JP4883361B2 - Conductive curable resin composition, cured product thereof, and molded product thereof - Google Patents

Description

  The present invention relates to a curable resin composition, and more particularly to a conductive curable resin composition excellent in heat dissipation in addition to conductivity and a cured product thereof.

  Recent technological innovations, starting with the electronics industry, are remarkable, and the material technologies that support them are also making rapid progress. The development of polymer materials that play a role in the materials is no exception, and many new or high-performance polymer materials have been developed, and the range of use has been steadily expanding.

  The main characteristics required of polymer materials in the electronics field vary depending on the product and application, but they include moldability, heat resistance, durability, electrical characteristics (high insulation and high conductivity), corrosion resistance, heat dissipation, etc. There are many thermosetting resins such as epoxy resins and phenol resins, and various engineering plastics such as polyimide, polycarbonate, polyphenylene oxide, and liquid crystal polymer.

  By the way, although the request | requirement with respect to the material which comprised various performances as enumerated above is strong, there are technically very difficult aspects and it is often disadvantageous in terms of price. One of such technical problems is the development of a polymer material that is conductive (particularly high conductivity with a volume resistivity of 1 Ωcm or less) and has both heat dissipation and heat resistance. The target material development is also in this point. That is, for example, a highly conductive composition used for various members in the battery field such as a separator for a fuel cell using hydrogen, alcohol or the like as a fuel.

  Many studies have been made in the past on highly conductive compositions comprising a carbon-based material and a thermosetting resin composition. For example, Patent Documents 1 and 2 disclose a combination of graphite and a phenol resin. On the other hand, a plurality of techniques relating to the use of an epoxy resin and an unsaturated polyester resin as a base resin are also disclosed.

Furthermore, in applications where higher conductivity is required, a method is known in which these curable compositions are calcined and graphitized after being molded (Patent Document 3).
Japanese Patent Publication No. 50-11355 JP 59-213610 A JP-A-8-222241

When a curable resin composition containing ordinary graphite powder is used, it is necessary to greatly increase the amount of graphite powder added in order to obtain the same conductivity as that of the cured product of the present invention, and thus the specific gravity increases. In addition, there is a drawback that the moldability at the time of molding such as compression molding, transfer molding and injection molding is deteriorated. In addition, with a composite material comprising a combination of a resin and ordinary graphite powder, a cured product having a contact resistance of 2 × 10 ⁻² Ωcm ² or less could not be obtained.

  Furthermore, in order to obtain high conductivity, including a firing step in which the molded body is heated for a long time at a high temperature of 1000 to 3000 ° C., the time required for the production becomes long and the production process becomes complicated and the cost is reduced. There was a problem of rising.

  The present invention has been made in view of such a situation, even if the amount of conductive filler filling is relatively small, the cured body is excellent in conductivity, heat resistance, heat dissipation, in addition, It is a main subject to provide a conductive curable resin composition excellent in molding processability, a cured product thereof, and a molded product thereof.

  In view of such a situation, the present inventors have a graphite powder and a curable resin or a monomer composition thereof (including an initiator if necessary) as a main raw material, and the cured product has excellent conductivity. In addition, diligent efforts were made to develop a conductive curable resin composition exhibiting heat resistance and heat dissipation, and by combining a specific graphite containing boron and a curable resin, a conductive curing meeting the purpose of the present invention. The inventors have completed the inventions of the functional resin composition and the cured product.

That is, this invention relates to the electroconductive curable resin composition shown by the following (1)-(19), its hardening body, and its molded object.

(1) (A) graphite powder containing boron in graphite crystal, (B) curable resin and / or curable resin composition, and (C) fiber diameter is 0.05 to 10 μm, fiber length is 1 A conductive curable resin composition comprising vapor-grown carbon fibers of ˜500 μm and / or carbon nanotubes having a fiber diameter of 0.5 to 100 nm and a fiber length of 0.01 to 10 μm.
(2) The mass ratio (A + C: B) of the sum of the components (A) and (C) and the component (B) is 20 to 99.9: 80 to 0.1 (sum is 100). The conductive curable resin composition according to (1), characterized in that
(3) The mass ratio of the component (A) and the component (C) (sum is 100) is 60 to 99.9: 40 to 0.1. (1) or (2) The conductive curable resin composition in any one.
(4) In a state in which the bulk density of the graphite powder of component (A) is pressurized to 1.5 g / cm ³ , the powder electrical resistivity of component (A) in the direction perpendicular to the pressing direction is 0 The conductive curable resin composition according to any one of (1) to (3), which is 0.06 Ωcm or less.
(5) The conductive curable resin composition according to any one of (1) to (4), wherein the component (A) has an average particle size of 5 μm to 80 μm.
(6) (A) component, a specific surface area of ^3m 2 / g or less, an aspect ratio of 6 or less, a tapping bulk density of 0.8 g / cm ³ or more, graphite lattice spacing (Co value) of less than 6.745 Å The conductive curable resin composition according to any one of (1) to (5), which is a powder.
(7) The molding conductive curable resin composition according to any one of (1) to (6), wherein the component (A) is a graphite crystal using coke as a raw material.
(8) The component (B) contains at least one selected from a phenol resin, an unsaturated polyester resin, an epoxy resin, a vinyl ester resin and an allyl ester resin, and a curing agent (1) to The conductive curable resin composition according to any one of (7).
(9) The conductive curable resin composition according to (8), wherein the component (B) contains an epoxy resin and a phenol resin.
(10) The conductive curable resin composition according to (9), wherein the epoxy resin includes a cresol novolac type epoxy resin, and the phenol resin includes a novolac type phenol resin.
(11) The component (B) is a vinyl ester resin and / or allyl ester resin and at least one monomer selected from allyl ester monomers, acrylic ester monomers, methacrylic ester monomers and styrene monomers, and a radical polymerization initiator. The conductive curable resin composition according to (8), which comprises:
(12) The conductive curable resin composition according to (11), wherein the vinyl ester resin is a novolac type vinyl ester resin.
(13) The conductive material according to any one of (1) to (12), wherein the component (A) is a graphite powder containing 0.05% by mass to 5.0% by mass of boron. Curable resin composition.
(14) The volume resistivity obtained by curing the conductive curable resin composition according to any one of (1) to (13) is 2 × 10 ⁻² Ωcm or less, and the contact resistance is 2 × 10 ⁻² Ωcm. ² or less and a thermal conductivity of 1.0 W / m · K or more.
(15) The method for producing a conductive cured body according to (14), wherein the molding is performed by any one of compression molding, transfer molding, injection molding, and injection compression molding.
(16) The conductive curable resin composition according to any one of (1) to (13), wherein the sum of the component ( A) and the component (C) is 50% by mass to 95% by mass. The volume resistivity obtained by curing the photocurable resin composition is 2 × 10 ⁻² Ωcm or less, the contact resistance is 2 × 10 ⁻² Ωcm ² or less, the thermal conductivity is 1.0 W / m · K or more, and A separator for a fuel cell, wherein an air permeability is 1 × 10 ⁻⁶ cm ² / sec or less.
(17) The conductive curable resin composition according to any one of (1) to (13), wherein the sum of the components ( A) and (C) is 50% by mass to 95% by mass. Volume specific resistance obtained by curing the curable resin composition is 2 × 10 ⁻² Ωcm or less, contact resistance is 2 × 10 ⁻² Ωcm ² or less, thermal conductivity is 1.0 W / m · K or more, and ventilation A fuel cell characterized in that a separator for a fuel cell having a rate of 1 × 10 ⁻⁶ cm ² / sec or less is molded by compression molding, transfer molding, injection molding or injection compression molding. Manufacturing method for the separator.
(18) A conductive cured product obtained by curing the conductive curable resin composition according to any one of (1) to (13).
(19) The conductive curable resin composition according to any one of (1) to (13), wherein the sum of the component ( A) and the component (C) is 50% by mass to 95% by mass. A fuel cell separator obtained by curing a photocurable resin composition.

  The conductive curable resin composition of the present invention has a cured product having excellent conductivity, heat resistance, heat dissipation, and corrosion resistance. It can be widely applied to various uses / parts such as electric products, machine parts, vehicle parts, etc., and is particularly useful as a material for a separator of a fuel cell such as a polymer electrolyte fuel cell.

  Hereinafter, the present invention will be described in detail. The graphite powder (A) in the present invention is characterized by containing boron in the graphite crystal. When boron is not added, graphitization decreases the degree of graphitization (crystallinity), increases the lattice spacing (hereinafter referred to as “Co value”), and a highly conductive graphite powder cannot be obtained. Further, the boron may be contained in any form as long as boron and / or a boron compound are mixed in the graphite. However, the boron is present between the graphite crystals, and some of the carbon atoms forming the graphite crystals are boron atoms. Those substituted with are also more preferred. In addition, the bond between the boron atom and the carbon atom when a part of the carbon atom is substituted with the boron atom may be any bond mode such as a covalent bond or an ionic bond.

The specific surface area of the (A) graphite powder in the present invention is preferably 3 m ² / g (BET method) or less. When the specific surface area exceeds 3 m ² / g, conductivity and moldability may be deteriorated. In order to reduce the specific surface area, the particle size, particle shape, particle size distribution, surface property, and the like are important factors, and among these factors, the particle shape is preferably as close to spherical as possible.

  In order to further increase the conductivity, it is important to increase the packing density of the graphite particles. For this purpose, the graphite powder particles are preferably not spherical but as close to spherical as possible. When the shape of the particles is expressed by an aspect ratio, the aspect ratio of the graphite powder of the present invention is 6 or less, preferably 5 or less. For molding using the conductive curable resin composition, compression molding, injection molding, transfer molding, injection compression molding, or the like is applied. In this case, the aspect ratio of the graphite powder as the component (A) is 6. When it exceeds, fluidity | liquidity will worsen and it may cause a molding defect.

  The aspect ratio is generally expressed by the ratio of the major axis length to the minor axis length (long axis length / short axis length), and the value can be obtained from a micrograph of the particle. In the present invention, the aspect ratio was calculated as follows.

First, an average particle diameter A calculated by a laser diffraction scattering method and an average particle diameter B calculated by an electrical detection method (Cole counter method) are obtained. Here, from each measurement principle, A can be regarded as the diameter of a sphere having the maximum particle length, and B can be regarded as the diameter of a sphere having the same volume as the particle. When the particle is assumed to be a disk, and the bottom diameter of the disk is A and the volume is C [C = (4/3) × (B / 2) ³ π], the thickness of the disk is T = C / (A / 2) ² π can be calculated. Therefore, the aspect ratio can be obtained by A / T.

The graphite powder of the present invention has a tapping bulk density of 0.8 g / cm ³ or more, preferably 0.9 g / cm ³ or more. If it is less than 0.8 g / cm < ³ >, a filling property will worsen and electroconductivity or airtightness will fall.

  The tapping bulk density was obtained by weighing a certain amount of graphite powder (6.0 g) into a 15 mmφ measurement cell, setting it in a tapping device, dropping height 45 mm, tapping speed 2 sec / times, 400 After the free fall, it is calculated from the relationship between the measured volume and mass.

The tapping bulk density of the graphite powder is related to the particle size, shape, and surface properties of the powder, and varies depending on the particle size distribution even if the average particle size of the particles is the same. Therefore, if there are a lot of scale-like particles or a lot of fine powder, the tapping bulk density will not increase. For example, if the graphite material is simply pulverized to an average particle size of about 10 μm to 30 μm, it contains a lot of fine powder and it is quite difficult to make the tapping bulk density 0.8 g / cm ³ or more. The graphite powder of the present invention has as little fine powder as possible, wide particle size distribution, and high tapping bulk density, but the aspect ratio is small as described above, that is, it is not scaly, or the scale is low. A highly conductive cured body having a high packing density is obtained.

The graphite powder of the component (A) of the present invention is desirably as crystalline as possible. The Co value of the graphite structure in which the hexagonal network layers are stacked is desirably 6.745 Å or less, more preferably 6.730 Å or less. , even more preferably not more than 6.720 Å. Thus, the electrical resistivity of the cured product can be lowered by increasing the crystallization of the graphite powder.

It is conceivable that the graphite powder contains boron, beryllium, aluminum, silicon, and other graphitization catalysts. However, boron is particularly effective, and when boron is added to the carbon powder and graphitized, the degree of graphitization (crystallinity) ) Increases and the Co value decreases. Further, when boron is added to obtain graphite having the same crystallinity, the processing temperature can be lowered as compared with the case where boron is not added.

The graphite powder of the present invention desirably has a powder electrical resistivity as low as possible in the direction perpendicular to the pressing direction when the bulk density is 1.5 g / cm ^3, and is preferably 0.06 Ωcm or less. Furthermore, it is more preferable that it is 0.01 ohm-cm or less. When the electrical specific resistance of the graphite powder exceeds 0.06 Ωcm, the conductivity of the cured product obtained by curing the composition with the curable resin becomes low, and a desired cured product cannot be obtained.

  The method for measuring the electrical resistivity of this graphite powder is shown in FIG. In FIG. 1, 1, 1 'are electrodes made of a copper plate, 2 is a compression rod made of resin, 3 is a pedestal, 4 is a side frame, and both are made of resin. 5 is a graphite powder of the sample. Reference numeral 6 denotes a lower end of the sample, which is a voltage measurement terminal provided at the center in the direction perpendicular to the paper surface.

Using the four-terminal method shown in FIG. 1, the electrical resistivity of the sample is measured as follows. The sample is compressed by the compression rod 2. A current (I) is passed from the electrode 1 to the electrode 1 ′. The voltage (V) between the terminals is measured by the terminal 6. At this time, the voltage is a value obtained when the sample is made to have a bulk density of 1.5 g / cm ³ by a compression rod. If the electrical resistance (between terminals) of the sample is R (Ω), then R = V / I. From this, ρ = R · S / L can be used to determine the electrical resistivity [ρ: electrical resistivity, S = cross-sectional area (cm ² ) perpendicular to the energization direction of the sample, ie, the pressurizing direction, L is This is the distance (cm) between the terminals 6. ]. In actual measurement, the sample has a cross-section in the right-angle direction of about 1 cm in width, 0.5 cm to 1 cm in length (height), 4 cm in length in the energizing direction, and a distance (L) between terminals of 1 cm.

  In order to increase the conductivity of the cured product of the present invention, it is necessary to increase the conductivity of the graphite powder. Therefore, it is necessary to increase the conductivity of graphite itself, and for that purpose, improvement in the crystallinity of graphite is required. For example, graphite produced from an easily graphitizable raw material is used, or the graphitization temperature is increased. It is also effective to increase the crystallinity of graphite using a graphitization catalyst such as boron. It is also effective to reduce the number of contacts between graphite particles, that is, to reduce the content of fine powder. From the viewpoint of conductivity, it is preferable that the graphite particles are large, but the surface of the molded product becomes rough, so that too large graphite particles cannot be used. Therefore, it is preferable to make the average particle size of the graphite powder as large as possible within a range that does not hinder the molding and curing of the composition.

  The particle size of the graphite powder in the present invention is preferably 5 μm to 80 μm, more preferably 20 μm to 50 μm, in terms of average particle size. The particle size was measured by a laser diffraction scattering method. Specifically, 50 mg of a sample is weighed and added to 50 ml of distilled water, 0.2 ml of a 2% Triton (surfactant) aqueous solution is further added and ultrasonically dispersed for 3 minutes, and then Nikkiso Co., Ltd. Measured with a Microtrac HRA device.

  The (A) graphite powder of the present invention can be produced as follows.

  In order to obtain graphite powder, usually coke is first produced. The raw material for coke is petroleum pitch, coal pitch, or the like. These raw materials are carbonized into coke. In general, coke is converted into graphitized powder by pulverizing coke and then graphitizing, or by pulverizing coke itself and then pulverizing, or by adding a binder to coke and molding and firing (coke and this calcined product). There is a method of pulverizing a product after combining it with a graphitization process.

  However, when coke or the like is pulverized after graphitization, crystals are developed, so that when pulverized, it tends to become a scaly powder. Therefore, in order to obtain powder particles having a smaller aspect ratio and a more spherical shape in the present invention, pulverized non-graphitized coke and the like are classified and adjusted to a predetermined particle size and specific surface area. It is desirable to perform graphitization. Since it is better that the raw material coke or the like has no crystal growth as much as possible, heat treatment at 2000 ° C. or lower, preferably 1200 ° C. or lower is suitable.

  Moreover, the aspect ratio after pulverization varies depending on the type of raw material coke. It is known that coke includes easily graphitizable so-called acicular coke and non-acicular coke having poorer graphitization. According to the knowledge of the present inventor, when coke is pulverized into powder, it has been found that non-acicular coke is suitable for obtaining powder particles having a small aspect ratio. Accordingly, the raw coke is preferably non-acicular coke heat-treated at 2000 ° C. or lower, preferably 1200 ° C. or lower.

It has been found that when a powder such as coke is graphitized, not only the crystallization proceeds, but also the surface area of the particles is reduced, and this is convenient. For example, the specific surface area of the coke powder having an average particle diameter of about 10μm coke and the obtained milled is about 14m ² / g, when graphitized at 2800 ° C. or more so, the specific surface area 2m ² / g~3m ² / g. However, when it is pulverized after graphitization, it is at least 5 m ² / g or more, and in some cases 10 m ² / g or more, depending on the particle size. Compared with this, the method of graphitizing after pulverization has rearranged carbon atoms when graphitizing, and part of the surface evaporated at high temperature, so that the surface was cleaned or smoothed. Is expected to decrease.

  For crushing coke, etc., high-speed rotary crusher (hammer mill, pin mill, cage mill), various ball mills (rolling mill, vibration mill, planetary mill), stirring mill (bead mill, attritor, distribution pipe mill, annular mill) Etc. can be used. Further, a screen mill, a turbo mill, a super micron mill, and a jet mill of a fine pulverizer can be used by selecting conditions. Coke and the like are pulverized using these pulverizers, selection of pulverization conditions at that time, and classification of the powder as necessary, so that the average particle diameter is preferably in the range of 5 μm to 80 μm. More preferably, particles having a particle size of 3 μm or less and / or more than 80 μm are substantially removed so that each of these particles is 5% by mass or less, preferably 1% by mass or less.

  Any method can be used for classifying coke powder, etc., as long as separation is possible. For example, sieving method, forced vortex type centrifugal classifier (micron separator, turboplex, turbo classifier, super separator), inertia classification, etc. An air classifier such as a machine (improved virtual impactor, elbow jet) can be used. A wet sedimentation method or a centrifugal classification method can also be used.

Furthermore, in order to obtain the graphite powder of the present invention, B simple substance, H ₃ BO ₃ , B ₂ O ₃ , B ₄ C, BN, etc. are added to the powder of coke before graphitization as a boron source and mixed well. To graphitize. If the boron compound is not uniformly mixed, not only the graphite powder becomes uneven, but also the possibility of sintering during graphitization increases. In order to mix uniformly, it is preferable that these boron sources are powders having a particle size of about 50 μm or less, preferably about 20 μm or less, and mixed with a powder such as coke. Moreover, it is preferable that the boron contained in (A) component of this invention is 0.05 mass%-5.0 mass% with respect to the amount of graphite powder. If the boron content is less than 0.05% by mass, the intended highly conductive graphite powder may not be obtained, which is not preferable. Even if the boron content exceeds 5.0% by mass, the improvement effect of the conductivity improvement of the graphite powder is small, which is not preferable.

  The graphitization temperature of the powder such as coke containing a boron source is preferably higher, but the range of 2500 to 3200 ° C. is preferable because of restrictions on the apparatus and the like. As the graphitization method, a method using an Atchison furnace in which powder is placed in a graphite crucible and directly energized, a method of heating powder with a graphite heating element, or the like can be used.

  The vapor grown carbon fiber of component (C) used in the present invention is, for example, from 800 to 1300 ° C. together with hydrogen gas in the presence of a transition metal catalyst such as ferrocene, using organic compounds such as benzene, toluene and natural gas as raw materials. It can be obtained by a thermal decomposition reaction. Furthermore, it is preferable to graphitize at about 2500-3200 degreeC after that. More preferably, it is graphitized at about 2500 to 3200 ° C. together with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum and silicon.

  In the present invention, it is preferable to use vapor grown carbon fiber having a fiber diameter of 0.05 to 10 μm and a fiber length of 1 to 500 μm, more preferably 0.1 to 5 μm and a fiber length of 5 to 50 μm. More preferably, the fiber diameter is 0.1 to 0.5 μm and the fiber length is 10 to 20 μm.

  In addition, the carbon nanotube of the component (C) of the present invention has recently attracted industrial attention not only for its mechanical strength but also for its field emission function and hydrogen storage function, and has also begun to pay attention to its magnetic function. This type of carbon nanotube is also called graphite whisker, filamentous carbon, graphite fiber, ultrafine carbon tube, carbon tube, carbon fibril, carbon microtube, carbon nanofiber, and the like. Carbon nanotubes include single-walled carbon nanotubes having a single graphite film forming a tube and multi-walled carbon nanotubes having multiple layers. In the present invention, both can be used, but a cured body having higher conductivity and mechanical strength is preferably obtained by using single-walled carbon nanotubes.

  Carbon nanotubes are produced, for example, by the arc discharge method, laser evaporation method, thermal decomposition method, etc. described in “Basics of Carbon Nanotubes” published by Corona (P23-P57, issued in 1998). It can be obtained by purification by a thermal method, a centrifugal separation method, an ultrafiltration method, an oxidation method or the like. More preferably, a high temperature treatment is performed in an inert gas atmosphere at about 2500 to 3200 ° C. to remove impurities. More preferably, a high temperature treatment is performed at about 2500 to 3200 ° C. in an inert gas atmosphere together with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum, and silicon.

  In the present invention, it is preferable to use carbon nanotubes having a fiber diameter of 0.5 to 100 nm and a fiber length of 0.01 to 10 μm, more preferably a fiber diameter of 1 to 10 nm and a fiber length of 0.05 to 5 μm. More preferably, the fiber diameter is 1 to 5 nm, and the fiber length is 0.1 to 3 μm.

  The fiber diameter and fiber length of vapor grown carbon fiber and carbon nanotube in the present invention can be measured with an electron microscope.

  In the present invention, the component (A) (graphite powder containing boron in the graphite crystal) and the component (C) (fiber phase carbon fiber having a fiber diameter of 0.05 to 10 μm and a fiber length of 1 to 500 μm and / or The mass ratio with respect to carbon nanotubes having a fiber diameter of 0.5 to 100 nm and a fiber length of 0.01 to 10 μm is preferably 60 to 99.9: 40 to 0.1, and 70 to 99:30. It is more preferable that it is -1, and it is still more preferable that it is 80-95: 20-5. If the ratio of component C exceeds 40, moldability may be deteriorated.

  When the electroconductive curable resin composition of this invention contains (C) component, the electroconductivity and mechanical strength of the hardening body increase further.

  As the curable resin of component (B) in the present invention, phenol resin, unsaturated polyester resin, epoxy resin, vinyl ester resin, alkyd resin, acrylic resin, melamine resin, xylene resin, guanamine resin, diallyl phthalate resin, allyl ester Resins, furan resins, imide resins, urethane resins, urea resins and the like can be mentioned.

  Among these, at least one curable resin selected from a phenol resin, an unsaturated polyester resin, an epoxy resin, a vinyl ester resin, and an allyl ester resin is preferable.

  Specific examples of the phenol resin in the present invention include a resol type phenol resin and a novolac type phenol resin.

  As the unsaturated polyester resin in the present invention, specifically, an orthophthalic acid type, an isophthalic acid type, a terephthalic acid type, an adipic acid type, a heptic acid type (HET acid; hexachloro-3,6) depending on a dibasic acid as a raw material. -Endomethylene-tetrahydrophthalic anhydride), 3,6-endomethylene-tetrahydrophthalic anhydride, maleic acid, fumaric acid, itaconic acid and the like.

  Specifically, as the epoxy resin in the present invention, bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, etc. Is mentioned.

  Specific examples of the vinyl ester resin in the present invention include novolac type vinyl ester resins and bisphenol type vinyl ester resins.

  Specific examples of the allyl ester resin in the present invention include esters of polyvalent carboxylic acids such as terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, ethylene glycol, propylene glycol, 1,4-butanediol, neo Examples include those produced from polyhydric alcohols such as pentyl glycol and allyl alcohol.

  Said curable resin can be used individually by 1 type or in mixture of 2 or more types. Moreover, the addition amount is 20-99.9: 80- in the mass ratio of the sum of (A) component and (C) component, and curable resin and / or curable resin composition (B), ie, A + C: B. The ratio is 0.1. However, the sum of the mass ratio is 100, and when the component (C) is not included, the mass ratio is A: B. When the addition amount of the component (B) exceeds 80% by mass and the graphite powder is less than 20% by mass, the conductivity of the cured product is lowered.

  In particular, in a field where airtightness is required, it is preferable to select a resin that does not generate gas in the curing reaction, such as a combination of an epoxy resin and a phenol resin, an unsaturated polyester resin, a vinyl ester resin, or an allyl ester resin. By using these resins, it is possible to obtain a molded product having high airtightness without voids in the cured product.

  Furthermore, in fields where heat resistance, acid resistance and the like are required, resins having a molecular skeleton such as bisphenol A type, novolac type, and cresol novolak type are preferable. For example, in the case of a combination of an epoxy resin and a phenol resin, an epoxy resin containing a cresol novolac type epoxy resin and a phenol resin containing a novolac type phenol resin can improve heat resistance, chemical resistance, and airtightness, which is preferable. As mentioned. Furthermore, it is preferable that the vinyl ester resin contains a novolac-type vinyl ester resin because heat resistance, chemical resistance, airtightness, and moldability can be improved.

  In the present invention, as a component of the curable resin composition of the component (B), a monomer such as an allyl ester monomer, an acrylate ester monomer, a methacrylic ester monomer, and a styrene monomer may be added to the curable resin. it can.

  Specific examples of the allyl ester monomer in the present invention include diallyl phthalate, diallyl isophthalate, dimethallyl isophthalate, diallyl terephthalate, diallyl 2,6-naphthalenedicarboxylate, diallyl 1,5-naphthalenedicarboxylate, 1,4- Examples include aromatic allyl carboxylates such as allyl xylene dicarboxylate, diallyl 4,4′-diphenyldicarboxylate, and diallyl cyclohexanedicarboxylate.

  Specific examples of acrylic acid ester monomers and methacrylic acid ester monomers include phenoxyethyl methacrylate, isononyl methacrylate, benzyl methacrylate, dicyclopentenyloxyethyl (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerin di (meta). ) Acrylate, 1,6-hexanediol diacrylate and the like. Furthermore, these halogen-substituted compounds can be used for the purpose of imparting flame retardancy.

  Examples of the styrene monomer include styrene, α-methylstyrene, chlorostyrene, styrene sulfonic acid, 4-hydroxystyrene, vinyl toluene, divinyl benzene, and the like. Of these, styrene is preferred.

  The curing agent in the present invention is preferably a radical polymerization initiator, and examples of the radical polymerization initiator include organic peroxides and photopolymerization initiators. In the present invention, an organic peroxide is more preferable. As the organic peroxide, known compounds such as dialkyl peroxides, acyl peroxides, hydroperoxides, ketone peroxides, and peroxyesters can be used. Specific examples include benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, 2,5-dimethyl2,5-di (2-ethylhexanoyl) peroxyhexane, t-butylperoxybenzoate, Examples thereof include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-dibutylperoxyhexane, and the like.

  Examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, benzophenone, and 2-methyl-1- (4-methylthiophenyl) -2. -Monfolinopropane-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one, 2, Examples include 4,6-trimethylbenzoyldiphenylphosphine oxide. These radical polymerization initiators may be used alone or in combination of two or more.

  Further, the conductive curable resin composition of the present invention has glass fiber, carbon fiber, UV stabilizer, oxidation agent for the purpose of improving hardness, strength, conductivity, moldability, durability, weather resistance, water resistance, etc. Additives such as an inhibitor, an antifoaming agent, a leveling agent, a mold release agent, a lubricant, a water repellent, a thickener, a low shrinkage agent, and a hydrophilicity imparting agent can be added.

  In order to obtain the conductive curable resin composition of the present invention, each of the above components is a mixer generally used in the resin field such as a roll, an extruder, a kneader, a Banbury mixer, a Henschel mixer, a planetary mixer, It is preferable to use a kneader and mix as uniformly as possible while maintaining a constant temperature at which curing does not start. Moreover, when adding a radical polymerization initiator, after mixing all other components uniformly, it is good to add and mix a radical polymerization initiator at the end.

  The obtained conductive curable resin composition can be made into the shape of powder, granules, pellets, tablets, sheets, etc., and used for the final molding step.

  The method for molding the conductive curable resin composition of the present invention is not particularly limited, but it can be formed into a desired shape using a generally known molding method such as compression molding, transfer molding, injection molding or injection compression molding. While shaping, it can be heated and cured. Moreover, about resin which has an unsaturated bond, a high energy ray can be irradiated, a radical can be generated, and it can be hardened. As the conditions for heat curing, it is important to select and search for the optimum temperature according to the type of composition. For example, it can be appropriately determined within a temperature range of 120 to 200 ° C. and a heating range of 30 seconds to 1200 seconds. Further, after the thermoforming, complete curing can be carried out by performing after-curing for 10 minutes to 600 minutes in a temperature range of 150 to 200 ° C.

  Moreover, the conductive curable resin composition of the present invention has good workability and workability without containing an organic solvent. This point is very valuable in recent years as safety for workers and preservation of the global environment have become important. Of course, in order to further improve the molding processability of the conductive curable resin composition of the present invention, it is possible to further improve the fluidity by adding a solvent.

As the conductive cured body of the present invention, those having the characteristics described below are preferable. That is, the volume resistivity is preferably 2 × 10 ⁻² Ωcm or less, more preferably 8 × 10 ⁻³ Ωcm or less, and particularly 5 × 10 ⁻³ Ωcm or less is suitably used for a fuel cell separator. The contact resistance is preferably 2 × 10 ⁻² Ωcm ² or less, more preferably 1 × 10 ⁻² Ωcm ² or less, and particularly preferably 7 × 10 ⁻³ Ωcm ² or less. The thermal conductivity is preferably 1.0 W / m · K or more, more preferably 4.0 W / m · K or more, and particularly preferably 10 W / m · K or more. Further, air permeability is an important characteristic value is preferably at most 1 × 10 ^-6 cm ² / sec as a separator for a fuel cell, more preferably not more than ^{1 × 10 -8 cm 2 / sec} , especially 1 × 10 ^{- 9} cm ² / sec or less is suitable.

  In addition, the cured product of the conductive curable resin composition of the present invention is an extremely high performance composite material that can reproduce the conductivity and thermal conductivity of graphite as much as possible and is excellent in heat resistance, corrosion resistance, molding accuracy, and the like. is there. Therefore, it is useful in various applications such as various parts such as the electronics field, electrical machinery, machinery, and vehicles, and in particular, a fuel cell separator material can be cited as a preferred example.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the examples.

The materials used are shown below.
Component (A) (graphite powder) A-1 to A-4: LPC-S coke (hereinafter referred to as “coke A”) manufactured by Nippon Steel Chemical Co., Ltd., which is non-acicular coke (calcined product), is used as a pulverizer [Hosokawa Micron. Co., Ltd.] and coarsely pulverized to a size of 2 mm to 3 mm or less. The coarsely pulverized product was finely pulverized with a jet mill (IDS2UR, manufactured by Nippon Pneumatic Co., Ltd.). Then, it adjusted to the desired particle size by classification. For removing particles of 5 μm or less, air classification was performed using a turbo classifier (TC15N, manufactured by Nisshin Engineering Co., Ltd.). 0.6 kg of boron carbide (B ₄ C) was added to 14.4 kg of a part of this finely pulverized product, and mixed at 800 rpm with a Henschel mixer for 5 minutes. This was sealed in a graphite crucible with a lid having an inner diameter of 40 cm and a volume of 40 liters, and placed in a graphitization furnace using a graphite heater and graphitized at a temperature of 2900 ° C. After standing to cool, the powder was taken out to obtain 14 kg of powder.

A-5: Coke A was coarsely pulverized to a size of 2 mm to 3 mm or less with a pulverizer. This coarsely pulverized product was finely pulverized with a jet mill. Then, it adjusted to the desired particle size by classification. For removing particles of 5 μm or less, air classification was performed using a turbo classifier. This was sealed in a graphite crucible with a lid having an inner diameter of 40 cm and a volume of 40 liters, and placed in a graphitization furnace using a graphite heater and graphitized at a temperature of 2900 ° C. After standing to cool, the powder was taken out to obtain 14 kg of powder.

A-6, A-8, A-9: Coke A was put into a similar graphitization furnace as it was and graphitized at a temperature of 2800 ° C. After allowing to cool, the powder was taken out, and a portion of 15 kg of the powder was coarsely pulverized to a size of 2 mm to 3 mm or less with a pulverizer. This coarsely pulverized product was finely pulverized with a jet mill. Then, it adjusted to the desired particle size by classification.

A-7: Nippon Steel Chemical Co., Ltd. LPC-UL, which is acicular coke (calcined product), was placed in the same graphitization furnace as it was and graphitized at a temperature of 2800 ° C. After allowing to cool, the powder was taken out, and a portion of 15 kg of the powder was coarsely pulverized to a size of 2 mm to 3 mm or less with a pulverizer. This coarsely pulverized product was finely pulverized with a jet mill. Then, it adjusted to the desired particle size by classification. The adjusted removal of particles of 5 μm or less was performed by air classification using a turbo classifier.

  Table 1 shows the physical properties of the component (A), A-1 to A-9.

  (B) component (curable resin and / or curable resin composition) The curable resin composition mixed in the composition described in Table 3 using the material described in Table 2, or the curable resin described in Table 2 ( B) Component B-1 to B-8.

(C) Component C-1: VGCF-G: Gas phase method carbon fiber manufactured by Showa Denko KK (fiber diameter 0.1 to 0.3 μm, fiber length 10 to 50 μm)

C-2: CNT: Carbon nanotube 6 mm in diameter and 50 mm in length on a graphite rod, a hole with a diameter of 3 mm and a depth of 30 mm is made from the tip along the central axis, and rhodium (Rh): platinum (Pt): Graphite (C) was packed as a mixed powder with a weight ratio of 1: 1: 1 to produce an anode. On the other hand, a cathode having a diameter of 13 mm and a length of 30 mm made of graphite having 99.98% purity was produced. These electrodes were placed opposite to the reaction vessel and connected to a DC power source. Then, the inside of the reaction vessel was replaced with helium gas having a purity of 99.9%, and DC arc discharge was performed. Thereafter, soot (chamber soot) adhering to the inner wall of the reaction vessel and soot deposited on the cathode (cathode soot) were collected. The pressure and current in the reaction vessel were 600 Torr and 70A. During the reaction, the operation was performed so that the gap between the anode and the cathode was always 1 to 2 mm.

  The recovered soot was ultrasonically dispersed in a 1: 1 mixed solvent of water and ethanol, the dispersion was recovered, and the solvent was removed with a rotary evaporator. The sample was ultrasonically dispersed in a 0.1% aqueous solution of benzalkonium chloride, which is a cationic surfactant, and then centrifuged at 5000 rpm for 30 minutes to recover the dispersion. Further, the dispersion was purified by heat treatment in air at 350 ° C. for 5 hours to obtain carbon nanotubes having a fiber diameter of 1 to 10 nm and a fiber length of 0.05 to 5 μm.

  A method for measuring the physical properties of the cured product is shown below.

  The air permeability was measured in accordance with JIS K7126 A method using nitrogen gas at 23 ° C.

  The volume resistivity was measured by a four-probe method according to JIS K7194.

  The compressive strength was measured in accordance with JIS K7181, with a test piece (20 mm × 20 mm × 2 mm) being subjected to a compression speed of 1 mm / min.

  The bending strength and bending elastic modulus were measured by a three-point bending strength measurement method on a test piece (80 mm × 10 mm × 4 mm) under the conditions of a span interval of 64 mm and a bending speed of 2 mm / min in accordance with JIS K6911.

  The specific gravity was measured according to JIS K7112 Method A (submersion method in water).

The thermal conductivity was measured using a laser flash method (t _1/2 method, laser flash method thermal constant measuring device LF / TCM FA8510B, manufactured by Rigaku Denki Co., Ltd.), with a test piece (φ10 mm, thickness 1.7 mm) at a temperature of 80 ° C. and vacuum The measurement was performed under the conditions of irradiation light ruby laser light (excitation voltage 2.5 kV).

For the contact resistance value, the test piece 11 (20 mm × 20 mm × 2 mm) and the carbon plate 12 (1.5 × 10 ⁻³ Ωcm, 20 mm × 20 mm × 1 mm) were brought into contact with each other using the apparatus shown in FIG. Then, a load of 98N is applied. A resistance value was calculated by flowing a constant current of 1 A in the penetration direction, bringing the terminal 14 into contact with the interface between the test piece 11 and the carbon plate 12 and measuring the voltage. The cross-sectional area in contact with the value is integrated to obtain a contact resistance value.

  The heat resistance is evaluated in three stages, in which a bending test piece is left in a perfect oven at a temperature of 140 ° C. in an air atmosphere for 2000 hours, and the rate of change in bending strength thereafter is 20% or less, 20 to 50%, or 50% or more. Compared.

  The acid resistance was compared in a three-stage evaluation in which a 5% sulfuric acid aqueous solution was maintained at a temperature of 90 ° C. and immersed for 100 hours, and thereafter the bending strength change rate was 20% or less, 20 to 50%, or 50% or more.

  The spiral flow was molded at a pressure of 10 MPa using a transfer molding machine 50t, and the spiral flow length was measured.

Reference Examples 1 to 6, Examples 7 and 8, Reference Examples 10 to 13, 17, 19 to 20 and Comparative Examples 1 to 7, 9 to 12, and 16 to 18 are universal mixing agitators having a mechanism in which the stirring blades rotate and revolve. Were mixed while kneading for 30 minutes at a temperature of 40 ° C. to obtain a resin composition. The obtained resin composition was excellent in storage stability with no change in its properties even after storage at 23 ° C. for 3 months. In addition, 0.05 mass part of hydroquinone was added as a polymerization inhibitor with respect to the total amount of a resin composition.

The obtained resin composition was heated under pressure at 140 ° C. for 5 minutes using a compression molding machine and cured to form a cured body having a thickness of 100 mm × 100 mm × 2 mm. In addition, about the reference example 14 which uses dicumyl peroxide as a polymerization initiator, it heated and pressurized at 180 degreeC for 5 minute (s), and it was made to harden | cure.

Reference Examples 9, 14 to 16, and 17 and Comparative Examples 8 and 13 to 15 were kneaded at a temperature of 80 ° C. for 15 minutes using a kneader to obtain resin compositions. The obtained resin composition was heated under pressure at 180 ° C. for 5 minutes using a compression molding machine and cured to obtain a cured product.

The composition ratios (mass ratios) of the above Reference Examples, Examples and Comparative Examples are shown in Tables 4, 6 and 8, and the physical property measurement results are shown in Tables 5, 7 and 9. Table 10 shows the results of spiral flow performed in Reference Examples 2, 17 to 20, and Comparative Examples 16 to 18.

  Table 1 shows that graphite with high crystallinity was obtained by narrowing the lattice spacing by graphitizing with boron. The hardened | cured material of the conductive curable resin composition using these graphites had a highly conductive hardened body compared with the example using the graphite without boron. Among them, by using graphite having a large tapping bulk density and graphite having a wide particle size distribution and a large particle size, an even higher conductive cured body was obtained.

  Accordingly, sufficient conductivity is exhibited even when the amount of resin is increased, and thus the moldability can be improved while maintaining the desired high conductivity.

  The moldability was further improved by using graphite powder having a small aspect ratio. However, when there is a graphite powder having a particle size of 80 μm or more, the fluidity is lowered, resulting in molding failure.

  A composition using a novolac type epoxy resin, vinyl ester resin, or phenol resin as the curable resin has improved acid resistance and heat resistance. However, in the reaction with only the phenol resin, water was generated and a large number of pores were formed in the cured body, and the air permeability was poor due to the influence.

It is a figure showing the measuring method of the electrical resistivity of graphite powder. It is a figure explaining the calculation method of the electrical specific resistance of graphite powder. It is a figure showing the measuring method of the contact resistance of a hardening body.

Explanation of symbols

1 Electrode (+)
1 'electrode (-)
2 compression rod 3 cradle 4 side frame 5 sample 6 voltage measurement terminal 11 test piece 12 carbon plate 13 copper plate 14 terminal

Claims (19)

  (A) graphite powder containing boron in graphite crystal, (B) curable resin and / or curable resin composition, and (C) fiber diameter is 0.05 to 10 μm, and fiber length is 1 to 500 μm. A conductive curable resin composition comprising vapor-grown carbon fibers and / or carbon nanotubes having a fiber diameter of 0.5 to 100 nm and a fiber length of 0.01 to 10 μm.   The mass ratio (A + C: B) of the sum of the component (A) and the component (C) and the component (B) is 20 to 99.9: 80 to 0.1 (sum is 100). The conductive curable resin composition according to claim 1.   The mass ratio of the component (A) to the component (C) (sum is 100) is 60 to 99.9: 40 to 0.1. Conductive curable resin composition. In a state where the bulk density of the graphite powder of component (A) is pressed to 1.5 g / cm ³ , the powder electrical resistivity of component (A) in the direction perpendicular to the pressing direction is 0.06 Ωcm or less The conductive curable resin composition according to claim 1, wherein the composition is a conductive curable resin composition.   5. The conductive curable resin composition according to claim 1, wherein the average particle size of the component (A) is 5 μm to 80 μm. The component (A) is a graphite powder having a specific surface area of 3 m ² / g or less, an aspect ratio of 6 or less, a tapping bulk density of 0.8 g / cm ³ or more, and a lattice spacing (Co value) of 6.745 Å or less. The conductive curable resin composition according to any one of claims 1 to 5, wherein:   The conductive curable resin composition for molding according to any one of claims 1 to 6, wherein the component (A) is a graphite crystal using coke as a raw material.   The component (B) contains at least one selected from a phenol resin, an unsaturated polyester resin, an epoxy resin, a vinyl ester resin, and an allyl ester resin, and a curing agent. The conductive curable resin composition according to claim 1.   The conductive curable resin composition according to claim 8, wherein the component (B) contains an epoxy resin and a phenol resin.   The conductive curable resin composition according to claim 9, wherein the epoxy resin includes a cresol novolac type epoxy resin, and the phenol resin includes a novolac type phenol resin.   Component (B) comprises a vinyl ester resin and / or an allyl ester resin and at least one monomer selected from allyl ester monomers, acrylic ester monomers, methacrylic ester monomers, and styrene monomers, and a radical polymerization initiator. The conductive curable resin composition according to claim 8.   The conductive curable resin composition according to claim 11, wherein the vinyl ester resin is a novolac type vinyl ester resin.   The conductive curable resin composition according to any one of claims 1 to 12, wherein the component (A) is a graphite powder containing 0.05% by mass to 5.0% by mass of boron. object. A volume specific resistance obtained by curing the conductive curable resin composition according to claim 1 is 2 × 10 ⁻² Ωcm or less, a contact resistance is 2 × 10 ⁻² Ωcm ² or less, and heat A conductive cured body having a conductivity of 1.0 W / m · K or more.   The method for producing a conductive cured body according to claim 14, wherein the molding is performed by any one of compression molding, transfer molding, injection molding, and injection compression molding. The conductive curable resin composition according to claim 1, wherein the sum of the component ( A) and the component (C) is 50% by mass to 95% by mass. The volume resistivity obtained by curing the product is 2 × 10 ⁻² Ωcm or less, the contact resistance is 2 × 10 ⁻² Ωcm ² or less, the thermal conductivity is 1.0 W / m · K or more, and the air permeability is 1 ×. A separator for a fuel cell, which is 10 ⁻⁶ cm ² / sec or less. The conductive curable resin composition according to any one of claims 1 to 13, wherein the sum of the component ( A) and the component (C) is 50% by mass to 95% by mass. The volume resistivity obtained by curing is 2 × 10 ⁻² Ωcm or less, the contact resistance is 2 × 10 ⁻² Ωcm ² or less, the thermal conductivity is 1.0 W / m · K or more, and the air permeability is 1 × 10. ^A method for producing a fuel cell separator, wherein the fuel cell separator is molded by compression molding, transfer molding, injection molding, or injection compression molding, wherein the separator is ^-6 cm ² / sec or less .   A conductive cured body obtained by curing the conductive curable resin composition according to claim 1. The conductive curable resin composition according to claim 1, wherein the sum of the component ( A) and the component (C) is 50% by mass to 95% by mass. A fuel cell separator obtained by curing a product.

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