JP2009274934A - Method of manufacturing ceramic hollow particle, and ceramic hollow particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing ceramic hollow particles, easy to carry out, reducible in use amount of resin molds, containing no unnecessary component, capable of manufacturing the ceramic hollow particles by mass production. <P>SOLUTION: The method of manufacturing ceramic hollow particles is provided with a dispersion phase preparing process for obtaining a dispersion phase liquid formed by adding water and ceramic particles made hydrophobic to an organic solvent solution of polystyrene and dispersing them, an emulsion preparing process for obtaining an emulsion formed by dispersing the dispersion phase liquid in water, a particle forming process for obtaining polystyrene-ceramic hollow particles comprising polystyrene and ceramics by removing the solvent from the emulsion to dry it, and a baking process for obtaining the ceramic hollow particles by heating the polystyrene-ceramic hollow particles in an oxidation atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing ceramic hollow particles which can be added to a resin material or the like as a filler and can give various functions to a base material, and ceramic hollow particles.

  Development of fillers that are added to resin materials and the like to impart various functions to the base material is underway. Among these, ceramic hollow particles capable of imparting characteristics such as low dielectric constant, low thermal conductivity, and light weight are expected to be applied in various fields. However, most of the ceramic-based hollow particles currently on the market require a complicated preparation process, an expensive apparatus or a large amount of resin mold in production, and as a result, are not suitable for mass production.

  On the other hand, silica-based hollow particles made of volcanic glassy resources such as shirasu balloons that do not require complicated preparation processes or equipment contain a large amount of unnecessary components in the molded product, and control of heating and foaming is possible. Since it is difficult, there is a problem that quality such as wall thickness is not stable. Furthermore, most of these hollow particles exhibit a wide particle size distribution and have a problem that the application range is limited.

There are various methods for preparing ceramic hollow particles depending on materials and applications. That is, a melt spraying method in which high-pressure air is blown to the molten ceramic, a heating foaming method by foaming of a foaming component, a ceramic layer is coated on the surface of a resin having a low melting point, and the core material is removed at the same time as heating and firing to form a hollow Represented by core material melting / elution method, nozzle droplet method, spray pyrolysis method, and interfacial reaction method, advanced technology and complicated equipment are required, and quality control is difficult, making it easy and mass production. It is hard to say that suitable technology has been established. In particular, the melt elution method (Patent Document 1) has a problem that a large amount of a resin mold is required and the material cost is high, and the spray pyrolysis method (Patent Documents 2 to 4) makes it difficult to perform mass production. There are problems.
JP 2003-160330 A JP 2003-89519 A JP 2003-160331 A JP 2005-126309 A

  The present invention improves the above-mentioned conventional problems, that is, a method for producing ceramic hollow particles that can be carried out easily, reduce the amount of resin mold used, do not contain unnecessary components, and can be mass-produced The purpose is to provide.

  In order to solve the above problems, the method for producing ceramic hollow particles of the present invention has a diffusion phase in which water and hydrophobic ceramic particles are added and dispersed in an organic solvent solution of polystyrene as described in claim 1. A diffusion phase preparation step for obtaining a liquid, an emulsion preparation step for obtaining an emulsion by dispersing the diffusion phase liquid in water, particles for obtaining polystyrene-ceramic hollow particles comprising polystyrene and ceramics by removing the solvent from the emulsion and drying the emulsion. A method for producing ceramic hollow particles, comprising a forming step and a firing step of heating the polystyrene-ceramic hollow particles in an oxidizing atmosphere to obtain the ceramic hollow particles.

  Moreover, the manufacturing method of the ceramic hollow particle of this invention is a manufacturing method of the ceramic hollow particle of Claim 1 as described in Claim 2, A polymer dispersion stabilizer is in the said water used at the said emulsion preparation process. It is characterized by being added.

  Moreover, the ceramic hollow particle of the present invention is a ceramic hollow particle produced by the method for producing a ceramic hollow particle according to claim 1 or 2.

  The method for producing ceramic hollow particles of the present invention is an excellent method for producing ceramic hollow particles that can be carried out simply, reduces the amount of resin mold used, does not contain unnecessary components, and enables mass production.

  Further, according to the method for producing ceramic hollow particles according to claim 2, since a polymer dispersion stabilizer is added to the water used in the emulsion preparation step, the droplets in the formed emulsion Dispersion is stabilized, and variation in the size of the finally obtained ceramic hollow particles is reduced.

  In the present invention, in the diffusion phase preparation step, a diffusion phase liquid is obtained in which water and hydrophobic ceramic particles are added and dispersed in an organic solvent solution of polystyrene. This is shown as a model in the diffusion phase preparation step in FIG. In the figure, reference numeral 1 is water, and the state immediately before being poured into the polystyrene organic solvent solution 2 in which the ceramic particles 3 are dispersed and after the diffusion phase preparation step, the ceramic particles 3 and the water 1 are added to the polystyrene organic solvent solution 2. Indicates a distributed state.

  As the organic solvent to be used, any solvent that dissolves polystyrene and is insoluble in water may be used. Examples include dichloromethane, chloroform, carbon tetrachloride, benzene, toluene, xylene, cyclohexane, methylcyclohexane, ethylcyclohexane, and the like. It can also be mixed and used as needed.

  The polystyrene used may be a commercially available one (pellet-shaped one), and may be dissolved in the organic solvent after being powdered as necessary. Upon dissolution, stirring, heating, or the like may be performed as necessary. If the viscosity of the diffusive phase is too high, stable spherical droplets cannot be formed in the emulsion adjustment process, so the amount of polystyrene, ceramic powder and solvent added can be adjusted to form stable spherical droplets. Adjust the viscosity of the diffusion phase. At this time, considering that polystyrene is removed in a later step, it is preferable that the amount of polystyrene added is as small as possible. In the present invention, since polystyrene is used as a binder for ceramics in this way, the polystyrene-ceramic hollow particles obtained in the particle forming step have high strength even before firing, and are very unlikely to break. Hollow particles can be obtained efficiently.

  The hydrophobic ceramic used may be a commercially available hydrophobic ceramic particle (for example, hydrophobic alumina is available from Nippon Aerosil Co., Ltd.) or a surface-modified hydrophobized ceramic with a hydrophobizing agent. It may be used. Here, as the hydrophobizing agent, a fatty acid, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a silicone oil, and the like can be raised, and one or more kinds are selected and used.

  Although it does not specifically limit as a silane coupling agent, For example, a vinyl ethoxysilane, vinyl tris (2-methoxysilane) silane, (gamma) -methacryloxypropyl trimethoxysilane, (gamma) -aminopropyl trimethoxysilane, (beta) -(3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and the like can be raised. Such a silane coupling agent is usually used in a range of 0.1 wt% to 5 wt%, preferably 0.3 wt% to 1 wt%, with respect to the hydrophilic ceramic particles.

  In addition, since the purpose is hydrophobicity, a coupling agent other than the silane coupling agent, for example, a titanate coupling agent or an aluminum coupling agent can be used in the same manner as the silane coupling agent.

  In addition, since the fatty acid is used for hydrophobization, it is necessary that the fatty acid does not dissolve in a large amount in water. For example, butyric acid, valeric acid, butyric acid, valeric acid, capron Acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecyl acid, stearic acid, margaric acid, aragylic acid, behenic acid, lignoceric acid, undecylic acid, One or more selected from nonadecanoic acid, arachidic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, sorbic acid, arachidonic acid, linoleic acid, linolenic acid, and the like, which may be saturated or unsaturated, Saturated or unsaturated higher fatty acids having 14 to 24 carbon atoms are preferred, If, it can be exemplified oleic acid and stearic acid. Such fatty acids are usually used in the range of 0.5 wt% to 5 wt%, preferably 1 wt% to 3 wt%. Moreover, the salt of the said fatty acid can also be used.

  Silicone oils can also be used as a hydrophobizing agent, and examples thereof include methyl hydrogen polysiloxane.

  Among these hydrophobizing agents, a coupling agent is reacted with ceramic particles under the coupling reaction conditions, and subjected to a surface treatment to be hydrophobized. For other hydrophobizing agents, the hydrophobizing treatment is performed under the condition that these hydrophobizing agents are satisfactorily applied to the ceramic particle surface.

Here, non-metallic inorganic materials BaTiO ₃ , Ba ₂ NaNbO ₁₅ , PbZrO ₃ , PbTiO ₃ , PZT (lead zirconate titanate (solid solution of PbZrO ₃ and PbTiO ₃ )), PLZT (PZT with La added) Metal oxide), LiTaO ₃ , LiNbO ₃ , CaO, CaAs, CaWO ₄ , Bi ₂ O ₃ , Bi ₄ (GeO ₄ ) ₃ , SiO ₂ , SiC, Si ₃ N ₄ , ZnO, ZnS, ThO ₂ , K ₂ O, LaCrO ₃ , SnO ₂ , ZrO ₂ , LaB ₆ , BeO, WC, B ₄ C, In ₂ O ₃ , TiN, TiO ₂ , TiC, LaF ₃ , Y ₂ O ₂ S, Y ₃ Al ₅ O ₁₂ , YIG (yttrium iron garnet 3Y ₂ O ₃ .5Fe ₂ O ₃ ), HAp (Ca ₁₀ (PO ₄ ) ₆ (O _{H) 2 hydroxyapatite), TCP (Ca 3 (PO} 3) 2 tricalcium _{phosphate), TTCP (Ca 4 O (} PO 3) 2 tetracalcium phosphate), vanadium oxides such as VO and _V 2 _{O 3,} Examples thereof include iron group oxides such as Fe ₂ O ₃ and ferrite.

  On the other hand, if the size of the ceramic particles used is too small, a large number of aggregates are generated in the diffusion phase and workability is deteriorated. On the other hand, if the size is too large, sedimentation occurs in the diffusion phase and the dispersibility decreases. Therefore, it is usually preferable to use a film having a thickness of 0.01 μm to 10 μm.

  Hydrophobized ceramic particles are uniformly dispersed in an organic solvent solution of polystyrene. At this time, the organic solvent solution of polystyrene can be gradually added with stirring using a stirrer or a mixer. preferable. The amount of the ceramic particles hydrophobized is in the range of 5 to 1000 parts by weight with respect to 100 parts by weight of polystyrene to affect the shape and stability of the droplets in the emulsion. It is preferable to do. A more preferable range is 10 parts by weight or more and 200 parts by weight or less.

  A diffusion phase liquid is obtained in which water and hydrophobic ceramic particles are added and dispersed in the organic solvent solution of polystyrene thus obtained. The amount of water added at this time is one of the parameters that determine the size of the hollow portion of the resulting hollow particles. If the amount added is too small, solid particles rather than hollow particles increase, and the amount added is large. If too much, an emulsion cannot be formed. For this reason, it is preferable to add water so that it may become the range of 1 volume% or more and 30 volume% or less with respect to a diffusion phase. Further, it is preferable to add while stirring with a stirrer or a mixer so that the water particles are sufficiently uniformly diffused. Furthermore, when a polymer dispersion stabilizer is added to the water at this time, aggregation (unification) of water in the diffusion phase is prevented, and dispersion in the diffusion phase is stabilized. By the addition of the polymer dispersion stabilizer, water is stably present in the droplets of the emulsion to be molded, and the finally obtained ceramic particles become a hollow body with a high probability.

  In this way, in the diffusion phase preparation step, a diffusion phase is formed in which water particles are diffused in an organic solvent solution of polystyrene in which hydrophobic ceramic particles are added and dispersed. At this time, since the ceramic particles are hydrophobized, they do not approach the water particles and the water phase, and exist in an organic solvent solution of polystyrene.

  Next, an emulsion preparation step is performed in which the diffusion phase liquid is dispersed in water to obtain an emulsion. In FIG. 1, emulsion particles 5 are formed immediately after the organic solvent solution 2 of polystyrene in which water 1 and hydrophobic ceramic particles 3 are diffused, and after the emulsion preparation step. It is modeled that water molecules are dispersed in an organic solvent solution of polystyrene in which the hydrophobic ceramic particles 3 are dispersed in the particles 5.

  It is preferable to add a polymer dispersion stabilizer to the water used here because the dispersion becomes stable. Examples of the polymer dispersion stabilizer used include polyvinyl alcohol and polyvinyl pyrrolidone. The concentration of these polymer dispersion stabilizers in water should be 0.5 to 3 parts by weight with respect to 100 parts by weight of water in order to obtain a dispersion stabilizing effect. Is preferred.

  The diffusion phase liquid is dispersed in the water thus prepared. At this time, if the amount of the diffusion phase liquid is too much with respect to water, the opportunity for the diffusion phase liquids to come into contact with each other increases, and the possibility of becoming an aggregate increases even in the presence of the polymer dispersion stabilizer. For this reason, the diffusion phase liquid is 30 parts by weight or less, preferably 10 parts by weight or less with respect to 100 parts by weight of water. In addition, using a stirrer, a mixer (rotary blade, homomixer), etc., stir (suspend) until an appropriate droplet size is obtained, and continue stirring to maintain a good dispersion state of the droplets. .

  At this time, by keeping the emulsion at an appropriate temperature, the solvent in the droplets is removed by evaporation, polystyrene is precipitated, and the droplets are solidified. Also, the solvent vapor can be recovered and reused. In this way, polystyrene-alumina particles composed of polystyrene and alumina having water inside are formed.

  In such an emulsion preparation process, liquid particles made of an organic solvent solution of polystyrene having water particles inside and hydrophobized ceramic particles added and dispersed therein are dispersed in water. Furthermore, in this emulsion preparation step, stirring is performed to form an emulsion, and this stirring is an important factor for determining the outer diameter of the finally obtained ceramic hollow particles.

  In addition, since the organic solvent solution of polystyrene in the liquid particles has water molecules inside, the amount of polystyrene required is smaller than the size of the liquid particles, compared to the conventional core melting and elution method. However, since the required amount is reduced, the cost can be finally reduced.

Next, the particles are separated from the emulsion, the polymer dispersion stabilizer physically adsorbed on the particle surface is removed, and then the particles are dried to remove the water in the interior, thereby removing polystyrene-alumina hollow particles composed of polystyrene and alumina. The resulting particle formation step is performed.
FIG. 1 schematically shows that emulsion particles 5 dispersed in water 4 are taken out of water after the particle formation step.

  The particles are separated by means such as filtration or centrifugation. Thereafter, the polymer dispersion stabilizer physically adsorbed on the particle surface is washed with water at about 80 ° C.

  In this particle forming step, water is removed to form polystyrene-ceramic hollow particles (polystyrene-ceramic hollow particles 5 'in FIG. 1). At this time, the polystyrene component functions as a binder for holding the ceramic particles in a larger hollow particle shape.

  Thereafter, a firing step is performed in which the polystyrene-ceramic hollow particles are heated in an oxidizing atmosphere to obtain ceramic hollow particles. FIG. 1 schematically shows that the polystyrene component is removed from the polystyrene-ceramic hollow particles 5 ′ by the firing process to form the ceramic hollow particles 6.

  By this firing, the polystyrene component is burned and removed, and the remaining ceramic particles are bonded together to obtain hollow particles made of ceramics. Usually, air is used as the oxidizing atmosphere, but the oxidizing conditions may be adjusted by mixing nitrogen or the like as necessary.

  As the firing temperature, while the polystyrene-ceramic hollow particles finally maintain a hollow shape, adjacent ceramic particles in the hollow particles are fused with each other to be in a sintered state, or not sintered. It is necessary that the temperature is such that they are partially bonded to each other. For example, the temperature is preferably in the range of 1400 ° C. to 1800 ° C.

  As described above, the only necessary equipment for this production method is a container for various solutions, a thermostatic bath, a stirrer or mixer for stirring, and an electric furnace, which is a process that is very simple and easy to expand.

  Furthermore, since the particle size is controlled by the size of the emulsion depending on the stirring force in the emulsion preparation process, there is less variation in the particle size compared to a method that requires a foam material. Moreover, by adjusting the amount of water in the diffusion phase preparation step, it is excellent in applicability such as reduction of the amount of polystyrene used and control of the wall thickness.

  Examples of the method for producing ceramic hollow particles of the present invention will be specifically described below.

<Diffusion phase preparation process>
Hydrophobized alumina particles (AluC805 manufactured by Nippon Aerosil Co., Ltd., particle size: while stirring with a stirrer in a dichloromethane solution of polystyrene obtained by dissolving 10 g of polystyrene (n = 2500 products) manufactured by Wako Pure Chemical Industries, Ltd. in 60 g of dichloromethane. 15 g) 3 g and water (distilled ion-exchanged water) 5 g were added in this order and dispersed uniformly to obtain a diffusion phase liquid.

<Emulsion preparation process>
The diffusion phase solution obtained above was poured into a solution in which 12 g of polyvinyl alcohol was added and dissolved in 900 mL of water while stirring at 100 rpm with a mixer (stirrer blade), and then continuously stirred for 240 minutes. Evaporation and removal were performed to obtain polystyrene-alumina particles composed of polystyrene and alumina having water inside.

<Particle formation process>
The particles in the emulsion were separated and collected by vacuum filtration, washed sufficiently with warm water at 80 ° C., and then dried in a drying furnace at 40 ° C. for 3 hours to obtain polystyrene-alumina hollow particles composed of polystyrene and alumina. . A micrograph of the obtained polystyrene-alumina hollow particles with a scanning electron microscope is shown in FIG. 2 (a), and a micrograph of the polystyrene-alumina hollow particles broken by compression so that the hollow portion can be confirmed is shown in FIG. Shown in (b).

<Baking process>
The polystyrene-alumina hollow particles were baked (in air) at 1600 ° C. for 3 hours in an electric furnace to obtain alumina hollow particles.

FIG. 2 (c) shows a microscopic photograph of the obtained hollow alumina particles by a scanning electron microscope and a partially enlarged photograph of the surface thereof. The hollow alumina particles are broken by compression so that the hollow portion can be confirmed. A photomicrograph is shown in FIG. From these photographs, it can be confirmed that the obtained alumina hollow particles are uniform and have true spherical hollow particles. The enlarged photograph in FIG. 2 (c) is pores formed on the particle surface,
It is considered that the open pores formed when the internal water evaporates remain even after the baking treatment.

It is the figure which showed the manufacturing method of the ceramic hollow particle of this invention in model. (A) It is a scanning electron micrograph which shows the polystyrene-alumina hollow particle obtained in the Example. (B) It is a scanning electron micrograph which shows the state which fractured | ruptured the particle | grains of (a). (C) It is a scanning electron micrograph which shows the alumina hollow particle obtained in the Example. (D) It is a scanning electron micrograph which shows the state which fractured | ruptured the particle | grains of (b).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water 2 Organic solvent solution of polystyrene 3 Hydrophobized ceramic particle 4 Water 5 Emulsion particle 5 'Polystyrene-alumina hollow particle 6 Alumina hollow particle

Claims (3)

A diffusion phase preparation step for obtaining a diffusion phase liquid in which water and hydrophobic ceramic particles are added and dispersed in an organic solvent solution of polystyrene,
An emulsion preparation step of obtaining an emulsion by dispersing the diffusion phase liquid in water;
Particle formation step of removing the solvent from the emulsion and drying to obtain polystyrene-ceramic hollow particles comprising polystyrene and ceramics, and
A method for producing ceramic hollow particles, comprising a firing step of heating the polystyrene-ceramic hollow particles in an oxidizing atmosphere to obtain the ceramic hollow particles.   The method for producing ceramic hollow particles according to claim 1, wherein a polymer dispersion stabilizer is added to the water used in the emulsion preparation step.   A ceramic hollow particle produced by the method for producing a ceramic hollow particle according to claim 1.