JP2005200620A - Thermoplastic resin composition and thermoplastic resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recyclable thermoplastic resin composition excellent in conductivity, mechanical strength, flexibility, durability and surface smoothness, and also to provide a thermoplastic resin molded product prepared from the above composition. <P>SOLUTION: The thermoplastic resin composition comprises a thermoplastic resin, Ketchen black or carbon nanotubes and vapor-deposition carbon fibers. The thermoplastic resin molded product is prepared by molding the above composition. The above thermoplastic resin composition contains highly conductive Ketchen black or carbon nanotubes to give a molded product with high conductivity even with a small amount of the conductive material. Since the amount of the conductive material can be suppressed, the molding property of the composition is not deteriorated and the molded product with excellent flexibility is prepared. Further, vapor-deposition carbon fibers with small diameters are used to form a network to enhance the conductivity of the molded product, and to improve the strength, flexibility and durability as well. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoplastic resin composition excellent in conductivity, strength, flexibility, durability, and surface smoothness and suitable for recyclable fuel cell separator applications, and a heat formed by molding this thermoplastic resin composition. The present invention relates to a plastic resin molded product.

  Conventionally, fuel cell separators have been manufactured by cutting graphite or graphite impregnated with resin. However, in the case of cutting, the processing cost for forming a complicated fuel gas passage or cooling water passage on the surface is required. There was a drawback that it was expensive. Therefore, as a separator that can be molded without using a cutting process, a separator made of a metal material as a main material, a separator that is formed by press-molding a resin with a large amount of conductive filler such as graphite, and the like have been proposed. Among these, separators mainly made of metal materials have problems such as fuel cell output and long-term durability degradation due to generation of rust and ion elution, and in recent years, many studies have been made on resin-based materials.

The following method has been proposed as a method of molding a separator using a resin containing a conductive filler.
(1) A method in which a carbon material is added to a phenol resin and molded and then carbonized and fired (Japanese Patent Laid-Open No. 2001-143719)
(2) A method of forming a granular composite material by adding a large amount of carbon powder (200 parts by weight or more with respect to 100 parts by weight of the resin) to the resin, and molding this (JP-A-2000-182630)
(3) A method of press-molding a composite material in which a large amount (250 parts by weight or more with respect to 100 parts by weight of resin) of carbon powder is mixed with a thermosetting resin (Japanese Patent Laid-Open No. 2002-63913)
(4) A method of injection molding a material obtained by mixing carbon fibers chopped into a thermoplastic resin and carbon nanotubes (Japanese Patent Laid-Open No. 2002-97375)

JP 2001-143719 A JP 2000-182630 A JP 2002-63913 A JP 2002-97375 A

  However, in the method described in JP-A-2001-143719, it is necessary to perform carbonization firing after molding, and there is a problem that dimensional shrinkage in the graphitization process is unavoidable and strain at the time of shrinkage tends to remain. In the method described in JP-A-2000-182630, since a large amount of carbon powder is added to the resin, the flexibility of the material is remarkably impaired, and there is a problem that even a slight deformation is easy to break. In the method described in JP-A-2002-63913, since a thermosetting resin is used, there is a problem that it is difficult to recycle the material, and there is a problem that the molding time is long and the moldability is inferior. . In the method described in JP-A-2002-97375, since chopped carbon fiber is used, there is a problem that the surface smoothness of the molded product is easily impaired.

  The present invention solves the above-mentioned conventional problems, is excellent in conductivity, strength, flexibility, durability, surface smoothness, and is recyclable, and a thermoplastic resin composition suitable for fuel cell separator applications, and this heat It aims at providing the thermoplastic resin molded product formed by shape | molding a plastic resin composition.

  The 1st thermoplastic resin composition of this invention is characterized by including a thermoplastic resin, Ketjen black, and a vapor growth carbon fiber. If it is a thermoplastic resin composition to which ketjen black and vapor-grown carbon fiber are added in combination, it is possible to provide a thermoplastic resin molded article excellent in conductivity, strength, flexibility, durability, and surface smoothness. it can. Moreover, if it is a thermoplastic resin composition, recycling is also easy.

  In the first thermoplastic resin composition of the present invention, the blending amount of ketjen black is 5 to 30% by weight with respect to the total of the thermoplastic resin, ketjen black and vapor-grown carbon fiber, and vapor-grown carbon. The fiber content is preferably 10 to 60% by weight, in particular, the ketjen black content is preferably 10 to 25% by weight, and the vapor-grown carbon fiber content is preferably 25 to 50% by weight. The growth carbon fiber preferably has a fiber diameter of 50 to 200 nm.

  The 2nd thermoplastic resin composition of this invention is characterized by including a thermoplastic resin, a carbon nanotube, and a vapor growth carbon fiber. A thermoplastic resin composition having both carbon nanotubes and vapor-grown carbon fibers added together can provide a thermoplastic resin molded article excellent in conductivity, strength, flexibility, durability, and surface smoothness. . Moreover, if it is a thermoplastic resin composition, recycling is also easy.

  In the 2nd thermoplastic resin composition of this invention, the compounding quantity of a carbon nanotube is 1 to 20 weight% with respect to the sum total of a thermoplastic resin, a carbon nanotube, and a vapor growth carbon fiber, vapor growth carbon fiber of The blending amount is 10 to 70% by weight, in particular, the blending amount of the carbon nanotube is preferably 4 to 10% by weight, and the blending amount of the vapor growth carbon fiber is preferably 30 to 70% by weight. Those having a diameter of 1 to 50 nm are preferable, and vapor-grown carbon fibers having a fiber diameter of 50 to 200 nm are preferable.

  In the thermoplastic resin composition of the present invention, the thermoplastic resin is selected from the group consisting of polypropylene, polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyetheretherketone, polysulfone, polyethersulfone, and polyetherimide. One or two or more selected are preferably used, and polypropylene or polyphenylene sulfide is particularly preferably used.

  The thermoplastic resin molded article of the present invention is formed by molding such a thermoplastic resin composition of the present invention, and is excellent in conductivity, strength, flexibility, durability, surface smoothness, and recycling. Easy. The thermoplastic resin molded article of the present invention is particularly useful as a fuel cell separator.

  According to the present invention, a thermoplastic resin composition excellent in conductivity, strength, flexibility, durability, surface smoothness, and recyclable and suitable for fuel cell separator use, and molding the thermoplastic resin composition A thermoplastic resin molded article is provided.

  Embodiments of the thermoplastic resin composition and the thermoplastic resin molded article of the present invention will be described in detail below.

  The thermoplastic resin composition of the present invention has a first aspect and a second aspect. That is, the first thermoplastic resin composition of the present invention includes a thermoplastic resin, ketjen black, and vapor grown carbon fiber, while the second thermoplastic resin composition of the present invention includes a thermal resin. It contains a plastic resin, carbon nanotubes, and vapor grown carbon fibers.

  The thermoplastic resin used in the thermoplastic resin composition of the present invention is not particularly limited, but polypropylene, polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyether ether ketone, polysulfone, polyether sulfone and poly One type selected from the group consisting of ether imides, or a blend of two or more types may be mentioned. Of these, polypropylene and polyphenylene sulfide are preferable from the viewpoint of chemical stability.

  The ketjen black used in the first thermoplastic resin composition of the present invention is a kind of carbon black and is a carbon black having higher conductivity than conventional carbon black. The excellent performance of ketjen black is due to the fact that ketjen black has a hollow shell structure unlike other carbon blacks. Typical types of ketjen black include ketjen black EC, ketjen black EC-600JD, etc., and each exhibits the following properties.

  On the other hand, the carbon nanotube (CNT) related to the second thermoplastic resin composition of the present invention is a macromolecule in which carbon atoms are bonded in a cylindrical shape, and has high conductivity. Ordinary graphite is formed by stacking layers (graphene sheets) in which carbon atoms bonded in a honeycomb shape spread in a plane, but CNT has a structure in which graphene sheets are rounded into a cylindrical shape. Graphene sheet 1 A layer formed in a cylindrical shape is referred to as a single-walled CNT (SWNT), and a structure in which two or more layers are formed in a concentric cylindrical shape is referred to as a multilayer CNT (MWNT). Further, among SWNTs and MWNTs, they may be further finely classified depending on differences in diameter, the number of graphene sheet layers, how to wind the graphene sheet (chirality), and the like. Examples of CNT manufacturing methods include arc discharge, laser evaporation, and CVD.

  The CNT used in the second thermoplastic resin composition of the present invention may be produced by any of the above-described production methods, and may be any one of SWNT and MWNT, or a mixture of two or more. The CNT used in the present invention preferably has an arpect ratio (length / diameter ratio) of about 10 to 1000, and preferably has a fiber diameter in the range of 1 to 50 nm.

  Moreover, the vapor growth carbon fiber related to the thermoplastic resin composition of the present invention is a carbon fiber obtained by a vapor growth method. There are two types of methods for producing vapor-grown carbon fibers: a substrate method and a fluidized bed method. The substrate method is a method in which a metal catalyst is directly attached to a substrate, and this is installed in a furnace core tube, and a hydrocarbon gas is flowed in at a high temperature using an electric furnace to generate carbon fibers on the substrate. In this method, carbon fibers are generated on the substrate, and the generated carbon fibers are left under reaction conditions for a long time inside the core, so that the fiber diameter is increased. On the other hand, the fluidized bed method is a method in which both a hydrocarbon gas and a metal catalyst are caused to flow into the core at a high temperature to generate carbon fibers by a short reaction, and a fiber having a relatively small fiber diameter can be obtained.

  The vapor growth carbon fiber used in the present invention may be produced by any of the above methods, but the fiber diameter is preferably in the range of 50 to 200 nm. If the fiber diameter of the vapor-grown carbon fiber is less than 50 nm, the cohesive force is large, so that uniform dispersion in the resin is difficult. If it exceeds 200 nm, high conductivity is obtained when it is combined with the resin. It becomes difficult. In addition, it is preferable that the fiber length of vapor growth carbon fiber is about 1-10 micrometers normally, and an aspect-ratio (length / diameter ratio) is about 10-1000.

  By using such a vapor-grown carbon fiber having a small fiber diameter, it is possible to increase the conductivity, the strength, the flexibility, and the durability of the obtained molded product through a network of carbon fibers. Moreover, since such a vapor-grown carbon fiber having a small diameter is used, the surface smoothness of the obtained molded product is also good.

  In the first thermoplastic resin composition of the present invention, the amount of ketjen black and vapor-grown carbon fiber is the same as that of the thermoplastic resin, ketjen black and vapor-grown carbon fiber. 5 to 30% by weight, especially 10 to 25% by weight, vapor-grown carbon fiber is 10 to 60% by weight, especially 25 to 50% by weight, and the total amount of ketjen black and vapor-grown carbon fiber is 40 It is preferable to set it to -75 weight%, especially 50-70 weight%. If the amount of ketjen black and vapor-grown carbon fiber is less than the above range, the effect of each addition cannot be obtained sufficiently, and if it is too large, moldability, strength, etc. are impaired.

  In the first thermoplastic resin composition of the present invention, ketjen black and vapor-grown carbon fiber are used in combination in order to obtain a molded article having an excellent balance of conductivity, strength and flexibility. The blending ratio of chain black and vapor grown carbon fiber is preferably 10 to 300 parts by weight with respect to 100 parts by weight of vapor grown carbon fiber.

  On the other hand, in the second thermoplastic resin composition of the present invention, the compounding amount of the carbon nanotube and the vapor grown carbon fiber is 1 for the total amount of the thermoplastic resin, the carbon nanotube and the vapor grown carbon fiber. -20% by weight, especially 4-10% by weight, vapor-grown carbon fiber is 10-70% by weight, especially 30-70% by weight, and the total amount of carbon nanotubes and vapor-grown carbon fiber is 15-15% It is preferably 80% by weight, particularly 30 to 75% by weight. If the blending amount of the carbon nanotube and the vapor grown carbon fiber is less than the above range, the effect of each addition cannot be obtained sufficiently, and if it is large, the moldability, strength and the like are impaired.

  The thermoplastic resin composition of the present invention includes glass fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, and ceramic within the range not impairing the effects of the present invention. Fibrous fillers such as fibers, asbestos fibers, masonry fibers and metal fibers, wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, alumina silicate, etc. Metal oxides such as alumina, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide and iron oxide, carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, magnesium hydroxide and hydroxide Calcium, aluminum hydroxide What hydroxide, glass beads, glass flakes, ceramic beads, boron nitride, may be incorporated one or more of such non-fibrous fillers such as silicon carbide and silica. Further, for the purpose of obtaining better mechanical strength, these fibrous / non-fibrous fillers are used as coupling agents such as isocyanate compounds, organic silane compounds, organic titanate compounds, organic borane compounds, epoxy compounds, and the like. It may be used after pretreatment.

  Furthermore, the thermoplastic resin composition of the present invention includes nucleating agents such as talc, kaolin, organophosphorus compounds, polyether ether ketone, coloring inhibitors such as hypophosphite, oxidations such as hindered phenols and hindered amines. Functional agents such as inhibitors, heat stabilizers, lubricants, UV inhibitors, colorants such as dyes and pigments, and antistatic agents can be added.

  The method for producing the thermoplastic resin composition of the present invention is not particularly limited, and ketjen black or carbon nanotubes, vapor-grown carbon fibers, and other additive components blended as necessary are collectively contained in the thermoplastic resin. After dry blending, it can be produced by melt-kneading with an extruder, kneader, Banbury mixer or the like. Further, it may be manufactured by melt-kneading a pellet obtained by melt-extruding a thermoplastic resin and vapor-grown carbon fiber, ketjen black or carbon nanotubes, and other additive components. Or you may manufacture by melt-kneading the masterbatch formed by mix | blending a carbon nanotube, a vapor growth carbon fiber, and another additive component. In order to uniformly disperse and knead vapor-grown carbon fibers and ketjen black or carbon nanotubes in a thermoplastic resin, a method such as kneading with a lab plast mixer in the case of a batch type or a twin screw extruder in the case of a continuous type Is preferably adopted.

  The thermoplastic resin molded article of the present invention is formed by molding the thermoplastic resin composition, and is excellent in conductivity, strength, flexibility, durability and surface smoothness, and can be easily recycled. In addition, there is no restriction | limiting in particular in the manufacturing method of the thermoplastic resin molded product of this invention, Injection molding, injection compression molding, press molding, etc. can be used. In this case, the thermoplastic resin, ketjen black or carbon nanotube, vapor-grown carbon fiber, and other additive components blended as necessary may be dry blended together and then directly injection molded, or once All components may be melt extruded and pelletized before injection molding.

  As a molded article obtained by molding the thermoplastic resin composition of the present invention, a fuel cell separator is particularly suitable, but in addition, pallets, trays, packaging materials, substrates, etc. that require electrical conductivity and antistatic function. It can also be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by the following examples unless it exceeds the gist.

In the following examples and comparative examples, the molding materials used are as follows.
PPS-1: Polyphenylene sulfide “Fortron 0220A9” manufactured by Polyplastics Co., Ltd.
PPS-2: Polyphenylene sulfide “LR-03G” manufactured by Dainippon Ink, Inc.
PPS-3: Polyphenylene sulfide “Sasteel B-100” manufactured by Tosoh Corporation
PP-1: Nippon Polychem Polypropylene "BC6C"
KB: Ketjen Black “EC-600JD” manufactured by Lion
VGCF: Vapor growth carbon fiber “VGCF-R” manufactured by Showa Denko KK, average fiber diameter 150 nm
PP-2 and CNT: PP (polypropylene) / CNT (carbon nanotube) masterbatch “MB3020-01” manufactured by Hyperion, average fiber diameter of CNT: 10 nm

Examples 1-6, Comparative Examples 1-2
The ingredients shown in Table 2 or Table 3 are used to produce a thermoplastic resin composition by kneading each component with "Lab Plast Mill R30" manufactured by Toyo Seiki Co., Ltd. After kneading, necessary test pieces are produced by press molding. The following characteristic evaluation was performed, and the results are shown in Table 2 or Table 3.

[Volume resistivity]
The sheet-shaped test piece having a thickness of 1 mm was measured by “Loresta” manufactured by Mitsubishi Chemical Corporation by the four-end needle method.

[Bending strength and bending strain]
According to JIS K6911, bending strength was measured as an index of strength, and bending strain was measured as an index of flexibility.

[durability]
100 mL of pure water and 6 test pieces of 80 mm × 10 mm × 4 mm were put in a pressure vessel, the weight of the test piece after 700 hours at 150 ° C. was measured, and the rate of change from the initial weight was calculated.

  From Table 2, in Comparative Example 1 using only vapor-grown carbon fiber, the bending strength and bending strain are good, but the volume resistivity is too large, so that it is a material that satisfies all the conductivity, strength, and flexibility. On the other hand, according to the thermoplastic resin compositions of Examples 1 to 3 blended with ketjen black and vapor-grown carbon fiber, the conductivity, strength, and flexibility were all excellent. It turns out that the molded article which shows a characteristic can be obtained. All of these molded articles were good in surface smoothness.

  From Table 3, in Comparative Example 2 using only vapor-grown carbon fibers, the bending strength and bending strain are good, but the volume resistivity is too large. I understand that it is not. On the other hand, according to the thermoplastic resin compositions of Examples 4 to 6 in which carbon nanotubes and vapor grown carbon fibers are used in combination, a molded product exhibiting excellent properties in all of conductivity, strength and flexibility. It can be seen that can be obtained.

Claims (14)

  A thermoplastic resin composition comprising a thermoplastic resin, ketjen black, and vapor grown carbon fiber.   In Claim 1, the compounding quantity of ketjen black is 5 to 30 weight% with respect to the sum total of a thermoplastic resin, ketjen black, and a vapor growth carbon fiber, and the compounding quantity of a vapor growth carbon fiber is a heat | fever. A thermoplastic resin composition, characterized by being 10 to 60% by weight based on the total of the plastic resin, ketjen black and vapor grown carbon fiber.   In Claim 2, the compounding quantity of ketjen black is 10-25 weight% with respect to the sum total of a thermoplastic resin, ketjen black, and vapor growth carbon fiber, and the compounding quantity of vapor growth carbon fiber is heat | fever. A thermoplastic resin composition characterized by being 25 to 50% by weight based on the total of the plastic resin, ketjen black and vapor grown carbon fiber.   The thermoplastic resin composition according to any one of claims 1 to 3, wherein the vapor-grown carbon fiber has a fiber diameter of 50 to 200 nm.   5. The group according to claim 1, wherein the thermoplastic resin is made of polypropylene, polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyetheretherketone, polysulfone, polyethersulfone, and polyetherimide. A thermoplastic resin composition characterized by being one or more selected from the group consisting of:   6. The thermoplastic resin composition according to claim 5, wherein the thermoplastic resin is polypropylene or polyphenylene sulfide.   A thermoplastic resin composition comprising a thermoplastic resin, carbon nanotubes, and vapor-grown carbon fibers.   In Claim 7, the compounding quantity of a carbon nanotube is 1 to 20 weight% with respect to the sum total of a thermoplastic resin, a carbon nanotube, and a vapor growth carbon fiber, and the compounding quantity of a vapor growth carbon fiber is a thermoplastic resin. The thermoplastic resin composition is characterized by being 10 to 70% by weight based on the total of carbon nanotubes and vapor-grown carbon fibers.   In Claim 8, the compounding quantity of a carbon nanotube is 4 to 10 weight% with respect to the sum total of a thermoplastic resin, a carbon nanotube, and a vapor growth carbon fiber, and the compounding quantity of a vapor growth carbon fiber is a thermoplastic resin. The thermoplastic resin composition is 30 to 70% by weight based on the total of carbon nanotubes and vapor-grown carbon fibers.   The thermoplastic resin composition according to any one of claims 7 to 9, wherein the carbon nanotube has a fiber diameter of 1 to 50 nm, and the vapor-grown carbon fiber has a fiber diameter of 50 to 200 nm.   The group according to any one of claims 7 to 10, wherein the thermoplastic resin is composed of polypropylene, polyvinylidene fluoride, polyphenylene sulfide, polyphenylene oxide, polyamideimide, polyetheretherketone, polysulfone, polyethersulfone, and polyetherimide. A thermoplastic resin composition characterized by being one or more selected from the group consisting of:   The thermoplastic resin composition according to claim 11, wherein the thermoplastic resin is polypropylene or polyphenylene sulfide.   A thermoplastic resin molded article obtained by molding the thermoplastic resin composition according to any one of claims 1 to 12.   The thermoplastic resin molded article according to claim 13, which is a fuel cell separator.