Spherical magnesium oxide and method for producing same, resin filler, and resin composition

Abstract

The purpose of the present invention is to provide: a spherical magnesium oxide having high sphericity and excellent moisture resistance and properties to be filled in a resin; and a method for producing the spherical magnesium oxide.　The present invention is a spherical magnesium oxide having such properties that the total content of an element belonging to any one of Group-3 to Group-4 on the periodic table (excluding an element belonging to any one of Group-2 and Group-18) and yttrium is 500 to 12,000 ppm, the volume-based cumulative 50% particle diameter (D50) is 1 to 200 μm when measured by a laser diffraction scattering particle size distribution measurement, and the sphericity determined from an SEM image is 1.00 to 1.20.

Description

Spherical magnesium oxide, its manufacturing method, resin filler, and resin composition

[0001] The present invention relates to spherical magnesium oxide having high sphericity and excellent moisture resistance, a method for producing the same, a resin filler containing the spherical magnesium oxide, and a resin composition containing the same.

[0002] Magnesium oxide has excellent electrical insulation, thermal conductivity, and heat resistance, and is used in a variety of applications, including as a refractory raw material, heater insulating material, abrasive, rubber vulcanization accelerator, and paint / ink pigment. It is also used as a resin filler to impart properties such as heat resistance to resins. Patent Document 1 describes the use of magnesium oxide to impart gas barrier properties to resin films used in packaging applications such as food. Patent Document 2 describes the use of magnesium oxide as a white pigment added to resins. Patent Document 3 describes the use of magnesium oxide to improve the light resistance of resins. Patent Document 4 describes the use of magnesium oxide to improve the thermal conductivity of epoxy resins. However, when incorporated into resins, magnesium oxide is highly hygroscopic, and hydration with atmospheric moisture can cause problems such as cracks due to volume expansion of the filler. Therefore, there is a need for magnesium oxide with excellent moisture resistance that does not cause these problems even with long-term use. Furthermore, when magnesium oxide is used as a resin filler, high loading capacity into resin compositions is also required to achieve excellent performance.

[0003] When magnesium oxide is used as a resin filler, it needs to have good filling properties and moisture resistance. Patent Document 5 proposes spherical magnesium oxide with a smooth surface and fine grains, which is obtained by adding a lithium compound. Patent Document 6 proposes spherical magnesium oxide with a smooth surface and excellent moisture resistance and filling properties, which is obtained by adjusting the boron and iron contents within a certain range. Patent Document 7 proposes spherical magnesium oxide with excellent moisture resistance and excellent fluidity of a resin composition when filled into a resin, which is obtained by adjusting the boron and lithium contents within a certain range.

[0004] JP 2015-131494 A JP 2015-101614 A JP 2009-227725 A JP 2017-186578 A JP 2016-088838 A JP 2018-131378 A International Publication No. 2020 / 203710

[0005] However, although the spherical magnesium oxide obtained by the above-mentioned method has improved moisture resistance and resin fillability, it is necessary to control the boron content and lithium content. Furthermore, since the magnesium oxide contains a large amount of boron or lithium, its properties (insulating properties, heat resistance, thermal conductivity) are reduced, and these elements are more likely to leach into the resin, adversely affecting the performance of final products such as electronic devices. Furthermore, since the inclusion of lithium in magnesium oxide adversely affects the fluidity of the resin composition when filled into the resin, a low lithium content is desirable. Therefore, an object of the present invention is to provide spherical magnesium oxide that has high sphericity, excellent moisture resistance, and excellent resin fillability even without containing a certain amount of boron or lithium, and a method for producing the same.

[0006] In order to solve the above problems, the inventors conducted extensive research and found that by adjusting the content of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18), spherical magnesium oxide with high sphericity, moisture resistance, and resin fillability can be obtained without containing a certain amount of boron or lithium. Furthermore, they found that adjusting the content of yttrium in addition to elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) is also effective in obtaining spherical magnesium oxide with high sphericity, moisture resistance, and resin fillability.

[0007] That is, the present invention provides a composition containing 500 to 12,000 ppm of elements belonging to the third and fourth periods of the periodic table (excluding elements belonging to the second and eighteenth periods) and yttrium in total, and a volume-based cumulative 50% particle diameter (D ５０) is in the range of 1 to 200 μm, and the sphericity as read from the SEM photograph is 1.00 to 1.20.

[0008] The present invention also provides a powder containing 500 to 12,000 ppm of elements belonging to the third and fourth periods of the periodic table (excluding elements belonging to the second and eighteenth groups), and a particle size distribution measured by a laser diffraction / scattering method, which is a volume-based cumulative 50% particle size (D ５０ ) is in the range of 1 to 200 μm, and the sphericity as read from the SEM photograph is 1.00 to 1.20.

[0009] The present invention also provides a resin filler containing the spherical magnesium oxide.

[0010] The present invention also provides a resin composition containing the resin filler.

[0011] The present invention also provides a method for producing spherical magnesium oxide, comprising: 1) a step of reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then agglomerating the resulting magnesium carbonate to obtain a spherical magnesium carbonate slurry; 2) a step of filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles; and 3) a step of firing the spherical magnesium carbonate particles to obtain spherical magnesium oxide, wherein in at least one of steps 1) to 3), the amounts of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) and yttrium are adjusted so that the total content of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) and yttrium in the fired spherical magnesium oxide is 500 to 12,000 ppm.

[0012] The present invention also provides a method for producing spherical magnesium oxide, comprising: 1) a step of reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then agglomerating the resulting magnesium carbonate to obtain a spherical magnesium carbonate slurry; 2) a step of filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles; and 3) a step of firing the spherical magnesium carbonate particles to obtain spherical magnesium oxide, wherein in at least one of steps 1) to 3), the amount of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) is adjusted so that the total content of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) in the fired spherical magnesium oxide is 500 to 12,000 ppm.

[0013] According to the present invention, it is possible to provide spherical magnesium oxide having high sphericity, excellent moisture resistance and excellent fillability in resin, and a method for producing the same.

[0014] 1 shows an SEM photograph of spherical magnesium oxide of Example 1.

[0015] The spherical magnesium oxide of the present invention has a total content of elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) and yttrium of 500 to 12,000 ppm, and a volume-based cumulative 50% particle diameter (D) measured by laser diffraction / scattering particle size distribution measurement. ５０ ) is in the range of 1 to 200 μm, and the sphericity as read from the SEM photograph is 1.00 to 1.20.

[0016] The spherical magnesium oxide of the present invention has a total content of elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) of 500 to 12,000 ppm, and a volume-based cumulative 50% particle diameter (D ５０ ) is in the range of 1 to 200 μm, and the sphericity as read from an SEM photograph is 1.00 to 1.20. In the specification, ppm means mass ppm unless otherwise specified.

[0017] In the present invention, the total content of elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) and yttrium is controlled to 500 to 12,000 ppm, thereby achieving a volume-based cumulative 50% particle diameter (D ５０ When the particle diameter is in the range of 1 to 200 μm, the spherical magnesium oxide can be obtained with a high sphericity of 1.00 to 1.20 as read from an SEM photograph, and has excellent moisture resistance. The spherical magnesium oxide of the present invention has excellent fillability into resin due to such high sphericity.

[0018] In addition, in the present invention, for example, by controlling the total content of elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) to 500 to 12,000 ppm, it is possible to obtain a particle size distribution of 50% cumulative particle diameter (D) on a volume basis measured by laser diffraction / scattering particle size distribution measurement. ５０ When the particle diameter is in the range of 1 to 200 μm, the spherical magnesium oxide can be obtained with a high sphericity of 1.00 to 1.20 as read from an SEM photograph, and has excellent moisture resistance. The spherical magnesium oxide of the present invention has excellent fillability into resin due to such high sphericity.

[0019] In the present invention, the elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) specifically refer to sodium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, and bromine. For example, at least one element selected from the group consisting of sodium, aluminum, silicon, phosphorus, chlorine, potassium, and titanium is preferred, and at least one element selected from the group consisting of aluminum, silicon, phosphorus, and titanium is more preferred. Furthermore, at least one element selected from the group consisting of aluminum, silicon, and titanium is also preferred. In the present invention, by adjusting the content of elements belonging to Periods 3 and 4 of the periodic table, spherical magnesium oxide having excellent moisture resistance, high sphericity, and a smooth surface can be obtained.

[0020] In the present invention, for example, the total content of elements belonging to Periods 3 and 4 of the periodic table (excluding elements belonging to Groups 2 and 18) is 500 to 12,000 ppm, preferably 500 to 10,000 ppm, and more preferably 500 to 8,000 ppm. If the total content is less than 500 ppm, it is not possible to obtain spherical magnesium oxide that has excellent moisture resistance, high sphericity, and a smooth surface. If the total content is more than 12,000 ppm, excessive particle growth and adhesion between particles are likely to occur, making it impossible to obtain spherical magnesium oxide with high sphericity.

[0021] The spherical magnesium oxide of the present invention is prepared by adjusting the total content of, for example, sodium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, bromine, and yttrium to a predetermined amount (e.g., 500 to 12,000 ppm, preferably 500 to 10,000 ppm, more preferably 500 to 8,000 ppm). This allows for the production of spherical magnesium oxide that has excellent moisture resistance, high sphericity, and a smooth surface. It is also preferable that the total content of aluminum, silicon, phosphorus, manganese, titanium, and yttrium be adjusted to the above-mentioned predetermined amount. Furthermore, for example, the spherical magnesium oxide of the present invention may have the total content of aluminum, silicon, phosphorus, manganese, and titanium adjusted to the above-mentioned predetermined amount, or the total content of aluminum, silicon, and titanium adjusted to the above-mentioned predetermined amount.

[0022] The spherical magnesium oxide of the present invention can contain a predetermined amount (e.g., 500 to 12,000 ppm, preferably 500 to 10,000 ppm, more preferably 500 to 8,000 ppm) of at least one element selected from the group consisting of sodium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, bromine, and yttrium, thereby enabling the production of spherical magnesium oxide that has excellent moisture resistance, high sphericity, and a smooth surface. It is also preferable that the spherical magnesium oxide of the present invention contains the predetermined amount of at least one element selected from the group consisting of aluminum, silicon, phosphorus, manganese, titanium, and yttrium. Furthermore, for example, the spherical magnesium oxide of the present invention may contain the above-mentioned predetermined amount of at least one selected from the group consisting of aluminum, silicon, phosphorus, manganese, and titanium, or may contain the above-mentioned predetermined amount of at least one selected from the group consisting of aluminum, silicon, and titanium.

[0023] In the present invention, spherical magnesium oxide having excellent moisture resistance, high sphericity, and a smooth surface can be obtained even without containing a certain amount of boron, and therefore the boron content can be extremely low. Therefore, in the present invention, the boron content can be, for example, less than 10 ppm, preferably less than 9 ppm, and more preferably less than 8 ppm. By reducing the boron content, it is possible to prevent deterioration of the properties of magnesium oxide. Furthermore, since it is possible to reduce the elution of boron into resins, it is possible to prevent errors in electronic circuits when used in applications such as electronic devices.

[0024] In the present invention, since spherical magnesium oxide having excellent moisture resistance, high sphericity, and a smooth surface can be obtained without containing a certain amount of lithium, the lithium content can be extremely low. Therefore, in the present invention, the lithium content can be, for example, less than 15 ppm, preferably less than 10 ppm, and more preferably less than 5 ppm. By reducing the lithium content, it is possible to prevent a decrease in the insulating properties of magnesium oxide. Furthermore, it is possible to reduce the elution of lithium into the resin, thereby preventing a decrease in the performance of the final product.

[0025] In the present invention, the calcium content is, for example, less than 700 ppm, preferably less than 600 ppm, and more preferably less than 500 ppm. If the calcium content is 700 ppm or more, moisture resistance tends to decrease, and it tends to be difficult to obtain spherical magnesium oxide with high sphericity.

[0026] In the present invention, the cumulative 50% particle diameter (D ５０ ) is in the range of 1 to 200 μm, preferably 5 to 100 μm, and more preferably 10 to 50 μm. Also, for example, 10 to 150 μm is a preferred range.

[0027] In the present invention, the sphericity that can be read from an SEM photograph, which affects the fillability into a resin, is 1.00 to 1.20, preferably 1.00 to 1.15, and more preferably 1.00 to 1.10. In the present invention, the lengths of the major axis and minor axis passing through the center of the particle are measured for 100 particles in an electron micrograph taken using a scanning electron microscope (SEM), the ratio of the major axis to the minor axis is calculated, and the average value is taken as the sphericity.

[0028] In the present invention, the BET specific surface area is, for example, 0.01 to 1.00 m ２ / g, preferably 0.05 to 0.80 m ２ / g, more preferably 0.10 to 0.60 m ２ / g.

[0029] There is no particular limitation on the method for producing the spherical magnesium oxide of the present invention, but it can be produced, for example, as follows.

[0030] 1) reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then agglomerating the resulting magnesium carbonate to obtain a spherical magnesium carbonate slurry, 2) filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles, and 3) firing the spherical magnesium carbonate particles in air to obtain the target spherical magnesium oxide, in which the amounts of elements belonging to periods 3 to 4 of the periodic table (excluding elements belonging to groups 2 and 18) are adjusted by addition, mixing, etc., before the final firing so that the total content of elements belonging to periods 3 to 4 of the periodic table (excluding elements belonging to groups 2 and 18) and yttrium in the spherical magnesium oxide after final firing is 500 to 12,000 ppm.

[0031] The total content of elements belonging to Periods 3 and 4 of the Periodic Table (excluding elements belonging to Groups 2 and 18) and yttrium can be adjusted, specifically, by a) adding a compound containing the above element to an aqueous magnesium salt solution and / or an aqueous carbonate solution, b) adding a compound containing the above element to the obtained spherical magnesium carbonate slurry, or c) mixing a compound containing the above element with the obtained spherical magnesium carbonate particles, thereby adjusting the content in the finally obtained spherical magnesium oxide.

[0032] For example, it can be produced as follows.

[0033] 1) reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then agglomerating the resulting magnesium carbonate to obtain a spherical magnesium carbonate slurry, 2) filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles, and 3) firing the spherical magnesium carbonate particles in air to obtain the target spherical magnesium oxide, in which the amount of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) is adjusted by addition, mixing, etc., before the final firing so that the total content of elements belonging to periods 3 and 4 of the periodic table (excluding elements belonging to groups 2 and 18) in the spherical magnesium oxide after final firing is 500 to 12,000 ppm.

[0034] The total content of elements belonging to Periods 3 and 4 of the Periodic Table (excluding elements belonging to Groups 2 and 18) can be adjusted by, for example, a) adding a compound containing the element to an aqueous magnesium salt solution and / or an aqueous carbonate solution, b) adding a compound containing the element to the obtained spherical magnesium carbonate slurry, or c) mixing a compound containing the element with the obtained spherical magnesium carbonate particles, thereby adjusting the content in the spherical magnesium oxide finally obtained.

[0035] The compound used for the above-mentioned addition, mixing, etc. is not particularly limited as long as it is a compound containing an element belonging to Period 3 or Period 4 of the periodic table (excluding elements belonging to Groups 2 and 18). In addition, with regard to yttrium, it is not particularly limited as long as it is a compound containing yttrium.

[0036] The aluminum source is not particularly limited as long as it is a compound containing aluminum, and examples that can be used include aluminum hydroxide, aluminum oxide, aluminum carbonate, aluminum chloride, aluminum nitrate, aluminum acetate, and aluminum sulfate.

[0037] The silicon source is not particularly limited as long as it is a compound containing silicon, and examples thereof include silicon oxide, silicates, etc. Examples of silicon oxide include crystalline silica, amorphous fumed silica, colloidal silica, etc. Examples of silicates include sodium silicate, magnesium silicate, potassium silicate, calcium silicate, etc.

[0038] The phosphorus source is not particularly limited as long as it is a compound containing phosphorus, and examples thereof include phosphoric acid, phosphates, etc. Examples of phosphates include magnesium phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate.

[0039] The chlorine source is not particularly limited as long as it is a compound containing chlorine, and examples thereof include sodium chloride, magnesium chloride, potassium chloride, and calcium chloride.

[0040] The bromine source is not particularly limited as long as it is a compound containing bromine, and examples thereof include sodium bromide, magnesium bromide, potassium bromide, and calcium bromide.

[0041] The sodium source is not particularly limited as long as it is a compound containing sodium, and examples thereof include sodium chloride, sodium carbonate, sodium phosphate, sodium hydroxide, and sodium nitrate.

[0042] The potassium source is not particularly limited as long as it is a compound containing potassium, and examples thereof include potassium chloride, potassium carbonate, potassium phosphate, potassium hydroxide, and potassium nitrate.

[0043] The titanium source is not particularly limited as long as it is a compound containing titanium, and examples thereof include titanium oxide (anatase type, rutile type), titanium chloride, titanium hydroxide, titanium bromide, titanium fluoride, magnesium titanate, and the like.

[0044] The manganese source is not particularly limited as long as it is a compound containing manganese, and examples thereof include manganese dioxide, manganese hydroxide, manganese carbonate, manganese chloride, and manganese nitrate.

[0045] The yttrium source is not particularly limited as long as it is a compound containing yttrium, and examples thereof include yttrium oxide, yttrium chloride, and yttrium nitrate.

[0046] It is also preferable to control the boron content of the spherical magnesium oxide after final calcination to less than 10 ppm, the lithium content to less than 15 ppm, and the calcium content to less than 700 ppm. The method for reducing the boron, lithium, and calcium contents is not particularly limited, but known processes such as repulp washing, which involves repeatedly reslurrying the precursor magnesium carbonate cake and filtering it, followed by water washing, pretreating the magnesium salt aqueous solution with an adsorbent, and adjusting the temperature rise profile during calcination, or a combination of these processes can be used. The contents of the above elements can also be controlled low by selecting raw materials that do not contain these elements and appropriately managing the possibility of their inclusion during the manufacturing process.

[0047] The magnesium salt in the aqueous magnesium salt solution is not particularly limited, but may be selected from, for example, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium acetate, and combinations thereof.

[0048] The carbonate in the carbonate aqueous solution is not particularly limited, but may be selected from, for example, sodium carbonate, potassium carbonate, ammonium carbonate, and combinations thereof.

[0049] The magnesium salt concentration of the magnesium salt aqueous solution is preferably 1 to 30 mass %, and the carbonate concentration of the carbonate aqueous solution is preferably 1 to 30 mass %. The reaction between the magnesium salt aqueous solution and the carbonate aqueous solution may be carried out, for example, by the reaction of [Mg ２＋ ]: [CO ３ ２－ The ion concentration ratio of the above ions can be 1.2:1 to 1:1.5.

[0050] In the method for producing spherical magnesium oxide of the present invention, first, an aqueous magnesium salt solution is reacted with an aqueous carbonate solution, and then the resulting magnesium carbonate is agglomerated to obtain spherical magnesium carbonate slurry. Here, the magnesium carbonate produced by the reaction of the aqueous magnesium salt solution with the aqueous carbonate solution is heated to a temperature of, for example, 60 to 100°C and maintained for 0.1 to 5 hours, and the volume-based cumulative 50% particle diameter (D ５０ The particles can be appropriately aggregated into spherical particles having a diameter of 1 to 200 μm and a sphericity of 1.00 to 1.30.

[0051] The spherically agglomerated magnesium carbonate slurry is filtered, washed with water, and dried, for example, by a method commonly used in the art, to form spherical magnesium carbonate particles.

[0052] The magnesium carbonate particles obtained by the above production method may be any of anhydrous magnesium carbonate, normal magnesium carbonate, and basic magnesium carbonate, but are preferably basic magnesium carbonate.

[0053] The firing conditions for the spherical magnesium carbonate particles are not particularly limited as long as they are within a range in which magnesium carbonate thermally decomposes to magnesium oxide, but for example, the temperature is preferably 1000°C to 1800°C, more preferably 1100°C to 1700°C, and particularly preferably 1200°C to 1600°C. The firing time depends on the firing temperature, but is preferably 0.5 to 10 hours, for example. If the firing temperature is less than 1000°C, the particles will not be sufficiently sintered, and if it exceeds 1800°C, the particles will sinter together and form coarse aggregates, so the temperature is adjusted to be within the above range.

[0054] The spherical magnesium oxide of the present invention is characterized by having sufficient moisture resistance even without surface treatment, but can also be surface-treated using a known method to further improve moisture resistance. When surface-treating the spherical magnesium oxide of the present invention, the surface treatment agent used is not particularly limited, 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, and zirconium-based coupling agents.

[0055] Examples of silane coupling agents include vinyltrichlorosilane, vinyltrialkoxysilane, glycidoxypropyltrialkoxysilane, and methacryloxypropylmethyldialkoxysilane.

[0056] Examples of titanate coupling agents include tetraisopropyl titanate, tetra-normal-butyl titanate, tetraoctyl titanate, tetrastearyl titanate, isopropyl triisostearoyl titanate, tetraoctylbis(ditridecylphosphite)titanate, and bis(dioctylpyrophosphate)oxyacetate titanate.

[0057] 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-based compound, and examples thereof include phosphoric acid, phosphates, and acidic phosphate esters. These may be used alone or in combination of two or more. Examples of 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.

[0058] Examples of the aluminate coupling agent include aluminum isopropylate, monosec-butoxyaluminum diisopropylate, aluminum sec-butylate, aluminum ethylacetoacetate diisopropylate, aluminum tris(ethylacetoacetate), and aluminum alkylacetoacetate diisopropylate.

[0059] Examples of zirconium-based coupling agents include normal propyl zirconate and normal butyl zirconate.

[0060] The spherical magnesium oxide of the present invention has high sphericity, excellent moisture resistance, and excellent fillability into resins, and therefore can be suitably blended into resins as a filler and is useful as a resin filler, such as a thermally conductive filler, a heat-resistant filler, a gas-barrier filler, or a light-resistant filler, and is particularly suitable as a thermally conductive filler.

[0061] Resins that can be used in the present invention include, for example, thermosetting resins and thermoplastic resins. Thermosetting resins are not particularly limited, but examples thereof 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 thereof 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.

[0062] The amount of spherical magnesium oxide to be added to the resin composition of the present invention is not particularly limited and may be determined appropriately depending on the properties required of the resin composition, but may be, for example, in the range of 0.1 to 100 parts by mass of spherical magnesium oxide per 100 parts by mass of resin.

[0063] The resin composition containing the spherical magnesium oxide of the present invention can be used in various fields depending on the properties of the resin.

[0064] The present invention will be described in detail with reference to the following examples, but these examples are not intended to limit the present invention in any way.

[0065] <Measurement method and evaluation method> (1) Measurement method of element content The element content was measured by ICP atomic emission spectroscopy. The measurement sample was added to acid and completely dissolved, and then the content of each element was measured using an ICP measurement device (PS3520 VDD, manufactured by Hitachi High-Tech Science Corporation). In Tables 1 and 2 below, when the content of each element was below the detection limit, it was expressed as a trace amount of <1 ppm.

[0066] (2) Method for Measuring BET Specific Surface Area The BET specific surface area was measured by a gas adsorption method (BET method) using nitrogen gas using a specific surface area measuring device (Macsorb, manufactured by Mountech Co. Ltd.).

[0067] (3) Volume-based cumulative 50% particle diameter (D ５０ ) Measurement sample 0.1 x 10 －３ kg was precisely weighed, dispersed in 40 mL of methanol, and measured using a laser diffraction scattering particle size distribution measuring device (MT3300, manufactured by Nikkiso Co., Ltd.).

[0068] (4) Sphericity and surface smoothness readable from SEM photographs A scanning electron microscope (SEM) (JSM6510LA, manufactured by JEOL Ltd.) was used. For 100 particles in the electron microscope photographs, the lengths of the major axis and minor axis passing through the center of the particle were measured to determine the ratio of the major axis to the minor axis, and the average value was taken as the sphericity. Furthermore, the surface condition of the spherical magnesium oxide in the electron microscope photographs taken with the scanning electron microscope (SEM) was evaluated as follows: ◯: a spherical magnesium oxide surface with almost no fine particles present and a smooth surface; Δ: a spherical magnesium oxide surface with a plurality of fine particles present but a smooth surface, or a spherical magnesium oxide surface with almost no fine particles present but an uneven and non-smooth surface; and ×: a spherical magnesium oxide surface with a plurality of fine particles present and an uneven and non-smooth surface.

[0069] (5) Evaluation of Moisture Resistance by Constant Temperature and Humidity Test The moisture resistance of the spherical magnesium oxide was evaluated by the mass gain rate in a constant temperature and humidity test. The thermo-hygrometer THN040FA manufactured by Advantec Toyo Co., Ltd. was used. 10 g of spherical magnesium oxide was exposed to an environment of 85°C and 85% RH for 168 hours using the thermo-hygrometer, and the mass gain rate was then determined.

[0070] Example 1 Magnesium nitrate hexahydrate (special grade, manufactured by Kanto Chemical Co., Ltd.) was dissolved in ion-exchanged water to prepare an approximately 20% by mass aqueous solution of magnesium nitrate. Potassium carbonate (special grade, manufactured by Kanto Chemical Co., Ltd.) was dissolved in ion-exchanged water to prepare an approximately 15% by mass aqueous solution of potassium carbonate. [Mg ２＋ ]: [CO ３ ２－ Magnesium carbonate was synthesized by reacting an aqueous magnesium nitrate solution with an aqueous potassium carbonate solution so that the ion concentration ratio of the magnesium nitrate and potassium carbonate solutions was 1:1. After the reaction, the magnesium carbonate slurry was heated to 90°C and held for 1 hour to prepare a spherical magnesium carbonate slurry. Silicon dioxide (special grade, manufactured by Kanto Chemical Co., Ltd.) was added to the slurry so that the silicon content in the finally obtained spherical magnesium oxide was 2,500 ppm, and the slurry was then filtered, washed with water, and dried to obtain spherical magnesium carbonate particles. The obtained spherical magnesium carbonate particles were fired in an electric furnace at 1,500°C for 1 hour to obtain spherical magnesium oxide particles. The particle diameter (D ５０ ) was 20.5 μm and the sphericity was 1.12.

[0071] Example 2 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that silicon dioxide (special grade, manufactured by Kanto Chemical Co., Ltd.) was added so that the silicon content in the finally obtained spherical magnesium oxide was 5,000 ppm. The particle diameter (D ５０ ) was 20.3 μm and the sphericity was 1.12.

[0072] Example 3 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that aluminum oxide (Kanto Chemical Co., Ltd., Deer Special Grade) was added instead of silicon dioxide so that the aluminum content in the finally obtained spherical magnesium oxide was 2,500 ppm. The particle diameter (D ５０ ) was 20.2 μm and the sphericity was 1.13.

[0073] Example 4 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that instead of adding silicon dioxide, titanium oxide (Kanto Chemical Co., Ltd., anatase type, Shika Grade 1) was added so that the titanium content in the finally obtained spherical magnesium oxide was 7,500 ppm. The particle diameter (D ５０ ) was 20.5 μm and the sphericity was 1.13.

[0074] Comparative Example 1 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that silicon dioxide was not added. The particle diameter (D ５０ ) was 19.8 μm and the sphericity was 1.12.

[0075] <Results> The above measurements and evaluations were carried out on the spherical magnesium oxides of Examples 1 to 4 and Comparative Example 1. The results are shown in Table 1 below. The content of each element belonging to Periods 3 and 4 of the periodic table other than those shown in Table 1 was 10 ppm or less. The content of yttrium element was also 10 ppm or less.

[0076]

[0077] As is clear from Table 1, the spherical magnesium oxides of Examples 1 to 4 had high sphericity and excellent moisture resistance. On the other hand, the spherical magnesium oxide of the comparative example was poor in both sphericity and moisture resistance.

[0078] Furthermore, spherical magnesium oxide particles of Examples 5 to 9 were obtained as described below, and measurements and evaluations were carried out in the same manner as in Examples 1 to 4 and Comparative Example 1.

[0079] Example 5 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that silicon dioxide (special grade, manufactured by Kanto Chemical Co., Inc.) was added so that the silicon content in the finally obtained spherical magnesium oxide would be 700 ppm, and the firing temperature was set to 1600°C.

[0080] Example 6 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that silicon dioxide (special grade, manufactured by Kanto Chemical Co., Inc.) was added so that the silicon content in the finally obtained spherical magnesium oxide would be 11,500 ppm, and the firing temperature was set to 1600°C.

[0081] Example 7 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that instead of adding silicon dioxide, sodium tripolyphosphate (Kanto Chemical Co., Ltd., Deka Grade 1) was added so that the phosphorus content in the finally obtained spherical magnesium oxide would be 1,200 ppm, and the firing temperature was set to 1,600°C.

[0082] Example 8 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that instead of adding silicon dioxide, manganese chloride tetrahydrate (special grade, manufactured by Kanto Chemical Co., Inc.) was added so that the manganese content in the finally obtained spherical magnesium oxide would be 9,000 ppm, and the firing temperature was set to 1600°C.

[0083] Example 9 Spherical magnesium oxide was obtained in the same manner as in Example 1, except that instead of adding silicon dioxide, yttrium nitrate hexahydrate (high-purity reagent manufactured by Kanto Chemical Co., Inc.) was added so that the yttrium content in the finally obtained spherical magnesium oxide would be 4,500 ppm, and the firing temperature was set to 1600°C.

[0084] <Results> Measurements and evaluations were carried out for the spherical magnesium oxides of Examples 5 to 9 in the same manner as in Examples 1 to 4 and Comparative Example 1. The results are shown in Table 2 below. Note that the content of each element belonging to Periods 3 and 4 of the periodic table other than those shown in Table 2 was 10 ppm or less in all cases.

[0085]

[0086] As is clear from Table 2, the spherical magnesium oxide particles of Examples 5 to 9 had high sphericity and excellent moisture resistance.

[0087] This indicates that the spherical magnesium oxide of the present invention has high sphericity and excellent moisture resistance, and is therefore useful as an excellent resin filler.

[0088] The spherical magnesium oxide of the present invention has high sphericity and excellent moisture resistance, and is therefore useful as an excellent resin filler.

Claims

1. The total content of elements belonging to the 3rd to 4th periods of the periodic table (excluding elements belonging to Group 2 and Group 18) and yttrium is 500 to 12,000 ppm, and the volume-based cumulative 50% particle diameter (D ５０ ), as measured by laser diffraction scattering type particle size distribution measurement, is in the range of 1 to 200 μm, and the sphericity read from the SEM photograph is 1.00 to 1.

20. Spherical magnesium oxide is characterized by this.

2. The total content of elements belonging to the 3rd to 4th periods of the periodic table (excluding elements belonging to Group 2 and Group 18) is 500 to 12,000 ppm, and the volume-based cumulative 50% particle size (D ５０ ), as measured by laser diffraction scattering particle size distribution measurement, is in the range of 1 to 200 μm, and the sphericity read from the SEM photograph is 1.00 to 1.

20. Spherical magnesium oxide is characterized by this.

3. The spherical magnesium oxide according to claim 1 or 2, wherein the element belonging to the 3rd to 4th periods of the periodic table is at least one selected from the group consisting of sodium, aluminum, silicon, phosphorus, chlorine, potassium, and titanium.

4. The spherical magnesium oxide according to claim 1 or 2, wherein the boron content is less than 10 ppm.

5. The spherical magnesium oxide according to claim 1 or 2, wherein the lithium content is less than 15 ppm.

6. The spherical magnesium oxide according to claim 1 or 2, wherein the calcium content is less than 700 ppm.

7. Cumulative 50% particle diameter (D ５０ ) is in the range of 5 to 100 μm, the spherical magnesium oxide according to claim 1 or 2.

8. The BET specific surface area is 0.01 to 1.00 m ２ / g, and the spherical magnesium oxide according to claim 1 or 2.

9. A resin filler containing the spherical magnesium oxide according to claim 1 or 2.

10. A resin composition containing the resin filler according to claim 9.

11. 1) A step of reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then aggregating the produced magnesium carbonate to obtain a spherical magnesium carbonate slurry; 2) A step of filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles; 3) A step of firing the spherical magnesium carbonate particles to obtain spherical magnesium oxide; The method for producing spherical magnesium oxide includes the above steps 1) to 3). In at least one of the steps 1) to 3), the total content of the elements belonging to the 3rd to 4th periods of the periodic table (excluding the elements belonging to Group 2 and Group 18) and yttrium in the spherical magnesium oxide after firing is adjusted to be 500 to 12,000 ppm so that the amounts of the elements belonging to the 3rd to 4th periods of the periodic table (excluding the elements belonging to Group 2 and Group 18) and yttrium are adjusted.

12. 1) A step of reacting an aqueous magnesium salt solution with an aqueous carbonate solution, and then aggregating the produced magnesium carbonate to obtain a spherical magnesium carbonate slurry; 2) A step of filtering, washing with water, and drying the spherical magnesium carbonate slurry to obtain spherical magnesium carbonate particles; 3) A step of firing the spherical magnesium carbonate particles to obtain spherical magnesium oxide; including, in at least one or more of the steps of 1) to 3) above, adjusting the amount of elements belonging to the 3rd to 4th periods of the periodic table (excluding elements belonging to Group 2 and Group 18) in the spherical magnesium oxide after firing so that the total content is 500 to 12,000 ppm, a method for producing spherical magnesium oxide, characterized by this adjustment.