Method for producing spherical particulate material

Abstract

The present invention addresses the problem to be solved of providing a method for manufacturing a spherical particle material by a melting method, the manufacturing method being capable of enhancing a melting spheroidization ratio more than conventional methods.　For raw material subjected to a melting method, it has been found that the powder compressibility evaluation FF value from a powder rheometer correlates with the level of the melting spheroidization ratio, and the following invention has been completed accordingly. The method for manufacturing a spherical particle material according to the present invention to solve the above problem involves a raw particle material preparation step for preparing a raw particle material formed from an inorganic material, and a spheroidization step for placing the raw particle material in a high-temperature atmosphere to melt same and then quickly cooling same to prepare a spherical particle material with a volume average particle diameter of 1 μm or more and less than 10 μm, wherein the raw particle material has a powder compressibility evaluation FF value from a powder rheometer of 2.0 or more.

Description

[Technical field]

[0001] The present invention relates to a method for producing a spherical particulate material. [Background technology]

[0002] Spherical particulate materials made of inorganic materials are used as fillers for electronic materials, such as fillers to be contained in sealing materials for semiconductors and substrate materials. Various requirements are placed on the spherical particulate materials with respect to particle size distribution, circularity, purity, etc.

[0003] Typical methods for producing spherical particulate materials from conventional inorganic materials include, when the inorganic material is a metal oxide, a method in which a metal particulate material made of the metal that constitutes the metal oxide is placed in a high-temperature oxidizing atmosphere, deflagrated, and then rapidly cooled (VMC method), and a method in which a particulate material made of the inorganic material is placed in a high-temperature atmosphere and then rapidly cooled (melting method). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-182714 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the VMC method, the particle size distribution of the generated spherical particle material can be controlled by controlling the particle size distribution and the input speed of the metal particle material, but the control range is not completely flexible. It is particularly difficult to expand the control range when producing alumina by the VMC method.

[0006] Therefore, when we investigated a melting method that allows some control over the spherical particulate material produced by controlling the particle size distribution of the raw particulate material, we found that although the particle size distribution of the spherical particulate material produced can be controlled by the particle size distribution of the raw particulate material, melting was not always complete. For example, when alumina particulate material was spheroidized by the melting method, some of the material was not melted. The degree to which the raw particulate material has been melted is referred to as the melting spheroidization rate (details will be described later).

[0007] Furthermore, a method has been disclosed in which a large particle material produced by granulating a small particle material is used as the raw material for the melting process to control the particle size distribution (Patent Document 1). However, there have been cases where it has been difficult to obtain a spherical particle material having a desired particle size distribution due to problems such as the destruction of the granulated particle material.

[0008] The present invention was completed in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a method for producing a spherical particulate material by a melting method, which can achieve a higher melt spheroidization rate than conventional methods. [Means for solving the problem]

[0009] Means for Solving the Problems The present inventors have conducted intensive research in order to solve the above problems, and as a result have found that the powder compressibility evaluation FF value, measured by a powder rheometer, for raw materials subjected to a melting method correlates with the melt spheroidization rate, and have completed the following invention.

[0010] The method for producing a spherical particulate material of the present invention, which solves the above problems, comprises: a raw material particulate material preparation step of preparing a raw material particulate material made of an inorganic material; a spheroidizing step of melting the raw material particles in a high-temperature atmosphere and then quenching the melted raw material particles to prepare spherical particles having a volume average particle size of 1 μm or more and less than 10 μm; having The raw particle material has a powder compressibility evaluation FF value of 2.0 or more as measured by a powder rheometer.

[0011] The powder compressibility evaluation FF value (hereinafter, simply referred to as "FF value" in this specification) means a fluidity index, and is a value calculated by maximum principal stress (MPS) / uniaxial collapse stress (UYS). Specifically, it is a value measured by a shear stress test using a powder fluidity analyzer, Powder Rheometer FT4, manufactured by Freeman Technology. Effect of the Invention

[0012] The method for producing a spherical particulate material of the present invention has the above-mentioned configuration, and thus makes it possible to obtain a spherical particulate material having a high melt spheroidization rate or a small specific surface area, and can provide a spherical particulate material that is preferable when incorporated as a filler in a resin composition. [Brief description of the drawings]

[0013] [Figure 1] 1 is a graph showing the particle size distribution of raw particle material in Test 1 of the Example. [Diagram 2] 1 is a SEM photograph of the raw particle material in Test 1 of the embodiment. [Diagram 3] 1 is a graph showing the particle size distribution of a spherical particle material in Test 1 of the embodiment. [Figure 4] 1 is a SEM photograph of a spherical particle material in Test 1 of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The method for producing a spherical particulate material of the present invention will be described in detail below based on the embodiment. The spherical particles produced by the method for producing a spherical particulate material of the present embodiment can be filled as a filler in a resin material to form a resin composition. The resin composition is suitable for use as an electronic material.

[0015] The method for producing a spherical particulate material of this embodiment includes a raw material particle material preparation step, a spheroidization step, and other steps selected as necessary. The spherical particulate material produced by the method for producing a spherical particulate material of this embodiment is composed of an inorganic material and has a volume average particle size of 1 μm or more and less than 10 μm. Examples of the lower limit value of the volume average particle size are 1 μm, 2 μm, and 3 μm, and examples of the upper limit value are 4 μm, 5 μm, and 6 μm. These lower limit values ​​and upper limit values ​​can be combined arbitrarily.

[0016] The spherical particle material produced by the production method of this embodiment has a circularity of 0.9 or more, preferably 0.95 or more, more preferably 0.98 or more, and even more preferably 0.99 or more. The circularity in this specification is calculated by taking a photograph with an SEM, and calculating the circularity from the area and perimeter of the observed particle, as follows: (Circularity) = {4π × (Area) ÷ (Perimeter)} 2 The closer to 1, the closer to a perfect sphere. Specifically, the average value measured for 100 particles using image analysis software (Asahi Kasei Engineering Corporation: A-zo-kun) is used.

[0017] The inorganic material constituting the spherical particle material of this embodiment is not particularly limited, but is preferably a metal oxide, particularly, alumina, silica, titania, zirconia, magnesia, and composite oxides thereof. As the inorganic material, it is particularly preferable that the above-mentioned metal oxides are contained alone or in combination in an amount of 50% or more based on the total mass, and it is more preferable that the inorganic material contains alumina in an amount of 50% or more.

[0018] The inorganic material preferably has a total content of alkali metals and alkaline earth metals as impurities of 5 ppm or less, more preferably 3 ppm or less, and even more preferably 1 ppm or less. In particular, the content of Na is preferably 5 ppm or less, more preferably 3 ppm or less, and even more preferably 1 ppm or less.

[0019] Furthermore, the inorganic material preferably has a total content of U and Th as impurities of 5 ppb or less, more preferably 3 ppb or less, and even more preferably 1 ppb or less.

[0020] When the inorganic material is alumina, the specific surface area is 1.0 m 2 / g or less, and 0.8m 2 / g or less is more preferable. And the melt spheroidization rate is preferably 85% or more. The lower limit of the melt spheroidization rate can be 88%, 90%, 92%, 94%, 95%, 96%, 97%, 98%, or 99%. The method for measuring the melt spheroidization rate will be described later in the Examples.

[0021] ·Raw material particle preparation process The raw particle material preparation step is a step of preparing a raw particle material made of an inorganic material. The inorganic material can be the same as the inorganic material constituting the spherical particle material to be produced. The raw particle material has a powder compressibility evaluation FF value of 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more, and even more preferably 4.0 or more, as measured by a powder rheometer.

[0022] The FF value can be controlled by the particle shape, surface treatment, and particle size distribution of the raw particle material. When the content of particles having a particle size smaller than 1 μm is 2% or more based on the mass of the entire raw particle material, the FF value can be increased by decreasing the circularity of the raw particle material. In this case, the circularity is preferably 0.9 or less, more preferably 0.88 or less, and even more preferably 0.85 or less. When the content of particles having a particle size smaller than 1 μm is 2% or less based on the mass of the entire raw particle material, conversely, it is better for the circularity of the raw particle material to be high. In this case, it is preferably 0.85 or more, more preferably 0.88 or more, and even more preferably 0.90 or more.

[0023] For the surface treatment, it is preferable to use a surface treatment agent capable of introducing a trimethylsilyl group, an isocyanate group, an amino group, or a phenyl group as a functional group. For example, an aluminate coupling agent or a silane compound having the functional group to be introduced can be reacted (surface treatment step).

[0024] Examples of aluminate coupling agents include acetoalkoxyaluminum diisopropylate, aluminum alkyl acetoacetate diisopropylate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, aluminum isopropylate, aluminum diisopropylate mono-sec-butylate, aluminum secondary butylate, aluminum ethylate, aluminum bisethyl acetoacetate monoacetylacetonate, aluminum trisacetylacetonate, and aluminum monoisopropoxymonoroxyethyl acetoacetate.

[0025] The surface treatment is preferably carried out to such an extent that the FF value is 2.0 or more. For example, the treatment amount is preferably about 0.5 μmol to 10 μmol based on the mass of the raw particle material, and examples of the lower limit value include about 0.6 μmol and 0.7 μmol, and examples of the upper limit value include about 6.0 μmol and 7.0 μmol. These lower limit values ​​and upper limit values ​​can be arbitrarily combined.

[0026] Regarding particle size distribution, the smaller the dispersion of the particle size distribution, the higher the FF value. For example, D90 / D10 is preferably 1.5 or less, and more preferably 1.2 or less. To reduce the dispersion, it is preferable to make the particle size of the raw material particles uniform, or to remove particles with a particle size smaller than 1 μm. To remove such small particles, a general method can be used, such as a cyclone method, a sieve method, or a method based on the difference in sedimentation speed in a fluid.

[0027] A particle material having a volume average particle size larger than the volume average particle size required for the raw material particle material is used as the coarse raw material particle material, and a grinding operation is performed to obtain a raw material particle material having the required volume average particle size. For example, the particle size distribution can be adjusted after grinding the coarse raw material particle material. Alternatively, instead of or in addition to adjusting the particle size distribution after grinding, the particle size distribution can be adjusted before grinding. For adjusting the particle size distribution, it is particularly preferable to remove particles having small particle sizes as described above.

[0028] The crude raw material particle material is preferably produced by the VMC method (deflagration process). The particle material produced by the VMC method can also be used as the raw material particle material as it is. The deflagration process is a process for preparing a raw material particle material or a crude raw material particle material by deflagrating a metal particle material made of a metal (metallic aluminum, etc.) that constitutes a metal oxide in a high-temperature oxidizing atmosphere.

[0029] For example, when alumina is produced by the VMC process, a mixture of large and small particle material is obtained, and the large particle fraction can be classified and used as the raw material particle material.

[0030] The pulverization method is not particularly limited, but general pulverization methods such as jet mill, ball mill, and vibrating ball mill can be used. In particular, jet mills are preferred because they are less likely to be contaminated by impurities derived from the media used in pulverization, and also have high pulverization efficiency on the order of micrometers. The particulate material produced by the VMC method has a high degree of circularity, and may contain a certain amount of particles with a particle size smaller than 1 μm in the particle size distribution. Therefore, the FF value tends to increase by reducing the circularity through pulverization.

[0031] It is preferable to use the particulate material made of metal oxide produced by the VMC method as the crude raw material particulate material either as is or after classification, because the metal constituting the metal particulate material used as the raw material for the VMC method is easier to purify than the metal oxide, and therefore it is easy to increase the purity of the raw material particulate material obtained via the VMC method.

[0032] The amount of impurities (alkali metals, alkaline earth metals, Na, U, Th, etc.) in the metal particulate material is preferably equal to or less than that of the inorganic material constituting the spherical particulate material of this embodiment described above.

[0033] ·Spheroidization process The spheroidization process is similar to a method for producing spherical particulate material, called a melting process, in which the raw particulate material is melted by introducing the raw particulate material into a high-temperature atmosphere and then rapidly cooled to produce spherical particulate material.

[0034] The temperature of the high-temperature atmosphere is equal to or higher than the melting point of the inorganic material constituting the raw material particle material. When the inorganic material constituting the raw material particle material is alumina, the temperature is preferably 2000° C. or higher, and more preferably 3000° C. or higher.

[0035] A preferred method for forming a high-temperature atmosphere is to use a flame formed by burning a combustible gas together with a combustion supporting gas. Examples of the combustible gas include a hydrocarbon gas such as propane or natural gas, hydrogen gas, or ammonia gas. Examples of the combustion supporting gas include oxygen or air.

[0036] A flame is formed inside the furnace, and the raw material particles are charged into the furnace in a state where they are dispersed in an appropriate carrier (gas or liquid). By lowering the concentration of the raw material particles dispersed in the carrier so that they do not fuse together, it is possible to obtain spherical particulate material with a particle size distribution similar to that of the raw material particles charged, and by raising the concentration of the raw material particles dispersed in the carrier to the extent that they fuse together, it is possible to obtain spherical particulate material with a particle size distribution shifted to the larger side than that of the raw material particles charged.

[0037] The molten raw material particles are transferred to the outside of the high-temperature atmosphere, where they are rapidly cooled and solidified into spherical particles, which are then collected using a cyclone, bag filter, or the like.

[0038] The spherical particle material thus produced may be subjected to a surface treatment, for example, with the above-mentioned silane compound. EXAMPLES

[0039] The method for producing the spherical particulate material of the present invention will now be described in detail with reference to examples.

[0040] (Test 1) Alumina (manufactured by Admatechs, AO-909, volume average particle size 10 μm: produced in the deflagration process) produced by the VMC method with fine powder removed was used as the raw material particle material. The raw material particle material was pulverized by a jet mill to adjust the particle size distribution (pulverization process), and raw material particle materials with three types of volume average particle sizes, 2.1 μm (Test Example 1-1), 3.0 μm (Test Example 1-2), and 4.1 μm (Test Example 1-3), were obtained (collectively referred to as the raw material particle material preparation process). The obtained raw material particle material was placed in a high-temperature atmosphere (about 2000°C) and quenched to produce spherical particle materials (spheroidization process).

[0041] For the raw material particles of each test example, the specific surface area was measured by the BET method using nitrogen, the moisture content was measured by the Karl Fischer method (KF moisture content), and the uranium (U) and thorium (Th) contents were measured by an inductively coupled plasma atomic emission spectrometer, and the FF value (including maximum principal stress (MPS) and uniaxial collapse stress (UYS)) were measured, and the results are shown in Table 1. The results of measuring the particle size distribution of the raw material particles of each test example are shown in Figure 1, and SEM photographs are shown in Figure 2.

[0042] The raw material particles of each test example were subjected to a spheroidization process. In the spheroidization process, the raw material particles were fed at a rate of 10 kg / h and oxygen was used as a carrier gas at 7.5 Nm 3 The flame was fed with LPG as a combustible gas at a flow rate of 7.5 Nm3 / h. 3 / h and oxygen as a combustion support gas of 9.0 Nm 3 / h. Oxygen 21.0 Nm3 as sheath gas and combustion support gas. 3 / h was flowed in. The raw particulate material was put into the flame, melted, and then rapidly cooled to obtain spherical particulate material. The obtained spherical particulate material was collected using a bag filter. For the spherical particulate material of each test sample, the particle size (D50), mode diameter, specific surface area, KF moisture content, and U and Th content were measured using the methods described above and are shown in Table 1. The results of measuring the particle size distribution of the spherical particulate material of each test example are shown in Figure 3, and SEM photos are shown in Figure 4.

[0043] The melt spheroidization rate was also measured and is shown in Table 1. The melt spheroidization rate was calculated from the following formula, assuming that a completely melted sample (melt spheroidization rate of 100%) is a perfect sphere, and that the closer it is to a perfect sphere, the more melting has progressed.

[0044] Formula (1): (melt spheroidization rate) = [1 - {(specific surface area of ​​spherical particle material) - (specific surface area when the melt spheroidization rate of the spherical particle material is assumed to be 100%)} / {(specific surface area of ​​raw material particle material) - (specific surface area when the melt spheroidization rate of the raw material particle material is assumed to be 100%)}] x 100 (%) (Specific surface area when the melt spheroidization rate of the spherical particle material is assumed to be 100%) = 6 / {(True specific gravity of inorganic material constituting the spherical particle material) × (D50 of the spherical particle material)} (Specific surface area when the melt spheroidization rate of the raw material particle material is assumed to be 100%) = 6 / {(True specific gravity of inorganic material constituting the spherical particle material) × (D50 of the raw material particle material)} Here, the unit of the specific surface area in formula (1) is (m 2 / g), D50 is in (μm), and true specific gravity is in (g / cm 3 ).

[0045] [Table 1]

[0046] As is clear from the table, the spherical particle material produced from the raw particle material of Test Example 1-3, which had an FF value of 3.0 or more, had a melt spheroidization rate close to 100% and a small specific surface area. Also, the spherical particle material produced from the raw particle material of Test Example 1-2, which had an FF value of 2.0 or more, had a slightly smaller melt spheroidization rate than the spherical particle material produced from the raw particle material of Test Example 1-1, which had an FF value of less than 2.0, but had a significantly smaller specific surface area. Basically, the individual spherical particle materials of each test example have a high circularity, so a large specific surface area means that the content ratio of particles with a smaller diameter than D50 is high, that is, the dispersion is large.

[0047] As is clear from Figure 1, the raw particle material of Test Example 1-1 has a large peak of about 1 μm and a shoulder peak of about 4 μm, has a large content of particles with relatively small diameters, and has a broad particle size distribution. Therefore, the spherical particle material of Test Example 1-1 also has a large content of particles with relatively small diameters, and has a wide particle size distribution. This is also clear from the SEM photograph in Figure 4. As is clear from Figures 1 and 2, the raw particle materials of Test Examples 1-2 and 1-3 have narrower particle size distributions than the raw particle material of Test Example 1-1.

[0048] As is clear from FIG. 3, the spherical particulate material of Test Example 1-1 has a broader particle size distribution than the spherical particulate materials of Test Examples 1-2 and 1-3, and also has a larger specific surface area than the spherical particulate materials of Test Examples 1-2 and 1-3.

[0049] (Test 2) The crude raw material particle material was prepared by removing fine powder from alumina (AO-909, manufactured by Admatechs, volume average particle size 10 μm) produced by the VMC method. The crude raw material particle material was pulverized by a jet mill to adjust the particle size distribution, and raw material particle materials with two volume average particle sizes of 2.0 μm (Test Example 2-1) and 4.1 μm (Test Example 2-2) were obtained. The obtained raw material particle material was surface-treated by reacting it with an aluminum-based coupling agent (Plenact AL-M, acetoalkoxyaluminum diisopropylate, manufactured by Ajinomoto Fine-Techno Co., Ltd.) or hexamethyldisilazane (HMDS) as a surface treatment agent. The amount of the surface treatment agent is shown in Table 2.

[0050] For the raw material particles of each test example, Cohesion, UYS, and MPS were measured using a powder rheometer and are shown in Table 2. The FF value was calculated from UYS and MPS and is shown in Table 2.

[0051] [Table 2]

[0052] As is clear from the table, for the sample with a particle size of 1.5 μm, the FF value was improved in the surface-treated test examples 2-2 to 2-5 compared to the test example 2-1 that was not surface-treated. In particular, the FF value was improved in the test example 2-5 that was treated with HMDS compared to the test example that was treated with an aluminum-based coupling agent. For the aluminum-based coupling agent, almost no change in the FF value was observed even when the amount of treatment was changed.

[0053] For the sample with a particle size of 3.0 μm, no improvement in the FF value was observed even in Test Example 2-7, which was surface-treated with HMDS, a highly effective surface treatment agent, compared to Test Example 2-6, which was not surface-treated. In other words, it was found that the effect of surface treatment is reduced when the particle size is large.

Claims

1. A raw material particle material preparation step of preparing a raw material particle material made of an inorganic material containing 50 mass% or more of alumina; a spheroidizing step of melting the raw material particles in a high-temperature atmosphere and then quenching the melted raw material particles to prepare a spherical particle material having a volume average particle size of 1 μm or more and less than 10 μm; having The raw material particle preparation step includes a grinding step of grinding a spherical coarse raw material particle material made of the inorganic material and having a volume average particle size larger than that of the raw material particle material so that the content of particles having a particle size smaller than 1 μm is 2% or more based on the mass of the entire raw material particle material and the sphericity is 0.9 or less, thereby making the powder compressibility evaluation FF value by a powder rheometer 2.0 or more. A method for producing a spherical particulate material.

2. The raw material particle material preparation step includes a surface treatment step of performing a surface treatment on the raw material particle material with a surface treatment agent, The method for producing a spherical particulate material according to claim 1 , wherein the surface treatment step is combined with the pulverization step so that a powder compressibility evaluation FF value by a powder rheometer is 2.0 or more.

3. The spherical particle material prepared in the spheroidizing step consists of only alumina, The method for producing a spherical particulate material according to claim 2, wherein the surface treatment agent is an aluminate-based coupling agent.

4. The method for producing a spherical particulate material according to any one of claims 1 to 3, wherein the raw material particle material preparation process includes a deflagration process for preparing the raw material particle material by deflagrating a metal particle material made of metallic aluminum in a high-temperature oxidizing atmosphere.

5. The metal particle material has a Na content of 5 ppm or less, The method for producing a spherical particulate material according to claim 4, wherein the spherical particulate material has a Na content of 5 ppm or less.

6. The metal particle material has a total content of U and Th of 5 ppb or less, The method for producing a spherical particulate material according to claim 4, wherein the spherical particulate material has a total content of U and Th of 5 ppb or less.

7. The metal particle material has a total content of U and Th of 5 ppb or less, The method for producing a spherical particulate material according to claim 5, wherein the spherical particulate material has a total content of U and Th of 5 ppb or less.

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