Spherical Silica Powder

Abstract

A spherical silica powder according to the present embodiment has a NO3 - content of 5 ppm or less as determined on the basis of an ion chromatography method.

Description

[Technical Field]

[0001] The present invention relates to a spherical silica powder. [Background technology]

[0002] Various developments have been made so far regarding spheres. For example, a technique described in Patent Document 1 is known as a technique of this type. Patent Document 1 describes a method for obtaining molten spherical silica by injecting a siliceous raw material powder into a flame to melt it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-191317 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the fused spherical silica described in Patent Document 1 leaves room for improvement in terms of production stability of the resin composition. [Means for solving the problem]

[0005] After further investigation, the inventors found that nitrogen oxides (NOx) may be present in spherical silica powder produced by flame spraying, and that these nitrogen oxides may change the resin properties of a resin composition obtained by blending spherical silica powder into a resin. Based on this finding, the inventors conducted further intensive research and discovered that by keeping the amount of nitrate ions contained in the spherical silica powder at a predetermined value or less, the deterioration of the curing properties of the resin composition can be suppressed, thereby improving its production stability, and thus completed the present invention.

[0006] According to one aspect of the present invention, there is provided the following spherical silica powder.

[0007] 1. NO3 determined based on the following ion chromatography method - A spherical silica powder having a content of 5 ppm or less. (Ion chromatography method) The spherical silica powder is placed in distilled water, heated and cooled, and then centrifuged to obtain the supernatant liquid, which is then used as the extract. - concentration, and NO3 - The concentration is determined by ion chromatography. - Concentration, NO3 - Based on the concentration, the NO2 contained in the spherical silica powder - Content of NO3 - The content is calculated. 2. The spherical silica powder according to 1., The NO2 contained in the spherical silica powder determined based on the ion chromatography method - The content of N2, NO3 - When the content of N2 is N3, N2 and N3 satisfy the relationship 0.05≦N3 / N2≦30. 3. The spherical silica powder according to 1. or 2., In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 10% is defined as D 10 The particle diameter at which the cumulative value reaches 50% is D 50 The particle diameter at which the cumulative value reaches 97% is D 97 When (D 97 -D 10 ) / D 50 is 1.0 or more and 10.0 or less. 4. The spherical silica powder according to any one of 1. to 3., In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 50% is defined as D 50 The particle diameter at which the cumulative value reaches 97% is D 97 When D 97 / D 50is 2.0 or more and 30.0 or less. 5. The spherical silica powder according to any one of 1. to 4., Spherical silica powder with an amorphous rate of 95% or more. 6. The spherical silica powder according to any one of 1. to 5., The SO3 contained in the spherical silica powder can be determined in the same manner as in the ion chromatography method. 2- and SO4 2- A spherical silica powder having a content of each of the above 10 ppm or less. [Effects of the Invention]

[0008] According to the present invention, a spherical silica powder is provided which is excellent in the production stability of resin compositions. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a thermal spraying device used to produce spherical silica powder. DETAILED DESCRIPTION OF THE INVENTION

[0010] The spherical silica powder of this embodiment will be outlined below.

[0011] The spherical silica powder of this embodiment has NO3 - The content is configured to be 5 ppm or less.

[0012] According to the findings of the present inventors, in the process of producing spherical silica powder by flame spraying, for example, by introducing secondary air and appropriately controlling the amount of the introduced air, the temperature in the cyclone or bag filter that collects the powder can be adjusted to a high level, thereby reducing the amount of NO3 - It was found that the content of can be reduced.

[0013] Although the detailed mechanism is unclear, it is known that NOx originates from the nitrogen source contained in the supporting gas, and it is thought that by suppressing condensation on the surface of collected silica particles in cyclones or bag filters controlled in a high-temperature environment, NOx is adsorbed during condensation, preventing NOx from remaining on the surface of the silica particles. For example, it is possible to control the cyclones or bag filters to be in a high-temperature environment by reducing the amount of relatively low-temperature air (cooling medium) introduced as a secondary source and / or by introducing relatively high-temperature combustion exhaust gas as a secondary source.

[0014] Spherical silica powder NO3 - The upper limit of the content is 5 ppm or less, preferably 3 ppm or less, and more preferably 1 ppm or less, which can prevent a decrease in the curability of the resin composition. On the other hand, the NO3 of spherical silica powder - The lower limit of the content is not particularly limited, but may be 0 ppm or more, or 0.01 ppm or more.

[0015] The spherical silica powder contains NO2 as measured by the following ion chromatography method. - The content of N2, NO3 - When the content of N2 is defined as N3, N2 and N3 may be configured to satisfy 0.05≦N3 / N2≦30. The upper limit of N3 / N2 is 30 or less, preferably 20 or less, and more preferably 10 or less. This makes it possible to suppress corrosion of metal materials, such as copper wire corrosion, caused by the resin composition. On the other hand, the lower limit of N3 / N2 is not particularly limited, but may be 0 ppm or more, or 0.01 ppm or more.

[0016] The SO3 content of the spherical silica powder is determined based on the following ion chromatography method. 2- and SO4 2-The content of each of is, for example, 10 ppm or less, preferably 8 ppm or less, and more preferably 6 ppm or less. By forming a part of an electronic device using a resin composition containing such spherical silica powder, it is expected that the reliability of the electronic device can be improved.

[0017] An example of the procedure for the above ion chromatography method will be described. First, put the spherical silica powder into distilled water, put this mixture into a container, shake for 1 minute, leave it at 95°C for 20 hours, then cool. Add water to the container to make up the amount that has evaporated, then centrifuge and collect the supernatant as the extract. Next, the NO2 in the extract - , NO3 - , SO3 2- , and SO4 2- The concentrations of each of the above are measured using ion chromatography. Based on the concentration values ​​obtained by the measurements, the NO2 contained in the spherical silica powder - Content of NO3 - Content of SO3 2- and SO4 2- The contents of each are calculated.

[0018] The volume frequency particle size distribution of the spherical silica powder is measured by a wet laser diffraction scattering method, and the particle size at which the cumulative value reaches 10% in the volume frequency particle size distribution is defined as D 10 The particle diameter at which the cumulative value reaches 50% is D 50 The particle diameter at which the cumulative value reaches 97% is D 97 Let's say.

[0019] (D 97 -D 10 ) / D 50 The upper limit of is, for example, 10.0 or less, preferably 7.0 or less, and more preferably 5.0 or less, whereby the width of the particle size distribution becomes sharper and the flowability can be improved. On the other hand, (D 97 -D 10 ) / D 50The lower limit of is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 2.0 or more, whereby the particle size distribution has a certain width, and moldability can be improved.

[0020] D 97 / D 50 The upper limit of the ratio is, for example, 30.0 or less, preferably 20.0 or less, and more preferably 15.0 or less. This makes the particle size of the coarse particles sharp, thereby suppressing molding defects in resin moldings caused by the coarse particles. By system Cut. On the other hand, D 97 / D 50 The lower limit of is, for example, 2.0 or more, preferably 3.0 or more, and more preferably 5.0 or more, whereby the particle size distribution has a certain width, and fluidity and moldability can be improved.

[0021] The particle size distribution of spherical silica powder is a value based on particle size measurement using laser diffraction light scattering. Measurements can be performed using a particle size distribution analyzer, such as the Model LS-13-230 (manufactured by Beckman Coulter). For measurement, water is used as the solvent, and pretreatment involves dispersing the powder for 1 minute using a homogenizer at 200 W. The PIDS (Polarization Intensity Differential Scattering) concentration is adjusted to 45-55%. The refractive index of water is set to 1.33, while the refractive index of the powder is determined based on the refractive index of the powder material. For example, the refractive index of amorphous silica is set to 1.50.

[0022] A method for producing the spherical silica powder of this embodiment will be described.

[0023] Spherical silica powder, also known as molten spherical particles, is produced by supplying siliceous raw material powder into a high-temperature flame formed by the combustion reaction of a combustible gas and a combustion-supporting gas, and melting and spheroidizing it at a temperature above its melting point. If necessary, the molten spherical particles thus obtained may be classified or sieved.

[0024] An example of a schematic diagram of a thermal spraying device used to produce spherical silica powder is shown in FIG. The thermal spraying device 100 in FIG. 1 is composed of a melting furnace 2 equipped with a burner 1, cyclones 4 and 6 for classifying molten spherical particles generated by high-temperature exhaust gas from the flame by suction with a blower 9, and a bag filter 8 for collecting fine powder that could not be collected by the cyclones 4 and 6. The melting furnace 2 is constructed as a vertical furnace body, but is not limited to this, and may be a horizontal furnace or an inclined furnace that is horizontal and blows out flames horizontally. The hot exhaust gas is cooled by pipes 3, 5, and 7, which are equipped with water-cooled jackets. The blower 9 may be connected to a suction gas amount control valve and a gas exhaust port (not shown). A collected powder removal device (not shown) may be connected to the lower portions of the melting furnace 2, the cyclones 4 and 6, and the back filter 8. The classification can be carried out using known equipment such as a heavy settling chamber, a cyclone, a classifier having a rotor, etc. This classification operation may be carried out during the transportation process of the molten spheroidized product, or may be carried out in a separate line after collecting the molten spheroidized product all at once.

[0025] As the combustible gas, for example, one or more of acetylene, propane, butane, etc. may be used, but propane, butane, or a mixture thereof, which have a relatively small calorific value, are preferred. As the combustion supporting gas, for example, a gas containing oxygen is used. Generally, it is most preferable to use pure oxygen of 99% by weight or more, as it is inexpensive. In order to reduce the calorific value of the gas, an inert gas such as air or argon can be mixed with the combustion supporting gas.

[0026] The spherical silica powder may be either amorphous and / or crystalline.

[0027] The amorphous fraction of the spherical silica powder is preferably 95% or more, and more preferably 97% or more, as measured by the following method. The amorphous fraction is determined by X-ray diffraction analysis using a powder X-ray diffractometer (e.g., Rigaku Corporation, Model MiniFlex) in the 2θ range of 26° to 27.5° with CuKα radiation, and the intensity ratio of specific diffraction peaks is used to determine the amorphous fraction. In the case of siliceous powder, crystalline silica exhibits a main peak at 26.7°, while amorphous silica exhibits no peak. When amorphous and crystalline silica are mixed, a peak height at 26.7° corresponding to the proportion of crystalline silica is obtained. Therefore, the crystalline silica mixing ratio (X-ray diffraction intensity of sample / X-ray diffraction intensity of crystalline silica) is calculated from the ratio of the X-ray intensity of the sample to that of a crystalline silica standard sample, and the amorphous fraction is then calculated using the formula: amorphous fraction (%) = (1 - crystalline silica mixing ratio) × 100.

[0028] The spherical silica powder has a specific surface area S measured by the BET method. B and the theoretical specific surface area S calculated from the particle size distribution C Ratio to (S B / S C ) is preferably, for example, 2.5 or less. A large ratio means that the resin composition contains a large amount of ultrafine particles that cannot be detected by a particle size distribution measuring instrument such as a laser diffraction method. From the viewpoint of suppressing an increase in viscosity when the spherical silica particles are blended into the resin composition, the above S B / S C The value is more preferably 2.5 or less, and particularly preferably 2.0 or less.

[0029] Specific surface area S B is a value based on the BET method, and can be measured using, for example, a "Model 4-SORBU2" (manufactured by Yuasa Ionics Co., Ltd.) as a specific surface area measuring device. Theoretical specific surface area S C The particle size distribution can also be calculated automatically by the particle size distribution analyzer. The principle of this analyzer is as follows: C = 6 / (ρ·D), where D is the area-average particle diameter (μm) and ρ is the density of the spherical silica powder (g / cm 3) For example, if the powder is amorphous silica, it is 2.21. D can be calculated using the formula D=Σ(ni·ai·di) / Σ(ni·ai). This means that in a single powder mass, there are n1, n2, ni, and nk particles with diameters d1, d2, ···di, and ··dk, in order of smallest particle diameter, and if the surface areas per particle are a1, a2, ···ai, and ··ak, respectively, D can be calculated using the formula D=(n1·a1·d1+n2·a2·d2+···+ni·ai·di+···+nk·ak·dk) / (n1·a1·+n2·a2+···+ni·ai+···+nk·ak).

[0030] It is preferable that the spherical silica powder does not substantially contain particles smaller than 50 nm, which can prevent an increase in viscosity when blended into a resin composition. "Substantially free of particles smaller than 50 nm" means that the number of particles smaller than 50 nm in 100 random photographs taken at a magnification of 50,000 times using an electron microscope is counted, and the average value per photograph is calculated to be less than 50. The fewer particles smaller than 50 nm, the better.

[0031] Electron micrographs can be taken using a field emission scanning electron microscope (JEOL model "FE-SEM, JSM-6301F") under conditions of an acceleration voltage of 15 kV and an irradiation current of 3 x 10-11 A. As a pretreatment for the photographs, carbon is vapor-deposited onto spherical silica powder for 2 seconds using a vacuum vapor deposition device (JEOL model "JEE-4X"), and then gold-palladium is vapor-deposited for 60 seconds.

[0032] As for the degree of "sphericity" of the spherical silica powder, for example, it is preferable that the average sphericity of particles having a particle diameter less than 75% (d75) of the cumulative particle size distribution is 0.90 or more, and the average sphericity of particles having a particle diameter of d75 or more is 0.85 or more. In general, increasing the average sphericity of the spherical silica powder tends to improve the flowability, but the effect of this embodiment can be further enhanced by setting the average sphericity of the coarse particles having a particle diameter of d75 or more to 0.85 or more.

[0033] The average sphericity can be measured by taking particle images taken with a stereomicroscope (for example, Nikon Model "SMZ-10"), a scanning electron microscope, or the like, and inputting them into an image analyzer (for example, Nippon Avionics), as follows: The projected area (A) and perimeter (PM) of the particle are measured from the photograph. If the area of ​​a perfect circle corresponding to the perimeter (PM) is (B), the particle's circularity can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter as the perimeter (PM) of the sample particle, PM = 2πr, B = πr 2 Therefore, B=π×(PM / 2π) 2 The sphericity of each particle is: Sphericity = A / B = A × 4π / (PM) 2 The circularity of 200 randomly selected particles thus obtained is determined, and the average value thereof can be taken as the average sphericity.

[0034] In addition, as a method for measuring circularity other than the above, the circularity of each particle is automatically and quantitatively measured using a particle image analyzer (for example, the Sysmex model "FPIA-1000"), and the circularity is calculated using the formula: circularity = (circularity) 2 It can also be calculated by converting it as follows:

[0035] A resin composition containing the spherical silica powder of the present invention can be suitably used as a resin molding material.

[0036] Next, the resin composition of this embodiment will be described.

[0037] The resin composition contains, in addition to the spherical silica powder of the present invention, a resin and known resin additives.

[0038] The resin composition may contain spherical silica powder alone or in combination with other fillers. The resin composition may contain 10 to 99% by mass of spherical silica powder, or 10 to 99% by mass of a mixed inorganic powder containing spherical silica powder and other fillers. The content of the other fillers in the mixed inorganic powder may be, for example, 1 to 20% by mass or 3 to 15% by mass relative to 100% by mass of the spherical silica powder. In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0039] Examples of other fillers include alumina, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, etc. The average particle size of the other fillers is about 5 to 100 μm, and there are no particular restrictions on the particle size structure and shape.

[0040] Examples of the resin include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, etc. These may be used alone or in combination of two or more.

[0041] The resin composition can be produced, for example, by blending raw material components in a predetermined ratio using a blender, a Henschel mixer, or the like, kneading the mixture using a heated roll, a kneader, a single-screw or twin-screw extruder, or the like, cooling the mixture, and then pulverizing it.

[0042] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0043] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0044] <Production of spherical silica powder> A burner 1 was installed above a melting furnace 2, and a collection line consisting of cyclones 4 and 6 and a bag filter 8 was directly connected below the burner 1. The thermal spraying apparatus 100 shown in FIG. 1 was used to produce spherical silica powder. Burner 1 has a double-pipe structure capable of forming an inner flame and an outer flame, and is installed at the top of melting furnace 2, to which combustible gas supply pipe 11, combustion supporting gas supply pipe 12, and raw material supply pipe 13 are connected. In the melting furnace 2, siliceous raw material powder is fed into a high-temperature flame through a raw material supply pipe 13 and melted to form molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by a blower 9 together with the combustion exhaust gas, move by the air through pipes 3, 5, and 7, and are classified and collected in cyclones 4 and 6 or a bag filter 8.

[0045] Example 1 Using the above-mentioned thermal spraying device 100, LPG was supplied as a combustible gas from the combustible gas supply pipe 11, and air or oxygen was supplied as a combustion supporting gas from the combustion supporting gas supply pipe 12, and a high-temperature flame was formed in the burner 1 by combustion of the LPG and oxygen. Secondary air was supplied to cyclone 4 (first cyclone) through a rotary valve (not shown) installed in pipe 3. Air from the atmosphere was used as the secondary air. The opening and closing degrees (lower opening degrees) of the lower valves in cyclone 4 and cyclone 6 (second cyclone) were set to 100%. Secondary air was also supplied from pipe 7 in the same manner. Natural silica stone was pulverized to an average particle size (D 50 The molten spherical particles collected in cyclones 4 and 6 and bag filter 8 were recovered as spherical silica powder. In this way, the flame formation conditions, raw material particle size, raw material supply amount, classification conditions, mixing conditions, etc. were adjusted to produce 13 types of powder as shown in Table 1. The median diameter was adjusted by adjusting the raw material particle size, multistage sieving of the powder after spheroidization treatment, and adjusting the mixing amounts of coarse particles, medium particles, fine particles, ultrafine particles, etc. obtained by the above-mentioned operations.

[0046] Examples 2 to 12 When the secondary air supply rate V (kg / h) was that of Example 1, in Example 2 it was 1.3 times that amount, 1.3V, in Example 3 it was 0.6 times that amount, 0.6V, in Example 4 it was 1.1 times that amount, 1.1V, in Example 5 it was 0.9 times that amount, 0.9V, in Example 6 it was 0.7 times that amount, 0.7V, and in Examples 7 to 12 it was 1 time that amount, 1V. Spherical silica powder was obtained in the same manner as in Example 1 above, except for adjusting the particle size.

[0047] (Comparative Example 1) When the secondary air supply amount V (kg / h) is the same as in Example 1, tree, Three times the amount 3 A spherical silica powder was obtained in the same manner as in Example 7, except that a large amount of secondary air was supplied to adjust the particle size so that V was obtained.

[0048] [Table 1]

[0049] <Content:NO2 - , NO3 - , SO3 2-, SO4 2- > 10 g of the obtained spherical silica powder and 70 g of distilled water were placed in a polyethylene container and shaken for 1 minute, then placed in a dryer and left to stand at 95°C for 20 hours before cooling. Water was added to compensate for the evaporation, and the volume was adjusted to a fixed amount. The mixture was then centrifuged, and the supernatant was used as the extract. The NO2 in the extract - , NO3 - , SO3 2- , and SO4 2- The concentrations of NO2 contained in the spherical silica powder were measured by ion chromatography. - Content of NO3 - Content of SO3 2- and SO4 2- The results of the examples are shown in Table 1.

[0050] <Particle size distribution> The volume frequency particle size distribution of the obtained spherical silica powder was determined by a wet laser diffraction scattering method using a particle size distribution analyzer (Beckman Coulter, LS-13-230). Water was used as the solvent, and the powder was pre-dispersed for 1 minute using a homogenizer at 200 W output before measurement. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% before measurement. Based on the obtained volume frequency particle size distribution, the particle diameter D at which the cumulative value becomes X% X was calculated.

[0051] <Production stability of resin composition> To 90% by mass of the obtained spherical silica powder, 4.2% by mass of 4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl type epoxy resin, 4.3% by mass of phenol resin, 0.2% by mass of triphenylphosphine, 0.5% by mass of γ-glycidoxypropyltrimethoxysilane, 0.3% by mass of carbon black, and 0.5% by mass of carnauba wax were added, and the mixture was dry-blended in a Henschel mixer. The resulting mixture was then heated and kneaded in a twin-screw extrusion kneader (heater temperature 105 to 110°C), and the resulting mixture was cooled in a cooling press and pulverized to obtain a resin composition. It was confirmed that the resin compositions using the spherical silica powder of Examples 1 to 12 had no curing defects and could be used without any practical problems (good). On the other hand, it was confirmed that the resin composition using the spherical silica powder of Comparative Example 1 had curing defects (poor).

[0052] Compared with Comparative Example 1, the spherical silica powders of Examples 1 to 12 showed results that could improve the production stability of the resin composition.

[0053] This application claims priority based on Japanese Patent Application No. 2022-018506, filed February 9, 2022, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0054] 1 burner 2. Melting furnace 3 Piping 4. Cyclone 5 Piping 6. Cyclone 7 Piping 8. Bag filter 9 Blower 11 Combustible gas supply pipe 12 Combustion auxiliary gas supply pipe 13 Raw material supply pipe 100 Thermal spraying equipment

Claims

1. NO determined based on the following ion chromatography method ３ － A spherical silica powder having a content of 0.01 ppm or more and 5 ppm or less, The NO contained in the spherical silica powder determined based on the ion chromatography method ２ － The content of N2, NO ３ － When the content of N2 is N3, N2 and N3 satisfy the relationship 0.05≦N3 / N2≦30. (Ion Chromatography) The spherical silica powder is placed in distilled water, heated and cooled, and then centrifuged to obtain a supernatant liquid, which is used as an extract. ２ － concentration, and NO ３ － The concentration is determined by ion chromatography. ２ － Concentration, NO ３ － Based on the concentration, the NO contained in the spherical silica powder ２ － Content of NO ３ － The content is calculated.

2. The spherical silica powder according to claim 1, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 10% is defined as D １０ The particle diameter at which the cumulative value reaches 50% is D ５０ The particle diameter at which the cumulative value reaches 97% is D ９７ When (D ９７ -D １０ ) / D ５０ is 1.0 or more and 10.0 or less.

3. The spherical silica powder according to claim 1, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 50% is defined as D ５０ The particle diameter at which the cumulative value reaches 97% is D ９７ When D ９７ / D ５０ is 2.0 or more and 30.0 or less.

4. The spherical silica powder according to claim 1, A spherical silica powder having an amorphous rate of 95% or more.

5. The spherical silica powder according to claim 1, The SO content of the spherical silica powder is determined in the same manner as in the ion chromatography method. ３ ２－ and SO ４ ２－ The spherical silica powder has a content of each of the above in an amount of 10 ppm or less.

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