JP4889962B2 - Conductive structure, method for producing the same, and separator for fuel cell - Google Patents

Description

  The present invention relates to a method for manufacturing a conductive structure. More specifically, the present invention is composed of a crystalline thermoplastic resin composite material containing a conductive filler, and has an excellent electrical conductivity and heat resistance obtained by increasing the crystallinity of the composite material. And a method for manufacturing a fuel cell separator.

  Conventionally, metals and carbon materials have been mainly used for applications that require high electrical conductivity. However, with the recent diversification of uses of conductive materials in the fields of electronics, electrochemistry, energy, transportation equipment, etc., the role that conductive resin compositions as a kind of conductive materials should play has increased. As a result, the conductive resin composition has made remarkable progress in improving performance and functionality. An important factor is that molding processability is greatly improved by combining with a polymer material.

  In the conductive resin composition, it is important to effectively develop conductivity without substantially impairing mechanical properties and moldability. Applications that require electrical conductivity include electronic materials such as circuit boards, resistors, laminates, and electrodes, heaters, heating devices, dust collection filter elements, PTC elements, electronics in recent years, in addition to conventional applications. A part, a semiconductor part, etc. are mentioned. In these applications, high heat resistance is required along with conductivity.

  In other aspects, in recent years, fuel cells have attracted attention from the viewpoint of environmental problems, energy problems, and the like. A fuel cell is a clean power generation device that uses hydrogen and oxygen to generate power by the reverse reaction of electrolysis and has no emissions other than water. Also in this fuel cell field, the conductive resin composition can play a major role. Fuel cells are classified into several types depending on the type of electrolyte. Among these, polymer electrolyte fuel cells are most promising for automobiles and consumer use because they operate at low temperatures. Such a fuel cell can achieve high output power generation by stacking, for example, single cells composed of a polymer solid electrolyte, a gas diffusion electrode, a catalyst, and a separator.

In the fuel cell having the above configuration, a separator for partitioning a single cell is usually supplied with a fuel gas (hydrogen, etc.) and an oxidant gas (oxygen, etc.), and a flow for discharging the generated moisture (water vapor). A path (groove) is formed. Therefore, the separator is required to have high gas impermeability capable of completely separating these gases and high conductivity in order to reduce the internal resistance.
Furthermore, the separator is required to have excellent thermal conductivity, durability, strength, and the like.

  In order to achieve these requirements, the fuel cell separator has conventionally been studied from both metallic materials and carbon materials. Among these materials, regarding metal materials, attempts have been made to coat noble metals and carbon on the surface due to the problem of corrosion resistance. However, sufficient durability cannot be obtained, and the cost of coating becomes a problem.

  On the other hand, many studies have been made on carbon materials, and a molded product obtained by press-molding an expanded graphite sheet, a molded product obtained by impregnating and curing a resin in a carbon sintered body, and a product obtained by firing a thermosetting resin. Examples of the fuel cell separator material include glassy carbon, molded products obtained by mixing carbon powder and resin, and the like.

  For example, Patent Document 1 discloses an isotropic graphite obtained by adding a binder to carbonaceous powder, heating and mixing, then performing CIP molding (cold isostatic pressing), then firing and graphitizing. A complicated process is disclosed in which after a material is impregnated with a thermosetting resin and cured, the groove of the gas flow path is carved by cutting.

In addition, attempts have been made to improve the performance of the separator by devising the composition. For example, Patent Document 2 discloses a separator having excellent mechanical characteristics and electrical characteristics by combining a carbonaceous powder coated with a resin and a resin having higher heat resistance than the coating resin. ing.
Patent Document 3 discloses a resin composition composed of a mixture of a low melting point metal, a metal powder, a thermoplastic, and a thermoplastic elastomer.

On the other side, attempts have been made to produce a high-performance separator by a simple method by devising a molding method. For example, in Patent Document 4, the mold is heated in advance to a temperature equal to or higher than the melting point of the thermoplastic resin, the conductive composition is filled in the mold cavity in a heated state, and melted to be uniform at a predetermined pressure. A method for producing an electrically conductive molded article is disclosed in which it is shaped by compression and cooled to a temperature lower than the thermal deformation temperature of the thermoplastic resin while pressure is applied to the mold. In Patent Documents 5 and 6, injection molding is carried out by setting the cavity surface temperature at a temperature higher than the crystallization temperature of the thermoplastic resin composition by 50 ° C. and lower than the melting point of the composition. A method for molding a highly conductive resin molded product is disclosed.
JP-A-8-222241. JP2003-257446A. JP 2000-348739 A. JP2003-109622A. JP 2004-35826 A. JP 2004-34611 A.

  Various conductive structures made of the conventional conductive resin composition described in the above-mentioned patent document need to greatly increase the filling amount of the conductive filler in order to develop high conductivity. In order to maintain the properties, the resin content has to be increased, so that sufficiently high conductivity cannot be obtained. Furthermore, in order to obtain high conductivity, if the structure includes a baking process in which the structure is heated at a high temperature of 1000 to 3000 ° C. for a long time, the time required for the manufacturing becomes long and the manufacturing process becomes complicated and the cost is increased. There was a problem that would rise.

  In addition, the molding method has been devised, but the method of changing the temperature of the entire mold as in Patent Document 4 requires a lot of time and energy, so that a molded product cannot be manufactured at low cost. . Furthermore, the electrical conductivity required for the structure cannot be achieved if the mold temperature is lowered at random. Further, as in Patent Documents 5 and 6, it is efficient to mold by changing only the cavity surface temperature, but when the surface temperature is set to a temperature lower than the melting temperature of the thermoplastic resin composition, a large amount of When molding a highly conductive composition that contains a conductive filler and has high thermal conductivity and very fast solidification, solidification of the resin starts before shaping is completed, so molding with good dimensional accuracy It is often difficult to obtain a product.

  The objective of this invention is providing the manufacturing method of the electroconductive structure which has the outstanding electroconductivity which eliminated the fault of the prior art as mentioned above. It is another object of the present invention to provide a method for manufacturing a fuel cell separator having high dimensional accuracy and excellent conductivity.

  As a result of intensive research to solve the above problems, the present inventors have increased the crystallinity of a conductive structure composed of a crystalline thermoplastic resin composition, which is high in a simple and cost-effective manner. The inventors have found that conductivity can be expressed, and have completed the present invention. The present invention is based on the above findings. More specifically, the present invention includes, for example, the following items [1] to [18].

[1]
In the molding of a conductive structure made of a crystalline thermoplastic resin composite material containing at least a crystalline thermoplastic resin and a conductive filler, until the molding of the molten composite material in the mold is completed When the mold cavity surface temperature is defined as the crystal melting temperature (T _m ) of the composite material, it is kept at (T _m +5) ° C. or higher, and after shaping, the crystallization temperature of the composite material is adjusted to T _C And a temperature of the mold cavity is not lower than T _{C and not} higher than (T _C +15) ° C., and the composite material is solidified.
[2]
The conductive structure is solidified in a state in which the conductive structure is pressed with a mold, or in a state in which the conductive structure is pressed between correction plates that prevent deformation of the conductive structure. The method for producing a conductive structure according to [1].
[3]
The conductive structure according to [1] or [2], wherein the molding of the conductive structure is any molding method selected from injection molding, injection compression molding, compression molding, and stamping molding. Manufacturing method of structure.
[4]
The method for producing a conductive structure according to any one of [1] to [3], wherein the crystalline thermoplastic resin composite material further contains an elastomer.
[5]
Crystalline thermoplastic resin, the elastomer and other polymer compounds as a polymer component, the total of the polymer component and a conductive filler as a reference (100 mass%), the polymer component is 40-2 wt%, conductivity The method for producing a conductive structure according to any one of [1] to [4], wherein the conductive filler is 60 to 98% by mass.
[6]
At least 1 component contained in the said crystalline thermoplastic resin is polyolefin, The manufacturing method of the electroconductive structure in any one of [1] to [5] characterized by the above-mentioned.
[7]
Polymer components including crystalline thermoplastic resins, elastomers and other polymer compounds are hydrogenated styrene butadiene rubber, styrene / ethylene butylene / styrene block copolymers, styrene / ethylene propylene / styrene block copolymers, olefin crystals / ethylene butylene, One or more of olefin crystal block copolymer, styrene / ethylene butylene / olefin crystal block copolymer, styrene / isoprene / styrene block copolymer and styrene / butadiene / styrene block copolymer, and at least polyolefin The method for producing a conductive structure according to [5] .
[8]
The method for producing a conductive structure according to [5], wherein the polymer component including the crystalline thermoplastic resin, elastomer and other polymer compound contains at least polyvinylidene fluoride and a soft acrylic resin.
[9]
Any one of [1] to [8], wherein the conductive filler is at least one selected from the group consisting of a metal material, a carbonaceous material, a conductive polymer, a metal-coated filler, or a metal oxide. The manufacturing method of the electroconductive structure as described in a term.
[10]
The method for producing a conductive structure according to any one of [1] to [9], wherein the conductive filler is a carbonaceous material containing 0.05 to 5% by mass of boron. .
[11]
[1] to [10], wherein the conductive filler contains 0.1 to 50% by mass of vapor grown carbon fiber and / or carbon nanotube (based on the whole conductive filler including these). The manufacturing method of the electroconductive structure of any one of these.
[12]
The method for producing a conductive structure according to claim [11], wherein the vapor-grown carbon fiber or the carbon nanotube contains 0.05 to 5% by mass of boron.
[ 13 ]
A conductive structure manufactured by the manufacturing method according to any one of [1] to [12] and satisfying a relationship represented by X ≧ 0.8 × Y (Formula 1) .
(However, in Formula 1, X represents a part of the conductive structure as a sample, and a differential melting calorimeter at a rate of temperature increase of 20 ° C./minute from 25 ° C. to the crystal melting temperature of the thermoplastic resin composite material: T _This represents the value obtained by dividing the heat of fusion of the crystal observed when the temperature is raised to 60 ° C. higher than _m by the mass of the sample, and the unit is J / g, and Y is a crystalline thermoplastic resin composite Using the material as a sample, using a differential scanning calorimeter, holding at 60 ° C. or higher than T _m for 10 minutes, cooling to 25 ° C. at a cooling rate of 5 ° C./min, and holding at 25 ° C. for 10 minutes Furthermore, it represents a value obtained by dividing the heat of fusion of the crystal observed when the temperature is raised to a temperature 60 ° C. higher than _{Tm at a} rate of temperature increase of 20 ° C./min divided by the mass of the sample, and the unit is J / g. is there.)
[ 14 ]
[13] A separator for a fuel cell using the conductive structure according to [13] .

  Since the conductive structure manufactured by the manufacturing method of the present invention having the above-described structure is excellent in conductivity and heat dissipation, it is difficult to realize materials in areas that have been difficult to realize in the past, such as electronics, It can be widely applied to various uses and parts such as products, machine parts, and vehicle parts, and is particularly useful as a separator for fuel cells.

  Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary. In the following description, “parts” and “%” representing the quantity ratio are based on mass unless otherwise specified.

(Crystalline thermoplastic resin composite material)
The crystalline thermoplastic resin composite material of the present invention is a composite material containing at least a crystalline thermoplastic resin (A component) and a conductive filler (B component).

(Conductive structure)
The conductive structure of the present invention refers to a material obtained by shaping the crystalline thermoplastic resin composite material into a certain shape by injection molding or the like. Although the composition is exactly the same as the original crystalline thermoplastic resin composite material, the degree of crystallization differs depending on the thermal history during molding.

(Polymer component)
In addition to the crystalline thermoplastic resin (component A), the crystalline thermoplastic resin composite material of the present invention contains other high molecular compounds such as an elastomer component (component C), an amorphous thermoplastic resin, and a thermosetting resin. It may be included. A component, C component, and other polymer compounds are collectively referred to as a polymer component.
(Crystalline thermoplastic resin: Component A)
The crystalline thermoplastic resin of the present invention is not particularly limited, but polyvinyl chloride, polyimide, liquid crystal polymer, polyether ether ketone, fluororesin such as polyvinylidene fluoride and tetrafluoropolyethylene, polyolefin such as polyethylene and polypropylene, One or more combinations selected from polyacetal, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyphenylene oxide, polyphenylene sulfone and the like can be used. Among these, polypropylene, polyvinylidene fluoride, polyphenylene sulfide, and a liquid crystal polymer are preferable. Polypropylene is particularly preferred because large bending strain is obtained and hydrolysis resistance is high.

(Elastomer: C component)
Further, the crystalline thermoplastic resin composite material of the present invention may contain an elastomer component. An elastomer is a polymer having rubber-like elasticity near normal temperature. The elastomer component is not particularly limited. For example, acrylonitrile butadiene rubber, hydrogenated nitrile rubber, styrene butadiene rubber, ethylene propylene rubber, ethylene propylene diene terpolymer rubber, ethylene butadiene rubber, fluoro rubber, isoprene rubber, silicone rubber, Acrylic rubber, butadiene rubber, high styrene rubber, chloroprene rubber, urethane rubber, polyether special rubber, ethylene tetrafluoride / propylene rubber, epichlorohydrin rubber, norbornene rubber, butyl rubber, styrene thermoplastic elastomer, olefin thermoplastic Elastomers, urethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, 1,2-polybutadiene thermoplastic elastomers, Tsu Motokei thermoplastic elastomer, the Awa set of 1-2 or more selected from among such soft acrylic resin can be used.

The content of the elastomer contained in the crystalline thermoplastic resin composite material of the present invention is not particularly limited, but is preferably 0.01 to 50% by mass based on the polymer component (100% by mass). When the elastomer component is 50% by mass or more, the effect of the present invention is reduced.
Furthermore, 0.01-30 mass% is especially preferable because the effect of this invention appears large and a high bending strain and bending strength are obtained simultaneously.

  Among the polymer components containing the above-mentioned elastomer, polypropylene / styrene thermoplastic elastomer blends, polyvinylidene fluoride / fluorine elastomer blends, polyvinylidene fluoride / soft acrylic resin blends, polyphenylene sulfide / styrene thermoplastic elastomers are preferred. Blends and the like are preferred. Of these, polypropylene / styrene thermoplastic elastomer blends and polyphenylene sulfide / styrene thermoplastic elastomer blends are particularly preferred from the viewpoints of obtaining large bending strain and high hydrolysis resistance.

Examples of the styrenic thermoplastic elastomer used in the crystalline thermoplastic resin composite material of the present invention include hydrogenated styrene butadiene rubber, styrene / ethylene butylene / styrene block copolymer, styrene / ethylene propylene / styrene block copolymer, olefin crystal / ethylene butylene. • Olefin crystal block copolymer, styrene / ethylene butylene / olefin crystal block copolymer, styrene / isoprene / styrene block copolymer, styrene / butadiene / styrene block copolymer, and the like. Of these, hydrogenated styrene butadiene rubber, styrene / ethylene butylene / styrene block copolymer, and styrene / ethylene propylene / styrene block copolymer are preferred because of their good dispersibility in the crystalline thermoplastic resin.

(Amorphous thermoplastic resin)
In addition, the crystalline thermoplastic resin composite material of the present invention may contain an amorphous thermoplastic resin as long as the effects of the present invention are not lost. Such an amorphous thermoplastic resin is not particularly limited, and for example, one or more combinations selected from polystyrene, acrylic resin, polycarbonate, polycycloolefin and the like can be used.

  Furthermore, it is preferable to use a high molecular weight resin as much as possible as the thermoplastic resin used in the crystalline thermoplastic resin composite material of the present invention because excellent bending characteristics can be obtained. For example, when polypropylene is used as the crystalline thermoplastic resin, it is preferable to use polypropylene having a melt flow rate (MFR) of 10 or less. Particularly preferred is a polypropylene resin having an MFR of 2 or less because both excellent bending strain and bending strength are compatible. Here, MFR was measured at a temperature of 230 ° C. and a load of 2.16 kg according to JIS K 6921-2.

(Other ingredients)
In addition to these polymer components, various additives, for example, thermosetting resins, monomers, plasticizers, curing agents, curing initiators, curing aids, solvents, UV stabilizers, antioxidants, as necessary. In addition, a component selected from a heat stabilizer, an antifoaming agent, a leveling agent, a mold release agent, a lubricant, a water repellent, a thickener, a low shrinkage agent, a flame retardant, or a hydrophilicity imparting agent can be added.

(Method for producing polymer component)
The production method of the component A of the present invention is not particularly limited, and examples thereof include physical methods such as solution method, emulsion method, melting method, graft polymerization method, block polymerization method, IPN (interpenetrating polymer network) method and the like. The manufacturing method by a chemical method is mentioned.

  In the case of producing a polymer component by blending different polymers, the melting method is preferable from the viewpoint of diversity. The specific method of the melting method is not particularly limited, and examples thereof include a method of blending using a kneading machine such as a roll, a kneader, a Banbury mixer, and an extruder.

(Conductive filler: B component)
In the present invention, the B component constituting the crystalline thermoplastic resin composite material together with the above-described A component is not particularly limited as long as it is a conductive filler. From the viewpoint of conductivity, the B component is preferably a combination of one or more selected from a metal material, a carbonaceous material, a conductive polymer, a metal-coated filler, or a metal oxide. More preferably, it is a carbonaceous material and / or a metal material.

(Metal material)
As the metal material, from the viewpoint of conductivity, Ni, Fe, Co, B, Pb, Cr, Cu, Al, Ti, Bi, Sn, W, P, Mo, Ag, Pt, Au, TiC, NbC, It is preferably a composite material of one kind or two or more kinds of TiCN, TiN, CrN, TiB ₂ , ZrB ₂ , and Fe ₂ B. Furthermore, these metal materials can be used after being processed into powder or fiber.

(Carbonaceous material)
As the carbonaceous material, 1 to 2 selected from carbon black, carbon fiber, amorphous carbon, expanded graphite, artificial graphite, natural graphite, vapor grown carbon fiber, carbon nanotube, and fullerene from the viewpoint of conductivity. More than one type of combination can be mentioned.

Furthermore, it is preferable that 0.05-5 mass% of boron is contained in a carbonaceous material from the point of the electroconductivity improvement of a carbon material. If the amount of boron is less than 0.05% by mass, there is a high possibility that the desired highly conductive graphite powder will not be obtained. On the other hand, even if the amount of boron exceeds 5% by mass, the degree of contribution to the improvement of the conductivity of the carbon material tends to decrease. The method for measuring the amount of boron contained in the carbonaceous material is not particularly limited, and any measurement method can be used. In the present invention, a value measured by induction plasma emission spectrometry (hereinafter abbreviated as “ICP”) or induction plasma emission spectrometry / mass spectrometry (hereinafter abbreviated as “ICP-MS”) is used. Specifically, sulfuric acid and nitric acid are added to the sample, decomposed by microwave heating (230 ° C.) (Digester method), and further decomposed by adding perchloric acid (HClO ₄ ) and diluted with water. Is applied to an ICP emission spectrometer to measure the amount of boron.

(Method of containing boron)
As a method for containing boron, natural graphite, artificial graphite, expanded graphite, carbon black, carbon fiber, vapor-grown carbon fiber, carbon nanotube, or the like, or a mixture of at least one of them as a boron source, B alone , B ₄ C, BN, B ₂ 0 ₃ , H ₃ B0 _3, etc. are added, mixed well, and graphitized at about 2300 to 3200 ° C. to contain boron in the carbonaceous material. be able to. If the boron compound is not uniformly mixed, not only the graphite powder becomes non-uniform, but also the possibility of sintering during graphitization tends to increase. In order to uniformly mix the boron compound, it is preferable that these boron sources have a particle size of about 50 μm or less, preferably about 20 μm or less, and are mixed with a powder such as coke.

  When boron is not added, graphitization decreases the degree of graphitization (crystallinity), increases the lattice spacing, and increases the difficulty of obtaining highly conductive graphite powder. Further, as long as boron and / or boron compounds are mixed in graphite, the form of boron content is not particularly limited. Those substituted with atoms 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.

(Carbon black)
Carbon black, which is an example of the carbonaceous material described above, includes furnaces obtained by incomplete combustion of natural gas, etc., ketjen black obtained by thermal decomposition of acetylene, acetylene black, hydrocarbon oil and natural gas. Examples thereof include thermal carbon obtained by pyrolysis of carbon and natural gas.

(Carbon fiber)
Examples of the carbon fiber include pitch systems made from heavy oil, by-product oil, coal tar, and the like, and PAN systems made from polyacrylonitrile.

(Amorphous carbon)
In order to obtain the above-mentioned amorphous carbon, there is a method in which a phenol resin is cured and baked and pulverized to obtain a powder, or a method in which a phenol resin is cured in the form of a spherical, irregularly shaped powder and baked. is there. In order to obtain amorphous carbon having high conductivity, it is suitable to perform heat treatment at 2000 ° C. or higher.

(Expanded graphite electrode)
The above expanded graphite powder is, for example, a strong oxidizing solution of graphite having a highly developed crystal structure such as natural graphite and pyrolytic graphite, a mixture of concentrated sulfuric acid and nitric acid, and a mixture of concentrated sulfuric acid and hydrogen peroxide. Immersion treatment to form a graphite intercalation compound, which is washed with water and then rapidly heated to pulverize the powder obtained by expanding the C-axis direction of the graphite crystal and once rolled into a sheet Powder.

(Artificial graphite)
In order to obtain the above-mentioned artificial graphite, usually coke is first produced. Coke raw material 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 the coke and then graphitizing, or by pulverizing the coke itself and then pulverizing, or by adding a binder to the coke and molding and firing the product (coke and this calcined product). There is a method of pulverizing a product after combining it with a graphitization process. Since it is preferable that the raw material coke is not developed as much as possible, a heat-treated material at 2000 ° C. or lower, preferably 1200 ° C. or lower is suitable.

  As the graphitization method, a method using an Atchison furnace in which powder is put in a graphite crucible and directly energized, a method of heating powder with a graphite heating element, or the like can be used.

  For crushing coke, artificial graphite, natural graphite, 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) Mold mills, annular mills) and the like can be used. Further, a screen mill, a turbo mill, a supermicron mill, and a jet mill, which are fine pulverizers, can be used by selecting conditions. Crush, natural graphite, and the like are pulverized using these pulverizers, and the selection of pulverization conditions at that time, and classification of the powder as necessary, control the average particle size and particle size distribution.

  As a method for classifying coke powder, artificial graphite powder, natural graphite powder, etc., any method can be used as long as separation is possible. For example, a sieving method or a forced vortex type centrifugal classifier (micron separator, turboplex, turboclassic) Airflow classifiers such as fire and super separators and inertia classifiers (improved virtual impactor and elbow jet) can be used. A wet sedimentation method or a centrifugal classification method can also be used.

(Gas-phase carbon fiber / carbon nanotube)
The component B of the present invention preferably contains 0.1 to 50% by mass of vapor grown carbon fiber and / or carbon nanotube. More preferably, it is 0.1-45 mass%, More preferably, it is 0.2-40 mass%. If it is less than 0.1% by mass, there is no effect in improving the conductivity. Moreover, when it exceeds 50 mass%, there exists a tendency for a moldability to worsen.

  Further, the vapor grown carbon fiber or carbon nanotube preferably contains 0.05 to 5% by mass of boron. More preferably, it is 0.06-4 mass%, More preferably, it is 0.06-3 mass%. If it is less than 0.05% by mass, the effect of improving the conductivity by adding boron is small. Moreover, when it exceeds 5 mass%, the amount of impurities tends to increase, leading to a decrease in other physical properties.

  The vapor grown carbon fiber is obtained by, for example, subjecting an organic compound such as benzene, toluene or natural gas as a raw material to a thermal decomposition reaction at 800 ° C. to 1300 ° C. with hydrogen gas in the presence of a transition metal catalyst such as ferrocene. The fiber diameter is about 0.5 μm to 10 μm. Furthermore, it is preferable to graphitize at about 2300 ° C. to 3200 ° C. thereafter. More preferably, it is graphitized at about 2300 ° C. to 3200 ° C. with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum and silicon.

  With carbon nanotubes, in recent years, not only its mechanical strength, but also field emission function and hydrogen storage function have attracted industrial attention, and further attention has been focused on 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, etc., and the fiber diameter is about 0.5 nm to 100 nm. belongs to. 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 single-walled and multi-walled carbon nanotubes can be used. However, it is preferable to use single-walled carbon nanotubes because a composition having higher conductivity and mechanical strength tends to be obtained.

  Carbon nanotubes are produced, for example, by the arc discharge method, laser evaporation method, thermal decomposition method, etc. described in Saito / Panto “Basics of Carbon Nanotubes” (P23-P57, Corona Publishing, 1998) In order to enhance, it is obtained by purification by hydrothermal method, centrifugal separation method, ultrafiltration method, oxidation method or the like. More preferably, high temperature treatment is performed in an inert gas atmosphere at about 2300 ° C. to 3200 ° C. to remove impurities. More preferably, high temperature treatment is performed at about 2300 ° C. to 3200 ° C. in an inert gas atmosphere together with a graphitization catalyst such as boron, boron carbide, beryllium, aluminum and silicon.

(composition)
The composition of the polymer component and the B component in the present invention is preferably such that the polymer component is 40 to 2% by mass and the B component is 60 to 98% by mass based on (polymer component + B component) (100% by mass). More preferably, the polymer component is 30 to 5% by mass and the B component is 70 to 95% by mass. More preferably, the polymer component is 25 to 5% by mass and the B component is 75 to 95% by mass. If the polymer component is less than 2% by mass, the moldability tends to deteriorate. On the other hand, if the polymer component exceeds 40% by mass, the volume resistivity tends to be 1 Ωcm or more.

(Additive)
Furthermore, the crystalline thermoplastic resin composite material of the present invention may further include glass fiber, whisker, for the purpose of improving hardness, strength, conductivity, moldability, durability, weather resistance, water resistance, etc., if necessary. Additives such as metal oxides, organic fibers, UV stabilizers, antioxidants, mold release agents, lubricants, water repellents, thickeners, low shrinkage agents, hydrophilicity imparting agents and the like can be added.

(Production method)
The method for producing the crystalline thermoplastic resin composite material in the present invention is not particularly limited. For example, the above-described components are used in the resin field such as a roll, an extruder, a kneader, a Banbury mixer, a Henschel mixer (registered trademark), and a planetary mixer. It is preferable to use a mixer and a kneader that are generally used and to mix as uniformly as possible.

  Moreover, although the above-mentioned polymer component is manufactured beforehand, the method of mixing with B component, the method of kneading each component of a polymer component in presence of B component, etc. are mentioned, However It is not limited.

  The crystalline thermoplastic resin composite material in the present invention can be pulverized or granulated as necessary for the purpose of facilitating material supply to a molding machine or a mold after kneading or mixing. For pulverization, a homogenizer, a Willet pulverizer, a high-speed rotary pulverizer (hammer mill, pin mill, cage mill, blender) or the like can be used, and it is preferable to pulverize while cooling to prevent aggregation of materials. For granulation, a method of pelletizing using an extruder, a ruder, a kneader or the like, or a bread type granulator or the like can be used.

(Method for producing conductive structure)
The detail of the manufacturing method of the electroconductive structure in this invention is shown below.

(Manufacturing method 1)
The mold cavity surface temperature is kept at _Tm or higher until molding of the composite material melted in the mold is completed by molding of the conductive structure composed of the above crystalline thermoplastic resin composite material. after being shaped, at (T C _-20) ℃ or higher, and at (T C ₊₂₀₎ ℃ below the mold cavity surface temperature, the allowed composite solidified, removed from the mold. Incidentally, T _m is the crystalline melting temperature, T _C is the crystallization temperature, the measurement method will be described later. Here, mold molding is a general term for a method of molding a molded product using a mold or a metal frame, and examples thereof include injection molding, injection compression molding, compression molding, stamping molding, and the like. Of these, compression molding and stamping are preferred because a conductive structure with high dimensional accuracy can be obtained. Also, injection molding and injection compression molding are preferred because the molding cycle time is short. Furthermore, injection compression molding is particularly preferred because the conductivity is not lowered by the skin layer on the surface of the molded product, which is unavoidable by injection molding. In order to remove voids in the structure during the molding process, the mold can be formed in a vacuum state in the mold or the entire mold.

  Here, shaping means applying pressure to the melted composite material to transfer the shape of the mold cavity to the composite material. Specifically, in the case of compression molding, stamping molding, injection compression molding, The operation until the compression of the mold is completed is shown. In the case of injection molding, the operation until the injection is completed is shown. Solidification means that the composite material is hardened to such an extent that the structure is not damaged or deformed when the structure is taken out of the mold. After the structure is taken out of the mold, the structure may be deformed by post-crystallization of the composite material. In such a case, the structure needs to be corrected so as not to be deformed.

Molding conditions to be precisely controlled which are particularly important in the manufacturing method 1 are a mold temperature and a cavity surface temperature of the mold. Until the composite material as described above is shaped into a conductive structure in a mold surface temperature is maintained above T _m, after shaping complete, (T C _-20) ℃ or higher, and (T C _-20) ℃ so as to cool and solidifying the composite material at the surface temperature of below, must be at the mold temperature and cavity surface temperature. It is particularly preferable to maintain the cavity surface temperature at (T _m +5) ° C. or higher during shaping because a structure with higher dimensional accuracy can be formed. However, if the saddle shape is completed at the surface temperature that is too high, it takes time for cooling, and the molding cycle time becomes long, so that an efficient conductive structure cannot be manufactured. Therefore, the cavity surface temperature at the completion of shaping is preferably (T _m +10) ° C. or lower.

Further, after the shaping completion, mold temperature and cavity surface temperature when solidified cooling the composite, at (T C _-20) ℃ or higher and (T C ₊₂₀₎ ° C. or less of the temperature is required, it is preferably required to be a by _(T C -10) above, and _(T C +15) ℃ or lower. By cooling the composite material from the molten state at the mold temperature and the cavity surface temperature, the crystallization of the composite material is greatly promoted, and the volume specific resistance and penetration resistance of the conductive structure are greatly reduced. Furthermore, because the effect of the present invention is great, the mold temperature and the cavity surface temperature when cooling and solidifying the composite material should be not lower than T _{C and not} higher than (T _C +15) ° C. Is particularly preferred. In the case of injection molding or injection compression molding, a holding pressure may be applied in the mold cavity after the composite material is shaped in order to prevent warping or sinking of the conductive structure.

  As described above, the method of controlling the mold temperature and cavity surface temperature is to circulate water or oil in the mold, or to control the mold temperature and cavity surface temperature precisely with a mold heater. The use of a mold is mentioned. In addition, the mold temperature is set to the temperature at which the composite material is cooled, and immediately before molding, the cavity surface temperature and the composite material temperature are heated by induction heating, infrared rays, ultrasonic waves, electric fields or magnetic fields, and then molded. A method can also be used. A heat insulating mold having a heat insulating layer on the cavity surface can also be used. In order to reduce the molding cost, a plurality of conductive structures may be manufactured at a time using a mold having a plurality of cavities.

  As a method of measuring the mold temperature and the cavity surface temperature, a commercially available mold thermometer can be used, or a temperature sensor is installed in the mold, on the surface of the cavity, or in the vicinity of the surface. You can also.

Crystalline melting temperature T _m of a crystalline thermoplastic resin composite material may be measured using a differential scanning calorimeter (hereinafter abbreviated as DSC.) Is measured as follows using. Using a crystalline thermoplastic resin composite material as a sample, about 10 mg of a sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on a DSC together with an empty aluminum pan without a sample. The temperature at which the sample completely melts in both aluminum pans (the exact melting temperature is not known at this time, but the temperature is 60 ° C. or more higher than the crystal melting temperature of the crystalline thermoplastic resin contained in the sample). Hold for minutes and then cool from that temperature to 25 ° C. at a cooling rate of 20 ° C./min. Thereafter, the sample is held at 25 ° C. for 10 minutes, and then heated again at a rate of temperature increase of 20 ° C./min to a temperature at which the sample is completely melted. The temperature of the top of an endothermic peak due to melting of crystals occurred when the the T _m. If the endothermic peak there are multiple, the apex of the best high temperature endothermic peak with T _m.

Further, crystallization temperature T _C of the crystalline thermoplastic resin composite material is measured as follows using a DSC. Using a crystalline thermoplastic resin composite material as a sample, about 10 mg of a sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on a DSC together with an empty aluminum pan without a sample. Both aluminum pans are held at a temperature 60 ° C. or higher above _Tm for 10 minutes, and then cooled from that temperature to 25 ° C. at a cooling rate of 20 ° C./min. The temperature at the top of the exothermic peak due to crystallization that occurred at this time is T _C. If the exothermic peak there are multiple, an exothermic peak due to crystalline thermoplastic resin having the largest volume fraction in the composite material and T _C.

(Manufacturing method 2)
In molding a conductive structure made of the crystalline thermoplastic resin composite material, after the composite material melted in the mold is shaped, (T C ₊₂₀₎ from ℃ (T C _-20) ℃ The composite material is cooled and solidified at a cooling rate of 30 ° C./min or less in the temperature range up to the following, and then the conductive structure is taken out from the mold. The conditions under which the composite material is shaped in the mold are the same as in manufacturing method 1 described above. At the time of cooling after molding, the temperature range is cooled at a cooling rate of 30 ° C./min or less, preferably 20 ° C./min. Thereby, the crystallization of the composite material is greatly promoted, and the volume specific resistance and penetration resistance of the conductive structure are greatly reduced. Furthermore, it is particularly preferable to cool the temperature range at a cooling rate of 10 ° C./min because the effect of the present invention is great.

(Manufacturing method 3)
In the production of a conductive structure made of the above crystalline thermoplastic resin composite material, after molding the conductive structure, after taking out from the mold, it is _Tm or less and ( _Tm- 30) ° C or more By conducting a heat treatment (annealing), a conductive structure having excellent conductivity is manufactured. In this manufacturing method 3, as long as heat treatment is performed after molding, there is no limitation on molding of the conductive structure. However, if crystallization is greatly promoted during molding, the effect of promoting crystallization by heat treatment after molding will not be significant. Therefore, in order to increase the heat treatment effect after molding, it is preferable not to promote crystallization during molding. The temperature for the heat treatment is _Tm or lower, and is ( _Tm- 30) or higher, preferably _Tm or lower, and ( _Tm- 20) ° C or higher. Thereby, the crystallization of the composite material is greatly promoted, and the volume specific resistance and penetration resistance of the conductive structure are greatly reduced. Furthermore, it is particularly preferable to perform the heat treatment at _Tm or less and ( _Tm- 20) ° C or more because the effect of the present invention is great.

(Prevents deformation of conductive structure)
In order to prevent deformation when the composite material is solidified and cooled in the production methods 1 and 2 and / or when the conductive structure is heat-treated in the production method 3, the conductive structure is molded as a mold. It is preferable that the pressure is applied by pressing, or the pressure is applied by sandwiching the conductive structure between correction plates that prevent deformation of the conductive structure. This is because crystallization of the composite material is greatly promoted by cooling or heat treatment, so that the conductive structure is highly likely to be deformed.

  Below, the specific example of the said manufacturing method is introduced. However, the present invention is not limited to the following examples.

(Compression molding method)
An example of the compression molding method of the conductive structure in the present invention is shown below. A temperature profile device is mounted on the compression mold so that the mold cavity surface temperature can be precisely and freely varied. The mold temperature (molding temperature) is not particularly limited as long as it is a temperature at which the crystalline thermoplastic resin composite material in the present invention melts and the composite material does not thermally decompose, but at (T _m +50) ° C. or higher. It is particularly preferred. After setting the temperature, the powder or lump of the composite material is placed on the mold cavity. At this time, in order to obtain a conductive structure having a good thickness accuracy, a preform having a predetermined thickness and size, which has been molded in advance using an extruder, a roll, a calendar, or the like, is placed on the mold cavity. It may be arranged. In order to form a conductive structure with higher thickness accuracy, it is preferable to form a preform with an extruder and then roll it with a roll or calender. In order to eliminate voids and air in the preform, it is preferable to perform extrusion molding in a vacuum state. Thereafter, the mold is closed and preheating is performed for a time sufficient for the composite material to melt, followed by pressurization and compression molding. At this time, a plurality of conductive structures may be formed at a time using a plurality of molds in a mold having a plurality of mold cavities or a multistage compression molding machine. In order to obtain a good product substantially free of defects, it is preferable to evacuate the cavity. After melt molding from the molding temperature (T C _-20) cavity surfaces at 10 ° C. / min cooling rate until ° C. and cooled, electrically conductive structure of the present invention by taking out the conductive structure from the mold can get.

(Injection compression molding method)
The example of the injection compression molding method of the electroconductive structure in this invention is shown below. The set temperature of the plasticizing cylinder is not particularly limited as long as the crystalline thermoplastic resin composite material of the present invention is melted and the composite material does not undergo thermal decomposition, but from 30 ° C. above T _m. A temperature as high as about 60 ° C. is preferred. In addition, a temperature profile device capable of precisely and freely changing the mold cavity surface temperature is attached to the mold, and the mold cavity temperature and the mold surface temperature are set to (T _m +5) ° C. After confirming that the cylinder temperature and the mold temperature are constant, pellets made of the crystalline thermoplastic resin composite material of the present invention are put into a hopper of an injection compression molding machine. There are no particular restrictions on injection compression molding conditions such as weighing, injection speed, injection pressure, secondary pressure, mold clamping force, cooling time, etc., and conditions under which a conductive structure can be suitably obtained are set. The molten composite material is injected and filled into a mold cavity and compressed. Thereafter, the mold cavity surface temperature to (T C ₊₁₀₎ ℃, after solidifying the cooled the composite material at a 20 ° C. / min cooling rate, taken out conductive structure from the mold. After the conductive structure is taken out, in order to further cool, the structure may be sandwiched between a correction plate for preventing deformation of the structure and then cooled by pressing.

  In addition, when the conductive structure of the present invention is injection-molded or injection-compression-molded, in addition to a mold provided with a temperature profile device capable of precisely and freely varying the mold temperature, the wall of the mold cavity is also provided. You may use the heat insulation metal mold | die which provided the heat insulation layer. Further, the molding may be started after the mold cavity surface is temporarily heated by induction heating, infrared rays, ultrasonic waves or the like before the molding is started. Furthermore, a molding method is also effective in which after the mold cavity is filled with the composite material, an electric field or a magnetic field is applied to the mold cavity to control the solidification of the composite material. Further, in order to improve the moldability, carbon dioxide gas can be injected from the middle of the molding machine cylinder, dissolved in the material, and molded in a supercritical state.

(Conductive structure)
In this invention, it is preferable that the electroconductive structure which consists of a crystalline thermoplastic resin composite material satisfy | fills the relationship represented by X> = 0.8 * Y (Formula 1).
In Equation 1, about 10 mg of a part of the conductive structure is used as a sample. Using a differential scanning calorimeter, X is raised from 25 ° C. to a temperature 60 ° C. higher than _Tm at a temperature rising rate of 20 ° C./min. This represents a value obtained by dividing the heat of fusion of the crystal observed when warmed by the mass of the sample, and its unit is J / g. Y is about 10 mg of a crystalline thermoplastic resin composite material as a sample, and is held at a temperature 60 ° C. or higher than _Tm for 10 minutes using a differential scanning calorimeter, and then at a cooling rate of 5 ° C./min. After cooling to 25 ° C. and holding at 25 ° C. for 10 minutes, the heat of melting of the crystal observed when the temperature is further raised to a temperature 60 ° C. higher than _{Tm at a} rate of temperature increase of 20 ° C./min is the mass of the sample. The unit is J / g. The value of _Tm is obtained in advance by DSC measurement of a crystalline thermoplastic resin composite material.

  In Formula 1, Y is a value representative of the heat of fusion when the crystallinity of the crystalline thermoplastic resin composite material has risen to the limit (of course, annealing is performed for a long time (several hours) near the crystallization temperature). For example, the degree of crystallinity slightly increases and the heat of fusion increases from the value measured under the above conditions, but the measurement takes too much time.) Therefore, Formula 1 indicates that the crystallinity of the conductive structure of the present invention is 80% or more of the crystallinity limit value of the composite material. A conductive structure that satisfies Formula 1 is excellent in conductivity, and has high bending strength and bending elastic modulus.

(Separator)
The method for producing a fuel cell separator using the crystalline thermoplastic resin composite material of the present invention is not particularly limited. Specific examples of this production method include, but are not limited to, compression molding, transfer molding, injection molding, casting, and injection compression molding. More preferably, the molding is performed in the mold or in the whole mold at the time of molding.

  In order to increase the molding cycle speed in compression molding, it is preferable to use a multi-cavity mold. More preferably, when a multi-stage press (lamination press) method is used, a large number of products can be formed with a small output. In order to improve the surface accuracy with a flat product, it is preferable to form the sheet once and then compress it.

  In the injection molding, for the purpose of further improving the moldability, carbon dioxide gas can be injected from the middle of the molding machine cylinder, dissolved in the material, and molded in a supercritical state. In order to increase the surface accuracy of the product, it is preferable to use an injection compression method. As the injection compression method, a method of injecting and closing with the mold open, a method of injecting while closing the mold, and a method of applying the mold clamping force after injecting with the mold clamping force of the closed mold being zero Etc. are used.

(Mold)
In the present invention, the mold to be used at the time of molding is not particularly limited as long as the above temperature control is possible. For example, when the material is rapidly solidified and fluidity is poor, it is preferable to use a heat insulating mold in which a heat insulating layer is charged in the cavity. Further, a mold in which a temperature profile system capable of raising and lowering the mold temperature during molding is more preferable. Examples of temperature profile methods include induction heating and refrigerant (air, water, oil, etc.) switching systems, and heat medium (hot water, heating oil, etc.) and refrigerant switching systems. is not.

As for the mold temperature, it is important to select and search for the optimum temperature according to the kind of crystalline thermoplastic resin composite material and T _m and T _C. For example, it can be appropriately determined within a temperature range of 90 ° C. to 200 ° C. and a range of 10 seconds to 1200 seconds. When the molded product is taken out at a high temperature, it may be cooled, but the method is not limited. For example, for the purpose of suppressing warpage, a method of cooling a molded product by sandwiching it with a cooling plate, a method of cooling the entire mold, or the like can be mentioned.

  The separator for fuel cells in which the flow path for flowing gas is formed on both sides or one side of the present invention can be obtained by molding the conductive resin composition of the present invention by the molding method described above. The flow path for flowing the gas may be formed by machining the molded body of the conductive resin composition. Alternatively, the gas flow path may be formed by compression molding, stamp molding, or the like using a mold having an inverted shape of the gas flow path.

  The channel cross-sectional shape and the channel shape of the separator of the present invention are not particularly limited. For example, the channel cross-sectional shape includes a rectangle, a trapezoid, a triangle, a semicircle, and the like. Examples of the channel shape include a straight type and a meandering type. The width of the channel is preferably 0.1 to 2 mm and the depth is 0.1 to 1.5 mm.

  The thinnest part of the separator of the present invention is preferably 1 mm or less. More preferably, it is 0.8 mm. If the thickness is 1 mm or more, the separator becomes thick, so that the voltage drop of the cell due to the resistance of the separator becomes large, which is not preferable.

  In the fuel cell separator of the present invention, it is preferable to form a through hole serving as a manifold for flowing gas or water. Examples of the method for forming the through hole include, but are not limited to, a method of forming a through hole at the time of molding, a method of forming by cutting after molding, and the like.

(Use of conductive structure)
Since the conductive structure of the present invention is excellent in conductivity and has high bending strength and bending elastic modulus, it is optimal as a structure requiring high conductivity and high mechanical properties like a fuel cell separator.
Furthermore, the conductive structure of the present invention can reproduce the conductivity of graphite as much as possible, and an extremely high performance can be obtained in terms of excellent molding accuracy and the like. Therefore, it is useful for each application such as various parts of the electronics field, electrical machinery, machinery, vehicles, etc., and in particular, a current collector for capacitors or various batteries, an electromagnetic shielding material, an electrode, a heat sink, a heat dissipation component, an electronic component, Examples of suitable materials for semiconductor parts, bearings, PTC elements, brushes, and fuel cell separators.

Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples. First, a method for measuring physical properties of a molded body is shown below. Volume resistivity is JIS
In accordance with K7194, measurement was performed by the four-probe method.

The penetration resistance is measured by the four-terminal method shown in FIG. Specifically, four test pieces (50 mm x 50 mm x 2 mm) are stacked, sandwiched between two gold-plated brass plates, and uniformly pressed at 2 MPa, and a constant current of 1 A is passed between the gold-plated brass plates in the penetration direction. Then, the resistance (R ₁ ) is calculated by measuring the voltage. Similarly, the resistance (R ₂ ) is calculated by stacking two test pieces and sandwiching them between gold-plated brass plates and performing the same measurement. Furthermore, as shown in Equation 2 shown in the next section, the difference between the resistance (R ₁ ) and the resistance (R ₂ ) is taken, multiplied by the contact area (S), and divided by the thickness (t) of two test pieces. Calculate the penetration resistance.

[Formula 2]
Rt = (R ₁ −R ₂ ) × S / t (2)
Rt: penetration resistance (Ωcm), S: contact area (cm ² )
R ₁ : Resistance calculated from measurement 1 (Ω)
R ₂ : Resistance calculated from measurement 2 (Ω)
t: Thickness (cm) of two test pieces

  The bending strength, bending elastic modulus and bending strain were measured using an autograph (AG-10kNI) manufactured by Shimadzu Corporation. A test piece (80 mm × 10 mm × 4 mm) was measured by a JIS K6911 method by a three-point bending strength measurement method under a span interval of 64 mm and a bending speed of 1 mm / min.

The heat of fusion X of the crystals in the conductive structure was measured by the following procedure using DSC (DSC7 model, manufactured by Perkin Elmer). Using a part of the conductive structure as a sample, about 10 mg of the sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on the DSC together with an empty aluminum pan without a sample. Represents the value obtained by dividing the heat of fusion of crystals observed when the temperature of both aluminum pans is raised from 25 ° C. to 60 ° C. higher than T _m at a rate of temperature increase of 20 ° C./min divided by the mass of the sample. Is J / g.

A value Y representing the limit of the heat of fusion of crystals in the crystalline thermoplastic resin composite material was measured by the following procedure using DSC. Using a crystalline thermoplastic resin composite material as a sample, about 10 mg of a sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on a DSC together with an empty aluminum pan without a sample. Both aluminum pans were held at a temperature 60 ° C. or higher than _Tm for 10 minutes, then cooled to 25 ° C. at a cooling rate of 5 ° C./minute, held at 25 ° C. for 10 minutes, and then further increased at 20 ° C./minute. This represents a value obtained by dividing the heat of fusion of the crystal observed when the temperature is raised to a temperature 60 ° C. higher than _Tm by the temperature rate, divided by the mass of the sample, and the unit is J / g.

Melting temperature T _m of a crystalline thermoplastic resin composite material is measured as follows using a DSC. Using a crystalline thermoplastic resin composite material as a sample, about 10 mg of a sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on a DSC together with an empty aluminum pan without a sample. The temperature at which the sample completely melts in both aluminum pans (the exact melting temperature is not known at this time, but the temperature is 60 ° C. or more higher than the crystal melting temperature of the crystalline thermoplastic resin contained in the sample). Hold for minutes and then cool from that temperature to 25 ° C. at a cooling rate of 20 ° C./min. Thereafter, the sample is held again at 25 ° C. for 10 minutes, and heated again at a rate of temperature increase of 20 ° C./min until the sample completely melts. The temperature of the top of an endothermic peak due to melting of crystals occurred when the the T _m. If the endothermic peak there are multiple, the apex of the best high temperature endothermic peak with T _m.

Further, the crystallization temperature TC of the crystalline thermoplastic resin composite material is measured as follows using DSC. Using a crystalline thermoplastic resin composite material as a sample, about 10 mg of a sample is accurately weighed and placed in an aluminum pan, and the aluminum pan is set on a DSC together with an empty aluminum pan without a sample. Both aluminum pans are held at a temperature 60 ° C. or higher above _Tm for 10 minutes, and then cooled from that temperature to 25 ° C. at a cooling rate of 20 ° C./min. The temperature at the top of the exothermic peak due to crystallization generated at this time is defined as TC. When there are a plurality of exothermic peaks, the exothermic peak due to the crystalline thermoplastic resin having the largest volume fraction in the composite material is defined as TC.

The materials used are shown below.
Polymer components: those listed in Table 1 were used.
Polypropylene: Sun Allomer PW201N Styrene Ethylene Butylene Styrene Block Copolymer (SEBS): Clayton G1652 Hydrogenated Styrene Butadiene Rubber (H-SBR): Dynalon manufactured by JSR Corporation 1320P was used.
Polyvinylidene fluoride (PVDF): Neoflon VW-410 manufactured by Daikin Industries, Ltd. Soft acrylic resin: Parapet SA-FW001 manufactured by Kuraray Co., Ltd.

B component: Conductive filler <B1>: Boron-containing graphite fine powder MC coke made by MC Carbon Co., which is non-needle coke, with a pulverizer (manufactured by Hosokawa Micron Co., Ltd.) with a size of 2 mm to 3 mm or less Coarsely pulverized. 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.). Boron carbide (B ₄ C) 0.6 kg was added to 14.4 kg of a part of this finely pulverized product, and mixed for 5 minutes at 800 rpm with a Henschel mixer (registered trademark). This was sealed in a graphite crucible with a lid having an inner diameter of 40 cm and a volume of 40 liters, placed in a graphitization furnace using a graphite heater, and graphitized at a temperature of 2900 ° C. in an argon gas atmosphere. After standing to cool, the powder was taken out to obtain 14 kg of powder. The obtained graphite fine powder had an average particle size of 20.5 μm and a B content of 1.9% by mass.

<B2>: A mixture of vapor grown carbon fiber (hereinafter abbreviated as “VGCF”; Showa Denko, registered trademark) and B1 (graphite fine powder). B1 component 95 mass% and VGCF 5 mass% were mixed with the Henschel mixer (trademark). The average particle diameter of the obtained carbon material mixture was 12.4 μm and the B content was 1.3% by mass.

  As the vapor grown carbon fiber, VGCF-G (fiber diameter 0.1 to 0.3 μm, fiber length 10 to 50 μm) manufactured by Showa Denko Co., Ltd. was used.

<B3>: A mixture of carbon nanotubes (hereinafter abbreviated as “CNT”) and B1 (graphite fine powder). B1 component 95% by mass and CNT 5% by mass were mixed with a Henschel mixer (registered trademark). The obtained carbon material mixture had an average particle size of 9.2 μm and a B content of 1.2% by mass. Carbon nanotubes were obtained by the following method.

  A graphite rod having a diameter of 6 mm and a length of 50 mm is drilled with a hole having a diameter of 3 mm and a depth of 30 mm along the central axis from the tip, and a rhodium (Rh): platinum (Pt): graphite (C) mass ratio is 1 in this hole. It was packed as a 1: 1 mixed powder to prepare an anode. On the other hand, a cathode having a diameter of 13 mm and a length of 30 mm made of graphite having a purity of 99.98% by mass 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% by volume, 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 collected 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.

  The types and amount ratios of the component A and component B used in the following examples and comparative examples are summarized in Table 2 below. Table 2 summarizes the results of DSC measurement of the crystallization temperature, crystal melting temperature, and heat of fusion Y of each composite material. The value of 0.8 × Y is also shown in Table 2.

(Example 1 to Example 5)
The raw materials having the compositions shown in Tables 1 and 2 above are kneaded for 7 minutes at a temperature of 200 ° C. and 45 rpm using a lab plast mill (manufactured by Toyo Seiki Seisakusho, Model 100C100), and a crystalline thermoplastic resin composite material Got. The composite material is put into a mold capable of forming a 100 mm × 100 mm flat plate (thickness varies depending on physical property test items), and preheated at a temperature of 230 ° C. using a 50-t compression molding machine A (NIPPO ENGINEERING E-3013). After 3 minutes, pressure heating was performed at a pressure of 15 MPa for 3 minutes. Thereafter, the mold was taken out from the compression molding machine A while it was hot, and the mold was immediately pressed at a pressure of 15 MPa using a 50t compression molding machine B (NIPPO ENGINEERING E-3013) set to the heat treatment temperature shown in Table 3. Pressurized for 10 minutes. Then, it was made to cool for 2 minutes on the conditions of temperature 25 degreeC and pressure 15MPa using a cooling press, and the electroconductive structure was obtained.

(Comparative Examples 1 to 5)
The crystalline thermoplastic resin composite materials having the compositions shown in Tables 1 and 2 were obtained in the same procedure as in Examples 1 to 5. The kneaded material is put into a mold capable of forming a flat plate of 100 mm × 100 mm (thickness varies depending on physical property test items), using a 50-t compression molding machine A, temperature 230 ° C., preheating 3 minutes, and pressure 15 MPa for 3 minutes Pressurized and heated. Then, it was made to cool for 2 minutes on the conditions of temperature 25 degreeC and pressure 15MPa using a cooling press, and the electroconductive structure was obtained. The results obtained by the above Examples and Comparative Examples are summarized in Table 3 below.

  In any of the examples, the above formula 1 is satisfied, while in any of the comparative examples, the above formula 1 is not satisfied. Comparing the examples in which the heat treatment was performed using the same composite material and the comparative example in which the heat treatment was not performed, in any of the composite materials, the volume specific resistance and the penetration resistance were smaller, and the bending strength and the flexural modulus were It is getting bigger. On the other hand, the bending strain is reduced, but it is much larger than the target value (1% or more) required for the fuel cell separator.

(Example 6 to Example 9, Comparative Example 6)
A conductive structure was obtained in the same procedure as in Examples 1 to 5 except that the composite material 5 was used. The results obtained by the above Examples and Comparative Examples are summarized in Table 4 below.

(Comparative Example 7)
A conductive structure was obtained in the same procedure as Comparative Examples 1 to 5 except that the composite material 5 was used and the heat treatment temperature was changed. The results obtained by the above Examples and Comparative Examples are summarized in Table 4 below.

  In any of the examples, the above formula 1 is satisfied, while in any of the comparative examples, the above formula 1 is not satisfied. Example 6 in which heat treatment was performed at a temperature of not less than 149.3 ° C., which was 20 ° C. higher than the crystallization temperature of the composite material 5 even when the heat treatment was performed using the same composite material 5. Comparing Comparative Example 6 in which heat treatment was performed at 150 ° C. at ˜9 to 149.3 ° C. or higher, the specific volume resistance and penetration resistance were smaller in the example. Further, even when Examples 6 to 9 are compared with Comparative Example 7 where heat treatment is not performed, the volume resistivity and the penetration resistance are smaller in the example.

( Reference Example 10)
The composite material 5 is put into a mold capable of forming a flat plate of 100 mm × 100 mm (thickness varies depending on physical property test items), using a 50 t compression molding machine A, temperature 230 ° C., preheating 3 minutes, and pressure 15 MPa for 3 minutes. The mixture was heated under pressure, and then cooled for 2 minutes under the conditions of a temperature of 25 ° C. and a pressure of 15 MPa using a cooling press to obtain a conductive structure. The conductive structure was further inserted into a mold, and the mold was heated and pressurized at a pressure of 15 MPa for 120 minutes using a 50 t compression molding machine B set at 155 ° C. Then, it was made to cool for 2 minutes on the conditions of temperature 25 degreeC and pressure 15MPa using a cooling press, and the electroconductive structure was obtained. The results obtained by Reference Example 10 are summarized in Table 5 below.

( Reference Example 11)
Oil can be circulated through the hot plate of the 50t compression molding machine B. The temperature of the hot plate can be precisely controlled by circulating the oil whose temperature is precisely controlled from the oil temperature controller to the hot plate. The composite material 5 is put into a mold capable of forming a flat plate of 100 mm × 100 mm (thickness varies depending on physical property test items), using a 50 t compression molding machine B, after a temperature of 230 ° C., preheating for 3 minutes, and a pressure of 15 MPa for 3 minutes. After pressurizing and heating, the mold is cooled at a pressure of 15 MPa until the temperature of the hot plate reaches 100 ° C. at a cooling rate of 5 ° C./min. Then, it was made to cool for 2 minutes on the conditions of temperature 25 degreeC and pressure 15MPa using a cooling press, and the electroconductive structure was obtained. The results obtained in Reference Example 11 are summarized in Table 5 below.

In any of Reference Examples 10 and 11, the above formula 1 is satisfied, while in the comparative example 7, the above formula 1 is not satisfied. Reference Example 10 in which the annealed for two hours at 155 ° C. after molding, as compared to Comparative Example 7 which did not perform the heat treatment as in Reference Example 11 was gradually cooled at a cooling rate of 5 ° C. / min after shaping found the following examples Volume resistivity and penetration resistance are reduced.

(Example 12, Comparative Example 8)
Using composite material 1, 350t injection mold that can form a flat plate with 6 holes, 280 x 200 x 1.5 mm, groove width 1 mm pitch, groove depth 0.5 mm on both sides The conductive structure was injection compression molded by being attached to a compression molding machine. The cylinder temperature was set at 280 ° C. and the mold temperature at 140 ° C. Immediately before the start of molding, the cavity surface is heated from the outside to the cavity surface temperature shown in Table 6 by injection compression molding at an injection pressure of 100 MPa, a compression force of 50 t, and a cooling time of 150 seconds, and a fuel cell separator A flat plate was obtained. The volume resistivity of the flat plate and the thickness at the center of the flat plate were measured, and the results are shown in Table 6.

  As shown in Table 6, in Example 12 in which the mold temperature was heated to the crystal melting temperature of the composite material 1 or more, a plate having the shape of the mold cavity was obtained, but only at a temperature lower than the crystal melting temperature. In Comparative Example 8 which was not heated, only a flat plate thicker than the mold cavity shape was obtained.

  As shown in Tables 3 to 6, the conductive structure formed by the production method of the present invention is not produced by the production method of the present invention even when the raw material crystalline thermoplastic resin composite material is used. Compared with the conductive structure, it has high dimensional accuracy and low volume resistivity and low penetration resistance. Therefore, the production method of the present invention is suitable as a production method of a conductive structure that requires high dimensional accuracy and excellent conductivity, and is particularly suitable for a fuel cell separator that requires excellent dimensional accuracy and conductivity. It is optimal as a manufacturing method.

It is a schematic cross section for demonstrating the measuring method of penetration resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Test piece, 2 ... Gold-plated brass, 3 ... Voltmeter, 4 ... Constant current generator

Claims (14)

In the molding of a conductive structure made of a crystalline thermoplastic resin composite material containing at least a crystalline thermoplastic resin and a conductive filler, until the molding of the molten composite material in the mold is completed When the surface temperature of the mold cavity is defined as the crystal melting temperature (T _m ) of the composite material, it is kept at (T _m +5) ° C. or higher, and after shaping, the crystallization temperature of the composite material is adjusted to T _C And a temperature of the mold cavity is not lower than T _{C and not} higher than (T _C +15) ° C., and the composite material is solidified.   The conductive structure is solidified in a state in which the conductive structure is pressed with a mold, or in a state in which the conductive structure is pressed between correction plates that prevent deformation of the conductive structure. The manufacturing method of the electroconductive structure of Claim 1 to do.   The conductive structure according to claim 1 or 2, wherein the molding of the conductive structure is any one of molding methods selected from injection molding, injection compression molding, compression molding, and stamping molding. Manufacturing method.   The method for producing a conductive structure according to any one of claims 1 to 3, wherein the crystalline thermoplastic resin composite material further contains an elastomer. Crystalline thermoplastic resin, the elastomer and other polymer compounds as a polymer component, the total of the polymer component and a conductive filler as a reference (100 mass%), the polymer component is 40-2 wt%, conductivity The method for producing a conductive structure according to any one of claims 1 to 4, wherein the conductive filler is 60 to 98% by mass.   The method for producing a conductive structure according to claim 1, wherein at least one component contained in the crystalline thermoplastic resin is a polyolefin. Polymer components including crystalline thermoplastic resins, elastomers and other polymer compounds are hydrogenated styrene butadiene rubber, styrene / ethylene butylene / styrene block copolymers, styrene / ethylene propylene / styrene block copolymers, olefin crystals / ethylene butylene, One or more of olefin crystal block copolymer, styrene / ethylene butylene / olefin crystal block copolymer, styrene / isoprene / styrene block copolymer and styrene / butadiene / styrene block copolymer, and at least polyolefin The manufacturing method of the electroconductive structure of Claim 5 to do . 6. The method for producing a conductive structure according to claim 5, wherein the polymer component including the crystalline thermoplastic resin, the elastomer and the other polymer compound includes at least polyvinylidene fluoride and a soft acrylic resin.   9. The method according to claim 1, wherein the conductive filler is at least one selected from the group consisting of a metal material, a carbonaceous material, a conductive polymer, a metal-coated filler, or a metal oxide. The manufacturing method of the electroconductive structure as described in a term.   The method for manufacturing a conductive structure according to claim 1, wherein the conductive filler is a carbonaceous material containing 0.05 to 5 mass% of boron.   The conductive filler contains 0.1 to 50% by mass of vapor grown carbon fiber and / or carbon nanotube (based on the whole conductive filler containing them). A method for producing a conductive structure according to claim 1.   The method for producing a conductive structure according to claim 11, wherein the vapor grown carbon fiber or the carbon nanotube contains 0.05 to 5% by mass of boron. A conductive structure manufactured by the manufacturing method according to claim 1, and satisfying a relationship represented by X ≧ 0.8 × Y (Formula 1).
(However, in Formula 1, X represents a part of the conductive structure as a sample, and a differential melting calorimeter at a rate of temperature increase of 20 ° C./minute from 25 ° C. to the crystal melting temperature of the thermoplastic resin composite material: T _This represents the value obtained by dividing the heat of fusion of the crystal observed when the temperature is raised to 60 ° C. higher than _m by the mass of the sample, and the unit is J / g, and Y is a crystalline thermoplastic resin composite Using the material as a sample, using a differential scanning calorimeter, holding at 60 ° C. or higher than T _m for 10 minutes, cooling to 25 ° C. at a cooling rate of 5 ° C./min, and holding at 25 ° C. for 10 minutes Furthermore, it represents a value obtained by dividing the heat of fusion of the crystal observed when the temperature is raised to a temperature 60 ° C. higher than _{Tm at a} rate of temperature increase of 20 ° C./min divided by the mass of the sample, and the unit is J / g. is there.) A fuel cell separator using the conductive structure according to claim 13.

Images