Surface-treated silica powder, method for producing surface-treated silica powder

Abstract

This invention provides a surface-treated silica powder that excels at suppressing fluctuations in dielectric loss tangent before and after storage in high-temperature and high-humidity environments. [Solution] The surface-treated silica powder of the present invention contains silica particles surface-treated with vinylsilane, and the carbon content measured according to a predetermined procedure is defined as C (mass%), and the specific surface area measured by the BET 1-point method by nitrogen gas adsorption is defined as S (m²). 2 When ( / g) is set, C and S satisfy 0.001 ≤ C / S ≤ 0.025, and S is 0.8m 2 / g or more 5.0m 2 It must satisfy the condition of being less than or equal to / g.

Description

[Technical Field]

[0001] This invention relates to surface-treated silica powder and a method for producing surface-treated silica powder. [Background technology]

[0002] In recent years, with the increase in the volume of information and communication in the telecommunications field, the use of high-frequency bands in electronic devices and communication equipment has been expanding. High frequencies have characteristics such as broad bandwidth, directivity, and transparency, and in particular, frequencies of 10 9 The use of the GHz band, as described above, is widespread.

[0003] With the application of high-frequency bands, a problem arises in which the transmission loss of circuit signals increases. Transmission loss can be broadly classified into conductor loss due to the skin effect of wiring and dielectric loss due to the properties of the dielectric material of the insulator constituting electrical and electronic components such as substrates. Since dielectric loss is proportional to the first power of frequency, the square root of the dielectric constant of the insulator, and the first power of the dielectric loss tangent, materials used in high-frequency band devices are required to have low dielectric constant and dielectric loss tangent.

[0004] Silica (SiO2) has a low dielectric constant (3.7) and a quality factor index Qf (the product of the reciprocal of the dielectric loss tangent and the measurement frequency) of approximately 120,000, making it a promising filler material with low dielectric constant and dielectric loss tangent. However, the surface of silica particles contains many polar functional groups such as adsorbed water and silanol groups, which presents a problem in that the dielectric loss tangent is worse than that of a sintered substrate.

[0005] In contrast, Non-Patent Document 1 investigates a method of surface treatment using a silane coupling agent to reduce adsorbed water and polar functional groups on the surface of filler particles. However, the dielectric loss tangent is hardly reduced in the 1-10 MHz range, and the effect is insufficient. The effect in the GHz range is not specified. [Prior art documents] [Non-patent literature]

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, as a result of investigations by the present inventors, it has been found that there is room for improvement in the suppression of fluctuations in the dielectric tangent of silica powder as described in Non-Patent Document 1 before and after storage in a high-temperature and high-humidity environment.

Means for Solving the Problems

[0008] As a result of further investigations by the present inventors, it has been found that in silica powder having a predetermined specific surface area, by subjecting it to vinyl silane treatment, the carbon content on the powder surface can be reduced compared to methacryl silane. Based on such findings, as a result of intensive investigations, it has been found that by setting the carbon content per unit area to a predetermined value or less, fluctuations in the dielectric tangent of the surface-treated silica powder before and after storage in a high-temperature and high-humidity environment can be suppressed.

[0009] According to one aspect of the present invention, the following surface-treated silica powder and method for producing the surface-treated silica powder are provided. 1. A surface-treated silica powder containing silica particles surface-treated with vinyl silane, where the carbon content measured according to the following procedure is C (mass %), and the specific surface area measured by the BET single-point method by nitrogen gas adsorption is S (m 2 / g), when C and S satisfy 0.001 ≦ C / S ≦ 0.025 and S satisfies 0.8 m 2 / g or more and 5.0 m 2 / g or less, the surface-treated silica powder. (Procedure) Add 3 g of the surface-treated silica powder to 37 g of acetone and stir for 30 minutes. Then, operate the slurry in a centrifuge at 3500 rpm for 10 minutes to separate the surface-treated silica powder from the acetone, and discard the supernatant solution of acetone. Perform this washing operation with acetone twice and dry at 120 °C for 2 hours. Measure the carbon content (mass %) in 0.3 g of the washed surface-treated silica powder using a carbon / sulfur simultaneous analyzer and quantify it by the calibration curve method. 2. The surface-treated silica powder according to 1., When the particle diameters of the points where the cumulative volume from the small particle side in the volume-based cumulative distribution measured by the wet laser diffraction scattering method are 10%, 50%, and 90% are D 10 、D 50 、D 90 respectively, a surface-treated silica powder in which (D 90 -D 10 ) / D 50 is 1.0 or more and 5.0 or less. 3. The surface-treated silica powder according to 1. or 2., When the particle diameters of the points where the cumulative volume from the small particle side in the volume-based cumulative distribution measured by the wet laser diffraction scattering method are 10% and 50% are D 10 、D 50 respectively, a surface-treated silica powder in which D 50 / D 10 is 1.5 or more and less than 10.0. 4. The surface-treated silica powder according to any one of 1. to 3., A surface-treated silica powder having an average sphericity of 0.80 or more. 5. A method for producing a surface-treated silica powder, comprising a step of heat-treating a silica powder having a specific surface area measured by the BET one-point method by nitrogen gas adsorption of 0.8 m 2 / g or more and 5.0 m 2 / g or less under conditions of 1000 (°C·h) or more and 26400 (°C·h) or less, and then surface-treating with vinyl silane.

Advantages of the Invention

[0010] According to the present invention, a surface-treated silica powder that is excellent at suppressing fluctuations in dielectric loss tangent before and after storage in a high-temperature and high-humidity environment, a packaging body using the same, and a storage method are provided. [Modes for carrying out the invention]

[0011] The outline of the surface-treated silica powder of this embodiment will be described.

[0012] The surface-treated silica powder of this embodiment is A surface-treated silica powder containing silica particles surface-treated with vinylsilane, Let C (mass%) be the carbon content measured according to the procedure below, and S (m²) be the specific surface area measured by the BET one-point method using nitrogen gas adsorption. 2 When we set it to / g, C and S satisfy 0.001 ≤ C / S ≤ 0.025, and S is 0.8m 2 / g or more 5.0m 2 satisfies the condition of being less than or equal to / g Surface-treated silica powder. (procedure) Add 3 g of the surface-treated silica powder to 37 g of acetone and stir for 30 minutes. Then, run the slurry in a centrifuge at 3500 rpm for 10 minutes to separate the surface-treated silica powder from the acetone, and discard the supernatant solution of acetone. Repeat this washing operation with acetone twice and dry at 120°C for 2 hours. The carbon content (mass%) in 0.3 g of the washed surface-treated silica powder is measured using a carbon / sulfur simultaneous analyzer and quantified using the calibration curve method.

[0013] According to the inventors' findings, it has been found that by keeping the carbon content per unit area (C / S) below the above upper limit, it is possible to realize a surface-treated silica powder that can suppress large fluctuations in the dielectric loss tangent between before and after storage in high-temperature and high-humidity environments. Furthermore, it is possible to realize a surface-treated silica powder with a low dielectric loss tangent immediately after manufacturing.

[0014] By using a nonpolar silane coupling agent that does not contain O and / or N in its functional groups, and by keeping the C / S ratio below the above upper limit, it is possible to realize a surface-treated silica powder with minimal change in dielectric loss tangent over time before and after storage. For example, this can be achieved by applying treatment agents such as vinyltrimethoxysilane or dimethyldimethoxysilane, which do not contain O or N and have a low number of carbon atoms, or by drastically reducing the amount of phenyltrimethoxysilane or decyltrimethoxysilane added, which do not contain O or N and have a high number of carbon atoms.

[0015] The lower limit of C / S is, for example, 0.001 or higher, preferably 0.005 or higher, and more preferably 0.010 or higher. This improves adhesion with the resin. The upper limit of C / S is, for example, 0.025 or less, preferably 0.015 or less, and more preferably 0.010 or less. Keeping it below this upper limit suppresses fluctuations in dielectric loss tangent before and after storage in high-temperature, high-humidity environments, for example, at 40°C and 90% RH.

[0016] In this embodiment, the specific surface area, carbon content, and particle size distribution can be controlled by appropriately selecting, for example, the method for preparing the raw silica powder and the method for surface treatment of the raw silica powder. Among these, for example, appropriately adjusting the specific surface area by classifying the raw silica powder, and performing surface treatment with vinylsilane after classification and heat treatment are examples of factors that can bring the specific surface area, carbon content, and particle size distribution into desired numerical ranges.

[0017] The silica powder of this embodiment can be suitably used as a filler for compounding into resin materials such as resins or resin compositions. This resin material can be applied to a variety of uses, but for example, it can be used as a resin material for high-frequency band applications.

[0018] The composition of the surface-treated silica powder of this embodiment will be described in detail below.

[0019] Surface-treated silica powder can be any powder that contains silica (SiO2) as its main component. The term "main component" means that, by mass, the total amount of surface-treated silica powder contains, for example, 50% or more, preferably 80% or more, and more preferably 90% or more, of silica (SiO2). While higher purity silica is preferable, the presence of impurities that inevitably occur during the raw material and manufacturing process is acceptable.

[0020] The surface-treated silica powder contains either amorphous or crystalline silica, or both. The amorphous content of the surface-treated silica powder is, for example, 95.0% or more, preferably 97.0% or more, and more preferably 99.0% or more.

[0021] The amorphous content of surface-treated silica powder is determined by performing X-ray diffraction analysis using a powder X-ray diffractometer (e.g., RIGAKU's "Model MiniFlex") in the range of CuKα 2θ from 26° to 27.5°, and measuring it from the intensity ratio of specific diffraction peaks. In the case of siliceous powder, crystalline silica (α-quartz) has a main peak at 26.7°, but amorphous silica does not have a peak. When amorphous and crystalline silica are mixed, a peak height of 26.7° is obtained that corresponds to the proportion of crystalline silica. Then, the crystalline silica content ratio (X-ray diffraction intensity of the sample / X-ray diffraction intensity of crystalline silica) can be calculated from the ratio of the X-ray intensity of the sample to the X-ray intensity of the crystalline silica standard sample, and the amorphous content ratio (%) can be calculated from the formula: amorphous content ratio (%) = (1 - crystalline silica content ratio) × 100. If crystalline phases other than α-quartz are present, the same calculation should be performed for the main peak of each crystalline phase.

[0022] The silica particles in the surface-treated silica powder may be spherical, crushed, needle-shaped, or flake-shaped, but spherical is preferred.

[0023] The average circularity of the surface-treated silica powder is, for example, 0.80 or higher, preferably 0.90 or higher, and more preferably 0.95 or higher. This suppresses an increase in viscosity and a decrease in fluidity of the resulting resin composition when mixed with the resin.

[0024] The average sphericity of surface-treated silica powder is measured as follows: Particle images captured using a stereomicroscope (for example, Nikon's "SMZ-10" model), scanning electron microscope, etc., are imported into an image analysis device (for example, one manufactured by Japan Avionics Co., Ltd.). The projected area (A) and perimeter (PM) of the particles are measured from the photograph. If (B) is the area of ​​a perfect circle corresponding to the perimeter (PM), then the roundness of the particle can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter (PM) as the sample particle, PM = 2πr and B = πr 2 Therefore, B = π × (PM / 2π) 2 Therefore, the sphericity of each particle is given by: Sphericity = A / B = A × 4π / (PM) 2 It can be calculated as follows. The roundness of 200 arbitrary particles obtained in this way was determined, and the average value was taken as the average sphericity.

[0025] The vinylsilanes used for surface treatment of silica particles are silanes having at least one vinyl group in their molecule. These may be included individually or in any combination of two or more.

[0026] The silanes described above have one or more hydrolyzable groups in their molecules, in addition to functional groups such as vinyl groups. Examples of hydrolyzable groups include alkoxy groups such as methoxy groups and ethoxy groups. The alkoxy group generates a silanol group through hydrolysis. This silanol group chemically reacts with the OH group (reaction site) present on the surface of the silica particle, causing the silane coupling agent to chemically bond to the surface of the silica particle.

[0027] Silanes having a vinyl group can be any low-polarity silane that does not contain O and / or N in the vinyl group or other functional groups. Specifically, examples include vinyltrimethoxysilane, 7-octenyltrimethoxysilane, and vinyltriethoxysilane.

[0028] The upper limit of the specific surface area (S) of surface-treated silica powder is 5.0 m². 2 Less than or equal to / g, preferably 4.5m 2 / g or less, more preferably 4.0m 2 It is less than / g. This allows for a further reduction in the dielectric loss tangent when compounded into resin. On the other hand, the lower limit of the specific surface area (S) is 0.8 m². 2 / g or more, preferably 1.0m 2 / g or more, more preferably 1.4m 2 The concentration is 1 / g or more. This improves the filler properties of the composition when it is incorporated into the resin.

[0029] The specific surface area of ​​silica powder can be measured by the BET single-point method using nitrogen gas adsorption. Specifically, using a specific surface area analyzer (Anton Paar, model name: NOVA 800 BET), nitrogen gas is transported as the adsorption gas by a vacuum pump, and 0.1 to 5.0 g of the sample is dried and degassed at 300°C for 30 minutes before measurement.

[0030] In the volume-based cumulative distribution of particle size in surface-treated silica powder, the particle size at each point where the cumulative volume from the smallest particle side reaches 10%, 50%, and 90% is D. 10 , D 50 , D 90 Let's assume that. The volume-based cumulative distribution of surface-treated silica powder is a value based on particle size measurement by wet laser diffraction scattering. For example, the particle size distribution analyzer can be a Coulter LS13 320. For measurement, water is used as the solvent, and as a pretreatment, dispersion treatment can be performed using a homogenizer at a power of 500W for 120 seconds or more. Furthermore, the PIDS (Polarization Intensity Differential Scattering) concentration should be adjusted to 45-55%. The refractive index of water is set to 1.33, and the refractive index of the powder material should be considered. For example, amorphous silica is measured with a refractive index of 1.50.

[0031] (D 90 -D10 ) / D 50 The lower limit is, for example, 1.0 or higher, preferably 1.4 or higher, and more preferably 1.8 or higher. This improves the filler properties of the composition when it is compounded with resin. (D 90 -D 10 ) / D 50 The upper limit is, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.0 or less. Keeping it below the upper limit improves moldability by reducing coarse particles.

[0032] D 50 / D 10 The lower limit is, for example, 1.5 or higher, preferably 2.0 or higher, and more preferably 2.5 or higher. This further improves the fillability of the composition when it is compounded with resin. D 50 / D 10 The upper limit is, for example, 10.0 or less, preferably 9.0 or less, and more preferably 8.0 or less. By keeping it below the upper limit, the dielectric loss tangent in the resin composition containing surface-treated silica powder can be reduced.

[0033] <Method for producing surface-treated silica powder> As an example of a method for producing surface-treated silica powder according to this embodiment, surface-treated silica powder can be obtained by classification, heat treatment, and surface treatment using vinylsilane. The specific manufacturing method involves, for example, measuring the specific surface area of ​​0.8 m² using the BET single-point method with nitrogen gas adsorption. 2 / g or more 5.0m 2 The process may include heating silica powder at a concentration of 1000°C·h or less under conditions of 1000°C·h or more and 26400°C·h or less, followed by surface treatment with the vinylsilane described above. In the above manufacturing method, one or more vinylsilanes may be used alone, and vinylsilane may be used in combination with other silanes or silazanes, to the extent that the effects of the present invention are not impaired. Here, the vinylsilane content in the silane coupling agent used in the surface treatment is, for example, 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. Furthermore, by reducing the silazane (such as hexamethyldisilazane) content in the silane coupling agent used in surface treatment, the generation of ammonia (NH3) in the compounded resin can be suppressed, thereby reducing the impact on changes in resin properties such as curing behavior.

[0034] The following provides a detailed explanation of each step. First, the raw silica powder is produced by a dry process. An example of a dry process is the powder melting method, which involves passing the powder through a high-temperature range above its melting point to create spheroids. An example of a high-temperature range above the melting point is a flame. The flame temperature may be, for example, 1700°C. The raw silica powder produced by the dry process is subjected to a classification process including coarse powder classification and / or fine powder classification to obtain classified silica powder. It may be collected and stored in moisture-proof aluminum bags. Furthermore, classification can be carried out by mixing or classifying appropriate amounts of silica powder with different particle size configurations. Industrially, classification using a classifier such as a sieve or a precision air classifier is preferable, and the classification operation is preferably performed using a dry method. By dry classifying raw silica powder produced by a dry method, aggregation of the silica powder can be suppressed and handling properties can be improved compared to using raw silica powder produced by a wet method and / or wet classification.

[0035] Next, the classified silica powder is subjected to heat treatment. The heat treatment is performed at a temperature of 500 to 1100°C for a predetermined time (for example, about 1 to 52 hours) where the heating temperature (°C) × heating time (h) is 1000 to 26400 (°C·h), preferably for a predetermined time (for example, about 2 to 35 hours) where the heating temperature is 1800 to 17600 (°C·h). This treatment is carried out using hot air or an electric furnace. If the heating temperature is between 500 and 1100°C, the specific surface area and average particle size do not change before and after heating. Therefore, it is desirable to perform the classification process before heating, adjust the specific surface area and average particle size to the desired level, and then perform the heat treatment. After heat treatment, the silica powder may be recovered at a temperature of 110°C to 300°C after natural cooling in an electric furnace, further cooled to 25°C in an environment with a humidity of 40% RH or less, stored at 15 to 25°C, and then recovered and stored in a moisture-proof aluminum bag.

[0036] Next, the heat-treated silica powder is surface-treated with the silane coupling agent described above.

[0037] In the method for producing surface-treated silica powder, the treated material may be collected and stored in a bag after at least one of the following treatments: classification, heat treatment, and surface treatment.

[0038] In this embodiment, the treated material and / or surface-treated silica powder can be stored in a resin bag or a moisture-proof aluminum bag. Examples of plastic bags include, but are not limited to, PET film bags, PE film bags, and PP film bags. The moisture-proof aluminum bag has a moisture permeability of 0.1 g / m³ under JIS Z 0208-1976 condition B (temperature 40°C - relative humidity 90%). 2 Examples of moisture-proof bags (24 hours or less), such as moisture-proof aluminum bags or PET / AL / PE laminated bags.

[0039] The packaging of this embodiment may comprise the above-mentioned surface-treated silica powder and a resin bag containing the surface-treated silica powder. The resin bag may be sealed to contain the surface-treated silica powder, and the sealed space may be degassed or replaced with a known inert gas.

[0040] Furthermore, the storage method of this embodiment may include the step of storing the surface-treated silica powder in a resin bag. In terms of storage methods, the external environment during storage and the storage period are not particularly limited. Because the surface-treated silica powder of this embodiment exhibits little change in dielectric loss tangent over time, the dielectric loss tangent of the surface-treated silica powder can be kept low after storage even without using a moisture-proof bag.

[0041] Next, the resin composition of this embodiment will be described. The surface-treated silica powder of this embodiment, when incorporated into a resin composition, can be suitably used as a resin material. The resin composition includes, in addition to the surface-treated silica powder of this embodiment, a resin and known resin additives.

[0042] In the resin composition, the surface-treated silica powder may be used alone or mixed with other fillers. The resin composition may contain 10 to 99% by mass of surface-treated silica powder, or 10 to 99% by mass of mixed inorganic powder containing surface-treated silica powder and other fillers. In addition, the content of 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 silica powder. In this specification, unless otherwise specified, "~" indicates that it includes both the upper and lower limits.

[0043] Other fillers include, for example, silica other than the surface-treated silica powder of this embodiment, alumina, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, and the like. Other fillers used typically have an average particle size of around 5 to 100 μm, and there are no particular restrictions on their particle size composition or shape.

[0044] Examples of the above-mentioned resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, fully aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. These may be used individually or in combination of two or more types.

[0045] Resin compositions can be manufactured, for example, by blending raw material components in predetermined ratios using a blender or Henschel mixer, then kneading them using a heated roll, kneader, single-screw or twin-screw extruder, cooling, and then grinding the mixture.

[0046] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0047] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0048] <Preparation of silica powder> [Example 1] The raw material used was silica powder produced by a dry process. The silica powder had one peak with the most frequent diameter in the range of 1.0 to 15.0 μm. The fine and coarse powders were removed from the silica powder using cyclone collection and a precision air classifier. Through this classification process, silica powder with the particle size distribution and specific surface area shown in Table 1 was obtained. Next, the classified silica powder was packed into an alumina crucible and heat-treated in an electric furnace at 980°C under atmospheric conditions for 4 hours. After the heat treatment, it was cooled to 200°C in the furnace, then cooled to room temperature in a desiccator (23°C, 10% RH), and the heat-treated silica powder was recovered. To 100 parts by mass of heat-treated silica powder, 0.15 parts by mass of vinylsilane (KBM-1003, manufactured by Shin-Etsu Silicone Co., Ltd.) was added and mixed for 30 minutes in a vibrating mixer (manufactured by Resodyn Co., Ltd.). After that, the mixture was dried at 120°C for 4 hours. This surface treatment yielded surface-treated silica powder.

[0049] [Example 2] In the above surface treatment, a surface-treated silica powder was obtained in the same manner as in Example 1, except that 0.10 parts by mass of vinylsilane (KBM-1003, manufactured by Shin-Etsu Silicone Co., Ltd.) was added to 100 parts by mass of heat-treated silica powder. [Comparative Example 1] Silica powder that had not undergone surface treatment was recovered in the same manner as in Example 1, except that the above surface treatment was not performed.

[0050] [Comparative Example 2] In the above surface treatment, 0.2 parts by mass of methacrylic silane (KBM-503, manufactured by Shin-Etsu Silicone Co., Ltd.) was added to 100 parts by mass of heat-treated silica powder, except that surface-treated silica powder was obtained in the same manner as in Example 1.

[0051] [Reference example 1] The above-mentioned silica powder was added to pure water and stirred at room temperature for 6 hours to prepare a slurry with a particle concentration of 40% by mass. This slurry was put into a classifier and wet classification was performed. The classification conditions were a rotor peripheral speed of 26 m / s and a particle discharge rate of 10 L / hr. The supernatant liquid was removed from the slurry from which the fine particles had been removed by decantation, and the resulting silica powder was dried at 110°C for 24 hours. The dried silica powder was crushed in a mortar. The crushed silica powder was placed in an alumina crucible and heated in an electric furnace under a nitrogen atmosphere at an electric furnace temperature of 1000°C for 4 hours. After that, the furnace was allowed to cool naturally until it reached room temperature, and the silica powder was recovered. 1 part by mass of vinylsilane (KBM-1003, manufactured by Shin-Etsu Silicone Co., Ltd.) was added to 100 parts by mass of the recovered silica powder. Subsequently, the mixture was mixed in a vibrating mixer (manufactured by Resodyn) at an acceleration of 60G for 2 minutes, and then dried in a vacuum dryer for 24 hours at 120°C and below -133 Pa to obtain surface-treated silica powder.

[0052] The silica powder obtained as described above was stored in a plastic bag until immediately before each evaluation.

[0053] [Table 1]

[0054] The following items were evaluated for the obtained silica powder.

[0055] <Specific surface area> The specific surface area of ​​silica powder was measured using the BET 1-point method with nitrogen gas adsorption. Specifically, using a specific surface area analyzer (Anton Paar, model name: NOVA 800 BET), nitrogen gas was transported by a vacuum pump, and 0.1 to 5.0 g of the sample was dried and degassed at 300°C for 30 minutes before measurement.

[0056] <Particle size> The volume-based frequency distribution and volume-based cumulative distribution of silica powder particles were determined using a wet laser diffraction scattering method with a particle size distribution analyzer (Coulter LS13 320). Water was used as the solvent, and as a pretreatment, the powder was dispersed using a homogenizer at a power of 500W for 120 seconds or more before measurement. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% for measurement. A refractive index of 1.33 was used for water, and the refractive index of the powder material was considered. For example, amorphous silica was measured with a refractive index of 1.50. Based on the obtained volume-based cumulative distribution, the particle size (D) at which the cumulative value from the small particle size side becomes X% X ) was calculated.

[0057] <Average sphericity> The average sphericity of silica powder was measured by capturing particle images using a stereomicroscope (e.g., Nikon's SMZ-10 model) or scanning electron microscope, and then inputting the images into an image analysis device (e.g., one manufactured by Japan Avionics Co., Ltd.) as follows: The projected area (A) and perimeter (PM) of the particle were measured from the photograph. If (B) is the area of ​​a perfect circle corresponding to the perimeter (PM), then the roundness of the particle can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter (PM) as the sample particle, PM = 2πr and B = πr 2 Therefore, B = π × (PM / 2π) 2 Therefore, the sphericity of each particle is given by: Sphericity = A / B = A × 4π / (PM) 2 It can be calculated as follows. The roundness of 200 arbitrary particles obtained in this way was determined, and the average value was taken as the average sphericity. The average sphericity of the silica powders in Examples 1 and 2 was 0.90 or higher in both cases.

[0058] <Carbon content after acetone cleaning> 3 g of the obtained silica powder was added to 37 g of acetone and stirred for 30 minutes to obtain a slurry. The slurry was then centrifuged at 3500 rpm for 10 minutes to separate the silica powder from the acetone, and the supernatant solution of the acetone was discarded. This washing operation with acetone was repeated twice, and the mixture was dried at 120°C for 2 hours. The carbon content (mass%) in 0.3 g of washed silica powder was measured using a carbon / sulfur simultaneous analyzer "CS-444LS" (manufactured by LECO Corporation) and quantified using the calibration curve method.

[0059] <Viscosity> A resin sample was obtained by mixing 35% by mass of the obtained silica powder with 65% by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, bisphenol F type resin, JER807). The viscosity (Pa·s) of the obtained resin samples was measured at 25°C and a shear rate of 100 [1 / s] using a rheometer (Anton Paar, Model Modular Compact Rheometer MCR 102) equipped with a conical cone (3 degrees). The results are shown in Table 1. When the viscosity was less than 200 Pa·s, the filling performance was judged as "good"; when it was between 200 and 300 Pa·s, the filling performance was judged as "poor"; and when it exceeded 300 Pa·s, the filling performance was judged as "very poor".

[0060] <Dielectric loss tangent measured by resonance method> The obtained silica powder was mixed with polyethylene powder (Sumitomo Seika Co., Ltd., Flowsen UF-20S) at a packing volume of 40% using a vibrating mixer (Resodyn Co., Ltd.) under conditions of acceleration of 60g and processing time of 2 minutes. The obtained mixed powder was weighed to a predetermined volume (to a thickness of approximately 0.3 mm), placed in a 3 cm diameter metal frame, and molded using a nanoimprint meter (SCIVAX "X-300") under the conditions of 140°C-5 min-30000N to form a resin sheet sample with a diameter of 3.0 cm and a thickness of 0.3 mm. The shape and size of the resin sheet sample do not affect the evaluation results as long as it can be mounted on the measuring instrument. Using the obtained resin sheet samples, the dielectric constant and dielectric loss tangent were measured using a 40 GHz split-cylinder resonator (manufactured by EM Labs). The samples were placed in the resonator and measured. Measurements were performed twice under the same processing conditions, with n=2 for each sheet, and the average value of the four measurements was calculated. The measurement temperature was 20°C and the humidity was 60%RH. The obtained tanδc was used as the dielectric loss tangent of the resin sheet sample. Furthermore, the obtained silica powder was stored for 6 months under the following conditions: (temperature 40°C, humidity 90%RH, in a high-temperature, high-humidity chamber, in an atmospheric environment, with 20g of silica stored in a 12cm diameter glass petri dish). After that, a resin sheet sample was prepared in the same manner as described above, and the dielectric loss tangent of the resin sheet sample was measured. Table 1 shows the ratio of the dielectric loss tangent of a resin sheet using silica powder after 6 months of storage, with the dielectric loss tangent of the resin sheet using silica powder before storage being used as the reference.

[0061] The surface-treated silica powders of Examples 1 and 2 showed that, compared to Comparative Examples 1 and 2, they could suppress the increase in the degree of change in dielectric loss tangent when compounded with resin, both before and after storage in high-temperature and high-humidity environments. Furthermore, the surface-treated silica powders of Examples 1 and 2 showed superior filling performance compared to Reference Example 1, which had a smaller specific surface area.

Claims

1. A surface-treated silica powder containing silica particles surface-treated with vinylsilane, Let C (mass%) be the carbon content measured according to the procedure below, and S (m²) be the specific surface area measured by the BET one-point method using nitrogen gas adsorption. ２ When / g) C and S satisfy 0.001 ≤ C / S ≤ 0.025, and S is 0.8 m ２ / g or more 5.0m ２ Satisfying the condition of being less than or equal to / g Surface-treated silica powder. (procedure) Add 3 g of the surface-treated silica powder to 37 g of acetone and stir for 30 minutes. Then, run the slurry in a centrifuge at 3500 rpm for 10 minutes to separate the surface-treated silica powder from the acetone, and discard the supernatant solution of acetone. Repeat this acetone washing operation twice and dry at 120°C for 2 hours. The carbon content (mass%) in 0.3 g of the washed surface-treated silica powder is measured using a carbon / sulfur simultaneous analyzer and quantified using a calibration curve method.

2. The surface-treated silica powder according to claim 1, When the particle diameters of the points where the cumulative volume from the small particle side in the volume-based cumulative distribution measured by the wet laser diffraction scattering method are 10%, 50%, and 90% are D １０ , D ５０ , D ９０ , when it is set as (D ９０ - D １０ ) / D ５０ is 1.0 or more and 5.0 or less, a surface-treated silica powder.

3. A surface-treated silica powder according to claim 1 or 2, The particle diameters D are defined as the particle diameters at the points where the cumulative volume from the small particle side reaches 10% and 50% in the volume-based cumulative distribution measured by wet laser diffraction scattering. １０ , D ５０ In that case, D ５０ / D １０ Surface-treated silica powder having a value of 1.5 or more and 10.0 or less.

4. A surface-treated silica powder according to claim 1 or 2, Surface-treated silica powder with an average sphericity of 0.80 or higher.

5. The specific surface area measured by the BET one-point method using nitrogen gas adsorption is 0.8 m². ２ / g or more 5.0m ２ A method for producing surface-treated silica powder, comprising the step of heat-treating silica powder at a density of 1000°C·h or more and 26400°C·h or less, and then surface-treating it with vinylsilane.

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