JP2023150838A - Powder and method for producing the same, and method for producing resin composition - Google Patents

Abstract

To provide powder containing hollow particles which enables reduction in both the dielectric constant and the dielectric loss tangent of an insulation material, and have strength durable for the manufacturing process.SOLUTION: There is provided powder containing hollow particles each having a cavity inside a nonporous outer shell. An average particle diameter (D50) of the powder is 10.0 μm or more and 20.0 μm or less, and 1.0 vol.% or less of coarse particles having a particle diameter larger than 45 μm are contained therein. When the powder is suspended in water, floating particles are 10.0-30.0 mass%, suspended particles are 0-4.0 mass%, and precipitated particles are 66.0-90.0 mass%.SELECTED DRAWING: None

Description

The present invention relates to a powder suitable as a filler for semiconductor insulating materials. In particular, the present invention relates to a powder containing hollow particles having a cavity inside a non-porous outer shell.

In recent years, information communication has become faster and larger in capacity. Therefore, materials used in communication equipment are required to have a low dielectric constant (low Dk) and a low dielectric loss tangent (low Df). For example, printed wiring boards on which semiconductor elements are mounted are required to have insulating materials with a low dielectric constant and a low dielectric loss tangent. 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 lower permittivity and lower dielectric loss tangent of insulating materials, resin materials, which are the main insulating materials, are being developed.

Inorganic or organic fillers are added to such resin materials in order to improve durability (rigidity), heat resistance, and the like. It is known to use metal oxides such as silica, boron nitride, alumina, and titania as inorganic fillers. Furthermore, in order to lower the dielectric constant, it is known to incorporate hollow particles or silica as a filler (see, for example, Patent Document 1).

Furthermore, in order to lower the dielectric constant and dielectric loss tangent, it is known to use glass microbubble particles (hollow particles) containing silicon, calcium, sodium or potassium, boron, phosphorus, and zinc as fillers (for example, Patent Document 2).

Further, hollow particles with an average hollowness ratio of 70% by volume or more and an average particle diameter of 3 to 20 μm are known (see, for example, Patent Document 3).

Japanese Patent Application Publication No. 2017-057352 WO2015/009461 WO2007/125891

Among materials used as fillers, silica is superior in terms of low dielectric constant and low dielectric loss tangent. However, as data communications are rapidly increasing in capacity and processing speed, there is a need for lower dielectric constants and lower dielectric loss tangents. However, since the filler described in Patent Document 1 has a small particle size, it is difficult to lower the dielectric constant any further. Even if a large particle size could be achieved, the particle strength would be low.

Further, the glass microbubble particles described in Patent Document 2 are made of multiple elements and contain many impurities (particularly Na), so it has been difficult to lower the dielectric loss tangent.

Further, the hollow particles disclosed in Patent Document 3 have a thin outer shell and a high porosity, and therefore do not have sufficient particle strength. Therefore, cracks tend to occur when kneading with resin, making it difficult to lower the dielectric constant.

As described above, with the conventional techniques, it has not been possible to achieve both a reduction in dielectric constant and dielectric loss tangent and a high level of particle strength.

The present inventors have discovered that a powder containing hollow particles that does not contain coarse particles and satisfies a predetermined condition can achieve a low dielectric constant and a low dielectric loss tangent of an insulating material, as well as have strength that can withstand the manufacturing process of the insulating material. I found that I have it.

That is, the powder according to the present invention contains hollow particles having a cavity inside a non-porous outer shell, and has an average particle diameter (D50) of 10.0 μm or more and 20.0 μm or less, and a particle diameter of 45 μm or less. Contains 1.0% by volume or less of large diameter particles. When this powder is suspended in water, suspended particles account for 10.0 to 30.0 mass%, suspended particles account for 0 to 4.0 mass%, and settled particles account for 66.0 to 90.0 mass%. .

In addition, the method for producing 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, and a second step of neutralizing and removing alkali contained in the particles with an acid. , a third step of drying the particles, and a fourth step of firing the particles, and between the second step and the third step, the presence of coarse particles with a particle size of 45 μm or more is 1.0% by volume. A classification step is provided in which wet classification is performed as follows.

The powder of the present invention realizes a low dielectric constant and a low dielectric loss tangent of an insulating material, and has strength enough to withstand the manufacturing process of the insulating material. Therefore, excellent insulating materials can be stably manufactured.

The powder of the present invention contains hollow particles having a cavity inside a non-porous outer shell, and has an average particle diameter (D50) of 10.0 μm or more and 20.0 μm or less and larger than 45 μm (hereinafter referred to as , coarse particles) is 1.0% by volume or less. When this powder is suspended in water, suspended particles account for 10.0 to 30.0 mass%, suspended particles account for 0 to 4.0 mass%, and settled particles account for 66.0 to 90.0 mass%. . In addition to hollow particles, the powder of the present invention may also contain a small amount of solid particles. This is because solid particles may also be unexpectedly produced during the preparation of hollow particles. Since solid particles without internal cavities have a high specific gravity, they are basically considered to be latent within the sedimented particles. It is preferable that 90% by mass or more of the particles contained in the powder are hollow particles.

Here, particles that are dispersed in water when suspended in water are defined as suspended particles, and particles with a light specific gravity that float in the upper layer (near the water surface) are defined as suspended particles. Such suspended particles usually have high porosity. Therefore, as the number of floating particles added to the resin material increases, the dielectric constant and dielectric loss tangent of the resin product (molded product) decrease. In addition, generally, the higher the porosity of the particles, the larger the particle diameter (the smaller the particle diameter, the lower the porosity). Floating particles tend to have low particle strength because the ratio (t/d) of particle diameter (d) to outer shell thickness (t) is small. Therefore, there is a risk that the particles may break during the process of mixing the resin material and the particles until the resin product is molded (ie, during the manufacturing process). The cracked particles not only impede lower dielectric constant and lower dielectric loss tangent, but also deteriorate the fluidity of the resin composition, reduce the uniformity of the resin product, and create voids inside the resin product. This is a factor that causes However, by controlling the amount of suspended particles to 10.0 to 30.0% by mass of the entire particles, it is possible to suppress particle cracking and lower the dielectric constant and dielectric loss tangent.

In other words, by controlling the amount of suspended particles, the desirable properties of particles with high porosity (e.g., low dielectric constant and low dielectric loss tangent) can be ensured, while the unfavorable properties of particles with high porosity (e.g., low dielectric loss tangent) can be ensured. (occurrence of cracks) can be suppressed to a non-problematic level. Among the suspended particles, there are particles with a high porosity even if they are small in diameter, and such particles are less likely to crack during the manufacturing process than large-diameter particles, improving the particle strength as a whole. The content of suspended particles is preferably 12.5 to 25.0% by mass, more preferably 15.0 to 20.0% by mass. Further, the content of the precipitated particles is preferably 70.0 to 88.0% by mass, more preferably 75.0 to 85.0% by mass.

Moreover, the average particle diameter (D50) of the powder is 10.0 μm or more and 20.0 μm or less. This achieves both reduction in dielectric constant and improvement in particle strength. When granulated by a spray drying method, the smaller the particle size, the lower the porosity tends to be. Therefore, powder with an average particle diameter of less than 10.0 μm has a low dielectric constant reduction effect. Although there is a method of increasing the porosity by using powder with a particle size of less than 10.0 μm, the smaller the particle size, the thinner the outer shell becomes, and thus the number of particles that break during particle preparation increases. It is difficult to remove cracked particles, and if powder containing cracked particles is blended into a resin material, the fluidity of the resin composition may deteriorate, resulting in a decrease in the uniformity of the resin molded product, or the inside of the resin molded product. This can cause voids to occur. On the other hand, when the average particle diameter exceeds 20.0 μm, the powder contains many large hollow particles. Generally, the larger the hollow particle is, the higher the porosity and therefore the lower the particle strength. Therefore, the average particle diameter is preferably 15.0 μm or less.

Further, the amount of coarse particles (particle diameter of more than 45 μm) contained in the powder is 1.0% by volume or less. By reducing the coarse particles to 1.0% by volume or less by wet sieving, it is possible to suppress particle cracking and achieve both a low dielectric constant and a low dielectric loss tangent. It is generally known that particles (powder) granulated using a spray drying method have a wide particle size distribution. Naturally, the powder will contain a considerable amount of large particles. When such powders are mixed into resin materials, coarse particles with high porosity and low strength occupy a large volume, which increases the frequency of cracking particles due to the force of kneading during the manufacturing process. . As a result, desired dielectric properties cannot be obtained. Therefore, as described above, it is necessary to reduce the coarse particles to 1.0% by volume or less by wet sieving. The content of coarse particles is preferably 0.5% by volume or less, more preferably 0.3% by volume or less, and particularly preferably 0% by volume.

Such powder can have a high deformation coefficient even though it contains relatively large particles with an average particle diameter of 10.0 μm or more. Here, the deformation coefficient is determined from the displacement that occurs in the powder when a load is applied. The powder that contains more particles with higher particle strength has a larger deformation coefficient. The deformation coefficient can be increased by controlling the amount of suspended particles while removing coarse particles that tend to cause cracks. The deformation coefficient of the powder is preferably greater than 3000 kgf/mm. If the deformation coefficient is less than 3000 kgf/mm, it cannot withstand kneading in the manufacturing process, grain cracking occurs, and desired dielectric properties cannot be obtained.

The porosity of the powder is preferably 30.0% by volume or more and less than 70.0% by volume. With such a porosity, it is possible to achieve a low dielectric constant and a low dielectric loss tangent, and it is also possible to maintain particle strength above a predetermined level and effectively suppress particle cracking. The porosity is more preferably 40.0 volume % or more, and even more preferably 50.0 volume % or more. On the other hand, the content is more preferably 65.0% by volume or less, and even more preferably 55.0% by volume or less.

Further, the specific surface area of the powder is preferably 3.0 m ² /g or less. The larger the specific surface area, the more likely the particles will aggregate in the resin composition. Therefore, fluidity decreases and moldability is affected.

Here, as the particles constituting the powder, silica-based particles containing silica as a main component are suitable. Therefore, the hollow particles (shell) contained in the powder may contain inorganic oxides such as alumina, zirconia, titania, etc. 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, even more preferably 95% by mass or more, and particularly preferably consists essentially of silica.

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

As the resin, a curable resin generally used for electronic materials such as semiconductors can be used. A photocurable resin may be used, but a thermosetting resin is preferable. Examples of the curable resin include epoxy resin, polyphenylene ether resin, fluorine resin, polyimide resin, bismaleimide resin, acrylic resin, methacrylic resin, silicone resin, BT resin, cyanate resin, etc. can. Epoxy resins include bisphenol type epoxy resin, novolak type epoxy resin, triphenolalkane type epoxy resin, epoxy resin with biphenyl skeleton, epoxy resin with naphthalene skeleton, dicyclopentadienephenol novolac resin, phenol aralkyl type epoxy resin, glycidyl Examples include 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 powder A and curable resin B in a mass ratio (A/B) of 10/100 to 95/100. Thereby, it is possible to fully exhibit its function as a filler while maintaining the properties of the resin composition such as fluidity. The mass ratio (A/B) is more preferably 30/100 to 80/100.

Further, the resin composition preferably contains a curing agent such as a phenol compound, an amine compound, or an acid anhydride. When using an epoxy resin as a curable resin, use a phenol resin having two or more phenolic hydroxyl groups in one molecule (bisphenol type resin, novolac resin, triphenol alkane type resin, resol type phenol resin, phenol aralkyl resin) as a curing agent. , biphenyl type phenol resin, naphthalene type phenol resin, cyclopentadiene type phenol resin, etc.) and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methylnadic anhydride. Various additives such as colorants, stress relievers, antifoaming agents, leveling agents, coupling agents, flame retardants, and curing accelerators 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 thermosetting resin, powder, curing agent, additives, etc. are mixed and kneaded using a roll mill or the like. The obtained resin composition is applied to a substrate and cured by heat, ultraviolet rays, etc.

[Method for producing powder]
The method for producing powder of the present invention includes a particle preparation step in which particles are prepared by spray-drying an aqueous alkali silicate solution in a hot air stream, and an alkali removal step in which the alkali contained in the prepared particles is neutralized and removed with an acid. step, a drying step of drying the particles from which the alkali has been removed, and a firing step of baking the particles, and between the alkali removal step and the drying step, the presence of coarse particles with a particle size of 45 μm or more is 1.0 μm. A classification step is provided in which wet classification is carried out so that the concentration is less than or equal to % by volume.

Through such a process, the above-mentioned powder can be obtained.

Generally, when producing particles by calcination, it is considered preferable to carry out the process at the final stage after calcination in order to adjust the particle size. However, in this case, it is done before firing. If the firing process is performed without performing the classification process, the coarse particles that should be removed will remain in the firing process. Coarse particles have high porosity and tend to crack easily. Therefore, there is a risk of cracking due to the stress of shrinkage caused by heating. Since the fragments generated by the cracks are dense silica without voids, they become an obstacle to lowering the dielectric constant and lowering the dielectric loss tangent. Such inconveniences can be avoided by performing the classification process before firing. Therefore, a reduction in the dielectric constant and a reduction in the dielectric loss tangent of the particles can be more reliably achieved, and particles compatible with high-speed data communication can be obtained. Each step will be explained in detail below.

(Particle preparation process)
In this step, particles are granulated by spray drying an aqueous alkali silicate solution in a hot air stream. Although this step is performed to obtain hollow particles, it is difficult to make all particles hollow, and the granulated particles may eventually include solid particles. There is sex. In this case, solid particles are also included in the powder obtained through the steps described below. However, as long as the powder has the above-mentioned characteristics, the expected effect can be obtained even if it contains solid particles.

The molar ratio (SiO ₂ /M ₂ O) of SiO ₂ and M ₂ O (M is an alkali metal) of the alkali silicate is preferably 1 to 5, more preferably 2 to 4. When 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 performed in the alkali removal step described below. Furthermore, since the spray-dried product becomes highly deliquescent, it is difficult to obtain desired hollow particles. When this molar ratio exceeds 5, the solubility of the alkali silicate decreases, making it difficult to prepare an aqueous solution. Even if an aqueous solution can be prepared, hollow particles may not be granulated by spray drying.

The concentration of the alkali silicate aqueous solution as SiO ₂ is preferably 1 to 30% by mass, and preferably 5 to 28% by mass. Although production is possible with less than 1% by mass, productivity is significantly reduced. If it exceeds 30% by mass, the stability as an aqueous alkali silicate solution decreases significantly and becomes highly viscous, making spray drying impossible in some cases. Even if spray drying is possible, the particle size distribution, shell thickness, etc. may become extremely non-uniform, which may limit the uses of the obtained particles. Examples of the alkali silicate include water-soluble sodium silicate and potassium silicate. Sodium silicate is preferred.

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

In spray drying, the inlet temperature in the spray dryer is preferably 300 to 600°C, more preferably 350 to 550°C. Further, the outlet temperature is preferably 120 to 300°C, more preferably 130 to 250°C. By setting the temperature in this manner, hollow particles can be stably obtained.

(Alkali removal process)
Next, the alkali contained in the particles granulated in the particle preparation step is neutralized and removed with an acid. A treatment in which the particles are immersed in a solution of acid 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, preferably 1 to 4.5. . If this molar ratio is less than 0.6, the amount of acid relative to _M2O is too small. 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 silica skeleton will not proceed further, and the acid will be in excess, which is not economical.

Further, it is preferable to immerse the particles in an acid aqueous solution so that the concentration of the particles is 1 to 30% by mass as SiO ₂ . If it is less than 1% by mass, there will be no problem with alkali removal or cleaning performance, but production efficiency will decrease. If it exceeds 30% by mass, the concentration may be too high and the alkali removal and cleaning efficiency may decrease. More preferably 5 to 25% by mass.

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

The residual amount (mass ratio) of alkali (M) after alkali removal is preferably 200 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less. By sufficiently removing the alkali in this step, it is possible to prevent particles from coalescing in a later step, and to prevent the generation of sintered particles in the firing step. Furthermore, it is known that the residual amount (content) of alkali affects dielectric properties. By sufficiently removing the alkali in this step, it is possible to obtain particles with a low dielectric constant and a low dielectric loss tangent even when an aqueous alkali silicate solution is used as the raw material.

The amount of alkali in the final product (particles constituting the powder) is preferably within the above range, and is usually equivalent to the amount of alkali after the alkali removal step.

The residual amount of alkali can be measured using an atomic absorption spectrophotometer using a sample obtained by dissolving powder with an acid. When sodium silicate is used, Na is measured, and when potassium silicate is used, K is measured. Specifically, this will be explained in Examples.

Examples of acids used in this step include mineral acids (hydrochloric acid, nitric acid, sulfuric acid, etc.) and organic acids (acetic acid, tartaric acid, malic acid, etc.). Mineral acids are preferably used, with sulfuric acid having a high valence being particularly preferred.

(Classification process)
Coarse particles are removed by performing a classification process between the alkali removal process and the drying process described below. In this classification step, particle size classification is performed to divide the powder according to particle size in order to make the particle size of the powder uniform. Particle size classification operations can be broadly divided into sieving and fluid classification. It is preferable to use sieving, which is not affected by the porosity of particles and has high production efficiency. In sieving, the openings of the sieve screen are used to classify the material. In the present invention, wet sieving was used in order to maintain high particle dispersibility and reduce damage to particle surfaces.

In this step, a sieve with a mesh size that is large enough to remove particles that are easy to break during the manufacturing process is used as appropriate. In order to reduce the coarse particles contained in the powder to 1.0% by volume or less, it is preferable to use a sieve of 300 mesh or more.

Further, by the classification step, the content of suspended particles can be controlled to 10.0 to 30.0% by mass, and the content of settled particles can be controlled to 66.0 to 90.0% by mass.

(drying process)
Next, the classified particles are subjected to a drying process. This may be repeated multiple times if necessary. However, since the number of steps increases and productivity decreases, it is preferable to carry out the drying treatment once during the manufacturing process. Heat drying is suitable as a drying process. The drying temperature is preferably 50 to 400°C, more preferably 50 to 200°C. Specifically, there are methods of drying at a low temperature of about 50 to 200 degrees Celsius over a long period of time, methods of gradually increasing the temperature to dry, and methods of changing the temperature in several stages. be able to.

(Firing process)
Next, the particles after the drying treatment are fired. The firing temperature is preferably 600 to 1200°C, more preferably 900 to 1100°C. When the firing temperature is less than 600° C., the amount of SiOH groups remaining is large and the dielectric loss tangent of the particles becomes high. Therefore, even if it is blended into a resin material, it is difficult to obtain the effect of reducing the dielectric loss tangent. When the firing temperature exceeds 1200° C., particles tend to sinter together, so irregularly shaped particles and coarse particles are likely to be produced.

Furthermore, it is preferable to provide a crushing step between the drying step and the firing step. Even if the particles aggregate during the drying process, they can be separated into single particles. Therefore, sintering of particles can be prevented.

As a crushing device, a known ball mill, bead mill, hammer mill, etc. can be used. In order to prevent the powder from cracking due to mechanical loads during the process, a continuous pin mill is suitable because it can crush the powder in a short time using minimal impact force.

Furthermore, it is preferable to provide a step of sieving the particle agglomerates after the firing step. Note that the particle agglomerate refers to large particles with a particle size exceeding 150 μm, for example. In this step, a sieve with an opening (mesh number) that can remove particle agglomerates is used as appropriate. For example, a sieve with an opening of 150 μm is used.

Examples of the present invention will be specifically described below.

[Example 1]
Using 30,000 g of water glass aqueous solution (SiO ₂ /Na ₂ O molar ratio 3.2, SiO ₂ concentration 24.0% by mass), air was supplied to one of the two-fluid nozzles at a flow rate of 0.62 kg/hr and to the other nozzle. Hollow particles were granulated by spraying into hot air with an inlet temperature of 350° C. at a flow rate of 15,900 L/hr (empty/liquid volume ratio: 31,800). Here, the outlet temperature was 130°C (particle preparation step). At this time, a small amount of solid particles may also be granulated, but it is not necessary to remove the solid particles and 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. At this time, the solid content (SiO ₂ ) concentration is 10.2% by mass, and the ratio of the number of moles of acid (Ma) to the number of moles of alkali (Na ₂ O) (Msp) (Ma/Msp) is 3.5. becomes. The temperature of the dispersion after stirring was 35° C., and the pH was 3.0. After the immersion treatment, filtering and washing with pure water was performed to obtain a cake product (alkali removal step).

Next, the solid content of the cake product after washing was measured, and based on the measured value, pure water was added to the cake product so that the concentration was 10% by weight to prepare a dispersion liquid. Thereafter, in order to remove coarse particles, this dispersion was passed through a vibrating sieve with an opening of 45 μm, and the particles passing through the sieve were collected (wet classification step).

The particles were heat-treated at 1000° C. for 10 hours (calcination step). As a result, a powder containing hollow particles was obtained.

This powder was mixed with a liquid acid anhydride "Rikacid MH700 manufactured by Shin Nippon Rika Co., Ltd." and an imidazole-based epoxy resin curing agent "2PHZ-PW manufactured by Shikoku Kasei Co., Ltd." and a liquid epoxy resin "ZX-1059 manufactured by Nippon Steel Chemical & Materials Co., Ltd." ” was added. Here, the ratio 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 ratio of powder in the compound (paste) is 35% by volume. It was blended so that This mixture was pre-kneaded using a planetary mill and then kneaded using three rolls 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) measuring 50 mm x 50 mm x 1 mm.

The physical properties of the powder and resin molded product obtained as described above were measured and evaluated as follows. The results are shown in Table 1 along with the preparation conditions. The same procedure was carried out in other Examples and Comparative Examples.

(1) Average particle diameter (D50), amount of coarse particles Sample the powder to a size of ^about 1.0 cm, and use a particle size analyzer (Laser Micron Sizer LMS-3000 manufactured by Seishin Enterprise Co., Ltd.) to determine the particle size distribution of the powder using a dry method. was measured. The average particle diameter (D50) was obtained from the measurement results. Furthermore, this particle size distribution was analyzed to calculate the volume ratio of coarse particles having a particle diameter larger than 45 μm, which was defined as the amount of coarse particles (volume %).

(2) Specific surface area (SA)
After the powder was allowed to stand for 1 hour in an environment of 300° C., the specific surface area was measured by the BET method (one point method) using a fully automatic specific surface area measuring device (Macsorb manufactured by Mountec). Here, the measurement method specified in Japanese Industrial Standard JIS Z8830 was followed.

(3) Remaining amount of Na After the powder was pretreated with sulfuric acid/hydrofluoric acid, it was dissolved in hydrochloric acid, and the amount of Na was measured by atomic absorption spectrometry using an atomic absorption spectrophotometer (Hitachi Z-2310). .

(4) Particle density, porosity: Randomly sample powders of about 20.0 cm ³ and measure the average density of particles contained in the powders (particle density ) was measured. Nitrogen gas was used as the gas. Particle density was measured by the measurement method specified in Japanese Industrial Standards JIS Z8807.

From this particle density, the porosity (%) was calculated using the formula “[2.2−(particle density)]/2.2×100”. Assuming that the powder is composed of silica particles, this formula uses a density of silica of 2.2 g/cm ³ .

(5) Dielectric constant (Dk) and dielectric loss tangent (Df) of powder
The dielectric constant (Dk) and the dielectric loss tangent (Df) were measured by the cavity resonator perturbation method using a network analyzer (manufactured by Anritsu Corporation, MS46122B) and a cavity resonator (1 GHz). Measured in accordance with ASTM D2520 (JIS C2565).

(6) Ratio of suspended particles, suspended particles, and settled particles when suspended in water First, powder and water were mixed to a concentration of 5.0% by mass, and subjected to ultrasonication for 10 minutes. After the resulting dispersion was allowed to stand at 25° C. for 24 hours, floating particles, suspended particles, and sedimented particles were collected. Each collected particle was dried at 105° C. for 24 hours, then weighed, and the proportion thereof was calculated.

(7) Deformation coefficient Powder and glycerin were mixed and dispersed at a weight ratio of 2:1. This mixture is filled into a specified mold (diameter 25 mm, height 64 mm). After filling, the mold is placed in a press machine (manufactured by NP Systems) and a load is applied in stages. The load (kgf) and vertical displacement (mm) at that time were plotted. As the load increases, the particles contained in the powder are gradually crushed and the volume decreases. At this time, the relationship between load (vertical axis) and displacement (horizontal axis) changes linearly. The displacement of the straight line portion and the slope of the load were determined and taken as the deformation coefficient (kgf/mm). The higher the deformation coefficient, the higher the powder strength. A method for measuring the strength of hollow microparticles disclosed in JP-A-2-216028 was used as reference.

(8) Dielectric constant (Dk) and dielectric loss tangent (Df) of resin molded product
The dielectric constant (Dk) and dielectric loss tangent (Df) of a 50 mm x 50 mm x 1 mm plate-shaped resin molded product were measured at 9.4 GHz using a network analyzer (manufactured by Anritsu Corporation, MS46122B) and a coaxial resonator. A comparison was made using the following formula with a resin molded product containing no powder (filler), and evaluation was made using the following criteria.

Reduction rate (%) of dielectric constant (Dk) = (permittivity without powder mixture - dielectric constant with powder mixture) / dielectric constant without powder mixture × 100

◎: Reduction rate of 15% or more ○: Reduction rate of 10% or more and less than 15% △: Reduction rate of 0% or more and less than 10% ×: Reduction rate of less than 0

Reduction rate (%) of dielectric loss tangent (Df) = (dielectric loss tangent without powder mixture - dielectric loss tangent with powder mixture) / dielectric loss tangent without powder mixture 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]
Powder and resin moldings were obtained in the same manner as in Example 1, except that in the particle preparation step, spray drying was performed at an inlet temperature of 400°C and an outlet temperature of 150°C.

[Example 3]
Powder and resin molded products were obtained in the same manner as in Example 2 except that the opening was changed to 32 μm in the wet classification step.

[Comparative example 1]
Powder and resin moldings were obtained in the same manner as in Example 1 except that the opening was changed to 32 μm in the wet classification step. Since the amount of particles with high porosity removed was increased compared to Example 1, the porosity was lowered, and the low dielectric constant effect was reduced in the resin molded product.

[Comparative example 2]
Powder and resin moldings were obtained in the same manner as in Example 2 except that the classification treatment (wet classification step) was not performed. Since it is not classified, the resulting powder contains many suspended particles, and many of the particles have thin outer shells and are easily broken. Therefore, the particles were broken during the manufacturing process of the resin molded product, and the low dielectric constant effect could not be obtained in the resin molded product. Furthermore, as the specific surface area increased due to cracking, the amount of surface silanol groups increased, and the dielectric loss tangent decreased.

[Comparative example 3]
Powder and resin molded products were obtained in the same manner as in Example 2, except that the classification treatment (classification step) was changed to dry classification. In dry classification, particles collide with each other, which tends to cause pseudo-agglomeration due to static electricity. Therefore, the sieving efficiency is poor. Furthermore, if the sieving time is increased in order to ensure the yield, the number of collisions of particles (with each other and with the inner wall of the apparatus, etc.) increases, which causes cracks in the particles and makes them more likely to break. The particles were broken during the manufacturing process of the resin molding, reducing the low dielectric constant effect. Furthermore, the dielectric loss tangent decreased due to damage to the particle surface.

[Comparative example 4]
Powder and resin molded products were obtained in the same manner as in Example 2 except that the opening was changed to 75 μm in the wet classification step. Because the mesh opening of the sieve was large, coarse particles were not removed sufficiently, and the particles were broken during the manufacturing process of the resin molded product, making it impossible to obtain a low dielectric constant effect.

[Comparative example 5]
Powder and resin moldings were obtained in the same manner as in Example 2, except that in the particle preparation step, hot air with an inlet temperature of 250° C. was sprayed and the outlet temperature was 80° C. Granulated particles have a small diameter and a high deformation coefficient, but a low porosity. Therefore, the low dielectric constant effect became small.

[Comparative example 6]
Powder and resin moldings were obtained in the same manner as in Example 2, except that in the particle preparation step, hot air with an inlet temperature of 500°C was sprayed and the outlet temperature was 200°C. Granulated particles have a large diameter and high porosity, but have a low deformation coefficient. As a result, cracks occurred during the manufacturing process of the resin molded product, and the resin composition could not achieve a low dielectric constant effect.

As shown in Table 1, the powder according to the example and the resin molded product containing this powder have a low dielectric constant and a low dielectric loss tangent. Furthermore, the resin composition blended with the powder according to the example can withstand the kneading process and does not crack, and therefore has a low dielectric constant and dielectric loss tangent.

Claims (9)

A powder containing hollow particles having a cavity inside a non-porous outer shell,
The average particle diameter (D50) of the powder is 10.0 μm or more and 20.0 μm or less,
The powder contains 1.0% by volume or less of coarse particles with a particle diameter of more than 45 μm,
When the powder is suspended in water, the suspended particles are 10.0 to 30.0% by mass, the suspended particles are 0 to 4.0% by mass, and the settled particles are 66.0 to 90.0% by mass. powder. The powder according to claim 1, wherein the powder has a deformation coefficient greater than 3000 kgf/mm. The powder according to claim 1 or 2, wherein the powder has a porosity of 30.0% by volume or more and less than 70.0% by volume. The powder according to claim 1, wherein the powder has a specific surface area of 3.0 m ² /g or less. The powder according to claim 2, wherein the powder contains an alkali component amount of 200 ppm or less. A method for producing a resin composition, comprising blending the powder according to claim 1 into 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 neutralizing and removing the alkali contained in the particles with an acid;
a third step of drying the particles;
a fourth step of firing the particles; between the second step and the third step, wet classification is carried out so that the presence of coarse particles with a particle size of 45 μm or more is 1.0% by volume or less; A method for producing powder, comprising a step. 8. The method for producing powder according to claim 7, wherein in the second step, an alkali component contained in the particles is reduced to 200 ppm or less. 9. The method for producing powder according to claim 7, wherein in the classification step, a wet sieve classification process is performed using a sieve with an opening of 50 μm or less.