Hollow granules, methods for manufacturing the same, and resin compositions thereof

Abstract

This invention relates to hollow particles with an internal cavity and a non-porous shell. The average particle size (D50) is 0.1 μm to 10 μm; when suspended in water, the floating particles account for 0.5% to 7.0% by mass, the suspended particles for 0 to 4.0% by mass, and the settled particles for 89.0% to 99.5% by mass. Insulating materials with such hollow particles can achieve low dielectric constant and low dielectric loss tangent.

Description

Technical Field

[0001] This invention relates to hollow particles used as fillers in insulating materials. Prior Technology

[0002] In recent years, information and communication technologies have been developing towards high speed and large capacity. Therefore, materials used in communication equipment require low dielectric constant (low Dk) and low dielectric loss tangent (low Df). For example, printed circuit boards (PCBs) for mounting semiconductor components require insulating materials with low dielectric constant and low dielectric loss tangent. If the dielectric constant of the insulating material is high, dielectric loss will occur. Furthermore, if the dielectric loss tangent of the insulating material is high, it will not only cause dielectric loss but may also lead to increased heat generation.

[0003] To achieve low dielectric constant and low dielectric loss tangent in insulating materials, resin materials are being developed as the main body of insulating materials. Epoxy resins, polyphenylene ether resins, and fluorinated resins have been proposed as such resin materials (see, for example, Patent Documents 1 to 5).

[0004] For such resin materials, fillers are added to improve durability (rigidity) and heat resistance, etc. As fillers, metal oxides such as silicon dioxide, boron nitride, talc, kaolin, clay, mica, alumina, zirconium oxide, and titanium dioxide are known to be used (see, for example, Patent Document 3).

[0005] Patent documents [Patent Document 1] No. WO2009 / 041137 [Patent Document 2] Japanese Patent Publication No. 2006-516297 [Patent Document 3] Japanese Patent Application Publication No. 2017-057352 [Patent Document 4] Japanese Patent Application Publication No. 2001-288227 [Patent Document 5] Japanese Patent Application Publication No. 2019-172962 Summary of the Invention

[0006] Among materials used as fillers, silicon dioxide excels in low dielectric constant and low dielectric loss tangent. However, due to the rapid development of high-speed and high-capacity data communication, there is a further demand for lower dielectric constant and lower dielectric loss tangent.

[0007] The inventors of this invention have discovered that hollow particles that do not contain coarse particles and meet specified conditions can achieve a low dielectric constant and a low dielectric loss tangent in insulating materials. Furthermore, it has been found that such hollow particles do not impede the filterability and injectability of the liquid used to form the insulating material during the manufacturing process of the insulating resin.

[0008] That is, the present invention relates to hollow particles having cavities inside a non-porous shell. The average particle size (D50) of the hollow particles is 0.1 μm to 10 μm; when the hollow particles are suspended in water, the floating (floating) particles are 0.5% to 7.0% by mass, the suspended (turbid) particles are 0 to 4.0% by mass, and the settling (settling) particles are 89.0% to 99.5% by mass.

[0009] Furthermore, the method for manufacturing hollow particles according to the present invention includes the following steps: a hollow particle preparation step, in which hollow particles are prepared by spray drying a silica-alkali aqueous solution in a hot air stream; an alkali removal step, in which the alkali contained in the prepared hollow particles is neutralized and removed by acid; a firing step, in which the hollow particles after alkali removal are fired; and a grading step, in which the hollow particles are graded between the hollow particle preparation step and the firing step to remove coarse particles.

[0010] The hollow particles of this invention enable the insulation material to achieve a low dielectric constant and a low dielectric loss tangent, thereby achieving high semiconductor transmission speeds and reduced transmission losses. Furthermore, the hollow particles of this invention do not impede the filterability and injectability of the liquid used to form the insulation material during the manufacturing process. Therefore, excellent insulation materials can be stably manufactured. Simple Explanation of the Diagram

[0011] none. Implementation

[0012] [Hollow Granules]

[0013] The hollow particles of the present invention have cavities inside a non-porous shell, with an average particle size of 0.1 μm to 10 μm. When the hollow particles are suspended in water, the floating particles account for 0.5% to 7.0% by mass, the suspended particles account for 0 to 4.0% by mass, and the settling particles account for 89.0% to 99.5% by mass.

[0014] In this document, the hollow particles of the present invention are suitable for silica-based hollow particles with silica as the main component. Therefore, in addition to silica, the hollow particles (shell) may also contain inorganic oxides such as alumina, zirconium oxide, and titanium dioxide. The silica content in the particles is preferably 70% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably substantially composed of only silica.

[0015] The hollow particles of the present invention contain lightweight floating particles that float when suspended in water. Typically, these floating particles have high porosity; therefore, adding them to a resin composition results in a low dielectric constant and a low dielectric loss tangent. Furthermore, since hollow particles with high porosity generally have large particle sizes, controlling the amount of these floating particles to 0.5% to 7.0% of the total particle mass will control (reduce) the amount of coarse particles. This improves the filterability and injectability of the liquid used to form the resin composition during the manufacturing process of resin compositions such as insulating materials, and enhances the surface smoothness after molding. In this case, the content of coarse particles with a particle size greater than 8.0 μm is preferably 10% by volume or less, more preferably 5% by volume or less, and even more preferably 1% by volume or less.

[0016] Furthermore, due to the small ratio of the shell thickness to the particle size of the floating particles, the particles tend to have lower strength. Consequently, the particles may break during the manufacture of resin compositions such as insulating materials. These broken particles not only hinder the reduction of the dielectric constant and dielectric loss tangent, but also worsen the flowability of the liquid used to form the resin composition. In other words, broken particles are a major cause of reduced uniformity in the resin composition (molded article) and the formation of porosity within the resin composition. Particle breakage can be suppressed by controlling the amount of floating particles.

[0017] This invention controls the amount of floating particles, thus ensuring the preferred characteristics of high-porosity particles (especially low dielectric constant and low dielectric loss tangent) while suppressing their undesirable characteristics (especially breakage) to a non-problematic level. Furthermore, the floating particles include those with high porosity even with small diameters; these particles are less prone to breakage during manufacturing compared to large-diameter particles, thus significantly suppressing the undesirable characteristics of high-porosity particles overall.

[0018] The content of floating particles is preferably 1.0% to 5.0% by mass, more preferably 1.0% to 4.0% by mass, and even more preferably 2.0% to 4.0% by mass. In addition, the content of settling particles is preferably 91.0% to 99.5% by mass, more preferably 92.0% to 99.0% by mass, and even more preferably 95.0% to 98.0% by mass.

[0019] The proportions of floating, suspended, and settled particles when suspended in water are calculated by recovering and measuring each type of particle from the suspension. This is explained in detail in the embodiments.

[0020] Furthermore, the average particle size (D50) of the hollow particles of the present invention is in the range of 0.1 μm to 10 μm. Particles with an average particle size less than 0.1 μm are difficult to manufacture using spray drying. Furthermore, particles with an average particle size greater than 10 μm are unsuitable for semiconductor-related products. Therefore, the average particle size is preferably 0.5 μm to 10 μm, and more preferably 1.0 μm to 5.0 μm.

[0021] Furthermore, the maximum particle size (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 than the average particle size (D50), more preferably 8 times or less; usually more than 2 times, and may be greater than 5 times as long as the requirements of the present invention are met.

[0022] The average particle size (D50), maximum particle size (D100), and coarse particle content were measured using laser diffraction-scattering method. Specific details are provided in the examples.

[0023] The porosity of the hollow particles of the present invention is preferably 5% by volume or more, more preferably 8% by volume or more, and even more preferably 10% by volume or more. The upper limit is preferably 50% by volume or less, more preferably 35% by volume or less, even more preferably 25% by volume or less, and most preferably 20% by volume or less. With such a porosity, a reduction in dielectric constant and dielectric loss tangent can be achieved. Furthermore, particle breakage can be effectively suppressed while maintaining a particle strength above a specified level. In this document, the porosity is calculated from the particle density. Specific details are explained in the embodiments.

[0024] The hollow particles of the present invention are preferably used as fillers in insulating materials for electronic materials such as semiconductors. Specifically, they can be added to copper-clad laminates, prepregs, and building films used to form printed wiring boards (including rigid and flexible substrates). Furthermore, they can be added to semiconductor packaging-related materials such as molding resins, molding underfills, and underfill adhesives, as well as adhesives for flexible substrates.

[0025] [Resin Composition]

[0026] A resin composition can be prepared by adding the aforementioned hollow particles and resin. Such a resin composition can be used for applications involving the aforementioned hollow particles, such as insulating materials for electronic components like semiconductors.

[0027] As the resin, curable resins commonly used in electronic components such as semiconductors can be used. Photocurable resins are also possible, but thermocurable resins are preferred. Examples of such curable resins include epoxy resins, polyphenylene ether resins, fluorinated resins, polyimide resins, bismaleimide resins, acrylic resins, methacrylic resins, silicone resins, BT resins, and cyanate resins. Specific examples of epoxy resins include bisphenol-type epoxy resins, phenolic varnish-type epoxy resins, triphenolmethane-type epoxy resins, epoxy resins with a biphenyl backbone, epoxy resins with a naphthalene backbone, dicyclopentadiene phenolic varnish-type epoxy resins, phenol aralkyl-type epoxy resins, glycidyl ester-type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and halogenated epoxy resins. These resins can be used alone or in mixtures of two or more.

[0028] In the resin composition (the liquid used to form the resin composition), hollow particles A and curable resin B are preferably contained in a mass ratio (A / B) of 10 / 100 to 95 / 100. With such a mass ratio, the properties of the liquid used to form the resin composition, such as fluidity, can be maintained while fully utilizing its function as a filler. This mass ratio (A / B) is more preferably 30 / 100 to 80 / 100.

[0029] The resin composition (the liquid used to form the resin composition) preferably contains curing agents such as phenolic compounds, amine compounds, and acid anhydrides. When using epoxy resin as the curing resin, examples of curing agents include resins having two or more phenolic hydroxyl groups per molecule (bisphenol type resins, phenolic varnish type resins, triphenolmethane type resins, methyl phenolic resins, phenolic aralkyl resins, biphenyl type phenolic resins, naphthyl type phenolic resins, cyclopentadiene type phenolic resins, etc.) and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methyl northoenedic acid.

[0030] Various additives (colorants, stress relievers, defoamers, leveling agents, coupling agents, flame retardants, curing accelerators, etc.) may be added to the resin composition (the liquid used to form the resin composition) as needed.

[0031] The resin composition of the present invention can be obtained by conventionally known methods. For example, a coating liquid (a liquid used to form the resin composition) can be prepared by mixing thermosetting resin, hollow particles, curing agent, additives, etc., using a roller mill or the like, and then coated onto a substrate and cured by heat, ultraviolet light, etc.

[0032] [Manufacturing method of hollow pellets]

[0033] The method for manufacturing hollow particles according to the present invention includes the following steps: a hollow particle preparation step, in which hollow particles are prepared by spray drying a silica-alkali aqueous solution in a hot air stream; an alkali removal step, in which the alkali contained in the prepared hollow particles is neutralized and removed by acid; a firing step, in which the alkali-removed hollow particles are fired; and a grading step, in which the hollow particles are graded between the hollow particle preparation step and the firing step to remove coarse particles. Alternatively, other steps such as a drying step may be included between these steps.

[0034] For example, the hollow particles described above can be manufactured using such a manufacturing method.

[0035] When grading is performed during the manufacturing of fired particles, it is generally considered preferable to perform this process in the final stage after firing in order to adjust the final particle size. However, in the manufacturing method of the present invention, grading is specifically performed before the firing process. If the firing process is performed without grading, coarse particles with high porosity that should be removed will exist. Since such coarse particles are prone to breakage, they may break due to shrinkage stress caused by heating. Moreover, since the fragments produced by the breakage are small in size, they cannot be removed even if a grading process is performed later. Furthermore, since these fragments are porous and dense silicon dioxide, they hinder the reduction of dielectric constant and dielectric loss tangent. By performing grading before firing, such disadvantages can be avoided, and the reduction of dielectric constant and dielectric loss tangent of the manufactured particles can be reliably achieved, resulting in particles that correspond to the high-speed data communication requirements.

[0036] The following details each process.

[0037] (Hollow Particle Preparation Process)

[0038] In this process, hollow particles are prepared by spray drying of an aqueous silicate solution in a hot air stream.

[0039] The molar ratio (SiO₂ / M₂O) of the silica base to SiO₂ and M₂O (where M is an alkali metal) is preferably 1 to 5, more preferably 2 to 4. When the molar ratio is less than 1, the excessive amount of alkali makes acid washing during alkali removal difficult, and the increased deliquescence of the spray-dried product makes it difficult to obtain the desired hollow particles. When the molar ratio is greater than 5, the solubility of the silica base decreases, making it difficult to prepare an aqueous solution. Even if an aqueous solution is prepared, there are cases where the desired hollow particles cannot be obtained during spray drying.

[0040] The concentration of SiO₂ in the silica base aqueous solution is preferably 1% to 30% by mass, more preferably 5% to 28% by mass. Even if it is less than 1% by mass, it can still be manufactured, but productivity is significantly reduced. If it is greater than 30% by mass, the stability of the silica base aqueous solution will significantly decrease, becoming highly viscous, and sometimes spray drying is not possible. Even if spray drying is possible, the particle size distribution and shell thickness become extremely uneven, limiting the applications of the obtained particles. Sodium silicate or potassium silicate, which are soluble in water, can be used as the silica base; sodium silicate is preferred.

[0041] As a spray drying method, conventionally known methods such as the rotary disc method, the pressurized nozzle method, and the two-fluid nozzle method can be employed. In this paper, the two-fluid nozzle method is suitable.

[0042] In spray drying, the inlet temperature of the spray dryer is preferably 300℃~600℃, more preferably 350℃~550℃. Furthermore, the outlet temperature is preferably 120℃~300℃, more preferably 130℃~250℃. By setting the inlet and outlet temperatures within the above ranges, hollow particles can be stably obtained.

[0043] (Alkali removal process)

[0044] In this process, the alkali contained in the prepared hollow particles is removed. Neutralization with acid is a suitable method for removal.

[0045] As acids, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid can be used; organic acids such as acetic acid, tartaric acid, and malic acid can also be used. Among these, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid are suitable, but from the viewpoint of valence, sulfuric acid is particularly preferred.

[0046] In this process, it is preferable to immerse the prepared hollow particles in an acidic solution for treatment.

[0047] When hollow particles are immersed in an aqueous acid solution, the molar ratio (Ma / Msp) of the molar number of M₂O (Msp) in the hollow particles to the molar number of acid (Ma) is preferably 0.6 to 4.7, more preferably 1 to 4.5. When this molar ratio is less than 0.6, the amount of acid is too small relative to M₂O, so the silica skeletalization of silicic acid, which is thought to occur simultaneously with the removal of alkali, will not occur, and the hollow particles will partially dissolve, sometimes resulting in gelation of the dissolved silicic acid alkali. Even if the molar ratio is greater than 4.7, silica skeletalization will not proceed further, and excess acid is not economical.

[0048] Furthermore, it is preferable to immerse the hollow particles in an acidic aqueous solution with a concentration (based on SiO2) of 1% to 30% by mass, more preferably 5% to 25% by mass. While alkali removal and cleaning are not problematic at concentrations less than 1% by mass, manufacturing efficiency decreases. If the concentration exceeds 30% by mass, the concentration is too high, reducing alkali removal and cleaning efficiency.

[0049] The conditions for immersion in the acid-water solution are not particularly limited as long as the alkali is removed to the desired amount. Typically, the treatment temperature is 5°C to 100°C, and the treatment time is 0.5 hours to 24 hours. After the acid treatment, it is preferable to clean using a conventionally known method. For example, filtration and cleaning with pure water. Alternatively, the above acid treatment and cleaning can be repeated as needed.

[0050] The residual amount (mass ratio) of alkali (M) after alkali removal is preferably 300 ppm or less, more preferably 200 ppm or less, further preferably 100 ppm or less, and particularly preferably 50 ppm or less. By thoroughly removing the alkali in this step, particle adhesion in subsequent steps can be prevented, and the formation of sintered particles in the firing process can be prevented. Furthermore, it is known that the residual amount (content) of alkali affects dielectric properties. By thoroughly removing the alkali in this step, even when using a silica-alkali aqueous solution in the raw material, hollow particles with low dielectric constant and low dielectric loss tangent can be obtained.

[0051] In addition, the alkali content of the final product (hollow granules) is preferably within the above range. Generally, the alkali content of the final product is the same as that after the alkali removal process.

[0052] The residual alkali content was measured using an atomic absorption spectrophotometer, with Na or K measured from the sample of the substance remaining after the particles were dissolved in acid. Na was measured when sodium silicate was used, and K was measured when potassium silicate was used. Specific details are explained in the examples.

[0053] (Firing process)

[0054] This process involves firing the hollow particles after removing the alkali. The firing temperature is preferably 600℃~1200℃, more preferably 900℃~1100℃. At firing temperatures below 600℃, the residual SiOH groups are higher, leading to a higher dielectric loss tangent in the particles. Therefore, even with addition to the resin, it is difficult to achieve a reduction in the dielectric loss tangent. At firing temperatures above 1200℃, the hollow particles easily sinter together, resulting in irregularly shaped and coarse particles. This reduces the filterability and injectability of the liquid used to form the resin composition.

[0055] (Grading process)

[0056] In this process, the hollow granules are graded to remove coarse particles. This grading process is performed between the hollow granule preparation process and the firing process. If grading is performed before alkali removal, it is necessary to perform grading immediately after granulation to prevent the hollow granules from absorbing moisture (deliquescence) and agglomerating / adheding. Therefore, it is preferable to perform grading after alkali removal. At this time, grading can be performed after alkali removal, or drying can be performed after alkali removal followed by grading. To better enjoy the effects of the present invention, it is preferable to perform grading after drying.

[0057] In the grading process, the amount of coarse particles with a diameter greater than 8.0 μm is preferably 10% by volume or less, more preferably 5% by volume or less, and even more preferably 1% by volume or less. Through this grading process, the proportion of floating hollow particles can be controlled within a specified range.

[0058] The grading process in this section refers to particle size classification, which separates powders according to their particle size with the aim of achieving a generally uniform particle size. Fluid classification is an example of particle size classification. Fluid classification can be divided into dry classification and wet classification. Wet classification requires the particles to be suspended in water. This can lead to the formation of SiOH groups on the particle surface, potentially negatively impacting dielectric properties. Therefore, dry classification is preferred.

[0059] Dry classification machines can be broadly categorized by principle into gravity classifiers, inertial classifiers, and centrifugal classifiers. Inertial classifiers and centrifugal classifiers, which utilize the inertial force of particles for classification, can achieve more precise classification. In particular, examples of classifiers that can perform well even for lighter particles that are not easily subjected to centrifugal force include the Elbow-Jet manufactured by Nippon Steel Mining Co., Ltd., the SG Septar manufactured by 3M Japan Co., Ltd., the Aerofine Classifier manufactured by Nissin Engineering Co., Ltd., and the MyCrosspin manufactured by PNEUMATIC Industries Co., Ltd. Among these, Elbow-Jet and Aerofine Classifier are preferred because they can precisely classify light hollow particles.

[0060] Drying can also be appropriately performed in the manufacturing process of hollow granules. The drying process can be set between the alkali removal process and the classification process, between the classification process and the calcination process, or simultaneously at both of these locations. Multiple drying processes can also be performed as needed.

[0061] Heating is suitable as a drying process. The preferred drying temperature is 50℃ to 400℃, and more preferably 50℃ to 200℃. Specifically, examples can be given of drying at a low temperature of around 50℃ to 200℃, drying by gradually increasing the temperature, and drying by changing the temperature in several stages.

[0062] Furthermore, it is preferable to perform the sieving process for the granular blocks at at least one point after drying and firing. In addition, the granular blocks refer to, for example, granular blocks with a particle size greater than 50 μm, and a sieve with an aperture (mesh size) capable of removing such granular blocks should be used appropriately.

[0063] [Example]

[0064] The embodiments of the present invention are described in detail below.

[0065] [Example 1]

[0066] Hollow particles were obtained by spraying 30,000 g of a water glass aqueous solution (SiO₂ / Na₂O molar ratio 3.2, SiO₂ concentration 24% by mass) in hot air (hollow particle preparation step). In the spray drying apparatus, the water glass aqueous solution was supplied from one of two fluid nozzles at a flow rate of 0.62 kg / hr, and air was supplied from the other nozzle at a flow rate of 31,800 L / hr (air / liquid volume ratio 63,600). The inlet temperature was 400°C, and the outlet temperature was 150°C.

[0067] Next, 5000g of the hollow particles were immersed in 32000g of a 10% (w / w) sulfuric acid aqueous solution and stirred at 35°C for 15 hours. At this point, the concentration of the solid component (SiO₂) was 10.2% (w / w). Furthermore, since sulfuric acid is a divalent acid, the mole number (Ma) of the acid and the mole ratio (Ma / Msp) of the base (Na₂O) were 3.3. The pH of the dispersion was 3.0. After this impregnation treatment, the particles were filtered and washed with pure water (alkali removal process).

[0068] Next, the mixture is dried at 120°C for 24 hours using a dryer (drying process). After drying, it is pulverized and sieved through a 75μm sieve to remove coarse particles.

[0069] Next, using a cyclone separator manufactured by our company, the flow rate of the powder conveyor line is set to 5 m / s for dry centrifugal separation and processing (classification process). Particles that are not captured by the cyclone separator are recovered using a bag filter.

[0070] Furthermore, hollow particles of this embodiment are obtained by heating the graded particles at 1000°C for 10 hours (firing process). After firing, particle lumps (foreign matter) are removed using a sieve with a 150 μm aperture.

[0071] The obtained hollow particles were added together with liquid acid anhydride "Licasid MH700" manufactured by Shin Nippon Rikka and imidazole epoxy resin curing agent "2PHZ-PW" manufactured by Shikoku Kasei to liquid epoxy resin "ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. After premixing in a planetary ball mill, the mixture was mixed in a three-roll mill to prepare a liquid for forming the resin composition. Here, "ZX-1059" was added in a ratio of 100 parts by weight, "Licasid MH700" in 86 parts by weight, and "2PHZ-PW" in 1 part by weight. Furthermore, the hollow particles were added in a manner that the proportion of hollow particles in the resin composition was 35% by volume. The prepared liquid for forming the resin composition was heated at 170°C for 2 hours to solidify it, resulting in a plate-shaped resin composition of 50mm×50mm×1mm.

[0072] The physical properties of the hollow particles and resin composition obtained as described above were measured and evaluated. The results, along with the preparation conditions, are shown in Table 1. The same procedures were performed in other examples and comparative examples.

[0073] (1) Average particle size (D50), maximum particle size (D100), and amount of coarse particles

[0074] Particle size distribution was measured dry using a particle size analyzer (SEISHIN Enterprise Co., Ltd. Laser MicroSizer LMS-3000). Based on the measurement results, the average particle size (D50) and maximum particle size (D100) were obtained. Furthermore, the amount of coarse particles was calculated as the volume ratio of particles larger than 8.0 μm.

[0075] (2) Na residue in hollow particles

[0076] Hollow particles were pretreated with sulfuric acid and hydrofluoric acid, then dissolved in hydrochloric acid. The amount of sodium was measured by atomic absorption spectrophotometry using an atomic absorption spectrophotometer (Hitachi Z-2310).

[0077] (3) Particle density and porosity of hollow particles

[0078] Particle density was measured using the gas gravimetric method (gas gravimetric method) with an Ultrapyc1200e manufactured by Quantachrome Instruments. Nitrogen gas was used.

[0079] Based on the particle density, the porosity (%) is calculated using the formula "[2.2 - (particle density)] / 2.2 × 100". In this formula, the hollow particles are materials formed of silicon dioxide, and the density of silicon dioxide is 2.2 g / cm³.

[0080] (4) Dielectric constant (Dk) and dielectric loss tangent (Df) of hollow particles

[0081] The dielectric constant (Dk) and dielectric loss tangent (Df) were measured using a network analyzer (ANRITSU MS46122B) and a cavity resonator (1 GHz) via the cavity resonator perturbation method. The measurements were performed according to ASTM D2520 (JIS C2565).

[0082] (5) The ratio of floating particles a, suspended particles b, and settled particles c when suspended in water

[0083] First, hollow particles and water were mixed to a concentration of 0.5% by mass and subjected to ultrasonic treatment for 10 minutes. The resulting dispersion was then allowed to stand at 25°C for 24 hours, after which floating, suspended, and settled particles were recovered separately. Next, each particle was dried at 105°C for 24 hours, and its proportion was calculated.

[0084] (6) Filterability of the liquid used to form the resin composition

[0085] The filter (SHP type: 30μm) manufactured by ROKI TECHNO was used, and the flow rate per unit area was evaluated until the filter became clogged.

[0086] The evaluation criteria are as follows. ◎:≧1g / cm² 〇: 0.5 g / cm² or higher but less than 1.0 g / cm² △: 0.3 g / cm² or higher but less than 0.5 g / cm² ×:<0.3g / cm²

[0087] (7) Injectability of the liquid used to form the resin composition

[0088] The time required to fill 25 mm between glass plates with a 20 μm gap by injecting the liquid used to form the resin composition was evaluated.

[0089] The evaluation criteria are as follows. ◎: Within 200 seconds 〇: Greater than 200 seconds but less than 400 seconds △: Greater than 400 seconds but less than 600 seconds ×: Greater than 600 seconds

[0090] (8) Dielectric constant (Dk) and dielectric loss tangent (Df) of the resin composition.

[0091] The dielectric constant (Dk) and dielectric loss tangent (Df) of a 50mm×50mm×1mm plate-shaped molded body (resin composition) were measured at 9.4 GHz using a coaxial resonator of a network analyzer (ANRITSU, MS46122B).

[0092] The comparison with resin compositions without hollow particles (fillers) is performed according to the following formula and evaluated according to the following criteria. <Formula> Rate of decrease in dielectric constant (Dk) (%) = (Dielectric constant without filler - Dielectric constant with filler) / Dielectric constant without filler × 100 〇: Reduction rate > 0 △: Reduction rate = 0 ×: Reduction rate < 0 Formula: Reduction rate (%) of dielectric loss tangent (Df) = (Dielectric loss tangent without filler - Dielectric loss tangent with filler) / Dielectric loss tangent without filler × 100 ◎: Reduction rate of over 50% 〇: 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%

[0093] [Example 2]

[0094] Except for the grading process, the hollow granular and plate-shaped resin compositions were manufactured in the same manner as in Example 1. In the grading process, a dry inertial grading process was performed using an Elbow-Jet (EJ-15) manufactured by Nippon Steel Mining Co., Ltd. This device can separate the powder into three types based on the grading: F powder (micro powder), M powder (fine powder), and G powder (coarse powder). The edge distance of the F powder was adjusted so that the amount of coarse particles contained in the F powder (micro powder) was less than 5% by volume. The coarse particles were then recovered through a bag filter for use in subsequent processes.

[0095] [Example 3]

[0096] In Example 2, the F edge distance was adjusted during the grading process so that the amount of coarse particles contained in the F powder (micro powder) was less than 1% by volume. Otherwise, the hollow granular and sheet-like resin compositions were manufactured in the same manner as in Example 2.

[0097] [Example 4]

[0098] Except for dry centrifugation (semi-free vortex) classification using the Aerofine Classifier manufactured by Nissin Engineering Co., Ltd. in the classification process, the hollow particle and plate-shaped resin composition were manufactured in the same manner as in Example 1. Classification was performed by adjusting the blade angle, etc., so that the amount of coarse particles contained in the recovered powder was less than 1% by volume.

[0099] [Comparative Example 1]

[0100] In the alkali removal process, the impregnation and stirring time was changed from 15 hours to 1.5 hours, and no grading treatment (grading process) was performed. Otherwise, the hollow granular and plate-shaped resin compositions were manufactured in the same manner as in Example 1.

[0101] [Comparative Example 2]

[0102] In the hollow particle preparation process, the inlet temperature of the spray dryer was set to 250°C, and no grading process was performed. Otherwise, the hollow particle and plate-shaped resin composition were manufactured in the same manner as in Example 1.

[0103] [Comparative Example 3]

[0104] After the firing process, a grading process is performed. Otherwise, the hollow granular and plate-shaped resin compositions are manufactured in the same manner as in Example 1 (with the same grading conditions).

[0105] As shown in Table 1, the hollow particles described in the examples and the resin compositions incorporating these hollow particles achieve low dielectric constant and low dielectric loss tangent. Furthermore, the liquid used to form the resin compositions with the hollow particles described in the examples exhibits excellent filterability and injectability.

[0106] [Table 1]

[0107] none.

Claims

1. A hollow particle having a cavity inside a non-porous shell, wherein the average particle size (D50) of the hollow particle is in the range of 0.1 μm to 10 μm; when the hollow particle is suspended in water, the floating particles are 0.5% to 7.0% by mass, the suspended particles are 0% to 4.0% by mass, the settling particles are 89.0% to 99.5% by mass, and the content of coarse particles with a particle size greater than 8.0 μm is less than 10% by volume.

2. A resin composition comprising hollow particles as described in claim 1.

3. A method for manufacturing hollow particles, characterized in that the manufacturing method comprises: The hollow particle preparation process involves spray drying a silica-alkali aqueous solution in a hot air stream to prepare hollow particles; the alkali removal process involves neutralizing and removing the alkali contained in the prepared hollow particles with acid; the calcination process involves calcining the alkali-removed hollow particles at 600℃~1200℃; and the grading process involves grading the hollow particles between the alkali removal process and the calcination process to reduce the content of coarse particles with a particle size greater than 8.0μm to below 10% by volume.

4. The method for manufacturing hollow particles as described in claim 3, wherein, In the alkali removal process, the alkali content in the hollow particles is reduced to below 200 ppm.

5. The method for manufacturing hollow particles as described in claim 3, wherein, The grading process is carried out after the hollow particles, from which alkali has been removed, are dried.

6. A method for manufacturing hollow particles as described in any one of claims 3 to 5, wherein, The grading process described above is a dry grading process.