WO2015016221A1

WO2015016221A1 - Elastomer molded article and method for producing same

Info

Publication number: WO2015016221A1
Application number: PCT/JP2014/069952
Authority: WO
Inventors: 峻久小瀬; 宏旭中島; 竜介山岡; 鈴木　智志; 片山　直樹
Original assignee: 住友理工株式会社
Priority date: 2013-07-31
Filing date: 2014-07-29
Publication date: 2015-02-05
Also published as: JP2015030735A; JP5719887B2

Abstract

An elastomer molded article comprises: a base material comprising an elastomer; and a powder of composite particles which is contained in the base material in an oriented state. The composite particles comprise: heat-conductive particles formed from a non-magnetic material; and magnetic particles attached onto the surfaces of the heat-conductive particles by a binder. The particle size distribution of the powder of the composite particles has two peaks, i.e., a peak appearing on a smaller particle diameter side and a peak appearing on a larger particle diameter side. A method for producing an elastomer molded article comprises: a composite particle powder preparation step of producing a powder of composite particles using a stirring granulator, and then sieving the powder of the composite particles to prepare a powder having a smaller particle diameter and a powder having a larger particle diameter; a mixed raw material preparation step of mixing the powder having a smaller particle diameter and the powder having a larger particle diameter of the composite particles with an elastomer raw material to prepare a mixed raw material; and a molding step of placing the mixed raw material in a molding die to mold the mixed raw material under a magnetic field.

Description

Elastomer molded body and method for producing the same

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

For electronic equipment, electronic components with heat generation such as a CPU (Central Processing Unit) are used. 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, a molded body in which a thermally conductive filler is blended in a matrix made of a polymer material is used as the heat transfer member.

JP 2003-321554 A JP 2009-51148 A JP 2011-35221 A JP 2013-79371 A JP 2011-225833 A

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.

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 or 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

4 and 5 disclose a molded body in which composite particles in which magnetic particles are bonded to the surface of thermally 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 circumstances, and provides an elastomer molded body having further improved thermal conductivity without impairing the orientation 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 problems, an elastomer molded article of the present invention has a base material made of an elastomer, and a powder of composite particles that are oriented and contained in the base material. Includes a heat conductive particle made of a non-magnetic material and a magnetic particle bonded to the surface of the heat conductive particle with a binder, and the particle size distribution of the powder of the composite particle has a small particle size side peak and a large particle size distribution. It has two peaks of the particle size side peak.

The elastomer molded body of the present invention has a powder of oriented composite particles. The thermally conductive particles forming the core of the composite particles have a large thermal conductivity. The thermally conductive particles themselves are nonmagnetic. However, magnetic particles are adhered to the surface of the heat conductive 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 composite particles are oriented along the lines of magnetic force. That is, by compositing the thermally conductive particles and the magnetic particles, the thermally conductive particles made of a non-magnetic material can be oriented using the magnetic field orientation of the magnetic particles. In the base material, the composite particles are linearly connected, so that a heat transfer path is formed in the base material. Therefore, the thermal conductivity of the elastomer molded body of the present invention is high.

Here, the particle size distribution of the composite particle powder has two peaks, a small particle size side peak and a large particle size side peak. That is, the composite particle powder is a powder in which a small particle size powder and a large particle size powder are mixed. As the particle size distribution in the present invention, a volume-based frequency distribution of particles is employed.

The particle size distribution of the composite particle powder produced without adjusting the particle size such as classification usually has one peak. In the conventional molded body in which the powder of the composite particles is oriented, when the surface intersecting the orientation direction is observed, the composite particles and the base material can be distinguished relatively clearly as shown in Examples described later. Can do. That is, since the composite particles are arranged linearly in the orientation direction, most of the composite particles adjacent to each other in the plane direction intersecting the orientation direction is the base material.

In contrast, in the elastomer molded body of the present invention in which the powder of composite particles having a particle size distribution having two peaks, a small particle size side peak and a large particle size side peak, is oriented, a large particle size side peak is formed. The large particle size particles are aligned and connected linearly, and the small particle size particles constituting the small particle size side peak are also linearly aligned between the large particle particles adjacent to each other in the plane direction intersecting the alignment direction. It is a series. Therefore, as shown in the examples described later, when the surface intersecting the orientation direction is observed, the small particle size particles are formed so as to fill the gap (base material portion) between the large particle size particle and the large particle size particle. It can be confirmed that they are distributed. Therefore, according to the elastomer molded body of the present invention, heat transfer can be performed over the entire surface. For this reason, the thermal conductivity of the elastomer molded body can be improved without increasing the filling rate of the composite particles. In addition, since small particles having a small particle size are interposed between the large particles, 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 elastomer molded body of the present invention, the composite particles in the substrate need only be arranged in a predetermined direction with a certain regularity. For example, the elastomer molded body may be arranged in a straight line or a curved line between one end and the other end (the end may not be 180 ° opposite to the one end). Moreover, you may arrange | position radially from the center toward the outer periphery.

(2) The method for producing an elastomer molded body of the present invention is a method for producing an elastomer molded body having the above-described configuration (1) in the case where composite particles are produced by the agitation granulation method, using an agitation granulator. The powder raw material containing the heat conductive particles, the magnetic particles, and the binder is stirred to produce composite particles, and the composite particles are classified into small particles and large particles. A composite particle powder preparation step to be prepared, a mixed raw material preparation step for preparing a mixed raw material by mixing the small particle size powder and the large particle size powder of the composite particle, and an elastomer raw material, and molding the mixed raw material And a molding step of molding the mixed raw material in a magnetic field.

In the composite particle powder preparation step, first, a powder raw material containing a powder of heat conductive particles, a powder of magnetic particles, and a 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 heat conductive particles and the magnetic particles can be softly bonded with the binder. Therefore, even when the thermally conductive particles have a shape with a high thermal conductivity (a shape with a large aspect ratio), 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, the above 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 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.

Next, the produced composite particle powder is classified to prepare a small particle size powder and a large particle size powder. By dividing the composite particle powder into two types of powders having different particle size ranges, the small particle size particles can be dispersed so as to fill the gaps between the large particle size particles. Thereby, the heat conductivity of the elastomer molded body manufactured can be improved.

In the mixed raw material preparation step, the prepared small particle size powder and large particle size powder are mixed with the elastomer raw material to prepare a mixed raw material. In the molding step, the prepared mixed raw material is molded in a magnetic field. Thereby, the large particle size particles are aligned and connected in a linear manner, and the small particle size particles are also filled between the large particle particles and the large particle particles adjacent to each other in the plane direction intersecting the alignment direction. Oriented and linearly connected. Moreover, the uneven distribution of the composite particles due to the difference in magnetic flux density can be suppressed by applying a magnetic field having a substantially uniform magnetic flux density (uniform magnetic field) to the mixed raw material. Therefore, even if the filling rate of the composite particles is relatively low, the composite particles can be oriented while being dispersed throughout the substrate. Thus, according to the production method of the present invention, a relatively small amount of composite particles can be blended to easily produce the elastomer molded body of the present invention having high thermal conductivity.

2 is a particle size distribution of the mixed powder of Example 1. 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. 2 is an X-ray CT photograph of the elastomer molded body of Example 1. FIG. 3 is an X-ray CT photograph of an elastomer molded body of Comparative Example 2. It is a graph which shows the relationship between the filling rate of composite particle | grains, and thermal conductivity. It is a graph which shows the relationship between the mass ratio of small particle size powder and large particle size powder, and thermal conductivity. It is a graph which shows the measurement result of the thermal conductivity of the elastomer molded object which mix | blended the non-oriented filler.

1: Magnetic induction molding device, 2: Stand, 21: Bracket, 3: Electromagnet part, 30D, 30U: Yoke part, 31L, 31R: Coil part, 32D, 32U: Pole piece, 310L, 310R: Core part, 311L, 311R: Conductor, 4: Mold, 40U: Upper mold, 40D: Lower mold, 41: Cavity, 50: Planar heater, 51: Thermal insulation member, L: Magnetic field line.

Hereinafter, embodiments of the elastomer molded body and the manufacturing method thereof 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.

The curing method of the crosslinked rubber may be appropriately selected according to the type 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 conductive particles made of a non-magnetic material and magnetic particles bonded to the surface of the heat conductive particles with a binder.

The heat conductive particles may be non-magnetic and have high thermal conductivity. In the present specification, diamagnetic materials and paramagnetic materials other than ferromagnetic materials and antiferromagnetic materials are referred to as nonmagnetic materials. For example, the thermal conductivity of the thermally conductive particles is desirably 200 W / m · K or more. As a material of the heat conductive particles, for example, a carbon material such as graphite or carbon fiber is suitable. Also, aluminum, gold, silver, copper, and alloys based on these may be used. As the heat conductive particles, one kind of particles may be used or two or more kinds of particles may be used in combination.

The shape of the heat conductive particle is not particularly limited as long as it can be combined with the magnetic particle. For example, various shapes such as a flaky shape, a fibrous shape, a columnar shape, a spherical shape, an elliptical sphere shape, and an oval sphere shape (a shape in which a pair of opposing hemispheres are connected by a cylinder) can be employed. When the thermally conductive particles have a shape other than a sphere, the contact area between the composite particles increases. As a result, a heat transfer path is easily secured and the amount of heat transferred is increased. In general, the shape of metal particles such as aluminum, gold, and copper is spherical. On the other hand, even if the graphite particles have a shape with a large aspect ratio, they can be obtained at a lower cost than metal particles. For this reason, graphite is suitable as a material for the thermally conductive particles.

Examples of graphite include natural graphite such as scaly graphite, scaly graphite, and earthy graphite, and artificial graphite. 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 heat conductive 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 transmitted to the thermally conductive particles. Therefore, when the thermally conductive particles are made of expanded graphite, the expanded graphite reaches the expansion start temperature early. 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 particles.

In the case of using expanded graphite as the heat conductive 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 particles and play a role in orienting the thermally conductive particles. The magnetic particles may be directly bonded to the surface of the thermally conductive particles. As described later, when particles other than the magnetic particles are bonded to the surface of the thermally conductive particles, It may be indirectly bonded. Further, the magnetic particles may be adhered to only a part of the surface of the heat conductive 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 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 heat conductive 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 particles is flat, the distance between adjacent heat conductive particles is shorter than when the shape is spherical. 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 heat conductive particles are in contact with each other on the surface. That is, the contact area between the two becomes large. Thereby, the adhesive force of a magnetic particle and a heat conductive particle improves. Therefore, the magnetic particles are difficult to peel off. In addition, the thermal conductivity between the magnetic particles and the thermally conductive particles is also improved. For these reasons, it is desirable to employ flaky particles as the magnetic particles.

In the heat dissipation application of 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 particles. When insulating inorganic particles are bonded to the surface of the heat conductive particles, the heat conductive particles and magnetic particles (conducting particles) between adjacent composite particles, even if the composite particles are oriented in contact with each other. It becomes difficult to contact 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 heat conductive 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 heat conductive 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 adhesiveness to the heat conductive particles and the magnetic particles, the electric insulation between the composite particles and the heat 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 preferably 1/100 or more and 1/10 or less of the particle diameter of the heat conductive 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 heat conductive 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 heat conductive 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 heat conductive particles is also improved. For these reasons, it is desirable to employ flaky particles as the insulating inorganic particles.

The binder for adhering the thermally conductive particles and the magnetic particles and the like may be appropriately selected in consideration of the type of the thermally conductive particles and the influence on the moldability. 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 manufactured, for example, by spraying the powder of the heat conductive particles with a paint in which the powder of the magnetic particles is dispersed in the solution in which the binder is dissolved. Further, a powder raw material containing heat conductive particle powder, magnetic particle powder, and 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 particle size distribution of the composite particle powder has two peaks, a small particle size side peak and a large particle size side peak. The particle size distribution of the composite particle powder may be measured using a laser diffraction / scattering particle size distribution measuring apparatus. As the particle size distribution in the present invention, a volume-based frequency distribution of particles is employed.

From the viewpoint of aligning the small particle size so as to fill the space between the large particle size and not disturb the orientation of the large particle size, the peak particle size of the small particle size side peak and the large particle size side peak It is desirable that the difference from the peak particle size is 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 desirably 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 of the peak particle size of the small particle size side peak to the peak particle size of the large particle size side peak is preferably 1: 2 to 1:20, and 1: 5 to 1 : 15 is more preferable.

In order to enhance the effect of improving thermal conductivity even when the packing rate of the composite particles is relatively low, the large particle size particles included in the large particle size side peak are small in mass ratio and included in the small particle size side peak. It is desirable that they are blended at a ratio equal to or greater than that of the particle size. For example, in the particle size distribution of the composite particle powder, the ratio between the area of the small particle size side peak and 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 filling rate of the composite particles in the elastomer molded body may be determined in consideration of the physical properties of the elastomer molded body, the effect of improving thermal conductivity, and the like. For example, from the viewpoint of having little influence on moldability and physical properties, the filling rate of the composite particles is desirably 50% by volume or less when the volume of the elastomer molded body is 100% by volume. In particular, when the filling rate of the composite particles is 40% by volume or less, there is little interference between the composite particles, and the effect of improving thermal conductivity is large. On the other hand, in order to obtain an effect of improving thermal conductivity, it is desirable that the filling rate of the composite particles is 10% by volume or more. More preferably, the volume is 25% by volume or more.

From the viewpoint of realizing high thermal conductivity, the thermal conductivity when the filling rate of the composite particles is 26% by volume or more and 38% by volume or less when the volume of the elastomer molded body is 100% by volume is 2. 4 W / m · K or more is desirable. The thermal conductivity may be measured 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 base material 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. For example, the above-described heat conductive particles, insulating inorganic particles and the like may be dispersed as they are.

<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 powder preparation step, a mixed raw material preparation step, and a forming step. Hereinafter, each step will be described.

(1) Composite particle powder preparation step This step uses a stirring granulator to stir the powder raw material containing thermally conductive particle powder, magnetic particle powder, and binder to produce composite particle powder, It is a step of classifying the composite particle powder to prepare a small particle size powder and a large particle size powder.

The heat conductive particles, magnetic particles, and binder are as described above. Therefore, the description is omitted here. In addition, regarding the blending amount of the powder of the heat conductive particles, the powder of the magnetic particles, and the binder, considering the magnetic field orientation of the composite particles to be manufactured, the thermal conductivity of the elastomer molded body including the composite particles, What is necessary is just to adjust suitably.

For example, when graphite is employed as the thermally conductive particles, it is desirable that the blending amount of the magnetic particle powder is 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 desirably 2% by mass or more and 4% by mass or less when the total mass of the powder to be bonded is 100% by mass as an amount necessary and sufficient 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 heat conductive particles or the 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 combining insulating particles in addition to magnetic particles, both powders may be stirred together to adhere to the thermally conductive particles, but first the magnetic particles are adhered to the thermally conductive particles. Then, the insulating inorganic particles may be adhered next. In this case, the first stage of this step is the first stirring step of stirring the first powder raw material containing the powder of the heat conductive particles, the powder of the magnetic particles, and the binder, and the powder of the insulating inorganic particles and the binder It is good to comprise so that it may have and the 2nd stirring process of stirring further.

The method for classifying the produced composite particle powder is not particularly limited. For example, it may be performed by sieving, a dry classifier or the like. The particle size ranges of the small particle size powder and the large particle size powder after classification may be appropriately determined in consideration of the thickness of the elastomer molded body to be manufactured. From the viewpoint of aligning the small particle size so as to fill the space between the large particle size and not disturb the orientation of the large particle size, there is a difference in each peak particle size when the particle size distribution is measured. A relatively large one is desirable. For example, the peak particle size of the large particle size powder is preferably at least twice the peak particle size of the small particle size powder. It is more preferable that it is 5 times or more. On the other hand, if the difference in the peak particle size is too large, the effect of improving the thermal conductivity is reduced, so that the peak particle size of the large particle size powder is desirably 20 times or less the peak particle size of the small particle size powder. It is more preferable that it is 15 times or less.

(2) Mixed Raw Material Preparation Step This step is a step of preparing a mixed raw material by mixing the small particle size powder and large particle size powder of the composite particles produced in the previous step and an elastomer raw material.

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. When the elastomer raw material is a foamed urethane raw material, a collision stirring method may be employed in which a polyol raw material and a polyisocyanate raw material are mixed by being injected and collided with each other at a high pressure. In this case, the small particle size powder and the large particle size powder may be blended in advance in at least one of the polyol material and the polyisocyanate material.

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 side powder should be blended at a mass ratio equal to or greater than the small particle size powder. Is desirable. For example, the mass ratio of the small particle size powder to the large particle size powder is desirably 1: 1 to 1:10.

As described above, in the elastomer molded body of the present invention, non-oriented fillers such as heat conductive particles and insulating inorganic particles may be dispersed in the base material in addition to 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.

The blending amount of the composite particle powder (small particle size powder and large particle size powder) may be determined in consideration of the physical properties of the elastomer molded body, the effect of improving thermal conductivity, and the like. For example, from the viewpoint of reducing the influence on moldability and physical properties, it is desirable to blend so that the filling rate of the composite particles is 50% by volume or less when the volume of the elastomer molded body is 100% by volume. . It is more suitable when it is 40 volume% or less. On the other hand, in order to obtain the effect of improving thermal conductivity, it is desirable to blend so that the filling rate of the composite particles is 10% by volume or more. More preferably, the volume is 25% by volume or more.

(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.

¡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 control molding.

Also, 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 large particle size powder and small particle size powder 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 thermal conductive particles, and magnetic particles Stainless steel powder (SUS410L, flakes, average particle size 20 μm) 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 into 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.

Further, a powder of composite particles was produced in the same manner as 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 blended flaky graphite powder and the stainless steel powder 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>
[Example 1]
100 g of the small particle size powder and 400 g of the large particle size powder were mixed to prepare a mixed powder of Example 1 (the mass ratio of the small particle size powder to the large particle size powder was 1: 4).

[Example 2]
50 g of the small particle size powder and 450 g of the large particle size powder were mixed to prepare a mixed powder of Example 1 (the mass ratio of the small particle size powder to the large particle size powder was 1: 9).

[Example 3]
200 g of the small particle size powder and 400 g of the large particle size powder were mixed to prepare a mixed powder of Example 1 (the mass ratio of the small particle size powder to the large particle size powder was 1: 2).

[Example 4]
A mixed powder of Example 1 was prepared by mixing 250 g of the small particle size powder and 250 g of the large particle size powder (the mass ratio of the small particle size powder to the large particle size powder was 1: 1).

[Particle size distribution]
The particle size distribution of the mixed powders of Examples 1 to 4 was measured with a laser diffraction / scattering particle size distribution measuring apparatus (“MT-3300EX” manufactured by Nikkiso Co., Ltd.). In FIG. 1, the particle size distribution of the mixed powder of Example 1 is shown. As shown in FIG. 1, the particle size distribution of the mixed powder (composite particle powder) was confirmed to have two peaks, a small particle size side peak and a large particle size side peak. Here, 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.

Similarly, the peak areas of the small particle size side and the large particle size side were calculated from the particle size distributions of the mixed powders of Examples 2 to 4. As a result, the mixed powder of Example 2 was 1:20. Of the mixed powder of 1: 5, and 1: 1 of the mixed powder of Example 4.

<Manufacture of elastomer moldings>
[Elastomer molded bodies of Examples 1 to 4]
An elastomer molded body was produced using the prepared mixed powders of Examples 1 to 4. 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 Stirring agent 1-ethynyl-1-cyclohexanol 0.3 parts by mass and platinum catalyst (“SIP6830.3” manufactured by Gelest Co., Ltd.) 0.05 parts by mass using a stirring blade for 15 minutes, Created a compound.

Next, a mixed raw material was prepared by mixing the mixed powder with the manufactured silicone compound. The mixed powder was blended so that the filling rate of the composite particles was 32.7% by volume when the volume of the produced elastomer molded body was 100% by volume.

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 1 includes a gantry 2, an electromagnet unit 3, a molding die 4, a planar heater 50, and a heat insulating member 51.

The electromagnet unit 3 is placed on the upper surface of the gantry 2. The electromagnet unit 3 and the gantry 2 are fixed by screwing a bracket 21 to each. The electromagnet portion 3 includes

yoke portions

30U and 30D,

coil portions

31L and 31R, and

pole pieces

32U and 32D.

The yoke portion 30U is made of iron and has a flat plate shape. Similarly, the yoke part 30D is made of iron and has a flat plate shape. The

yoke portions

30U and 30D are arranged to face each other in the vertical direction.

The coil part 31L is interposed between the

yoke parts

30U and 30D. The coil part 31 </ b> L is disposed on the left side of the mold 4. Two coil portions 31L are arranged in the vertical direction. Each of the coil portions 31L includes a core portion 310L and a conductive wire 311L. The core portion 310L is made of iron and has a columnar shape extending in the vertical direction. The conducting wire 311L is wound around the outer peripheral surface of the core portion 310L. The conducting wire 311L is connected to a power source (not shown).

The coil portion 31R is interposed between the

yoke portions

30U and 30D. The coil portion 31 </ b> R is disposed on the right side of the mold 4. Two coil portions 31 </ b> R are arranged in the vertical direction. The coil portions 31R each have the same configuration as the coil portion 31L. That is, the coil portion 31R includes a core portion 310R and a conducting wire 311R. The conducting wire 311R is wound around the outer peripheral surface of the core portion 310R. The conducting wire 311R is connected to a power source (not shown).

The pole piece 32U is made of iron and has a flat plate shape. The pole piece 32U is disposed at the center of the lower surface of the yoke portion 30U. The pole piece 32U is interposed between the yoke portion 30U and the mold 4. The pole piece 32D is made of iron and has a flat plate shape. The pole piece 32D is disposed at the center of the upper surface of the yoke portion 30D.

The molding die 4 is disposed between the coil part 31L and the coil part 31R. The molding die 4 includes an upper die 40U and a lower die 40D. The upper mold 40U has a square plate shape. The lower mold 40D has a rectangular parallelepiped shape. A recess is formed on the upper surface of the lower mold 40D. The recess has a rectangular parallelepiped shape that opens upward. By combining the upper mold 40U and the lower mold 40D, a rectangular parallelepiped cavity 41 is defined. As described above, the cavity 41 is filled with the mixed raw material.

The planar heater 50 has a square sheet shape. The planar heater 50 is disposed so as to cover the lower surface of the lower mold 40D. The mold 4 is held at 100 ° C. by the planar heater 50.

The heat insulating member 51 is made of glass fiber and has a flat plate shape. The heat insulating member 51 is interposed between the planar heater 50 and the pole piece 32D. The heat transfer from the planar heater 50 to the electromagnet unit 3 is suppressed by the heat insulating member 51.

When both the power source connected to the conducting wire 311L and the power source connected to the conducting wire 311R are turned on, the upper end of the core portion 310L of the coil portion 31L 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 310L from the bottom to the top. Similarly, the upper end of the core portion 310R of the coil portion 31R 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 310R from the bottom to the top.

Magnetic field lines L radiated from the upper end of the core portion 310L of the coil portion 31L flow into the cavity 41 of the mold 4 through the yoke portion 30U and the pole piece 32U. Then, it flows into the lower end of the core part 310L through the pole piece 32D and the yoke part 30D. Similarly, the lines of magnetic force L radiated from the upper end of the core portion 310R of the coil portion 31R flow into the cavity 41 of the mold 4 through the yoke portion 30U and the pole piece 32U. Then, it flows into the lower end of the core portion 310R through the pole piece 32D and the yoke portion 30D. Thus, since the magnetic lines L constitute a closed loop, the leakage of the magnetic lines L is suppressed. In the cavity 41 of the mold 4, a uniform magnetic field is formed by magnetic lines L that are substantially parallel from the top to the bottom. Specifically, the magnetic flux density in the cavity 41 was about 300 mT. Further, the difference in magnetic flux density in the cavity 41 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 according to the numbers of the mixed powders.

[Elastomer molded bodies of Comparative Examples 1 and 2]
For comparison, elastomer molded bodies were produced in the same manner as in Examples 1 to 4, except that only a large particle size powder having a particle size of 700 μm or more and 1100 μm or less was blended instead of the mixed powder. There is one peak of the particle size distribution of the mixed composite particle powder. The obtained elastomer molded body was used as the elastomer molded body of Comparative Example 1.

Further, an elastomer molded body was prepared in the same manner as in Examples 1 to 4, except that the powder of composite particles produced using scaly graphite powder “W + 32” was blended as it was without sieving instead of the mixed powder. Manufactured. There is one peak of the particle size distribution of the mixed composite particle powder. The obtained elastomer molded body was used as the elastomer molded body of Comparative Example 2.

<X-ray CT measurement of elastomer molded body>
The alignment state in the direction perpendicular to the surface from the upper surface of the produced elastomer molded body was observed using an X-ray CT apparatus (“SMX-160LT” manufactured by Shimadzu Corporation). FIG. 4 shows an X-ray CT photograph of the elastomer molded body of Example 1. In FIG. 5, the X-ray CT photograph of the elastomer molded object of the comparative example 2 is shown. As shown in FIG. 4, in the elastomer molded body of Example 1, the small particle size particles are dispersed and oriented so as to fill the gap (base material portion) between the large particle size particle and the large particle size particle. I was able to confirm. On the other hand, as shown in FIG. 5, in the elastomer molded body of Comparative Example 2 in which composite powder without classification was blended, almost no small particle size particles were observed between the large particle size particles. I couldn't.

<Evaluation of elastomer molding>
The thermal conductivity of the produced elastomer molded body was measured using “HC-110” manufactured by Eihiro Seiki Co., Ltd. in accordance with the heat flow meter method of JIS A1412-2 (1999). Table 1 shows the evaluation results together with the composition of the powder of the composite particles used.

As shown in Table 1, the thermal conductivity of the elastomer molded bodies of Examples 1 to 4 was larger than the thermal conductivity of the elastomer molded bodies of Comparative Examples 1 and 2. Among them, the thermal conductivity of the elastomer molded bodies of Examples 1 to 3 having a large blending ratio of the large particle size powder was as large as 3.4 W / m · K or more.

<Relationship between packing rate of composite particles and thermal conductivity>
In the elastomer molded body in which the mixed powder of Example 1 was blended, the change in thermal conductivity with respect to the filling rate of the composite particles was examined. For comparison, the change in the thermal conductivity with respect to the filling rate of the composite particles was also examined in an elastomer molded body in which the powder of composite particles produced using the flaky graphite powder “W + 32” was blended as it was without sieving. In FIG. 6, the relationship between the filling rate of the composite particle in two elastomer molded objects and thermal conductivity is shown with a graph.

As shown in FIG. 6, regardless of the filling rate, the elastomer molded body in which the mixed powder of Example 1 was blended had a higher thermal conductivity than the elastomer molded body in which the powder of composite particles without classification was blended. became. Specifically, the thermal conductivity when the filling rate of the composite particles is 26% by volume or more and 38% by volume or less was 2.4 W / m · K or more. In addition, the elastomer molded body in which the mixed powder of Example 1 was blended had a higher filling rate at which the thermal conductivity was maximized than the elastomer molded body in which the composite particle powder without classification was blended. From this result, it can be seen that when the mixed powder of Example 1 is used, the powder of the composite particles can be filled more highly in order to increase the thermal conductivity.

<Relationship between blending ratio of small particle size powder and large particle size powder and thermal conductivity>
Using the mixed powders of Examples 1 to 4, two types of elastomer molded bodies having a composite particle filling rate of 26.4% by volume and 32.7% by volume were produced, and the thermal conductivity of each was measured. Further, for comparison, two types of elastomer molded bodies having a composite particle filling rate of 26.4% by volume and 32.7% by volume are manufactured using only a powder having a particle size of 700 μm or more and 1100 μm or less. The thermal conductivity of each was measured. The method for producing each elastomer molded body is the same as the method for producing the elastomer molded bodies in Examples 1 to 4 described above. FIG. 7 is a graph showing the relationship between the mass ratio between the small particle size powder and the large particle size powder and the thermal conductivity.

As shown in FIG. 7, at any filling rate, an elastomer molded body in which mixed powder is blended is an elastomer molded body in which only large particle diameter powder is blended (the mass of small particle diameter powder and large particle diameter powder). The thermal conductivity was greater than the ratio 0: 1). Moreover, in the elastomer molded body which mix | blended mixed powder, the one where the filling rate was high became large in thermal conductivity. Moreover, in the elastomer molded body which mix | blended mixed powder, when the mixture ratio of the large particle size powder was enlarged, thermal conductivity became large. For example, when the filling rate is 32.7% by volume, the thermal conductivity is maximized in the elastomer molded body in which the mass ratio of the small particle size powder to the large particle size powder is 1: 4.

<Composition of non-oriented filler>
In addition to the mixed powder of Example 1, an insulating inorganic material magnesium oxide powder (“Starmag PSF-WR” manufactured by Kamishima Chemical Industry Co., Ltd., average particle size 1.0 μm) is blended as an unoriented filler, and an elastomer A molded body was produced. The mixed powder of Example 1 was blended so as to be 32.7% by volume when the volume of the elastomer molded body was 100% by volume, and the magnesium oxide powder was blended so as to be 8% by volume. In FIG. 8, the measurement result of thermal conductivity is shown with a graph.

As shown in FIG. 8, even when the non-oriented filler was blended, the effect of improving the thermal conductivity by blending the mixed powder was maintained. Magnesium oxide has a relatively high thermal conductivity. For this reason, when the magnesium oxide powder was blended as the non-oriented filler, the thermal conductivity was increased.

The elastomer molded body 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.

Claims

A base material made of an elastomer, and a powder of composite particles that are oriented and contained in the base material,
The composite particles include thermally conductive particles made of a nonmagnetic material, and magnetic particles bonded to the surface of the thermally conductive particles with a binder,
An elastomer molded article, wherein the particle size distribution of the composite particle powder has two peaks, a small particle size side peak and a large particle size side peak.
The ratio of the peak particle size of the small particle size side peak to the peak particle size of the large particle size side peak in the particle size distribution of the composite particle powder is 1: 2 to 1:20. Elastomer molded body.
The ratio of the area of the small particle size side peak to the area of the large particle size side peak in the particle size distribution of the powder of the composite particles is 1: 1 to 1:30. Elastomer molded body.
Furthermore, the elastomer molded object of any one of Claim 1 thru | or 3 which has a non-orientation filler disperse | distributed in the said base material.
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.
The elastomer molded body according to any one of claims 1 to 5, wherein the thermally conductive particles are made of graphite.
The thermal conductivity when the filling rate of the composite particles is 26 vol% or more and 38 vol% or less when the volume of the elastomer molded body is 100 vol% is 2.4 W / m · K or more. The elastomer molded body according to any one of claims 1 to 6.
It is a manufacturing method of the elastomer fabrication object according to claim 1,
Using an agitation granulator, a powder material containing heat conductive particles, magnetic particle powder, and a binder is stirred to produce composite particle powder, and the composite particle powder is classified to obtain a small particle size. A composite particle powder preparation step of preparing a powder and a large particle size powder;
A mixed raw material preparation step of preparing a mixed raw material by mixing the small particle size powder and the large particle size powder of the composite particles and an elastomer raw material;
A molding step of placing the mixed raw material in a mold and molding the mixed raw material in a magnetic field;
A method for producing an elastomer molded article, comprising:
The method for producing an elastomer molded body according to claim 8, wherein a mass ratio of the small particle size powder and the large particle size powder to be blended in the mixed raw material preparation step is 1: 1 to 1:10.