JP4998744B2 - Spherical zinc oxide particle powder and highly heat conductive composition - Google Patents

Description

  The present invention relates to a spherical zinc oxide particle useful as a heat conductive material, an ultraviolet absorbing material, and a catalyst carrier, and a method for producing the same.

  There is a concern that electronic components such as ICs, transistors, and diodes generate heat due to their operation, and the performance deteriorates due to the heat. In particular, with the recent miniaturization of electronic devices, how to efficiently remove the generated heat has become the biggest challenge for electronic components. In general, in order to remove such heat, a part mainly made of metal called a heat radiator is attached around an electronic part. However, since these are conductive, problems such as electric leakage are not preferable if they are directly attached to an electronic component. Therefore, measures are taken to solve the above problems by interposing a heat conductive grease, a heat conductive sheet or the like between the electronic component and the radiator.

  Thermally conductive grease and thermally conductive sheet are high thermal conductive fillers dispersed in a matrix such as silicone grease, silicone rubber, and acrylic rubber. It is a point. At the same time, in the case of a thermally conductive grease, it is preferable that the viscosity is as low as possible, and in the case of a thermally conductive sheet, the thinner one is preferable.

  As the heat conductive filler, powder of alumina, aluminum nitride, boron nitride, silicon nitride or the like is used. In so-called thermal conductivity, aluminum nitride and silicon nitride are very high and are preferable materials for achieving this object, and various devices have been devised so that these fillers can be highly filled.

  However, aluminum nitride powder or silicon nitride powder undergoes a hydrolysis reaction in the presence of moisture, resulting in a significant decrease in thermal conductivity. At the same time, ammonia gas is generated and present as bubbles, resulting in inherent high thermal conductivity. Cannot be fully utilized.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-142999), an aqueous solution containing carbonate ions and / or bicarbonate ions and ammonium ions and an aqueous solution containing zinc ions are mixed, and the resulting product is 300 ° C. or higher. To produce spherical 0.01 to 10 μm zinc oxide particles. However, there is no description about the sphericity of the obtained particles, and there is no description based on the particle size distribution, pore structure, etc., for example, high packing when trying to fill the polymer material as thermally conductive particles As a result, it becomes difficult to obtain sufficient thermal conductivity.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 11-49516) proposes spherical zinc oxide particles having a fine spherical or acicular protrusion on the particle surface and a particle diameter of 1 to 50 μm. However, due to the projections on the particle surface, the frictional force between the particles is large, and when trying to fill the polymer material, it is difficult to fill the polymer material. There are many pores inside, and the viscosity becomes high when dispersed in a polymer material. As a result, high filling cannot be achieved, and the thermal conductivity is not sufficient.

  In Patent Document 3 (Japanese Patent Laid-Open No. 2002-201483), 40 to 90% by volume of coarse particles of an inorganic powder having an average particle size of 5 to 17 μm and 1/3 to 1 of the average particle size of the coarse particles are disclosed. A combination of 10 to 60% by volume of fine particles having an average particle size of / 40 is proposed. However, the shape and particle size distribution of the coarse particles are not described, and only the thermal conductivity and the dispensing property are improved compared to the case where only conventional fine particles are filled.

In Patent Document 4 (Japanese Patent Laid-Open No. 2000-143808), 5 to 500 weights of nitride or carbide subjected to a surface treatment for preventing the inhibition of the curing reaction of the silicone gel as component A with respect to 100 parts by weight of the silicone gel. 0 to 1200 parts by weight of a basic metal oxide having a specific surface area of 1.0 m ² / g or less and an average particle size of 10 to 100 μm as the B component, and 0 to 500 parts by weight of the reinforcing agent as the C component, D A compound having a composition containing 0 to 20 parts by weight of a crosslinking agent as a component is described. Again, only the average particle size is defined, and there is no description of its shape.

  Patent Document 5 (Japanese Patent Application Laid-Open No. 2001-2830) discloses silica, alumina, and the like that are difficult to hydrolyze the thermally conductive particles for the purpose of preventing hydrolysis of aluminum nitride, boron nitride, silicon nitride and the like. The coating with an inorganic oxide is described. However, the reliability under high temperature and high humidity conditions is not sufficient.

JP 2004-142999 A JP 11-49516 A JP 2002-201483 A JP 2000-143808 A JP 2001-2830 A

  In view of the actual situation, the present invention has an object to provide a material that is highly reliable even in high temperature and high humidity, has high filling properties as much as possible, and has high thermal conductivity.

That is, the present invention has an average particle diameter of 1 to 300 μm, a BET specific surface area of 1 m ² / g or less, a pore volume by mercury intrusion method of 0.05 ml / g or less, and a sphericity of less than 1.4. It is a spherical zinc oxide particle powder characterized by being spherical particles of the present invention (Invention 1).

  Moreover, this invention is a highly heat conductive composition which contains the spherical zinc oxide particle powder of Claim 1 of 30 volume% or more in the material which has a polymeric material as a main component (invention 2).

  Since the spherical zinc oxide particle powder according to the present invention has almost no pores by the mercury intrusion method and has an average particle diameter of 1 to 300 μm and is a spherical particle, it is a thermally conductive material, an ultraviolet absorbing material. It is useful as a catalyst support.

The spherical zinc oxide particles according to the present invention have an average particle diameter (D50) of 1 to 300 μm, a BET specific surface area of 1 m ² / g or less, and a pore volume by mercury intrusion method of 0.05 ml / g or less. A zinc oxide spherical particle powder composed of zinc oxide spherical particles characterized by a sphericity of less than 1.4.

  The particle shape of the spherical zinc oxide particle powder according to the present invention is spherical, and the sphericity (major axis diameter / minor axis diameter) is less than 1.4. When the particle shape is not spherical, the filling property is lowered.

  The average particle diameter (D50) of the spherical zinc oxide particle powder according to the present invention is 1 to 300 μm. Particles having an average particle diameter (D50) of less than 1 μm are difficult to increase the filling amount when molded with a resin or the like. On the other hand, when the thickness exceeding 300 μm is used as a filler for a heat conductive sheet, it is difficult to increase the filling amount. A preferable average particle diameter (D50) is 1 to 200 μm, and more preferably 1 to 100 μm.

The particle size distribution of the spherical ferrite particle powder according to the present invention is as follows: D _{90 with} respect to the average particle diameter in the case of D ₅₀ (when the particle diameter expressed in cumulative volume is defined with the total volume of the ferrite particle powder being 100%. The average particle size ratio (D ₉₀ / D ₅₀ ) in the case where the cumulative ratio is 90%) is preferably 3.0 or less, more preferably 2.8 or less. D ₁₀ (the point at which the cumulative ratio when the particle size represented by the cumulative volume is 100% when the total volume of the ferrite particle powder is 100% is 10%) is indicated by D ₅₀ with respect to the average particle size. The ratio of average particle diameter (D ₅₀ / D ₁₀ ) is preferably 3.0 or less, more preferably 2.5 or less.

The BET specific surface area of the spherical zinc oxide particle powder according to the present invention is 1.0 m ² / g or less. When the BET specific surface area exceeds 1.0 m ² / g, the filling amount cannot be increased. Furthermore, the thermal conductivity is lowered. A preferred BET specific surface area is 0.01 to 0.15 m ² / g.

  The spherical zinc oxide particle powder according to the present invention has a pore volume of 0.05 ml / g or less by mercury porosimetry. When the pore volume by the mercury intrusion method exceeds 0.05 ml / g, the filling amount cannot be increased and the thermal conductivity is also lowered. The preferred pore volume is 0.001 to 0.01 ml / g.

  The water content of the spherical zinc oxide particles according to the present invention is preferably less than 0.1% after standing for 24 hours at 33 ° C. and 80% RH. If the moisture content is higher than 0.1%, the electronic component, the substrate, the heat sink or the like may be corroded. More preferably, it is 0.01 to 0.08%.

  The specific gravity of the spherical zinc oxide particle powder according to the present invention is preferably 5.47 to 5.60. When the specific gravity is less than 5.47, the resin remains, which is not preferable. More preferably, it is 5.50-5.60.

  The bulk density of the spherical zinc oxide particles according to the present invention is preferably 2.45 to 2.80 g / ml. When the bulk density is less than 2.45 g / ml, it is difficult to improve the filling property into the polymer. Zinc oxide particle powder having a bulk density exceeding 2.80 g / ml is difficult to produce industrially.

The volume resistivity value of the spherical zinc oxide particles according to the present invention is preferably 1.0 × 10 ⁹ Ωcm or more. When the volume specific resistance value is less than 1.0 × 10 ⁹ Ωcm, problems such as electric leakage occur when used for electronic components. It is preferable that the volume resistivity value is as high as possible.

  Next, a method for producing spherical zinc oxide particle powder will be described.

  The spherical zinc oxide particle powder according to the present invention reacts and cures phenols and aldehydes in an aqueous medium in the presence of zinc oxide raw material particles to produce composite particles composed of zinc oxide raw material particles and a phenol resin. Then, the phenol resin is removed by heat treatment at 400 to 700 ° C., and the zinc oxide raw material particle powder is sintered by further heat treatment at 800 to 1400 ° C.

  The average particle diameter of the zinc oxide raw material particles in the present invention may be any particle that is smaller than the average particle diameter of the composite particles, and is in the range of 0.01 to 5.0 μm, particularly 0.1 to 2.0 μm. Those are preferred. When the average particle diameter of the zinc oxide raw material particles is less than 0.01 μm, the content of the zinc oxide raw material particles in the composite particles is low. On the other hand, when the average particle diameter exceeds 5.0 μm, the surfaces of the composite particles and the ferrite particles become uneven. Or the sphericity is low.

  In addition, it is desirable that the zinc oxide raw material particles have been subjected to lipophilic treatment in advance, and when using zinc oxide raw material particles that have not been subjected to lipophilic treatment, it becomes difficult to obtain spherical composite particles. There is a case.

  The lipophilic treatment is a method of treating zinc oxide raw material particles with a coupling agent such as a silane coupling agent or a titanate coupling agent, or dispersing zinc oxide raw material particles in an aqueous medium containing a surfactant, There is a method of adsorbing a surfactant on the particle surface.

  Silane coupling agents include those having a hydrophobic group, an epoxy group, and an amino group, and these may be used alone or in combination of two or more as required.

  Examples of silane coupling agents having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy) silane, and titanate coupling agents include isopropyltriisostearoyl titanate and isopropyltridodecyl. Examples include benzenesulfonyl titanate and isopropyl tris (dioctyl pyrophosphate) titanate.

  Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and β- (3,4-epoxycyclohexyl) trimethoxysilane.

  Examples of the silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyl. Examples include methyldimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane.

  The surfactant is not particularly limited, and a known surfactant can be used. However, those having a functional group capable of bonding to the inorganic compound particles and the hydroxyl groups on the surface of the particles are desirable. Cationic or anionic ones are preferred. These may be used alone or in combination of two or more as required.

  The object of the present invention can be achieved by any of the above-mentioned treatment methods, but treatment with a silane coupling agent having an amino group or an epoxy group is preferable in view of adhesion to a phenol resin.

  The amount of the lipophilic agent in the present invention is preferably 0.1 to 5.0% by weight with respect to the zinc oxide raw material particles. If it is less than 0.1% by weight, it becomes difficult to make the coating of the lipophilic agent adhere to the surface of the composite particles, and the content of zinc oxide raw material particles because the lipophilic treatment is insufficient. High composite particles cannot be obtained. Moreover, the zinc oxide raw material particles are not firmly embedded in the composite particles. On the other hand, when it exceeds 5.0% by weight, the coating of the lipophilic agent can be brought into close contact with the surface of the composite particles, but the generated composite particles are aggregated, and the particle size of the composite particles is increased. It becomes difficult to control.

  In order to produce spherical zinc oxide particles according to the present invention, first, by reacting phenols and aldehydes in an aqueous medium in the presence of zinc oxide raw material particles and a basic catalyst, Spherical composite particles composed of a phenol resin are prepared.

  The content of the zinc oxide raw material particles in the composite particles is preferably 80 to 98% by weight. When the amount is less than 80% by weight, the amount of phenol resin is increased, and in the subsequent heat treatment, it is not preferable because much energy is required for removing the phenol resin. On the other hand, when the amount exceeds 98% by weight, The strength of the composite particles before the heat treatment becomes weak, and the particles may be destroyed during the heat treatment.

  As a basic catalyst in this invention, the basic catalyst used for normal phenol resin manufacture is used. Examples thereof include aqueous ammonia, hexamethylenetetramine, and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The molar ratio of these basic catalysts to phenols is preferably 0.02 to 0.7. When the molar ratio is less than 0.02, the reaction does not proceed sufficiently. On the other hand, when it exceeds 0.7, a large amount of excess basic catalyst remains in the reaction solution, which increases the load of wastewater treatment.

  As phenols in the present invention, in addition to phenol, alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, bisphenol A, and a part or all of benzene nucleus or alkyl group are chlorine atoms. And compounds having a phenolic hydroxyl group such as halogenated phenols substituted with a bromine atom, and these are used alone or in combination of two or more as required. Among them, phenol is most preferred. That is, when a compound other than phenol is used as the phenol, particles may be difficult to produce, or even if particles are produced, the shape may be indefinite. preferable. In some cases, a commercially available phenol resin can be used in a form dissolved in a solvent such as alcohol.

  Examples of the aldehydes in the present invention include formaldehyde and furfural in any form of formalin or paraformaldehyde, and these are used singly or in combination of two or more as required, but formaldehyde is particularly preferable in terms of economy. . The molar ratio of aldehydes to phenols is preferably 1 to 4, particularly preferably 1.2 to 3. If the molar ratio of aldehydes to phenols is less than 1, particles are difficult to form, and even if they are formed, the resin tends to harden, so that the strength of the generated particles tends to be weak. When the molar ratio is larger than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

  In the present invention, the spherical composite particles composed of the zinc oxide raw material particles and the phenol resin are cured at the same time as the reaction in the temperature range of 70 to 90 ° C. and then cooled to 40 ° C. or lower. A dispersion is obtained.

  Next, the solid dispersion is separated from the aqueous dispersion according to a conventional method such as filtration and centrifugation, and then dried to obtain spherical composite particles composed of zinc oxide raw material particles and a phenol resin.

  In the reaction in the present invention, a suspension stabilizer may be present if necessary.

  Examples of the suspension stabilizer include hydrophilic organic compounds such as carboxymethyl cellulose and polyvinyl alcohol, fluorine compounds such as calcium fluoride, and water-insoluble inorganic salts such as calcium sulfate. These may be used alone or necessary. 2 or more types are used in combination.

  Next, the phenol resin is removed by heat-treating the obtained spherical composite particles. The heat treatment is performed at a temperature at which the phenol resin decomposes, that is, a temperature of 400 to 700 ° C. When the temperature exceeds 700 ° C., aggregation between particles occurs and the particle size distribution becomes wide. On the other hand, when the temperature is lower than 400 ° C., the phenol resin is not sufficiently decomposed and removed. A preferable temperature range of the heat treatment is 500 to 600 ° C.

  The treatment time of the heat treatment at 400 to 700 ° C. is usually about 2 to 8 hours, although it varies depending on the heating temperature. If it is less than 2 hours, the decomposition of the phenol resin tends to be insufficient, and the removal of the resin tends to be insufficient. On the other hand, if it exceeds 8 hours, the treatment time itself becomes too long. The atmosphere is preferably an oxidizing atmosphere because it decomposes the phenol resin and does not leave it as carbon.

  The heat treatment furnace may be either a fixed type or a rotary type, but a rotary type is preferable in order to prevent particles from aggregating.

  The oxidizing atmosphere in the present invention is sufficient if air is flowed into the heat treatment furnace, and it is sufficient if it is flowed at a flow rate of 1 L / min or more. If it is less than 1 L / min, the decomposition gas of the resin is filled in the heat treatment furnace, so that it remains as carbon.

  Next, heat treatment (sintering) for subsequent sintering is performed. This heat treatment is performed at a temperature of 800 to 1400 ° C. When it exceeds 1400 ° C., the particles are sintered with each other, and the particle size distribution becomes wide. On the other hand, if it is less than 800 degreeC, sintering will be inadequate and the intensity | strength of granulated particle will run short. A preferable temperature range of the heat treatment (firing) is 900 to 1300 ° C.

  The treatment time for the heat treatment at 800 to 1400 ° C. is about 1 to 10 hours, although it varies depending on the heating temperature. If it is less than 1 hour, the sintering tends to be insufficient, whereas if it exceeds 10 hours, the productivity tends to decrease.

  The atmosphere for the heat treatment may be performed in an oxidizing atmosphere while flowing air. The gas flow rate is preferably 1 L / min or more. If it is less than 1 L / min, it is difficult to obtain the surface properties of the desired particles.

  Next, a highly heat conductive composition is described.

  The spherical zinc oxide particles according to the present invention are used alone or mixed with materials such as aluminum nitride, boron nitride, and alumina, and dispersed in a polymer material such as silicone resin, silicone gel, silicone oil, and epoxy resin. A high thermal conductive composition can be obtained. The content of the spherical zinc oxide particles according to the present invention is preferably 30% by volume or more, and 35% by volume or more is preferable to increase the thermal conductivity, and 40% by volume or more is more preferable. Without using spherical particles with a controlled particle size distribution, it is very difficult to mix zinc oxide particle powder exceeding 60% by volume.

  The spherical zinc oxide particles according to the present invention obtained as described above are useful as a heat conductive material, an ultraviolet absorbing material, and a catalyst carrier.

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First, the important point in the present invention is to first prepare composite particles composed of zinc oxide raw material particles and a phenol resin, and then heat-treat the composite particles at 400 to 700 ° C. to decompose the phenol resin, It is to sinter by performing heat processing (baking) at 800-1400 degreeC continuously. In particular, composite particles composed of zinc oxide raw material particles and phenol resin once prepared have a high content of zinc oxide raw material particles, almost no pores by mercury intrusion method, and an average particle diameter of 1 to 300 μm. It is important that the spherical particles are sintered and are sintered by heat treatment while maintaining the particle size distribution.

Regarding the reason why the spherical zinc oxide particle powder according to the present invention has a pore volume by a mercury intrusion method of 0.05 ml / g or less and a BET specific surface area of 1.0 m ² / g or less, the present inventor once Due to the extremely high filling amount of the zinc oxide raw material particles in the spherical composite particles composed of the zinc oxide raw material particles and the phenol resin to be prepared, and the composite particles having almost no pores by the mercury intrusion method. Even after subsequent sintering by heat treatment, the pore volume is considered to be 0.05 ml / g or less and the BET specific surface area is assumed to be 1.0 m ² / g or less.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not restrict | limited at all by these.

  In addition, the average particle diameter in the following Examples and Comparative Examples was shown as a value measured by a laser diffraction particle size distribution meter (RODOS manufactured by SYMPATEC).

  The particle morphology of the particles was observed with an emission scanning electron microscope (S-4800 FE-SEM (Type-I) manufactured by Hitachi, Ltd.).

  The bulk density was measured according to the method described in JIS K5101.

  The sphericity is measured by randomly extracting 250 or more spherical composite particles with an emission scanning electron microscope (S-4800 FE-SEM (Type-I) manufactured by Hitachi, Ltd.), and calculating the average major axis diameter l and The average minor axis diameter w was obtained and calculated by the following formula.

Sphericity = l / w
l: Average major axis diameter of spherical composite particles w: Average minor axis diameter of spherical composite particles

  The BET specific surface area was measured by a nitrogen adsorption method.

  The pore volume was indicated by a value measured with a mercury intrusion autopore 9220 (trade name, manufactured by Shimadzu Corporation).

  As the volume resistivity value, a value measured with a high resistance meter 4339B (trade name, manufactured by Yokogawa Hewlett-Packard Company) was used.

  The moisture content was determined by first leaving the obtained spherical zinc oxide particle powder in a constant temperature and humidity chamber at 33 ° C. and 80% RH for 24 hours, and then Karl Fischer moisture meter AQ-2100 (trade name, manufactured by Hiranuma Sangyo Co., Ltd.) The value measured in was used.

  The thermal conductivity is obtained by first mixing the obtained spherical zinc oxide particles or the commercially available spherical alumina for comparison with a silicone resin (CY52-276A &B; manufactured by Toray Dow Corning Co., Ltd.) at a predetermined ratio, and further using a vacuum pump. Is sufficiently deaerated to produce a molded body having a size of 50 mm × 100 mm. The value measured with a rapid thermal conductivity meter QTM-500 (trade name, manufactured by Kyoto Electronics Co., Ltd.) after drying at 80 ° C. using a dryer was used.

Example 1
Charge 1 kg of ZnO (1 type) with an average particle size of 1 μm into a Henschel mixer, stir well, then add 5 g of silane coupling agent KBM-902 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.) having an amino group. After mixing, the surface of the raw material particles was treated with a silane coupling agent having an amino group.

  Next, 108 g of phenol, 155 g of 37% formalin, 1 kg of the above raw material particles treated with a silane coupling agent having an amino group on the particle surface, 28 g of 25% aqueous ammonia and 112 g of water are charged into a 1 L flask and stirred. While raising the temperature to 70 ° C. over 60 minutes, the mixture is reacted at the same temperature for 60 minutes, and then heated to 85 ° C. over 30 minutes. By reacting and curing at the same temperature for 120 minutes, composite particles composed of phenol resin and zinc oxide raw material particles were obtained.

  Next, the contents in the flask are cooled to 30 ° C., the supernatant liquid is removed, and the precipitate in the lower layer is further filtered and dried at 80 ° C. for 7 hours with an air dryer to obtain composite particles (A). It was.

The obtained composite particles (A) had an average particle diameter of 11 μm, a content of the filling component of 87% by weight, a BET specific surface area of 0.01 m ² / g, and a pore volume of 0.001 ml / g.

  Next, this is put into a rotary heat treatment furnace having an internal volume of 10 L, and while the air is flowed at a flow rate of 3 L / min, the inside of the heat treatment furnace is raised to 600 ° C. in 2 hours, and heat treatment (heating) is performed at the same temperature for 4 hours. After removing phenol resin by treatment I), the temperature was raised to 1200 ° C. in 2 hours, followed by heat treatment at the same temperature for 5 hours (heat treatment II) to perform sintering. Then, after cooling to room temperature, it took out and obtained spherical zinc oxide particles (I).

The average particle diameter of the obtained zinc oxide particles was 11 μm. The BET specific surface area is 0.02 m ² / g, the pore volume is 0.004 ml / g, the volume resistivity is 2.5 × 10 ¹⁰ Ωcm, the sphericity is 1.2, and the water content is 0.05%. there were.
Further, SEM photographs of the obtained zinc oxide particles are shown in FIGS.

Example 2
A composite particle B was obtained in the same manner as in Example 1 except that the kind and amount of the lipophilic agent and other reaction conditions were changed. The manufacturing conditions and various characteristics at this time are shown in Tables 1 to 3.

Comparative Example 1
20 g of polyvinyl alcohol and 200 g of water were added to 1 kg of the same zinc oxide raw material particles as in Example 1 to make a slurry. This slurry was granulated and dried with a spray dryer to prepare composite particles (C) having an average particle diameter of 72 μm.
Next, the particles are placed in a rotary heat treatment furnace, and while the air is flowed at 3 L / min, the heat treatment furnace is heated to 600 ° C. in 2 hours, and heat treatment I is performed at the same temperature for 2 hours to obtain polyvinyl alcohol. After the removal, the temperature was subsequently raised to 1200 ° C. in 3 hours, and heat treatment II was performed at the same temperature for 4 hours to obtain zinc oxide particles (III).

The manufacturing conditions and various characteristics at this time are shown in Tables 1 to 3.

Production of High Thermal Conductivity Composition According to the composition ratio shown in Table 4, various inorganic compounds and silicone resin (CY52-276A &B; manufactured by Toray Dow Corning Co., Ltd.) are sufficiently mixed, and further deaeration is sufficiently performed by a vacuum pump. A molded body having a size of 50 mm × 100 mm was produced.

  Table 4 shows various characteristics of the obtained high thermal conductive composition.

  In Table 4, about Examples 3-5 and Comparative Examples 2-4, if the example with the same content of particle | grains (A + B) is contrasted, it will be confirmed that the composition which concerns on this invention has high thermal conductivity. It was. Moreover, also about Examples 6-8 and Comparative Examples 5-7, if the content of particle | grains (A + B) was contrasted, it was confirmed that the composition which concerns on this invention has high thermal conductivity. .

As described above, the spherical zinc oxide particles according to the present invention have a spherical shape, a specific particle size distribution, a high volume resistivity value of 1 × 10 ⁹ to 1 × 10 ¹¹ Ωcm, and a BET ratio. Since it has a surface area of 0.2 m ² / g or less, a pore volume of 0.05 ml / g or less, and a structure having few pores, it is useful as a heat conductive material. Further, it is useful as an ultraviolet absorbing material and a catalyst carrier.

2 is an electron micrograph of spherical zinc oxide particles (I) obtained in Example 1 (× 5,000). 2 is an electron micrograph of spherical zinc oxide particles (I) obtained in Example 1. (× 10,000)

Claims (2)

Spherical particles having an average particle diameter of 1 to 300 μm, a BET specific surface area of 1 m ² / g or less, a pore volume by mercury intrusion method of 0.05 ml / g or less, and a sphericity of less than 1.4. Spherical zinc oxide particle powder characterized by A highly thermally conductive composition comprising the spherical zinc oxide particle powder according to claim 1 in a volume of 30% by volume or more in a material mainly composed of a polymer material.