Hollow particles and their manufacturing method, and resin composition

Abstract

The present invention relates to hollow particles having a cavity inside a non-porous outer shell. The average particle size (D50) is 0.1 to 10 μm, and when suspended in water, the suspended particles are 0.5 to 7.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settled particles are 89.0 to 99.5 mass%. An insulating material incorporating such hollow particles enables low dielectric constant and low dielectric loss tangent.

Description

Technology Field

[0001] The present invention relates to hollow particles used as fillers for insulating materials. Background Technology

[0002] In recent years, information and communications have been moving toward higher speeds and larger capacities. Consequently, materials used in communication devices are required to have low dielectric constant (low Dk) and low dielectric loss tangent (low Df). For example, printed circuit boards on which semiconductor devices are mounted require insulating materials with low dielectric constant and low dielectric loss tangent. If the dielectric constant of an insulating material is high, dielectric loss occurs; furthermore, if the dielectric loss tangent is high, there is a risk of increased heat generation in addition to dielectric loss.

[0003] In order to achieve low dielectric constant and low dielectric loss tangent of insulating materials, development of resin materials, which are the main components of insulating materials, is being carried out. As such resin materials, epoxy resins, polyphenylene ether resins, fluorine resins, etc. have been proposed (for example, see Patent Documents 1 to 5).

[0004] Fillers are incorporated into these resin materials to improve durability (rigidity) or heat resistance. It is known that metal oxides such as silica, boron nitride, talc, kaolin, clay, mica, alumina, zirconia, and titania are used as fillers (see, for example, Patent Document 3). Prior art literature

[0005] WO2009 / 041137 Japanese Patent Publication No. 2006-516297 Japanese Patent Publication No. 2017-057352 Japanese Patent Publication No. 2001-288227 Japanese Patent Publication No. 2019-172962 The problem to be solved

[0006] Among materials used as fillers, silica is excellent in terms of low dielectric constant and low dielectric loss tangent. However, as data communication is rapidly advancing toward high speed and high capacity, there is a demand for even lower dielectric constant and lower dielectric loss tangent. means of solving the problem

[0007] The inventors have discovered that hollow particles satisfying certain conditions, which do not contain coarse particles, can achieve low dielectric constant and low dielectric loss tangent of insulating materials. Furthermore, they have found that these hollow particles do not interfere with the filterability and injection properties of the liquid for forming insulating materials during the manufacturing process of insulating resins.

[0008] That is, the present invention relates to hollow particles having a cavity inside a nonporous outer shell. These hollow particles have an average particle size (D50) of 0.1 to 10 μm, and when these hollow particles are suspended in water, the suspended particles are 0.5 to 7.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settled particles are 89.0 to 99.5 mass%.

[0009] In addition, the method for manufacturing hollow particles according to the present invention comprises a hollow particle preparation process in which hollow particles are prepared by spray-drying an alkali silicate aqueous solution in a hot air stream, an alkali removal process in which alkali contained in the prepared hollow particles is neutralized with an acid to remove it, a calcination process in which the alkali-removed hollow particles are calcined, and a classification process in which the hollow particles are classified to remove coarse particles between the hollow particle preparation process and the calcination process. Effects of the invention

[0010] The hollow particles of the present invention can achieve low dielectric constant and low dielectric loss tangent of insulating materials, and furthermore, can increase the transmission speed of semiconductors or reduce transmission loss. In addition, the hollow particles of the present invention do not interfere with the filterability and injection properties of the liquid for forming insulating materials during the insulating material manufacturing process. Therefore, excellent insulating materials can be manufactured stably. Specific details for implementing the invention

[0011] [Hollow particles]

[0012] The hollow particles of the present invention have a cavity inside the nonporous outer shell and have an average particle size of 0.1 to 10 μm. When these hollow particles are suspended in water, the suspended particles are 0.5 to 7.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settled particles are 89.0 to 99.5 mass%.

[0013] Here, the hollow particles of the present invention are suitable as silica-based hollow particles having silica as the main component. Accordingly, the hollow particles (outer shell) may include inorganic oxides such as alumina, zirconia, and titania in addition to silica. The silica content in the particles is preferably 70 mass% or more, more preferably 90 mass% or more, and even more preferably 95 mass% or more, and it is particularly preferred to contain substantially only silica.

[0014] The hollow particles of the present invention include floating particles with a low specific gravity that float when suspended in water. Typically, since floating particles have a high porosity, incorporating these particles into a resin composition enables low dielectric constant and low dielectric loss tangent. Furthermore, since hollow particles with high porosity generally have large particle diameters, controlling the amount of these floating particles to 0.5 to 7.0 mass% of the total particles controls (reduces) the amount of coarse particles. Consequently, in the manufacturing process of resin compositions such as insulating materials, the filtration and injection properties of the liquid for forming the resin composition are improved, and the surface smoothness after molding can be enhanced. At this time, the content of coarse particles with a particle diameter exceeding 8.0 μm is preferably 10 volume% or less, more preferably 5 volume% or less, and even more preferably 1 volume% or less.

[0015] Furthermore, suspended particles tend to have low particle strength because the ratio of the outer thickness to the particle diameter is small. Consequently, there is a risk of particle cracking during the manufacture of resin compositions, such as insulating materials. These cracked particles not only hinder the reduction of dielectric constant and dielectric loss tangent but also worsen the fluidity of the liquid used to form the resin composition. In other words, cracked particles are a factor that lowers the uniformity of the resin composition (molded product) or causes voids to form within the resin composition. Cracking of particles can be suppressed by controlling the amount of suspended particles.

[0016] In the present invention, since the amount of suspended particles is controlled, desirable characteristics of high-porosity particles (particularly low dielectric constant and low dielectric loss tangent) are secured, while undesirable characteristics of high-porosity particles (particularly the occurrence of cracking) are suppressed to an extent that is not problematic. Furthermore, among the suspended particles, there are high-porosity particles even if they are small in diameter, and since these particles are less likely to crack during the manufacturing process compared to large-diameter particles, the undesirable characteristics of high-porosity particles can be suppressed to the maximum extent as a whole.

[0017] The content of suspended particles is preferably 1.0 to 5.0 mass%, more preferably 1.0 to 4.0 mass%, and even more preferably 2.0 to 4.0 mass%. In addition, the content of settled particles is preferably 91.0 to 99.5 mass%, more preferably 92.0 to 99.0 mass%, and even more preferably 95.0 to 98.0 mass%.

[0018] The ratio of suspended particles, suspended particles, and settled particles when suspended in water is calculated by recovering and weighing each particle from the suspension. Specifically, this is explained in the examples.

[0019] In addition, the average particle size (D50) of the hollow particles of the present invention is in the range of 0.1 to 10 μm. It is difficult to manufacture particles with an average particle size of less than 0.1 μm using a spray drying method. Furthermore, particles with an average particle size exceeding 10 μm are not suitable for semiconductor-related products. Therefore, the average particle size is preferably 0.5 to 10 μm, and more preferably 1.0 to 5.0 μm.

[0020] In addition, 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 the average particle size (D50), and more preferably 8 times or less. Typically, it is 2 times or more, and may exceed 5 times as long as it satisfies the requirements of the present invention.

[0021] The average particle size (D50), maximum particle size (D100), and coarse particle content are measured by laser diffraction and scattering. Specifically, this is explained in the examples.

[0022] The porosity of the hollow particles of the present invention is preferably 5 volume% or more, more preferably 8 volume% or more, and even more preferably 10 volume% or more. The upper limit is preferably 50 volume% or less, more preferably 35 volume% or less, even more preferably 25 volume% or less, and most preferably 20 volume% or less. With such porosity, the dielectric constant and dielectric loss tangent can be reduced. In addition, the particle strength is maintained at a predetermined level or higher, and particle cracking can be effectively suppressed. Here, the porosity is calculated from the particle density. Specifically, this is explained in the examples.

[0023] The hollow particles of the present invention are suitable for use as insulating material fillers for electronic components such as semiconductors. Specifically, they can be incorporated into copper-clad laminates, prepregs, build-up films, etc., for forming printed circuit boards (including rigid and flexible substrates). Additionally, they can be incorporated into semiconductor package-related materials such as mold resins, mold underfills, and underfills, or into adhesives for flexible substrates.

[0024] [Resin Composition]

[0025] A resin composition can be prepared by combining the aforementioned hollow particles with a resin. This resin composition can be used for applications of the aforementioned hollow particles, such as insulating materials for electronic components like semiconductors.

[0026] As the resin, a curable resin generally used in electronic components such as semiconductors may be used. It may be a photocurable resin, but a thermocurable resin is preferred. Examples of such curable resins include epoxy resins, polyphenylene ether resins, fluorine resins, polyimide resins, bismaleimide resins, acrylic resins, methacrylate resins, silicone resins, BT resins, cyanate resins, etc. Specific examples of epoxy resins include bisphenol-type epoxy resins, novolak-type epoxy resins, triphenolalkane-type epoxy resins, epoxy resins having a biphenyl backbone, epoxy resins having a naphthalene backbone, dicyclopentadiene phenol novolak 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 alone or in a mixture of two or more types.

[0027] It is preferable that the resin composition (liquid for forming a resin composition) contains hollow particle A and curable resin B in a mass ratio (A / B) of 10 / 100 to 95 / 100. With this mass ratio, the liquid for forming a resin composition can sufficiently perform its function as a filler while maintaining properties such as fluidity. This mass ratio (A / B) is more preferably 30 / 100 to 80 / 100.

[0028] The resin composition (liquid for forming the resin composition) preferably includes 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, the curing agent may be a resin having two or more phenolic hydroxyl groups in one molecule (phenol resins such as bisphenol-type resin, novolak resin, triphenolalkane-type resin, resol-type phenol resin, phenolaralkyl resin, biphenyl-type phenol resin, naphthalene-type phenol resin, cyclopentadiene-type phenol resin, etc.) or anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methyl anhydride.

[0029] Various additives (coloring agents, stress relievers, defoaming agents, leveling agents, coupling agents, flame retardants, curing accelerators, etc.) may be added to the resin composition (liquid for forming the resin composition) as needed.

[0030] The resin composition of the present invention can be obtained by conventionally known methods. For example, it can be obtained by mixing a thermosetting resin, hollow particles, a curing agent, additives, etc., kneading them with a roll mill or the like to prepare a coating solution (a solution for forming a resin composition), applying it to a gas, and then curing it by heat, ultraviolet rays, etc.

[0031] [Method for manufacturing hollow particles]

[0032] The method for manufacturing hollow particles according to the present invention comprises a hollow particle preparation process in which hollow particles are prepared by spray-drying an aqueous alkali silicate solution in a hot air stream, an alkali removal process in which alkali contained in the prepared hollow particles is neutralized with an acid to remove it, and a calcination process in which the alkali-removed hollow particles are calcined. Between the hollow particle preparation process and the calcination process, a classification process is provided to classify the hollow particles and remove coarse particles. Additionally, other processes such as a drying process may be provided between each process.

[0033] By this manufacturing method, for example, the hollow particles described above can be manufactured.

[0034] It is generally considered desirable to perform classification treatment at the final stage after calcination to refine the final particles when manufacturing calcined particles. However, in the manufacturing method of the present invention, classification treatment is performed specifically before the calcination process. If the calcination process is carried out without classification treatment, coarse particles with high porosity that need to be removed will remain. Since these coarse particles are prone to cracking, there is a risk that they will crack due to the stress of shrinkage caused by heating. Furthermore, the fragments generated by cracking cannot be removed even if a classification process is performed afterward because their particle size is small. In addition, since these fragments are dense silica without pores, they hinder the low dielectric constant and low dielectric loss tangent. By performing classification treatment before calcination, these problems are avoided, and the low dielectric constant and low dielectric loss tangent of the manufactured particles can be realized more reliably, and particles suitable for high-speed data communication are obtained.

[0035] Below, each process is explained in detail.

[0036] (Hollow particle preparation process)

[0037] In this process, hollow particles are prepared by spray-drying an alkaline silicate solution in a hot air stream.

[0038] The molar ratio (SiO2 / M2O) of SiO2 and M2O (M is an alkali metal) of alkali silicate 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 large, making it difficult to perform acid cleaning to remove the alkali, and the deliquescence of the spray-dried product increases, 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, and even if an aqueous solution can be prepared, there are cases where the desired hollow particles cannot be obtained by spray drying.

[0039] The concentration of SiO2 in the aqueous alkali silicate solution is preferably 1 to 30 mass%, and more preferably 5 to 28 mass%. Although production is possible with less than 1 mass%, productivity is significantly reduced. If it exceeds 30 mass%, the stability of the aqueous alkali silicate solution is significantly reduced, resulting in high viscosity, which may make spray drying impossible. Even if spray drying is possible, the particle size distribution and outer thickness become very non-uniform, which may limit the uses of the obtained particles. As the alkali silicate, water-soluble sodium silicate or potassium silicate may be used. Sodium silicate is preferred.

[0040] As a spray drying method, conventionally known methods such as the rotary disc method, the pressurized nozzle method, and the two-fluid nozzle method may be adopted. Here, the two-fluid nozzle method is suitable.

[0041] In spray drying, the inlet temperature of the spray dryer is preferably 300 to 600°C, and more preferably 350 to 550°C. In addition, the outlet temperature is preferably 120 to 300°C, and more preferably 130 to 250°C. By setting the inlet and outlet temperatures within the above ranges, hollow particles can be obtained stably.

[0042] (Alkali removal process)

[0043] In this process, alkali contained in the prepared hollow particles is removed. A method of removal by adding acid to neutralize it is suitable.

[0044] As for the acid, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid, tartaric acid, and malic acid can be used. Among these, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid are suitably used, and sulfuric acid is particularly preferred in terms of hydration.

[0045] In this process, it is preferable to immerse the prepared hollow particles in an acid solution.

[0046] When hollow particles are immersed in an aqueous acid solution, the molar ratio (Ma / Msp) of the number of moles of M2O (Msp) and the number of moles of acid (Ma) in the hollow 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 relative to M2O is excessively small, so the silica skeletonization of the silicic acid, which is thought to occur along with the removal of alkali, does not proceed, and the hollow particles may partially dissolve or the dissolved alkali silicate may gel. Even if the molar ratio exceeds 4.7, the silica skeletonization does not proceed further, and the acid is excessive, making it uneconomical.

[0047] In addition, it is preferable to immerse the hollow particles in an aqueous acid solution such that the concentration of the hollow particles is 1 to 30 mass% as SiO2. 5 to 25 mass% is more preferable. If the concentration is less than 1 mass%, there is no problem with alkali removal or cleaning performance, but the manufacturing efficiency decreases. If the concentration exceeds 30 mass%, the concentration is excessively high, and the alkali removal and cleaning efficiency may decrease.

[0048] The conditions for immersion in the acid solution are not particularly limited as long as the alkali can be removed to the desired amount; typically, the treatment temperature is 5 to 100°C and the treatment time is 0.5 to 24 hours. After this acid treatment, it is preferable to wash using a conventionally known method. For example, filter washing with pure water. Additionally, if necessary, the acid treatment and washing may be repeated.

[0049] The residual amount (mass ratio) of alkali (M) after alkali removal is preferably 300 ppm or less, more preferably 200 ppm or less, even more preferably 100 ppm or less, and particularly preferably 50 ppm or less. By sufficiently removing alkali in this process, particle adhesion in subsequent processes is prevented, and the generation of sintered particles in the firing process can be prevented. In addition, it is known that the residual amount (content) of alkali affects dielectric properties. By sufficiently removing alkali in this process, hollow particles that enable low dielectric constant and low dielectric loss tangent can be obtained even when an alkali silicate aqueous solution is used as the raw material.

[0050] In addition, the alkali content of the final product (hollow particles) is also preferably within the range described above, and typically, the alkali content of the final product becomes equivalent to the alkali content after the alkali removal process.

[0051] The residual alkali content is determined by using a sample in which particles are dissolved in acid, and measuring Na or K using an atomic absorption spectrophotometer. Na is measured when sodium silicate is used, and K is measured when potassium silicate is used. Specifically, this is explained in the examples.

[0052] (Sintering process)

[0053] This process is a process of calcining hollow particles from which alkali has been removed. The calcination temperature is preferably 600 to 1200°C, and more preferably 900 to 1100°C. If the calcination temperature is below 600°C, the amount of residual SiOH groups is high, and the dielectric loss tangent of the particles increases. Therefore, even if incorporated into a resin, it is difficult to obtain an effect of reducing the dielectric loss tangent. If the calcination temperature exceeds 1200°C, hollow particles tend to sinter easily with each other, making it easy for irregularly shaped particles or coarse particles to be generated. This causes a decrease in the filterability and injection properties of the liquid for forming the resin composition.

[0054] (Classification process)

[0055] In this process, hollow particles are classified to remove coarse particles. This classification treatment is performed between the hollow particle preparation process and the calcination process. If the classification treatment is performed before alkali removal, it is necessary to perform the classification treatment immediately after granulation to prevent the hollow particles from absorbing moisture (deliquescence) and aggregating or bonding. Therefore, it is preferable to perform the classification treatment after alkali removal. At this time, the classification treatment may be performed immediately after the alkali removal treatment, or a drying treatment may be performed after the alkali removal treatment, and then the classification treatment may be performed. To further enjoy the effects of the present invention, it is preferable to perform the classification treatment after the drying treatment.

[0056] In the classification process, it is preferable to keep the amount of coarse particles with a particle size exceeding 8.0 μm at 10 volume% or less, more preferable to keep it at 5 volume% or less, and even more preferable to keep it at 1 volume% or less. Through this classification process, the ratio of suspended hollow particles can be controlled to a predetermined range.

[0057] In this classification process, classification refers to particle size classification, which divides powders based on particle diameter for the purpose of standardizing the particle size distribution. Fluid classification can be cited as an operation for particle size classification. Fluid classification can be classified into dry classification and wet classification. Wet classification requires performing the classification treatment while the particles are suspended in water. Consequently, SiOH groups may form on the particle surface, potentially adversely affecting dielectric properties. Therefore, dry classification is preferred.

[0058] Classifiers used for dry classification can be broadly classified in principle into gravity classifiers, inertial classifiers, and centrifugal classifiers. By using inertial classifiers, which classify using the inertial force of particles, or centrifugal classifiers, more precise classification becomes possible. In particular, examples of classifiers that exhibit characteristics even with light particles that are difficult to apply centrifugal force to include the Elbow Jet manufactured by Nittetsu Kogyo, the SG Separator manufactured by 3M Japan, the Aerofine Classifier manufactured by Nissin Engineering, and the Micro Spin manufactured by Nippon Pneumatic Kogyo. Among these, the Elbow Jet and the Aerofine Classifier are preferred because they can precisely classify light hollow particles.

[0059] In the method for manufacturing hollow particles, a drying treatment may be performed as appropriate. The drying process may be provided, for example, between the alkali removal process and the classification process, between the classification process and the calcination process, or at both ends thereof. It may be provided multiple times if necessary.

[0060] As a drying treatment, heat drying is suitable. The drying temperature is preferably 50 to 400°C, and more preferably 50 to 200°C. Specifically, examples include drying over time at a low temperature of about 50 to 200°C, drying by gradually increasing the temperature, or drying by changing the temperature in several stages.

[0061] In addition, it is preferable to perform a sieve separation treatment to separate particle lumps at least at either after drying or after firing. Furthermore, particle lumps refer, for example, to particles with a diameter exceeding 50 μm, and a sieve with a mesh size (number of meshes) capable of removing such particle lumps is appropriately used.

[0062] Examples

[0063] Hereinafter, embodiments of the present invention will be described in detail.

[0064] [Example 1]

[0065] 30,000 g of an aqueous water glass solution (SiO2 / Na2O molar ratio 3.2, SiO2 concentration 24 mass%) was sprayed into hot air to obtain hollow particles (hollow particle preparation process). In the spray drying device, the aqueous water glass solution was supplied at a flow rate of 0.62 kg / hr from one of the two-fluid nozzles, and air was supplied at a flow rate of 31,800 L / hr from the other nozzle (air / liquid volume ratio 63,600). In addition, the inlet temperature was 400°C and the outlet temperature was 150°C.

[0066] Next, 5,000 g of these hollow particles were immersed in 32,000 g of an aqueous sulfuric acid solution with a concentration of 10 mass% and stirred at 35°C for 15 hours. At this time, the solid content (SiO2) concentration was 10.2 mass%. In addition, since sulfuric acid is a divalent acid, the molar ratio of acid (Ma) to alkali (Na2O) (Ma / Msp) was 3.3. The pH of the dispersion was 3.0. After this immersion treatment, filtration washing with pure water was performed (alkali removal process).

[0067] Next, the product was dried in a dryer at 120°C for 24 hours (drying process). After drying, the product was crushed and the coarse particles were removed by passing it through a sieve with a mesh size of 75 μm.

[0068] Next, dry centrifugal classification was performed using a proprietary cyclone with a flow rate of 5 m / s in the powder transport line (classification process). Particles that passed through without being captured by the cyclone were recovered using a bag filter.

[0069] In addition, hollow particles of the present example were obtained by heat-treating the classified particles at 1000°C for 10 hours (sintering process). In addition, after sintering, particle clumps (foreign matter) were removed using a sieve with a mesh size of 150 μm.

[0070] The obtained hollow particles were mixed with Shin Nippon Ricacid's liquid acid anhydride "Ricacid MH700" and Shikoku Kasei's imidazole-based epoxy resin curing agent "2PHZ-PW" into Nittetsu Chemical & Material's liquid epoxy resin "ZX-1059". After preliminary mixing in an oil mill, the mixture was mixed using three rollers to prepare a liquid for forming a resin composition. Here, "ZX-1059" was mixed 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. Additionally, the mixture was formulated so that the ratio of hollow particles in the resin composition was 35% by volume. The prepared liquid for forming a resin composition was heated and cured at 170°C for 2 hours to obtain a plate-shaped resin composition measuring 50 mm × 50 mm × 1 mm.

[0071] The physical properties of the hollow particles and resin compositions 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 performed for other examples and comparative examples.

[0072] (1) Average particle size (D50), maximum particle size (D100) and coarse particle amount

[0073] The particle size distribution was measured dry using a particle size analyzer (Seishin Kikyo Laser Micron Sizer LMS-3000). From the measurement results, the average particle size (D50) and the maximum particle size (D100) were obtained. In addition, the amount of coarse particles was calculated as the volume ratio of particles exceeding 8.0 μm.

[0074] (2) Remaining amount of Na in hollow particles

[0075] After pre-treating the hollow particles with sulfuric acid and hydrofluoric acid, they were dissolved in hydrochloric acid, and the amount of Na was measured by atomic absorption analysis using an atomic absorption spectrophotometer (Hitachi Z-2310).

[0076] (3) Particle density and porosity of hollow particles

[0077] Particle density was measured by gas pycnometers using the Quantachrome Instruments Ultrapyc1200e. Nitrogen gas was used.

[0078] From this particle density, the porosity (%) was calculated using the formula [2.2-(particle density)] / 2.2×100. In this formula, the hollow particles were assumed to be formed of silica, and the silica density of 2.2 g / cm³ was used.

[0079] (4) Permittivity (Dk) and dielectric loss tangent (Df) of hollow particles

[0080] The permittivity (Dk) and dielectric loss tangent (Df) were measured by the cavity resonator perturbation method using a network analyzer (Anritsu, MS46122B) and a cavity resonator (1 GHz). This measurement was performed in accordance with ASTMD2520 (JIS C2565).

[0081] (5) Ratio of suspended particles a, suspended particles b, and settled particles c when suspended in water

[0082] First, hollow particles and water were mixed to a concentration of 0.5 mass%, and ultrasonic treatment was performed for 10 minutes. After the resulting dispersion was left to stand at 25°C for 24 hours, the suspended particles, suspended particles, and settled particles were recovered, respectively. Subsequently, each particle was dried at 105°C for 24 hours, weighed, and the ratio was calculated.

[0083] (6) Filtration of the liquid for forming the resin composition

[0084] Using a filter manufactured by Rocky Techno Co., Ltd. (SHP type: 30㎛), it was evaluated based on the amount of liquid passing through per unit area up to filter clogging.

[0085] The evaluation criteria are as follows.

[0086] ◎: ≥1g / ㎠

[0087] ○: 0.5g / ㎠ or more and less than 1.0g / ㎠

[0088] △: 0.3g / ㎠ or more and less than 0.5g / ㎠

[0089] ×: <0.3g / ㎠

[0090] (7) Injectability of liquid for forming resin composition

[0091] It was evaluated as the time required to inject a liquid for forming a resin composition between glass plates having a gap of 20㎛ and to fill 25㎜.

[0092] The evaluation criteria are as follows.

[0093] ◎: Within 200 seconds

[0094] ○: Exceeds 200 seconds and is within 400 seconds

[0095] △: Exceeds 400 seconds and is within 600 seconds

[0096] ×: Exceeds 600 seconds

[0097] (8) Dielectric constant (Dk) and dielectric loss tangent (Df) of the resin composition

[0098] The dielectric constant (Dk) and dielectric loss tangent (Df) of a plate-shaped molded body (resin composition) of 50 mm × 50 mm × 1 mm were measured at 9.4 GHz using a network analyzer (Anritsu MS46122B) and a coaxial resonator.

[0099] A comparison with a resin composition without hollow particles (fillers) was performed using the following formula, and evaluated according to the following criteria.

[0100] <Formula> Reduction rate (%) of permittivity (Dk) = (Permittivity without filler - Permittivity with filler) / Permittivity without filler × 100

[0101] ○: Reduction rate > 0

[0102] △: Reduction rate = 0

[0103] ×: Reduction rate < 0

[0104] <Formula> Reduction rate (%) of dielectric loss tangent (Df) = (Dielectric loss tangent without filler - Dielectric loss tangent with filler) / Dielectric loss tangent without filler × 100

[0105] ◎: Reduction rate of 50% or more

[0106] ○: Reduction rate 30% or more and less than 50%

[0107] △: Reduction rate 20% or more and less than 30%

[0108] ×: Reduction rate less than 20%

[0109] [Example 2]

[0110] Except for the classification process, hollow particles and plate-shaped resin compositions were prepared in the same manner as in Example 1. In the classification process, dry inertial classification was performed using an elbow jet (EJ-15) manufactured by Nittetsu Kogyo. In this device, the powder can be divided into three types by classification: F powder (fine powder), M powder (fine powder), and G powder (coarse powder). Among these, the F edge distance was adjusted so that the amount of coarse particles contained in the F powder (fine powder) was 5 volume% or less, and the powder was recovered by a bag filter and used in subsequent processes.

[0111] [Example 3]

[0112] In Example 2, the F edge distance was adjusted so that the amount of coarse particles included in the F powder (fine powder) in the classification process was 1 volume% or less. Except for this, a hollow particle and plate-shaped resin composition was prepared in the same manner as in Example 2.

[0113] [Example 4]

[0114] In the classification process, a hollow particle and plate-shaped resin composition was prepared in the same manner as in Example 1, except that dry centrifugal (semi-free vortex) classification treatment was performed using an Aerofine Classifier manufactured by Nissin Engineering. Classification was performed by adjusting the angle of the blade, etc., so that the amount of coarse particles included in the recovered portion was 1 volume% or less.

[0115] [Comparative Example 1]

[0116] A hollow particle and plate-shaped resin composition was prepared in the same manner as in Example 1, except that in the alkali removal process, the immersion stirring time was changed from 15 hours to 1.5 hours and the classification treatment (classification process) was not performed.

[0117] [Comparative Example 2]

[0118] In the hollow particle preparation process, the inlet temperature of the spray dryer was set to 250°C, and a hollow particle and plate-shaped resin composition were prepared in the same manner as in Example 1, except that a classification process was not performed.

[0119] [Comparative Example 3]

[0120] A hollow particle and plate-shaped resin composition was prepared in the same manner as in Example 1, except that the classification process was performed after the firing process (with the same classification conditions).

[0121]

[0122] As shown in Table 1, the hollow particles according to the examples and the resin composition incorporating them can achieve low dielectric constant and low dielectric loss tangent. In addition, the liquid for forming the resin composition incorporating the hollow particles according to the examples has excellent filtration and injection properties.

Claims

Claim 1 A hollow particle having a cavity inside a non-porous outer shell, wherein the outer shell contains 70 mass% or more of silica and has an average particle size (D50) in the range of 0.1 to 10 μm, and when the hollow particle is suspended in water, the suspended particles are 0.5 to 7.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settled particles are 89.0 to 99.5 mass%, and the content of coarse particles exceeding a particle size of 8.0 μm is 10 volume% or less. Claim 2 A resin composition comprising hollow particles as described in claim 1. Claim 3 A method for manufacturing hollow particles, characterized by having a hollow particle preparation process in which hollow particles are prepared by spray-drying an alkali silicate aqueous solution in a hot air stream, an alkali removal process in which alkali contained in the prepared hollow particles is neutralized with an acid to remove it, and a calcination process in which the alkali-removed hollow particles are calcined, and between the hollow particle preparation process and the calcination process, a classification process in which the hollow particles are classified to reduce the content of coarse particles exceeding a particle size of 8.0 μm to 10 volume% or less. Claim 4 A method for manufacturing hollow particles according to claim 3, characterized in that, in the alkali removal process, the amount of alkali contained in the hollow particles is reduced to 200 ppm or less. Claim 5 A method for manufacturing hollow particles according to claim 3, characterized in that the classification process is performed after drying the alkali-removed hollow particles. Claim 6 A method for manufacturing hollow particles, characterized in that, in any one of claims 3 to 5, the classification treatment of the classification process is a dry classification treatment. Claim 7 delete

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