JP2019073419A - Zinc oxide particle and method for producing the same, and application of the same - Google Patents

Abstract

To provide zinc oxide particles having excellent thermal conductivity, and to provide a method for producing the same.SOLUTION: Zinc oxide particles have a spherical shape and have an outer shell formed by integrating a plurality of plate pieces of zinc oxide particles to overlap partially with one another, wherein it is preferable that median diameter (D50) is in a range of 15 to 30 μm. The zinc oxide particles are produced by aging a solution comprising a zinc compound, a carboxylic acid and/or its salt, and a basic compound, for example, under a hydrothermal condition of 120 to 200°C.SELECTED DRAWING: Figure 2

Description

  The present invention relates to zinc oxide particles, a method for producing the same, and a composition containing zinc oxide particles.

  A thermal interface material used for an electronic device or the like is provided, for example, between a heat generating device such as a CPU and a heat sink. The heat transfer material promotes heat transfer from the device to the heat sink to prevent the device from becoming hot (and thus the electronics fail).

  Examples of the heat conductive material include those in which a heat dissipating filler is mixed with a resin, a base oil, etc. (hereinafter referred to as “heat dissipating composition”), and zinc oxide is known as a heat dissipating filler used for the heat dissipating composition. There is. Zinc oxide has a thermal conductivity almost at the middle value of alumina and aluminum nitride, which are general heat radiation fillers, and is a relatively well-balanced material in terms of powder physical properties such as linear expansion coefficient and hardness, and cost. Because of their existence, various studies have been made as materials for heat dissipating fillers.

  When zinc oxide is used as a heat radiation filler, the shape of the zinc oxide particles is preferably spherical. When it is spherical, it can be highly filled with respect to the heat dissipating composition, and the heat conductivity can be improved by increasing the proportion of the heat dissipating filler in the heat dissipating composition. is there. In addition, it is considered that the use of the spherical heat dissipating filler advantageously affects the flowability of the heat dissipating composition. Then, various spherical zinc oxide particles for a heat dissipation filler are proposed.

  For example, Patent Document 1 describes spherical zinc oxide particles having a median diameter of about 20 to 40 μm, which are obtained by mixing zinc source particles and an organic acid (such as acetic acid), granulating and firing the mixture. ing. Further, in Patent Document 2, a plurality of small particle size zinc oxides are solidified with a phenol resin to form a complex, which is fired to remove the phenol resin, and obtained by sintering zinc oxides having small particle sizes. There are described spherical zinc oxide particles having an average particle diameter of about 10 to 100 μm.

International Publication No. 2011/0043207 JP, 2009-249226, A

  With the recent increase in speed and integration of semiconductor devices, the calorific value and the calorific density from electronic devices tend to increase. Under such circumstances, the thermal conductivity of the heat dissipating composition using the above-described conventional zinc oxide particles is not sufficient. Therefore, zinc oxide particles having further excellent thermal conductivity are required.

  The inventors of the present invention conducted zinc heat treatment under predetermined conditions to obtain zinc oxide particles having a special shape which has not been conventionally achieved, while examining the zinc oxide particles appropriately for the above purpose. . And when this zinc oxide particle is used as a thermal radiation filler, it discovered that the thermal conductivity of a thermal radiation composition can be improved more compared with the former, and completed this invention.

That is, the zinc oxide particles of the present invention are
(1) Spherical zinc oxide particles having an outer shell formed by accumulating a plurality of zinc oxide platelets so as to partially overlap with each other
(2) The zinc oxide particles according to (1), wherein the plate-like piece is a hexagonal plate-like,
(3) The zinc oxide particles according to (1) or (2), wherein the median diameter is 15 to 30 μm,
(4) The zinc oxide particles according to any one of (1) to (3), wherein D90 / D50 is 1.5 or less,
(5) The zinc oxide particles according to any one of (1) to (4), having an organic compound coating and / or an inorganic compound coating on the surface,
(6) A resin composition comprising the zinc oxide particles according to any one of (1) to (5),
(7) The resin composition according to (6), comprising a small particle size heat radiation filler having a median diameter smaller than that of the zinc oxide particles,
(8) A grease comprising the zinc oxide particles according to any one of (1) to (5),
(9) A cosmetic comprising the zinc oxide particle according to any one of (1) to (5),
(10) A paint composition comprising the zinc oxide particles according to any one of (1) to (5),
(11) A method for producing zinc oxide particles, which comprises aging a solution containing a zinc compound, a carboxylic acid and / or a salt thereof, and a basic compound under hydrothermal conditions.

Since the zinc oxide particles of the present invention have a spherical shape, they can be added to a resin or the like at a high filling rate, and moreover, it is possible to secure sufficient fluidity for practical use. In addition, at least the outer shell of the zinc oxide particles is formed by accumulating a plurality of zinc oxide plate-like pieces so as to partially overlap with each other, so that the thermal conductivity is excellent. For this reason, the zinc oxide particles of the present invention are useful as a heat dissipating filler used for a heat dissipating composition (resin composition for heat dissipating use, grease, etc.).
Moreover, since it has fluidity | liquidity and fillability sufficient for practical use by mix | blending the zinc oxide particle of this invention also except a thermal radiation use, it can be used for uses, such as a cosmetics, a coating composition, and a resin composition. .

1 is a powder X-ray diffraction spectrum of the zinc oxide particles (sample a) of Example 1. FIG. It is an electron micrograph of the zinc oxide particle (sample A) of Example 1. 3 is an electron micrograph (enlarged view) of the zinc oxide particles (sample A) of Example 1. FIG. It is an electron micrograph (sectional view) of the zinc oxide particle (sample A) of Example 1. It is an electron micrograph of the zinc oxide particle (sample B) of Example 2. It is an electron micrograph of the zinc oxide particle (sample C) of Example 3. It is an electron micrograph of the zinc oxide particle (sample D) of comparative example 1. It is the conceptual diagram which showed the mode of the heat transfer on the zinc oxide particle surface of this invention. It is the conceptual diagram which showed the contact state between the particles of the zinc oxide particle of this invention.

The zinc oxide particles of the present invention are spherical particles, and have an outer shell formed by accumulating a plurality of plate-like pieces so as to partially overlap.
The zinc oxide particles of the present invention contain, as a component, at least 50% by mass of zinc oxide (ZnO) exhibiting an X-ray diffraction pattern of any one of hexagonal, cubic and cubic face-centered structures. The zinc oxide particles of the present invention may contain zinc hydroxide such as zinc hydroxide and zinc sulfate such as zinc sulfate, zinc nitrate, zinc chloride and zinc acetate which is an unreacted material of the raw material, and the composition of the zinc compound of the raw material Elements such as sulfate, nitrate, chlorine and acetic acid may be contained. Moreover, various materials (carboxylic acid, its salt, an amine compound etc.) other than the zinc source added at the time of synthesis | combination of zinc oxide particle may be included.

The zinc oxide particles of the present invention are spherical particles. The term "spherical" in the present invention includes not only perfect spheres (true spheres) but also shapes based on spheres in which a part thereof is missing. However, from the viewpoint of the filling property to the resin or the like, or the fluidity (viscosity) of the resin composition contained in the resin, it is preferable that the shape is more nearly spherical. Specifically, the sphericity is preferably in the range of 1.0 to 1.3, and more preferably in the range of 1.0 to 1.2.
The shape of the zinc oxide particles of the present invention can be confirmed by a scanning electron microscope. In addition, the sphericity of the zinc oxide particles of the present invention is obtained by measuring the major axis and minor axis length of the 50 particles present in the field of view in an electron micrograph taken with a scanning electron microscope. The ratio of major axis / minor axis is determined and calculated as the average value.

  The "plate-like small piece" which comprises the outer shell of the spherical zinc oxide particle of this invention means the thing of a flat plate-like and / or scaly small particle. The plate surface shape of such a plate-like piece is not particularly limited, and may be a polygonal shape, or any other irregular shape (for example, based on a polygon, at least a part of its corners or sides is missing) Or a shape that is smoothed by removal of corners.

  In addition, "a plurality of plate-like pieces are accumulated so as to partially overlap" can be rephrased as a state in which the plate-like small pieces overlap with each other while being slightly offset and stacked. Such an accumulation structure is a structure such as a cuticle structure of hair or a laminated structure of fish scales. The aspect of lamination of plate-like small pieces in zinc oxide particles can also be confirmed by a scanning electron microscope. FIG. 3 shows an electron micrograph of the surface of the zinc oxide particles of the present invention as a specific example of such a structure.

The zinc oxide particles of the present invention are characterized by having the above-described integrated structure, and it is considered that this contributes to the improvement of the thermal conductivity. Although the mechanism is not clear, the present inventors speculate as follows.
It is known that heat is more easily transmitted in the direction of the plate surface compared to the thickness direction of the plate piece when viewed in the unit of the plate piece of zinc oxide (see WO 2012/147886 etc.) . For this reason, it is considered that in a state where the plate-like pieces are partially overlapped and accumulated, heat is successively transferred in the direction of the plate-like surface from one plate-like piece to the next plate-like piece (see FIG. See 8). The broken line portion of the figure represents the outer shell of spherical zinc oxide particles. The zinc oxide particles of the present invention are considered to be in a state in which heat transfer at the particle surface is likely to occur because the outer shell of the particles is formed by such an accumulation structure.
Moreover, when the contact state of the zinc oxide particles in the state contained in a resin composition etc. is considered, as shown in FIG. 9, it is thought that the plate-shaped surfaces of a plate-shaped piece contact. In the case of simple spherical zinc oxide particles, the contact between the particles is considered to be a point contact, so the contact area between the particles can be increased compared to this, and the heat conduction between the particles is also considered to be promoted. .

  At least the outer shell of the zinc oxide particles of the present invention is configured as an accumulation structure of plate-like small pieces. In other words, the inside of the particle (the part other than the outer shell) may have any structure as long as it is not completely hollow (hollow). For example, the inside of the particle may be constituted by a plate-shaped piece, and the plate-shaped piece may be constituted by small particles (spherical, anisotropic shape, etc.) having different shapes. Alternatively, it may be in a state in which the boundaries between the individual particles are not clear because plate-like small pieces and small particles constituting the inside of the particles are fused to each other by sintering or the like. From the viewpoint of thermal conductivity, it is preferable that the inside of the zinc oxide particles be densely filled with almost no gaps.

  The plate surface shape of the plate-like piece is preferably a hexagonal shape. As described above, the “hexagonal shape” includes, as described above, shapes having at least a part of the corners and sides missing or smooth on the basis of a hexagon (see FIG. 3). ). When the plate surface of the plate-like piece is hexagonal, a plurality of plate-like pieces are easily accumulated finely, and it is considered that the thermal conductivity of the particles is improved by the high density of the zinc oxide particles. In addition, by integrating plate-shaped pieces having hexagonal plate surfaces to form a particle surface, spherical zinc oxide particles closer to a true sphere can be obtained, and the filling property to a resin or the like, and a composition containing the same. The liquidity of the

  The plate-like small pieces preferably have a maximum diameter of about 1 to 6 μm and a thickness of about 0.05 to 0.5 μm. It is considered that the thermal conductivity of the particles is improved by the fact that a plurality of plate-like pieces are easily stacked densely within this numerical range, and the zinc oxide particles have a high density. The plate surface shape, dimensions, etc. of the plate-like piece can be confirmed by a scanning electron microscope.

The zinc oxide particles of the present invention preferably have a median diameter (D50) in the range of 15 to 30 μm, and more preferably in the range of 18 to 30 μm. As described above, by using zinc oxide particles having a relatively large particle diameter, the interface of the particles in the heat dissipating composition can be made smaller, and the heat resistance between the particles is reduced to achieve sufficient heat dissipation performance. It can be secured. In addition, by using zinc oxide particles having a large particle diameter, it is possible to suppress the increase in viscosity of the heat dissipation composition when the zinc oxide particles are highly filled. As a result, it is possible to realize a heat dissipating composition having a practically usable viscosity range (500 Pa · s or less) and high heat dissipating performance.
The median diameter D50 is measured using a laser diffraction / scattering type particle size distribution measuring apparatus (Partica LA-950V2 manufactured by Horiba, Ltd.).

The zinc oxide particles of the present invention preferably have a D90 / D50 of 1.5 or less. Here, D90 is a particle size at which the cumulative frequency in the particle size distribution of zinc oxide particles is 90%. The small value of the ratio of D90 to D50 means that the amount of coarse particles having an extremely large particle size is small, and the particle size distribution is narrow (the particle size is uniform). Thereby, sufficient fluidity can be secured in the composition containing zinc oxide particles, and the filling property to the composition can also be improved.
As a simple method of setting D90 / D50 to 1.5 or less, pulverization, classification by sieve, etc. may be mentioned. D90 is also measured using the above-mentioned laser diffraction / scattering type particle size distribution measuring apparatus (Partica LA-950V2 manufactured by Horiba, Ltd.).

  In addition, the surface of the above-mentioned zinc oxide particles may be covered with an organic compound, if necessary. Examples of the organic compound include organic silicon compounds, organic metal compounds, polyols, alkanolamines, higher fatty acids, higher hydrocarbons and the like. By coating the zinc oxide particles with these organic compounds, dispersibility in solvents, paints, plastics and the like can be imparted. The organic compounds may be used alone or in combination of two or more.

  Examples of organosilicon compounds include organopolysiloxanes (dimethylpolysiloxane, methylhydrogenpolysiloxane, methylmethoxypolysiloxane, methylphenylpolysiloxane, dimethylpolysiloxanediol, dimethylpolysiloxane dihydrogen etc. or copolymers thereof) Organosilanes (aminosilane, epoxysilane, methacrylsilane, vinylsilane, mercaptosilane, chloroalkylsilane, alkylsilane, fluoroalkylsilane etc. or hydrolysis products thereof), organosilazanes (hexamethylsilazane, hexamethylcyclo) Trisilazane etc.).

  Organic metal compounds include organic titanium compounds (aminoalkoxytitanium, phosphoric acid ester titanium, carboxylic acid ester titanium, sulfonic acid ester titanium, titanium chelate, phosphorous acid ester titanium complex, etc.), organic aluminum compounds (aluminum chelate etc.), Organic zirconium compounds (carboxylic acid ester zirconium, zirconium chelate, etc.) can be mentioned.

Examples of the polyols include trimethylolpropane, trimethylolethane, pentaerythritol and the like.
As alkanolamines, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine etc. or derivatives thereof (acetate, oxalate, tartrate, formate, benzoate etc.) Organic acid salts and the like).
As higher fatty acids, stearic acid, lauric acid, oleic acid and the like or metal salts thereof (aluminum salt, zinc salt, magnesium salt, calcium salt, barium salt and the like) can be mentioned.
Examples of higher hydrocarbons include paraffin wax, polyethylene wax and the like, or derivatives thereof (perfluorinated compounds and the like).

In addition, if necessary, an inorganic compound may be coated on the surface of the above-mentioned zinc oxide particles. Examples of the inorganic compound include oxides such as silicon, titanium, aluminum, zirconium and tin, and inorganic compounds such as phosphates thereof. These inorganic compounds may be used alone or in combination of two or more.
The inorganic compound may be coated in place of the organic compound described above, or may be coated in addition to the organic compound (laminated on a multilayer of the organic compound). In the latter case, the order of coating of the organic compound and the inorganic compound does not matter, but considering the dispersibility in the solvent, the paint, the plastics, etc., the inorganic compound layer, the organic compound layer to the surface of the zinc oxide particles It is preferable to coat in the order of
The range of 0.1-50 mass% is preferable with respect to a zinc oxide particle, and, as for the coating amount of an inorganic compound and an organic compound, the range of 0.1-30 mass% is still more preferable.

The zinc oxide particles of the present invention can be produced, for example, by the following method. That is, a solution containing a zinc compound, a carboxylic acid and / or a salt thereof, and a basic compound is aged under hydrothermal conditions. Specifically, a zinc compound and a carboxylic acid and / or a salt thereof are mixed in water, a basic compound is added to the mixture, and the mixture is further aged under hydrothermal conditions.
As a zinc compound, it can select suitably and can be used, for example, zinc oxide, zinc chloride, zinc sulfate, zinc carbonate, zinc nitrate, zinc acetate etc. can be used. The carboxylic acid and / or the salt thereof can be appropriately selected and used, and preferred examples thereof include divalent carboxylic acids having one hydroxyl group such as malic acid and succinic acid and / or salts thereof, and more preferably Trivalent carboxylic acid having one hydroxyl group such as citric acid and / or a salt thereof, particularly preferably trisodium citrate dihydrate can be used. The basic compound can be appropriately selected and used, and examples thereof include alkali metal hydroxides such as sodium hydroxide, ammonia, ammonium compounds such as ammonium hydroxide, ammonium nitrate, ammonium nitrate and ammonium sulfate, and amines such as monoethanolamine and isopropanolamine Compounds, urea and the like can be used.

  For example, zinc sulfate is prepared as a zinc compound, sodium citrate is prepared as a carboxylate, these are weighed in a beaker, pure water is added, and the mixture is appropriately stirred. The amount of the zinc compound (zinc sulfate) is preferably in the range of 0.4 to 3 mol, more preferably in the range of 1 to 2 mol, per 100 ml of pure water. In addition, the amount of carboxylate (sodium citrate) is preferably in the range of 0.002 to 0.006 mol per 100 ml of pure water.

Subsequently, monoethanolamine is added as a basic compound to a mixed solution of a zinc compound (zinc sulfate), a carboxylate (sodium citrate) and pure water. A white precipitate can be obtained in solution by adding a basic compound (monoethanolamine). This white precipitate is presumed to be a precursor of the zinc oxide particles of the present invention.
It is preferable that the addition amount of the amine compound (monoethanolamine) as a basic compound is the range of 2-6 mol with respect to 1 mol of zinc compounds.

  Furthermore, the mixture after addition of the basic compound (monoethanolamine) is aged under hydrothermal conditions. It is thought that spherical zinc oxide particles are formed by the above-described precursors being accumulated and at the same time each precursor being converted to zinc oxide through the aging step.

“Aging under hydrothermal conditions” means aging at a temperature above the boiling point (100 ° C.) of water while applying a pressure above atmospheric pressure in a pressure resistant vessel. As a heating method, for example, a method of heating the reaction solution (the mixed solution) using heat transfer means such as a heater, an electric furnace, a steam jacket, a coil, etc. using electricity or steam as a heat source like an autoclave. A method of irradiating the reaction solution with microwaves and heating can be used. The treatment temperature under hydrothermal conditions is preferably in the range of 120 to 200 ° C., and it is preferable to carry out under pressure in a closed vessel at that temperature.
When using the heating method like an autoclave as a heating method of the said liquid mixture, it is preferable to make ripening time on hydrothermal conditions into 3 hours or more. If the aging time is less than 3 hours, spherical zinc oxide particles may not be obtained if the treatment temperature is too low. It is considered that this is because when the aging time is short, the accumulation of the above-described precursor does not proceed sufficiently, or the conversion from the precursor to zinc oxide is not completed. If the aging time is further extended, spherical zinc oxide particles can be obtained more reliably. However, it may be unacceptable to mature in hydrothermal conditions for too long, from the viewpoint of production and cost. Accordingly, the ripening time is preferably 20 hours or less, more preferably 15 hours or less.
When using microwave irradiation as a heating method of the said liquid mixture, it is thought that the above-mentioned ripening time can be shortened further.

The zinc oxide particles thus obtained are filtered, washed and dried. There is no particular limitation on the filtration means, and means such as gravity filtration, pressure filtration, vacuum filtration, suction filtration, centrifugal filtration, natural sedimentation and the like can be taken. Industrially, pressure filtration, vacuum filtration and suction filtration are preferable, and it is preferable to use a filter press such as a filter press or a roll press because the dewatering ability is high and a large amount of treatment can be performed. A band type heater, a batch type heater, a spray dryer, etc. can be used for drying. Although drying temperature can be set suitably, about 80-200 degreeC is appropriate.
After drying, it may be dry-ground if necessary. For dry pulverization, use is made of impact pulverizers such as hammer mills and pin mills, grinding pulverizers such as roller mills, pulper and disintegrators, compression crushers such as roll crushers and jaw crushers, and airflow crushers such as jet mills. be able to.

  Moreover, you may bake said zinc oxide particle as needed. The firing conditions are not particularly limited, but a firing temperature of 300 to 1500 ° C. and a firing time of about 10 minutes to 10 hours are appropriate. The firing may be carried out by stationary firing or in a rotary furnace. Stationary firing can be carried out in a mullite-made, mullite-cordierite bowl. The firing can usually be performed under an atmosphere of air, oxygen, nitrogen or the like. It may be performed under the flow of those gases. It is preferable to bake at 700-1200 degreeC, and, as for baking of a zinc oxide particle, it is more preferable to bake at the temperature of 850-1200 degreeC. As the firing temperature is higher, the crystallite diameter tends to be larger, and the thermal conductivity of the zinc oxide particles can be further enhanced.

  The zinc oxide particles may be classified for the purpose of removing the extremely coarse particles contained in the zinc oxide particles. Classification can be performed by grinding or sieving. The classification method by grinding is not particularly limited, and for example, an atomizer and the like can be mentioned. Wet classification, dry classification, etc. can be mentioned as a classification method by a sieve.

  In addition, when the surface of the above zinc oxide particles is to be coated with an inorganic compound and / or an organic compound, it may be coated by adding an inorganic compound or an organic compound in the aqueous slurry of zinc oxide particles and neutralizing it. it can. In addition, as another method for coating an organic compound, the coating may be performed by adding an organic compound to zinc oxide particles, performing dry treatment with a mixer, and performing heat treatment.

  The present invention can also be made into various compositions containing the above-mentioned zinc oxide particles. Specifically, embodiments of a resin composition containing zinc oxide particles, a grease, a cosmetic, a coating composition, and the like can be used. Such a resin composition may be a sheet, a gel, an elastomer, a plastic or the like formed using this.

The resin used in the resin composition of the present invention may be a thermoplastic resin or a thermosetting resin, and epoxy resin, acrylic resin, phenol resin, polyphenylene sulfide (PPS) resin, polyester resin, polyamide , Polyimide, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, fluorocarbon resin, polymethyl methacrylate, ethylene / ethyl acrylate copolymer (EEA) resin, polycarbonate, polyurethane, polyacetal, polyphenylene ether, polyetherimide And resins such as acrylonitrile-butadiene-styrene copolymer (ABS) resin, liquid crystal resin (LCP), and silicone resin.
The resin component of the resin composition can be appropriately selected according to the application. For example, when the resin composition is used for heat radiation, a resin having high adhesiveness, low hardness, and high heat resistance, such as an epoxy resin, a silicone resin, or an acrylic resin may be selected.

  The resin composition of the present invention comprises (1) a resin composition for thermoforming obtained by kneading a thermoplastic resin and the zinc oxide particles in a molten state, and (2) a thermosetting resin and the zinc oxide It may be any form such as a resin composition obtained by heat curing after kneading the particles.

  When the resin composition of the present invention is a resin composition for thermoforming, the resin composition is pelletized by melt-kneading the thermoplastic resin and the zinc oxide particles, for example, using a screw type twin-screw extruder, It can manufacture by the method etc. which are shape | molded by a desired shape by arbitrary shaping | molding methods, such as injection molding, after that.

  When the resin composition of the present invention is a resin composition obtained by heating and curing a thermosetting resin and the above-mentioned zinc oxide particles, the resin composition may be molded by, for example, pressure molding. preferable. Although the manufacturing method of such a resin composition is not specifically limited, For example, a resin composition can be shape | molded and manufactured by transfer molding.

  The compounding quantity of the said zinc oxide particle | grains in the resin composition of this invention can be arbitrarily determined according to the performance of a resin composition, such as the hardness of the target thermal conductivity and resin composition. In order to exhibit the heat dissipation performance of the said zinc oxide particle, it is preferable to contain 5 volume% or more with respect to solid content whole quantity in a resin composition. In applications where higher heat dissipation is required, 10% by volume or more is more preferable, 20% by volume or more is more preferable, and 40% by volume or more is the most preferable. Thus, the thermal conductivity of the resin composition can be 1.0 W / m · K or higher, preferably 2.0 W / m · K or higher, and more preferably 2.5 W / m · K. It can be m · K or more.

  Applications of the resin composition of the present invention include heat-radiating members for electronic parts, thermally conductive fillers, insulating fillers for temperature measurement and the like. For example, the resin composition of the present invention can be used to transfer the heat from a heat-generating electronic component such as an MPU (microprocessor), a power transistor, a transformer, etc. to a heat-radiating component such as a radiation fin or a radiation fan. , It can be used by being sandwiched between heat generating electronic components and heat dissipation components. As a result, the heat transfer between the heat generating electronic component and the heat radiating component is improved, and the malfunction of the heat generating electronic component can be reduced in the long run. It can also be suitably used to connect a heat pipe and a heat sink, and to connect a heat sink and a module incorporating various heating elements.

  The grease of the present invention is obtained, for example, by mixing the zinc oxide particles with a base oil containing a mineral oil or a synthetic oil.

  As the base oil, various oil materials such as mineral oil, synthetic oil, silicone oil, and fluorinated hydrocarbon oil can be used alone or in combination of two or more. In particular, hydrocarbon oils are preferred as synthetic oils. As synthetic oils, α-olefins, diesters, polyol esters, trimellitic acid esters, polyphenyl ethers, alkylphenyl ethers and the like can be used.

  The blending amount of the zinc oxide particles in the grease of the present invention can be arbitrarily determined in accordance with the target thermal conductivity. In order to exhibit the heat dissipation performance of the said zinc oxide particle, it is preferable to contain 1 volume% or more with respect to whole quantity in grease. In applications where higher heat dissipation is required, 5% by volume or more is more preferable, and 10% by volume or more is even more preferable.

  A surfactant may be added to the grease of the present invention as required. As said surfactant, a nonionic surfactant is preferable. The thermal conductivity can be increased by blending a nonionic surfactant.

  As nonionic surfactants, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl naphthyl ether, polyoxyethylene ethylated castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylamide, poly Oxyethylene-polyoxypropylene glycol, polyoxyethylene-polyoxypropylene glycol ethylenediamine, decaglycerin fatty acid ester, polyoxyethylene monofatty acid ester, polyoxyethylene difatty acid ester, polyoxyethylene propylene glycol fatty acid ester, polyoxyethylene sorbitan mono Fatty acid ester, polyoxyethylene sorbitan tri fatty acid ester, ethylene glycol mono fatty acid ester, die Glycol mono fatty acid esters, propylene glycol mono fatty acid esters, glycerol mono-fatty acid esters, pentaerythritol fatty acid monoesters, sorbitan mono fatty acid esters, Sorubitansesuki fatty esters, sorbitan tri fatty acid ester.

  The effect of the addition of the nonionic surfactant differs depending on the type and blending amount of the zinc oxide particles, and HLB (hydrophile-lipophile balance) which exhibits a balance between hydrophilicity and lipophilicity. In addition, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used in applications where importance is not placed on the electrical insulation and the reduction of the electrical resistance, such as highly heat dissipating greases.

  The grease of the present invention can be prepared by mixing the above-mentioned components using a mixing apparatus such as a dough mixer (kneader), a gate mixer, a planetary mixer and the like.

  The grease of the present invention is used by applying to a heat generating body or a heat radiating body. Examples of the heating element include general power sources; power devices for power sources, power modules, power modules, thermistors, thermocouples, electronic devices such as temperature sensors, and heat generating electronic components such as integrated circuits such as LSIs and CPUs. As a heat radiating body, heat radiating components, such as a heat spreader and a heat sink, heat pipe, a heat sink, etc. are mentioned, for example. Application can be performed, for example, by screen printing. Screen printing can be performed using, for example, a metal mask or screen mesh. Since heat can be efficiently conducted from the heat generating body to the heat radiating body by interposing and applying the grease between the heat generating body and the heat radiating body, heat can be effectively removed from the heat generating body. it can.

  The above-mentioned resin composition of the present invention may contain another heat-dissipating filler other than the zinc oxide particles of the present invention. The other heat dissipating filler is not particularly limited, and any known one can be used. For example, metal oxides such as zinc oxide, magnesium oxide, titanium oxide, aluminum oxide and zirconium oxide, aluminum nitride, boron nitride, silicon carbide, silicon nitride, titanium nitride, metal silicon, metal particles, carbon compounds (diamond, graphite, Graphene, carbon nanotubes, etc. can be mentioned. When combined with the zinc oxide particles of the present invention, the other heat dissipating filler is not limited to one type, and plural types of heat dissipating fillers may be used in combination.

  As the other heat dissipating filler, zinc oxide particles different in particle size from the zinc oxide particles of the present invention or heat dissipating fillers of other materials different in particle size may be used, and the median diameter is larger than the zinc oxide particles of the present invention Small small particle size heat dissipating fillers are preferred. In particular, a small particle size heat dissipating filler having a median diameter of R / 40 to R / 2 (R is the median diameter of the zinc oxide particles of the present invention) and zinc oxide particles of the present invention are used in the composition In addition, the voids between the zinc oxide particles of the present invention can be filled to increase the filler loading in the composition, and the composition can function like a lubricant to enhance the flowability of the composition. There is no restriction | limiting in particular in the other thermal radiation filler, Arbitrary materials can be used. Particularly preferred is zinc oxide and / or aluminum oxide. There is no restriction | limiting in particular in the compounding ratio of the zinc oxide particle of this invention, and another thermal radiation filler, What is necessary is just to adjust suitably, and the range of 7: 3-9: 1 is suitable by volume ratio. There is no particular limitation on the shape of the other heat radiation fillers, and spherical, granular, cubic, rod-like, hexagonal plate-like, scaly-like, indefinite shapes and the like can be mentioned. The other heat dissipating filler may be coated with an inorganic compound or an organic compound.

  The zinc oxide particles of the present invention are not limited to heat radiation applications, and may be used as ultraviolet light shielding materials, white pigments, fillers, etc. in various compositions (cosmetics such as sunscreen cosmetics and basic cosmetics, paints, and other resin compositions) Is also applicable. By so doing, zinc oxide particles can be blended into the composition at a high filling rate while maintaining the flowability of various compositions.

  When used in an appropriate amount, for example, in addition to the above-mentioned zinc oxide particles, well-known components used in cosmetics, such as (1) solvent (water, lower alcohols, etc.), (2) oil agent Higher fatty acids, higher alcohols, organopolysiloxanes (silicone oil), hydrocarbons, oils and fats, etc., (3) Surfactants (anionic, cationic, amphoteric, nonionic etc.), (4) Moisturizers (polyols such as glycerins and glycols, non-polyols such as pyrrolidone carboxylic acids) (5) Organic UV absorbers (benzophenone derivatives, para-aminobenzoic acid derivatives, salicylic acid derivatives etc), (6) antioxidants Phenolic, organic acids or their salts, acid amides, phosphoric acid etc), (7) thickeners, (8) perfumes, (9) coloring agents (pigments, dyes, dyes etc), (10) raw materials Active ingredient (vitamins, hormones, amino acids, etc.), (11) an antibacterial agent or the like may be blended. The form of the cosmetic is not particularly limited, and may be solid, liquid, gel, etc. When it is liquid or gel, its dispersion form may be any of water-in-oil type emulsion, oil-in-water type emulsion, oil type and the like. The blending amount of the zinc oxide particles in the cosmetic is preferably in the range of 0.1 to 50% by mass.

Moreover, when it mix | blends and uses it to a coating material, even if it has hardening property, resin which is used may not have hardening property. As resin, resin illustrated as resin which can be used in the resin composition mentioned above can be mentioned specifically. The paint may be a solvent-based paint containing an organic solvent or a water-based paint in which a resin is dissolved or dispersed in water.
It can manufacture by mixing and disperse | distributing the required raw material and solvent using the said coating material, for example, a disper, a bead mill, etc.

  The coating composition of the present invention can be used for the same applications as the heat dissipation member of electronic parts similar to the above-mentioned resin composition. In addition, it can be used for exterior walls of buildings, construction materials, industrial facilities that generate heat such as boilers, home appliances, and the like.

  EXAMPLES The present invention will be described in more detail by way of the following examples, but the present invention is not limited by these examples.

Example 1
0.3 mol of zinc sulfate heptahydrate and 0.001 mol of trisodium citrate dihydrate were mixed in 25 ml of pure water. While stirring at room temperature, 0.77 mol of monoethanolamine was added to obtain a white precipitate as a precursor.
The white precipitate was transferred to a pressure-resistant sealed container for hydrothermal treatment, allowed to stand in a constant temperature dryer DX 400 manufactured by Yamato Scientific Co., Ltd., and aged at 150 ° C. for 12 hours under hydrothermal conditions. The pressure-resistant sealed vessel was cooled to room temperature in ice water, and the sample in the vessel was suction filtered to recover a white precipitate. The recovered white precipitate was washed with pure water until the specific resistance of the filtrate was 1.0 × 10 ⁶ Ω · cm or less. After washing, it was allowed to stand still in a constant temperature dryer DX 400 manufactured by Yamato Scientific Co., Ltd. and dried at 150 ° C. for 3 hours. The data of the powder X-ray diffraction spectrum of the sample a after drying is shown in FIG. As a result of measurement of the X-ray diffraction pattern, it was confirmed that this sample a was a zinc oxide particle.
Further, this sample was calcined at 1100 ° C. for 2 hours to obtain Sample A. The scanning electron microscope (SEM) photograph of sample A (zinc oxide particles of Example 1) is shown in FIGS. Moreover, the scanning electron microscope (SEM) photograph of the cross section of the zinc oxide particle of sample A is shown in FIG.

The data of the powder X-ray diffraction spectrum was measured using a sample horizontal multipurpose X-ray diffractometer (Ultima IV manufactured by Rigaku Corporation). The detailed measurement conditions are as follows.
(1) Optical system (A) Entrance slit 1 °
(A) Longitudinal restriction slit 2 mm
(C) Light receiving slit 1 1 °
(D) With K beta filter (E) Photodetector slit 0.3 mm
(2) Measurement range: 5 to 50 deg
(3) Scanning method (a) Scanning speed 8.000 deg / min
(B) Step width 0.0200 deg
(4) Wavelength of X-ray CuKα ray 1.541 Å

Example 2
The white precipitate in the pressure-resistant sealed container is recovered by suction filtration and washed in the same manner as in Example 1 except that the aging time under hydrothermal conditions is changed from 12 hours to 3 hours based on Example 1 and washing. It was dry. From the result of measurement of the X-ray diffraction pattern of the sample after drying, it was confirmed that this sample is also a zinc oxide particle (data is omitted). Further, this sample was calcined at 1100 ° C. for 2 hours to obtain Sample B. A scanning electron microscope (SEM) photograph of Sample B (zinc oxide particles of Example 2) is shown in FIG.

Example 3
Sample A, which is a fired sample obtained in Example 1, was passed through a 330 mesh (32 μm mesh) vibrating sieve. Thus, a sample (sample C) from which coarse particles were removed from sample A was obtained. A scanning electron microscope (SEM) photograph of Sample C (zinc oxide particles of Example 3) is shown in FIG.

Comparative Example 1
First, re-pulp 600 g of zinc oxide (made by Hakusui Tech Co., Ltd.) in water, mix 3.50 mass% of dispersing agent (Paos 532A made by Kao) with respect to the mass of zinc oxide 1, and mix 0.61 mass% of acetic acid A slurry having a concentration of 600 g / l was prepared. Next, granulated particles were obtained by spray-drying the slurry with a spray dryer (L-8i, manufactured by Taigawara Kakoki Co., Ltd.). The product was put in a mortar made of mullite, mullite, cordierite, etc. and left to stand and fired at 1150 ° C. for 3 hours. The product was cooled, dispersed in 1.0 liter of water, passed through a 200-mesh (75 μm mesh) sieve, and the slurry passed through was filtered and dried to obtain Sample D. The scanning electron microscope (SEM) photograph of the sample D (the zinc oxide particle of the comparative example 1) is shown in FIG.

<Shape of zinc oxide particles>
As shown in FIGS. 2 to 6, all of the zinc oxide particles of Examples 1 to 3 are spherical particles, the particle surface is composed of a plurality of plate-like pieces, and the plate-like pieces are positioned little by little each other. It turns out that it accumulates in the mode which overlaps partially, shifting. More specifically, as shown in FIG. 3, the plate-like piece constituting the surface of the zinc oxide particle is, based on a hexagonal plate, at least a part of the corner or the side is missing, or the corner It can be seen that it has a smooth and smooth shape. Furthermore, as shown in FIG. 4, it can be seen that the zinc oxide particles of the example have a very densely packed inside.
Moreover, when the sphericity of each Example was measured by the above-mentioned method, the zinc oxide particles of Examples 1 and 2 had a sphericity of 1.1, and the zinc oxide particles of Example 3 had a sphericity of 1.2. there were.
On the other hand, as shown in FIG. 7, although the zinc oxide particles of Comparative Example 1 are spherical particles, the particle surface is not composed of a plurality of plate-like pieces. The zinc oxide particles of Comparative Example 1 are granules of zinc oxide particles, and it is considered that the individual small particles constituting the granules are formed into substantially spherical shapes by being fused together by firing.

<Particle diameter of zinc oxide particles>
The median diameter (D50) of the zinc oxide particles of the above-described Examples and Comparative Examples is shown in Table 1. The median diameter R was measured using a laser diffraction / scattering type particle size distribution measuring apparatus (Partica LA-950V2 manufactured by Horiba, Ltd.). Specifically, an aqueous solution in which 0.2% by mass of sodium hexametaphosphate is dissolved is used as a dispersion medium, each sample is mixed therein, and ultrasonic waves are irradiated for 3 minutes while circulating and stirring in the apparatus, and then particle size The distribution was measured. The particle diameter at which the cumulative frequency in the particle size distribution is 50% was taken as the median diameter (D50).

<Inclusion of coarse particles>
In the zinc oxide particles of Example 3 described above, based on the measurement result of the particle size distribution described above, D90 is a particle diameter at which the cumulative frequency in the particle size distribution is 90%, and D90 serves as an indicator of the amount of coarse particles mixed. As a result of measuring / D50, it was found that the mixing amount of coarse particles was small because it was 1.5.

<Characteristics evaluation of resin composition>
The performance (flowability, heat conductivity) of the resin composition which mix | blended this was evaluated using the zinc oxide particle of the above-mentioned Example and comparative example.

  First, 0.5% by mass of epoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) is added to the sample C obtained in the above-mentioned Example 3 and dry processing is performed by a mixer, and it is performed at 150 ° C. for 3 hours It was heat treated to give an organic compound coating. In addition, 1.0% by mass of epoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) is added to a small particle size filler (a zinc oxide particle manufactured by Haxuitec Co., Ltd., median diameter 0.5 μm), and the same as above. The organic compound coating was applied by the procedure. The sample C coated with the organic compound and the small particle size filler were mixed at a volume ratio of 8: 2, to obtain a sample C1.

  In the same manner as in the sample D of the comparative example 1, the sample D coated with the organic compound and the small particle size filler were mixed at a volume ratio of 8: 2, to obtain a sample D1.

Next, using the sample C1, a resin composition for flowability evaluation was produced as follows. First, a resin (jER (registered trademark)-807: bisphenol F-type epoxy resin, manufactured by Mitsubishi Chemical Corporation) and a sample C1 were weighed in a screw bottle and kneaded for 3 minutes at 2000 rpm. Subsequently, the mixture was defoamed by kneading at 1000 rpm for 1 minute to prepare a liquid resin composition for flowability evaluation. The compound (40% by volume, 45% by volume, 55% by volume) of the compounding amount (filling ratio) of the sample C1 with respect to the total solid content in the resin composition was prepared. The mixing ratio of each is as shown in Table 2.
Hereinafter, the resin composition produced using the sample C1 is referred to as a resin composition of Example 3.

With respect to this resin composition, the viscosity of the resin composition was measured using a viscosity / viscoelasticity measurement apparatus (HAAKE RheoStress 6000, manufactured by Thermo Scientific Co., Ltd.). The measurement was performed under the following conditions, a resin composition of about 0.5 ml was placed on a cone, and the viscosity at each rotation speed was measured. For the evaluation of fluidity, the value of viscosity at 1 rpm was used for comparison.
Cone: MP-20, C20 / 1H
Measurement temperature: 25 ° C
Gap: 0.052 mm
Number of rotations: 1, 2, 5, 10, 20 rpm

  The viscosity of the resin composition for flowability evaluation of Example 3 is shown in Table 2. Even when the filling rate is set high (filling rate 55% by volume), practically sufficient viscosity (less than 300 Pa · s) can be obtained. On the other hand, by lowering the filling rate (filling rate 40% by volume), the viscosity of the resin composition can be greatly reduced to about 30 Pa · s, so that a resin composition with particularly good handleability is realized. Can.

Moreover, the pellet for thermal conductivity measurement was produced as follows using C1 and D1. First, an amine curing agent (Jeffamine (registered trademark) EDR-148, manufactured by Huntsman, USA) was weighed into a screw bottle together with a resin (jER (registered trademark)-807) and a sample C1 (or sample D1). Thereafter, kneading and degassing were performed in the same manner as in the preparation of the resin composition for flowability evaluation, to prepare a resin composition. The compounding quantity (filling rate) of sample C1 (or sample D1) with respect to solid content whole quantity in a resin composition prepared the thing of 40 volume%, 45 volume%, 55 volume%. The blending ratio of each is as shown in Table 3.
The resin composition was poured into a circular mold and allowed to stand overnight, and then heated and solidified at 100 ° C. for 3 hours to prepare a solid thermal conductivity measurement pellet.
In the following, the above-mentioned pellet produced using sample C1 is made into the pellet of Example 3, and the above-mentioned pellet produced using sample D1 is made the pellet of Comparative Example 1.

The thermal conductivity was measured by the following method using the above-mentioned pellet for thermal conductivity measurement. First, the pellet for thermal conductivity measurement was polished to a thickness of about 1 mm to obtain a sample for evaluation. The thermal diffusivity of the sample for evaluation was measured by a laser flash method in an atmosphere temperature of 25 ° C. using a thermal diffusivity evaluation device (TC-7000, manufactured by ULVAC, Inc.) according to JIS R 1611. Moreover, based on JISK7123, the specific heat capacity of the said pellet was measured by DSC (differential scanning calorimetry DSC6200 SII make). Furthermore, in accordance with JIS K 7112, the specific gravity of the above pellet was measured by a water substitution method. Based on the values of the thermal diffusivity, the specific heat capacity, and the specific gravity obtained by the above method, the thermal conductivity was calculated by the following equation. The thermal conductivity of the pellets for thermal conductivity measurement of Example 3 and Comparative Example 1 is shown in Table 3.
Thermal conductivity = thermal diffusivity x specific heat capacity x specific gravity

  As apparent from Table 3, focusing on the case where the filling rate is set high (loading rate 55% by volume), the thermal conductivity of the resin composition (pellets) of Comparative Example 1 is about 3.1 W / m · K. On the other hand, the thermal conductivity of the resin composition (pellet) of Example 3 is a high thermal conductivity of 3.6 W / m · K or more. Thus, it has been found that the zinc oxide particles of the present invention can achieve high thermal conductivity.

  Further, focusing on the case where the filling rate is set low (for example, the filling rate of 40% by volume), the thermal conductivity of the resin composition (pellets) of Comparative Example 1 is about 1.5 W / m · K, It was found that the thermal conductivity of the resin composition (pellet) of Example 3 can still maintain a relatively high thermal conductivity of about 2.1 W / m · K.

  The zinc oxide particles of the present invention are excellent in thermal conductivity. For this reason, when it mixes with resin etc. and it is set as a heat dissipation composition (a resin composition, a grease, etc.), since a heat dissipation composition with high heat conductivity is obtained while having sufficient fluidity for practical use, a heat radiation filler Etc. are useful as various fillers such as Moreover, since it has fluidity | liquidity and filling property practically sufficient by mix | blending the zinc oxide particle | grains of this invention, it is used also for uses, such as a cosmetics, a coating composition, and a resin composition.

Claims (11)

  Spherical zinc oxide particles having an outer shell formed by accumulating a plurality of zinc oxide platelets so as to partially overlap.   The zinc oxide particles according to claim 1, wherein the plate-like piece is a hexagonal plate-like.   The zinc oxide particles according to claim 1 or 2, wherein the median diameter is 15 to 30 μm.   The zinc oxide particles according to any one of claims 1 to 3, wherein D90 / D50 is 1.5 or less.   The zinc oxide particles according to any one of claims 1 to 4, which have an organic compound coating and / or an inorganic compound coating on the surface.   The resin composition containing the zinc oxide particle in any one of Claims 1-5.   The resin composition according to claim 6, comprising a small particle size heat radiation filler having a median diameter smaller than that of the zinc oxide particles.   A grease comprising the zinc oxide particles according to any one of claims 1 to 5.   A cosmetic comprising the zinc oxide particles according to any one of claims 1 to 5.   A paint composition comprising the zinc oxide particles according to any one of claims 1 to 5.   A method for producing zinc oxide particles, wherein a solution containing a zinc compound, a carboxylic acid and / or a salt thereof, and a basic compound is aged under hydrothermal conditions.

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