fuel cell separator according to [22] , wherein the fuel cell separator is produced by any of compression molding, transfer molding, injection molding and injection compression molding. [26] A partially silylated 1, 2-polybutadiene, which has been obtained by trimethylsilylating or triethylsilylating 3-90 mole% of the carbon-carbon double bonds of the side chain of 1, 2-polybutadiene.

Brief Description of Drawings Fig. 1 is a schematic sectional view showing a method of measuring the electric resistivity of a carbonaceous powder material; Fig. 2 is a schematic plan view showing the flat plate in the shape of a fuel cell separator produced in Example 10; Fig. 3 is a chart showing ¹H-NMR spectrum of partially silylated 1, 2-polybutadiene obtained in Preparation example <A-1>; and Fig. 4 is a chart showing FT-IR spectrum of partially silylated 1, 2-polybutadiene obtained in Preparation example <A-1>.

In the above drawings, the respective reference numerals denote the following items. 1 electrode comprising copper plate 2 compression rod comprising resin 3 pedestal (made of resin) 4 side frame (made of resin) 5: sample (carbonaceous material powder) 6: voltage probe.

Best Mode for Carrying Out the Invention Hereinbelow, the present invention will be described in detail, with reference to the accompanying drawings as desired. In the following description, "%" and "part(s)" representing a quantitative proportion or ratio are those based on mass, unless otherwise specifically noted. (Curable composition) The curable composition according to the present invention comprises, at least, (A) a hydrocarbon compound having a plurality of carbon-carbon double bonds with a silyl group added to a part or all of the carbon-carbon double bonds, and (B) a carbonaceous material. (Hydrocarbon compound having a plurality of carbon-carbon double bonds) The hydrocarbon compound having a plurality of carbon-carbon double bonds of the present invention is a compound comprising carbon atoms and hydrogen atoms as basic constituent elements, but it may also comprise oxygen atoms and/or nitrogen atoms. However, in view of prevention of hydrolysis by hot water, the compound may preferably have a structure which includes ester bonds, urethane bonds, and/or amide bonds in as small a proportion as possible. When the compound is a polymer, the (combined) number of ester bonds, urethane bonds, and amide bonds may preferably be_ 5% or less of the total number of monomer units. More preferably, such a compound is a polymer having carbon-carbon double bonds in the side chain. The polymer may be a homo-polymer or a copolymer. Further, even when the polymer is a homo-polymer (i.e., a polymer comprising only one kind of monomers) , the microstructure thereof may be different depending on the polymerization process (e.g., conditions such as the catalyst and the temperature) . For example, in the case of a homo-polymer of butadiene, one comprising the monomer units mainly in 1,4-cis linkage or 1,4-trans linkage has the carbon- carbon double bonds in the main chain thereof, and it assumes a rubbery state at ordinary temperature. This polymer is called generally as "polybutadiene rubber" . On the other hand, a polymer mainly comprising the monomer units (of 1,2-bond) having a main chain constituted by 1-position carbon atoms and 2-position carbon atoms shows a so-called resinous state when the molecular weight becomes relatively high. When the molecular weight is relatively low (the degree of polymerization is low) , it becomes a viscous liquid. In the case of the above-described diene compound, the monomer unit having a side chain containing a carbon- carbon double bond and a saturated main chain, may preferably refer to a monomer unit having a 1,2-linkage. Here, the "total number of monomer units", e.g., in the case of poly-butadiene, refers to the total number of monomer units which is obtained by counting the monomers corresponding to the 1,2-linkage, 1,4-cis linkage and

1, 4-trans-linkage as one kind of monomer units. If one kind of monomer is co-polymerized with another kind of monomer, each of the other kind of monomer is counted as one monomer unit. A monomer unit refers to a portion corresponding to each of the monomers as the raw material of a polymer. In the present invention, the ratio of the monomer units having a side chain containing a carbon-carbon double bond and a saturated main chain, may preferably be 60 mole % or more, more preferably 70 mole % or more, and most preferably 85 mole % or more, based on the total number of monomer uinits constituting the polymer. If the ratio of the above monomer units is less than 60 mole %, the resultant curing property may be insufficient in some cases, even when the carbon-carbon double bond of the side chain is subjected to reaction so as to provide a cured product. Further, in such a case, the bending modulus of elasticity, bending strength and the glass transition temperature (Tg) of the cured product including the carbonaceous material also tends to be decreased. The monomer unit having a carbon-carbon double bond and a saturated main chain may preferably be a monomer unit represented by the following formula (2) or (3) :

(Diene polymer) In the present invention, the polymer containing 60 mole % or more of the monomer unit having a carbon-carbon double bond in the side chain and a saturated main chain, may preferably be a polymer comprising the above- mentioned diene compounds (such as butadiene, pentadiene, and isoprene) as a main monomer (the monomer constituting 50 mole % or more of the raw material monomers) . In the present invention, such a polymer comprising the diene compounds as main monomer may be referred to as "diene polymer" in some cases. The diene polymer may be a copolymer of a plurality of diene compound monomers. Further, the carbon-carbon double bonds in the side chain may be partially hydrogenated (hydrogenated portion of the carbon-carbon double bond becomes a saturated carbon- carbon linkage) . Specific examples of the diene polymer usable in the present invention may include, but are not limited to: 1, 2-polybutadiene, 3, 4-polybutadiene, 3, 4-polyisoprene, polycyclopentadiene, etc. In the present invention, the diene polymer may preferably be 1, 2-polybutadiene or 3,4- polyisoprene, and more preferably 1, 2-polybutadiene. These polymers may also comprise other monomer units corresponding to the 3,4-linkage of polybutadiene as a microstructure. Further, a monomer other than the diene compounds may also be co polymerized with the diene compounds. Specific examples of the monomer other than the diene compounds may include: maleic anhydride, methacrylic acid, etc. The ratio of the monomer units corresponding to 3,4-linkage and the monomer units corresponding to other monomers may preferably be below 40 mole %, more preferably 30 mole %, and particularly below 15 mole %, of the total number of monomer units. The diene polymer is characterized in that its surface tension is low. The surface tension is a parameter indicating the hydrophobicity and/or the hydropholicity of the surface of a substance. The diene polymer of the present invention may preferably be hydrophobic. If the hydrophilicity of the polymer becomes large, the affinity with water is increased, and as a result, the hydrothermal resistance may tend to be decreased. Therefore, excessive hydrophilicity is undesirable. The process for synthesizing such a diene polymer is not particularly limited. Specific examples of the sunthesizing process include, but are not limited to: those as described in "Experiment Example 2.20 Synthesis of 1, 2-polybutadiene and cis-1, 4-polybutadiene by cobalt catalyst", pp.41 in "4^th Edition Experimental Chemistry Series (Jikken Kagaku Kouza) , Polymer Synthesis", 4^th ed. , edited by Chemical Society of Japan, May.6, 1992, published by Maruzen K. K. ; or "Experiment Example 2.26 Synthesis of 3, 4-polyisoprene by (Pr-O) 4Ti-Organic Aluminum type Catalyst", pp. 48, in "4^th Edition Experimental Chemistry Series, Polymer Synthesis", 4^th ed., edited by Chemical Society of Japan, May 6, 1992, published by Maruzen K. K. Method of confirming the microstructure of the diene polymer synthesized in this way, is not particularly limited, but the microstructure can be confirmed by any method. For example, in the present invention, the microstructure can be confirmed by a nuclear magnetic resonance method (hereinafter abbreviated as "NMR method"), or by a Fourier transform infrared spectroscopy (hereinafter abbreviated as "FT-IR method"), etc. Specific examples include: an article entitled "Experiment Example 223 Measurement of microstructure of polybutadiene by infrared spectra", pp. 45, in "Experimental Procedure for Polymer Synthesis (Kobunshi Gosei no Jikken-Ho)", 8^th impression, March 1, 1984, published by Kagakudoujin K. K. ; an article entitled "Experiment Example 225 Measurement of microstructure of polybutadiene by NMR", pp. 49, in "Experimental Procedure for Polymer Synthesis", 8^th impression, March 1, 1984, published by Kagakudoujin K. K. ; or an article entitled "Experiment Example 226 Measurement of microstructure of polyisoprene by NMR", pp. 51, in "Experimental Procedure for Polymer Synthesis", 8^th impression, March 1, 1984, published by Kagakudoujin K. K. In the present invention, the microstructure is measured by the above- mentioned NMR method. In the present invention, the branched structure or terminal structure of the diene polymer is not particularly limited, but those which have been modified or denatured in various manners, may also be used.

Specific examples thereof include: those having various kinds of structures such as acrylic modified structures, methacrylic modified structures,-..carboxy.- modified structures, maleic anhydride modified structures, epoxy modified structures, etc. However, the structure of the diene polymer usable in the present invention are not limited to these specific examples. (Hydrocarbon compound having a plurality of carbon- carbon double bonds with a silyl group added to at least a part of the carbon-carbon double bonds) In the present invention, the method for obtaining the hydrocarbon compound having a plurality of carbon- carbon double bonds with a silyl group added to at least a part of the carbon-carbon double bonds (hereinafter sometimes referred to as "silyl added diene polymer") is not particularly limited. Such a silyl added diene polymer can be obtained, for example, by reacting the above-mentioned hydrocarbon compound having a plurality of carbon-carbon double bonds with a silylating agent. A silyl group is a substituent containing a silicon atom. In the present invention, an organo-silyl group may preferably be used. Preferred examples of the organo-silyl group include, for example, those represented by the following formula (1) : R,

Si ^■ R, (1)

^R3 (wherein Ri, R₂, and R₃ each represents, independently of each other, a hydrogen atom, alkyl, alkoxy, or aryl group) . The above-mentioned alkyl group include an ethyl group, propyl group, etc., and the above-mentioned alkoxy group include an ethoxy group, and the above-mentioned aryl group include a phenyl group. In the present invention, a trimethyl-silyl group which is represented by (1) above where all of R_x, R₂, and R₃ are methyl group, and a triethyl-silyl group which is represented by (1) above where..all .of Ri, R₂, and R₃ are ethyl group, may preferably be used. The silylating agent used for the silylating reaction is not particularly limited, but may preferably be a linear silane containing at least one SiH group in the molecule is used, and more preferably with all of Ri, R₂, and R₃ being hydrocarbons. The catalyst used in the silylating reaction is not particularly limited, as long as it has activity for a hydro-silylating reaction. Examples of usable catalyst include: platinate chloride, platinum-olefin complex, platinum-vinylsiloxane complex as disclosed in JP-A 2003- 155378, etc. The silyl addition rate for the silyl added diene polymer in the present invention may preferably be 1-90

%, more preferably 3-70 %, and particularly 5-50 %, added with a silyl group, based on the carbon-carbon double bonds. If the addition rate is less than 1 %, properties of the cured product cannot be improved, and if the addition rate is greater than .90 %, curing characteristics are deteriorated. (Carbonaceous material) Examples of the carbonaceous material for use in the present invention (hereinafter referred to as "component (B) " in some cases) include one or a combination of two or more selected from the group consisting of: natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, vapor phase grown carbon fiber, and carbon nanotube. The carbonaceous material as the component (B) for use in the present invention may preferably have a powder electric resistivity as low as possible in the direction perpendicular to the direction of applied pressure when the bulk density is 1 g/cm³. The powder electric resistivity may preferably be 0.1 Ωcm or less, and more preferably 0.07 Ωcm or less. If the powder electric resistivity of the carbonaceous material exceeds 0.1 Ωcm, the cured product obtaAnecl by curing the composition may have poor electro-conductivity, and desired cured product is unlikely to be obtained. Fig. 1 shows a method of measuring the powder electric resistivity of the carbonaceous material. In Fig. 1, the reference numerals 1 and 1' denote electrodes comprising a copper plate, the reference numeral 2 denotes a compression rod comprising a resin, the reference numeral 3 denotes a pedestal comprising a resin, the reference numeral 4 denotes a side frame comprising a resin, the reference numeral 5 denotes a sample carbonaceous powder material, and the reference numeral 6 denotes a voltage probe provided in the center part in the direction vertical to the sheet surface at the lower end of the sample. By use of the four probe method as shown in Fig. 1, the electric resistivity of a sample can be measured as follows. A sample is compressed using the compression rod 2. An electric current (I) is passed from the electrode 1 to the electrode 1A The voltage (V) between the probes is measured by the probe 6. Here, a value measured when the sample is compressed to a bulk density of 1.5 g/cm³ by the compression rod is used for the voltage. If we assume that electric resistance (between probes) of the sample is R (Ω) , then R = V/I. From this, the electric resistivity can be determined according to the formula p = R-S/L [p: electric resistivity, S: cross sectional area (cm²) in the plane orthogonal to the direction of the current in the sample, that is the direction of applied pressure, L: distance (cm) between the probes 6] . In the actual measurement, the cross section of the sample in the plane orthogonal to the direction of the current has a width of about 1 cm and a length (height) of 0.5 to 1 cm, the length in the direction of the current is 4 cm, and the distance (L) between the probes is 1 cm. (Artificial graphite) —- ---- - In order to obtain artificial graphite as one example of the component (B) of the present invention, in general, coke is first produced. The starting material of the coke is petroleum pitch, coal pitch, or the like, and this starting material is carbonized into coke. From this coke, graphite powder is generally obtained by, for example, a method of pulverizing and then graphitizing the coke, a method of graphitizing the coke itself and then pulverizing the graphitized coke, or a method of adding a binder to the coke, forming and baking the resultant mixture, and graphitizing and then pulverizing the baked product (hereinafter, the coke and the baked product are collectively called "coke and the like") into powder. The starting material coke and the like may preferably be hindered from the growth of crystal, and may preferably be heat treated at 2,000°C or lower, more preferably 1200°C or lower. The graphitization may be performed, for example, by a method using' an Acheson furnace where the powder is enclosed in a graphite crucible and electric current is directly passed therethrough, or by a method of heating the powder by means of a graphite heating element. The carbonaceous material such as coke, artificial graphite, and natural graphite can be pulverized by using a high speed rotary mill (e.g., hammer mill, pin mill, cage mill), a ball mill (e.g., roll mill, vibrating mill, planetary mill), or a stirring mill (e.g., bead mill, attritor, flow tube type mill, annular mill) . In addition, a fine pulverizer such as screen mill, turbo mill, super micron mill, and jet mill may also be usedby selecting the conditions. The carbonaceous material such as coke and natural graphite is pulverized by using such a mill and by selecting the pulverization conditions, and then, if desired, classifying the powder, whereby the average particle size and particle size distribution can be controlled. The method of classifying the coke powder, artificial graphite powder, and natural graphite powder may be any method as long as the separation can be attained. For example, sieving or an air classifier such as forced vortex type centrifugal classifier (e.g., micron separator, turboplex, turbo classifier, super separator) , and iertial classifier (reformed virtual impactor, elbow jet), may be used. Also, a wet precipitation separation method, a centrifugal classification method, or the like may be used. (Expanded graphite powder) The expanded graphite powder to be used in the present invention may be, for example, a powder obtained by a method where a graphite having highly grown crystal structure such as natural graphite and pyrolytic graphite is dipped in a strongly oxidative solution such as a mixed solution of a concentrated sulfuric acid and nitric acid or a mixed solution of a concentrated sulfuric acid and aqueous hydrogen peroxide to produce a graphite intercalation compound, and the produced graphite intercalation compound is washed with water and is rapidly heated to expand the graphite crystal in the c- axis direction. Or, it may be a powder obtained by once rolling the powder obtained as described above into a sheet and then pulverizing the sheet. (Carbon fiber) Specific examples of the carbon fiber to be used in the present invention include a pitch type carbon fiber obtained from heavy oil, by-product oil, or coal tar, and a PAN type carbon fiber obtained from polyacrylonitrile. The vapor grown carbon fiber to be used in the present invention may be obtained, for example, by causing a thermal decomposition reaction to take place using, as a starting material, an organic compound such as benzene, toluene, or natural gas together with a hydrogen gas at a temperature from 800 to 1300°C in the presence of transition metal catalyst such as ferrocene. The obtained vapor grown carbon fiber may preferably be further subjected to a graphitization treatment at about 2,500 to 3,000°C, more preferably a graphitization treatment together with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum or silicon at about 2,500 to 3,200°C. The vapor grown carbon fiber to be used in the present invention may preferably have fiber diameter of 0.05 to 10 μm and fiber length of 1 to 500μm. More preferably, the vapor grown carbon fiber has fiber diameter of 0.1 to 5 μm and fiber length of 5 to 50μm, and most may preferably have fiber diameter of 0.1 to 0.5 μm and fiber length of 10 to 20μm. (Carbon nanotube) The carbon nanotube has recently attracted attention from industry not only by its mechanical strength but also by its field emission function and hydrogen absorption function, and furthermore, its magnetic function. This carbon nanotube is also called graphite whisker, filamentous carbon, graphite fiber, extra fine carbon tube, carbon tube carbon fibril, carbon microtube or carbon nanofiber. Carbon nanotube includes a single layer carbon nanotube where the graphite film forming the tube is a single layer, and a multilayer carbon nanotube where the graphite film is composed of multiple layers. In the present invention, eithe the single layer carbon nanotube or the multilayer carbon nanotube may be used. However, the single carbon nanotube is preferred because a cured product having higher electro-conductivity or mechanical strength is likely to be obtained. The carbon nanotube can be manufactured, for example, by an arc discharge method, a laser evaporation method , or a thermal decomposition method, which are described in Carbon Nanotube no Kiso (Fundamental Study of Carbon Nanotube) , written by Saito and Bando, pages 23 to 57, Corona Sha (1998) . For enhancing the purity, the carbon nanotube obtained may further be purified by a hydrothermal method, an oxidation method or the like. For removing impuroties, the carbon nanotube may preferably be subjected to a high-temperature treatment in an inert gas atmosphere at about 2,500 to 3,200°C. More preferably, the carbon nanotube may be subjected to a high-temperature treatment in an inert gas atmosphere at about 2,500 to 3,200°C together with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum and silicon. The carbon nanotube to be used in the present invention may preferably have fiber diameter of 0.5 to 100 nm and fiber length of 0.01 to lOμm. More preferably, the carbon nanotube has fiber diameter of 1 to 10 nm and fiber length of 0.05 to 5μm, and still more may preferably have fiber diameter of 1 to 5 nm and fiber length of 0.1 to 3μm. The fiber diameter and fiber length of the vapor grown carbon fiber and carbon nanotube for use in the present invention can be measured by using a scanning electron microscope (SEM) . More specifically, in this measurement, the diameters and lengths of several hundreds pieces of fibers were measured, and the number average values of these diameters and lengths were calculated. (Carbon black) The carbon black for use in the present invention may include Ketjen black and acetylene black which are obtained by incomplete combustion of a natural gas and the like or by thermal decomposition of acetylene, a furnace carbon obtained by incomplete combustion of a hydrocarbon oil or a natural gas, and a thermal carbon obtained by thermal decomposition of a natural gas. (Boron) The boron may preferably be contained in the carbonaceous material as the component (B) in the present invention in an amount of 0.05 to^" 10 mass%, based on the total mass of the carbonaceous material. If the amount of boron is less than 0.05 mass%, the graphite powder having high electro-conductivity, which is the object of boron contained in the carbonaceous material, is less likely to be obtained. On the other hand, even if the amount of boron exceeds 10 mass%, the effect of boron on improving the electro-conductivity of the carbon material tends to be decreased. The method of measuring the quantity of boron contained in the carbonaceous material is not particularly limited, but the quantity of boron can be measured by any measurement method. In the present invention, the measured value obtained by an inductive type plasma emission spectrometry (hereinafter, abbreviated as "ICP") or an inductive type plasma emission spectrometry mass spectrometry (hereinafter, abbreviated as "ICP-MS") are used. More specifically, sulfuric acid and nitric acid are added to a sample and microwave heated (230°C) to be decomposed (digester method) , and perchloric acid is further added to the decomposition product, and the resultant product is diluted with water. Then, the sample thus obtained is subjected to ICP emission spectrometry to measure the quantity of boron. The carbonaceous material (B) to be used in the present invention may preferably be one containing 0.05 mass% to 10 mass% of boron. Boron can be incorporated into the carbonaceous material, for example, by a method of adding a boron source such as B in elemental form, B₄C, BN, B₂0₃, or H₃BO₃ to a single substance or a mixture of two or more of natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, vapor grown carbon fiber, carbon nanotube or the like, thoroughly mixing the boron compound, and then graphitizing the mixture at about 2,500 to 3,200°C. If the mixing of boron compound is not uniform, the resulting "graphite powder is not only non-uniform but also highly likely to be sintered at the graphitization. For attaining uniform mixing, the boron source may preferably be formed into powder having particle size of 50 μm or less, more preferably about 20μm or less, and then mixed with the powder of coke or the like. If graphitization is performed without adding boron to the carbonaceous material, the degree of graphitization (i.e., crystallinity) may be decreased and the lattice spacing may be increased. As a result, graphite powder having high electro-conductivity may not be obtained. The form of boron contained is not particularly limited as long as boron and/or boron compound is contained in the graphite. However, in a preferred form, boron is present between layers of the graphite crystal or a boron atoms are substituted to a part of carbon atoms constituting the graphite crystal. In the case where a part of carbon atoms are substituted by boron atoms, the bonding between the boron atoms and the carbon atoms may be in any bonding form such as covalent bonding or ionic bonding. (Mass ratio of the component (A) and component (B) ) The mass ratio of the diene polymer as the component (A) relative to the carbonaceous material as the component (B) of the present invention, may preferably be in the range of 0.01:1-4:1, and more 'preferably in the range of 0.01:1-1.5:1. If the mass of the component (A) is less than 0.01 of the mass of the component (B) , moldability tends to be lowered, and if the mass of the component (A) is more than 4 times the mass of the component (B) , the electro-conductivity of the cured product tends to become lower. (The component (C) and the blending ratio thereof) In the present invention, in addition to the component (A) , a non-silylated hydrocarbon compound (C) having a plurality of carbon-carbon double bonds may be further added to the composition. The blending ratio of the component (C) may be adjusted in accordance with the so-called master batch adjustment method such that the addition rate of the silyl group relative to the total sum of the number of carbon-carbon double bonds of the blended component (C) and the number of the unreacted carbon-carbon double bonds of the component (A) falls in the range as defined above. (Reactive monomer) The curable composition according to the present invention may comprise a reactive monomer as another component (D) . The reactive monomer usable in the present invention is not particularly limited, but various kinds of reactive monomers may be used. For example, it is possible to add a monomer having a radical reactivity containing an unsaturated double bond such as vinyl group and allyl group, for the purpose of controlling the rate of reaction, adjusting the viscosity, improving the cross-linking density, adding certain functions, etc. Specific examples of the radically reactive monomers containing an unsaturated double bond such as vinyl group and allyl group, include: unsaturated fatty acid esters, aromatic vinyl compounds, vinyl esters of aromatic carboxylic acid or saturated fatty acids and derivatives thereof, cross-linking polyfunctional monomers, etc. (Unsaturated fatty acid ester) Specific examples of the above-mentioned unsaturated fatty acid esters include: alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethyl hexyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, methyl cyclohexyl (meth) acrylate; acrylic acidaromatic esters such as phenyl (meth) acrylate, benzyl (meth) acrylate, 1- naphtyl (meth) acrylate, fluorophenyl (meth) acrylate, chlorophenyl (meth) acrylate, cyanophenyl (meth) acrylate, methoxy phenyl (meth) acrylate, biphenyl (meth) acrylate; haloalkyl (meth) acrylate, such as fluorophenyl (meth) acrylate, chloromethyl (meth) acrylate, glycidyl (meth) acrylate, alkylamino (meth) acrylate, α-cyanoacryloc acid ester, etc. (Aromatic vinyl compounds, etc.) Specific examples of the above-mentioned aromatic vinyl compound may include: styrene, α-methyl styrene, chlorostyrene, styrene sulfonic acid, 4-hydroxy styrene, vinyl toluene, etc. Specific examples of the above vinyl ester of aromatic carboxylic acid or saturated fatty acid, and derivatives thereof, may include: vinyl acetate, vinyl propionate, vinyl benzoate, etc. (Cross-linking polyfunctional monomer) Specific examples of the above-mentioned cross- linking polyfunctional monomer may include: di (meth) acrylates such as ethylene glycol di (meth) acrylate, di ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetra ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, 1, 3-butyleneglycol di (meth) acrylate, 1, 4-butandiol di (meth) acrylate, 1, 5-pentadiol di (meth) acrylate, 1,6-hexadiol di (meth) acrylate, neopentylglycol di (meth) acrylate, oligoester di (meth) acrylate, polybutadiene (meth) acrylate, 2,2- bis(4- (meth) acryloyloxyphenyl) propane, 2,2-bis (4-ω- (meth) acryloyloxy piriethoxy) propane; aromatic carboxylic acid diallyl compound such as phthalic acid diallyl, iso phthalic acid diallyl, iso phthalic acid dimetallyl, terephthalic acid diallyl, 2, 6-naphthalene dicarboxylic acid diallyl, 1,5- naphthalene dicarboxylic acid diallyl, 1,4-xylene dicarboxylic acid diallyl, 4,4'- diphenyl dicarboxylic acid diallyl; cross-linking bifunctional monomers such as cyclohexane dicarboxylic acid diallyl, divinylbenzene; cross-linking trifunctional monomers such as tri ethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, penta erythritol tri (meth) acrylate, tri (meth) allyl isocyanurate, tri (meth) allyl cyanurate, triallyl trimellitate, diallyl chlorendate; cross-linking tetrafunctional monomers such as pentaerythritol tetra (meth) acrylate, etc. Among these reactive monomers (D) , it is preferred to add a cross-linking polyfunctional monomer in order to improve the thermal resistance and the hydrothermal resistance. The amount of the reactive monomers (which may have a linkage portion susceptible to hydrolysis, such as ester bond and urethane bond) to be used for such a purpose may preferably be as small as possible, in view of prevention of the hydrolysis by hot water. However, it is possible to use an appropriate amount of the reactive monomers in view of the balance with respect to another property. The amount of the reactive monomer (D) to be used in the present invention may preferably be 1-40 mass parts, more preferably 2-30 mass parts, particularly 3-25 mass parts, based on 100 mass parts of the component (A) and the component (C) combined. If the amount of the reactive monomer exceeds 40 mass parts, the hydrothermal resistance of the cured product (such as fuel cell separator) may become insufficient in some cases. (Additives) The curable composition according to the present invention may further contain additives such as lubricants, thickeners, cross-linking agents, cross- linking auxiliaries, curing initiators, curing accelerators, curing retarder, plasticizers, shrinkage reducing agent, thixotropic agents, surfactants or detergents, solvent, glass fibers, inorganic fiber fillers, organic fibers, an ultraviolet stabilizer, an antioxidant, a defoaming agent, a levelling agent, a mold releasing agent, a lubricant, a water repellant, a thickener, a hydrophilicity imparting agent, and a curing auxiliary. As the curing initiator, it is preferred to use a compound which can produce radicals by heat, such as organic peroxides and azo compounds. Known peroxides such as dialkylperoxides, acyl peroxides, hydroperoxides, ketone peroxides, and peroxy esters, may be used. Specific examples of the organic peroxides may include: benzoyl peroxide, 1, 1-bis (t-butyl peroxy) cyclohexane, 2,2-bis (4, 4-dibutyl peroxyl cyclohexyl) propane, t-butyl peroxyl-2-ethyl hexanate, 2,5-dimethyl 2, 5-di (t-butyl peroxyl) hexane, 2,5-dimethyl 2, 5-di (benzoyl peroxy) hexane, t-butyl peroxy benzoate, t-butyl cumyl peroxide, p-methane hydroperoxide, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 2, 5-, 5-dimethyl-2-dibutylperoxy hexyne-3, etc. It is preferred to add an organic peroxide in an amount of 0.2-10 mass parts, more preferably 0.5-8 mass parts, and still more preferably 0.8-6 mass parts, with respect to 100 mass parts of (the component (A) + component (C) + component (D) ) . If the amount of the organic peroxide is less than 0.2 mass parts, the cross- linking density of the cured product is decreased so as to decrease the strength thereof, and may lead to decrease of the durability. If, on the other hand, the amount of the organic peroxide exceeds 10 mass parts, the gas resulting from the decomposition of the organic peroxide is increased so that the gas tjghtness of the cured product may be decreased. (Preparation of curable composition) The preparation process of the curable composition of the present invention is not particularly limited, but it is preferred in preparing the curable composition to mix the above-described components uniformly by using a mixer or kneadr commonly used pn the field of resin, such as roller extruder, kneader, Banbury™ mixer, Henschel™ mixer, or planetary mixer while keeping them at a temperature at which curing reaction is not initiated. When an organic peroxide is added, the organic peroxide may preferably be added and mixed at the final stage after all other components are uniformly mixed. For the purpose of facilitating the supply of the materials to a molding machine or a mold, the hydrothermally resistant curable composition of the present invention may be pulverized or granulated after kneading or mixing. The curable composition can be pulverized by using a homogenizer, a Wiley mill, a high speed rotary mill, (e.g., hammer mill, pin mill, cage mill, blender) or the like. The pulverization may preferably be performed while cooling so as to prevent the materials from aggregating with each other. The granulation may be performed by a method of palletizing the composition by using an extruder or a co-kneader, or by using a pan-type granulator. (Molding of curable composition) For the purpose of obtaining a cured product having a precise thickness, the curable compound obtained as described above, may be molded once into a molded sheet form having a predetermined thickness and a predetermined width at a temperature at which no curing is initiated, by using an extruder, a roll, a .calender, etc. In order to conduct molding so as to provide a higher thickness precision, it is preferred that the composition is molded by an extruder, and then rolled by a roll or calender.

For the purpose of eliminating voids or air in the sheet, it is preferred to use extrusion in vacuum. The obtained sheet may be cut or punched so as to provide an intended size, and the resultant sheet inserted into a mold having both-side grooves as one sheet or two or more sheets in parallel or in superposed arrangement, and then is heat-cured in a compression molding machine to obtain the cured product. In order to obtain high quality products substantially free from defects, it is preferred to evacuate the cavity during the curing. After the curing, in order to straighten the warping of the product, it is preferred to cool the product under a pressure, of 3 MPa or more with . a..presser. bar which is controlled to a temperature of 10-50°C. With respect to the curing conditions, it is possible to search and select an optimum temperature depending on the kind of the composition. The temperature may be appropriately selected, for example, in the range of 120-250°C for the period of 30-1,800 seconds. After the composition is cured, after-curing may be performed at a temperature in the range of 150- 250°C for 10-600 minutes, whereby complete curing can be achieved. By performing the after-curing under a pressure of 5 MPa or more, the product can be prevented from warping. (Properties of hydrothermally resistant electro- conductive cured product) The hydrothermally resistant electro-conductive cured product of the present invention which has been cured as described above, may preferably have a glass transition temperature (hereinafter sometimes referred to as "Tg") of 160°C or higher, more preferably 170°C or higher, and still more preferably 180°C or higher. If Tg is lower than 160°C, the obtained cured product is less likely to have sufficient thermal resistance. Tg may be measured by a TMA method using a Thermo- analyzer (TMA-50) manufactured by Shimadzu Corporation. In this measurement, the coefficient of linear expansion is measured in an atmosphere of nitrogen supplied at 50 mL/min from 30°C to 250°C at a temperature rising rate of 5°C /min using a sample having a size of 3 x 3 x 5 (mm) , and Tg is determined by detecting a discontinuity point in the coefficient of the linear expansion. The hydrothermally resistant electro-conductive cured product according to the present invention may preferably have a bending strength of 30 MPa or more, more preferably 35 MPa or more, and still more preferably 40 MPa or more. If the bending strength is less than 30 MPa, the cured product is less likely to have a sufficient strength. The bending strength may be measured by a method prescribed in JIS K 6911. More specifically, a test specimen (80 mm x 10 mm x 4 mm) is subjected to the three point bending strength measurement under the conditions of a span space of 64 mm and a bending speed of 2 mm/min. The hydrothermally resistant electro-conductive cured product according to the present invention may preferably have a volume resistivity of 2 x 10^~2 Ωcm or less, more preferably 8 x 10^"3 Ωcm or less, and still more preferably 5 x 10^-3 Ωcm or less. If the volume resistivity exceeds 2 x 10^~2 Ωcm, a sufficient electro- conductivity may not be obtained. The volume resistivity is measured by the four-point probe method in accordance with JIS K 7194. The hydrothermally resistant electro-conductive cured product according to the present invention may preferably have a contact resistance of 2 x 10^~2 Ωcm² or less, more preferably 1 x 10^~2 Ωcm² or less, and still more preferably 7 x 10^~3 Ωcm² or less. If the contact resistance exceeds 2 x 10^"2 Ωcm², a sufficient electro- conductivity may be unlikely to be obtained. The value of the contact resistance is determined as follows. A test piece (20 mm x 20 mm x 2 mm) and a carbon plate (1.5 x 10^"3 Ωcm, 20 mm x 20 mm x 1 mm) are brought into contact with each other, and then sandwiched between two copper plates, and a load of 98 N is applied thereon. A constant current of 1 A is passed in the through direction and the probes are contacted to the interface between the test piece and the carbon plate to measure the voltage. From the measured voltage, resistance value is calculated. The value obtained is integrated with the contacting cross-sectional area and the resulting value is designated as the contact resistance value. ^" The hydrothermally resistant^" electro-conductive cured product according to the present invention may preferably have a thermal conductivity of 1.0 W/m-K or more, more preferably 4.0 W/m-K or more, and still more preferably 10 W/m-K or more. If the thermal conductivity is below 1.0 W/m-K, the heat radiating property of the material may become poor, and the material may be undesirably heated to a high temperature during usage. The thermal conductivity may be measured by using a specimen (diameter φ: 10 mm, thickness: 1.7 mm) at a temperature of 80°C in vacuum by irradiating a ruby laser beam (excitation voltage: 2.5 kV) according to the laser- flash method (tι_/2 method, thermal constant measuring apparatus for laser-flash method: LF/TCM FA8510B mfd. by Rigaku Denki Co.). (Hydrothermal resistance) The hydrothermally resistant electro-conductive cured product according to the present invention is characterized in that the hydrothermal resistance thereof can be increased. Specific examples of the index of hydrothermal resistance may include, e.g., water absorption and rate of mass change. These values may be measured by a method according to JIS K 7202. For example, a test piece having a constant size is placed in a pressure-resistant container, and a constant volume of distilled water is added thereto, and is subjected to a test in an oven at a constant temperature for a predetermined time period. The change in the mass of the test piece before and after the test is measured, whereby the hydrothermal resistance can be determined. The hydrothermally resistant electro-conductive cured product according to the present invention may preferably exhibit a mass change in the range of -1.5 % to +1.5 % after the 168 hr test at 180°C, in the conditions that the size of the test piece is 30 mm x 30 mm x 3 mm, and 50 ml of distilled water is added thereto. The mass change may more preferably be in the range of -1.0 % to +1.0 %. If the mass change is below -1.5 %, or exceeds +1.5

%, the mass change becomes too large in a long term use thereof, and the dimension of the molded product may be greatly changed undesirably. Further, if the mass change is below -1.5 %, the material is more liable to be deteriorated and may produce cracks and fracture. Such a state is particularly unfavorable. In the electro-conductive cured product in the present invention, it is preferred to maintain a good balance between the bending strength (at the time of breakage) and the bending strain (at the time of breakage) . The cured product which exhibits only large bending strength is liable to be a fragile material. The cured product which exhibits only large strain is liable to provide a poor strength. Therefore, it -is preferred to prepare a cured product wherein the bending strength and the strain are well balanced. From such a point of view, the hydrothermally resistant electro-conductive cured product which can be obtained from the curable composition in the present invention shows an excellent performance showing balanced bending strength and strain. (Boron content in the cured product) The hydrothermally resistant electro-conductive cured product according to the present invention may preferably contain 0.1 ppm or more of boron. The boron content may more preferably be 0.5 ppm or more, and still more preferably be 1 ppm or more. If the boron content is less than 0.1 ppm, a high electro-conductivity is unlikely to be obtained. The boron content in such a case may also be measured in the same manner as in the case of the carbonaceous material (B) , and the ICP-MS method should be used. (Hydrothermally resistant electro-conductive molded product) In the hydrothermally.. resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases, the gases to be passed therethrough include air, oxygen, hydrogen, nitrogen, steam, etc., and the shape and size of the flow channel for gases can be appropriately selected or designed depending on the use and the size of the molded product. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a Tg of 160°C or higher, more preferably 170°C or higher, and still more preferably 180°C or higher. If Tg is lower than 160°C, the obtained molded product is less likely to have sufficient thermal resistance. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have bending strength of 30 MPa or more, more preferably 35 MPa or more, and still more preferably 40 MPa or more. If the bending strength is less than 30 MPa, the molded product is less likely to have a sufficient strength. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a volume resistivity of 2 x 10^~2 Ωcm or less, more preferably 8 x 10^-3 Ωcm or less, and still more preferably 5 x 10^"3 Ωcm or less. If the volume resistivity exceeds 2 x 10^~2 Ωcm, a sufficient electro-conductivity may not be obtained. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a contact resistance of 2 x 10^~2 Ωcm² or less, more preferably 1 x 10^"2 Ωcm² or less, and still more preferably 7 x 10^~3 Ωcm² or less. If the contact resistance exceeds 2 x 10^"2 Ωcm², a sufficient electro-conductivity may be unlikely to be obtained. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a thermal conductivity of 1.0 W/m-K or more, more preferably 4.0 W/m-K or more, and still more preferably 10 W/m-K or more. If the thermal conductivity is below 1.0 W/m-K, the load to be applied to the material undesirably becomes too high. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably contain 0.1 ppm or more of boron. The boron content may more preferably be 0.5 ppm or more, and still more preferably be 1 ppm or more. If the boron content is less than 0.1 ppm, a high electro-conductivity is unlikely to be obtained. The shape and size of the flow channel of the separator according to the present invention may be appropriately set or designed depending on the shape and size of the separator itself and on the flow rate of gases, etc. The cross section of the flow channel is, in general, rectangular with the depth of about 0.5 mm and width of about 1.0 mm, but is not limited to this example. The fuel cell separator according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a Tg of 160°C or higher, more preferably 170°C or higher, and still more preferably 180°C or higher. If Tg is lower than 160°C, the obtained fuel cell separator is less likely to have sufficient thermal resistance. The fuel cell separator according ^"to^" the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a bending strength of 30 MPa or more, more preferably 35 MPa or more, and still more preferably 40 MPa or more. If the bending strength is less than 30 MPa, the cured product is less likely to have a sufficient strength. The fuel cell separator according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a volume resistivity of 2 x 10^"2 Ωcm or less, more preferably 8 x 10^"3 Ωcm or less, and still more preferably 5 x 10^~3 Ωcm or less. If the volume resistivity exceeds 2 x 10^"2 Ωcm, a sufficient electro-conductivity may not be obtained. The fuel cell separator according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a contact resistance of 2 x 10^~2 Ωcm² or less, more preferably 1 x 10^~2 Ωcm² or less, and still more preferably 7 x 10^~3 Ωcm² or less. If the contact resistance exceeds 2 x 10^~2 Ωcm², a sufficient electro- conductivity may be unlikely to be obtained. The fuel cell separator according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably have a thermal conductivity of 1.0 W/m-K or more, more preferably 4.0 W/m-K or more, and still more preferably 10 W/m-K or more. If the thermal conductivity is below 1.0 W/m-K, the heat radiating property of the material may become poor, and the material may be undesirably heated to a high temperature during usage. Also, due to heat generation of the fuel cell separator, it becomes undesirably difficult to control so as maintain a constant operating temperature. The fuel cell separator- according to the present invention having flow channel formed on both sides or on one side thereof for passing gases may preferably contain 0.1 ppm or more of boron. The boron content may more preferably be 0.5 ppm or more, and still more preferably be 1 ppm or more. If the boron content is less than 0.1 ppm, a high electro-conductivity is unlikely to be obtained. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases can be obtained by curing and shaping the curable composition according to the present invention by using a general molding method for a heat curable resin.

(Process for producing fuel cell separator) The process for producing the fuel cell separator according to the present invention is not particularly limited. Specific examples of the process may include, but are not limited to: compression molding, transfer molding, injection molding, cast molding, injection compression molding, or the like. The molding may preferably be performed while keeping the inside of the mold or the mold as a whole under a vacuum state at various mold workings. The hydrothermally resistant electro-conductive molded product according to the present invention having flow channel formed on both sides or on one side thereof for passing gases can be obtained by curing and shaping the curable composition according to the present invention using a general molding method for a heat curable resin. It is possible that, after the curable composition according to the present invention is once cured, the above-mentioned flow channel (such as groove) is formed thereon by machine work. It is also possible that the formation of flow channel is carried out simultaneously with the curing of the curable composition by compression molding, etc., using a mold having a reverse configuration corresponding to the gas flow channel. Specific examples of the process for producing the fuel cell separator may include, but are not limited to: compression molding, transfer molding, injection molding, cast molding, injection compression molding. The molding may preferably be performed while keeping the inside of the mold or the mold as a whole under a vacuum state during the molding. In the compression molding, for enhancing the molding cycle, a multi-cavity mold may preferably be used. More preferably, a multi-stage press (laminate press) may be used to mold a large number of products with a small power output. In order to improve plane precision in the case of flat type product, the compression molding may preferably be performed after once forming a non-cured sheet. In the injection molding, for the purpose of further enhancing the moldability, the molding can be performed in a supercritical state by injecting carbon dioxide gas from the halfway point of the molding machine cylinder and dissolving the gas in the material. For improving the plane precision of a product, the injection compression molding may preferably be used. The injection compression molding method which can be used may include: 1) a method of injecting the material into an open mold and then closing the mold; 2) a method of injecting the material while closing the mold; and 3) a method of injecting the material with the locking force being set to zero and then applying the locking force. With respect to the mold temperature, it is important to search and select an optimum temperature depending on the kind of the composition. The temperature can be appropriately selected in the range of 120°C-250°C for the period in the range of 30 to 1,800 seconds. After the composition is cured, after-curing is performed at a temperature in the range of 150°C-250°C for the period in the range of 10 to 600 minutes to thereby achieve complete curing. By performing the after-curing under pressure of 5 MPa or more, the product can be prevented from warping. The curable composition according to the present invention is easy to be molded, and therefore, is optimal as a composite material in the fields where high precision in thickness is required. Further, the cured product thereof can reproduce the electro-conductivity or the thermal conductivity of the graphite virtually with no limit, and can provide high performance by exhibiting excellent properties in thermal resistance, hydrothermal resistance, corrosion resistance, nolding precision, and the like. Accordingly, use of the curable composition or the cured product is not particularly limited. Specific examples of such a use may include: fuel cell separators, electrodes, electromagnetic wave shielding plates, heat radiating materials, laminates for battery, electronic circuit boards, resistors, heaters, dust collecting filter elements, panel type heaters, electromagnetic materials, etc.

Examples The present invention will be described in more detail below with reference to Examples. However, the present invention is by nomeans limited to these Examples . Materials used in the Examples to be described later were prepared as follows. Preparation examples

Component (A) : Silylated diene polymer <A-1> A mixture of 65 g of triethylsilane (manufactured by Tokyo Kasei Kogyo Co.) and 37 ml of toluene was placed into a 300 ml three-port glass reaction container, and was maintained at 70°C under nitrogen atmosphere flowing in the container. 1.0 ml of platinum catalyst (manufactured by NE CHEMCAT Co., 3% platinum-VTS (1,3- divinyl-1, 1, 3, 3-tetramethyl disiloxane) -xylene solution) was added dropwise. Then, a mixture of 30 g of polybutadiene (manufactured by Nippon Soda Co., B-3000 (molecular weight: 3,000, 1,2-linkage: 91.7 %, viscosity at 50°C: 10.7 Pa-s) and 52 ml of toluene was added over 5 minutes. While maintaining the temperature in the container at 70°C, reaction was continued for 14 hours, and then heating was stopped. After remaining triethylsilane and toluene were removed by using an evaporator and a vacuum pump, 43 g of partially silylated 1, 2-polybutadiene was obtained. Silylation rate was calculated to be 25.2 % using ¹H- NMR analysis, from the area ratio between signals of vinyl hydrogen (54.95-5.10) in the side chain terminal and of the triethylsilyl group methyl hydrogen (50.45-0.75) after the silylation. Tetramethyl silane was used as the reference. Fig. 3 shows the ¹H-NMR spectrum, and Fig. 4 shows FT-IR spectrum. The measurement conditions for Fig. 3 and 4 are as follows. Fig. 3 C: \WINNMR98\COMMON\_DEFAULT.ALS Si-B3000 DFILE C:\WINNMR98\COMMON\ DEFAULT.ALS OBNUC 1H EXMOD NON OBFRQ 399.65 MHz OBSET 124.00 KHz OBFIN 10500.00 Hz POINT 32768 FREQU 7993.60 Hz SCANS 16 ACQTM 4.0993 sec PD 2.9010 sec PW1 6.00 usec IRATN 511 CTEMP 21.0 c SLVNT C6D6 EXREF 0.00 ppm BF 1.20 Hz RGAIN 7 Fig. 4 PERKIN ELMER 04/03/05 15:36 Showa Denko B3000Si IR chart Y: 16 scans, 4.0 cm-1 Result of elemental analysis is shown below. Elemental analysis: C: 77.92 % H: 11.04 % (Elements other than C,H,N,S) 8.67 %. ¹H-NMR was measured at room temperature with AL-400 manufactured by JEOL Ltd. using toluene-d8 as measurement solvent. FT-IR was measured by transmission method with 1600FT-IR manufactured by Perkin Elmer Co. with the sample directly applied to the AgCl plate. Elemental analysis was performed using CHNS-932 manufactured by LECO Co. with sym-diphenylthiourea as the reference to obtain CHNS analysis. More specifically, 0.2 g of sample was precisely weighed and placed into a platinum crucible, alkaline dissolved with Na₂C0₃, and measure by ICP-AES method. <A-2> Silylation reaction was performed as in <A-1> above, except that a mixture of 219 g of triethylsilane and 121 ml of toluene, 3.0 ml of platinum catalyst, and a mixture of 105 g of 1, 2-polybutadiene (manufactured by Nippon Soda Co., B-1000 (molecular weight: 1,000, 1,2-linkage: 90.0 %, viscosity at 45°C: 1.0 Pa-s) and 186 ml of toluene, were used and reaction was continued for 8 hours, and 145 g of partially silylated 1, 2-polybutadiene was obtained. Silylation rate was calculated, in the same manner as in the case of <A-1>, to be 20.5 %. Elemental analysis: C: 80.07 % H: 11.26 % (Elements other than C,H,N,S) 11.04 %. Component (B) : Carbonaceous material <B-1>: Graphite fine powder containing boron LPC-S coke (hereinafter, referred to as "coke A") mfd. by Shin Nittetsu Kagaku K.K., which is a non-needle type coke (calcined product) , was coarsely pulverized into a size of 2 to 3 mm or less by a pulverizer (mfd. by Hosokawa Micron K.K.). The coarsely pulverized product was finely pulverized by a jet mill (IDS2UR, mfd. by

Nippon Pneumatic K.K.). Thereafter, the powder obtained in this way was classified so as to adjust the particle size thereof to a desired value. The particles of 5 μm or less in size were removed by air classification using a turbo classifier (TC15N, mfd. by Nisshin Engineering K.K.) . To a portion (14.4 kg) of the finely pulverized product, 0.6 kg of boron carbide (BC) was added and then mixed therewith by a Henschel™ mixer at 800 rpm for 5 minutes. The resulting mixture was enclosed in a graphite crucible with a cover having an inside diameter of 40 cm and a capacity of 40 liters. The crucible was sealed and placed in a graphitization furnace provided with a graphite heater and the powder was graphitized at a temperature of 2,900°C in an argon atmosphere. The resultant product was taken out from the crucible to thereby obtain 14 kg of graphite powder. The graphite thus obtained had an average particle size of 20.5 μm, and a boron content of 1.3 mass %. <B-2>: Graphite fine powder without boron Coke A was coarsely pulverized by a pulverizer into a size of 2 to 3 mm and this coarsely pulverized product was finely pulverized by a jet mill. Thereafter, the obtained powder was adjusted by classification to the desired particle size. The particles of 5 μm or less in size were removed by air classification by using a turbo classifier. Then, the powder was enclosed in a graphite crucible with a cover having an inside diameter of 40 cm and a capacity of 40 liters. The crucible was sealed and placed in a graphitization furnace provided with a graphite heater, and the powder was graphitized at a temperature of 2,900°C. After being allowed to cool, the powder was taken out to obtain graphite fine powder. The graphite thus obtained had an average particle size of 20.5 μm, and a boron content of 0 wt %. <B-3>: Vapor phase grown carbon fiber The vapor phase grown carbon fiber (hereinafter, abbreviated as "VGCF" . Trade Mark by Showa Denko K.K.) was VGCF-G (fiber diameter: 0.1-0.3 μm, fiber length: 10-50 μm) mfd. by Showa Denko K.K.

<B-4>: Carbon nanotube The carbon nanotube (hereinafter, abbreviated as

"CNT") was obtained in the following manner. A hole having a diameter of 3 mm and a depth of 30 mm was bored in a graphite rod having a diameter of 6 mm and a length of 50 mm from the tip thereof along the center axis, and the hole was packed with a mixture powder of rhodium (Rh) : platinum (Pt) : graphite (C) = 1 : 1 : 1 (mass ratio), to thereby form an anode. On the other hand, there was formed a cathode having a diameter of 13 mm and a length of 30 mm which comprised graphite having a purity of 99.98 mass %. These electrodes were disposed in a reaction container so that they were disposed oppsite .to each other, and the electrodes were connected to a direct current power supply. The inside of the reaction container was replaced with helium gas having a purity of 99.9 vol. %, and direct current arc discharge was induced. Thereafter, the soot which had been attached to the inner wall of the reaction container (chamber soot) and the soot which had been accumulated on the cathode (cathode soot) were collected. The pressure in the reaction container and the electric current were 600 Torr and 70A, respectively. During the reaction, the anode and the cathode were operated- so that the gap between the anode and the cathode always became 1-2 mm. The soot thus collected was charged into a mixture solvent comprising water and ethanol (mixing mass ratio = 1 : 1), and then was dispersed therein using ultrasonic vibration, and the resultant dispersion was collected and the solvent was removed using a rotary evaporator. The sample thus obtaind was dispersed in a 0.1 % aqueous solution of benzalkonium chloride as a cationic surfactant using ultrasonic vibration, and then was subjected to centrifugal separation at 5000 rpm for 30 minutes, and the resultant dispersion was collected. Further, the dispersion was purified by heat treating the dispersion in air at 350°C for five hours, to thereby obtain carbon nanotube having a fiber diameter of 1-10 nm and a fiber length of 0.05-5 μm. Compound (C) : Diene polymer <C-1> JSR K.K. RB-810 (melting point: 70°C, Melt index at 21.2 N: 3 g/10 min., 1,2-linkage: 90.0%) <C-2> 1, 2-polybutadiene: mfd. by Nippon Soda K.K., B-3000 (molecular weight: 3,000, 1,2-linkage: 91.7 %, viscosity at 50°C: 10.7 Pa-s) <C-3> End-modified polybutadiene: Nippon Soda K.K., TE- 2000 (end-methacrylate modified product, 1, 2-linkage: 90 % or more, viscosity at 50°C: 54.9 Pa-s) Component (D) : Reactive monomer <D-1> Divinylbenzene: DVR-960, mfd. by Nippon Steel Chemistry Co., Ltd. (divinylbenzene content 95-97 %) <D-2> Styrene: Reagent Chemical, mfd. by Wako Pure Chemical Industries Co., Ltd. <Heat curable resin> Phenolic resin: Resol resin BRL-274, mfd. by Showa Highpolymer Co. (viscosity at 20°C: 25 Pa-s, non-volatile component 75%) Vinyl ester resin: VR-77, mfd. by Showa Highpolymer

Co. <Curing initiator> Dicumyl peroxide: Percumyl D, mfd. by Nippon Oil& Fats Co., Ltd. 2, 5-dimethyl-2, 5-di (t-butyl peroxy) hexane-3:

Perhexa-25B mfd. by Nippon Oil& Fats Co., Ltd.. The following Table 1 shows the ingredients (mass ratio) of the curable composition other than the carbonaceous material in Examples and Comparative Examples, and Table 2 shows the ingredients (mass ratio) of the curable composition.

SHDR685Tablel [Table 1]

SHDR685Table2 [Table 2] Ingredients of curable composition (mass ratio)

Example 1-Example 9, Comparative Example 1 Materials having composition as shown in Table 1, Table 2 above were kneaded at 90°C for 10 minutes using a kneader. The kneaded product was charged in a mold for forming a flat plate of 100 mm x 100 mm (thickness varies depending on the physical properties tested) , and heated at the mold temperature of 170°C under pressure of 30 MPa for 12 minutes using a 50 t compression molder to obtain a cured product.

Comparative Example 2 Materials having composition as shown in Table 1, Table 2 above were kneaded at 90°C for 10 minutes using a kneader. The kneaded product was charged into a mold for forming a flat plate of 100 mm x 100 mm (thickness varies depending on the physical properties tested) , and heated at the mold temperature of 120°C under pressure of 30 MPa for 15 minutes using a 50 t compression molder to obtain a cured product. Measurement result on the physical properties of the cured product obtained in Examples and Comparative Examples as described above is shown in Table 3 below.

SHDR685Table3 [Table 3]

Method- for measuring physical properties is described below. The volume resistivity was measured by the four probe method in accordance with JIS K 7194. The bending strength and bending strain were measured by using Autograph (AG lOkNI) mfd. by Shimadzu

Corporation. In accordance with JIS K 6911, a test piece (80 mm x 10 mm x 4 mm) was subjected to the measurement in three point bending strength method under the conditions of span interval of 64 mm and a bending rate of 2 mm/min. Tg was measured by the TMA method using

Thermoanalyzer (TMA-50) , mfd. by Shimadzu Corporation.

The size of the test piece was 3 x 3 x 5 (mm) . In this measurement, in an atmosphere of nitrogen supply of 50 mL/min., the coefficient of linear expansion was measured from 30°C to 250°C at a temperature rising rate of

5°C/min., to thereby determine Tg. In the hydrothermal resistance measurement, in accordance with JIS K 7209, a test piece having a size of 30 mm x 30 mm x 3 mm was placed in a fluorine resin container, and 50 ml of distilled water was added thereto. Then, this system was placed in a pressure resistant SUS 316L container, and is subjected to the measurement for 168 hours while the container was rotated in an oven at 180°C. The mass of the sample before and after the test was measured to obtain the rate of mass change. The moldability (Disc flow test) was conducted by charging 10 g of a composition into a press machine adjusted to 160°C and applying a load of 18 t thereto to thereby evaluate the spreading (diameter, mm) of the material. As shown in Table 3, the cured product and the molded product obtained by using the curable composition according to the present invention were excellent in the hydrothermal resistance, thermal resistance, mechanical strength, and electro-conductivity, and the flowability at the time of molding was also good.

Example 10 The composition obtained in Example 1 was charged into the mold capable of providing a plate having a size of 280 x 200 x 1.5 mm and having 1 mm pitch grooves on both sides thereof, and was cured by using a 500 t compression molding machine at a mold temperature of 170°C under a pressure of 60 MPa for 10 minutes. A flat plate in the form of a fuel cell separator having grooves on both sides thereof was thus obtained (Fig. 2) .

Industrial Applicability The curable resin composition according to the present invention can provide a cured product having excellent properties (such as thermal resistance, hydrothermal resistance, electro-conductivity, and/or heat radiating property) , in particular, hydrothermal resistance, and therefore, the present invention can be widely applied to materials in various fields which have heretofore been difficult to realize. Examples of the usage or application of the present invention may include: various application or parts including fuel cell separators, electronic materials such as electrodes, circuit boards, resistors, laminates for batteries; and various members such as heaters, members constituting heat generating device, dust collecting filter elements, panel type heaters, and electromagnetic materials. The present invention is particularly useful as materials for fuel cell separators in solid polymer electrolyte type fuel cells.

Claims

CLAIMS 1. A curable composition comprising: at least, (A) a hydrocarbon compound having a plurality of carbon-carbon double bonds, wherein a silyl group is added to at least a part of the carbon-carbon double bonds; and (B) a carbonaceous material. 2. A curable composition according to claim 1, further comprising: (C) a hydrocarbon compound having a plurality of carbon-carbon double bonds. 3. A curable composition according to claim 1 or 2, further comprising: (D) a reactive monomer. 4. A curable composition according to any one of claims 1-3, wherein the silyl group is an organo-silyl group. 5. A curable composition according to claim 4, wherein the organo silyl group is represented by the following formula (1) : R,

Si ^• . (1) R₃ (wherein R_x, R₂, and R₃ each represent, independently of each other, a hydrogen atom, an alkyl, alkoxy, or aryl group) . 6. A curable composition according to claim 5, wherein Ri, R₂, and R₃ are each, independently of each other, an alkyl group with carbon number 1-6. 7. A curable composition according to claim 5 or 6, wherein Ri, R₂, and R₃ are the same alkyl group. 8. A curable composition according to any one of claims 1-7, wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is a polymer having a carbon-carbon double bond in the side chain thereof . 9. A curable composition according to claim 8, wherein the polymer having a carbon-carbon double bond in the side chain, has a main chain containing 60 mole% or more of saturated monomer units. 10. A curable composition according to claim 9, wherein the monomer unit is a diene compound. 11. A curable composition according to claim 10, wherein the diene compound is at least one kind selected from the group consisting of: butadiene, pentadiene, and isoprene. 12. A curable composition according to claim 11, wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is 1, 2-polybutadiene or 3,4- polyisoprene. 13. A curable composition according to claim 1, wherein the hydrocarbon compound having a plurality of carbon-carbon double bonds is a polymer containing 60 mole% or more of a monomer unit represented by the following formula (2) or (3) :

14. A curable composition -according to any one of claims 1-12, wherein the carbonaceous material (B) is one kind or a combination of two or more kinds selected from the group consisting of: natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, vapor phase grown carbon fiber, and carbon nanotube. 15. A curable composition according to any one of claims 1-13, wherein the carbonaceous material (B) has a powder electric resistivity of 0.1 Ωcm or less in the direction at right angle to the direction of applied pressure in a state in which the carbonaceous material is pressurized so as to provide a bulk density of 1 g/cm³. 16. A curable composition according to any one of claims 1-13, wherein the carbonaceous material (B) contains 0.05 mass % to 10 mass % of boron. 17. A curable composition for a fuel cell separator, comprising a curable composition according to any one of claims 1-15. 18. A hydrothermally resistant electro-conductive cured product which has been obtained by curing the curable composition according to any one of claims 1-16. 19. A hydrothermally resistant electro-conductive cured product according to claim 18, which has a glass transition temperature of 160°C or higher, and a bending strength of 30 Mpa or more in accordance with JIS K 6911. 20. A hydrothermally resistant electro-conductive cured product according to claim 18 or 19, which has a rate of mass change of -1.5% to + 1.5%, when a test piece of the cured product having a size of 30 mm x 30 mm x 3 mm is subjected to a hydrothermal resistance test at 180°C for 168 hours. 21. A hydrothermally resistant electro-conductive molded product which has been obtained by curing the curable composition according to any one of claims 1-17, wherein at least one flow channel for flowing gas is formed on one side or both sides thereof. 22. A fuel cell separator which has been obtained by curing and molding the curable composition according to claim 17, wherein at least one flow channel for flowing gas is formed on one side or both sides thereof. 23. A fuel cell separator according to claim 22, which has a glass transition temperature of 160°C or higher, and a bending strength of 30 MPa or more in accordance with JIS K 6911, and which has a rate of mass change in the range of -1.5 % to +1.5% when a test piece having a size of 30 mm x 30 mm x 3 mm is subjected to a hydrothermal test at 180°C for 168 hours. 24. A process for producing the hydrothermally resistant electro-conductive molded product according to claim 21, wherein the molded product is produced by any of compression molding, transfer molding, injection molding and injection compression molding. 25. A process for producing the fuel cell separator according to claim 22, wherein the fuel cell separator is produced by any of compression molding, transfer molding, injection molding and injection compression molding. 26. A partially silylated 1, 2-polybutadiene, which has been obtained by trimethylsilylating or triethylsilylating 3-90 mole% of the carbon-carbon double bonds of the side chain of 1, 2-polybutadiene.