JP6277387B2 - Method for producing forsterite fine particles - Google Patents

Description

  The present invention relates to a method for producing forsterite fine particles useful for various ceramics, translucent decorative materials, electronic parts and the like.

  A composite insulating material in which insulating ceramics (for example, silica) fine particles are filled in a heat-resistant resin such as an epoxy resin has been put to practical use as an integrated circuit sealing material. However, with the recent increase in integration and capacity of integrated circuits, there is a demand for insulating materials with low dielectric loss, particularly in the high frequency region, in order to reduce signal loss in the integrated circuit.

Magnesium and silicon-containing oxides typified by forsterite (Mg ₂ SiO ₄ ) and enstatite (MgSiO ₃ ) have low dielectric loss in the high frequency region and are known as materials showing high insulation, and are used in the microwave region. It is used as a dielectric ceramic material.

  When using magnesium and a silicon-containing oxide as a translucent composite insulating material, it is necessary to make the particle diameter as small as possible in order to suppress light scattering.

In Patent Document 1, Mg (OH) ₂ powder or MgO powder and SiO ₂ powder having an average primary particle size of 10 μm or less are mixed and pulverized in water, spray-dried by a spray dryer, fired at 1100 ° C., and then further wetted. A method for producing MgO—SiO ₂ oxide powder having an average primary particle size of 0.05 to 0.15 μm by pulverization and spray drying is disclosed. However, in this method, if the wet pulverization after firing is omitted, particles of 1 μm or more are formed. For this reason, wet pulverization is required twice in the manufacturing process, which is a very complicated manufacturing method.

  In Patent Document 2, a mixed liquid obtained by mixing a magnesium nitrate aqueous solution and an ethyl silicate solution so that the magnesium amount and the silicon amount are in a molar ratio of 2: 1 is thermally decomposed at 900 ° C. by a spray pyrolysis method. Discloses a method for producing forsterite powder. However, the average particle diameter of the obtained powder is as large as 0.78 μm, and when used as a filler of a translucent composite insulating material, the translucency cannot be sufficiently increased.

  In Patent Document 3, a solution in which a micro hollow inorganic material or a precursor thereof is dissolved in a liquid medium, or a dispersion liquid dispersed in the liquid medium is made into micro droplets, and the high temperature atmosphere in which the inorganic material is sintered or melted is disclosed. A method for producing a crystalline microhollow body by supplying is disclosed. However, the particle diameter of the forsterite hollow body obtained by this method is as large as 2.4 μm, and when used as a filler of a translucent composite insulating material, the translucency cannot be sufficiently increased.

JP 2003-327470 A JP 2003-2640 A JP-A-7-96165

  The present invention has been made in view of such circumstances, and is useful for various ceramics, translucent decorative materials, electronic parts and the like, and particularly as an insulating material having a low dielectric loss in a high frequency region for electronic parts. It is an object of the present invention to provide a method for producing fine forsterite fine particles having a fine particle diameter that can be used and can improve the translucency of particles.

  As a result of diligent research to solve the above problems, the present inventors have spray-dried a solution containing a water-soluble magnesium salt and colloidal silica, and then baked at a temperature of 800 to 1000 ° C. in the atmosphere. It has been found that forsterite fine particles having a primary particle diameter in the range of 1 to 200 nm by electron microscope observation can be produced without going through a pulverization process.

  That is, the present invention relates to a method for producing forsterite fine particles according to any one of the following first to fourth aspects.

First aspect: A solution containing a water-soluble magnesium salt and colloidal silica in a molar ratio of magnesium atom to silicon atom (Mg / Si) 2 is sprayed and dried in a temperature atmosphere of 50 ° C. or more and less than 300 ° C., and then the atmosphere Forsterite fine particles, characterized in that forsterite fine particles having a primary particle diameter in the range of 1 to 200 nm by electron microscope observation are obtained by firing in a temperature atmosphere of 800 to 1000 ° C.
Second aspect: The method for producing forsterite fine particles according to the first aspect, wherein a primary particle diameter of the colloidal silica observed with an electron microscope is 2 to 100 nm,
Third aspect: The method for producing forsterite fine particles according to the first aspect or the second aspect, wherein the water-soluble magnesium salt is an organic acid salt of magnesium,
Fourth aspect: The organic acid salt of magnesium is at least one selected from the group consisting of magnesium citrate, magnesium glycolate, magnesium malate, magnesium tartrate, magnesium lactate, magnesium malonate, magnesium succinate, and magnesium acetate. A method for producing forsterite fine particles according to a third aspect.

  By the production method of the present invention, it is possible to easily produce forsterite fine particles having a primary particle diameter in the range of 1 to 200 nm by observation with an electron microscope.

  The forsterite fine particles produced according to the present invention can not only increase the translucency of particles when used as a filler of a composite insulating material, but also a high refractive index coating agent, antireflection agent, metal, It can also be used as a microfiller for composite materials such as plastics and ceramics. Further, when used as a dielectric ceramic sintered body used in the microwave region, the sintering temperature can be lowered.

2 is an X-ray diffraction pattern of Example 1 and Comparative Example 1. FIG. 2 is a TEM photograph of Example 1.

  The present invention relates to a method for producing forsterite fine particles. In the present invention, a method for preparing a solution containing a water-soluble magnesium salt and colloidal silica is not particularly limited, and the water-soluble magnesium salt and colloidal silica may be appropriately mixed in water by an arbitrary technique.

  In the solution containing the water-soluble magnesium salt and colloidal silica, the ratio of magnesium atom to silicon atom is 2 in terms of Mg / Si molar ratio.

Moreover, when preparing the solution containing water-soluble magnesium salt and colloidal silica, the water-soluble magnesium salt may use the powder, but it is preferable to use it beforehand as an aqueous solution. The solid content concentration in terms of MgO in the aqueous solution may be arbitrary, but is preferably 1 to 20% by mass. The colloidal silica is preferably used in the form of an aqueous dispersion, and the solid content concentration in terms of SiO ₂ may be arbitrary, but is preferably 1 to 40% by mass.

The solid content concentration of the solution containing the water-soluble magnesium salt and colloidal silica may be arbitrary, but is preferably 1 to 10% by mass, more preferably 2 to 5% by mass in terms of Mg ₂ SiO ₄ .

  The water-soluble magnesium salt used in the present invention is a magnesium salt that dissolves 1% by mass or more in water at 25 ° C., and is an inorganic acid salt of magnesium such as magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium citrate, glycol Examples thereof include organic acid salts of magnesium such as magnesium oxide, magnesium malate, magnesium tartrate, magnesium lactate, magnesium malonate, magnesium succinate, and magnesium acetate.

  In addition, as water-soluble magnesium salts, poorly water-soluble magnesium salts such as magnesium hydroxide and magnesium carbonate are hydrochloric acid, nitric acid, sulfuric acid, citric acid, glycolic acid, malic acid, tartaric acid, lactic acid, malonic acid, succinic acid, acetic acid, etc. Those dissolved in acid can also be used.

  The water-soluble magnesium salt can be used alone or in combination of two or more.

  From the viewpoint of the corrosiveness of the gas generated during drying or firing, it is particularly preferable to use an organic acid salt of magnesium.

  The colloidal silica used in the present invention is not particularly limited. Generally, the primary particle diameter by observation with an electron microscope is 1 to 1000 nm, but the primary particle diameter is preferably 2 to 100 nm. The production method of colloidal silica is not particularly limited, and commercially available colloidal silica produced by a method of growing colloidal particles using water glass as a raw material or a method of growing particles after hydrolyzing silicon alkoxide can be used.

  Colloidal silica is usually commercially available as an aqueous silica sol (for example, Snowtex (registered trademark) OXS, Snowtex O, Snowtex 30). The organic solvent dispersion is commercially available as an organosilica sol. Known dispersion media for organosilica sol include methanol, isopropanol, ethylene glycol, methyl ethyl ketone, methyl isobutyl ketone, and ethyl acetate.

  When the solution containing the obtained water-soluble magnesium salt and colloidal silica in a molar ratio of magnesium atom to silicon atom (Mg / Si) 2 is dried, the water-soluble magnesium salt and colloidal silica are uniformly mixed It is preferable to dry with a spray dryer, drum dryer, vacuum dryer, freeze dryer or the like. In particular, it is preferable to use a spray dryer because it can be dried while maintaining a uniform mixed state in the solution.

  The temperature atmosphere at the time of drying is 50 ° C. or higher and lower than 300 ° C., and is preferably lower than the decomposition temperature of the water-soluble magnesium salt and colloidal silica to be used.

  The dried powder obtained is fired in a temperature range of 800 to 1000 ° C. in the air. The firing time is 0.5 to 50 hours, preferably 1 to 20 hours. When the temperature atmosphere during firing exceeds 1000 ° C., the primary particle diameter of the obtained forsterite fine particles becomes larger than 200 nm, so it is difficult to increase the translucency of the particles when used as a filler of a composite insulating material. This is not preferable. Moreover, when the temperature atmosphere at the time of baking is less than 800 degreeC, since a water-soluble magnesium salt and colloidal silica do not fully react and a forsterite microparticle cannot be obtained, it is unpreferable.

  In the present invention, the primary particle diameter by electron microscope observation refers to the particle diameter of individual fine particles observed using a transmission electron microscope.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.

[Production Example 1] Production of magnesium citrate aqueous solution 253.5 g of citric acid monohydrate (manufactured by Kanto Chemical Co., Ltd., special grade, 99.5% by mass) was dissolved in 2058.8 g of pure water to obtain 10.0 mass. % Aqueous citric acid solution was obtained. While stirring the obtained aqueous citric acid solution, 105.7 g of magnesium hydroxide (manufactured by Kanto Chemical Co., Ltd., first grade, 95.0%) was added, and the mixture was stirred at room temperature for 1 hour. Got. Solid content concentration (MgO conversion) of the obtained magnesium citrate aqueous solution was 2.9 mass%.

[Production Example 2] Production of magnesium glycolate aqueous solution 15.2 g of glycolic acid (98.0% by mass, manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 113.4 g of pure water, and 11.6% by mass of glycolic acid aqueous solution was obtained. Obtained. While stirring the resulting aqueous glycolic acid solution, 5.8 g of magnesium hydroxide (manufactured by Kanto Chemical Co., Ltd., first grade, 95.0% by mass) was added, and the mixture was stirred at room temperature for 1 hour, whereby magnesium glycolate An aqueous solution was obtained. Solid content concentration (MgO conversion) of the obtained magnesium glycolate aqueous solution was 3.0 mass%.

[Example 1]
Colloidal silica (Snowtex (registered trademark) OXS, manufactured by Nissan Chemical Industries, Ltd., silica concentration 10.6% by mass, primary particle diameter 5 nm by electron microscope observation) mixed with 283.4 g of pure water, manufactured 1334.8 g of the magnesium citrate aqueous solution obtained in Example 1 was added, and the mixture was stirred at room temperature for 30 minutes. The obtained mixture had a specific gravity of 1.04, a viscosity of 1.8 mPa · s, and a pH of 5.2. Using a spray dryer (Palvis mini spray GA-22 type, manufactured by Yamato Scientific Co., Ltd.), 2500 g of the obtained mixed solution was used at an inlet temperature of 180 ° C., an atomizing air pressure of 1.35 kgf / cm ² , and an aspirator flow rate of 0. Drying was performed under the condition of a liquid feeding speed of 5 g / min of a mixed solution of ³⁰ m ³ / min. At this time, the outlet temperature was 80 ± 2 ° C., and 99.6 g of white dry powder was obtained. 43.1 g of the obtained dry powder was put in a crucible and fired in the atmosphere at a temperature of 500 ° C. for 2 hours using an electric furnace, and then fired in the atmosphere at a temperature of 800 ° C. for 2 hours to obtain a white powder. 12.4 g was obtained. When the obtained white powder was identified by X-ray diffraction analysis, the produced phase was almost a single phase of forsterite, and the specific surface area by the nitrogen adsorption method was 18.4 m ² / g. The X-ray diffraction chart is shown in FIG. The primary particle size was 30 to 50 nm as observed by a transmission electron microscope. A transmission electron micrograph is shown in FIG.

[Example 2]
Colloidal silica (Snowtex (registered trademark) OXS, manufactured by Nissan Chemical Industries, Ltd., silica concentration 10.6 mass%, primary particle diameter 5 nm by electron microscope observation) mixed with 28.3 g of pure water 337.3 g 134.4 g of the magnesium glycolate aqueous solution obtained in Example 2 was added, and the mixture was stirred at room temperature for 30 minutes. The obtained mixture had a specific gravity of 1.02, a viscosity of 1.8 mPa · s, and a pH of 5.3. Using a spray dryer (Palvis mini spray GA-22 type, manufactured by Yamato Scientific Co., Ltd.), 500 g of the obtained mixed liquid was used at an inlet temperature of 180 ° C., an atomizing air pressure of 1.35 kgf / cm ² , and an aspirator flow rate of 0. Drying was performed under the conditions of ³⁰ m ³ / min and a liquid feed rate of 5 g / min. At this time, the outlet temperature was 80 ± 2 ° C., and 11.1 g of white dry powder was obtained. The obtained dry powder (2.0 g) is put in a crucible and baked in the atmosphere at a temperature of 500 ° C. for 2 hours using an electric furnace, and then baked in the atmosphere at a temperature of 800 ° C. for 2 hours to obtain a white powder. 0.5 g was obtained. When the obtained powder was identified by X-ray diffraction analysis, the produced phase was a substantially single phase of forsterite, and the specific surface area by the nitrogen adsorption method was 18.1 m ² / g. The primary particle size was 30 to 50 nm as observed by a transmission electron microscope.

[Comparative Example 1]
Colloidal silica (Snowtex (registered trademark) OXS, manufactured by Nissan Chemical Industries, Ltd., 10.6% by mass of silica, primary particle diameter 5 nm by electron microscope observation) was mixed with 28.3 g of pure water, and then, production example 133.5 g of the magnesium citrate aqueous solution obtained in 1 was added, and the mixture was stirred at room temperature for 30 minutes. The obtained mixture had a specific gravity of 1.04, a viscosity of 1.8 mPa · s, and a pH of 5.2. 281.4 g of the obtained mixed liquid was transferred to a petri dish and dried for 12 hours at a temperature of 80 ° C. using a warm air dryer, to obtain 22.4 g of white dry powder. By putting 5.0 g of the obtained dry powder in a crucible and firing it in the atmosphere at a temperature of 500 ° C. for 2 hours using an electric furnace, and then firing in the atmosphere at a temperature of 800 ° C. for 2 hours, 0.5 g of white powder was obtained. When the obtained powder was identified by X-ray diffraction analysis, the product phase was a mixed phase of forsterite, magnesium oxide and enstatite. The X-ray diffraction chart is shown in FIG.

[Comparative Example 2]
Colloidal silica (Snowtex (registered trademark) OXS, manufactured by Nissan Chemical Industries, Ltd., silica concentration 10.6% by mass, primary particle diameter 5 nm by electron microscope observation) was mixed with 28.3 g of pure water 247.1 g, 5.8 g of magnesium oxide (manufactured by Kanto Chemical Co., Ltd., first grade, 95.0% by mass) was added and stirred at room temperature for 30 minutes. Magnesium hydroxide has a water solubility at 20 ° C. of 0.001% by mass. The obtained mixture had a specific gravity of 1.04, a viscosity of 1.9 mPa · s, and a pH of 9.5. The obtained mixture was sprayed using a spray dryer (Palvis Mini Spray GA-22, manufactured by Yamato Scientific Co., Ltd.), inlet temperature 180 ° C., atomizing air pressure 1.35 kgf / cm ² , aspirator flow rate 0. Drying was performed under the conditions of 30 m ³ / min and a liquid feed rate of 5 g / min. At this time, the outlet temperature was 80 ± 2 ° C., and 4.8 g of white dry powder was obtained. 1.0 g of the obtained dry powder is put into a crucible and fired in the atmosphere at a temperature of 500 ° C. for 2 hours using an electric furnace, and then in the atmosphere at a temperature of 800 ° C. for 2 hours. 0.7 g was obtained. When the obtained powder was identified by X-ray diffraction analysis, the product phase was a mixed phase of magnesium oxide and amorphous.

<Total light transmittance measurement>
[Test Example 1]
Forsterite fine particle slurry was obtained by accommodating 1 g of forsterite fine particles and 9 g of isopropanol prepared in the same manner as in Example 1 in a glass bottle (capacity 20 mL) and performing ultrasonic treatment for 10 minutes. The obtained forsterite fine particle slurry was coated on a glass plate using a 25 μm applicator and then dried at 100 ° C. for 10 minutes to form a forsterite fine particle coating. When the total light transmittance Tt value of the obtained film was measured with a spectroscopic haze meter (NDH5000, Nippon Denshoku Industries Co., Ltd.), the Tt value was 95%.

[Test Example 2]
A forsterite fine particle slurry was obtained in the same manner as in Test Example 1 except that HFF-SO (specific surface area by nitrogen adsorption method was 8.7 m ² / g) manufactured by Marusu Kayaku Co., Ltd. was used as the forsterite fine particles. The obtained forsterite fine particle slurry was coated on a glass plate using a 25 μm applicator and then dried at 100 ° C. for 10 minutes to form a forsterite fine particle coating. When the total light transmittance Tt value of the obtained coating film was measured with a haze meter (NDH5000, Nippon Denshoku Industries Co., Ltd.), the Tt value was 86%.

Claims (4)

  A solution containing a water-soluble magnesium salt and colloidal silica in a molar ratio of magnesium atom to silicon atom (Mg / Si) 2 is sprayed and dried in an atmosphere having a temperature of 50 ° C. or higher and less than 300 ° C. A method for producing forsterite fine particles characterized by obtaining forsterite fine particles having a primary particle diameter in the range of 1 to 200 nm by electron microscope observation by firing in a temperature atmosphere of 1000 ° C.   The method for producing forsterite fine particles according to claim 1, wherein the colloidal silica has a primary particle diameter of 2 to 100 nm as observed by an electron microscope.   The method for producing forsterite fine particles according to claim 1, wherein the water-soluble magnesium salt is an organic acid salt of magnesium. The organic acid salt of magnesium is at least one selected from the group consisting of magnesium citrate, magnesium glycolate, magnesium malate, magnesium tartrate, magnesium lactate, magnesium malonate, magnesium succinate, and magnesium acetate. The method for producing forsterite fine particles according to 1.