JP2007250207A - Conductive wax, conductive molding material, and conductive molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive wax capable of easily and stably improving surface conductivity of a molded product without degrading other characteristics in case of use for forming of a molded product made of a conductive polymer material such as a separator for a fuel cell, and to provide a conductive molding material as well as a conductive molded product using such a conductive wax. <P>SOLUTION: The conductive wax containing (a) nano-carbon and (b) wax, the conductive molding material and the conductive molded product including such a conductive wax are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive wax used when manufacturing a conductive molded article such as a separator of a fuel cell, and a conductive molding material and a conductive molded article using such a conductive wax.

  A separator made of graphite and resin is known as a separator used in fuel cells for automobiles, mobiles, homes, etc. Generally, graphite powder and resin are mixed and formed into a predetermined shape. It is manufactured by. The separator produced in this way contains a release agent, or because the release agent is applied at the time of molding, a skin layer with a very low content of conductive graphite is formed on the surface, As a result, there is a problem that the electrical resistance of the surface is increased and desired conductivity cannot be obtained.

  Therefore, measures such as scraping the skin layer on the surface by solvent washing or blasting using walnut powder after molding have been taken. Also proposed is a method of reducing the electrical resistance of the surface by applying a voltage using a separator made of resin and graphite as an anode in an organic solvent in which carbon nanotubes are dispersed, and attaching the carbon nanotubes to the separator surface. (For example, refer to Patent Document 1).

  However, in the former, problems such as a decrease in strength and gas permeation occurred by scraping the skin layer. In the latter case, the equipment is complicated, the adhesion stability of carbon nanotubes is lacking, and there are also problems in terms of safety. For this reason, there is a need for a measure that can stably increase the surface conductivity without causing other problems such as a decrease in strength.

  Normally, when manufacturing molded products made of rubber or resin in which conductive powder is dispersed, wax is used as the molding material to reduce the frictional resistance against the metal surface of the processing machine to prevent adhesion and facilitate processing. Or adding wax to the surface of a mold or the like.

However, conventional waxes are electrically insulating, and by using these waxes, a thin insulating layer made of wax is formed on the surface of the molded product, and as a result, there is a problem that the electrical resistance of the surface increases. For this reason, the countermeasure which can prevent the surface conductivity fall accompanying use of a wax is calculated | required.
JP 2005-235425 A

  As described above, there is a need for a technique that can easily and stably improve the surface conductivity of a resin separator used in a fuel cell without causing a decrease in strength or the like. In addition, there is a demand for a technique capable of improving the surface conductivity of a conductive molded article using wax.

  The present invention has been made to solve such problems of the prior art, and when used for forming a molded article made of a conductive polymer material such as a resin separator of a fuel cell, its surface conductivity is reduced. An object of the present invention is to provide a conductive wax that can be easily and stably improved without deteriorating other characteristics, and a conductive molding material and a conductive molded article using such a conductive wax. To do.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a wax having excellent conductivity by combining nanocarbon with wax, and using this, a resin separator for a fuel cell, etc. The present inventors have found that the surface conductivity of a molded article made of the conductive polymer material can be improved, and the present invention has been completed.

  That is, the first invention of the present application is a conductive wax containing (a) nanocarbon and (b) wax.

  According to a second aspect of the present invention, there is provided a conductive molding material comprising the conductive wax.

  Furthermore, a third invention of the present application is a conductive molded article including the conductive wax.

  The conductive wax of the present invention, when used to form a molded article made of a conductive polymer material such as a resin separator of a fuel cell, can easily and stably maintain its surface conductivity without deteriorating other characteristics. Can be improved.

  In addition, since the conductive molding material and the conductive molded article of the present invention contain the conductive wax having such characteristics, it is possible to stably have high surface conductivity without impairing other characteristics. it can.

Hereinafter, the present invention will be described in detail.
The (a) nanocarbon used in the conductive wax of the present invention is nano-sized carbon particles such as carbon nanofiber (CNF), single-walled carbon nanotube (CNT), double-walled carbon nanotube (DWCNT), and multilayer. Examples include carbon nanotubes (MWCNT), peapots, fullerenes and the like. In addition, so-called metal-encapsulated fullerene obtained by encapsulating metal in fullerene can also be used. These are used alone or in combination. In the present invention, carbon nanofibers and single-walled carbon nanotubes (CNT) are particularly preferable.

  Specific examples of carbon nanofiber (CNF) include carbon nanofiber VGCF (diameter 150 nm, length 8 μm; trade name) and carbon nanofiber VGCF-S (diameter 100 nm, length 10 μm; trade name) manufactured by Showa Denko KK ). Examples of the carbon nanotube (CNT) include carbon nanotube XS series, XD series, YM series, CCE series (above, trade names) manufactured by Carbon Nanotechnology Inc. (USA). Other carbon nanotubes (CNTs) are, for example, Bucky, Carborex, Hyperion Catalysis, Materials and Electrochemical Research Corporation, Nanos, Nanolab, Nanoledge (above, USA), and Gwangzo Yorkpoint Technology. (Guangzhou Yorkpoint Technology), Iijin nanotech, Sunnanotech (China), Rosetta Holding (Cyprus), Mitsui Carbon Nanotech Research Laboratories, Showa Denko, etc. In addition, multi-walled carbon nanotubes (MWCNT) having a diameter of 20 nm are available from Nikkiso Co., Ltd.

  The content of the (a) nanocarbon in the conductive wax is preferably in the range of 1 to 90% by mass, more preferably in the range of 10 to 50% by mass with respect to the entire conductive wax. If it is less than 1% by mass, the effect of addition cannot be sufficiently obtained. Conversely, if it exceeds 90% by mass, the adhesion function as a wax is lowered.

  The (b) wax used in the conductive wax of the present invention is not particularly limited, and one or more kinds of conventionally known waxes or lubricants may be appropriately selected and used depending on the application. Can do. Specifically, liquid paraffin (liquid at normal temperature, hereinafter referred to simply as liquid), natural paraffin (paste or solid at normal temperature), micro wax (solid at normal temperature, hereinafter simply referred to as solid), polyethylene wax (solid) Such as lauric acid (solid), stearic acid (solid), etc .; stearic acid amide (solid), palmitic acid amide (solid), methylene bisstearamide (solid), ethylene bisstearamide (Solid), fatty acid amides such as oleic amide (solid), ethyl amide (solid); fatty acid esters such as butyl stearate (liquid), hydrogenated castor oil (solid), ethylene glycol monostearate (liquid) Fatty alcohols such as cetyl alcohol (liquid) and stearyl alcohol (solid); lead stearate (solid) , Aluminum stearate (solid), a metal soap such as magnesium stearate (solid); mixed system, and the like. In the present invention, those which are solid at room temperature are preferred, and polymer waxes such as microwax and polyethylene wax are particularly preferred.

  For example, commercially available products include AC polyethylene 6, AC polyethylene 617, AC polyethylene 617A, AC polyethylene 629, and AC polyethylene 629 manufactured by Allied Chemical Co., Eastman Chemical. Epolene N-11 manufactured by Mitsui Chemicals, Inc. Exelex 10500, Exelex 20700, Exelex 40800, Exelex 30200B, Exelex 30050B, Exelex 48070B, Exelex 20400PM, Exelex 15341PA (Product name). In addition, as solids at room temperature other than the polymer wax, Amide S (mp: 100-105 ° C), Amide T (mp: 97-102 ° C), Amide P (mp: 95-100 ° C.), Armide HT (mp: 93-103 ° C.), Armido O (mp: 68 ° C.), Armide C (mp: 85 ° C.), Armoslip E (mp: 84) ), Armo slip CP (mp: 68-74 ° C.), Armo wax (mp: 130 ° C.), Armo wax EBS (mp: 140 ° C.), Alfro E-10 (mp: 73) manufactured by NOF Corporation. -74 ° C.), Alflow H-10 (mp: 70 ° C.), Emulgen (mp: 59 ° C.), Hard beef tallow oil (mp: 57 ° C.), Sakurain beef tallow sterin (mp: 57.5 ° C.) The same Mume acetyl (mp: 42-4 ° C.), Bamboo stamped powder stearic acid (mp: 57 ° C.), Nissan castor wax A (mp: 84 ° C.), Nissan New Loop A (mp: 56 ° C.), Panaceto S218 (Mp: 40-45 ° C), pinasol NAA46 (mp: 50-54 ° C), pinasol NAA48 (mp: 50-54 ° C), behenic acid NAA211 (mp: 57.5-60.5 ° C), Same behenic acid NAA222 (mp: 69-75 ° C), Monogly M (mp: 53-61 ° C), VLA-1 (mp: 126-130 ° C), VLTN-4 (mp: 60 ° C.), K-3 (mp: 85-87 ° C.), castor hardness (mp: 85-87 ° C.) (above, trade name), and the like.

  The content of the wax (b) in the conductive wax is preferably in the range of 10 to 99% by mass, more preferably in the range of 50 to 90% by mass with respect to the entire conductive wax. When the amount is less than 1% by mass or exceeds 90% by mass, the effect as a lubricant may not be sufficiently exhibited.

  In the conductive wax of the present invention, components other than the above components may be blended depending on the purpose of use and conditions of use and in a range not violating the purpose of the present invention. For example, when the conductive wax of the present invention is applied to the surface of a mold or the like and used, (c) a solvent can be blended. Specific examples of the solvent include alcohols such as methanol and ethanol, aromatics such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and these are used alone or in combination.

  The conductive wax of the present invention is prepared into a liquid, a paste, a grease, or a solid by mixing each of the above components using a normal mixer or kneader. The mixer or kneader used for mixing is appropriately selected depending on the type of wax used (b). For example, in the case of wax that becomes a low-viscosity liquid by heating or the like, a chemical reaction vessel with a stirring blade, a universal mixer A high intensity mixer with stirring blades is used. In the case of a wax that becomes a high-viscosity liquid by heating or the like, the above-described universal mixer can be used, but a uniaxial or biaxial rotary screw type kneading extruder is preferred. A biaxial roll kneader can also be used, and when the solvent (c) is used, the above-described chemical reaction vessel with stirring blades can also be used.

  In the present invention, the mixing or kneading time of each component is preferably 0.3 to 0.9 times the time required to completely and uniformly mix (a) nanocarbon and (b) wax. By setting it as such mixing time, the electroconductive effect can fully be exhibited. If kneading is advanced excessively, the conductive effect may be reduced. Here, the time required to completely and uniformly mix the (a) nanocarbon and the (b) wax is a state in which no lumps are observed when the dispersion state is observed with an SEM (electron microscope) over time. Say.

  The conductive wax of the present invention may be added directly to a conductive molding material as a material when molding a conductive molded product, or a mold, a metal roll, etc. used for molding a conductive molded product. You may make it apply to the surface of a processing machine by normal application means, such as a brush coating method and a spraying method. When used by adding to a conductive molding material, during molding, when the material heats and melts, the wax oozes out to the surface to form a conductive wax layer containing nanocarbon on the surface, When applied to the surface of a processing machine such as a mold or metal roll, the conductive wax layer formed on the surface of the processing machine is transferred to the surface of the molded product during molding, resulting in excellent surface conductivity. A conductive molded product can be obtained.

  The conductive molding material to which the conductive wax of the present invention is applied is not particularly limited, and is based on rubber or resin, and as a conductive powder, for example, carbon powder such as graphite and carbon black, iron, copper Contains metal powders such as silver, aluminum and nickel, metal oxide powders such as triiron tetroxide, tin oxide and indium oxide, inorganic powders such as titanium nitride and silicon carbide, organic powders such as polyaniline, polypyrrole and polyacetylene The thing which was done is mentioned. The base rubber is natural rubber, styrene / butadiene rubber, butadiene rubber, butyl rubber, isoprene rubber, nitrile / butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, chloroprene rubber, neoprene rubber, urethane rubber, norbornene. Examples thereof include rubber, epichlorohydrin rubber, fluorine rubber, silicone rubber, and various thermoplastic elastomers. In addition, as the resin, polyethylene, polypropylene, polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, polybutadiene, polycarbonate, polyacrylonitrile, ABS resin, AES resin, nylon resin, polyetherimide, polyetheretherketone, polysulfone, polysulfone Thermoplastic resins such as allylamine, polyphenylene oxide, petroleum resin, polytetrafluoroethylene, polyvinyl fluoride, polydimethylsiloxane, epoxy resin, phenol resin, phthalic acid resin, polyimide, polyurethane, furan resin, xylene-formaldehyde resin, melamine resin And thermoplastic resins such as urea resin, polyester resin and unsaturated polyester resin.

  Next, an embodiment of the conductive molded article of the present invention using the conductive wax of the present invention will be described with reference to the drawings.

  That is, FIG. 1 is an exploded perspective view showing a configuration of a fuel cell including a fuel cell separator according to an embodiment of the conductive molded article of the present invention.

  In FIG. 1, reference numeral 1 denotes an electrolyte plate. A negative electrode 2 and a positive electrode 3 are disposed with the electrolyte plate 1 interposed therebetween, and separators 4 and 5 are disposed with the electrolyte plate 1 interposed therebetween. Each of the separators 4 and 5 is made of a conductive molding material containing the conductive wax of the present invention, and oxygen and hydrogen flowing between the negative electrode 2 and the positive electrode 3, each electrode, Grooves 4a and 5a for increasing the contact area are provided.

  In the fuel cell configured as described above, since the layer made of the conductive wax of the present invention is formed on the surface of each separator 4, 5, it can have good surface conductivity.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

Example 1 and Comparative Example 1
500 g of carnauba wax (trade name Carnauba No. 1 manufactured by Toa Kasei Co., Ltd.) was weighed into a universal mixer and dissolved at 90 ° C., followed by 50 g of carbon nanofiber (trade name VGCF-S manufactured by Showa Denko KK). Was added in small portions over 30 minutes, and then mixed for 30 minutes to prepare a conductive wax.

  Next, 0.5 parts by mass of the obtained conductive wax, 90 parts by mass of graphite powder, and 9.5 parts by mass of a resol phenol resin (trade name BRM-4705, manufactured by Showa Polymer Co., Ltd.) were mixed to conduct electricity. A thermosetting resin molding material was prepared.

  For comparison, a conductive thermosetting resin molding material was prepared in the same manner as in Example 1 except that the carnauba wax was used instead of the conductive wax (Comparative Example 1).

  Using the obtained conductive thermosetting resin molding material, a disk-shaped molded product having a diameter of 100 mm and a thickness of 3 mm was prepared by compression molding, and the surface resistivity was measured. As a result, Example 1 was found to be 2.80 mΩ · Whereas it was cm, Comparative Example 1 was 4.14 mΩ · cm, and the effect of the present invention was confirmed.

Example 2 and Comparative Example 2
500 g of carnauba wax (trade name Carnauba No. 1 manufactured by Toa Kasei Co., Ltd.) was weighed into a universal mixer and dissolved at 90 ° C., and then carbon nanofiber (trade name VGCF-S manufactured by Showa Denko KK) 250 g Was added in small portions over 60 minutes, and then mixed for 30 minutes to prepare a conductive wax.

  Next, 0.5 parts by mass of the obtained conductive wax, 90 parts by mass of graphite powder, and 9.5 parts by mass of a resol phenol resin (trade name BRM-4705, manufactured by Showa Polymer Co., Ltd.) were mixed to conduct electricity. A thermosetting resin molding material was prepared.

  For comparison, a conductive thermosetting resin molding material was prepared in the same manner as in Example 2 except that the carnauba wax was used instead of the conductive wax (Comparative Example 2).

  A disk-shaped molded product having a diameter of 100 mm and a thickness of 3 mm was produced by compression molding using the obtained conductive thermosetting resin molding material, and the surface resistivity was measured. Whereas it was cm, Comparative Example 2 was 4.16 mΩ · cm, confirming the effect of the present invention.

Example 3 and Comparative Example 3
After mixing 5000 g of polyethylene wax (trade name AC polyethylene 6 manufactured by Allied Chemical Co., Ltd.) and 500 g of carbon nanofiber (trade name VGCF manufactured by Showa Denko Co., Ltd.) with a Hensial mixer, the mixture was put into a twin screw kneading extruder. The mixture was heated and kneaded at 90 ° C. After cooling, the mixture was frozen and pulverized to prepare a conductive wax.

  Next, 0.5 parts by mass of the obtained conductive wax, 90 parts by mass of graphite powder, and 9.5 parts by mass of a resol phenol resin (trade name BRM-4705, manufactured by Showa Polymer Co., Ltd.) were mixed to conduct electricity. A thermosetting resin molding material was prepared.

  For comparison, a conductive thermosetting resin molding material was prepared in the same manner as in Example 3 except that the carnauba wax was used instead of the conductive wax (Comparative Example 3).

  A disk-shaped molded product having a diameter of 100 mm and a thickness of 3 mm was produced by compression molding using the obtained conductive thermosetting resin molding material, and the surface resistivity was measured. As a result, Example 3 was found to be 2.41 mΩ · Whereas it was cm, Comparative Example 3 was 4.17 mΩ · cm, confirming the effect of the present invention.

Example 4 and Comparative Example 4
500 g of methyl ethyl ketone is weighed into a 2 L chemical reaction flask, 50 g of calcium stearate is added and dissolved by heating at 50 ° C., and 5 g of carbon nanofiber (trade name VGCF-S, manufactured by Showa Denko KK) is then added in small portions. A liquid conductive wax was prepared. In addition, 90 parts by mass of graphite powder, 9.9 parts by mass of resol phenol resin (trade name BRM-4705, manufactured by Showa Polymer Co., Ltd.), and carnauba wax (trade name, Carnabar No. 1 manufactured by Toa Kasei Co., Ltd.) 0. 1 part by mass was mixed to prepare a conductive thermosetting resin molding material.

  A disk-shaped molded product having a diameter of 100 mm and a thickness of 3 mm was produced by compression molding using the obtained conductive thermosetting resin molding material. At that time, the conductive wax was sprayed onto the surface of the molded plate and dried to be molded.

  For comparison, instead of conductive wax, 500 g of methyl ethyl ketone was weighed into a 2 L chemical reaction flask, 55 g of calcium stearate was added, and heated and dissolved at 50 ° C. for molding. A disc-shaped molded product having a diameter of 100 mm and a thickness of 3 mm was produced in the same manner as in Example 4 except that the above was compared (Comparative Example 4).

  When the surface resistivity of the molded products obtained in Example 4 and Comparative Example 4 was measured, Example 4 was 2.40 mΩ · cm, while Comparative Example 4 was 4.04 mΩ · cm. The effect of the present invention was confirmed.

Example 5
500 g of carnauba wax (trade name Carnauba No. 1 manufactured by Toa Kasei Co., Ltd.) was weighed into a universal mixer and dissolved at 90 ° C., followed by 200 g of carbon nanofiber (trade name VGCF-S manufactured by Showa Denko KK). Were added and mixed by the methods (i) to (ix) shown in Table 1 to prepare a conductive wax.

  Next, the obtained conductive wax was observed with an SEM (electron microscope) to examine the presence or absence of lumps. Further, using the obtained conductive wax, a conductive thermosetting resin molding material was prepared in the same manner as in Example 1, and the diameter was further measured by compression molding using these conductive thermosetting resin molding materials. A disk-shaped molded product having a thickness of 100 mm and a thickness of 3 mm was produced, and the surface resistivity was measured. These results are also shown in Table 1.

  As is apparent from Table 1, the conductive wax uniformly mixed until no lumps are observed by observation with an electron microscope has a large surface resistivity, as in the case of the conductive wax having a short mixing time.

  Since the conductive wax of the present invention can easily and stably improve the surface resistance of a conductive molded product for the purpose of conductivity without deteriorating other properties, high surface conductivity is required. It is particularly useful for applications such as fuel cell separators.

It is a disassembled perspective view which shows the structure of the fuel cell provided with the separator for fuel cells of one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrolyte board, 2 ... Negative electrode, 3 ... Positive electrode, 4, 5 ... Separator

Claims (7)

  A conductive wax comprising (a) nanocarbon and (b) a wax.   (A) The conductive wax according to claim 1, which contains 1 to 90% by mass of nanocarbon.   3. The conductive wax according to claim 1, further comprising (c) a solvent.   (A) Nanocarbon and (b) wax are mixed, and the mixing time is 0.3 to 0. 0 of the time required to completely and uniformly mix (a) nanocarbon and (b) wax. The conductive wax according to claim 1, wherein the conductive wax is 9 times.   A conductive molding material comprising the conductive wax according to claim 1.   A conductive molded article comprising the conductive wax according to claim 1.   The conductive molded article according to claim 6, wherein the conductive molded article is a fuel cell separator.

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