JP2004188286A - Thermally conductive coat and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coat the matrix component of which is a resin, the carbon nanomaterial of which is oriented parallel to the surface of a member at the site of mechanical part production, and which is excellent in thermal conductivity in the direction parallel to the surface of the member. <P>SOLUTION: The carbon nanomaterial selected from carbon nanotubes and carbon nanofibers is mixed with a resin being the matrix component, and the thermally conductive coat is molded from the resulting mixture. The mixed powder is thermally sprayed in the direction vertical to the surface of a member to form an anisotropically thermally conductive coat in which the longitudinal parts of the carbon nanomaterial are oriented in the direction parallel to the surface of the member. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat conductive film formed on a conductive surface of a heating product or a heat radiating product that requires rapid heat absorption and heat radiation, and a method of forming the same.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-38033 (Patent Document 1) discloses that at least one selected from carbon nanotubes and carbon nano materials of carbon microcoils is mixed with a silicone rubber composition as a matrix (matrix) component of a coating. It is disclosed that the mixture is applied to a member by a method such as a spray method or a dipping method, or the mixture is poured and cured to form a heat conductive sheet. Carbon nanomaterials have high thermal conductivity, and if a mixture in which carbon nanomaterials are mixed is applied to a member, the coating has excellent thermal conductivity. However, when the arrangement direction of the carbon nanotubes varies, and when the spray method or the dipping method is used, it is necessary that the coating material is liquid. When the matrix component of the coating is a resin, the solvent for dissolving them is not present, so that the coating forming method of Patent Document 1 cannot be applied.
[0003]
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-60639 (Patent Document 2) discloses a method of kneading a curable resin / curable resin composition and a carbon nanomaterial, and then molding the cured product by any one of injection molding, compression molding, and transfer molding. Is disclosed. Since carbon nanomaterials are very minute materials having a nanometer size and have a very small specific gravity, even if a resin composite material is molded by the method of Patent Document 2, the resin flows in the resin flow direction (parallel to the member surface). It is not possible to control the arrangement of carbon nanomaterials. Therefore, the coating formed by the method of Patent Document 2 has a different arrangement direction of the carbon nanotubes.
[0004]
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2001-272840 (Patent Document 3) discloses that carbon nanotubes are arranged in parallel, a conductive adhesive is applied to the surface of conductive rubber with a thickness of 1 μm, and then the carbon nanotubes arranged in parallel are made conductive. It is disclosed that the carbon nanotubes are pressed against and adhered to a conductive adhesive to arrange the carbon nanotubes in parallel in an arbitrary direction. In order to arrange the carbon nanotubes in parallel, first, a dispersion of the carbon nanotubes in ethanol is applied to a ceramic filter having a pore size of 0.2 μm, and the carbon nanotubes are arranged upright and in parallel in the holes of the ceramic filter. The carbon nanotube is transferred to the polyacetal while standing upright by electrostatically adsorbing the polyacetal (trade name: Delrin). When this is rubbed, the upright carbon nanotubes are arranged parallel to the polyacetal. However, working under such a microscope is not suitable for the production site of ordinary mechanical parts.
[0005]
[Problems to be solved by the invention]
In the heat conductive coating and the method for forming the same, the matrix component of the coating is a resin, and at the manufacturing site of a mechanical component, the carbon nano material is oriented in a direction parallel to the member surface, and has excellent thermal conductivity in a direction parallel to the member surface. It is an object to provide a coating and a method for forming the coating.
[0006]
[Means for Solving the Problems]
Carbon nanomaterials are fibers composed of carbon atoms, having a very fine size of nanometers, a large aspect ratio (ratio of length to width), and a very high thermal conductivity. For example, carbon nanotubes are hollow and have a vertical fiber diameter of 0.5 to 10 nm and a horizontal fiber length of 0.01 to 10 μm, and carbon nanofibers have a vertical fiber diameter of 15 to 200 nm and a horizontal direction. Has a fiber length of 0.01 to 30 μm.
In the present invention, a mixed (composite) powder of a carbon nanomaterial and a resin is uniformly mixed using a mixer / kneader, and then finely divided. Gas or thermal spraying. The mixed powder is heated by spraying to form droplets, and the droplets are accelerated and collide with the member surface. Since the droplet has a very large momentum, the droplet deforms flatly from the collision site, flows while spreading rapidly in the radial direction, and adheres to the member surface to form a coating. With the flow of the molten resin, the horizontally long part of the carbon nanomaterial in the droplet is oriented in the direction parallel to the member surface, and as a result, an anisotropic heat conductive film with excellent heat conductivity in the direction parallel to the member surface is formed. It is formed. Then, the degree of parallelism of the carbon nanotubes is adjusted by changing the magnitude of the momentum of the droplet.
[0007]
When the content of the carbon nanomaterial in the mixed powder is less than 2% by volume, the thermal conductivity is poor, and when the content is more than 50% by volume, the adhesion of the coating is poor. Preferably, it is 50% by volume. In addition, in order to prevent heat conduction from the heat conductive film to the member, an undercoat film may be formed between the heat conductive film and the member by spraying a material having low heat conductivity such as a resin. Further, a coating made of a material such as a resin may be formed on the thermal conductive coating in order to improve the functions of the surface of the thermal conductive coating such as abrasion resistance and scratch resistance. The member coated with the heat conductive coating of the present invention can be used as a quick conductive part for a product for heating and a product for heat radiation.
[0008]
The present invention provides a heat conductive coating formed from a mixture of a carbon nanomaterial and a matrix component, and a method for forming the same.
The carbon nanomaterial is at least one selected from carbon nanotubes and carbon nanofibers, the matrix component is a resin, and the mixed powder is sprayed on the surface of the member from a vertical direction to form a coating. A first configuration is an anisotropic heat conductive coating in which is oriented in a direction parallel to the member surface and a method for forming the same. Here, "the horizontally elongated portion of the carbon nanomaterial is oriented in the direction parallel to the member surface" means that the extremely long horizontally elongated portion of the carbon nanomaterial having a large aspect ratio is arranged in a direction substantially parallel to the member surface. Means
According to the present invention, in the first configuration, the thermal spraying is performed by gas flame spraying or plasma spraying, and the resin is selected from nylon, polyethylene, polypropylene, a thermoplastic resin including a fluororesin, and a thermosetting resin including an epoxy resin. This is the second configuration.
According to a third aspect of the present invention, in the first and second aspects, the content of the carbon nanomaterial in the mixed powder is set to 2 to 50% by volume.
[0009]
【Example】
As shown in FIG. 1 (a), a mixed (composite) powder composed of 70% by volume of polyethylene and 30% by volume of carbon nanotubes is sprayed by a gas flame spraying method, and heat is sprayed on the surface of a member 1 made of polypropylene. A conductive coating 2 was formed. Here, the dimensions of the member are 30 mm × 30 mm × 150 mm, the dimensions of the heat conductive film are 30 mm × 150 mm, and the thickness of the thermally sprayed heat conductive film is 1.5 mm. The substrate preheating temperature is 70 ° C.
[0010]
As shown in FIG. 1B, the member 1 coated with the heat conductive film 2 is placed vertically on the upper surface of the heater 3 having an upper surface temperature of 50 ° C., and is separated from the upper surface of the heater 3 by 80 mm. The change with time of the surface temperature of the thermally conductive film 2 at the point A was determined. The temperature before the test of the member 1 and the heat conductive coating 2 is 10 ° C. As shown in the test results of FIG. 1C, it was confirmed that the example of the present invention was very excellent in thermal conductivity in the direction parallel to the surface of the member 1.
[0011]
As Comparative Example 1, a member having a sprayed coating formed under the same film forming conditions as in the example was prepared except that a powder composed of only polyethylene was used without containing carbon nanotubes. Was done. Also, as Comparative Example 2, a member having a sprayed coating formed under the same film forming conditions as in the example was prepared, except that a powder composed of only polypropylene was used without containing carbon nanotubes. Was tested. As shown in FIG. 1 (c), the test results of Comparative Examples 1 and 2 did not show a temperature rise 30 seconds after point A.
[0012]
【The invention's effect】
The anisotropic heat conductive coating of the present invention in which the horizontally long portions of the carbon nano material are oriented in the direction parallel to the member surface, the heat conductivity in the direction parallel to the member surface is superior to the heat conductivity in the thickness direction of the member. I have. The anisotropic heat conductive coating is a resin having a high matrix component of the coating, and can be manufactured using equipment at a manufacturing site for mechanical parts.
[Brief description of the drawings]
1 shows an embodiment of the present invention and a test thereof, FIG. 1 (a) is a diagram showing an outline of the embodiment of the present invention, and FIG. 1 (b) is a diagram showing a test method. FIG. 1C shows the measurement result of the temperature of the surface of the test piece at the point A.

Claims (3)

Mixing a carbon nanomaterial and a matrix component, in a heat conductive coating formed from the mixture and a method for forming the same,
The carbon nanomaterial is at least one selected from carbon nanotubes and carbon nanofibers, the matrix component is a resin, and the mixed powder is sprayed on the surface of the member from a vertical direction to form a coating. Anisotropically heat-conductive coating in which is oriented in a direction parallel to the surface of the member, and a method for forming the same. The anisotropic material according to claim 1, wherein the thermal spraying is gas flame thermal spraying or plasma thermal spraying, and the resin is one selected from nylon, polyethylene, polypropylene, a thermoplastic resin containing a fluorine resin, and a thermosetting resin containing an epoxy resin. Thermal conductive film and method for forming the same. The anisotropic heat conductive coating according to claim 1 or 2, wherein the content of the carbon nanomaterial in the mixed powder is 2 to 50% by volume.

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