JP2015147714A - Method of producing surface-coated porous ceramic particle, and method of producing insulation material using the particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method enabling a surface-coated porous ceramic particle to be stably produced by 1 step process without causing adhesion of particles together.SOLUTION: The method of producing a surface-coated porous ceramic particle is provided that comprises: spraying to a porous ceramic particle jetted in aerial regions from a tip of a nozzle, a coating liquid composed of a molten-state or solution-state organic material supplied from a flow path other than that of the porous ceramic particle; and blowing gas to the porous ceramic particle to which the coating liquid has been sprayed, thereby drying the coating liquid instantaneously. A method of producing insulation material is also provided that comprises mixing the surface-coated porous ceramic particle obtained by the above method with an epoxy resin, and dispersing the particle in the resin.

Description

  The present invention relates to a method for producing a porous ceramic surface-coated particle in which an organic material is coated on the surface of the porous ceramic particle. The present invention also relates to a method for producing an insulating material using porous ceramic surface coating particles produced according to the present invention.

  Conventionally, porous ceramics have adsorptivity, and thus have been widely used as adsorbents for adsorbing water and gas inside the pores in purification of water and purification of exhaust gas in environmental applications. In recent years, an attempt has been made to adsorb ionic impurities contained in an epoxy resin by containing porous alumina in the epoxy resin composition (for example, Japanese Patent Application Laid-Open No. 2006-206748 (patent). See literature 1)).

  However, when the porous ceramic is contained in the resin as in the invention disclosed in Patent Document 1, the resin enters the pores of the porous ceramic. For this reason, attempts have been made to coat the surface of porous silica with polypropylene by spraying hot-melted polypropylene with a spray nozzle to carry the polypropylene on the surface of the porous silica, and then heat-treating the polypropylene (for example, Japanese Patent Application Laid-Open No. 2004-2004). -311326 (Patent Document 2).

JP 2006-206748 A JP 2004-31326 A

  In the conventional coating method of porous ceramic particles, there is a possibility that the coating material may enter the inside of the pores, and there is a possibility that the particles adhere to each other during the heat treatment. Furthermore, a two-stage process is required, that is, a process for supporting the coating agent and a heat treatment process.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to produce porous ceramic surface-coated particles stably in one step without causing the particles to stick together. It is to provide a way that can be done.

  The method for producing the porous ceramic surface coating particles of the present invention comprises a molten or solution organic material supplied from a flow path different from the porous ceramic particles to the porous ceramic particles injected into the air from the nozzle tip. A coating liquid made of a material is sprayed, and a gas is sprayed onto porous ceramic particles onto which the coating liquid is sprayed to dry the coating liquid instantaneously.

  The organic material in the method for producing porous ceramic surface coating particles of the present invention preferably contains polyvinyl butyral, polyvinyl alcohol, polyethylene, polypropylene, polybutene, nylon, acetylcellulose, or polylactic acid.

  The porous ceramic particles in the method for producing porous ceramic surface coating particles of the present invention are preferably porous alumina particles or porous silica particles.

  The porous ceramic particles in the method for producing porous ceramic surface coating particles of the present invention preferably have a pore size of 1 μm or less and a particle size of less than 300 μm.

  This invention also provides the manufacturing method of the insulating material which mixes and disperse | distributes the porous ceramic surface coating particle obtained by the manufacturing method of the porous ceramic surface coating particle of this invention mentioned above with an epoxy resin.

  According to the present invention, the coating material does not penetrate into the pores of the porous ceramic particles, and only the surface can be coated while leaving the air component inside the porous ceramic particles, and the particles adhere to each other. An unprecedented new method for producing porous ceramic surface coating particles can be provided without any fear.

It is a figure which shows typically a preferable example of the manufacturing method of the porous ceramic surface coating particle of this invention. It is a figure which shows typically the porous ceramic particle 3 before coating. It is a figure which shows typically the porous ceramic surface coating particle 11. FIG. It is a figure which shows typically the insulating material 21 manufactured using the porous ceramic surface coating particle 11 obtained by this invention. It is a figure which shows typically the insulating material formed using the porous ceramic particle | grains 3 and the epoxy resin 22 which are not forming the coating layer unlike this invention.

  The method for producing the porous ceramic surface coating particles of the present invention comprises a molten or solution organic material supplied from a flow path different from the porous ceramic particles to the porous ceramic particles injected into the air from the nozzle tip. A coating liquid made of a material is sprayed, and a gas is sprayed onto porous ceramic particles onto which the coating liquid is sprayed to dry the coating liquid instantaneously. Here, FIG. 1 is a diagram schematically showing a preferred example of the method for producing porous ceramic surface coating particles of the present invention. As shown in FIG. 1, the method for producing porous ceramic surface coating particles of the present invention includes a flow path 4 for supplying porous ceramic particles 3, a flow for supplying a coating liquid 5 made of a molten or solution organic material. The path 6, the flow path 8 for supplying the gas 7, the porous ceramic particles 3 from the flow path 4, the coating liquid 5 from the flow path 6, and the gas 7 from the flow path 8 are ejected from the jet outlet 2a at the tip thereof. A raw material separation supply type spray drying apparatus 1 provided with a nozzle 2 is preferably used. In the present invention, the flow path 4 for supplying the porous ceramic particles 3, the flow path 6 for supplying the coating liquid 5, and the flow path 8 for supplying the gas 7 may be different flow paths. As in the example shown, it is preferable that the flow path 6 is provided around the flow path 4, and the flow path 8 is further provided around the flow path 6.

  In the example shown in FIG. 1, the porous ceramic particles 3 ejected from the ejection port 2 a and the coating liquid 5 are designed to join at the joining point 9, and when joined, from the outside of the joining point 9. A gas 7 ejected from the ejection port 2a is ejected, and the coating liquid is instantly dried. In the present invention, since the coating liquid sprayed on the surface of the porous ceramic particles is dried instantaneously, the coating liquid does not enter the pores of the porous ceramic particles, It is possible to coat only the surface.

  Here, FIG. 2 is a diagram schematically illustrating the porous ceramic particles 3 before coating, and FIG. 3 is a schematic diagram of the porous ceramic particles (porous ceramic surface coating particles) 11 from which the coating liquid has been dried. FIG. The porous ceramic particles 3 before coating used in the present invention can have pores 12 observed on the surface thereof as shown in FIG. On the other hand, as shown in FIG. 3, the coated porous ceramic surface coating particles 11 have a coating layer 13 formed on the surface thereof, and the coating liquid does not enter the pores 12 of the porous ceramic particles 3, Coating can be performed while air remains inside the porous ceramic particles 3.

  In the example shown in FIG. 1, the porous ceramic particles (porous ceramic surface coating particles) 11 from which the coating liquid has been dried further fall and accumulate in the tray 10. Since the porous ceramic surface coating particles 11 are dry, the porous ceramic surface coating particles 11 do not stick to each other in the tray 10.

  In the present invention, the flow path 4 for supplying the porous ceramic particles 3 and the flow path 8 for supplying the gas 7 are preferably configured to work at the same pressure. Thereby, the thickness of the coating layer 13 on the surface of the produced porous ceramic surface coating particles 11 can be adjusted by adjusting the pressure of the flow path 4 and the flow path 8 and the speed of supplying the coating liquid. It becomes.

  As the porous ceramic particles 3 used in the present invention, porous alumina particles, porous silica particles, porous silicon carbide particles, and the like can be used. Among these, because they are familiar with the coating material, Preferably, the particles are porous alumina particles or porous silica particles.

  The porous ceramic particles 3 used in the present invention preferably have a pore diameter of 1 μm or less. This is because if the porous ceramic particles 3 having a pore diameter exceeding 1 μm are used, it may be difficult to perform coating that does not allow the coating liquid to enter the pores of the porous ceramic particles. From the viewpoint of making it difficult for the coating liquid to penetrate into the pores, the pore diameter of the porous ceramic particles 3 is more preferably 400 nm or less. In addition, if the pore diameter is too small, the penetration speed of the coating material into the pores due to capillary action increases, and therefore the pore diameter of the porous ceramic particles 3 is preferably 30 nm or more. The pore diameter of the porous ceramic particles 3 refers to an average value of the size of 100 or more pores by directly observing the size of 100 or more pores using, for example, SEM.

  The porous ceramic particles 3 used in the present invention preferably have a particle size of less than 300 μm. It is because there exists a possibility that it may become impossible to supply sufficient coating liquid for coating the whole porous ceramic particle as the particle diameter of a porous ceramic particle is 300 micrometers or more. The porous ceramic particles preferably have a particle diameter of 200 μm or less because the porous ceramic particles are coated on the entire particle surface. Moreover, if the particle diameter of the porous ceramic particles is too small, the particles are likely to aggregate together, and therefore the particle diameter of the porous ceramic particles 3 is preferably 10 μm or more. The particle diameter of the porous ceramic particles 3 refers to an average value of the sizes of 100 or more particles by directly observing the size of 100 or more particles using, for example, SEM.

  In the porous ceramic surface coating particles 11 produced by the method of the present invention, the thickness of the coating layer 13 is preferably 0.1 μm or more, and more preferably 1 μm or more. When the thickness of the coating layer 13 is less than 0.1 μm, since the coating layer 13 is thin, when the porous ceramic surface coating particles 11 and the epoxy resin are mixed as described later, the epoxy resin is coated with the coating layer 13. This is because 13 may be destroyed and the epoxy resin may penetrate into the pores of the porous ceramic particles 3. Moreover, the thickness of the coating layer 13 is preferably 6 μm or less, and more preferably 4 μm or less, because if the coating layer is too thick, the coating layer cannot be dried sufficiently. The thickness of the coating layer 13 is determined by, for example, performing cross-sectional SEM observation of the porous ceramic surface coating particles and directly observing the thickness of the coating layer from 100 or more particles. Refers to the average thickness.

  In the present invention, since the coating liquid can be supplied in a molten state or a solution state, the coating liquid is not particularly limited as long as it is an organic material in a molten state or a solution state. Since the viscosity is suitable, it is preferable to use a coating solution containing polyvinyl butyral, polyvinyl alcohol, polyethylene, polypropylene, polybutene, nylon, acetylcellulose, or polylactic acid as the organic material used for the coating solution. Among these, polyvinyl butyral is particularly preferable because it can be easily adapted to the surface of the porous alumina particles.

  When a coating solution in a solution state is used, the solvent is not particularly limited, and examples thereof include ethanol, 1-propanol, N-pentyl alcohol and the like. Among these, it is preferable to use ethanol because it is easy to dry. Moreover, when using the coating liquid of a solution state, the density | concentration is not specifically limited, However, It is preferable that it is 3 weight% or more, and it is more preferable that it is 5 weight% or more. When the concentration of the coating solution in the solution state is less than 3% by weight, the amount of organic material is small, and thus the coating layer may become thin when the surface of the porous ceramic particles is coated. It is. In addition, the concentration of the coating liquid in the solution state is preferably 40% by weight or less, and preferably 20% by weight or less, because if the viscosity of the solution is too high, it becomes difficult to spray the coating liquid. More preferred.

  FIG. 4 is a diagram schematically showing an insulating material 21 manufactured using the porous ceramic surface coating particles 11 obtained in the present invention. FIG. 5 is a diagram schematically showing an insulating material formed using the porous ceramic particles 3 and the epoxy resin 22 which are not formed with a coating layer unlike the present invention. The present invention also provides a method for manufacturing the insulating material 21 in which the porous ceramic surface coating particles 11 manufactured by the above-described method of the present invention are mixed and dispersed with the epoxy resin 22. Conventionally, it is known that a composite material composed of an alumina filler and an epoxy resin is applied as an insulating material. However, while the dielectric constant of epoxy resin is 4.2, the dielectric constant of alumina is as high as 9.3, so it has been difficult in the past to reduce the dielectric constant of the composite material to 5.0 or less. there were. Therefore, an attempt was made to apply porous alumina having air (dielectric constant: 1.0) inside the pores instead of alumina, but the epoxy resin entered into the pores of the porous alumina, resulting in pores. Lowering the dielectric constant becomes difficult because the air inside is lost. On the other hand, the porous ceramic surface coated particles 11 produced by the method of the present invention, as described above, do not enter the pores of the porous ceramic particles and the surface of the porous ceramic particles only. It is a coated one. Therefore, in the method for producing an insulating material of the present invention using such porous ceramic surface coating particles 11, an insulating material capable of greatly reducing the dielectric constant, reducing the electric field strength, and improving the insulating performance is obtained. Can be manufactured. When the insulating material manufactured by such a method of the present invention is applied to an insulating member of a gas circuit breaker, for example, the busbar portion can be reduced in size.

  The specific procedure of the method for producing an insulating material of the present invention may be any conventionally known appropriate procedure except that the porous ceramic surface coating particles 11 obtained by the method of the present invention are used. For example, first, the main component of the epoxy resin is heated, and the porous ceramic surface coating particles 11 preheated to a temperature equivalent to the heating temperature of the main component of the epoxy resin are put therein and mixed while being uniformly dispersed. Thereafter, a curing agent is added and mixed while further uniformly dispersed, and then deaerated in a vacuum, for example, in order to remove air in the epoxy resin. Thereafter, the insulating material 21 as shown in FIG. 4 can be manufactured by molding and curing the epoxy resin.

  The mixing ratio of the porous ceramic surface coating particles 11 and the epoxy resin 22 used for the production of the insulating material 21 is not particularly limited, but is preferably in the range of 1: 9 to 8: 2 by weight. More preferably, it is in the range of 6-7: 3. The insulating material obtained in the present invention is porous without the epoxy resin 22 entering the pores of the porous ceramic surface coating particles 11 regardless of the mixing ratio of the porous ceramic surface coating particles and the epoxy resin. Air in the pores of the porous ceramic particles 3 is retained, and the insulating material 21 having the low dielectric constant as described above can be manufactured.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
1 is used to supply porous alumina particles having a pore size of 10 to 60 nm and a particle size of 40 to 80 μm to the flow path 4 and dissolved in ethanol as a coating solution 5 To prepare a solution of each concentration (2.0 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, 10 wt%, 20 wt% or 30 wt%) Butyral was supplied to the channel 6. Moreover, both the pressure of the flow path 4 for supplying porous alumina particles and the pressure of the flow path 8 for supplying gas (gas supply pressure) are 1.0 MPa, and the supply speed of the coating liquid 5 is 1. 0 ml / min. In this way, porous ceramic surface coated particles in which the surface of the porous alumina particles was coated with polyvinyl butyral were produced.

  When the obtained porous ceramic surface coating particles were observed with a scanning electron microscope (JXA-8230, manufactured by JEOL Ltd.), it was possible to observe the aspect in which the surfaces of the porous alumina particles were coated with polyvinyl butyral. Moreover, when the obtained porous ceramic surface coating particles are observed by a cross-section with an electron beam microanalyzer (JXA-8230, manufactured by JEOL Ltd.), the surface of the porous alumina particles does not enter the pores of the porous alumina particles. Only the presence of polyvinyl butyral was observed. Furthermore, when the thickness of the polyvinyl butyral layer (coating layer) that coats the porous alumina surface is determined by cross-sectional observation, it can be observed that the greater the polyvinyl butyral concentration is, the greater the coating layer thickness is, as shown in Table 1. It was.

  Next, the concentration of polyvinyl butyral is fixed to 5% by weight, the gas supply pressure and the coating liquid supply speed in the raw material separation supply type spray drying apparatus 1 are changed, and the coating layer of the obtained porous ceramic surface coating particles The thickness was measured. The results are shown in Table 2.

  As shown in Table 2, the thickness of the coating layer increased as the gas supply pressure decreased. Moreover, it turned out that the thickness of a coating layer becomes large, so that a coating liquid supply rate is large.

<Example 2>
Porous ceramic surface-coated particles (pore size as in Example 1) were heated to 130 ° C. in the epoxy resin main component (bisphenol A type epoxy resin EP-4100, manufactured by ADEKA Corporation) and previously heated to 130 ° C. Was formed on the surface of porous alumina particles having a particle diameter of 10 to 60 nm and a particle diameter of 40 to 80 μm, and a 1 μm-thick coating layer was formed with polyvinyl butyral. The mixing ratio was 50% by weight of epoxy resin with respect to 50% by weight of porous ceramic surface coating particles. Thereafter, a curing agent (MHAC-P, manufactured by Hitachi Chemical Co., Ltd.) was added, followed by heating at a rotation speed of 70 rpm for 10 minutes. Next, in order to remove the air in the epoxy resin, vacuum deaeration was performed for 1 minute, and after that, molding was performed and curing was performed at 130 ° C. for 12 hours to produce an insulating material as shown in FIG. Moreover, the insulating material as shown in FIG. 5 was similarly formed using the porous alumina particle | grains which have not formed the coating layer. About each obtained insulating material, when the dielectric constant was measured using 4192A LF IMPEDANCE ANALYZER (made by Yokogawa Hewlett-Packard Co.), it was 6.0 with the insulating material shown in FIG. In the insulating material shown in FIG. 4, the dielectric constant was lowered to 4.5.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Raw material separation supply type spray drying apparatus, 2 nozzle, 2a spout, 3 porous ceramic particle, 4 flow path, 5 coating liquid, 6 flow path, 7 gas, 8 flow path, 9 junction, 10 saucer, 11 porous Ceramic surface coating particles, 12 pores, 13 coating layer, 21 insulating material, 22 epoxy resin.

Claims (5)

  A coating liquid made of an organic material in a molten state or a solution state supplied from a flow path different from the porous ceramic particles is sprayed onto the porous ceramic particles injected into the air from the nozzle tip, and the coating liquid is A method for producing porous ceramic surface coating particles, wherein a gas is sprayed onto the sprayed porous ceramic particles to instantaneously dry the coating liquid.   The method for producing porous ceramic surface-coated particles according to claim 1, wherein the organic material contains polyvinyl butyral, polyvinyl alcohol, polyethylene, polypropylene, polybutene, nylon, acetylcellulose, or polylactic acid.   The method for producing porous ceramic surface-coated particles according to claim 1 or 2, wherein the porous ceramic particles are porous alumina particles or porous silica particles.   The said porous ceramic particle is a manufacturing method of the porous ceramic surface coating particle in any one of Claims 1-3 whose pore diameter is 1 micrometer or less and whose particle diameter is less than 300 micrometers.   The manufacturing method of the insulating material which mixes and disperse | distributes the porous ceramic surface coating particle obtained by the method in any one of Claims 1-4 with an epoxy resin.

Images