Method for producing inorganic metal oxide powder containing coated particles

Abstract

Provided is a method for producing an inorganic metal oxide powder containing surface-coated particles (coated particles), wherein the amount of increase in the BET specific surface area of the inorganic metal oxide powder finally obtained is small relative to the BET specific surface area of the raw material powder and the fluidity is less likely to decrease when filling a resin.　A method for producing an inorganic metal oxide powder (I) containing coated particles (X), wherein the production method includes spraying a raw material inorganic metal oxide powder (A) with a slurry (C) containing a coating component (B), coating by a rolling fluidized bed, and firing to obtain an inorganic metal oxide powder (I) containing coated particles (X), and the ratio ((Si) / (Sa)) of the BET specific surface area (Si) of the inorganic metal oxide powder (I) to the BET specific surface area (Sa) of the inorganic metal oxide powder (A) is 5.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a method for producing inorganic metal oxide powders containing coated particles. [Background technology]

[0002] In fields such as semiconductor encapsulation, inorganic metal oxide powders such as silica and alumina are used as fillers to improve the coefficient of thermal expansion, thermal conductivity, and flame retardancy. Silica has a relatively low thermal conductivity, and alumina has a higher thermal conductivity than silica, but its hardness is also high, making the equipment it is used in prone to wear. Therefore, magnesium oxide powder, which has a higher thermal conductivity than silica and alumina but is also less hard than alumina, is being considered as a filler applicable to the above fields.

[0003] It is known that magnesium oxide has low moisture resistance and reacts with moisture in the air to form magnesium hydroxide. As the content of magnesium hydroxide increases, the thermal conductivity tends to decrease, so efforts have been made to improve moisture resistance by coating the surface of magnesium oxide particles (e.g., Patent Documents 1 and 2).

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-34523 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-74683 Summary of the Invention

[0005] In conventional methods for producing coated inorganic metal oxide powders, the specific surface area of ​​the powder can increase due to the coating. This is due to the fact that the shape and surface smoothness of the particles constituting the powder change as a result of the coating. However, if the BET specific surface area increases significantly compared to before coating, it can become difficult to obtain the desired physical properties. Furthermore, since fillers for inorganic metal oxide powders are generally used by filling them into resins, if the specific surface area becomes too large, there are problems such as a decrease in fillability and dispersibility in the resin, which impairs fluidity and makes handling difficult.

[0006] Therefore, an object of the present invention is to provide a method for producing an inorganic metal oxide powder containing coated particles, which method has a small increase in the BET specific surface area of ​​the final inorganic metal oxide powder relative to the BET specific surface area of ​​the raw material powder, and is less likely to reduce flowability when filled into a resin.

[0007] As a result of extensive research, the present inventors have discovered that a manufacturing method that includes coating the raw material inorganic metal oxide powder with tumbling fluidized bed coating can solve all of the above-mentioned problems, and have thus completed the present invention. That is, the present invention has the following aspects. [1] A method for producing an inorganic metal oxide powder (I) containing coated particles (X), the method comprising spraying a slurry (C) containing a coating component (B) onto a raw material inorganic metal oxide powder (A) to perform tumbling fluidized bed coating, followed by firing to obtain an inorganic metal oxide powder (I) containing coated particles (X), wherein the ratio ((Si) / (Sa)) of the BET specific surface area (Si) of the inorganic metal oxide powder (I) to the BET specific surface area (Sa) of the inorganic metal oxide powder (A) is 5.0 or less. [2] The method according to [1], wherein the firing temperature is 500 to 1600°C. [3] The method according to [1] or [2], wherein the firing time is 0.1 to 12 hours. [4] The manufacturing method according to any one of [1] to [3], wherein the spraying of the slurry (C) onto the inorganic metal oxide powder (A) is carried out in such a manner that the ratio of the coating component (B) to the total amount (100% by mass) of the inorganic metal oxide powder (A) and the coating component (B) is 1 to 25% by mass. [5] The manufacturing method according to any one of [1] to [4], wherein the inorganic metal oxide powder (A) has a median diameter (Da50) of 10 to 150 μm, and the inorganic metal oxide powder (I) has a median diameter (Di50) of 11 to 300 μm. [6] The method according to any one of [1] to [5], wherein the (Si) / (Sa) ratio is 0.5 or more. [7] The method according to any one of [1] to [6], wherein the coating component (B) contains an inorganic metal oxide powder (B1). [8] The method according to any one of [1] to [7], wherein the coated particles (X) comprise core-shell particles. [9] The manufacturing method according to any one of [1] to [8], wherein the inorganic metal oxide powder (A) comprises an inorganic metal oxide powder or an inorganic metal double oxide powder containing at least one element selected from titanium, aluminum, magnesium, silicon, and calcium.

[10] The manufacturing method according to any one of [1] to [9], wherein the inorganic metal oxide powder (A) contains magnesium oxide powder, the coating component (B) contains at least one inorganic metal oxide powder (B1) selected from alumina powder and silica powder, and the coated particles (X) contain particles in which the surface of a core particle containing magnesium oxide is coated with a coating layer.

[11] The manufacturing method according to

[10] , wherein the coating layer contains at least one selected from Al2O3, MgO-Al2O3 composite oxide, SiO2, and MgO-SiO2 composite oxide.

[0008] According to the present invention, a method for producing an inorganic metal oxide powder containing coated particles can be provided, in which the increase in the BET specific surface area of ​​the final inorganic metal oxide powder relative to the BET specific surface area of ​​the raw material powder is small, and the flowability is less likely to decrease when filled into a resin. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. When a specific explanation given for one embodiment also applies to other embodiments, that explanation may be omitted in other embodiments. In this specification, the expression "α to β" indicating a numerical range means "above α and below β." Furthermore, in this specification, "powder" means "an aggregate of particles."

[0010] [Method for producing inorganic metal oxide powder (I) containing coated particles (X)] The present embodiment relates to a method for producing an inorganic metal oxide powder (I) containing coated particles (X), which comprises spraying a slurry (C) containing a coating component (B) onto a raw material inorganic metal oxide powder (A) to perform tumbling fluidized bed coating, followed by calcination to obtain an inorganic metal oxide powder (I) containing coated particles (X), wherein the ratio ((Si) / (Sa)) of the BET specific surface area (Si) of the inorganic metal oxide powder (I) to the BET specific surface area (Sa) of the inorganic metal oxide powder (A) is 5.0 or less. The production method according to the present embodiment enables the production of an inorganic metal oxide powder (I) in which the increase in the BET specific surface area of ​​the final inorganic metal oxide powder relative to the BET specific surface area of ​​the raw material powder is small, and which is less likely to reduce flowability when filled into a resin.

[0011] The inorganic metal oxide powder (I) containing coated particles (X) (hereinafter sometimes referred to as "powder (I)") obtained by the production method according to this embodiment has a small increase in the BET specific surface area of ​​the final inorganic metal oxide powder (I) relative to the BET specific surface area of ​​the raw inorganic metal oxide powder (A). In this embodiment, the increase in specific surface area before and after coating is expressed as the BET specific surface area (Si) of the inorganic metal oxide powder (I) relative to the BET specific surface area (Sa) of the raw inorganic metal oxide powder (A) ((Si) / (Sa)). According to the production method according to this embodiment, it is possible to keep (Si) / (Sa) to 5.0 or less. The closer (Si) / (Sa) is to 1.0, the smaller the change in BET specific surface area between the raw inorganic metal oxide powder (A) (hereinafter sometimes referred to as "raw powder (A)") and the powder (I).

[0012] The increase in BET specific surface area due to coating is caused by a change in the shape of the particles constituting the powder, a decrease in the surface smoothness of the particles (i.e., an increase in surface roughness), etc. The production method according to this embodiment makes it easy to suppress the decrease in the surface smoothness of the particles due to coating, thereby making it possible to make the value of (Si) / (Sa) 5.0 or less.

[0013] In one embodiment, the lower limit of (Si) / (Sa) may be 0.5 or more. That is, (Si) / (Sa) may be in the range of 0.5 to 5.0. When (Si) / (Sa) is less than 1.0, the BET specific surface area (Si) of powder (I) is smaller than the BET specific surface area (Sa) of raw material powder (A). One known method for producing coated powders involves immersing the raw powder in an aqueous solution containing the coating components and then calcining the resulting powder to coat it. This method has proven extremely difficult to minimize the increase in the BET specific surface area of ​​the coated powder, and even to make the specific surface area of ​​the coated powder smaller than that of the raw powder. This is because, in these methods, the raw powder and coating components are mixed in a liquid, filtered, and then the resulting cake layer is crushed and calcined to obtain the coated powder. However, it is extremely difficult to achieve a uniform and smooth coating of the coating components on the surface of the raw powder after crushing. The production method of this embodiment utilizes tumbling fluidized bed coating, which enables uniform and dense coating of each particle constituting the raw powder (A). This eliminates the need for a crushing step as in conventional methods, thereby minimizing the increase in the specific surface area of ​​the powder (I). Therefore, the production method of this embodiment also allows the ratio (Si) / (Sa) to be adjusted to less than 1.0. In a preferred embodiment, (Si) / (Sa) may be 0.5 to 4.0, 0.5 to 3.0, or 0.5 to 2.0. (Sa) and (Si) can be measured under the following conditions. (Method for measuring BET specific surface area) 5 g of raw material powder (A) (or powder (I)) is filled into the measurement cell of a fully automatic specific surface area measurement device (BET single-point method) (for example, Mountech's Macsorb HM model-1201 fully automatic specific surface area measurement device), and the specific surface area is measured. The degassing conditions before measurement are 200°C and 10 minutes. Helium is used as the carrier gas, and nitrogen (mixed concentration: 30.5%) is used as the adsorption gas.

[0014] <Raw material inorganic metal oxide powder (A)> In the manufacturing method according to this embodiment, the raw material powder (A) is not particularly limited as long as it is an inorganic metal oxide powder. The term "inorganic metal oxide" refers to a compound in which a metal element is bonded to oxygen. In this embodiment, the raw material powder (A) may be an inorganic metal oxide powder suitable for use in the field of semiconductor encapsulation materials, but is not limited thereto. Examples of inorganic metal oxide powders suitable for use in the field of encapsulation materials include inorganic metal oxide powders or inorganic metal double oxide powders containing at least one element selected from titanium, aluminum, magnesium, silicon, and calcium. "Inorganic metal double oxide" refers to a higher-order oxide composed of an oxide containing two or more metal ions. The raw material powder (A) preferably contains the inorganic metal oxide powder or inorganic metal double oxide powder described above. Among these, from the viewpoint of obtaining powder (I) with good thermal conductivity, the raw material powder (A) preferably contains an inorganic metal oxide powder or inorganic metal double oxide powder containing at least one element selected from aluminum and magnesium, and more preferably contains magnesium oxide powder. In one embodiment, the raw material powder (A) may be composed solely of magnesium oxide powder.

[0015] (Magnesium oxide powder) When the raw material powder (A) contains magnesium oxide powder, the purity of the magnesium oxide powder is not particularly limited and is preferably determined depending on the application. For example, when the powder (I) obtained by the production method according to this embodiment is used as a filler for a semiconductor encapsulation material, it is preferable to use magnesium oxide powder with a purity of 90% or more, and more preferably to use magnesium oxide powder with a purity of 95% or more. Furthermore, magnesium oxide powder produced by a conventionally known method, such as an electric melting method or a sintering method, can be used.

[0016] In one embodiment, the periclase crystallite size of the magnesium oxide powder is 50×10 -9 The crystallite size is preferably 50 × 10 -9Magnesium oxide powder with a particle size of 0.01m or more tends to have good thermal conductivity. Note that "crystallite size" refers to the value calculated using the Scherrer formula using X-ray diffraction. When the particles are polycrystalline, the crystallite size indicates the average size of the single crystals in the polycrystalline body.

[0017] (Physical properties of raw material powder (A)) In one embodiment, the BET specific surface area (Sa) of the raw material powder (A) is 0.01 to 20 m from the viewpoint of fluidity. 2 / g, and may be 0.01 to 10m 2 / g, and may be 0.01 to 1m 2 / g.

[0018] In one embodiment, the median diameter (Da50) of the raw material powder (A) may be 10 to 150 μm, 20 to 140 μm, 40 to 130 μm, or 45 to 120 μm from the viewpoint of fluidity. When the median diameter (Da50) of the raw material powder (A) is within the above range, the change in specific surface area tends to be small when the powder is coated by tumbling fluidized bed coating. In this specification, the term "median diameter (D50)" refers to the particle diameter corresponding to the 50% cumulative value in the volume-based cumulative particle size distribution measured using a laser diffraction particle size analyzer (e.g., Beckman Coulter, Inc., product name "LS 13 320" or Microtrackbell, Inc., product name "MT3300EXII"). The cumulative particle size distribution is represented by a distribution curve with particle diameter (μm) on the horizontal axis and cumulative value (%) on the vertical axis.

[0019] The average circularity (ARa) of the raw material powder (A) is not particularly limited. In one embodiment, from the viewpoint of fillability into a resin, the average circularity (ARa) may be 0.70 or more, 0.80 or more, or 0.90 or more. The average circularity can be measured by the following method. (Method for measuring average circularity) The raw powder (A) (or powder (I)) is fixed with carbon tape and then coated with osmium. Then, the particles are photographed at a magnification of 200 to 50,000 times using a scanning electron microscope (e.g., manufactured by JEOL Ltd., product name "JSM-7001F SHL"), and the projected area (A) of the particles is calculated using an image analyzer (e.g., manufactured by Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3"). p ) and projected perimeter (L), and then calculate the circularity using the following formula (1). The circularity is calculated for any 200 particles, and the average value is taken as the average circularity. Circularity = 4πA p / L 2 ···(1)

[0020] Conventional manufacturing methods involving wet coating are susceptible to the surface condition of the raw material particles. When raw material powder containing particles with low surface smoothness (high surface roughness) is used, the proportion of uncoated portions may increase, which tends to increase the specific surface area of ​​the resulting powder. According to the manufacturing method of this embodiment, even when raw material powder (A) contains particles with relatively low surface smoothness, coated particles (X) that are substantially free of uncoated portions are easily obtained. The surface smoothness (surface roughness) of the particles contained in raw material powder (A) or powder (I) can be evaluated by methods such as shape observation using a scanning electron microscope.

[0021] In one embodiment, the average particle density of the raw material powder (A) is 0.1 to 7.0 g / cm from the viewpoint of easily obtaining suitable powder fluidity in the tumbling fluidized bed coating process. 3 and may be 0.5 to 5.5 g / cm 3 The average particle density can be measured by the following method. (Method for measuring average particle density) 2.0 g of raw material powder (A) (or powder (I)) is placed in a measurement sample cell of a dry density meter (for example, Shimadzu Corporation, product name "Accupyk II 1340"), and the average particle density is measured by the gas (helium) substitution method.

[0022] In one embodiment, the raw material powder (A) may be surface-treated with a surface treatment agent. In the production method according to this embodiment, the raw material powder (A) is coated by tumbling fluidized bed coating, and therefore is less susceptible to the surface condition of the raw material powder (A) than conventional wet coating methods. Therefore, surface-treated raw material powder (A) can also be used. Examples of surface treatment agents include silane coupling agents and aluminate coupling agents. These agents may be used alone or in combination of two or more. The presence or absence of surface treatment of the raw material powder (A) can be confirmed by analyzing the raw material powder (A) using, for example, IR, TG-DTA, mass spectrometry, or the like.

[0023] <Slurry (C) containing coating component (B)> The manufacturing method according to this embodiment involves spraying a slurry (C) containing a coating component (B) onto a raw inorganic metal oxide powder (A) to perform tumbling fluidized bed coating, followed by firing. The coating component (B) contained in the slurry (C) may be either a component capable of reacting with the raw powder (A) to form a coating layer on the surfaces of the particles constituting the raw powder (A) (hereinafter sometimes referred to as "raw material particles (A)"), or a component capable of forming a coating layer without reacting with the raw material particles (A). From the viewpoint of facilitating the formation of a uniform and continuous coating layer, a component capable of reacting with the raw material particles (A) to form a coating layer on the surfaces of the raw material particles (A) is preferred.

[0024] The coating component (B) capable of reacting with the raw material particles (A) is not particularly limited as long as it has the effects of the present invention. In one embodiment, the coating component (B) preferably contains an inorganic metal oxide powder (B1). The inorganic metal oxide powder (B1) contained in the coating component (B) is not particularly limited as long as it can react with the raw material particles (A), and examples thereof include inorganic metal oxide powders such as alumina, silica, and titania. These may be used alone or in combination of two or more.

[0025] In a preferred embodiment, when the coating component (B) contains an inorganic metal oxide powder (B1) (hereinafter, sometimes referred to as "powder (B1)"), the median diameter (Db150) of the powder (B1) is preferably 1 to 10,000 nm, more preferably 10 to 1,000 nm. In one embodiment, the ratio ((Db150) / (Da50)) of the average particle diameter (Db150) of the powder (B1) to the median diameter (Da50) of the raw material powder (A) is 8.0 × 10 -6 ~1.0×10 -1 may be 5.0 x 10 -5 ~5.0×10 -2 If ((Db150) / (Da50)) is within the above range, the surfaces of the raw material particles (A) can be more efficiently coated with the coating component (B) containing the powder (B1).

[0026] In one embodiment, when the coating component (B) contains an inorganic metal oxide powder (B1) and the raw material powder (A) contains magnesium oxide powder, the inorganic metal oxide powder (B1) preferably contains at least one inorganic metal oxide powder selected from alumina (Al2O3) powder and silica (SiO2) powder, and more preferably contains alumina powder. In this case, the coated particles (X) contained in the resulting powder (I) preferably contain particles in which the surface of a core particle containing magnesium oxide is coated with a coating layer. Furthermore, the coating layer preferably contains at least one selected from Al2O3, MgO-Al2O3 composite oxide, SiO2, and MgO-SiO2 composite oxide. When magnesium oxide powder is used as raw powder (A) and coated with inorganic metal oxide powder (B1) such as alumina, the coated particles (X) preferably comprise core-shell particles, since this facilitates improving the moisture resistance of the resulting powder (I). In this case, the coated particles (X) more preferably comprise core-shell particles in which the surface of a magnesium oxide-containing core particle is coated with a coating layer containing at least one selected from the aforementioned Al2O3, MgO-Al2O3 composite oxide, SiO2, and MgO-SiO2 composite oxide. Furthermore, the coating layer of the core-shell particle preferably contains MgO-Al2O3 composite oxide, more preferably MgAl2O4.

[0027] In one embodiment, the content of the coating component (B) in the slurry (C) may be 0.1 to 80 mass % or 1 to 50 mass % relative to the total mass of the slurry (C). When the content of the coating component (B) is within the above range, the amount of the coating component (B) sprayed onto the raw material powder (A) can be easily adjusted to a preferred range described below.

[0028] The dispersion medium in the slurry (C) preferably contains water or ethanol, more preferably water. The slurry (C) may contain other components in addition to the coating component (B) and the dispersion medium. Examples of other components include a dispersant and a binder.

[0029] In one embodiment, the amount of coating component (B) sprayed onto raw material powder (A) is preferably 1 to 25 mass% relative to the total amount (100 mass%) of raw material powder (A) and coating component (B), from the viewpoint of easier control of the (Si) / (Sa) value. That is, spraying of slurry (C) onto raw material powder (A) may be performed so that the proportion of coating component (B) relative to the total amount (100 mass%) of raw material powder (A) and coating component (B) is 1 to 25 mass%. In other embodiments, from the viewpoint of easier production of core-shell particles, the amount of coating component (B) sprayed may be 1 mass% or more and less than 25 mass%, 1 to 20 mass%, 1 mass% or more and less than 20 mass%, 1 to 18 mass%, or 5 to 20 mass%, relative to the total amount (100 mass%) of raw material powder (A) and coating component (B).

[0030] <Tumbling fluidized bed coating> The manufacturing method according to this embodiment involves spraying the aforementioned slurry (C) onto raw powder (A) to perform tumbling fluidized bed coating. Tumbling fluidized bed coating, also known as tumbling fluidized bed coating or tumbling fluidized bed granulation coating, is a coating technique using a coating device equipped with a blade rotor at the bottom of a typical fluidized bed device. The present inventors have discovered that by spraying a slurry (C) containing coating components (B) onto raw powder (A) using tumbling fluidized bed coating to produce powder (I) containing coated particles (X), it is possible to suppress the increase in BET specific surface area due to coating and control the (Si) / (Sa) ratio to 5.0 or less. Furthermore, they have discovered that tumbling fluidized bed coating can efficiently coat the surfaces of raw material particles (A).

[0031] In one embodiment, the tumbling fluidized bed coating may be carried out under conditions of 20 to 150°C, 30 to 100°C, or 50 to 90°C. The coating time is not particularly limited as long as it is a time that allows the surfaces of the raw material particles (A) to be sufficiently coated. From the viewpoint of forming a uniform coating layer, the coating time may be 0.01 to 24 hours, 0.05 to 24 hours, or 0.1 to 12 hours.

[0032] The tumbling fluidized bed coating can be carried out using a conventionally known tumbling fluidized bed apparatus, such as the "Tumbling Fluidized Granulation Coating Apparatus MP (Multiplex)" manufactured by Powrex Corporation.

[0033] <Firing> The production method according to this embodiment includes calcining the raw material powder (A) after the tumbling fluidized bed coating. From the viewpoint of forming a uniform coating layer, the calcination temperature is preferably 500 to 1600°C, more preferably 700 to 1600°C, even more preferably 1000 to 1600°C, and particularly preferably 1000 to 1400°C. In one embodiment, the calcination temperature may be higher than 1000°C and not higher than 1600°C, or may be 1100 to 1500°C. From the viewpoint of forming a uniform coating layer, the calcination time is preferably 0.1 to 12 hours, more preferably 0.5 to 10 hours, even more preferably 1 to 10 hours, and particularly preferably 1 to 8 hours.

[0034] <Other processes> After the firing step, the resulting coated powder (A) may be in the form of aggregates. Therefore, a crushing treatment may be carried out as necessary. The crushing method is preferably carried out under conditions that make it difficult for the BET specific surface area (Si) of the powder (I) to change, and for example, a mortar, a bead mill, a ball mill, etc. can be used.

[0035] In one embodiment, after firing the raw material powder (A), the obtained powder (I) may be classified by sieving, air classification, etc. By classifying the powder (I), it becomes easier to control the (Si) / (Sa) ratio to 5.0 or less.

[0036] [Inorganic metal oxide powder (I)] The production method according to this embodiment makes it possible to prepare an inorganic metal oxide powder (I) containing coated particles (X).

[0037] <Coated particles (X)> The coated particles (X) obtained by the production method according to this embodiment refer to particles having at least a portion of their surface coated with the coating component (B). In a preferred embodiment, the coated particles (X) preferably comprise core-shell particles having substantially no uncoated portions on their surfaces. In one embodiment, the coated particles (X) are preferably core-shell particles. The term "core-shell particles" refers to coated particles having a large portion of their surface coated. Whether the coated particle (X) is a core-shell particle can be determined, for example, by observing that in a cross-sectional image of the coated particle (X) obtained by a field emission scanning electron microscope (e.g., Carl Zeiss, product name "MERLIN, FE-SEM") and an energy dispersive X-ray spectroscopy (e.g., Bruker, product name "QUANTAX System XFlash6 / 60SDD, EDS"), the ratio (rc / ra) of the cross-sectional perimeter ra of the inorganic metal oxide particle (A) (raw material particle (A)) that forms the core portion to the perimeter rc of the portion of the cross-section of the raw material particle (A) that is coated with the coating component (B) is 0.6 or more, indicating that the majority of the core particle is coated with a coating layer (i.e., the particle is a core-shell particle).

[0038] By coating raw powder (A) with coating component (B) using the aforementioned method including tumbling fluidized bed coating, coated particles (X) can be obtained in which at least a portion of the surface of the particles (raw particles (A)) constituting the raw powder (A) is coated with coating component (B). Coated particles (X) containing core-shell particles can be easily obtained by adjusting the spray amount of the aforementioned coating component (B), adjusting the firing temperature and firing time, etc. For example, when magnesium oxide powder is used as raw powder (A) and the magnesium oxide powder (A) is coated with coating component (B) containing alumina powder, core-shell particles can be easily obtained by setting the spray amount of coating component (B) to 1 to 20 mass% (equivalent to alumina powder) based on the total amount (100 mass%) of the magnesium oxide powder (A) and coating component (B), or by setting the firing temperature to more than 1000°C and not more than 1600°C. Such magnesium oxide powder (I) containing core-shell particles also tends to have good moisture resistance.

[0039] In one embodiment, the proportion of the coated particles (X) in the powder (I) is preferably 80% or more, more preferably 90% or more, from the viewpoint of easily controlling (Si) / (Sa) to 5.0 or less. In one embodiment, the powder (I) may contain particles other than the coated particles (X). Examples of the other particles include uncoated inorganic metal oxide powder (A) and particles of inorganic metal oxides or inorganic metal double oxides derived from the coating component (B). These may be contained alone or in combination of two or more.

[0040] In one embodiment, the raw material powder (A) has a BET specific surface area (Sa) of 0.01 to 10 m 2 When an inorganic metal oxide powder having a specific surface area of ​​1000 nm / g is used, the BET specific surface area (Si) of the powder (I) is in a range where (Si) / (Sa) is 5.0 or less, and preferably 0.015 to 25 m 2 / g, more preferably 0.02 to 20m 2 / g.

[0041] In one embodiment, when an inorganic metal oxide powder having a median diameter (Da50) of 10 to 150 μm is used as raw material powder (A), the median diameter (Di50) of powder (I) is preferably 11 to 300 μm, more preferably 11 to 200 μm, and even more preferably 11 to 180 μm.

[0042] In one embodiment, when the raw material powder (A) has an average circularity (ARa) of 0.75 or more, the average circularity (ARi) of the powder (I) is preferably 0.75 or more, more preferably 0.80 or more.

[0043] In one embodiment, the thickness of the coating layer, calculated as the difference ((Di50)-(Da50)) between the median diameter (Di50) of the powder (I) containing the coated particles (X) and the median diameter (Da50) of the raw material powder (A), may be 40 μm or less or 35 μm or less from the viewpoint of maintaining high thermal conductivity. From the viewpoint of easily obtaining a resin composition with lower viscosity and good flowability when filled into a resin, the thickness may be 30 μm or less or 26 μm or less.

[0044] Powders obtained by coating raw material particles using conventional coating methods, such as wet coating, tend to have a low average circularity when raw material powders with a low average circularity are used. Furthermore, when raw material powders with a low average circularity are used for coating, the resulting powders tend to have a large amount of uncoated particles. Increasing the amount of coating to reduce the uncoated particles or increase the average circularity of the coated powder can lead to problems such as difficulty in obtaining the desired median diameter (D50) or a decrease in thermal conductivity when used as a filler. The powder (I) obtained by the production method according to this embodiment is likely to have a high average circularity (ARi) even when raw material powder (A) with a low average circularity (ARa) is used. Furthermore, because the entire particles can be coated with a relatively small amount of coating, thermal conductivity is less likely to decrease.

[0045] <Magnesium oxide powder> When the surface of raw material powder (A) containing magnesium oxide powder is coated with alumina, silica, or the like, the powder (I) obtained by the production method according to this embodiment has high thermal conductivity and excellent moisture resistance. In one embodiment, the thermal conductivity of magnesium oxide powder (I) obtained by the production method according to this embodiment, measured under the following conditions, may be 4.0 to 8.0 W / mK, or may be 5.0 to 7.0 W / mK. (Measurement conditions) A mixed powder is prepared by mixing magnesium oxide powder and spherical alumina powder (e.g., manufactured by Denka Co., Ltd., product names "DAW-07" or "ASFP-40") in a volume ratio of 51:49. The mixed powder is then filled into a silicone resin (e.g., manufactured by Shin-Etsu Chemical Co., Ltd., product names "SE1885:A" or "SE1885:B") so that the mixed powder accounts for 77.5% by volume, to prepare an evaluation sheet. The evaluation sheet is measured using a thermal resistance measuring device (e.g., manufactured by Hitachi Technology and Services, Ltd., product name "TRM-046RHHT") to determine its thermal conductivity.

[0046] Furthermore, the magnesium hydroxide content of the magnesium oxide powder (I) after conducting tests under the following conditions is preferably less than 50% by mass, more preferably 30% by mass or less, and even more preferably 10% by mass or less. The magnesium oxide powder (I) obtained by the production method according to this embodiment has excellent moisture resistance and is therefore less likely to produce magnesium hydroxide. (Conditions for measuring magnesium hydroxide content after test) 10 g (M1) of inorganic metal oxide powder (I) is left standing for 168 hours in a highly accelerated life tester (for example, Espec Corp., product name "Highly Accelerated Life Tester EHS-212M" under unsaturated mode) at a temperature of 135°C and a humidity of 85%RH. The mass (M2) of inorganic metal oxide powder (I) after standing is measured, and the change in mass before and after standing is substituted into the following formula (2) to calculate the magnesium hydroxide content. {(M2-M1) / 18.0}×(40.3 / M1)×100 ···(2) (In formula (2), M1 is the mass (g) of the inorganic metal oxide powder (I) before standing, M2 is the mass (g) of the inorganic metal oxide powder (I) after standing, and 18.0 and 40.3 are the molecular weights of HO and MgO, respectively.)

[0047] [Application] The powder (I) obtained by the production method according to this embodiment has a small increase in the BET specific surface area of ​​the final inorganic metal oxide powder relative to the BET specific surface area of ​​the raw material powder, and therefore is less likely to lose fluidity when filled into a resin. Furthermore, when the powder (I) is a magnesium oxide powder, it has excellent moisture resistance and good thermal conductivity. Such powder (I) can be suitably used as a filler for resins.

[0048] [Resin composition] The resin composition according to this embodiment contains the powder (I) prepared by the above-described production method and at least one resin selected from thermoplastic resins and thermosetting resins. The content of the powder (I) in the resin composition is not particularly limited and can be adjusted appropriately depending on the purpose. For example, when used as an encapsulant, the content may be in the range of 1 to 99 mass % relative to the total mass of the resin composition, and more preferably in the range of 10 to 90 mass %.

[0049] <Resin> The resin composition according to the present embodiment includes at least one resin selected from thermoplastic resins and thermosetting resins. More specifically, examples of the resin include polyethylene resins, polypropylene resins, epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyester resins, fluororesins, polyamide-based resins such as polyimide resins, polyamide-imide resins, and polyetherimide resins, polyester-based resins such as polybutylene terephthalate resins and polyethylene terephthalate resins, polyphenylene sulfide resins, wholly aromatic polyester resins, polysulfone resins, liquid crystal polymer resins, polyethersulfone resins, polycarbonate resins, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, hydrocarbon-based elastomer resins, polyphenylene ether resins, and aromatic polyene-based resins. These may be used alone or in combination of two or more.

[0050] The resin composition according to this embodiment may contain a curing agent, a curing accelerator, a release agent, a coupling agent, a colorant, a flame retardant, an ion scavenger, etc., within the range that does not impair the effects of the present invention.

[0051] <Method of manufacturing resin composition> The method for producing the resin composition is not particularly limited, and the resin composition can be produced by stirring, dissolving, mixing, and dispersing predetermined amounts of each material. The apparatus for mixing, stirring, dispersing, etc., of these mixtures is not particularly limited, and examples that can be used include a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, and a planetary mixer. These apparatuses may also be used in appropriate combination.

[0052] As described above, the resin composition containing the coated powder (A) has excellent fluidity and is therefore easy to handle.

[0053] A more preferred aspect of this embodiment is as follows. <1> A method for producing a magnesium oxide powder (I) containing coated particles (X), comprising: The production method includes spraying a slurry containing at least one coating component (B) selected from alumina powder and silica powder onto a raw material magnesium oxide powder (A) to perform tumbling fluidized bed coating, followed by firing the resulting material to obtain a magnesium oxide powder containing coated particles (X); The ratio of the coating component (B) sprayed on the magnesium oxide powder (A) is 1% by mass or more and less than 25% by mass with respect to the total amount (100% by mass) of the magnesium oxide powder (A) and the coating component (B), A production method in which the ratio of the BET specific surface area (Si) of the magnesium oxide powder (I) to the BET specific surface area (Sa) of the magnesium oxide powder (A) ((Si) / (Sa)) is 5.0 or less. <2> the coating component (B) contains alumina powder, and the ratio of the alumina powder sprayed on the magnesium oxide powder (A) is 1 to 20 mass% with respect to the total amount (100 mass%) of the magnesium oxide powder (A) and the coating component (B); <1> The manufacturing method described in <3> The firing temperature is more than 1000°C and less than 1600°C. <1> or <2> The manufacturing method described in <4> The coated particles (X) comprise core-shell particles in which the surface of a core particle containing magnesium oxide is coated with a coating layer containing at least one selected from Al2O3, an MgO-Al2O3 composite oxide, SiO2, and an MgO-SiO2 composite oxide. <1> from <3> 1. The manufacturing method according to any one of the preceding claims. <5> The slurry is sprayed onto the magnesium oxide powder (A) so that the thickness of the coating layer of the coated particles (X) becomes 30 μm or less. <1> from <4> 1. The manufacturing method according to any one of the preceding claims. [Example]

[0054] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0055] [Example 1] As the raw material powder (A), magnesium oxide powder (manufactured by Denka Co., Ltd., product name "DMG-50", median diameter (Da50): 50 μm, BET specific surface area (Sa): 0.2 m) was used. 2 Magnesium oxide powder (A) was coated with a slurry (C) containing alumina powder (coating component (B), product name "CAB-O-SPERSE PG008" manufactured by Cabot Specialty Chemicals, Inc., median diameter (Db150): 100 nm) using a tumbling fluidized bed coating method. The slurry (C) was sprayed onto the magnesium oxide powder (A) in an amount such that the ratio of coating component (B) to the total amount (100 mass%) of magnesium oxide powder (A) and coating component (B) was 7 mass% (magnesium oxide powder (A) 93 mass%, coating component (B) 7 mass% (alumina powder equivalent)). The magnesium oxide powder (I) was then calcined at 1300°C for 1 hour to obtain powder (I). The Si, median diameter (Di50), average circularity, and presence or absence of coated particles (X) of the resulting powder (I) were measured under the following conditions. The physical properties of raw powder (A) were measured under the same conditions as those of powder (I). The thickness of the coating layer was calculated from the difference between the median diameter (Da50) of raw powder (A) and the median diameter (Di50) of powder (I). As a result of these measurements, powder (I) of Example 1 contained coated particles (X), and the (Si) / (Sa) ratio was 0.70.

[0056] (Method for measuring BET specific surface area (Sa) and (Si)) 5 g of raw material powder (A) (or powder (I)) was filled into the measurement cell of a fully automatic specific surface area measurement device (BET single-point method) (Mountech Macsorb HM model-1201 fully automatic specific surface area measurement device), and the specific surface area was measured. The degassing conditions before the measurement were 200°C and 10 minutes. Helium was used as the carrier gas, and nitrogen (mixed concentration: 30.5%) was used as the adsorption gas.

[0057] (Method for measuring median diameter (D50)) The median diameter (D50) of the powder was determined by measuring the volumetric particle size distribution using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name "LS 13 320"). Specifically, a 50 cm 3 100g of pure water and 0.1g of raw material powder (A) (or powder (I)) were added, and the mixture was dispersed for 60 seconds at 25W output using an ultrasonic homogenizer (Microtec Nichion Co., Ltd., product name "Smurt NR-50M (titanium alloy tip φ3 (NS-50M-MT3))"). The dispersed raw material powder (A) (or powder (I)) dispersion was added dropwise to the laser diffraction particle size analyzer using a dropper, and measurements were taken 30 seconds after the specified amount was added. The refractive index of water was 1.33, and the refractive index of MgO powder was 1.74. The median diameter (D50) was calculated from the particle diameter corresponding to the 50% cumulative value in the volume-based cumulative particle size distribution of the particle diameters being measured.

[0058] (average circularity) The raw powder (A) (or powder (I)) is fixed with carbon tape and then coated with osmium. Then, the particles are photographed at a magnification of 200 to 50,000 times using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7001F SHL"), and the projected area (A) of the particles is calculated using an image analyzer (for example, manufactured by Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3"). p After calculating the diameter (mm) and projected perimeter (L), the circularity was calculated using the following formula (1): The circularity was calculated for 200 randomly selected particles, and the average value was taken as the average circularity. Circularity = 4πA p / L 2 ···(1)

[0059] <Presence or absence of coated particles (X) and core-shell particles> The powder (I) obtained in Example 1 was observed with a scanning electron microscope (JEOL Ltd., JSM-7001F) to confirm the presence or absence of coated particles (X). Furthermore, cross-sectional images of the powder (I) were obtained using a field-emission scanning electron microscope (Carl Zeiss, MERLIN, FE-SEM) and an energy-dispersive X-ray spectroscopy (Bruker, QUANTAX System XFlash6 / 60SDD, EDS). The ratio of the cross-sectional perimeter ra of the coated particle to the perimeter rc of the portion of the coated particle covered with the coating component (B) was calculated (rc / ra), confirming the presence or absence of core-shell particles. The measurements were performed at an image acquisition magnification of 1000x, a voltage of 10 kV, a current of 500 nA, and a measurement time of 30 seconds. Elemental mapping of aluminum and magnesium was also performed. Image analysis was performed using ImageJ, and for each particle image, ra was the perimeter of the magnesium component mapping area, which forms the core, and rc was the perimeter of the area surrounding the magnesium component that is in contact with the aluminum component, which forms the shell (it was determined to be "in contact" if the area one pixel outside the magnesium component was the mapping area of ​​the aluminum component), and rc / ra was calculated; particles with rc / ra of 0.6 or greater were determined to be core-shell particles. The results are shown in Table 1.

[0060] <Liquidity evaluation> A resin composition was prepared from the powder (I) obtained in Example 1 under the following conditions. A resin composition was prepared by mixing 60% by volume of a bisphenol A liquid epoxy resin (epoxy equivalent: 184 to 194, manufactured by Mitsubishi Chemical Corporation, product name "JER828") and 40% by volume of the powder (I) and kneading the mixture with a planetary mixer (manufactured by Thinky Corporation, product name "Awatori Rentaro (registered trademark) AR-250", rotation speed: 2000 rpm).

[0061] Next, the viscosity of the obtained resin composition at 25°C was measured under the following conditions. In addition, it was evaluated according to the following evaluation criteria, and a rating of "fair" or better was considered to be acceptable (good fluidity). The results are shown in Table 1. The viscosity of the resulting resin composition at 25° C. was measured under the following conditions using a rotational rheometer (manufactured by Anton Paar, product name "MCR-302"). Plate shape: circular flat plate 10mmφ Sample thickness: 1 mm Temperature: 25±1℃ Shear rate: 1.0 / s (Evaluation criteria) Excellent: Viscosity of resin composition is 500 Pa·s / 25°C or less. Good: Viscosity of the resin composition is more than 500 Pa·s / 25°C and 1,000 Pa·s / 25°C or less. Acceptable: Viscosity of resin composition is over 1,000 Pa·s / 25°C and up to 2,000 Pa·s / 25°C. Not permitted: Viscosity of resin composition exceeds 2,000 Pa·s / 25°C.

[0062] <Thermal conductivity evaluation> The thermal conductivity of powder (I) from Example 1 was evaluated when used as a filler. First, powder (I) and spherical alumina powder (manufactured by Denka Co., Ltd., a mixture of product names "DAW-07" and "ASFP-40"; (DAW-07) / (ASFP-40) = 70 / 30 (volume ratio)) were mixed in a volume ratio of 51:49 to prepare a mixed powder. The mixed powder was then filled into silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., a mixture of product names "SE1885:A" and "SE1885:B"; (SE1885:A) / (SE1885:B) = 50 / 50 (volume ratio)) so that the mixed powder ratio was 77.5% by volume. The mixture was then mixed using a mixer equipped with a stirring blade to obtain a resin composition. The resin composition was molded using a sheet coater to obtain a 3-mm-thick evaluation sheet. The thermal conductivity of the evaluation sheet was measured using a thermal resistance measuring device (manufactured by Hitachi Technology and Services, Ltd., product name "TRM-046RHHT") The results are shown in Table 1.

[0063] [Examples 2 to 9] Powder (I) was prepared in the same manner as in Example 1, except that the raw powder (A) and coating conditions were as shown in Table 1. For each example of powder (I) and raw powder (A), evaluations of (Sa), (Si), median diameter (D50), average circularity, presence or absence of coated particles (X), thickness of the coating layer, fluidity, and thermal conductivity were performed under the same conditions as in Example 1. The results are shown in Table 1. The silica powder used in Examples 8 and 9 was manufactured by Cabot Specialty Chemicals, Inc., product name "CAB-O-SPERSE 2017A" (median diameter (Db1): 100 nm).

[0064] [Comparative Example 1] As raw material powder (A), magnesium oxide powder (manufactured by Denka Co., Ltd., product name "DMG-50", median diameter (Da50): 50 μm, BET specific surface area (Si): 0.2 m) was used. 2 The magnesium oxide powder (A) was wet-coated by immersing it in an alumina slurry (coating component (B), manufactured by Cabot Specialty Chemicals, Inc., product name "PG008", median diameter (Db150): 100 nm) using an alumina slurry (coating component (B) of 0.1g / g, average circularity (ARa): 0.93) for 1 hour, and then fired at 1300°C for 2 hours. The physical properties of the obtained powder were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0065] [Table 1]

[0066] As shown in Table 1, the powders (I) of Examples 1 to 9 obtained by the production method according to this embodiment had (Si) / (Sa) ratios of 5.0 or less. The resin compositions filled with the powders (I) of these Examples had viscosities of 2,000 Pa·s or less at 25°C and good fluidity. On the other hand, the resin composition filled with the powder of Comparative Example 1 coated by wet coating had a viscosity of more than 2,000 Pa·s at 25°C and poor fluidity. From the above results, it was confirmed that the inorganic metal oxide powder (I) obtained by the production method according to this embodiment has a small increase in the BET specific surface area of ​​the final inorganic metal oxide powder relative to the BET specific surface area of ​​the raw material powder, and is less likely to experience a decrease in fluidity when filled into a resin. [Industrial Applicability]

[0067] The manufacturing method according to the present embodiment can provide an inorganic metal oxide powder containing coated particles that is less likely to lose flowability when filled into a resin. A resin composition containing such a powder can be used as a ceramic filler for semiconductor encapsulation and the like.

Claims

1. A method for producing an inorganic metal oxide powder (I) containing coated particles (X), comprising: The production method includes spraying a slurry (C) containing a coating component (B) onto a raw material inorganic metal oxide powder (A) to perform tumbling fluidized bed coating, followed by firing at 700 to 1600°C to obtain an inorganic metal oxide powder (I) containing coated particles (X); A method for producing an inorganic metal oxide powder (I), wherein the ratio ((Si) / (Sa)) of the BET specific surface area (Si) of the inorganic metal oxide powder (I) to the BET specific surface area (Sa) of the inorganic metal oxide powder (A) is 5.0 or less.

2. The method according to claim 1, wherein the firing time is 0.1 to 12 hours.

3. 3. The method according to claim 1, wherein the slurry (C) is sprayed onto the inorganic metal oxide powder (A) in such a manner that the ratio of the coating component (B) to the total amount (100% by mass) of the inorganic metal oxide powder (A) and the coating component (B) is 1 to 25% by mass.

4. The inorganic metal oxide powder (A) has a median diameter (Da50) of 10 to 150 μm, The method according to claim 1 or 2, wherein the inorganic metal oxide powder (I) has a median diameter (Di50) of 11 to 300 μm.

5. The method according to claim 1 or 2, wherein the (Si) / (Sa) ratio is 0.5 or more.

6. The method according to claim 1 or 2, wherein the coating component (B) comprises an inorganic metal oxide powder (B1).

7. The method according to claim 1 or 2, wherein the coated particles (X) comprise core-shell particles.

8. 3. The method according to claim 1, wherein the inorganic metal oxide powder (A) comprises an inorganic metal oxide powder or an inorganic metal double oxide powder containing at least one element selected from titanium, aluminum, magnesium, silicon, and calcium.

9. The inorganic metal oxide powder (A) contains magnesium oxide powder, The coating component (B) contains at least one inorganic metal oxide powder (B1) selected from alumina powder and silica powder, The method according to claim 1 or 2, wherein the coated particles (X) comprise particles in which the surface of a core particle containing magnesium oxide is coated with a coating layer.

10. The coating layer is Al ２ O ３ , MgO-Al ２ O ３ Complex oxide, SiO ２ , and MgO—SiO ２ The method according to claim 9 , wherein the oxide comprises at least one selected from the group consisting of composite oxides.

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