JP6165603B2 - Elastomer molded body and method for producing the same - Google Patents

Description

  The present invention relates to an elastomer molded body having high thermal conductivity and a method for producing the same.

  An electronic component that generates heat, such as a CPU (Central Processing Unit), is used for the electronic device. If the heat generation of the electronic component is increased, there is a risk of causing malfunction or shortening of the product life. Accordingly, in order to suppress the temperature rise of the electronic component, a heat sink made of copper or aluminum having a high thermal conductivity is used. At this time, a heat transfer member is interposed between the electronic component and the heat sink in order to efficiently transfer heat generated in the electronic component to the heat sink. Heat generated in the electronic component is released from the heat dissipation surface of the heat sink via the heat transfer member. For example, as disclosed in Patent Documents 1 to 5, as the heat transfer member, a molded body in which a thermally conductive filler is blended in a matrix made of a polymer material is used.

JP 2003-321554 A JP 2009-51148 A JP 2013-79371 A JP 2011-225833 A JP 2012-238819 A

Yukihiro Nishikawa, “Analysis of Fiber Orientation of Fiber-Polymer Composites Using X-ray CT”, Film Forming / Processing and Troubleshooting -Process Improvement / Conditions Handbook-, Technical Information Association, Inc., 2012, p . 192-197 Yukihiro Nishikawa and three others, “Application of High Contrast X-ray CT to Polymer Carbon Fiber Composite Materials”, Journal of the Society of Materials Science, Japan, January 2011, Vol. 60, No. 1, p. 29-34

  As described in Patent Document 1, particles having high thermal conductivity such as graphite may be blended in order to improve the heat dissipation of the molded body. However, even if graphite is simply blended, it is difficult to form a heat transfer path by bringing graphite into contact with each other. For example, when a large amount of graphite is blended to form a heat transfer path, the hardness of the molded body is increased and the elongation is decreased, so that flexibility may be impaired. Moreover, the problem that the mass of a molded object increases and cost increases also arises. Graphite has a hexagonal layered structure. For this reason, the thermal conductivity in the crystal plane direction parallel to the layer is large, but the thermal conductivity in the stacking direction perpendicular to the crystal plane is small. Therefore, the orientation direction of graphite in the molded body greatly affects the thermal conductivity of the molded body.

  On the other hand, Patent Document 2 discloses a urethane foam molded article in which magnetic particles are blended to improve heat dissipation. When the magnetic particles are oriented in the polyurethane foam in a state of being connected to each other, a heat transfer path is formed in the orientation direction of the magnetic particles. Thereby, the heat dissipation of a urethane foam molded object improves. However, the thermal conductivity of iron and stainless steel blended as magnetic particles is smaller than that of graphite. Therefore, the effect of improving heat dissipation is not sufficient only by orienting the magnetic particles.

  In order to solve these problems, Patent Documents 3 and 4 disclose a molded body in which composite particles in which magnetic particles are bonded to the surface of heat conductive particles are blended with a base material. In the molded body, the heat conductive particles having a large thermal conductivity are oriented by utilizing the magnetic field orientation of the magnetic particles. When the oriented heat conductive particles (composite particles) are linearly connected, a heat transfer path is formed in the substrate. Thereby, the heat dissipation of a molded object can be improved.

  However, when the present inventors have further studied, in order to increase the thermal conductivity of the molded body, when the filling ratio of composite particles (volume ratio of the composite particles in the molded body) is increased, a certain filling ratio is obtained. It was found that the thermal conductivity decreased at the boundary. The reason for this is considered to be that when the filling rate of the composite particles is increased, the composite particles interfere with each other during molding and the orientation is impaired.

  The present invention has been made in view of such a situation, and provides an elastomer molded body in which the thermal conductivity is further improved by optimizing the orientation state of composite particles blended as a thermally conductive filler. Is an issue. It is another object of the present invention to provide a manufacturing method thereof.

(1) In order to solve the above-mentioned problem, the elastomer molded article of the present invention has a base material made of an elastomer and composite particles that are oriented and contained in the base material. Heat conduction anisotropic particles having anisotropy in heat conduction, and magnetic particles bonded to the surface of the heat conduction anisotropic particles by a binder, and the filling rate of the composite particles is 30% by volume or more when the volume is 100% by volume, and the orientation dispersion degree S defined by the following formula (1) of the composite particles is −0.47 to −0.5, Elastomer molded body.
S = <3 cos ² θ−1> / 2 (1)
[Θ is the angle of the normal line in the direction perpendicular to the plane of the composite particles to the heat conduction direction of the elastomer molded body. <> Represents a spatial average value. ]
The elastomer molded body of the present invention has oriented composite particles. The thermally conductive anisotropic particles forming the core of the composite particles have a large thermal conductivity. Magnetic particles are bonded to the surface of the thermally conductive anisotropic particles. The magnetic particles are oriented along the magnetic field lines in a magnetic field. Therefore, when a magnetic field is applied to the composite particles, the entire composite particles including the thermally conductive anisotropic particles are aligned along the magnetic field lines due to the magnetic field orientation of the magnetic particles. Thereby, a composite particle can be orientated in a base material. When the composite particles are oriented and connected in a linear manner, a heat transfer path is formed in the base material.

  Here, the thermally conductive anisotropic particles are particles having different thermal conductivities depending on directions. Therefore, in order to improve the thermal conductivity of the elastomer molded body, it is necessary to orient the thermally conductive anisotropic particles so as to be continuous in the direction in which the thermal conductivity is large. In the elastomer molded body of the present invention, the orientation state of the composite particles is defined by the orientation dispersion degree S. The orientation dispersion degree S is defined by the above formula (1). FIG. 1 is an explanatory diagram of the angle θ in the definition formula of the orientation dispersion degree S.

  As shown in FIG. 1, the elastomer molded body 1 has a base material 10 made of an elastomer and composite particles 11. The composite particles 11 are linearly aligned in the thickness direction of the elastomer molded body 1. The thickness direction of the elastomer molded body 1 corresponds to the heat conduction direction. The orientation direction of the composite particles 11 corresponds to the direction in which the thermal conductivity of the composite particles 11 is large. Here, the angle θ in the defining formula of the orientation dispersion degree S is defined by the normal 110 perpendicular to the surface of the composite particle 11 and the thickness direction of the elastomer molded body 1 (indicated by a one-dot chain line in FIG. 1). It becomes an angle. For example, when the thickness direction (heat conduction direction) of the elastomer molded body 1 and the orientation direction of the composite particles 11 coincide, the normal angle θ of the composite particles 11 with respect to the heat conduction direction becomes 90 °. In this case, the orientation dispersion degree S of the composite particles 11 is −0.5 as a completely oriented state. Therefore, as the orientation direction of the composite particles 11 approaches the heat conduction direction of the elastomer molded body 1, the angle θ becomes closer to 90 °, and the orientation dispersion degree S of the composite particles becomes a value close to −0.5. On the other hand, when the composite particles 11 are randomly dispersed and the orientation is lowered, S = 0 is approached. A method for calculating the orientation dispersion degree S of the composite particles 11 will be described in detail in a later embodiment.

  In the elastomer molded body of the present invention, the orientation dispersion degree S of the composite particles is −0.47 to −0.5 (including −0.47 and −0.5). That is, the orientation dispersion degree S of the composite particles is close to −0.5. For this reason, the composite particles are oriented in substantially the same direction as the heat conduction direction of the elastomer molded body. Therefore, by making the orientation direction of the composite particles coincide with the direction in which the thermal conductivity of the thermally conductive anisotropic particles is large, the thermal conductivity of the elastomer molded body can be maximized by taking advantage of the large thermal conductivity of the thermally conductive anisotropic particles. The conductivity can be increased.

  The filling rate of the composite particles is 30% by volume or more when the volume of the elastomer molded body is 100% by volume. As described above, conventionally, even if the filling rate of the composite particles is increased due to the interference between the composite particles at the time of molding, the thermal conductivity is not necessarily improved. However, in the elastomer molded body of the present invention, by aligning the orientation direction of the composite particles, interference between the composite particles during molding is suppressed. For this reason, the filling rate of the composite particles can be increased to 30% by volume or more, and the thermal conductivity can be further increased.

  Incidentally, Patent Document 5 has a resin and a plate-like or scaly filler, and the average orientation angle of the filler is 29 degrees or more with respect to the surface direction of the thermally conductive sheet, and the maximum orientation angle. Discloses a thermally conductive sheet having an angle of 65 degrees or more. However, the filler described in Patent Document 5 is not composite particles. Moreover, the heat conductive sheet is manufactured by hot press, and the filler is not oriented. The thermal conductive sheet described in Patent Document 5 is intended to ensure thermal conductivity in both the surface direction and the thickness direction. Therefore, Patent Document 5 does not have the idea of aligning the filler orientation in one direction.

(2) The method for producing an elastomer molded body according to the present invention is a method for producing the elastomer molded body according to the present invention described above, and is a thermally conductive anisotropic particle having anisotropy in heat conduction using a stirring granulator. A composite particle manufacturing process of manufacturing a composite particle powder by stirring a powder raw material containing the powder, magnetic particle powder, and binder, and the composite particle powder and the elastomer raw material. A mixed raw material preparation step for preparing a mixed raw material by mixing so that the filling rate is 30% by volume or more when the volume of the elastomer molded body is 100% by volume, and placing the mixed raw material in a mold And forming the mixed raw material in a magnetic field, and adjusting the magnetic field in the forming step, thereby adjusting the orientation dispersity S defined by the following formula (2) to −0. 47--0.5 Characterized in that in the range.
S = <3 cos ² θ−1> / 2 (2)
[Θ is the angle of the normal line in the direction perpendicular to the plane of the composite particles to the heat conduction direction of the elastomer molded body. <> Represents a spatial average value. ]
In the composite particle manufacturing process, the powder raw material containing the powder of thermally conductive anisotropic particles, the powder of magnetic particles, and the binder for bonding them is stirred at high speed using a stirring granulator. Thereby, the powder of a composite particle can be manufactured easily. According to the stirring granulation method, the thermally conductive anisotropic particles and the magnetic particles can be softly bonded by the binder. Therefore, even when the thermally conductive anisotropic particles have a shape with a large aspect ratio such as flaky shape or fibrous shape, the magnetic particles can be combined without breaking the shape. Moreover, the adhesion amount of a magnetic particle can be increased by using a binder. By adhering a large amount of magnetic particles, a desired orientation state of the composite particles can be realized even in a relatively low magnetic field having a magnetic flux density of 350 mT or less. As will be described later, for example, an electromagnet is used to form the magnetic field. If the molding can be performed in a low magnetic field, the gap between the electromagnets arranged with the molding die interposed therebetween can be increased. For this reason, the cavity of a shaping | molding die can be enlarged and the shape freedom degree of a product becomes high. Moreover, the installation cost and running cost of the electromagnet can be reduced.

  Incidentally, Patent Document 1 describes that the orientation of the graphite powder can be promoted by attaching a ferromagnetic powder to the surface of the graphite powder. Further, a mechanochemical method is mentioned as a method for mechanically fixing the particles. However, bonding with a binder is not described. For example, when the magnetic particles are attached to the surface of the thermally conductive anisotropic particles without using a binder, it is difficult to increase the amount of magnetic particles attached. That is, in the composite particles without using a binder, the amount of magnetic particles attached is small and the magnetism necessary for orientation is insufficient. For this reason, when the said particle | grain is used, a desired orientation state cannot be implement | achieved by a low magnetic field. Further, since graphite is brittle, there is also a problem that when mechanochemical treatment involving compression and shearing of particles is performed, it is easily pulverized and the shape cannot be maintained.

  In the forming step, the orientation dispersion degree S of the composite particles is set within the range of −0.47 to −0.5 by adjusting the magnetic field applied when the mixed raw material is formed (−0.47, − 0.5). For example, the composite particles can be oriented in a desired direction by adjusting how the magnetic field is applied, such as the strength of the magnetic field and on / off control. Therefore, according to the production method of the present invention, the elastomer molded body of the present invention having high thermal conductivity can be easily produced by blending the composite particles so as to have a high filling rate and aligning the orientation direction thereof. .

It is explanatory drawing of angle (theta) in the definition formula of orientation dispersion degree S. FIG. It is a perspective view of the magnetic induction molding apparatus used for manufacture of an elastomer molded object. It is sectional drawing of the same apparatus. It is a three-dimensional image of the elastomer molded product B obtained by X-ray CT measurement. 3 is an X-ray CT image of a cross section in the thickness direction of an elastomer molded body B. FIG. 3 is a mapping diagram in which only normal lines of composite particles in an elastomer molded body B are extracted. 4 is a graph showing the relationship between the filling rate of composite particles and the orientation dispersion degree S.

  Hereinafter, embodiments of the elastomer molded body and the method for producing the same according to the present invention will be described. The elastomer molded body and the method for producing the same according to the present invention are not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art are possible without departing from the spirit of the present invention. It can be implemented in the form.

<Elastomer molded body>
The elastomer molded body of the present invention has a base material composed of an elastomer and a powder of composite particles that are oriented and contained in the base material.

  The elastomer may be appropriately selected from a crosslinked rubber and a thermoplastic elastomer. The elastomer may be a solid body or a foamed body such as polyurethane foam. However, in view of the filling properties such as composite particles, a solid body having no bubbles (cells) is desirable. For example, examples of the crosslinked rubber include urethane rubber, silicone rubber, fluorine rubber, acrylic rubber, acrylonitrile butadiene rubber, and the like. Examples of the thermoplastic elastomer include various thermoplastic elastomers such as styrene, olefin, vinyl chloride, polyester, polyurethane, and polyamide.

  What is necessary is just to select the hardening method of crosslinked rubber suitably according to the kind of rubber polymer. For example, heat curing, ultraviolet curing, electron beam curing, moisture curing and the like can be mentioned. In order to orient the composite particles in a magnetic field, it is necessary to cure the elastomer while applying a magnetic field. For example, in the case of a thermosetting elastomer, the temperature of the elastomer raw material is raised and cured. However, when the temperature is high, the magnetism of the magnet that forms the magnetic field is reduced, which may weaken the magnetic field. For this reason, the curing temperature of the elastomer is desirably 150 ° C. or lower. In order to orient the composite particles in a low magnetic field, the viscosity of the elastomer is desirably 100 Pa · s or less. When the viscosity of the elastomer is high, the composite particles may not be easily oriented due to the influence of viscous resistance. If the elastomer has a high viscosity, it may be diluted with a solvent to lower the viscosity, and the solvent may be volatilized during curing. From the viewpoint that liquefaction and low viscosity can be achieved without using a solvent, the elastomer is preferably urethane rubber, silicone rubber, or fluororubber.

  The composite particles include heat conduction anisotropic particles having anisotropy in heat conduction, and magnetic particles bonded to the surface of the heat conduction anisotropic particles by a binder.

  As the thermally conductive anisotropic particles, particles having a high thermal conductivity are desirable. The thermal conductivity in at least one direction of the thermally conductive anisotropic particles is desirably 200 W / m · K or more. The thermally conductive anisotropic particles may be non-magnetic particles. In the present specification, diamagnetic materials and paramagnetic materials other than ferromagnetic materials and antiferromagnetic materials are referred to as nonmagnetic materials. Examples of thermally conductive anisotropic particles include scaly graphite particles, carbon fibers, and boron nitride particles. As the heat conduction anisotropic particles, one kind of particles may be used or two or more kinds of particles may be used in combination.

  The shape of the thermally conductive anisotropic particles may be flaky or fibrous. For example, as graphite, natural graphite such as scaly graphite, scaly graphite, earthy graphite, artificial graphite, and the like can be given. Artificial graphite is not easily scaled. For this reason, natural graphite is preferred because it is scaly and has a high effect of improving thermal conductivity. Further, as the graphite, expanded graphite in which a substance that generates gas by heating is inserted between scaly graphite layers may be used. Expanded graphite is often used as a flame retardant. When heat is applied to expanded graphite, the generated gas expands the layers and forms a stable layer against heat and chemicals. The formed layer becomes a heat-insulating layer and prevents heat transfer, thereby providing a flame retardant effect. Therefore, it is preferable to use at least one of natural graphite particles and expanded graphite particles as the thermally conductive anisotropic particles.

  In the elastomer molded body of the present invention, the composite particles are oriented. For this reason, the heat applied to the elastomer molded body is easily transferred to the thermally conductive anisotropic particles. Therefore, when the thermally conductive anisotropic particles are made of expanded graphite, the expanded graphite reaches the expansion start temperature earlier. Thereby, the flame-retardant effect by expanded graphite is exhibited rapidly. Thus, flame retardance can be imparted to the elastomer molded body by using expanded graphite as the thermally conductive anisotropic particles.

  When expanded graphite is used as the thermally conductive anisotropic particles, a suitable one may be selected from known expanded graphite powder in consideration of the expansion start temperature, the expansion rate, and the like. For example, the expansion start temperature of expanded graphite must be higher than the temperature at the time of molding the elastomer molded body. Specifically, expanded graphite having an expansion start temperature of 150 ° C. or higher is suitable.

The magnetic particles only need to have excellent magnetization characteristics. For example, ferromagnetic materials such as iron, nickel, cobalt, gadolinium, stainless steel, magnetite, maghemite, manganese zinc ferrite, barium ferrite, strontium ferrite, MnO, Cr Antiferromagnetic materials such as ₂ O ₃ , FeCl ₂ , and MnAs, and alloys particles using these are preferable. Among these, iron, nickel, cobalt, and powders of these iron-based alloys (including stainless steel) are preferable from the viewpoint of easy availability as fine particles and high saturation magnetization.

  The magnetic particles are bonded to the surface of the thermally conductive anisotropic particles and play a role of orienting the thermally conductive anisotropic particles. The magnetic particles may be directly bonded to the surface of the thermally conductive anisotropic particles. As described later, when particles other than the magnetic particles are bonded to the surface of the thermally conductive anisotropic particles, the magnetic particles You may adhere | attach indirectly through particle | grains. Further, the magnetic particles may be adhered to only a part of the surface of the thermally conductive anisotropic particles or the like, or may be adhered so as to cover the entire surface. The size of the magnetic particles may be appropriately determined in consideration of the size of the thermally conductive anisotropic particles, the orientation of the composite particles, the thermal conductivity between the composite particles, and the like. For example, the particle diameter of the magnetic particles is desirably 1/25 or more and 1/2 or less of the particle diameter of the thermally conductive anisotropic particles. Here, the particle diameter is the length of the longest part of the particle. When the size of the magnetic particles is reduced, the saturation magnetization of the magnetic particles tends to decrease. Therefore, in order to orient the composite particles with a smaller amount of magnetic particles, the average particle size of the magnetic particles to be combined needs to be 100 nm or more. It is more preferable that the thickness is 1 μm or more, further 5 μm or more.

  The shape of the magnetic particles is not particularly limited. For example, when the shape of the magnetic particle is flat, the distance between adjacent heat conductive anisotropic particles is shorter than that of a spherical shape. Thereby, the thermal conductivity between adjacent composite particles is improved. As a result, the thermal conductivity of the elastomer molded body is improved. When the shape of the magnetic particles is flat, the magnetic particles and the thermally conductive anisotropic particles are in contact with each other. That is, the contact area between the two becomes large. Thereby, the adhesive force of a magnetic particle and a heat conductive anisotropic particle improves. Therefore, the magnetic particles are difficult to peel off. In addition, the thermal conductivity between the magnetic particles and the thermally conductive anisotropic particles is also improved. For these reasons, it is desirable to employ flaky particles as the magnetic particles.

  In heat dissipation applications for electronic parts, etc., the elastomer molded body of the present invention may be required to have insulating properties. For example, conduction between the composite particles can be interrupted by adhering insulating inorganic particles in addition to magnetic particles to the surface of the thermally conductive anisotropic particles. When the insulating inorganic particles are bonded to the surface of the thermally conductive anisotropic particles, even if the composite particles are oriented in contact with each other, the thermally conductive anisotropic particles and magnetic particles ( It becomes difficult for the conductive particles) to come into contact with each other. Therefore, the electrical resistance between the composite particles increases. Moreover, the conduction | electrical_connection between composite particles can be interrupted when composite particles contact via an insulating inorganic particle. Thereby, in the elastomer molded object of this invention, electrical insulation can be implement | achieved.

  The insulating inorganic particles may be particles of an inorganic material having insulating properties. Among these, those having relatively high thermal conductivity are desirable from the viewpoint of not inhibiting the thermal conductivity between the composite particles. For example, it is preferable that the thermal conductivity of the insulating inorganic particles is 5 W / m · K or more. Examples of the insulating inorganic material having a thermal conductivity of 5 W / m · K or more include aluminum hydroxide, aluminum oxide (alumina), magnesium hydroxide, magnesium oxide, and talc. Further, when the insulating inorganic particles have flame retardancy, flame retardancy can be imparted to the elastomer molded body. For example, aluminum hydroxide is suitable because of its relatively high thermal conductivity and flame retardancy. Aluminum hydroxide is dehydrated and decomposed when heated to a predetermined temperature. Since dehydration decomposition is an endothermic reaction, temperature rise is suppressed and a flame retardant effect is brought about.

  The insulating inorganic particles may be directly bonded to the surface of the thermally conductive anisotropic particles, or may be indirectly bonded via magnetic particles. The insulating inorganic particles may be adhered to only a part of the surface of the thermally conductive anisotropic particles or the like, or may be adhered so as to cover the entire surface. From the viewpoint of increasing the electrical resistance between the composite particles and improving the electrical insulation of the elastomer molded body, it is desirable that the insulating inorganic particles are disposed on the outermost layer of the composite particles.

  The size of the insulating inorganic particles may be appropriately determined in consideration of the adhesion to the thermally conductive anisotropic particles and the magnetic particles, the electrical insulation between the composite particles, and the thermal conductivity. If the insulating inorganic particles are too large, the adhesiveness and the thermal conductivity between the composite particles are lowered. For example, the particle diameter of the insulating inorganic particles is desirably 1/100 or more and 1/10 or less of the particle diameter of the thermally conductive anisotropic particles. Here, the particle diameter is the length of the longest part of the particle.

  The shape of the insulating inorganic particles is not particularly limited. For example, when the shape of the insulating inorganic particles is flat, the distance between adjacent thermally conductive anisotropic particles is shorter than that of a spherical shape. Thereby, the thermal conductivity between adjacent composite particles is improved. As a result, the thermal conductivity of the elastomer molded body is improved. Further, the contact area between the insulating inorganic particles, the magnetic particles, and the thermally conductive anisotropic particles is increased. Thereby, adhesive force improves and it becomes difficult to exfoliate insulating inorganic particles. In addition, the thermal conductivity between the insulating inorganic particles, the magnetic particles, and the thermally conductive anisotropic particles is also improved. For these reasons, it is desirable to employ flaky particles as the insulating inorganic particles.

  The binder for bonding the thermally conductive anisotropic particles and the magnetic particles and the like may be appropriately selected in consideration of the type of thermally conductive anisotropic particles and the like, the influence on the moldability, and the like. A water-soluble binder is preferable because it has little influence on moldability and is environmentally friendly. For example, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol and the like can be mentioned. The binder that adheres the magnetic particles and the binder that adheres the insulating inorganic particles may be the same or different.

  The composite particles can be produced, for example, by spraying a coating material in which a magnetic particle powder or the like is dispersed in a solution in which a binder is dissolved, onto the heat conductive anisotropic particle powder. Moreover, the powder raw material containing the heat conductive anisotropic particle powder, the magnetic particle powder, and the binder can be produced by stirring at high speed (stir granulation method). In the stirring granulation method, frictional heat is generated by high-speed stirring. For this reason, as a binder, a non-volatile thing is desirable. For example, the water-soluble binder described above is suitable.

  The filling rate of the composite particles in the elastomer molded body of the present invention is 30% by volume or more when the volume of the elastomer molded body is 100% by volume. The upper limit value of the filling rate of the composite particles is not particularly limited, but from the viewpoint of reducing the influence on moldability and physical properties, the filling rate of the composite particles is 60 when the volume of the elastomer molded body is 100% by volume. It is desirable to make it volume% or less.

  For example, as a powder of composite particles, a mixed powder in which a small particle size powder and a large particle size powder are mixed, in other words, a powder having two peaks of a small particle size side peak and a large particle size side peak in the particle size distribution. When used, it is effective for improving thermal conductivity. In the present specification, a volume-based frequency distribution of particles is adopted as the particle size distribution. When the mixed powder is used, the small particle diameter particles are arranged so as to fill the gap (base material portion) between the large particle diameter particles and the large particle diameter particles. Therefore, even if the filling rate of the composite particles is increased, the composite particles are unlikely to interfere with each other and the orientation is not easily impaired.

  In the mixed powder, the difference between the peak particle size of the small particle size side peak and the peak particle size of the large particle size side peak is desirably relatively large. For example, the peak particle size of the large particle size side peak is preferably at least twice the peak particle size of the small particle size side peak. It is more preferable that it is 5 times or more. On the other hand, if the difference in peak particle size is too large, the effect of improving the thermal conductivity is reduced, so the peak particle size of the large particle size side peak is preferably 20 times or less than the peak particle size of the small particle size side peak. . It is more preferable that it is 15 times or less. In summary, in the two peaks, the ratio between the peak particle size of the small particle size side peak and the peak particle size of the large particle size side peak is preferably 1: 2 to 1:20, and is preferably 1: 5 to 1. : 15 is more preferable. Further, in order to enhance the effect of improving the thermal conductivity even if the packing rate of the composite particles is relatively low, the large particle size powder is blended at a mass ratio equal to or greater than the small particle size powder. It is desirable. For example, the mass ratio between the small particle size powder and the large particle size powder is desirably 1: 1 to 1:10. In the particle size distribution of the composite particle powder, the ratio of the area of the small particle size side peak to the area of the large particle size side peak is preferably 1: 1 to 1:30. A ratio of 1: 5 to 1:20 is more preferable.

  The degree of orientation dispersion of the composite particles in the elastomer molded body of the present invention is -0.47 to -0.5. Below, the calculation method of the orientation dispersion degree of a composite particle is demonstrated.

  First, an elastomer molded body is imaged using an X-ray CT (Computerized Tomography) apparatus, and the obtained tomographic image data is subjected to a reconstruction operation to produce a three-dimensional image including the inside of the elastomer molded body. Next, the degree of orientation dispersion S is calculated using software in which the orientation analysis method described in Non-Patent Document 1 is modified for the composite particles of the present invention. Specifically, the produced three-dimensional image is divided into a grid pattern, and Fourier transform is performed for each divided region to obtain a tensor (third-order symmetric matrix) of the Fourier transform intensity image. The obtained tensor is diagonalized, and the eigenvector corresponding to the largest eigenvalue is set as the normal of the composite particle in the region. In this way, the normal of the composite particles in the direction perpendicular to the plane is calculated for each region. Then, the orientation dispersion degree S of the composite particles is calculated by the above-described equation (1) using the angle θ of the normal of the composite particles with respect to the heat conduction direction of the elastomer molded body (for example, the thickness direction of the elastomer molded body). To do. Finally, the arithmetic average of the orientation dispersion degree S calculated for each region is calculated, and the obtained average value is used as the orientation dispersion degree S of the composite particles in the elastomer molded body.

  The thermal conductivity of the elastomer molded body of the present invention is preferably 3.0 W / m · K or more from the viewpoint of realizing high thermal conductivity. What is necessary is just to measure thermal conductivity according to the heat flow meter method of JIS A1412-2 (1999).

  In addition to the composite particle powder, the elastomer molded body of the present invention may further include a non-oriented filler that is dispersed in the substrate without being oriented. The non-oriented filler may be appropriately selected according to the purpose such as improvement of thermal conductivity, provision of insulation, improvement of flame retardancy, and the like. As the non-oriented filler, in addition to the above-described thermally conductive anisotropic particles and insulating inorganic particles, thermally conductive isotropic particles having no directionality in heat conduction can be dispersed. When blending a non-oriented filler, it is desirable to use particles having a small particle size so as not to hinder the orientation of the composite particles. For example, a powder having an average particle size of 0.1 μm or more and 20 μm or less is suitable.

<Method for producing elastomer molded article>
The method for producing an elastomer molded body of the present invention is a production method for producing composite particles by agitation granulation method, and includes a composite particle production step, a mixed raw material preparation step, and a molding step. Hereinafter, each step will be described.

(1) Composite particle manufacturing process This process stirs the powder raw material containing the heat conductive anisotropic particle powder, the magnetic particle powder, and the binder having anisotropy in heat conduction using an agitation granulator. This is a process for producing a powder of composite particles.

  The thermally conductive anisotropic particles, magnetic particles, and binder are as described above. Therefore, the description is omitted here. In addition, regarding the amount of thermally conductive anisotropic particle powder, magnetic particle powder, and binder, the magnetic field orientation of the produced composite particles, the thermal conductivity of the elastomer molded body containing the composite particles, and the like are considered. And may be adjusted as appropriate.

  For example, when graphite is employed as the thermally conductive anisotropic particles, the blending amount of the magnetic particle powder is desirably 20 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the graphite powder. When the amount is less than 20 parts by mass, the amount of adhesion of the magnetic particles is small, so that the magnetism necessary for the orientation of the composite particles may be insufficient. On the other hand, if it exceeds 150 parts by mass, the adhesion amount of the magnetic particles becomes excessive. Accordingly, an increase in the mass of the elastomer molded body and an increase in cost are incurred accordingly.

  The blending amount of the binder is preferably 2% by mass or more and 4% by mass or less, assuming that the total mass of the powder to be bonded is 100% by mass as a necessary and sufficient amount for coating the particles to be bonded. When the blending amount of the binder is less than 2% by mass, the binder does not reach the surface of the thermally conductive anisotropic particles or magnetic particles, and the adhesiveness decreases. On the other hand, when it exceeds 4 mass%, there exists a possibility that composite particles may aggregate with an excess binder. The binder may be solid or liquid. When water-soluble powder is used as the binder, it is preferable to add water after previously stirring the binder and the powder of other raw materials. By doing so, aggregation of particles can be suppressed.

  When the insulating inorganic particles are combined in addition to the magnetic particles, both powders may be stirred together to adhere to the thermally conductive anisotropic particles. Then, the insulating inorganic particles may be bonded after the bonding. In this case, the present process includes the first stirring step of stirring the first powder raw material containing the heat conductive anisotropic particle powder, the magnetic particle powder, and the binder; It is good to comprise so that it may have and the 2nd stirring process of stirring further.

(2) Mixed raw material preparation step In this step, the composite particle powder and the elastomer raw material produced in the previous step are used, and the filling rate of the composite particles in the elastomer molded body is 100% by volume of the elastomer molded body. This is a step of preparing a mixed raw material by mixing so as to be 30% by volume or more.

  In addition to the polymer of the elastomer component (in the case where the elastomer is a crosslinked rubber, the elastomer raw material), if necessary, a crosslinking agent, a plasticizer, a catalyst, a foaming agent, a foam stabilizer, a flame retardant, a charge Contains inhibitors, thickeners, stabilizers, fillers, colorants and the like. The mixed raw material may be produced by stirring the composite particle powder and the elastomer raw material using a stirring blade or the like. In the case of using a powder having two peaks of a small particle size side peak and a large particle size side peak in the particle size distribution as the composite particle, the powder of the composite particle is sieved in advance and classified by a dry classifier or the like. A particle size powder and a large particle size powder may be prepared.

  For example, when the elastomer raw material is a foamed urethane raw material, the composite particle powder may be blended in advance with at least one of the polyol raw material and the polyisocyanate raw material. Moreover, you may employ | adopt the collision stirring method which mixes a polyol raw material and a polyisocyanate raw material by injecting and colliding each at high pressure.

  As described above, in the elastomer molded body of the present invention, non-oriented fillers may be dispersed in the base material separately from the composite particles. When an elastomer molded body of this form is manufactured, the powder of composite particles and the non-oriented filler may be mixed with the elastomer raw material.

(3) Molding step This step is a step of placing the mixed raw material prepared in the previous step in a mold and molding the mixed raw material in a magnetic field. In this step, the orientation dispersion degree S of the composite particles is set in the range of −0.47 to −0.5 by adjusting the magnetic field applied during molding.

  The mold may be a closed mold or an open mold. The magnetic field may be formed in the direction in which the composite particles are oriented. For example, when orienting composite particles in a straight line, it is desirable to apply magnetic lines of force from one end of the mixed raw material to the other end. In order to form such a magnetic field, a magnet may be disposed so as to sandwich the mixed raw material. A permanent magnet or an electromagnet may be used as the magnet. When an electromagnet is used, magnetic field formation can be switched on and off instantaneously, and the control of the magnetic field strength is easy. Therefore, it is easy to orient the composite particles so that the orientation dispersion degree S is in the range of −0.47 to −0.5.

  Moreover, it is desirable that the magnetic field lines constituting the magnetic field form a closed loop. By doing so, leakage of the magnetic field lines is suppressed, and a stable magnetic field can be applied to the mixed raw material. In order to form a magnetic field inside the mold by using a magnet arranged outside the mold, the mold may be made of a material having low magnetic permeability, that is, a non-magnetic material. For example, a mold made of aluminum or aluminum alloy is suitable. In this case, the magnetic field and magnetic lines generated from a magnetic source such as an electromagnet are not easily affected, and the magnetic field state is easily controlled. However, a mold made of a magnetic material may be used as appropriate according to the required magnetic field and magnetic field lines.

  In this step, it is desirable to apply a magnetic field having a substantially uniform magnetic flux density to the mixed raw material. Specifically, the difference in magnetic flux density between the mixed raw materials is preferably within ± 10%. It is more preferable that it is within ± 5%, more preferably within ± 3%. By applying a uniform magnetic field to the mixed raw material, uneven distribution of the composite particles can be suppressed, and a desired orientation state can be obtained. Moreover, it is good to perform shaping | molding with the magnetic flux density of 150 mT or more and 350 mT or less. By carrying out like this, the composite particle in a mixed raw material can be orientated reliably. After molding is completed in this step, the mold is removed to obtain the elastomer molded body of the present invention.

  Next, the present invention will be described more specifically with reference to examples.

<Production of composite particles>
First, two types of scaly graphite powders (“W + 32” (+32 mesh 80% or more) and “X-100” (average particle size 60 μm) manufactured by Ito Graphite Industries Co., Ltd.) as magnetically conductive anisotropic particles and magnetic properties Stainless steel powder (SUS410L, flakes, average particle size 20 μm) as particles and hydroxypropylmethylcellulose (HPMC, “TC-5” manufactured by Shin-Etsu Chemical Co., Ltd.) as a binder were prepared. The flaky stainless steel powder was produced by flattening a spherical stainless steel powder (“DAP410L” manufactured by Daido Steel Co., Ltd., average particle size: 10 μm). That is, a spherical stainless steel powder was filled in a planetary ball mill (“Planet-M” manufactured by Gokin Planetaring) together with zirconia balls having a diameter of 5 mm, and processed at a rotational speed of 300 rpm for 1 hour.

  Next, 1418 g of scaly graphite powder “W + 32”, 532 g of stainless steel powder, and 43 g of HPMC were put into a container of FM mixer (manufactured by Nippon Coke Industries Co., Ltd.) and mixed for 1 minute. Thereafter, 135 g of water was added and further mixed for 6 minutes to produce composite particle powder. After the produced composite particle powder was dried, it was sieved with two types of sieves having an opening of 1100 μm and 700 μm to obtain a large particle size powder having a particle size of 700 μm to 1100 μm.

  A powder of composite particles was produced in the same manner as described above except that the scaly graphite powder was replaced with “X-100”. After the produced composite particle powder was dried, it was sieved with two types of sieves having openings of 100 μm and 45 μm to obtain a small particle size powder having a particle size of 45 μm or more and 100 μm or less.

  The mass ratio of the flaky graphite powder and the stainless steel powder blended is 100: 37.5. The blending amount of HPMC is 2.2% by mass when the total mass of the scaly graphite powder and the stainless steel powder is 100% by mass.

<Preparation of mixed powder>
A mixed powder is prepared by mixing 100 g of a small particle size powder produced using a flaky graphite powder “X-100” and 400 g of a large particle size powder produced using a “W + 32” flaky graphite powder. (The mass ratio of the small particle size powder to the large particle size powder was 1: 4). The particle size distribution of the prepared mixed powder was measured with a laser diffraction / scattering type particle size distribution measuring device (“MT-3300EX” manufactured by Nikkiso Co., Ltd.). It was confirmed to have two peaks of the particle size side peak. The peak particle size of the small particle size side peak was 90 μm, the peak particle size of the large particle size side peak was 900 μm, and the ratio of both peak particle sizes was 1:10. Further, when the particle size distribution was divided into two at 270 μm and the respective peak areas on the small particle size side and the large particle size side were calculated, the area ratio between the small particle size side peak and the large particle size side peak was 1:10.

[Mixed powder A]
The prepared mixed powder was weighed so that the filling rate of the composite particles was 33% by volume when the volume of the elastomer molded body to be produced was 100% by volume, and mixed powder A was obtained.

[Mixed powder B]
The prepared mixed powder was weighed so that the filling rate of the composite particles was 36% by volume when the volume of the elastomer molded body to be produced was 100% by volume, and mixed powder B was obtained.

[Mixed powder C]
The prepared mixed powder was weighed so that the filling rate of the composite particles was 26% by volume when the volume of the elastomer molded body to be produced was 100% by volume, and mixed powder C was obtained.

[Mixed powder D]
The prepared mixed powder was weighed so that the filling rate of the composite particles would be 40% by volume when the volume of the elastomer molded body to be produced was 100% by volume.

<Manufacture of elastomer moldings>
An elastomer molded body was manufactured using the weighed mixed powders A to D. First, 100 parts by mass of vinyl group-containing dimethylpolysiloxane (“DMS-V41” manufactured by Gelest) of liquid silicone rubber and 3 parts by mass of hydrosilyl group-containing dimethylpolysiloxane (“HMS-082” manufactured by Gelest) of a crosslinking agent, , 1 part of 1-ethynyl-1-cyclohexanol as a retarder and 0.05 part by weight of platinum catalyst (“SIP6830.3” manufactured by Gelest) were stirred for 15 minutes using a stirring blade, Created a compound.

  Next, mixed powders A to D were mixed with the manufactured silicone compound to prepare mixed raw materials. Subsequently, each of the mixed raw materials is poured into an aluminum mold (see FIGS. 2 and 3 to be described later. The cavity is a rectangular parallelepiped having a length of 130 mm × width of 130 mm × thickness of 5 mm). , Sealed. And the shaping | molding die was installed in the magnetic induction molding apparatus, and it shape | molded. FIG. 2 shows a perspective view of the magnetic induction molding apparatus. FIG. 3 shows a sectional view of the apparatus. In FIG. 2, hatching of the yoke part and the core part is omitted for convenience of explanation. As shown in FIGS. 2 and 3, the magnetic induction molding apparatus 2 includes a gantry 3, an electromagnet unit 4, a molding die 5, a planar heater 60, and a heat insulating member 61.

  The electromagnet unit 4 is placed on the upper surface of the gantry 3. The electromagnet portion 4 and the gantry 3 are fixed by screwing a bracket 31 to each. The electromagnet portion 4 includes yoke portions 40U and 40D, coil portions 41L and 41R, and pole pieces 42U and 42D.

  The yoke part 40U is made of iron and has a flat plate shape. Similarly, the yoke part 40D is made of iron and has a flat plate shape. The yoke portions 40U and 40D are arranged to face each other in the vertical direction.

  The coil portion 41L is interposed between the yoke portions 40U and 40D. The coil portion 41L is disposed on the left side of the mold 5. Two coil portions 41L are arranged in the vertical direction. Each of the coil parts 41L includes a core part 410L and a conducting wire 411L. The core 410L is made of iron and has a columnar shape extending in the vertical direction. The conducting wire 411L is wound around the outer peripheral surface of the core portion 410L. The conducting wire 411L is connected to a power source (not shown).

  The coil portion 41R is interposed between the yoke portions 40U and 40D. The coil portion 41 </ b> R is disposed on the right side of the mold 5. Two coil portions 41R are arranged in the vertical direction. The coil portions 41R each have the same configuration as the coil portion 41L. That is, the coil portion 41R includes a core portion 410R and a conductive wire 411R. The conducting wire 411R is wound around the outer peripheral surface of the core portion 410R. The conducting wire 411R is connected to a power source (not shown).

  The pole piece 42U is made of iron and has a flat plate shape. The pole piece 42U is disposed at the center of the lower surface of the yoke portion 40U. The pole piece 42U is interposed between the yoke portion 40U and the mold 5. The pole piece 42D is made of iron and has a flat plate shape. The pole piece 42D is disposed at the center of the upper surface of the yoke portion 40D.

  The forming die 5 is disposed between the coil portion 41L and the coil portion 41R. The mold 5 includes an upper mold 50U and a lower mold 50D. The upper mold 50U has a square plate shape. The lower mold 50D has a rectangular parallelepiped shape. A recess is formed on the upper surface of the lower mold 50D. The recess has a rectangular parallelepiped shape that opens upward. By combining the upper mold 50U and the lower mold 50D, a rectangular parallelepiped cavity 51 is defined. As described above, the cavity 51 is filled with the mixed raw material.

  The planar heater 60 has a square sheet shape. The planar heater 60 is disposed so as to cover the lower surface of the lower mold 50D. The mold 5 is held at 100 ° C. by the planar heater 60.

  The heat insulating member 61 is made of glass fiber and has a flat plate shape. The heat insulating member 61 is interposed between the planar heater 60 and the pole piece 42D. The heat transfer from the planar heater 60 to the electromagnet unit 4 is suppressed by the heat insulating member 61.

  When both the power source connected to the conducting wire 411L and the power source connected to the conducting wire 411R are turned on, the upper end of the core portion 410L of the coil portion 41L is magnetized to the N pole and the lower end is magnetized to the S pole. For this reason, a magnetic force line L (indicated by a dotted line in FIG. 3) is generated in the core portion 410L from below to above. Similarly, the upper end of the core portion 410R of the coil portion 41R is magnetized to the N pole and the lower end is magnetized to the S pole. For this reason, lines of magnetic force L are generated in the core portion 410R from below to above.

  The lines of magnetic force L radiated from the upper end of the core portion 410L of the coil portion 41L flow into the cavity 51 of the mold 5 through the yoke portion 40U and the pole piece 42U. Then, it flows into the lower end of the core part 410L through the pole piece 42D and the yoke part 40D. Similarly, the line of magnetic force L radiated from the upper end of the core portion 410R of the coil portion 41R flows into the cavity 51 of the mold 5 through the yoke portion 40U and the pole piece 42U. Then, it flows into the lower end of the core part 410R through the pole piece 42D and the yoke part 40D. Thus, since the magnetic lines L constitute a closed loop, the leakage of the magnetic lines L is suppressed. In the cavity 51 of the mold 5, a uniform magnetic field is formed by magnetic lines of force L that are substantially parallel from the top to the bottom. Specifically, the magnetic flux density in the cavity 51 was about 300 mT. Further, the difference in magnetic flux density in the cavity 51 was within ± 3%.

  Molding was performed at 100 ° C. while applying a magnetic field for 30 minutes. After the molding was completed, the mold was removed to obtain an elastomer molded body. The obtained elastomer moldings were numbered as elastomer moldings A to D in correspondence with the numbers of the mixed powders.

<Orientation analysis of composite particles in elastomer molding>
First, the produced elastomer molded bodies A to D were photographed using an X-ray CT apparatus ("FLEX-M865-CT" manufactured by Beam Sense Co., Ltd.) Photographing was performed at an acceleration voltage of 70 kV and a tube current of 100 µA. The obtained tomographic image data was reconstructed to produce a three-dimensional image including the inside of the elastomer molded body, as an example, a three-dimensional image of the elastomer molded body B is shown in FIG.

Next, the orientation dispersion degree S of the composite particles was calculated using software obtained by correcting the orientation analysis method described in Non-Patent Document 1 for the composite particles of the present invention. As described above, first, the produced three-dimensional image was divided into a grid shape, and the normal of the composite particles in the direction perpendicular to the plane was calculated for each divided region. As an example, FIG. 5 shows an X-ray CT image of a cross section in the thickness direction of the elastomer molded body B. In FIG. 5, the white straight line is the normal of the composite particle. In FIG. 6, the mapping figure which extracted only the normal line of the composite particle in the elastomer molded object B is shown. Next, using the angle [theta] of the normal of the composite particle with respect to the thickness direction (heat conduction direction) of the elastomer molded body, the orientation dispersion of the composite particle by the above formula [S = <3cos < ² > [theta] -1> / 2]. The degree S was calculated. And the arithmetic average of the orientation dispersion degree S computed for every area | region was calculated, and the obtained average value was made into the orientation dispersion degree S of the composite particle in an elastomer molded object.

<Measurement of thermal conductivity of elastomer moldings>
The thermal conductivity of the produced elastomer molded bodies A to D was measured using “HC-110” manufactured by Eihiro Seiki Co., Ltd., which conforms to the heat flow meter method of JIS A1412-2 (1999). Table 1 shows the measurement results of the orientation dispersion degree S and the thermal conductivity in the elastomer molded bodies A to D together with the filling rate of the composite particles (mixed powder). FIG. 7 is a graph showing the relationship between the filling rate of the composite particles and the orientation dispersion degree S. In FIG. 7, the range of the present invention is shown by hatching.

  As shown in Table 1 and FIG. 7, the orientation dispersity S of the elastomer molded body A in which the filling rate of the composite particles was 33% by volume was −0.49. For this reason, the thermal conductivity of the elastomer molded body A was as large as 3.7 W / m · K. Similarly, the degree of orientation dispersion S of the elastomer molded body B in which the filling rate of the composite particles was 36% by volume was −0.47. For this reason, the thermal conductivity of the elastomer molded body B was as large as 3.5 W / m · K. Elastomer molded bodies A and B are included in the elastomer molded body of the present invention.

  On the other hand, in the elastomer molded body C, the orientation dispersion degree S is −0.49, but the filling rate of the composite particles is as low as 26 volume%. For this reason, the thermal conductivity of the elastomer molded body C was as small as 2.5 W / m · K. In the elastomer molded body C, since the filling rate of the composite particles is low, the composite particles hardly interfere with each other during molding, and the composite particles are easily oriented in the direction of the lines of magnetic force (the thickness direction of the elastomer molded body). However, since the packing rate of the composite particles is low, the desired thermal conductivity could not be realized.

  Further, in the elastomer molded body D, the filling rate of the composite particles is as high as 40% by volume, but the orientation dispersion S is −0.45. For this reason, the thermal conductivity of the elastomer molded body D was as small as 2.3 W / m · K. In the elastomer molded body D, since the filling rate of the composite particles is high, the composite particles interfere with each other during molding, and it is considered that the composite particles could not be sufficiently oriented in the thickness direction of the elastomer molded body. For this reason, the large thermal conductivity in the orientation direction of the scaly graphite powder could not be utilized, and the desired thermal conductivity could not be realized.

  The elastomer molded article of the present invention can be used in a wide range of fields such as electronic equipment, automobiles, and architecture. Specifically, it is suitable for a heat radiating member used for electronic equipment such as a personal computer, a heat radiating member for an in-vehicle ECU (electronic control unit), a heat radiating member for LED (light emitting diode) illumination, and the like.

1: Elastomer molded body, 10: base material, 11: composite particles, normal: 110.
2: Magnetic induction molding device, 3: Stand, 31: Bracket, 4: Electromagnet part, 40D, 40U: Yoke part, 41L, 41R: Coil part, 42D, 42U: Pole piece, 410L, 410R: Core part, 411L, 411R: conducting wire, 5: molding die, 50U: upper die, 50D: lower die, 51: cavity, 60: planar heater, 61: heat insulating member, L: magnetic field lines.

Claims (6)

A substrate made of an elastomer, and composite particles that are oriented and contained in the substrate;
The composite particles include thermally conductive anisotropic particles having anisotropy in heat conduction, and magnetic particles bonded to the surface of the thermally conductive anisotropic particles by a binder,
The filling rate of the composite particles is 30% by volume or more when the volume of the elastomer molded body is 100% by volume,
An elastomer molded product, wherein the orientation dispersion degree S defined by the following formula (1) of the composite particles is −0.47 to −0.5.
S = <3 cos ² θ−1> / 2 (1)
[Θ is the angle of the normal line in the direction perpendicular to the plane of the composite particles to the heat conduction direction of the elastomer molded body. <> Represents a spatial average value. ]   The elastomer molded body according to claim 1, wherein the thermally conductive anisotropic particles have a flaky shape or a fibrous shape.   3. The elastomer molded body according to claim 1, wherein the thermally conductive anisotropic particles are at least one selected from scaly graphite particles, carbon fibers, and boron nitride particles.   The elastomer molded body according to any one of claims 1 to 3, wherein the thermal conductivity is 3.0 W / m · K or more.   The elastomer molded body according to any one of claims 1 to 4, wherein the elastomer is any one of urethane rubber, silicone rubber, fluororubber, and foams thereof. It is a manufacturing method of the elastomer fabrication object according to claim 1,
Production of composite particles using an agitation granulator to produce powder of composite particles by stirring powder of heat conduction anisotropic particles having anisotropy in heat conduction, powder of magnetic particles, and powder raw material containing a binder Process,
The composite particle powder and the elastomer raw material are mixed so that the filling rate of the composite particle in the elastomer molded body is 30% by volume or more when the volume of the elastomer molded body is 100% by volume, and the mixed raw material A mixed raw material preparation step to prepare
A molding step of placing the mixed raw material in a mold and molding the mixed raw material in a magnetic field;
Have
Elastomer molding characterized in that by adjusting the magnetic field in the molding step, the orientation dispersion degree S defined by the following formula (2) of the composite particles is in the range of −0.47 to −0.5. Body manufacturing method.
S = <3 cos ² θ−1> / 2 (2)
[Θ is the angle of the normal line in the direction perpendicular to the plane of the composite particles to the heat conduction direction of the elastomer molded body. <> Represents a spatial average value. ]