JP6971110B2 - A method for producing a coated particle powder, and a method for producing a dispersion containing the coated particle powder and a dispersion medium. - Google Patents

Description

The present invention relates to a method for producing a coated particle powder and a method for producing a dispersion containing the coated particle powder and a dispersion medium.

In recent years, particulate materials such as inorganic particles, organic particles, and metal particles have been used for various purposes including polishing compositions and high-temperature structural members. For example, inorganic particles such as silicon carbide (SiC) have high hardness, are excellent in high temperature heat resistance, mechanical strength, impact resistance, wear resistance, oxidation resistance and corrosion resistance, and have a small coefficient of thermal expansion. There are great expectations for its application.

In the application of particulate matter, in forming a desired composition or material, the particulate material may be dispersed in a dispersion medium or a polymer material medium, or mixed with other materials such as ceramic particles. It is being considered for use. Further, in order to improve the functions of dispersions and mixtures containing particulate matter, and molded bodies formed from these, the surroundings of the constituent particles are coated with a compound capable of imparting a desired function, and then dispersed and mixed. Is being considered. From this, a particulate material having high dispersibility in a medium and capable of uniform mixing with other materials in a state where the surroundings are coated with a compound capable of imparting a desired function is particularly desired.

As such a technique, for example, in Patent Document 1, the surface of the SiC powder is coated with an oxide film of alumina or the like having a thickness of 10 nm to 500 nm provided by firing to obtain the SiC powder. It is disclosed that the insulation property can be improved. Further, it is disclosed that the heat resistance, high thermal conductivity and high insulating property of the composite composition can be realized by containing such SiC powder.

Japanese Unexamined Patent Publication No. 2012-106888

However, in the technique according to Patent Document 1, sufficient dispersibility of the powder in the medium cannot be obtained.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a means for producing a coated particle powder capable of imparting high dispersibility when dispersed in a medium.

In order to solve the above problems, the present inventors have accumulated diligent research. As a result, in the method for producing powder containing coated particles, an appropriate raw material particle is selected, an appropriate compound is selected as a raw material for the coated component, and the raw material for the coated component, the raw material particles, and water are contained. It has been found that the above-mentioned problems can be solved by having a step of spray-drying the raw material dispersion, and the present invention has been completed.

That is, the above problem of the present invention is solved by the following means;
A step (A) of spray-drying a raw material dispersion containing a raw material particle composed of an oxide, a carbide, a nitride, a metal or an organic substance, a water-soluble metal salt, and water to obtain a particle aggregate (a).
The step (B) of heat-treating the particle aggregate (a) at a temperature of 300 ° C. or higher and 750 ° C. or lower to obtain the particle aggregate (b).
The step (C) of obtaining the coated particles (c) by pulverizing the particle aggregate (b), and
A method for producing a coated particle powder.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a means for producing a coated particle powder capable of imparting high dispersibility when dispersed in a medium.

It is a graph which shows the particle size distribution of the SiC particle which is a raw material particle, the coated particle powder which concerns on one Embodiment of this invention, and the powder which concerns on a comparative example.

Hereinafter, the present invention will be described. The present invention is not limited to the following embodiments.

In the present specification, "X to Y" indicating a range means "X or more and Y or less". Further, in the present specification, unless otherwise specified, the operation and the measurement of physical properties are performed under the conditions of room temperature (20 to 25 ° C.) / relative humidity of 40 to 50% RH.

<Powder manufacturing method>
One embodiment of the present invention is a step of spray-drying a raw material dispersion containing particles composed of oxides, carbides, nitrides, metals or organic substances, a water-soluble metal salt, and water to obtain a particle aggregate (a). (A) and
The step (B) of heat-treating the particle aggregate (a) at a temperature of 300 ° C. or higher and 750 ° C. or lower to obtain the particle aggregate (b).
The step (C) of obtaining the coated particles (c) by pulverizing the particle aggregate (b), and
The present invention relates to a method for producing a coated particle powder.

The present inventors presume the mechanism by which the above-mentioned problems are solved by the present invention as follows.

The coated particles as described in Patent Document 1 are produced by mixing raw material particles and raw materials of components (coating components) contained in the coating layer in a dispersion medium, filtering, drying, and then firing. In such a production method, agglomeration of the coated particles proceeds at the same time as the formation of the coated particles at the time of firing to form an agglomerate (coated particle aggregate). For example, in the production of alumina-coated particles according to Patent Document 1, agglomeration of particles forming SiC powder progresses when the alumina-coated particle precursor is heated during firing. As a result, the coated particles produced by such a manufacturing method have a significantly increased degree of aggregation as compared with the raw material particles, and the difference in the degree of individual aggregation also increases accordingly, so that the particle size varies. The increase in is also remarkable. It is difficult to obtain a dispersion having high dispersibility in such a coated particle powder not only when it is dispersed in a medium as it is, but also when it is dispersed in a medium after being pulverized.

On the other hand, the coated particles contained in the powder produced by the production method according to one embodiment of the present invention use water-soluble metal salts as raw materials for the components (coated components) contained in the coated layer, and are water-soluble with the raw material particles. It is formed by spray-drying, heat-treating, and pulverizing a raw material dispersion containing a metal salt and water. Further, in the coating layer formed by the method, the combination of the raw material of the coating component and the raw material particles is optimized, and the raw material of the coating component adheres to the surface of the raw material particles by the spray dry method. Then, in the production method, a part of the water-soluble metal salt which is a raw material of the coating component is changed to a component such as graphite at the time of firing, and this component such as graphite functions as a release agent, so that the coating of adjacent coated particles is coated. Bonding between layers is greatly suppressed. Further, in the manufacturing method, the strength of the formed coated particle aggregate is also significantly reduced. Therefore, it is easily crushed when the subsequent particle aggregate is crushed, and the coated particle powder is produced while maintaining the low cohesiveness of the raw material particles. Therefore, even if the powder composed of the particles is dispersed in the medium as it is, a dispersion having high dispersibility can be obtained.

The above mechanism is based on speculation, and its correctness does not affect the technical scope of the present invention.

In the production method according to one embodiment of the present invention, coated particles are produced.

(Step (A))
In the method for producing coated particle powder according to the present invention, raw material particles composed of oxides, carbides, nitrides, metals or organic substances, a water-soluble metal salt, and a raw material dispersion containing water are spray-dried to form particles. It has a step (A) of obtaining an aggregate (a). In this step, it is considered that the particle aggregate (a) containing the raw material particles coated with the water-soluble metal salt which is the raw material of the coating component is formed by the spray-drying method.

[Preparation method for raw material dispersion]
The raw material dispersion contains raw material particles, a water-soluble metal salt, and water.

The method for preparing the raw material dispersion containing the raw material particles, the water-soluble metal salt, and water is not particularly limited, and for example, a method of adding the water-soluble metal salt to the raw material particles and the dispersion containing water, water-soluble. A method of adding raw material particles to an aqueous solution of a metal salt, a method of adding raw material particles and a water-soluble metal salt to a dispersion medium containing water, a method of mixing a dispersion containing raw material particles and water with an aqueous solution of a water-soluble metal salt. And so on. Among these, a method of adding raw material particles to an aqueous solution of a water-soluble metal salt is preferable.

Here, the aqueous solution of the dispersion containing the raw material particles and water and the water-soluble metal salt may be a commercially available product or a synthetic product, respectively. When synthesizing (preparing) these, a known device and a known method can be used without particular limitation.

[Raw material particles]
The raw material particles according to the present invention are raw material particles of the coated particles contained in the produced coated particle powder, and generally determine the characteristics of the coated particle powder. The raw material particles according to the present invention are made of oxides, carbides, nitrides, metals or organic substances.

The particles made of oxide are not particularly limited, and examples thereof include silica particles, alumina particles, ceria particles, titania particles, magnesia particles, and beryllia particles. The particles made of carbide are not particularly limited, and examples thereof include silicon carbide (SiC) particles and the like. The particles made of nitride are not particularly limited, and examples thereof include silicon nitride (SiN), boron nitride (BN), and aluminum nitride (AlN) particles. The particles made of metal are not particularly limited, and examples thereof include nickel particles, copper particles, silver particles, and gold particles. The particles made of an organic substance are not particularly limited, and examples thereof include latex particles, polystyrene particles, polymethyl methacrylate (PMMA) particles, polyester particles, polyimide particles, epoxy particles, graphite particles and the like. Further, as the particles made of oxide, carbide or nitride, particles made of oxide nitride, particles made of carbide or the like may be used. Among these, oxides, carbides or nitrides are high in hardness, excellent in high temperature heat resistance, mechanical strength, impact resistance, abrasion resistance, oxidation resistance and corrosion resistance, and have a small coefficient of thermal expansion. Particles made of carbon are preferred, particles made of carbide are more preferred, and SiC particles are even more preferred.

The average primary particle size of the raw material particles is preferably 3000 nm or less. When the average primary particle size is in this range, a dispersion having higher dispersibility can be obtained when the coated particle powder is dispersed in the medium. From the same viewpoint, the average primary particle size of the raw material particles is more preferably 1000 nm or less, and further preferably 300 nm or less. Further, the average primary particle size of the raw material particles is preferably 10 nm or more. When the average primary particle size is in this range, the occurrence of reaggregation after dispersion is further suppressed, and it becomes easier to maintain the dispersed state. From the same viewpoint, the average primary particle size of the raw material particles is more preferably 50 nm or more, further preferably 100 nm or more. Here, the value of the average primary particle diameter of the raw material particles is the value of the true density of the raw material particles based on the average value of the specific surface area (SA) of the raw material particles calculated from the values measured 3 to 5 times continuously by the BET method. Can be calculated by assuming that the shape of the raw material particles is a true sphere. The specific surface area of the raw material particles can be measured, for example, by using Flow SorbII 2300 manufactured by Micromeritex. The details of the measurement method will be described in Examples.

The average secondary particle size of the raw material particles is preferably 10,000 nm or less. When the average secondary particle size is in this range, a dispersion having higher dispersibility can be obtained when the coated particle powder is dispersed in the medium. From the same viewpoint, the average secondary particle size of the raw material particles is preferably 5000 nm or less, and more preferably 1500 nm or less. Further, the average two particle diameter of the raw material particles is preferably 10 nm or more. When the average secondary particle size is in this range, the raw material particles can be coated with high efficiency. From the same viewpoint, the average secondary particle size of the raw material particles is more preferably 50 nm or more, further preferably 100 nm or more. Here, the value of the average secondary particle size of the raw material particles can be measured by the scattering type particle size distribution measuring device LA-950 manufactured by HORIBA, Ltd. The details of the measurement method will be described in Examples.

The average secondary particle size represents the particle size measured in the presence of particles at the time of measurement, regardless of whether the particles are single particles or aggregated particles.

Further, as the raw material particles, a commercially available product or a synthetic product may be used. The commercially available product is not particularly limited, but for example, GC # 40,000, GC8,000S and the like manufactured by Fujimi Incorporated Co., Ltd. can be used.

The raw material particles may be used alone, in combination thereof, or in combination of two or more.

The content of the raw material particles in the raw material dispersion is not particularly limited, but is preferably 10% by mass or more with respect to the total mass of the raw material dispersion. This is because when the content of the raw material particles is within this range, the production efficiency of the coated particle powder can be improved. From the same viewpoint, the content of the raw material particles is more preferably 15% by mass or more, further preferably 20% by mass or more, and particularly preferably 30% by mass or more with respect to the total mass of the raw material dispersion. The content of the raw material particles in the raw material dispersion is not particularly limited, but is preferably 60% by mass or less with respect to the total mass of the raw material dispersion. When the content of the raw material particles is in this range, the increase in viscosity is further suppressed, and the raw material particles can be more stably supplied into the spray dryer device. From the same viewpoint, the content of the raw material particles in the raw material dispersion is more preferably 55% by mass or less, still more preferably 50% by mass or less, based on the total mass of the raw material dispersion.

[Water-soluble metal salt]
The water-soluble metal salt is a raw material for a coating component contained in a coating layer of coated particles contained in the coated particle powder produced in the production method according to the present invention, and can impart a desired function to the powder. Is.

The water-soluble metal salt is not particularly limited, and a known water-soluble metal salt can be appropriately selected and used depending on the coating property on the raw material particles and the function imparted to the powder.

The type of metal in the water-soluble metal salt is not particularly limited, and examples thereof include alkali metals such as sodium and potassium, group 2 elements such as calcium and magnesium, aluminum and yttrium. Among these, aluminum and yttrium are preferable, and aluminum is more preferable when imparting functionality as a sintering aid.

The type of salt in the water-soluble metal salt is not particularly limited, but is, for example, salts of inorganic acids such as carbonic acid, hydrochloric acid, nitrate and sulfuric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid and enanthic acid. , Caprilic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, naphthenic acid, arachidonic acid, docosahexaenoic acid, eikosapentaenoic acid, lactic acid, apple Acids, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, merit acid, sucrose, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, Examples thereof include salts of organic acids such as carboxylic acids such as aconitic acid, amino acids, anthranyl acid and nitrocarboxylic acid. Among these, a salt of an organic acid is preferable, and a lactate is more preferable.

The specific water-soluble metal salt is not particularly limited, but for example, calcium chloride, calcium nitrate, calcium sulfate, calcium lactate, magnesium chloride, magnesium sulfate, magnesium sulfate, magnesium lactate, aluminum chloride, aluminum nitrate, aluminum sulfate, etc. Examples thereof include aluminum lactate, yttrium chloride, yttrium nitrate, yttrium sulfate, and yttrium lactate. Among these, aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum lactate, yttrium chloride, yttrium nitrate, yttrium sulfate, yttrium lactate and the like are preferable, aluminum lactate and yttrium lactate are more preferable, and aluminum lactate is even more preferable. Further, as the water-soluble metal salt, a commercially available product or a synthetic product may be used.

The content of the water-soluble metal salt in the raw material dispersion is not particularly limited, but is preferably 0.1% by mass or more with respect to the total mass of the raw material dispersion. When the content of the water-soluble metal salt is in this range, the raw material particles can be more reliably coated with the coating component, and the function derived from the coating component is further improved. Further, in the dispersion including the coated particle powder and the dispersion, aggregation is less likely to occur even when the powder and other particles described later are used in combination. Therefore, it is possible to produce a dispersion having higher dispersibility. From the same viewpoint, the content of the water-soluble metal salt in the raw material dispersion is more preferably 0.5% by mass or more, still more preferably 1% by mass or more, based on the total mass of the raw material dispersion. The content of the water-soluble metal salt in the raw material dispersion is not particularly limited, but is preferably 50% by mass or less with respect to the total mass of the raw material dispersion. When the content of the water-soluble metal salt is in this range, the effect obtained by the coating becomes constant after the coating progresses to some extent. Therefore, by setting the addition amount of the water-soluble metal salt to a predetermined amount or less, economic efficiency and production can be achieved. This is because the efficiency is further improved. From the same viewpoint, the content of the water-soluble metal salt in the raw material dispersion is more preferably 40% by mass or less, further preferably 30% by mass or less, and further preferably 20% by mass or less, based on the total mass of the raw material dispersion. Even more preferably, 10% by mass or less is particularly preferable.

[Dispersion medium]
The raw material dispersion contains water as a dispersion medium. Water makes it possible to apply the spray-drying method by dispersing the raw material particles and dissolving the water-soluble metal salt.

The water is preferably water containing as little impurities as possible. For example, water having a total content of transition metal ions of 100 ppb or less is preferable. Here, the purity of water can be increased by, for example, operations such as removal of impurity ions using an ion exchange resin, removal of foreign substances by a filter, distillation and the like. Specifically, as the water, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water and the like are preferably used.

The procedure and method for dispersing the raw material particles in water and the procedure and method for dissolving the water-soluble metal salt are not particularly limited, and known procedures and methods can be used.

The raw material dispersion may further contain a dispersion medium other than water. The dispersion medium other than water may be an organic solvent for dispersion or dissolution of each component. In this case, examples of the organic solvent used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol and the like, which are organic solvents that are mixed with water. Further, these organic solvents may be used without being mixed with water to disperse or dissolve each component and then to be mixed with water. These organic solvents can be used alone or in combination of two or more.

Here, the content of water in the total mass of the dispersion medium is preferably 50% by mass or more, preferably 80% by mass or more, from the viewpoint of better coating the raw material particles with the water-soluble metal salt. It is preferably 100% by mass (water only), and more preferably 100% by mass (upper limit 100% by mass).

[Other ingredients]
The raw material dispersion may contain other components as long as the effects of the present invention are not impaired.

[Spray dry method]
The spray-drying method (spray-drying method) is a method for producing a powder by spraying (spraying) a dispersion medium (dispersion liquid) or a solution into a gas atmosphere and drying the dispersion medium or the solvent. According to the spray-drying method, many steps such as concentration, filtration, pulverization, classification, and drying can be performed instantaneously at once, and particle aggregates can be easily obtained. In the present invention, the particle aggregate (a) obtained by the spray-drying method is considered to be an aggregate of particles in which the raw material particles are coated with the water-soluble metal salt which is the raw material of the coating component.

The gas constituting the gas atmosphere for spraying the raw material dispersion is not particularly limited, and examples thereof include an atmospheric atmosphere, an oxygen atmosphere, a nitrogen atmosphere, and an argon atmosphere.

The spray-drying method is performed using a spray dryer. In the spray dryer, the raw material dispersion is ejected from a nozzle and dried by mixing the droplets with the air in a gaseous atmosphere (particularly hot air). As the spray dryer, a commercially available product can be preferably used. The commercially available product is not particularly limited, but for example, product name L-8i manufactured by Ohkawara Kakohiki Co., Ltd. can be used.

The particle size of the coated particles constituting the coated particle powder includes the spray dryer operating conditions such as hot air temperature, atomizer shape, atomizer rotation speed, hot air exhaust volume, and exhaust air temperature, and the viscosity and solid content concentration of the spray dryer supply liquid. It can be controlled by adjusting the stock solution supply speed and the like.

The conditions of the spray-drying method are not particularly limited, and known conditions can be used. Here, the inlet temperature (wind temperature) is not particularly limited, but is preferably 200 ° C. or higher and 250 ° C. or lower. The outlet temperature (exhaust air temperature) is not particularly limited, but is preferably 100 ° C. or higher and 140 ° C. or lower. The atomizer shape is not particularly limited, but is preferably a disc type. The atomizer rotation speed is not particularly limited, but is preferably 18,000 rpm or more and 28,000 rpm or less, for example. Further, the amount of exhaust air, the viscosity of the spray dryer supply liquid, the solid content concentration of the spray dryer supply liquid, and the supply speed of the spray dry and the supply liquid can be appropriately adjusted according to the type of the raw material dispersion and the spray dryer.

Regarding the spray-drying method, description of publicly known documents such as JP-A-2003-11066, JP-A-2017-61737, JP-A-2017-61738, International Publication No. 2015/199244, etc. is appropriately described. You can refer to it.

(Step B)
The method for producing a coated particle powder according to the present invention is a step of heat-treating the particle aggregate (a) obtained in the step (A) at a temperature of 300 ° C. or higher and 750 ° C. or lower to obtain a particle aggregate (b). (B). In this step, by heat-treating the particle aggregate (a), the water-soluble metal salt which is the raw material of the coating component is changed to the coating component, and the particle aggregate (b) containing the raw material particles coated with the coating component. Is considered to be formed. That is, in this step, coated particles are formed.

The heat treatment is not particularly limited, but is preferably performed in a graphite sheath using an inert atmosphere furnace or the like.

The heat treatment temperature is 300 ° C. or higher. If the heat treatment temperature is less than 300 ° C., the water-soluble metal salt that is the raw material of the coating component cannot be sufficiently changed into the coating component, and the function derived from the coating component cannot be sufficiently obtained. From the same viewpoint, the heat treatment temperature is preferably 400 ° C. or higher, more preferably 500 ° C. or higher, and even more preferably 550 ° C. or higher. The heat treatment temperature is 750 ° C. or lower. When the heat treatment temperature is higher than 750 ° C., the reaction of the water-soluble metal salt, which is the raw material of the coating component, proceeds excessively, and the product causes the aggregation of adjacent coated particles to proceed, resulting in a strong aggregate (particle aggregate). ) Is formed. Even if the particle aggregate is later pulverized, the produced powder does not have high dispersibility when dispersed in a medium. From the same viewpoint, it is preferably 700 ° C. or lower, more preferably 650 ° C. or lower, and even more preferably 600 ° C. or lower.

The heat treatment time is not particularly limited, but is preferably 30 minutes or more. Within this range, the coating component can be more sufficiently generated from the water-soluble metal salt which is the coating component, and the function derived from the coating component is improved. From the same viewpoint, the heat treatment time is more preferably 1 hour or more, further preferably 3 hours or more, and particularly preferably 4 hours or more. The heat treatment time is not particularly limited, but is preferably 60 hours or less. Within this range, productivity is further improved. From the same viewpoint, the heat treatment time is more preferably 36 hours or less, further preferably 12 hours or less, and particularly preferably 9 hours or less.

The heat treatment atmosphere is not particularly limited, and examples thereof include an atmospheric atmosphere, an oxygen atmosphere, a nitrogen atmosphere, and an argon atmosphere. Among these, a nitrogen atmosphere and an argon atmosphere are preferable, and an argon atmosphere is more preferable, from the viewpoint of suppressing oxidation of the raw material particles during firing and maintaining the characteristics derived from the raw material particles at a higher level. ..

(Process C)
The method for producing coated particle powder according to the present invention includes a step (C) of obtaining coated particles (c) by crushing the heat-treated particle aggregate (b) obtained in the step (B). .. In this step, the particle aggregate (b) is crushed into individual particles constituting the coated particle powder.

It should be noted that the conventional particle aggregate formed without the above-mentioned steps (A) and (B) is difficult to be uniformly crushed even after being pulverized by this step, and the conventional particle aggregate Even if the coated particle powder produced from the body is dispersed in a medium, it is difficult to obtain a dispersion having high dispersibility.

The crushing method is not particularly limited, and examples thereof include a method using a ball mill, a roller mill, a jet mill, a hammer mill, a pin mill, an attritor, and the like. Among these, from the viewpoint of the uniformity of the coated particle powder after crushing and the improvement of the dispersibility when the coated particle powder is dispersed in the medium, it is preferable to use a ball mill. The ball mill is not particularly limited, and examples thereof include a pot mill rotary table ANZ-10D manufactured by Tech Jam Co., Ltd.

The ball used in the ball mill is not particularly limited, and examples thereof include alumina balls. The diameter of the ball is not particularly limited, but is preferably 0.2 mm or more and 20 mm or less, preferably 0.5 mm or more and 10 mm or less, and further preferably 1 mm or more and 5 mm or less.

The pulverization is not particularly limited, but is preferably performed in the state of a dispersion containing the particle aggregate (b). The concentration of the dispersion is not particularly limited, but the content of the fine particle aggregate (b) is preferably 1% by mass or more and 60% by mass or less with respect to the total mass of the dispersion, and is 5% by mass. It is more preferably 50% by mass or less, and further preferably 10% by mass or more and 40% by mass or less.

The pulverization conditions are not particularly limited, but it is preferably performed at room temperature. The rotation speed at the time of crushing is preferably 30 rpm or more and 300 rpm or less, more preferably 50 rpm or more and 250 rpm or less, and further preferably 100 rpm or more and 200 rpm or less. The crushing time is not particularly limited, but is preferably 1 hour or more and 500 hours or less, more preferably 5 hours or more and 250 hours or less, further preferably 10 hours or more and 150 hours or less, and 20 hours. It is particularly preferable that the time is 100 hours or less.

(Other processes)
The method for producing a coated particle powder according to one embodiment of the present invention may further include steps other than steps (A) to (C). As the other steps, a known step applied in the field of producing coated particles can be selected without particular limitation, and examples thereof include a filtration step and a classification step.

(Coated particle powder)
[Structure of coated particles]
The coated particle powder is produced by the production method according to the present invention. As used herein, the coated particles refer to particles in which at least a part of the raw material particles is coated with a coating layer containing a coating component.

In addition, in this specification, a coated particle powder which is a product represents a plurality of coated particles, or a composition containing them. In the present specification, the term "powder" is used for convenience, but the term does not mean only a powdery (dry) substance, but exists in a dispersed state in a dispersion medium and is dispersed. It also represents a substance that can be obtained as a powder when the medium is volatilized.

That is, in the production method according to the present invention, the coated particle powder as a product may contain components other than the coated particles. However, it is particularly preferable that the components other than the coated particles that can be contained in the coated particle powder are unavoidable impurities in the coating treatment. In the present specification, the unavoidable impurities in the coating treatment are, for example, coatings of raw materials, raw materials of unreacted coating components, by-products, reagents used for reactions that can be added as needed, impurities derived from the raw materials, and the like. Represents a component that may be contained in relation to the formation of particles. The unavoidable impurities in the coating treatment do not include components that can be arbitrarily added for the purpose of functional expression during and after the production.

The ratio of the coated particles in the coated particle powder is most preferably 100% by mass with respect to the total mass of the coated particle powder. However, in consideration of production efficiency and the like, it is preferable that the coated particles are the main component in the coated particle powder, and the ratio of the coated particles in the coated particle powder is more preferably 80% by mass or more, 90. %% by mass or more is further preferable, 99% by mass or more is further preferable, and 99.9% by mass or more is particularly preferable (upper limit 100% by mass).

The coated particle powder quantitatively accurately determines the content of the coated particles in the coated particle powder from a technical and economic point of view, depending on the types of components other than the coated particles contained therein. It can be difficult to analyze or remove other components. In particular, if other components are unavoidable impurities, the situation of such features on the analysis is similar, the content, the difficulty of removing the quantitatively accurate analysis or other components, the high Tend to be. However, even in this case, if it is confirmed by the analysis method described later that the coated particle powder contains the coated particles, the coated particle powder has good dispersibility in the dispersion medium and has good dispersibility in the dispersion medium. , Will have the desired properties derived from the properties of the raw material particles and the coated particles.

The coated particle powder according to one embodiment of the present invention maintains its form as coated particles even when washed with a solvent (preferably water) or dispersed in a dispersion medium (preferably water). It is preferable to be able to do it.

The fact that the produced particles have a coating layer means that the measurement magnification is 20000 times, the acceleration voltage is 10 keV, and the measurement depth is 2 to 3 nm, using the product name PHI 710 manufactured by ULVAC, which is a scanning Auger Microscope (SAM). , SEM observation, and elements contained only in the raw material particles (for example, silicon element (Si element) when the raw material particles are SiC particles) and elements contained only in the coating component contained in the coating layer (that is, coating). It is an element derived only from the raw material of the component, and can be confirmed, for example, by performing element mapping by Auger electron spectroscopy for the aluminum element (Al element) when the coating component is aluminum lactate.

Here, the position of the particles observed in the SEM image, the position of the Auger electron image of the element contained only in the raw material particles, and the position of the Auger electron image contained only in the coating layer (that is, derived only from the raw material of the coating component). When it is confirmed that the position of the Auger electron image of the element clearly corresponds to the position of the Auger electron image, it can be determined that the raw material particles are covered with the coating component.

The details of the measurement method will be described in Examples.

[Composition of coated particles]
In the coated particle powder, the content of the metal element derived from the water-soluble metal salt in the coated particle powder is not particularly limited, but is preferably 0.1% by mass or more. When the content of the metal element derived from the water-soluble metal salt in the coated particle powder is in this range, the coating by the coating layer containing the coating component of the raw material particles becomes more sufficient and can be imparted from the coating layer. The function can be further improved. From the same viewpoint, the content of the metal element derived from the water-soluble metal salt in the coated particle powder is more preferably 0.5% by mass or more, further preferably 1% by mass or more, 3 It is particularly preferable that it is by mass or more. The content of the metal element derived from the water-soluble metal salt in the coated particle powder is not particularly limited, but is preferably 40% by mass or less. If the content of the metal element derived from the water-soluble metal salt in the coated particle powder is within this range, the effect obtained by the coating will be constant once the coating has progressed to some extent, and thus the economic efficiency and production efficiency will be improved. Because it does. From the same viewpoint, the content of the metal element derived from the water-soluble metal salt in the coated particle powder is more preferably 30% by mass or less, further preferably 20% by mass or less, and 10% by mass. The following is particularly preferable. The content of the metal element derived from the water-soluble metal salt in the coated particle powder can be measured by the XRF method using a fluorescent X-ray analyzer. The details of the measurement method will be described in Examples.

The coated particle powder has iron element (Fe element) and nickel element from the viewpoint of more efficient sintering when the function that can be imparted from the coating layer is the function as a sintering aid. The smaller the content of (Ni element), the more preferable. Specifically, the contents of Fe element and Ni element in the coated particle powder are preferably 1% by mass or less, more preferably 0.1% by mass or less (lower limit 0% by mass). ). The contents of Fe element and Ni element in the coated particle powder can be measured by the XRF method using a fluorescent X-ray analyzer. The details of the measurement method will be described in Examples.

The coated particle powder preferably contains a carbon element (C element) from the viewpoint of dispersibility. When the coated particle powder contains element C, the content of element C in the coated particle powder is not particularly limited, but is preferably 10% by mass or more with respect to the total mass of the coated particle powder. It is more preferably 15% by mass or more, and further preferably 20% by mass or more. The content of element C in the coated particle powder is not particularly limited, but is preferably 70% by mass or less, more preferably 60% by mass or less, based on the total mass of the coated particle powder. It is more preferably 50% by mass or less, further preferably 40% by mass or less, and particularly preferably 30% by mass or less. The presence / absence and content of element C in the coated particle powder can be measured by an infrared absorption method using the product name CS-400 manufactured by LECO. The details of the measurement method will be described in Examples.

The coated particle powder preferably contains an element derived from raw material particles and a metal element derived from a water-soluble metal salt, and more preferably contains an Si element, an Al element, an oxygen element (O element) and a C element. The presence of Si element and Al element in the coated particle powder is measured by the above Auger spectroscopy or XRF, and the presence of O element and C element in the coated particle powder is measured by the above infrared absorption method, respectively. can do. The details of these measurement methods will be described in Examples.

[Average secondary particle size]
The average secondary particle size of the coated particle powder is preferably 2 μm (2000 nm) or less. When the average secondary particle size of the coated particle powder is in this range, a dispersion having higher dispersibility can be obtained when the coated particle powder is dispersed in a medium. From the same viewpoint, the average secondary particle size of the coated particle powder is more preferably 1.5 μm (1500 nm) or less, further preferably less than 1.5 μm (1500 nm), and 1.0 μm (1000 nm). ) Or less, more preferably 500 nm or less. The average secondary particle size of the coated particle powder produced by the production method according to one embodiment of the present invention is not particularly limited, but is preferably 10 nm or more. When the average secondary particle size of the coated particle powder is in this range, the viscosity at the time of slurry does not increase excessively, and the handleability becomes better. From the same viewpoint, the average secondary particle size of the coated particle powder is more preferably 10 nm or more, further preferably 20 nm or more, and particularly preferably 30 nm or more. Here, the values of the average secondary particle diameters of the coated particles and the powder are the scattering type particle diameter distribution manufactured by Horiba Seisakusho Co., Ltd. in the dispersion in which the coated particle powder is dispersed in the dispersion medium so as to have an appropriate concentration for measurement. It can be measured by the measuring device LA-950. The details of the measurement method will be described in Examples.

[Ratio of the average secondary particle size of the coated particle powder to the average secondary particle size of the raw material particles]
The ratio of the average secondary particle size of the coated particle powder to the average secondary particle size of the raw material particles (pre-coated particles) in the coated particle powder (hereinafter, also referred to as the ratio of the average secondary particle size to the raw material particles) is Although not particularly limited, it is preferably 10 or less. Within this range, the coated particle powder is produced while maintaining a high degree of dispersibility of the raw material particles or having a dispersibility higher than that of the raw material particles. As a result, a dispersion having higher dispersibility can be obtained when the coated particle powder is dispersed in the medium. From the same viewpoint, the ratio of the average secondary particle size to the raw material particles is more preferably 5 or less, further preferably 3 or less, further preferably 2 or less, and 1.5 or less. It is particularly preferable to have. The ratio of the average secondary particle diameter to the raw material particles in the coated particle powder is not particularly limited, but is preferably 0.1 or more. Within this range, the coverage of the coated particles can be further improved. From the same viewpoint, the ratio of the average secondary particle size to the raw material particles is more preferably 0.5 or more, further preferably 0.7 or more, and even more preferably 0.8 or more. , 0.9 or more is particularly preferable.

Here, the average secondary particle size of the coated particle powder and the average secondary particle size of the raw material particles can be obtained by the above-mentioned methods, respectively.

[Ratio of average secondary particle size of coated particle powder to average primary particle size of raw material particles]
In the coated particle powder, the ratio of the average secondary particle size of the coated particle powder to the average primary particle size of the raw material particles (pre-coated particles) (hereinafter, the ratio of the average secondary particle size to the average primary particle size of the raw material particles). (Also referred to as) is not particularly limited, but is preferably 50 or less. Within this range, a dispersion having higher dispersibility can be obtained when the coated particle powder is dispersed in the medium. From the same viewpoint, the ratio of the average secondary particle size to the average primary particle size of the raw material particles is more preferably 20 or less, further preferably 10 or less, and particularly preferably 8 or less. Further, since the coated particles are considered to be formed after the raw material particles are coated with a water-soluble metal salt, the ratio of the average secondary particle size to the average primary particle size of the raw material particles in the coated particle powder. Is usually more than 1, and is preferably 3 or more, and more preferably 5 or more, from the viewpoint of production efficiency in consideration of the agglomeration of raw material particles.

Here, the average secondary particle size of the coated particle powder and the average primary particle size of the raw material particles can be obtained by the above-mentioned methods, respectively.

<Manufacturing method of dispersion>
Another embodiment of the present invention is a dispersion comprising a step (D) of producing a coated particle powder by the production method according to the first embodiment of the present invention and then mixing the coated particle powder with a dispersion medium. Regarding the manufacturing method of. The dispersion containing the coated particle powder and the dispersion medium produced by the production method has high dispersibility.

The dispersion produced by the production method according to one embodiment of the present invention is not particularly limited, but has high dispersibility, and thus has a raw material for forming a molded product having high uniformity and high polishing properties. It can be preferably used as a polishing composition.

(Step D)
The method for mixing the coated particle powder and the dispersion medium is not particularly limited, and a known method can be used.

[Dispersion medium]
The dispersion produced by the production method according to one embodiment of the present invention contains a dispersion medium. The dispersion medium has a function of dispersing or dissolving each component. The dispersion medium preferably contains water, and more preferably water alone. Further, the dispersion medium may be an organic solvent for dispersion or dissolution of each component. In this case, examples of the organic solvent used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol and the like, which are organic solvents that are mixed with water. The dispersion medium may be a mixed solvent of water and an organic solvent. Alternatively, an organic solvent may be used without mixing with water to disperse or dissolve each component and then mix with water. These organic solvents can be used alone or in combination of two or more.

The water is preferably water containing as little impurities as possible. For example, water having a total content of transition metal ions of 100 ppb or less is preferable. Here, the purity of water can be increased by, for example, operations such as removal of impurity ions using an ion exchange resin, removal of foreign substances by a filter, distillation and the like. Specifically, as the water, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water and the like are preferably used.

[Other ingredients]
The dispersion produced by the production method according to one embodiment of the present invention may contain other components as long as the effects of the present invention are not impaired.

When the other component is another particle, the other particle is not particularly limited, and a known particle can be used. Among these, alumina, copper oxide, iron oxide, from the viewpoint that aggregation is unlikely to occur and good dispersibility is maintained when used in combination with the powder produced by the production method according to one embodiment of the present invention. Preferred examples include nickel oxide, tin oxide, cadmium oxide, zinc oxide, zirconium oxide, and zirconium oxide.

(Other processes)
The method for producing a dispersion according to one embodiment of the present invention may further include steps other than steps (A) to (D).

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "part" mean "% by mass" and "part by mass", respectively.

<Powder production>
(Manufacturing of powder 1)
To 2.64 parts by mass of water, aluminum lactate are water soluble metal salt (molecular _{formula: Al (C 3 H 5 O} 3) 3) was added 0.2 part by weight, were mixed with stirring, the starting material particles Add 1.88 parts by mass of SiC particles 1 (GC # 40,000, manufactured by Fujimi Incorporated Co., Ltd., powder) and mix for 30 minutes with a high-speed disperser Homo Disper 2.5 type manufactured by Primix. Obtained a raw material dispersion.

Next, the obtained raw material dispersion was spray-dried under the conditions of a disk rotation speed of 23000 rpm, an inlet temperature of 230 ° C., and an outlet temperature of 130 ° C. under the conditions of spray dryer Co., Ltd., Ohkawara Kakohki Co., Ltd. A particle aggregate (a), which is an object, was obtained.

Then, the obtained particle aggregate (a) was heated at 600 ° C. for 6 hours under an argon atmosphere to obtain a particle aggregate (b).

Then, 55 g of the obtained particle aggregate (b) was placed in a polyethylene container having a capacity of 500 ml, 3 mm alumina balls were added until the volume became 250 ml, 100 ml of water was added, and then a ball mill (a product manufactured by Tech Jam Co., Ltd.) was added. Powder 1 was prepared by pulverizing with a pot mill turntable ANZ-10D) at a rotation speed of 200 rpm for 48 hours.

(Manufacturing of powder 2)
In the production of the powder 1, the powder 2 was prepared in the same manner except that the particle aggregate (b) was heated at 500 ° C. in an atmospheric atmosphere.

(Manufacturing of powder 3)
SiC grains child 1 which is a raw material particles (GC # 40,000, Ltd. Fujimi Incorporated Ltd., powder) was prepared 20 wt% aqueous dispersion of. Then sodium aluminate was added 50 parts by weight with respect to Si C particle child 1 100 parts by mass as a raw material particles, by dissolving it with stirring, to obtain a raw material dispersion PH13.1. Subsequently, a 9.9% by mass aqueous nitric acid solution was added to the obtained raw material dispersion to adjust the pH to 11.5, and then the dispersion was held between pH 11.5 and pH 10.6 for 60 minutes, and then 9 A 9.9% by mass aqueous nitric acid solution was further added to obtain a dispersion having a pH of 10. Then, pure water was added so that the concentration (content) of the SiC particles with respect to the dispersion was 10% by mass to prepare a dispersion containing powder. Then, the obtained dispersion was dried at 105 ° C. for 12 hours and then calcined at 1000 ° C. for 4 hours to prepare powder 3.

Table 1 below summarizes the raw materials used in the production of each of the above powders.

<Powder analysis>
(Composition analysis)
For each of the above obtained powders, a sample of 0.10 g was measured in a mulite sheath using the product name CS-400 manufactured by LECO, and measurement was carried out. The element content (mass%) was confirmed.

These results are shown in Table 1 below.

Further, the powder 1 obtained above is made into a compact by cold pressing, and fluorescent X-ray (X-ray Fluorescence, XRF) is used using a fluorescent X-ray analyzer LAB CENTER XRF-1700 manufactured by Shimadzu Corporation. ) The presence or absence of Si element, Al element, Ni element and Fe element and the content of Al element, Fe element and Ni element with respect to the total mass of the powder were further confirmed by the analysis method.

(Structural analysis)
For each of the obtained powders, SEM observation was performed using a scanning Auger electron microscope SAM (Manning Auger Spectroscopy) (product name PHI 710 manufactured by ULVAC) at a measurement magnification of 20000 times, an acceleration voltage of 10 keV, and a measurement depth of 2 to 3 nm. At the same time, element mapping was performed for Si element and Al element by Auger electron spectroscopy.

Here, the position of the particles observed in the SEM image, the position of the Auger electron image of the Si element which is an element contained in the raw material particles, and the position of the Auger electron image in the coating component contained in the coating layer (that is, the raw material of the coating component). When it is confirmed that the position of the Auger electron image of the Al element (derived from aluminum lactate) clearly corresponds to the position, it is determined that the SiC particles are covered with a coating component containing Al. When the coating was confirmed, it was determined that the coated particles (c) were formed and the coated particle powder was produced.

These results are shown in Table 1 below.

(Average primary particle size of SiC particles as raw material particles)
The average primary particle diameter (nm) of the SiC particles is based on the average value of the specific surface area (SA) of the SiC particles calculated from the values measured 3 to 5 times continuously by the BET method for the SiC particles of about 0.2 g. , The value of the true density of the SiC particles was used, and the calculation was made assuming that the shape of the SiC particles is a true sphere.

[True Density]
The true density (g / cm ³ ) was measured as follows. First, SiC particles were placed in a 30 g beaker, and then 70 g of pure water was placed and stirred. Next, the SiC particle aqueous dispersion is placed in a crucible so that the solid content (powder) is about 15 g, and the water is evaporated at about 200 ° C. using a commercially available hot plate. Furthermore, in order to remove the water remaining in the voids of the SiC particles, heat treatment is performed at 300 ° C. for 1 hour in an electric furnace (manufactured by Advantech Co., Ltd., firing furnace), and the treated dried SiC particles are crushed in a mortar. .. Next, 10 g of the dried SiC particles prepared above was placed in a 100 ml specific gravity bottle (Wa (g)) whose weight was measured in advance with a precision balance (GH-202, manufactured by A & D Co., Ltd.) and weighed. After measuring (Wb (g)), 20 ml of ethanol was added, and the mixture was degassed in a reduced pressure desiccator for 30 minutes. Then, the inside of the specific density bottle is filled with ethanol, plugged, and the weight is measured (Wc (g)). After the weight of the SiC particles has been measured, the contents of the specific gravity bottle are discarded, and after washing, the bottle is filled with ethanol and the weight is measured (Wd (g)). From these weights and the temperature of ethanol (t (° C.)) at the time of measurement, the true density is calculated by the following formula 1 and the following formula 2.

In the above formula 2, Sg represents the true density (g / cm ³ ) of the SiC particles;
Wa represents the weight (g) of the specific gravity bottle;
Wb represents the total weight (g) of the sample (dried SiC particles) and the specific gravity bottle;
Wc represents the total weight (g) of the sample (dried SiC particles), ethanol and specific gravity bottle;
Wd represents the total weight (g) of ethanol and specific density bottles;
Ld represents the specific gravity (g / cm ³ ) of ethanol obtained by the above formula 1.

[BET specific surface area]
The BET specific surface area (m ² / g) was measured as follows. First, the SiC particles were crushed in a dairy pot, and about 0.2 g of the SiC particles were placed in a cell (Wa'(g)) whose weight was measured in advance and the weight was measured (Wb'(g)), and then 5 minutes or more. The temperature was kept at 180 ° C. in the heating part of a specific surface area meter (manufactured by Shimadzu Corporation, flowersorb II 2300). After that, it was attached to the measuring unit and the adsorption area (A [m ² ]) at the time of degassing was measured. Using the A value, the specific surface area SA [m ² / g] was determined by the following formula 3.

In the above formula 3, SA represents the BET specific surface area (m ² / g) of the SiC particles;
A represents the adsorption area (m ^{2) at the time of degassing;}
Wa'represents the weight (g) of the cell;
Wb'represents the total weight (g) of the sample (dried SiC particles) and the cell.

Table 1 shows the average primary particle size of the SiC particles, which are the raw material particles.

(Average secondary particle size, particle size distribution)
The average secondary particle size and particle size distribution of each SiC particle as a raw material particle and the particles constituting each of the obtained powders were measured by a scattering type particle size distribution measuring device LA-950 manufactured by Horiba Seisakusho Co., Ltd.

Here, for each SiC particle, the SiC particle was measured using a 10% by mass aqueous dispersion. Further, for each powder, the dispersion containing the powder was diluted with pure water until the appropriate concentration was displayed by the apparatus, and the measurement was performed.

Table 1 shows the average secondary particle diameters of each SiC particle as a raw material particle and each of the obtained powders.

(Evaluation of dispersibility in the medium)
The ratio of the average secondary particle size of each of the obtained powders to the average secondary particle size of each SiC particle as the raw material particle (the ratio of the average secondary particle size to the raw material particle) is used as a criterion for evaluating the dispersibility. Using. Here, when the ratio of the average secondary particle size to the raw material particles is 10 or less, it is assumed that the dispersibility is practically acceptable.

Further, the ratio of the average secondary particle size of each of the obtained powders to the average primary particle size of each SiC particle as the raw material particles (the ratio of the average secondary particle size to the average primary particle size of the raw material particles) is also dispersed. Confirmed as a criterion for sexual evaluation.

Table 1 shows the calculation results of each SiC particle which is a raw material particle and each of the obtained powders.

Further, FIG. 1 shows a graph showing the particle size distribution of SiC particles 1 as raw material particles, powder 1 according to an example, and powder 3 according to a comparative example. In FIG. 1, the broken line represents the particle size distribution of the SiC particles 1 which are the raw material particles, the solid line represents the particle size distribution of the powder 1, and the one-point broken line represents the particle size distribution of the powder 3.

From the results in Table 1, it was confirmed that the powder 1 and the powder 2 of the examples according to the present invention had extremely good dispersibility in the medium. On the other hand, it was confirmed that the powder 3 of the comparative example, which is outside the scope of the present invention, is significantly inferior in dispersibility.

Here, since the powder 1 of the example had a higher carbon content with respect to the total mass of the powder and was closer to the theoretical value as compared with the powder 2 of the example, the raw material particles were used. It is considered that the coated fine particle powder is obtained by suppressing the oxidation of certain SiC particles and maintaining the characteristics derived from the raw material particles at a higher level.

Further, the powder 1 of the example contains Si element, Al element, and O element, and the content of Al element, the content of Fe element, and the content of Ni element with respect to the total mass of the powder are, respectively. It was confirmed that it was 3.3% by mass, 0% by mass, and 0% by mass.

Further, even when the powder 1 and the powder 2 of the examples according to the present invention are dispersed in water as a dispersion medium and then the water is evaporated to take out the powder, the same result as described above is obtained. was gotten. From this, it was confirmed that the powder 1 and the powder 2 can maintain their morphology as coated particles regardless of whether they are in a dry state or in a state of being dispersed in a medium.

Then, when a dispersion containing these powders, other particles having an isoelectric point of 5 or more, and a dispersion medium is produced using the powders 1 and 2 of the examples, the produced dispersion is produced. Very good dispersibility and high uniformity can be achieved.

Claims (5)

A step (A) of spray-drying a raw material dispersion containing SiC particles , aluminum lactate, and water to obtain a particle aggregate (a).
The step (B) of heat-treating the particle aggregate (a) at a temperature of 300 ° C. or higher and 750 ° C. or lower to obtain the particle aggregate (b).
The step (C) of obtaining the coated particles (c) by pulverizing the particle aggregate (b), and
Have a,
The average primary particle size of the SiC particles is 10 nm or more and 3000 nm or less.
The average secondary particle diameter of the SiC particles, Ru der least 10000nm less 10 nm, a manufacturing method of the coated particle powder. The production method according to claim 1, wherein the coated particle powder has an average secondary particle diameter of 2 μm or less. The production method according to claim 1 or 2, wherein the ratio of the average secondary particle size of the coated particle powder to the average secondary particle size of the SiC particles is 10 or less. The production method according to any one of claims 1 to 3, wherein the ratio of the average secondary particle size of the coated particle powder to the average primary particle size of the SiC particles is 50 or less. After producing the coated particle powder by the production method according to any one of claims 1 to 4,
A method for producing a dispersion, which comprises a step (D) of mixing the coated particle powder and a dispersion medium.

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