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

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

Technical Field

[0001] The present invention relates to a powder suitable as a filler for an insulating material of a semiconductor. In particular, it relates to a powder containing hollow particles having a cavity inside a porous outer shell.

Background Art

[0002] In recent years, high speed and large capacity have been progressing in information communication. Therefore, materials used in communication devices are required to have a low dielectric constant (low Dk) and a low dielectric tangent (low Df). For example, printed wiring boards on which semiconductor elements are mounted are required to have an insulating material with a low dielectric constant and a low dielectric tangent. If the dielectric constant of the insulating material is high, dielectric loss occurs, and if the dielectric tangent of the insulating material is high, there is a risk that not only the dielectric loss but also the amount of heat generation increases.

[0003] In order to achieve a lower dielectric constant and a lower dielectric tangent of the insulating material, development of a resin material that is the main component of the insulating material has been carried out.

[0004] In such resin materials, inorganic or organic fillers are blended in order to improve durability (rigidity), heat resistance, etc. As inorganic fillers, it is known to use metal oxides such as silica, boron nitride, alumina, and titania. Also, in order to lower the dielectric constant, it is known to blend hollow particles or silica as a filler (see, for example, Patent Document 1).

[0005] Also, in order to lower the dielectric constant and the dielectric tangent, it is known to use glass microbubble particles (hollow particles) containing silicon, calcium, sodium or potassium, boron, phosphorus, and zinc as a filler (see, for example, Patent Document 2).

[0006] Also, hollow particles having an average hollow 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).

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-057352 [Patent Document 2] WO2015 / 009461 issue [Patent Document 3] WO2007 / 125891 [Overview of the project] [Problems that the invention aims to solve]

[0008] Among the materials used as fillers, silica is superior in terms of low dielectric constant and low dielectric loss tangent. However, with the rapid increase in data capacity and processing speed in data communication, there is a demand for even lower dielectric constant and dielectric loss tangent. However, with the filler described in Patent Document 1, it is difficult to further lower the dielectric constant due to the small particle size. Even if a larger particle size could be achieved, the particle strength would be low.

[0009] Furthermore, the glass microbubble particles described in Patent Document 2 consist of multiple elements and contain a large amount of impurities (especially Na), making it difficult to lower the dielectric loss tangent.

[0010] Furthermore, the hollow particles disclosed in Patent Document 3 have a thin outer shell and high porosity, resulting in insufficient particle strength. Therefore, cracking is likely to occur when kneading with resin, making it difficult to lower the dielectric constant.

[0011] Thus, conventional technology has been unable to achieve a high level of both reduced dielectric constant and dielectric loss tangent, and high particle strength. [Means for solving the problem]

[0012] The inventors have discovered that a powder containing hollow particles that satisfy predetermined conditions and do not contain coarse particles achieves a low dielectric constant and low dielectric loss tangent in insulating materials, while also possessing sufficient strength to withstand the manufacturing process of insulating materials.

[0013] In other words, the powder according to the present invention contains hollow particles having cavities inside a non-porous outer shell, with an average particle diameter (D50) of 10.0 μm or more and 20.0 μm or less, and containing 1.0 volume% or less of particles with a diameter larger than 45 μm. When this powder is suspended in water, the amount of suspended particles is 10.0 to 30.0 mass%, the amount of suspended particles is 0 to 4.0 mass%, and the amount of settled particles is 66.0 to 90.0 mass%.

[0014] Furthermore, the powder manufacturing method according to the present invention comprises, in order, a first step of preparing particles by spray-drying an alkaline silicate aqueous 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, and a fourth step of calcining the particles, with a wet classification step between the second and third steps being provided so that the presence of coarse particles with a particle diameter of 45 μm or more is 1.0 volume% or less. [Effects of the Invention]

[0015] The powder of the present invention achieves low dielectric constant and low dielectric loss tangent in insulating materials, while also possessing sufficient strength to withstand the manufacturing process of insulating materials. Therefore, it is possible to stably manufacture excellent insulating materials. [Modes for carrying out the invention]

[0016] The powder of the present invention contains hollow particles having cavities inside a non-porous outer shell, with an average particle diameter (D50) of 10.0 μm to 20.0 μm, and a content of particles with a diameter greater than 45 μm (hereinafter referred to as coarse particles) of 1.0 volume% or less. When this powder is suspended in water, the amount of suspended particles is 10.0 to 30.0 mass%, suspended particles are 0 to 4.0 mass%, and settled particles are 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 be unintentionally 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 settled particles. It is preferable that 90 mass or more of the particles contained in the powder are hollow particles.

[0017] Here, suspended particles are defined as particles that disperse in water when suspended, and floating particles are defined as lighter particles that float in the upper layer (near the water surface). Such floating particles usually have a high porosity. Therefore, the more floating particles are added to the resin material, the lower the dielectric constant and dielectric loss tangent of the resin product (molded product). Also, generally, particles with a high porosity have a large particle diameter (smaller particle diameters have lower porosity). Floating particles tend to have low particle strength because the ratio of particle diameter (d) to outer shell thickness (t) (t / d) is small. Therefore, there is a risk of particles breaking during the process from mixing the resin material and particles to molding the resin product (i.e., during the manufacturing process). Broken particles hinder the reduction of dielectric constant and dielectric loss tangent, and worsen the fluidity of the resin composition, leading to a decrease in the uniformity of the resin product and the formation of voids inside the resin product. However, by controlling the amount of suspended particles to 10.0-30.0% by mass of the total particles, it is possible to suppress particle fracture while simultaneously reducing the dielectric constant and dielectric loss tangent.

[0018] In other words, by controlling the amount of suspended particles, desirable properties of particles with high porosity (e.g., low dielectric constant and low dielectric loss tangent) can be ensured while undesirable properties of particles with high porosity (e.g., cracking) can be suppressed to an acceptable degree. Suspended particles include small-diameter particles with high porosity, and such particles are less prone to cracking during the manufacturing process compared to large-diameter particles, thus improving the overall particle strength. The content of suspended particles is preferably 12.5 to 25.0 mass%, and more preferably 15.0 to 20.0 mass%. The content of settled particles is preferably 70.0 to 88.0 mass%, and more preferably 75.0 to 85.0 mass%.

[0019] In addition, the average particle size (D50) of the powder is 10.0 μm or more and 20.0 μm or less. This enables both reduction of the dielectric constant and improvement of the particle strength. When granulated by the spray drying method, generally, the smaller the particle size, the lower the porosity tends to be. Therefore, a powder with an average particle size of less than 10.0 μm has a low effect of reducing the dielectric constant. Although there is a method to increase the porosity with a powder of less than 10.0 μm, as the particle size becomes smaller, the outer shell becomes thinner, so that more particles are cracked during particle preparation. It is difficult to remove the cracked particles, and when a powder containing cracked particles is blended into a resin material, it deteriorates the fluidity of the resin composition, reduces the uniformity of the resin molded product, or causes voids inside the resin molded product. On the other hand, when the average particle size exceeds 20.0 μm, the powder contains many large hollow particles. Usually, the larger the hollow particle, the higher the porosity and the lower the particle strength. Therefore, the average particle size is preferably 15.0 μm or less.

[0020] Moreover, the coarse particles (particle size over 45 μm) contained in the powder are 1.0 volume% or less. By making the coarse particles 1.0 volume% or less by wet sieving, it is possible to achieve both suppression of particle cracking and reduction of the dielectric constant and dielectric loss tangent. Generally, it is known that particles (powder) granulated using the spray drying method have a wide particle size distribution. Naturally, the powder contains a considerable amount of large particles. When such a powder is blended into a resin material, since coarse particles with high porosity and low strength occupy a large volume, during the manufacturing process, they are subjected to the force by kneading, and the frequency of generation of cracked particles increases. Therefore, as a result, the desired dielectric properties cannot be obtained. Therefore, as described above, it is necessary to make the coarse particles 1.0 volume% or less by wet sieving. The coarse particles are preferably 0.5 volume% or less, more preferably 0.3 volume% or less, and particularly preferably 0 volume%.

[0021] Even though such powder contains relatively large particles with an average particle diameter of 10.0 μm or more, the deformation coefficient can be increased. Here, the deformation coefficient is determined from the displacement that occurs in the powder when a load is applied. The greater the amount of powder containing many particles with high particle strength, the greater the deformation coefficient. By removing coarse particles that are prone to cracking and controlling the amount of floating particles, the deformation coefficient can be increased. The deformation coefficient of the powder is preferably greater than 3000 kgf / mm. When the deformation coefficient is 3000 kgf / mm or less, it cannot withstand kneading in the manufacturing process, particle cracking occurs, and the desired dielectric properties cannot be obtained.

[0022] 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 lower dielectric constant and a lower dielectric tangent, and at the same time, the particle strength can be maintained above a predetermined level to effectively suppress particle cracking. The porosity is more preferably 40.0% by volume or more, and even more preferably 50.0% by volume or more. On the other hand, it is more preferably 65.0% by volume or less, and even more preferably 55.0% by volume or less.

[0023] Also, the specific surface area of the powder is preferably 3.0 m 2 / g or less. The larger the specific surface area, the easier it is for particles to aggregate in the resin composition. Therefore, the fluidity decreases, affecting the moldability.

[0024] Here, the particles constituting the powder are preferably silica-based particles mainly composed of silica. 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 silica content 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 consisting substantially of only silica.

[0025] [Resin Composition] A resin composition is prepared by blending the aforementioned powders with resin materials. Such a resin composition can be used as an insulating material for electronic materials such as semiconductors, specifically for copper-clad laminates, prepregs, and build-up films for forming printed circuit boards (including rigid and flexible substrates). It can also be used for semiconductor packaging-related materials such as mold resins, mold underfills, and underfills, as well as adhesives for flexible substrates.

[0026] As the resin, curable resins commonly used in electronic materials such as semiconductors can be used. Photocurable resins are also acceptable, but thermosetting resins are preferred. Examples of curable resins include epoxy resins, polyphenylene ether resins, fluorine resins, polyimide resins, bismaleimide resins, acrylic resins, methacrylic resins, silicone resins, BT resins, cyanate resins, etc. Examples of epoxy resins include bisphenol-type epoxy resins, novolac-type epoxy resins, triphenolalkane-type epoxy resins, epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, dicyclopentadienephenol novolac resins, phenol aralkyl-type epoxy resins, glycidyl ester-type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, halogenated epoxy resins, etc. These resins may be used individually or in mixtures of two or more types.

[0027] The resin composition preferably contains powder A and curable resin B in a mass ratio (A / B) of 10 / 100 to 95 / 100. This allows the resin composition to fully exhibit its function as a filler while maintaining its properties such as fluidity. A mass ratio (A / B) of 30 / 100 to 80 / 100 is more preferable.

[0028] 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, examples of curing agents include phenol resins having two or more phenolic hydroxyl groups in one molecule (bisphenol-type resins, novolac resins, triphenolalkane-type resins, resol-type phenol resins, phenol aralkyl resins, biphenyl-type phenol resins, naphthalene-type phenol resins, cyclopentadiene-type phenol resins, etc.) and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methylnadic anhydride. Various additives such as colorants, stress relievers, defoamers, leveling agents, coupling agents, flame retardants, and curing accelerators may be added to the resin composition as needed.

[0029] The resin composition can be manufactured using conventionally known methods. For example, a thermosetting resin, powder, curing agent, additives, etc., can be mixed and kneaded using a roll mill or the like. The resulting resin composition can then be applied to a substrate and cured by heat, ultraviolet light, or the like.

[0030] [Method for producing powder] The present invention provides a method for producing powder, comprising: a particle preparation step of preparing particles by spray-drying an alkaline silicate aqueous solution in a hot air stream; an alkali removal step of neutralizing and removing the alkali contained in the prepared particles with an acid; a drying step of drying the alkali-removed particles; and a calcination step of calcining the particles. Between the alkali removal step and the drying step, there is a wet classification step of wet classification such that the presence of coarse particles with a particle diameter of 45 μm or more is 1.0 volume% or less.

[0031] The aforementioned powder can be obtained through this process.

[0032] Generally, when producing particles by firing, it is considered preferable to perform classification in the final stage after firing to standardize the particle size. However, here we deliberately perform it before firing. If the firing process is carried out without classification, coarse particles that should be removed will remain during firing. Coarse particles have a high porosity and tend to crack easily. Therefore, they may crack due to the stress of shrinkage caused by heating. The fragments generated by cracking are dense silica with no voids, which hinders the reduction of dielectric constant and dielectric loss tangent. By performing classification before firing, these problems can be avoided. As a result, the reduction of dielectric constant and dielectric loss tangent of the particles is more reliably achieved, and particles that can handle high-speed data communication can be obtained. The following describes each process in detail.

[0033] (Particle preparation process) In this process, an alkaline silicate aqueous solution is spray-dried in a hot air stream to granulate particles. While this process is performed to obtain hollow particles, it is difficult to produce only hollow particles, and the granulated particles may consequently contain solid particles. In this case, the powder obtained through the subsequent process will also contain solid particles. However, if the powder possesses the aforementioned properties, the desired effect can be achieved even if solid particles are present.

[0034] The molar ratio of SiO2 to M2O (where M is an alkali metal) in alkali silicate (SiO2 / M2O) is preferably 1 to 5, and more preferably 2 to 4. If this molar ratio is less than 1, the amount of alkali is too high, making it difficult to remove it sufficiently even with acid washing in the alkali removal process described later. Furthermore, the deliquescent properties of the spray-dried product increase, making it difficult to obtain the desired hollow particles. If 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, it may not be possible to granulate hollow particles by spray drying.

[0035] The concentration of SiO2 in the alkali silicate aqueous solution is preferably 1 to 30% by mass, and more preferably 5 to 28% by mass. Although production is possible at concentrations below 1% by mass, productivity is significantly reduced. If the concentration exceeds 30% by mass, the stability of the alkali silicate aqueous solution decreases significantly, resulting in high viscosity, and spray drying may not be possible. Even if spray drying is possible, the particle size distribution, outer shell thickness, etc., become extremely non-uniform, which may limit the applications of the resulting particles. Examples of alkali silicate include water-soluble sodium silicate and potassium silicate. Sodium silicate is preferred.

[0036] Conventional known methods such as the rotating disk method, the pressurized nozzle method, and the two-fluid nozzle method can be used as spray drying methods. In this case, the two-fluid nozzle method is preferred.

[0037] In spray drying, the inlet temperature of the spray dryer is preferably 300 to 600°C, and more preferably 350 to 550°C. The outlet temperature is preferably 120 to 300°C, and more preferably 130 to 250°C. With these temperature settings, hollow particles can be obtained stably.

[0038] (Alkali removal process) Next, the alkali contained in the particles granulated in the particle preparation process is neutralized and removed with acid. Immersion of the particles in an acid solution is preferred. At this time, the molar ratio (Ma / Msp) of the number of moles of M2O (Msp) to the number of moles of acid (Ma) in the particles is preferably 0.6 to 4.7, and more preferably 1 to 4.5. If this molar ratio is less than 0.6, the amount of acid is too small relative to the M2O. Therefore, the silica skeletalization of silicic acid, which is thought to occur along with alkali removal, does not proceed, and the particles may partially dissolve, or the dissolved alkali silicate may gel. Even if the molar ratio exceeds 4.7, further silica skeletalization does not proceed, and the acid is excessive and uneconomical.

[0039] Furthermore, it is preferable to immerse the particles in an acidic aqueous solution so that the particle concentration is 1 to 30% by mass as SiO2. If the concentration is less than 1% by mass, there are no problems with alkali removal or cleaning performance, but the manufacturing efficiency will decrease. If the concentration exceeds 30% by mass, the concentration may be too high, and alkali removal and cleaning efficiency may decrease. 5 to 25% by mass is even more preferable.

[0040] The conditions for immersion in the acidic aqueous solution are not particularly limited as long as the alkali can be removed to the desired level. Typically, 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 conventionally known methods. For example, filtration washing with pure water is performed. The above acid treatment and washing may be repeated as needed.

[0041] The residual amount (mass percentage) 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 alkali in this step, particle adhesion in subsequent steps is prevented, and the generation of sintered particles in the firing step can be prevented. Furthermore, the residual amount (content) of alkali is known to affect dielectric properties. By sufficiently removing alkali in this step, even when using an aqueous alkali silicate solution as the raw material, particles with low dielectric constant and low dielectric loss tangent can be obtained.

[0042] Furthermore, the alkali content of the final product (the particles constituting the powder) is preferably within the range described above, and is usually equivalent to the alkali content after the alkali removal process.

[0043] The amount of residual alkali can be measured using an atomic absorption spectrophotometer with a sample prepared by dissolving the powder in acid. If sodium silicate is used, Na is measured; if potassium silicate is used, K is measured. Specific details will be explained in the examples.

[0044] Examples of acids used in this process include mineral acids (hydrochloric acid, nitric acid, sulfuric acid, etc.) and organic acids (acetic acid, tartaric acid, malic acid, etc.). Mineral acids are preferred, and sulfuric acid with a high valency is particularly preferred.

[0045] (Classification process) Coarse particles are removed by performing a classification process between the alkali removal process and the drying process described later. In this classification process, particle size classification is performed to separate the powder according to its particle size, with the aim of standardizing the particle size of the powder. Particle size classification operations can be broadly classified into sieving and fluid classification. It is preferable to use sieving, which is not affected by the porosity of the particles and has high production efficiency. In sieving, classification is performed using the openings of the sieve mesh. In this invention, wet sieving is used to reduce damage to the particle surface while maintaining high particle dispersibility.

[0046] In this process, a sieve with an appropriate mesh size (number of meshes) is used to remove particles that are large in size and prone to breaking during the manufacturing process. To reduce the amount of coarse particles in the powder to 1.0 volume% or less, it is preferable to use a sieve with a mesh size of 300 or more.

[0047] Furthermore, the classification process allows for the control of the suspended particle content to 10.0-30.0% by mass and the settled particle content to 66.0-90.0% by mass.

[0048] (drying process) Next, the classified particles are subjected to a drying treatment. This may be done multiple times if necessary. However, since this increases the number of steps and reduces productivity, a single drying treatment is preferred during the manufacturing process. Heat drying is suitable as the drying treatment. The drying temperature is preferably 50 to 400°C, and more preferably 50 to 200°C. Specifically, methods include drying at a low temperature of around 50 to 200°C over a long period of time, drying by gradually increasing the temperature, or drying by changing the temperature in several stages.

[0049] (Firing process) Next, the dried particles are fired. The firing temperature is preferably 600 to 1200°C, and more preferably 900 to 1100°C. If the firing temperature is below 600°C, a large amount of SiOH groups remain, and the dielectric loss tangent of the particles becomes high. Therefore, even when incorporated into a resin material, it is difficult to obtain a dielectric loss tangent reduction effect. If the firing temperature exceeds 1200°C, the particles sinter easily, so irregularly shaped particles and coarse particles are likely to be generated.

[0050] Furthermore, it is preferable to include a crushing step between the drying and firing steps. Even if the particles have aggregated during the drying step, they can be separated into individual particles. This prevents the particles from sintering together.

[0051] As a crushing device, known ball mills, bead mills, and hammer mills can be used. To prevent cracking of the powder due to mechanical load during the process, a continuous pin mill that can crush the powder in a short time using minimal impact force is suitable.

[0052] Furthermore, it is preferable to include a step of sieving out particle clumps after the firing process. Note that particle clumps refer to large particles, such as those with a particle size exceeding 150 μm. In this step, a sieve with an appropriate mesh size (mesh count) that can remove particle clumps is used. For example, a sieve with a mesh size of 150 μm is used.

[0053] The following describes specific embodiments of the present invention.

[0054] [Example 1] 30,000 g of a water glass aqueous solution (SiO2 / Na2O molar ratio 3.2, SiO2 concentration 24.0 mass%) was used to granulate hollow particles by spraying hot air at an inlet temperature of 350°C into one of two fluid nozzles at a flow rate of 0.62 kg / hr and into the other nozzle at a flow rate of 15,900 L / hr (air / liquid volume ratio 31,800). The outlet temperature was 130°C (particle preparation process). At this time, a small amount of solid particles may also be granulated, but it is not necessary to remove the solid particles before proceeding to the next process.

[0055] Next, 5000g of these hollow particles (i.e., the particles granulated in the first step) were immersed in 32000g of a 10% by mass sulfuric acid aqueous solution and stirred for 15 hours. At this time, the solid content (SiO2) concentration was 10.2% by mass, and the ratio of moles of acid (Ma) to moles of alkali (Na2O) (Msp) (Ma / Msp) was 3.5. After stirring, the temperature of the dispersion was 35°C and the pH was 3.0. After the immersion treatment, the mixture was filtered and washed with pure water to obtain a cake product (alkali removal step).

[0056] Next, the solid content of the cake after washing was measured, and based on that value, pure water was added to create a dispersion with a concentration of 10% by weight. Then, in order to remove coarse particles, this dispersion was passed through a vibrating sieve with a mesh size of 45 μm, and the particles that passed through the sieve were collected (wet classification process).

[0057] These particles were heat-treated at 1000°C for 10 hours (calcination process). This resulted in a powder containing hollow particles.

[0058] This powder was blended with the liquid epoxy resin "ZX-1059 manufactured by Nippon Steel Chemical & Material Co., Ltd." together with the liquid acid anhydride "Ricacid MH700 manufactured by Shin Nippon Rika Co., Ltd." and the imidazole-based epoxy resin curing agent "2PHZ-PW manufactured by Shikoku Kasei Co., Ltd.". Here, "ZX-1059" was added in a ratio of 100 parts by mass, "Ricacid MH700" in a ratio of 86 parts by mass, and "2PHZ-PW" in a ratio of 1 part by mass, so that the proportion of powder in the blend (paste) was 35% by volume. This blend was pre-mixed in a planetary mill and then kneaded with a three-roll mill to obtain a paste (resin composition). This paste was heated at 170°C for 2 hours to cure, and a plate-shaped resin molded product (resin product) measuring 50 mm × 50 mm × 1 mm was obtained.

[0059] The physical properties of the powder and resin molded products obtained as described above were measured and evaluated as follows. The results, along with the preparation conditions, are shown in Table 1. The same procedure was followed for other examples and comparative examples.

[0060] (1) Average particle diameter (D50), amount of coarse particles Powder 1.0 cm 3A sample was taken, and the particle size distribution of the powder was measured dry using a particle size analyzer (Seishin Corporation Laser Micron Sizer LMS-3000). From the measurement results, the average particle diameter (D50) was obtained. Furthermore, by analyzing this particle size distribution, the volume ratio of coarse particles with a particle diameter greater than 45 μm was calculated and expressed as the amount of coarse particles (volume %).

[0061] (2) Specific surface area (SA) After allowing the powder to stand for 1 hour in a 300°C environment, the specific surface area was measured using the BET method (single-point method) with a fully automatic specific surface area analyzer (Macsorb, manufactured by Mountec). Here, the measurement method was followed in accordance with the Japanese Industrial Standard JIS Z8830.

[0062] (3)Residual amount of Na The powder was pre-treated with sulfuric acid and hydrofluoric acid, then dissolved in hydrochloric acid, and the amount of Na was measured by atomic absorption spectrometry using an atomic absorption spectrophotometer (Hitachi Z-2310).

[0063] (4) Particle density, porosity 20.0cm 3 A random sample of powder was taken, and the average particle density was measured using the gas pycnometer method with a Quantachrome Instruments Ultrapyc5000. Nitrogen gas was used as the gas. The particle density was measured according to the measurement method specified in Japanese Industrial Standard JIS Z8807.

[0064] From this particle density, the porosity (%) was calculated using the formula "[2.2 - (particle density)] / 2.2 × 100". Assuming the powder is composed of silica particles, this formula uses the silica density of 2.2 g / cm³. 3 I used it.

[0065] (5) Dielectric constant (Dk) and dielectric loss tangent (Df) of powder The dielectric constant (Dk) and dielectric loss tangent (Df) were measured using the cavity resonator perturbation method with a network analyzer (Anritsu MS46122B) and a cavity resonator (1 GHz). The measurements were performed in accordance with ASTMD2520 (JIS C2565).

[0066] (6) The proportion of suspended particles, suspended particles, and settled particles when suspended in water. First, the powder and water were mixed to a concentration of 5.0% by mass, and then subjected to ultrasonic treatment for 10 minutes. The resulting dispersion was allowed to stand at 25°C for 24 hours, after which the suspended particles, suspended particles, and settled particles were collected separately. Each of the collected particles was dried at 105°C for 24 hours, weighed, and its proportion was calculated.

[0067] (7) Deformation modulus Powder and glycerin were mixed and dispersed in a weight ratio of 2:1. This mixture was filled into a specified mold (25 mm in diameter, 64 mm in height). After filling, the mold was placed in a press machine (manufactured by NPA Systems Co., Ltd.) and a load was applied in stages. The load (kgf) and vertical displacement (mm) were plotted. As the load increased, the particles contained in the powder were gradually crushed and the volume decreased. At this time, the relationship between load (vertical axis) and displacement (horizontal axis) changed linearly. The slope of the load and displacement in the linear portion was determined and used as the deformation coefficient (kgf / mm). A higher deformation coefficient indicates higher powder strength. The method for measuring the strength of hollow fine particles disclosed in Japanese Patent Publication No. 2-216028 was used as a reference.

[0068] (8) Dielectric constant (Dk) and dielectric loss tangent (Df) of resin molded products The dielectric constant (Dk) and dielectric loss tangent (Df) of a 50mm x 50mm x 1mm plate-shaped resin molded material were measured at 9.4GHz using a network analyzer (Anritsu MS46122B) and a coaxial resonator. The measured values ​​were compared with those of a resin molded material without powder (filler) using the following formula, and evaluated according to the following criteria.

[0069] The reduction rate (%) of the dielectric constant (Dk) = (dielectric constant without powder - dielectric constant with powder) / dielectric constant without powder × 100

[0070] ◎: Reduction rate of 15% or more ○: Reduction rate of 10% or more but less than 15% △: Reduction rate 0% or more but less than 10% ×: Reduction rate less than 0

[0071] The reduction rate (%) of the dielectric loss tangent (Df) = (dielectric loss tangent without powder - dielectric loss tangent with powder) / dielectric loss tangent without powder × 100

[0072] ◎: Reduction rate of 50% or more ○: Reduction rate of 30% or more but less than 50% △: Reduction rate of 20% or more but less than 30% ×: Reduction rate less than 20%

[0073] [Example 2] Powder and resin molded products were obtained in the same manner as in Example 1, except that the particle preparation step involved spray drying at an inlet temperature of 400°C and an outlet temperature of 150°C.

[0074] [Example 3] Powder and resin molded products were obtained in the same manner as in Example 2, except that the mesh opening was changed to 32 μm in the wet classification process.

[0075] [Comparative Example 1] Powder and resin molded products were obtained in the same manner as in Example 1, except that the mesh opening was changed to 32 μm in the wet classification process. Since the amount of particles with high porosity removed increased compared to Example 1, the porosity decreased, and the low dielectric constant effect in the resin molded product became smaller.

[0076] [Comparative Example 2] Powder and resin molded products were obtained in the same manner as in Example 2, except that a classification process (wet classification process) was not performed. Because the powder was not classified, the obtained powder contained many suspended particles and many particles with thin outer shells that were easily broken. As a result, the particles broke during the manufacturing process of the resin molded products, and the low dielectric constant effect could not be obtained in the resin molded products. In addition, the amount of surface silanol groups increased along with the increase in specific surface area due to cracking, and the dielectric loss tangent decreased.

[0077] [Comparative Example 3] Powder and resin molded products were obtained in the same manner as in Example 2, except that the classification process (classification step) was changed to dry classification. In dry classification, particles collide with each other, and pseudo-aggregation due to static electricity is likely to occur. Therefore, the sieving efficiency is poor. In addition, if the sieving time is increased in order to ensure the yield, the number of particle collisions (with each other and with the inner wall of the apparatus, etc.) increases, causing cracks in the particles and making them brittle. In the manufacturing process of the resin molded products, the particles cracked, and the low dielectric constant effect was reduced. Furthermore, the dielectric loss tangent decreased due to damage to the particle surface.

[0078] [Comparative Example 4] Powder and resin molded products were obtained in the same manner as in Example 2, except that the mesh size was changed to 75 μm in the wet classification process. Because the mesh size of the sieve was large, coarse particles were not sufficiently removed, and the particles broke during the manufacturing process of the resin molded products, so the low dielectric constant effect could not be obtained.

[0079] [Comparative Example 5] In the particle preparation process, powder and resin molded products were obtained in the same manner as in Example 2, except that the mixture was sprayed into hot air at an inlet temperature of 250°C and the outlet temperature was set to 80°C. The granulated particles had a small diameter and a high deformation modulus, but a low porosity. As a result, the low dielectric constant effect was reduced.

[0080] [Comparative Example 6] In the particle preparation process, powder and resin molded products were obtained in the same manner as in Example 2, except that the particles were sprayed into hot air at an inlet temperature of 500°C and the outlet temperature was set to 200°C. The granulated particles had a large diameter and high porosity, but a low deformation modulus. As a result, cracking occurred during the manufacturing process of the resin molded products, and the low dielectric constant effect was not obtained in the resin composition.

[0081] [Table 1]

[0082] As shown in Table 1, the powders according to the examples and the resin molded products containing these powders have low dielectric constants and dielectric loss tangents. Furthermore, the resin compositions containing the powders according to the examples have low dielectric constants and dielectric loss tangents because they withstand the kneading process and do not crack.

Claims

1. A powder containing hollow particles having a cavity inside a non-porous outer shell, The hollow particles are silica-based particles, with silica as the main component. The average particle size (D50) of the aforementioned powder is 10.0 μm or more and 20.0 μm or less. The aforementioned powder contains coarse particles with a particle size larger than 45 μm in 1.0 volume percent or less. The powder, when suspended in water, contains 10.0 to 30.0% by mass of suspended particles, 0 to 4.0% by mass of suspended particles, and 66.0 to 90.0% by mass of settled particles.

2. The powder according to claim 1, characterized in that the deformation coefficient of the powder is greater than 3,000 kgf / mm.

3. The powder according to claim 1 or 2, wherein the porosity of the powder is 30.0% by volume or more and less than 70.0% by volume.

4. The specific surface area of ​​the aforementioned powder is 3.0 m². ２ The powder according to claim 1, which is less than or equal to / g.

5. The powder according to claim 2, characterized in that the powder contains an alkaline component amount of 200 ppm or less.

6. A method for producing a resin composition, characterized by incorporating the powder described in claim 1 into a resin material.

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