Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F5/00—Compounds of magnesium
  • C01F5/02—Magnesia
  • C01F5/06—Magnesia by thermal decomposition of magnesium compounds
  • C01F5/08—Magnesia by thermal decomposition of magnesium compounds by calcining magnesium hydroxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G49/00—Compounds of iron
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/16—Solid spheres
  • C08K7/18—Solid spheres inorganic
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds

Definitions

• the present invention relates to spherical magnesium oxide and a method for producing the same, as well as a thermally conductive filler containing the spherical magnesium oxide and a resin composition containing the same.
• Silica, alumina, etc. have traditionally been used as thermally conductive fillers, but silica has low thermal conductivity and is insufficient at dissipating heat to cope with the increase in heat generated by recent trends such as high integration, high power consumption, and high speed, which can cause problems with the stable operation of semiconductors.
• alumina has a higher thermal conductivity than silica, and improves heat dissipation compared to silica, but alumina's high hardness causes severe wear on kneading machines, molding machines, molds, etc., which is a problem.
• magnesium oxide which has a thermal conductivity one order of magnitude higher than silica and about twice that of alumina, and is also less hard than alumina, and can suppress wear on each manufacturing equipment, is being considered as a thermally conductive filler.
• Patent Document 1 proposes magnesium oxide in which a boron compound or the like is added to control the aggregation state and particle size distribution.
• Patent Document 2 proposes spherical magnesium oxide with a smooth and dense surface, which is obtained by adding a lithium compound.
• Patent Document 3 proposes spherical magnesium oxide with excellent moisture resistance and filling properties, which is obtained by adjusting the boron and iron content within a certain range.
• the objective of the present invention is to provide spherical magnesium oxide that has high sphericity, excellent filling ability into resin, and small increase in viscosity when kneaded into resin, and a method for producing the same.
• the gist of the present invention is as follows.
• D 50 volume-based cumulative 50% particle size
• the spherical magnesium oxide of [1] having a cumulative 50% particle diameter (D 50 ) of more than 25 ⁇ m and not more than 150 ⁇ m.
• a method for producing spherical magnesium oxide comprising the steps of: 1) reacting an aqueous magnesium chloride solution with an aqueous alkali solution to prepare a magnesium hydroxide slurry; 2) drying and calcining the magnesium hydroxide slurry to prepare magnesium oxide; 3) dispersing the magnesium oxide in a solvent to prepare a dispersion, followed by wet-grinding; 4) spray-drying the magnesium oxide dispersion after wet-grinding; and 5) calcining the spherical magnesium oxide granulated by spray-drying, wherein in at least one of steps 1) to 5), the titanium and/or iron content is adjusted so that the spherical magnesium oxide after calcination has a titanium content of 0.05 to 2.0% and an iron content of 100 to 1,500 ppm.
• the present invention provides spherical magnesium oxide with high sphericity, excellent fillability into resin, and small increase in viscosity when filled into resin, as well as a method for producing the same.
• the spherical magnesium oxide of the present invention contains 0.05 to 2.0% titanium and 100 to 1,500 ppm iron, has a volume-based cumulative 50% particle size (D 50 ) in the range of 3 to 200 ⁇ m as measured by laser diffraction scattering particle size distribution measurement, and has a sphericity of 1.00 to 1.20 as read from a SEM photograph.
• D 50 volume-based cumulative 50% particle size
• % means % by mass
• ppm means ppm by mass, unless otherwise specified.
• the spherical magnesium oxide of the present invention is intended to be magnesium oxide powder.
• the spherical magnesium oxide obtained in the present invention has a volume-based cumulative 50% particle size ( D50 ) measured by laser diffraction/scattering particle size distribution measurement of 3 to 200 ⁇ m, preferably 15 to 180 ⁇ m, and more preferably more than 25 ⁇ m and not more than 150 ⁇ m, which is a relatively large particle size range capable of improving heat dissipation performance, and also has high sphericity and excellent filling ability.
• D50 volume-based cumulative 50% particle size measured by laser diffraction/scattering particle size distribution measurement of 3 to 200 ⁇ m, preferably 15 to 180 ⁇ m, and more preferably more than 25 ⁇ m and not more than 150 ⁇ m, which is a relatively large particle size range capable of improving heat dissipation performance, and also has high sphericity and excellent filling ability.
• sphericity refers to the sphericity that can be read from a scanning electron microscope (SEM) photograph, and should be 1.00 to 1.20, preferably 1.00 to 1.15, and more preferably 1.00 to 1.10. Such sphericity provides excellent filling properties into resin.
• SEM scanning electron microscope
• the lengths of the major and minor axes passing through the center of the particles are measured for 100 particles in an electron microscope photograph taken using an SEM, the ratio of the major axis to the minor axis is calculated, and the average value is taken as the sphericity.
• the titanium content is 0.05 to 2.0%, preferably 0.08 to 1.5%, and more preferably 0.1 to 1.0%.
• the iron content is 100 to 1,500 ppm, preferably 150 to 1,300 ppm, and more preferably 200 to 1,000 ppm.
• the method for producing spherical magnesium oxide of the present invention is not particularly limited, but can be produced, for example, by the following production method: 1) a step of reacting an aqueous magnesium chloride solution with an aqueous alkali solution to prepare magnesium hydroxide slurry, 2) a step of drying and firing the magnesium hydroxide slurry to prepare magnesium oxide, 3) a step of dispersing the magnesium oxide in a solvent to prepare a dispersion liquid, which is then wet-pulverized, 4) a step of spray-drying the magnesium oxide dispersion liquid after wet-pulverization, and 5) a step of firing the spherical magnesium oxide granulated by spray drying, and in at least one or more of the steps 1) to 5), the titanium and/or iron content is adjusted so that the titanium content in the spherical magnesium oxide after firing is 0.05 to 2.0% and the iron content is 100 to 1,500 ppm.
• the above-mentioned production method can be carried out as follows. 1) A magnesium chloride aqueous solution is reacted with an alkaline aqueous solution to obtain a magnesium hydroxide slurry, and then 2) The slurry is filtered, washed with water, dried, and then calcined to obtain magnesium oxide. 3) The magnesium oxide is dispersed in a solvent, preferably an organic solvent, to obtain a dispersion liquid, which is then wet-pulverized. 4) Spray drying is carried out; 5) The obtained spherical magnesium oxide is fired to obtain the desired spherical magnesium oxide.
• a titanium source and/or an iron source are mixed and/or added before the final firing so that the titanium content of the spherical magnesium oxide after the final firing is 0.05 to 2.0% and the iron content is 100 to 1,500 ppm.
• the titanium content and/or the iron source are adjusted by, for example, a) adding a boron source and/or an iron source to an aqueous magnesium chloride solution and/or an alkaline aqueous solution, b) adding a titanium source and/or an iron source to the generated magnesium hydroxide slurry, c) mixing a titanium source and/or an iron source with magnesium oxide obtained by firing magnesium hydroxide, d) adding a titanium source and/or an iron source during wet grinding of magnesium oxide, e) mixing a titanium source and/or an iron source with spherical magnesium oxide granulated by spray drying, or the like, to adjust the titanium content and iron content in the spherical magnesium oxide finally obtained.
• the titanium content and the iron content may be adjusted
• the titanium source is not particularly limited as long as it is a compound containing titanium, but examples include titanium oxide (anatase type, rutile type), titanium chloride, titanium hydroxide, titanium bromide, titanium fluoride, magnesium titanate, etc.
• the iron source is not particularly limited as long as it is a compound containing iron, but examples include iron oxide (II), iron oxide (III), iron tetroxide, iron hydroxide, iron chloride, iron nitride, iron bromide, and iron fluoride.
• the titanium source is adjusted so that the titanium content of the spherical magnesium oxide after final firing is 0.05-2.0%. If the titanium content is less than 0.05%, the effect of reducing viscosity is not sufficient. Furthermore, if the titanium content exceeds 2.0%, excessive particle growth and adhesion between particles are likely to occur, making it impossible to obtain spherical magnesium oxide with high sphericity. Then, the iron source is adjusted so that the iron content of the spherical magnesium oxide after final firing is 100-1,500 ppm. In addition to the above titanium content, if the iron content is in the range of 100-1,500 ppm, spherical magnesium oxide with high sphericity tends to be obtained.
• the magnesium chloride aqueous solution can be selected from, for example, magnesium chloride hexahydrate, magnesium chloride dihydrate, anhydrous magnesium chloride, bittern, seawater, and combinations thereof.
• the alkaline aqueous solution can be selected from, for example, an aqueous sodium hydroxide solution, an aqueous calcium hydroxide solution, ammonia water, and combinations thereof.
• the magnesium hydroxide slurry obtained by reacting an aqueous magnesium chloride solution with an aqueous alkali solution is filtered, washed with water, dried, and then calcined to form magnesium oxide, for example, by a method common in the technical field.
• the obtained magnesium oxide is then dispersed in a solvent to form a dispersion (for example, a slurry), which is wet-pulverized and spray-dried to form granules.
• the solvent used here is not particularly limited, but any known solvent can be used, such as water-based systems, water-organic solvent mixtures, alcohols such as methanol and ethanol, ketones such as acetone, esters such as ethyl acetate, ethers such as diethyl ether, and aromatic compound solvents such as tetrahydrofuran and toluene.
• the method of spray drying is not particularly limited, but it is preferable to use a spray drying method in which a magnesium oxide dispersion (e.g., a slurry) after wet grinding is sprayed from a rotating disk or nozzle to obtain magnesium oxide particles.
• a magnesium oxide dispersion e.g., a slurry
• the operating conditions are appropriately adjusted according to the slurry viscosity, the particle size of the powder in the slurry, the target particle size, and the like.
• a dispersant may be appropriately added to the slurry.
• the operating conditions are not particularly limited, but in the case of the spray drying method, for example, a slurry with a viscosity adjusted to 10 to 3000 cps is sprayed from a rotating disk or nozzle into an air flow at 80°C to 250°C by appropriately adjusting the flow rate, and particles of about 1 to 200 ⁇ m can be produced.
• the spray conditions by appropriately setting the spray conditions, the sphericity of the obtained spherical magnesium oxide can be adjusted.
• the cumulative 50% particle size (D 50 ) of the obtained spherical magnesium oxide can be adjusted.
• the spray drying method is preferred since it can stably obtain particles having a large particle size.
• the conditions for sintering the granulated magnesium oxide are not particularly limited as long as they are within the range in which the magnesium oxide particles are sintered, but a temperature of 1000°C to 1800°C is preferable, 1100°C to 1700°C is more preferable, and 1200°C to 1600°C is particularly preferable.
• the sintering time depends on the sintering temperature, but is preferably 0.5 to 10 hours. If the sintering temperature is less than 1000°C, sufficient sintering will not occur, and if it exceeds 1800°C, the particles will sinter together and form coarse agglomerates, so it is adjusted to the above range.
• the spherical magnesium oxide of the present invention can also be surface-treated using a known method for the purpose of improving moisture resistance.
• a known method for the purpose of improving moisture resistance there are no particular limitations on the surface treatment agent used, but examples that can be used include colloidal silica, silane-based coupling agents, titania sol, titanate-based coupling agents, phosphorus compounds, alumina sol, aluminate-based coupling agents, zirconium-based coupling agents, etc. These may be used alone or in combination of two or more types.
• silane coupling agents examples include vinyltrichlorosilane, vinyltrialkoxysilane, glycidoxypropyltrialkoxysilane, and methacryloxypropylmethyldialkoxysilane.
• Titanate coupling agents include, for example, tetraisopropyl titanate, tetranormalbutyl titanate, tetraoctyl titanate, tetrastearyl titanate, isopropyltriisostearoyl titanate, tetraoctylbis(ditridecylphosphite)titanate, bis(dioctylpyrophosphate)oxyacetate titanate, etc.
• the phosphorus compound is not particularly limited as long as it is a compound that can react with magnesium oxide to form a magnesium phosphate compound, but examples include phosphoric acid, phosphates, and acidic phosphate esters.
• acidic phosphate esters include isopropyl acid phosphate, 2-ethylhexyl acid phosphate, oleyl acid phosphate, methyl acid phosphate, ethyl acid phosphate, propyl acid phosphate, butyl acid phosphate, lauryl acid phosphate, and stearyl acid phosphate.
• aluminate coupling agents include aluminum isopropylate, monosec-butoxyaluminum diisopropylate, aluminum sec-butylate, aluminum ethyl acetoacetate diisopropylate, aluminum tris(ethyl acetoacetate), and aluminum alkyl acetoacetate diisopropylate.
• zirconium-based coupling agents examples include normal propyl zirconate and normal butyl zirconate.
• the spherical magnesium oxide of the present invention has the advantages of high sphericity, excellent filling properties, and small increase in viscosity when filled into resin, and can therefore be suitably blended into resin as a filler, making it useful as a thermally conductive filler.
• the thermally conductive filler of the present invention may contain the spherical magnesium oxide of the present invention alone, or may contain the spherical magnesium oxide of the present invention together with other thermally conductive filler materials.
• the resin composition of the present invention contains the thermally conductive filler of the present invention, and examples of resins that can be used in the present invention include thermosetting resins and thermoplastic resins.
• Thermosetting resins are not particularly limited, but examples include phenolic resins, urea resins, melamine resins, alkyd resins, polyester resins, epoxy resins, diallyl phthalate resins, polyurethane resins, and silicone resins.
• Thermoplastic resins are not particularly limited, but examples include polyamide resins, polyacetal resins, polycarbonate resins, polybutylene terephthalate resins, polyolefin resins, polysulfone resins, polyamideimide resins, polyetherimide resins, polyarylate resins, polyphenylene sulfide resins, polyether ether ketone resins, fluororesins, and liquid crystal polymers.
• the amount of spherical magnesium oxide in the resin composition of the present invention may be appropriately determined depending on the properties required of the resin composition, and is not particularly limited. However, as an example, spherical magnesium oxide may be used in the range of 0.1 to 100 parts by mass per 100 parts by mass of resin.
• the resin composition containing the spherical magnesium oxide of the present invention can be used in various fields depending on the characteristics of the resin. However, since the spherical magnesium oxide of the present invention has excellent thermal conductivity, it can be used particularly preferably in applications where heat dissipation is required. For example, the resin composition of the present invention can be used as a semiconductor encapsulation material with excellent thermal conductivity.
• Measurement and evaluation methods (1) Measurement method of iron content The iron content was measured by ICP emission spectrometry. The measurement sample was added to 12N hydrochloric acid (special grade reagent) and heated to completely dissolve, and the iron content was measured using an ICP measurement device (PS3520 VDD, manufactured by Hitachi High-Tech Science Corporation).
• the titanium content was measured using an X-ray fluorescence analyzer (device name: ZSX Primus4, manufactured by Rigaku Corporation).
• the magnesium oxide to be measured was placed in an aluminum ring ( ⁇ 35 mm), sandwiched between dies, and pelletized using a press (surface pressure 250 MPa) to obtain a measurement sample.
• This sample was measured in SQX analysis (EZ scan) mode (bulb: Rh (4 kW), atmosphere: vacuum, analysis window: Be (30 ⁇ m), measurement diameter: 30 mm ⁇ , measurement range F to U) to determine the titanium content in the magnesium oxide.
• volume-based cumulative 50% particle size ( D50 ) 0.1 ⁇ 10 ⁇ 3 kg of the measurement sample was precisely weighed, dispersed in 40 mL of methanol, and measured using a laser diffraction scattering type particle size distribution measuring device (MT3300, manufactured by Nikkiso Co., Ltd.).
• Viscosity evaluation during resin filling Spherical magnesium oxide to be evaluated and alumina particles were mixed at 50% by volume, and this was added to silicone oil (Shin-Etsu Chemical's "KF96-100cs") so that the total filling rate of the spherical magnesium oxide and alumina particles was 75% by volume. This was mixed for 30 seconds at a rotation speed of 2,200 rpm using a rotation/revolution mixer, and then vacuum degassed to obtain a resin composition.
• the viscosity of the obtained resin composition was measured using a B-type viscometer (TOKIMEC's BL type, measurement conditions: sample temperature 25°C, 6 rpm, rotor No. 4, container dimensions ⁇ 26 mm ⁇ h46 mm, sample amount 20 mL).
• Example 1 Anhydrous magnesium chloride (MgCl 2 ) was dissolved in ion-exchanged water to prepare an aqueous magnesium chloride solution of about 3.5 mol/l.
• the MgCl 2 solution and 25% NaOH solution were each pumped into a reactor with a metering pump so that the reaction rate of MgCl 2 was 90 mol%, and a continuous reaction was carried out to obtain a magnesium hydroxide slurry.
• titanium oxide/anatase type manufactured by Teika Co., Ltd., JA-20
• titanium oxide/anatase type manufactured by Teika Co., Ltd., JA-20
• iron oxide (II) manufactured by Hayashi Pure Chemical Industries Co., Ltd.
• the obtained magnesium hydroxide was fired at 900°C for 1 hour to obtain magnesium oxide.
• the obtained magnesium oxide was dispersed in an organic solvent to obtain a slurry with a magnesium oxide concentration of 65 wt%.
• Example 2 Spherical magnesium oxide was obtained using the same production method as in Example 1, except that titanium oxide was added to the reaction liquid so that the titanium content in the spherical magnesium oxide was 0.39% and iron (II) oxide was added to the reaction liquid so that the iron content was 330 ppm.
• Example 3 Spherical magnesium oxide was obtained using the same production method as in Example 1, except that titanium oxide was added to the reaction liquid so that the titanium content in the spherical magnesium oxide was 0.11% and iron (II) oxide was added to the reaction liquid so that the iron content was 330 ppm.
• Example 4 Spherical magnesium oxide was obtained using the same manufacturing method as in Example 1, except that titanium oxide was added to the reaction solution so that the titanium content in the spherical magnesium oxide was 0.75% and iron (II) oxide was added so that the iron content was 240 ppm, and the firing temperature in the final firing was 1300°C.
• the spherical magnesium oxide of Examples 1 to 4 had high sphericity and the increase in viscosity when filled with resin was kept low.
• the spherical magnesium oxide of Comparative Example 1 had high sphericity, but the increase in viscosity when filled with resin was large, and its performance as a filler was poor.
• the spherical magnesium oxide of the present invention has a small increase in viscosity when filled into resin, has high sphericity, and is excellent in fillability into resin. Therefore, it was found that the spherical magnesium oxide of the present invention is useful as an excellent resin filler.
• the present invention provides spherical magnesium oxide that exhibits a small increase in viscosity when filled into resin, has high sphericity, and is excellent in fillability into resin, as well as a method for producing the same.

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  • 2024-03-28 JP JP2025511107A patent/JPWO2024204485A1/ja active Pending
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