WO2022210919A1

WO2022210919A1 - Powder, production method therefor, and resin composition production method

Info

Publication number: WO2022210919A1
Application number: PCT/JP2022/016128
Authority: WO
Inventors: 美紀江上; 正展谷口; 宏忠荒金; 良村口
Original assignee: 日揮触媒化成株式会社
Priority date: 2021-03-31
Filing date: 2022-03-30
Publication date: 2022-10-06
Also published as: JPWO2022210919A1; CN116867738A; KR20230161426A; TW202302744A

Abstract

The present invention relates to a powder including hollow particles, each having a cavity inside a non-porous outer shell. The powder has an average particle size (D50) of 2.0-10.0 μm, and contains microparticles of a particle size under 2.0 μm in the amount of 20 vol% or less. When the powder is suspended in water, the proportions of floating particles, suspended particles, and settled particles are 7.0-25.0 mass%, 0-4.0 mass%, and 71.0-93.0 mass%, respectively.

Description

Powder, method for producing the same, and method for producing resin composition

The present invention relates to powders suitable for fillers of insulating materials for semiconductors. In particular, it relates to powders comprising hollow particles having cavities inside non-porous shells.

In recent years, the speed and capacity of information communication have been increasing. Therefore, materials used in communication devices are required to have a low dielectric constant (low Dk) and a low dielectric loss tangent (low Df). For example, an insulating material having a low dielectric constant and a low dielectric loss tangent is required for printed wiring boards on which semiconductor elements are mounted. If the dielectric constant of the insulating material is high, dielectric loss will occur, and if the dielectric loss tangent of the insulating material is high, not only the dielectric loss but also the amount of heat generated may increase.

In order to achieve a low dielectric constant and a low dielectric loss tangent of insulating materials, resin materials, which are the main insulating materials, are being developed. Epoxy-based resins, polyphenylene ether-based resins, fluorine-based resins, and the like have been proposed as such resin materials (see Patent Documents 1 to 5, for example).

Fillers are added to such resin materials in terms of durability (rigidity) and heat resistance. It is known to use metal oxides such as silica, boron nitride, talc, kaolin, clay, mica, alumina, zirconia, and titania as fillers (see, for example, Patent Document 3).

WO2009/041137 Japanese Patent Publication No. 2006-516297 JP 2017-057352 A Japanese Patent Application Laid-Open No. 2001-288227 JP 2019-172962 A

Among the materials used as fillers, silica is superior in terms of low dielectric constant and low dielectric loss tangent. However, as the capacity and speed of data communication are rapidly increasing, further reductions in dielectric constant and dielectric loss tangent are required.

The inventors have found that hollow particles that do not contain microparticles and satisfy predetermined conditions can achieve a low dielectric constant and a low dielectric loss tangent of insulating materials.

That is, the powder according to the present invention contains hollow particles having a cavity inside a nonporous outer shell, has an average particle size (D50) of 2.0 to 10.0 μm, and has a particle size of 2.0 μm. less than 20% by volume of microparticles. When this powder is suspended in water, the suspended particles are 7.0 to 25.0% by mass, the suspended particles are 0 to 4.0% by mass, and the sedimented particles are 71.0 to 93.0% by mass. .

Further, the method for producing a powder according to the present invention includes a first step of preparing particles by spray-drying an aqueous alkali silicate solution in a hot air stream, a second step of removing alkali contained in the particles, and a second step of removing alkali. and a third step of firing the particles, and a classification step of removing fine particles of less than 2.0 μm is provided between the first and third steps.

The powder of the present invention makes it possible to reduce the dielectric constant and dielectric loss tangent of the insulating material, thereby increasing the transmission speed of semiconductors and reducing transmission loss.

The powder of the present invention contains hollow particles having cavities inside nonporous outer shells, and has an average particle size of 2.0 to 10.0 μm. Furthermore, the content of microparticles having a particle diameter of less than 2.0 μm is 20% by volume or less. When this powder is suspended in water, the suspended particles are 7.0 to 25.0% by mass, the suspended particles are 0 to 4.0% by mass, and the sedimented particles are 71.0 to 93.0% by mass. be. In addition to hollow particles, the powders of the present invention may also contain small amounts of solid particles. This is because there is a possibility that solid particles are also produced unexpectedly during the production of hollow particles. Since solid particles without internal cavities have a high specific gravity, they are basically thought to be latent in sedimented particles. It is preferable that 90 mass % or more of the particles contained in the powder are hollow particles.

Here, particles that disperse in water when suspended in water are defined as suspended particles, and particles with a low specific gravity floating in the upper layer (near the water surface) are defined as suspended particles. Such suspended particles usually have a high porosity. Therefore, the dielectric constant and dielectric loss tangent of the resin product decrease as the number of suspended particles mixed in the resin material increases. In general, particles with higher porosity have larger particle diameters (smaller particle diameters have lower porosity). Therefore, controlling the amount of suspended particles to 7.0 to 25.0% by mass of the total particles controls (reduces) the amount of coarse particles. Since there are not many coarse particles, the resin composition for molding resin products (insulating materials, etc.) has good filterability and injectability. Therefore, the surface smoothness of the molded resin product is improved. Since microparticles have a low porosity, by reducing the content of particles (microparticles) with a particle diameter of less than 2.0 μm, the dielectric constant can be lowered without increasing the number of large particles with a high porosity. Fewer microparticles also reduce the total surface area of all particles. As a result, the amount of SiOH groups is reduced, so that the dielectric constant and dielectric loss tangent can be lowered.

Thus, by using the powder of the present invention as a filler, the filterability and injectability of the resin composition for molding are improved, and a resin product with good surface smoothness can be obtained. In addition, a powder containing few microparticles has low adhesiveness and improved fluidity. Therefore, handleability and dispersibility are also improved.

The content of microparticles is preferably 15% by volume or less, more preferably 10% by volume or less, even more preferably 5% by volume or less, and most preferably 3% by volume or less.

Suspended particles tend to have low particle strength because the ratio (t/d) of the particle diameter (d) to the shell thickness (t) is small. Therefore, there is a risk that the particles will break during the process of mixing the resin material and the particles until the resin product is molded (that is, during the manufacturing process). Cracked particles hinder low dielectric constant and low dielectric loss tangent, and deteriorate the fluidity of the resin composition, reduce the uniformity of the resin product (molded product), It becomes a factor that causes voids. However, by controlling the amount of suspended particles, cracking of the particles can be suppressed.

In addition, by controlling the amount of suspended particles, while ensuring the favorable properties of particles with high porosity (e.g., low dielectric constant and low dielectric loss tangent), unfavorable properties of high porosity particles (e.g., occurrence of cracks) can be suppressed to the extent that there is no problem. Among the suspended particles, there are particles with a high porosity even if they have a small diameter. Such particles are less likely to crack than large-diameter particles in the manufacturing process. characteristics can be suppressed as much as possible.

The content of suspended particles is preferably 8.0 to 24.0% by mass, more preferably 8.0 to 23.0% by mass, even more preferably 8.0 to 22.0% by mass, and 8.0 to 15.0% by weight is most preferred. The content of the sedimented particles is preferably 72.0 to 92.0% by mass, more preferably 73.0 to 92.0% by mass, even more preferably 74.0 to 92.0% by mass, and 81.0% by mass. ~92.0% by weight is most preferred.

Also, the average particle size (D50) of the powder is in the range of 2.0 to 10.0 μm. If the average particle diameter is less than 2.0 μm, a large number of fine particles are contained, resulting in a high specific surface area (high SiOH group content), making it difficult to obtain excellent dielectric properties. Also, powders with an average particle size exceeding 10 μm are unsuitable for use in semiconductors. For semiconductor applications, the average particle size is preferably 2.5 to 10.0 μm, more preferably 3.0 to 10.0 μm.

Also, the maximum particle diameter (D100) is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The maximum particle size (D100) is preferably 10 times or less, more preferably 8 times or less, the average particle size (D50). Usually, it is 2 times or more, and may exceed 5 times as long as the requirements of the present invention are satisfied.

The porosity of the powder is preferably 20% by volume or more, more preferably 30% by volume or more, and even more preferably 40% by volume or more. Also, it is preferably 70% by volume or less, more preferably 65% by volume or less, even more preferably 60% by volume or less, and most preferably 55% by volume or less. With such a porosity, it is possible to achieve a low dielectric constant and a low dielectric loss tangent, and at the same time, it is possible to effectively suppress cracking of the particles by maintaining the particle strength above a predetermined level.

Here, silica-based particles containing silica as a main component are suitable for the particles that make up the powder. Therefore, the hollow particles (outer shell) contained in the powder may contain inorganic oxides such as alumina, zirconia, and titania in addition to silica. The content of silica in the particles is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably consisting essentially of silica.

[Resin composition]
A resin composition is prepared by blending the powder and the resin material described above. Such a resin composition is an insulating material for electronic materials such as semiconductors, and more specifically, copper-clad laminates, prepregs, build-up films, etc. for forming printed wiring boards (including rigid boards and flexible boards). can be used for It can also be used for semiconductor package-related materials such as mold resins, mold underfills, and underfills, adhesives for flexible substrates, and the like.

As the resin, curable resins that are generally used in electronic materials such as semiconductors can be used. A photocurable resin may be used, but a thermosetting resin is preferred. Examples of curable resins include epoxy-based resins, polyphenylene ether-based resins, fluorine-based resins, polyimide-based resins, bismaleimide-based resins, acrylic-based resins, methacrylic-based resins, silicone-based resins, BT resins, and cyanate-based resins. can. Furthermore, as epoxy resins, bisphenol-type epoxy resins, novolak-type epoxy resins, triphenolalkane-type epoxy resins, epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, dicyclopentadiene phenol novolak resins, and phenol aralkyl-type epoxy resins. , glycidyl ester type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and halogenated epoxy resins. These resins may be used alone or in combination of two or more.

The resin composition preferably contains the powder A and the curable resin B at a mass ratio (A/B) of 10/100 to 95/100. Thereby, the function as a filler can be sufficiently exhibited while maintaining the characteristics of the resin composition such as fluidity. The mass ratio (A/B) is more preferably 30/100 to 80/100.

Furthermore, the resin composition preferably contains a curing agent such as a phenol compound, an amine compound, or an acid anhydride. When an epoxy resin is used as the curable resin, a resin having two or more phenolic hydroxyl groups in one molecule (bisphenol type resin, novolak resin, triphenol alkane type resin, resol type phenol resin, phenol aralkyl resin, phenolic resins such as biphenyl-type phenolic resins, naphthalene-type phenolic resins, and cyclopentadiene-type phenolic resins), and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methylnadic anhydride. Various additives (colorants, stress relaxation agents, antifoaming agents, leveling agents, coupling agents, flame retardants, curing accelerators, etc.) may be added to the resin composition as necessary.

Conventionally known methods can be applied to the method of manufacturing the resin composition. For example, a curable resin, powder, a curing agent, additives, etc. are mixed and kneaded by a roll mill or the like. The obtained resin composition is applied to a substrate and cured by heat, ultraviolet rays, or the like.

[Method for producing powder]
The method for producing a powder of the present invention includes a first step of spray-drying an aqueous alkali silicate solution in a hot air stream to prepare particles, a second step of removing the alkali contained in the prepared particles, and a second step of removing the alkali. and a third step of firing the particles, and a step of classifying the particles to remove fine particles of less than 2.0 μm (classifying step) is provided between the first step and the third step. In addition, other processes such as a drying process may be provided between each process. Through such a process, the powder described above can be obtained.

Generally, when producing particles by sintering, it is considered preferable to perform a classification treatment after sintering in order to adjust the particle size. However, in this case, the classification treatment is intentionally performed before firing. If the sintering process is performed without classifying, the particles are sintered while the fine particles to be removed are present, and the fine particles are sintered with other particles. Therefore, the fine particles cannot be removed even if the classification treatment is performed afterward. Fine particles can be reliably reduced by performing the classification treatment before firing. As a result, a low dielectric constant and a low dielectric loss tangent of the particles can be achieved more reliably, and particles suitable for high-speed data communication can be obtained. In addition, you may perform a classification process again after baking. Each step will be described in detail below.

(First step)
In this step, the alkali silicate aqueous solution is spray-dried in a hot air stream to granulate silica-based particles. Although this step is performed to obtain hollow particles, it is difficult to make all the particles hollow particles, and the granulated silica-based particles eventually contain solid particles. There may be In this case, solid particles are also contained in the powder obtained through the steps described below. However, if the powder has the properties described above, the expected effect can be obtained even if the powder contains solid particles.

The molar ratio (SiO ₂ /M ₂ O) of SiO ₂ and M ₂ O (M is an alkali metal) in the alkali silicate is preferably 1-5, more preferably 2-4. If this molar ratio is less than 1, the amount of alkali is too large, and it is difficult to sufficiently remove it even if acid washing is carried out in the alkali removing step. Furthermore, the deliquescence of the spray-dried product increases, making it difficult to obtain desired hollow particles. If this molar ratio exceeds 5, the alkali silicate becomes less soluble, making it difficult to prepare an aqueous solution. Even if an aqueous solution can be prepared, it may not be possible to form hollow particles by spray drying.

The concentration of SiO ₂ in the alkali silicate aqueous solution is preferably 1 to 30% by mass, more preferably 5 to 28% by mass. Production is possible even if the content is less than 1% by mass, but the productivity is remarkably lowered. If it exceeds 30% by mass, the stability of the alkali silicate aqueous solution is remarkably lowered and the viscosity becomes high, and spray drying may not be possible. Even if the particles can be spray-dried, the particle size distribution, outer shell thickness, etc. become extremely non-uniform, and the applications of the obtained particles may be limited. As the alkali silicate, water-soluble sodium silicate and potassium silicate can be used. Sodium silicate is preferred.

As the spray-drying method, for example, conventionally known methods such as a rotating disk method, a pressurized nozzle method, and a two-fluid nozzle method can be adopted. A two-fluid nozzle method is preferred here.

In the spray drying, the inlet temperature of the spray dryer is preferably 300-600°C, more preferably 350-550°C. The outlet temperature is preferably 120-300°C, more preferably 130-250°C. Hollow particles can be stably obtained by such temperature setting.

(Second step)
Next, the alkali contained in the particles granulated in the first step is removed. A method of removing by adding an acid for neutralization is suitable. A treatment in which the particles are immersed in an acid solution is preferred. At this time, the molar ratio (Ma/Msp) between the number of moles of M ₂ O (Msp) and the number of moles of acid (Ma) in the particles is preferably 0.6 to 4.7, more preferably 1 to 4.5. preferable. If this molar ratio is less than 0.6, the amount of acid relative to _M2O is too low. Therefore, the formation of a silica skeleton of silicic acid, which is thought to occur with the removal of alkali, does not proceed, and the particles may partially dissolve or the dissolved alkali silicate may gel. Even if the molar ratio exceeds 4.7, the formation of the silica skeleton does not proceed further, and the acid is excessive, which is not economical.

Further, it is preferable that the particles are immersed in an acid aqueous solution so that the concentration of the particles is 1 to 30% by mass as SiO ₂ . If the amount is less than 1% by mass, there is no problem in alkali removal and cleaning properties, but the production efficiency is lowered. If it exceeds 30% by mass, the concentration may be too high and the alkali removal and cleaning efficiency may be lowered. 5 to 25% by mass is more preferable.

The conditions for immersion in the acid aqueous solution are not particularly limited as long as the desired amount of alkali can be removed, and the treatment temperature is usually 5 to 100° C. and the treatment time is 0.5 to 24 hours. After that, it is preferable to wash by a conventionally known method. For example, it is filtered and washed with pure water. The acid treatment and washing may be repeated as necessary.

The residual amount (mass ratio) of alkali (M) after alkali removal is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. By sufficiently removing the alkali in this step, it is possible to prevent the particles from coalescing in the subsequent steps and to prevent the generation of sintered particles in the firing step. In addition, it is known that the residual amount (content) of alkali affects the dielectric properties. By sufficiently removing the alkali in this step, it is possible to obtain particles capable of achieving a low dielectric constant and a low dielectric loss tangent even when an aqueous alkali silicate solution is used as a raw material.

The alkali content of the final product (particles that make up the powder) is also preferably within the range described above, and is usually equivalent to the alkali content after the alkali removal step.

The amount of residual alkali can be measured using an atomic absorption photometer, using a sample of powder dissolved in acid. Na is measured when sodium silicate is used, and K is measured when potassium silicate is used. Specifically, it will be described in Examples.

As acids used in this step, mineral acids (hydrochloric acid, nitric acid, sulfuric acid, etc.) and organic acids (acetic acid, tartaric acid, malic acid, etc.) can be used. Mineral acids are preferably used, and sulfuric acid having a high valence is particularly preferred.

(Third step)
Next, the particles after the alkali removal treatment are calcined. The firing temperature is preferably 600-1200°C, more preferably 900-1100°C. When the firing temperature is lower than 600° C., the amount of remaining SiOH groups is large and the dielectric loss tangent of the particles is high. Therefore, it is difficult to obtain the effect of reducing the dielectric loss tangent even if it is added to the resin. When the firing temperature exceeds 1200° C., the particles are likely to be sintered together, so irregularly shaped particles and coarse particles are likely to be generated. This causes deterioration in filterability and injectability of the resin composition-forming liquid.

(Classification process)
Fine particles smaller than 2.0 μm are removed by performing a classification treatment between the first step and the third step. When the classification treatment is performed before removing the alkali, it is necessary to perform the classification treatment immediately after granulation in order to prevent the hollow particles from absorbing moisture (deliquescence) and aggregating and coalescing. Further, when the classification treatment is performed before firing, the classification treatment may be performed following the alkali removal treatment.

By the classification process, the amount of fine particles with a particle size of less than 2.0 μm is reduced to 20% by volume or less. The content is preferably 15% by volume or less, more preferably 10% by volume or less, even more preferably 5% by volume or less, and most preferably 3% by volume or less. Through this classification process, the ratio of suspended particles present in the powder can be controlled within a predetermined range. Generally, the content of fine particles and coarse particles in the final product does not change significantly from the content after the classification step.

The classification process in this classification process means particle size classification that separates powders by particle size with the aim of aligning the particle size of the powder. Fluid classification can be mentioned as an operation of this particle size classification. Fluid classification can be classified into dry classification and wet classification. Wet classification is carried out while particles are suspended in water. As a result, SiOH groups are generated on the particle surface, which may adversely affect the dielectric properties. Dry classification is therefore preferred.

In principle, classifiers used for dry classification can be broadly classified into gravity classifiers, inertial classifiers, and centrifugal classifiers. More precise classification is possible by using an inertial classifier or a centrifugal classifier. Classifiers that can accurately classify even light particles such as the present invention include Elbow Jet manufactured by Nittetsu Mining Co., Ltd., SG Separator manufactured by 3M Japan, Aerofine Classifier manufactured by Nisshin Engineering, and Microspin manufactured by Nippon Pneumatic Industry. can be mentioned. Among these, an elbow jet and an aerofine classifier are preferable.

In addition, a drying treatment step may be provided as appropriate during the manufacturing process. The drying treatment can be provided between the alkali removal treatment and the classification treatment, between the classification treatment and the firing, or both, or between the alkali removal treatment and the firing. It may be provided multiple times as required. Alternatively, the drying treatment may be performed before firing, and the classification treatment may be performed between the drying treatment and firing. In order to enjoy the effect of the present invention more, it is preferable to carry out a classification treatment after the drying treatment and then perform the firing. Heat drying is suitable as the drying treatment. The drying temperature is preferably 50 to 400°C, more preferably 50 to 200°C. Specific examples include a method of drying at a low temperature of about 50 to 200°C over a long period of time, a method of gradually increasing the temperature, and a method of changing the temperature in several stages for drying. can.

Furthermore, it is preferable to provide a sieving process for sieving the particle lumps at least after drying and after firing. The term "particle agglomerate" refers to, for example, particles having a particle size exceeding 50 μm, and a sieve having an opening (mesh number) capable of removing such a particle agglomerate is appropriately used.

Examples of the present invention will be specifically described below.

[Example 1]
Using 30000 g of water glass aqueous solution (SiO ₂ /Na ₂ O molar ratio 3.2, SiO ₂ concentration 24% by mass), one of the two-fluid nozzles is supplied with a flow rate of 0.62 kg / hr, and the other nozzle is supplied with air at 31800 L / Hollow particles were granulated by spraying with hot air having an inlet temperature of 400° C. at a flow rate of hr (empty/liquid volume ratio of 63,600). Here, the outlet temperature was 150° C. (first step). A small amount of solid particles may also be granulated in the first step, but it is not necessary to remove the solid particles to proceed to the next step.

Next, 5000 g of the hollow particles (that is, the particles granulated in the first step) were immersed in 32000 g of an aqueous sulfuric acid solution having a concentration of 10% by mass and stirred for 15 hours. The solid content (SiO ₂ ) concentration is 10.2% by mass. Further, since sulfuric acid is a divalent acid, the ratio (Ma/Msp) of the number of moles (Ma) of acid and the number of moles (Msp) of alkali (Na ₂ O) is 3.3. The temperature of the dispersion was 35° C. and the pH was 3.0. After this immersion treatment, filtration washing was performed with pure water (second step).

Then, it was dried in a dryer at 120°C for 24 hours. After drying, it was pulverized and passed through a sieve with an opening of 75 μm to remove particle lumps.

Next, a dry centrifugal classification process was performed using a cyclone manufactured in-house and setting the flow velocity of the powder transportation line to 5 m/s. Particles trapped in the cyclone were recovered.

A powder containing hollow particles was obtained by heat-treating the collected particles at 1000°C for 10 hours (third step). After the baking, particle lumps (foreign matters) were removed with a sieve with an opening of 150 μm.

The resulting powder was mixed with a liquid acid anhydride "Likacid MH700 manufactured by Shin Nippon Rika Co., Ltd.", an imidazole-based epoxy resin curing agent "2PHZ-PW manufactured by Shikoku Kasei Co., Ltd.", and a liquid epoxy resin "ZX manufactured by Nippon Steel Chemical & Materials Co., Ltd." -1059". Here, the proportion of "ZX-1059" is 100 parts by mass, "Rikacid MH700" is 86 parts by mass, and "2PHZ-PW" is 1 part by mass, and the proportion of powder in the formulation (paste) is 35% by volume. It was blended so that This compound was preliminarily kneaded in a planetary mill and then kneaded in a triple roll to obtain a paste (resin composition). This paste was cured by heating at 170° C. for 2 hours to obtain a plate-shaped resin molding (resin product) of 50 mm×50 mm×1 mm.

The physical properties of the powder and resin molding obtained as described above were measured and evaluated as follows. The results are shown in Table 1 together with the preparation conditions. Other examples and comparative examples were also carried out in the same manner.

(1) Average particle size (D50), maximum particle size (D100), and amount of fine particles Using a particle size analyzer (Laser Micronsizer LMS-3000 manufactured by Seishin Enterprise Co., Ltd.), the particle size distribution of the powder was measured in a dry manner. . Average particle size (D50) and maximum particle size (D100) were obtained from the measurement results. Further, the particle size distribution was analyzed to calculate the volume ratio of particles less than 2.0 μm, which was defined as the amount of fine particles.

(2) Amount of residual alkali The powder was pretreated with sulfuric acid/hydrofluoric acid, dissolved in hydrochloric acid, and the amount of Na was measured by atomic absorption spectrometry using an atomic absorption spectrophotometer (Z-2310 manufactured by Hitachi). .

(3) Particle Density and Porosity Using Ultrapyc1200e manufactured by Quantachrome Instruments, the average density of particles contained in the powder (particle density) was measured by the gas pycnometer method. Nitrogen gas was used as the gas.
From this particle density, the porosity (%) was calculated by the formula “[2.2-(particle density)]/2.2×100”. Assuming that the powder is composed of silica particles, this formula used a silica density of 2.2 g/cm ³ .

(4) Permittivity (Dk) and dielectric loss tangent (Df) of powder
A dielectric constant (Dk) and a dielectric loss tangent (Df) were measured by a cavity resonator perturbation method using a network analyzer (manufactured by Anritsu, MS46122B) and a cavity resonator (1 GHz). It was measured according to ASTM D2520 (JIS C2565).

(5) Percentage of Floating Particles, Suspended Particles, and Sedimented Particles When Suspended in Water First, powder and water were mixed so as to make 5% by mass, and ultrasonic treatment was performed for 10 minutes. After the resulting dispersion was allowed to stand at 25° C. for 24 hours, suspended particles, suspended particles and settled particles were collected. Subsequently, each particle was dried at 105° C. for 24 hours and then weighed to calculate the ratio.

(6) Dielectric constant (Dk) and dielectric loss tangent (Df) of resin molding
Dielectric constant (Dk) and dielectric loss tangent (Df) of a plate-shaped molding (resin molding) of 50 mm × 50 mm × 1 mm were measured at 9.4 GHz using a network analyzer (manufactured by Anritsu, MS46122B) and a coaxial resonator. It was measured. It was compared with a resin molding containing no powder (filler) according to the following formula and evaluated according to the following criteria.

Dielectric constant (Dk) reduction rate (%) = (dielectric constant without powder blending - dielectric constant with powder blending)/dielectric constant without powder blending x 100

○: Reduction rate > 0
△: reduction rate = 0
×: reduction rate < 0

Dielectric loss tangent (Df) reduction rate (%) = (Dielectric loss tangent without powder blending - Dielectric loss tangent with powder blended) / Dielectric loss tangent without powder blended x 100

◎: Reduction rate of 50% or more ○: Reduction rate of 30% or more and less than 50% △: Reduction rate of 20% or more and less than 30% ×: Reduction rate of less than 20%

[Example 2]
In the classification process, a dry inertia classification process was performed using an elbow jet (EJ-15) manufactured by Nittetsu Mining Co., Ltd. This device can classify powder into three types: F powder (fine powder), M powder (fine powder), and G powder (coarse powder). At this time, the F edge distance was adjusted so that the fine particles of less than 2.0 μm contained in the M powder (fine powder) were 2% by volume or less. M powder was collected and the subsequent steps were performed. A powder and a resin molding were prepared in the same manner as in Example 1 except for this.

[Example 3]
In the classification process, a dry centrifugal (semi-free vortex) classification treatment was performed using an Aerofine Classifier manufactured by Nisshin Engineering. The angle of the blades and the like were adjusted and classified so that the fine particles of less than 2.0 μm contained in the recovered powder were 20% by volume or less. A powder and a resin molding were prepared in the same manner as in Example 1 except for this.

[Example 4]
The angles of the blades and the like were adjusted so that the fine particles of less than 2.0 μm contained in the collected particles were 10% by volume or less. A powder and a resin molding were prepared in the same manner as in Example 3 except for this.

[Comparative Example 1]
A powder and a resin molding were prepared in the same manner as in Example 1, except that the classification treatment (classification process) was not performed.

[Comparative Example 2]
In the first step, the inlet temperature of the spray dryer was changed to 250°C, and in the second step, the immersion stirring time was changed to 1.5 hours. Furthermore, no classification step was performed. A powder and a resin molding were prepared in the same manner as in Example 1 except for this.

[Comparative Example 3]
In the first step, the inlet temperature of the spray dryer was changed to 420°C, and no classification treatment (classification step) was performed. A powder and a resin molding were prepared in the same manner as in Example 1 except for this.

[Comparative Example 4]
Classification treatment (classification process) was performed after firing. A powder and a resin molding were prepared in the same manner as in Example 1 except for this.

As shown in Table 1, the powders according to the examples and the resin moldings containing the powders have low dielectric constants and low dielectric loss tangents.

Claims

A powder comprising hollow particles having a cavity inside a nonporous outer shell,
The average particle diameter (D50) of the powder is 2.0 to 10.0 μm, and the content of fine particles having a particle diameter of less than 2.0 μm is 20% by volume or less,
When the powder is suspended in water, the suspended particles are 7.0 to 25.0% by mass, the suspended particles are 0 to 4.0% by mass, and the sedimented particles are 71.0 to 93.0% by mass. A powder characterized by:
A method for producing a resin composition, which comprises blending the powder according to claim 1 with a resin material.
a first step of preparing particles by spray-drying an aqueous alkali silicate solution in a hot air stream;
a second step of removing the alkali contained in the particles;
a third step of firing the alkali-removed particles;
has
A method for producing powder, wherein a classification step for removing fine particles having a particle size of less than 2.0 μm is provided between the first step and the third step.
The method for producing powder according to claim 3, wherein in the second step, the amount of alkali contained in the particles is reduced to 300 ppm or less.
A drying step for drying the hollow particles is provided before the third step,
5. The method for producing powder according to claim 3, wherein the classifying step is provided between the drying step and the third step.
6. The method for producing powder according to any one of claims 3 to 5, wherein in the classifying step, the fine particles are removed by a dry classification treatment.