JP2015131739A - Surface-coated porous ceramic particle, production method of the same, and insulation material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a composite material achieving both of the low dielectric constant and the high elastic modulus.SOLUTION: There are disclosed: a surface-coated porous ceramic particle which includes a porous ceramic particle, and a coating film covering the surface of the porous ceramic particle and having holes not penetrating to the surface of the porous ceramic particle; as well as a surface-coated porous ceramic particle which includes a porous ceramic particle containing air inside and a coating film covering the surface of the porous ceramic particle and having holes not penetrating to the surface of the porous ceramic particle; and an insulation material consisting of a composite material of the surface-coated porous ceramic particle and a resin.

Description

  The present invention relates to surface-coated porous ceramic particles in which the surface of porous ceramic particles is covered with a coating film, a method for producing the same, and an insulating material using the same.

  Conventionally, since porous ceramic particles have adsorption properties, they have been widely used for purification of water and purification of exhaust gas in environmental applications. In such a case, the porous ceramic particles have been used as an adsorbent for adsorbing water and gas inside the pores. In recent years, attempts have been made to adsorb ionic impurities contained in an epoxy resin by containing porous alumina particles in the epoxy resin composition (for example, JP-A-2006-206748). (See Patent Document 1)).

  However, when porous ceramic particles are contained in such a resin, the resin enters into the pores of the porous ceramic particles. Therefore, the porous particle surface is dispersed with the silicone compound by dispersing the porous particles in the polymer silicone compound and then pouring a poor solvent into the silicone compound to adhere the silicone compound to the particle surface and forming the film. Attempts have also been made to coat (see, for example, JP-A-63-113081 (Patent Document 2)).

  In another document, an attempt is made to coat the surface of the porous silica with polypropylene by spraying polypropylene melted on the surface with a spray nozzle, supporting the polypropylene on the surface of the porous silica, and then performing heat treatment. (For example, refer to Japanese Unexamined Patent Application Publication No. 2004-311326 (Patent Document 3)).

JP 2006-206748 A JP-A-63-113081 JP 2004-31326 A

  However, the composite technique as in Patent Document 1 has a problem that it is difficult to lower the dielectric constant of the composite material because the epoxy resin enters the pores of the porous ceramic particles as described above. It was.

  In addition, in the coating methods such as Patent Documents 2 and 3, since the hole is not seen on the surface of the coating material and there are few irregularities, the anchor effect of the epoxy resin is obtained when trying to combine with a resin such as an epoxy resin. Therefore, the adhesion with the porous ceramic particles is poor, the elastic modulus of the composite material is insufficient, and there is a problem that it is easily deformed.

  The present invention has been made in view of the above problems, and an object of the present invention is to stably obtain a composite material having both a low dielectric constant and a high elastic modulus.

  The surface-coated porous ceramic particle of the present invention comprises a porous ceramic particle containing air inside, and a coat film having a hole that covers the surface of the porous ceramic particle and does not penetrate to the surface of the porous ceramic particle. It is characterized by providing.

  The present invention also provides a surface-coated porous ceramic comprising porous ceramic particles containing air therein and a coating film that covers the surface of the porous ceramic particle and has a hole that does not penetrate to the surface of the porous ceramic particle. An insulating material composed of a composite material of particles, the surface-coated porous ceramic particles and a resin is also provided.

  In the surface-coated porous ceramic particles of the present invention, the coat film is preferably formed of any material selected from polyvinyl butyral, polyvinyl alcohol, polycarbonate, and polylactic acid.

  The present invention further includes a step of filling a volatile liquid inside the pores of the porous ceramic particles, and after the porous ceramic particles filled with the volatile liquid are dispersed in a solution for forming a coating film. From the step of coating the surface of the porous ceramic particles with a coating film by adding a poor solvent, the step of evaporating a liquid having volatility by heating, and the glass transition temperature of the material forming the coating film And a method of producing surface-coated porous ceramic particles, comprising a step of heat-treating in a temperature range between 40 ° C. and a temperature higher than the transition temperature.

  In the method for producing surface-coated porous ceramic particles of the present invention, the coat film is preferably formed of any material selected from polyvinyl butyral, polyvinyl alcohol, polycarbonate, and polylactic acid.

  According to the present invention, it is possible to coat only the surface while leaving the air inside the porous ceramic particles without the material forming the coating film entering the pores of the porous ceramic particles. Furthermore, when compounding with a resin such as an epoxy resin, the resin penetrates into the hole opened in the coating film, so that the adhesion strength between the porous ceramic particles and the resin can be improved by the anchor effect of the resin. . From these, in the present invention, a composite material having a high elastic modulus and a low dielectric constant can be obtained.

It is a figure which shows typically the surface coat porous ceramic particle 1 of this invention. It is a figure which shows typically the porous ceramic particle 2 of the state before forming the coating film 3 in the surface coat porous ceramic particle 1 shown in FIG. It is a figure which shows the manufacturing method of the surface coat porous ceramic particle | grains 1 shown in FIG. 1 in steps. It is a graph which shows the relationship between the density | concentration (wt%) of a polyvinyl butyral solution, and the thickness of a polyvinyl butyral layer (coat film). It is a figure which shows typically the insulating material 11 using the surface coat porous ceramic particle 1 of this invention shown in FIG. It is a figure which shows typically the insulating material obtained by the comparative example 1. FIG. It is a figure which shows typically the insulating material obtained by the comparative example 2. FIG. It is a graph which shows the result of the bending elastic modulus of Examples 1-9 and Comparative Examples 1-4. It is a graph which shows the result of the dielectric constant of Examples 1-9 and Comparative Examples 1-4.

<Surface-coated porous ceramic particles>
FIG. 1 is a diagram schematically showing a surface-coated porous ceramic particle 1 of the present invention (Embodiment 1). The surface-coated porous ceramic particle 1 of the present invention comprises a porous ceramic particle 2 and a coating film 3 having a hole 4 that covers the surface of the porous ceramic particle 2 and does not penetrate to the surface of the porous ceramic particle 2. It is characterized by providing. According to the surface-coated porous ceramic particle 1 of the present invention as described above, air remains inside the porous ceramic particle without the material forming the coating film entering the pores of the porous ceramic particle 2. Only the surface can be coated. For this reason, when compounding with a resin such as an epoxy resin, the resin penetrates into the hole opened in the coating film, thereby improving the adhesion strength between the porous ceramic particles and the resin due to the anchor effect of the resin. it can. As a result, a composite material (insulating material) having both a high flexural modulus and a low dielectric constant can be obtained.

  In the present invention, porous alumina particles, porous silica particles, and the like can be used as the porous ceramic particles 2, and among these, porous alumina particles are preferably used from the viewpoint of the hardness of the porous particles. As the porous ceramic particles 2, commercially available ones can be used as appropriate.

  The shape of the porous ceramic particle 2 in the present invention is not particularly limited, such as a spherical shape, a crushed shape, and a flake shape.

  The size of the porous ceramic particle 2 in the present invention is not particularly limited, but the average particle size measured by laser diffraction particle size distribution measurement is preferably less than 2 mm, and is in the range of 10 to 300 μm. Is more preferable. This is because when the average particle diameter is 2 mm or more, it tends to be difficult to coat the entire porous ceramic particle 2.

  The porous ceramic particle 2 in the present invention has a large number of pores, and the size of the pores is not particularly limited, but the material forming the coating film penetrates into the pores and cannot be coated. For this reason, the diameter of the pores needs to be 1 μm or less, and if it is 100 nm or less, the coating material is more difficult to enter, which is more preferable. The diameter of the pores of the porous ceramic particles 2 can be measured using a mercury intrusion method or a gas adsorption method using nitrogen or argon gas.

  Here, FIG. 2 is a diagram schematically showing the porous ceramic particle 2 in a state before the formation of the coat film 3 in the surface-coated porous ceramic particle 1 shown in FIG. In the porous ceramic particle 2 before coating, pores can be observed on the surface layer. On the other hand, the surface coated porous ceramic particles 1 shown in FIG. 1 are coated with the coating film 3 on the surface layer, and the material for forming the coating film does not enter the pores of the porous ceramic particles 2. Then, the coating is performed with air remaining inside the pores of the porous ceramic particles 2.

  In the present invention, any material can be used as a material for forming the coating film 3 as long as it is a polymer material that can be in a solution state. However, polyvinyl butyral is used from the viewpoint of viscosity when it is made into a solution. , Polyvinyl alcohol, polycarbonate, or polylactic acid is preferable.

  The thickness of the coating film 3 is not particularly limited, but is preferably 0.1 μm or more. If the thickness of the coat film 3 is less than 0.1 μm, the thickness of the coat film 3 is so thin that when the obtained surface-coated porous ceramic particles and the resin are mixed, the resin destroys the coat film. This is because the resin may enter into the pores of the porous ceramic particles 2.

  Polyvinyl butyral is used as a material for forming the coating film, and the relationship between the concentration (wt%) and the thickness of the obtained polyvinyl butyral layer (coating film) is shown in Table 1 and FIG.

  Table 1 and FIG. 4 show the polyvinyl butyral layer on the surface of the porous alumina particles by changing the polyvinyl butyral concentration (2 wt%) in Example 1 described later to 1.5 wt%, 5 wt%, 7 wt%, and 10 wt%. The result of forming (coat film) is shown. From Table 1, it can be seen that the coating film thickness can be 0.1 μm or more by setting the polyvinyl butyral concentration to 2 wt% or more.

  The coating film 3 in the present invention has a hole 4 that does not penetrate to the surface of the porous ceramic particle 2. The size of the hole 4 formed in the coat film 3 is not particularly limited, but the diameter is preferably in the range of 0.3 to 3 μm, more preferably in the range of 1 to 2 μm. preferable. When the diameter of the hole 4 is less than 0.3 μm, the resin anchor effect tends to be small when it is combined with the resin, and the elastic modulus tends not to improve, and the diameter of the hole 4 exceeds 3 μm. In some cases, the hole is too large, making it difficult to produce a hole that does not penetrate. The diameter of the hole 4 of the coat film 3 can be measured by observing the surface and cross section of the porous ceramic particles using, for example, a scanning electron microscope.

  The hole 4 provided in the coat film 3 is not particularly limited as long as it does not penetrate the coat film 3. For example, when the thickness of the coat film 3 is in the range of 2 to 3 μm, the hole 4 is not limited. The depth is preferably in the range of 1 to 2 μm and not penetrating the coat film 3. The depth of the hole 4 in the coat film 3 can be measured by observing the cross section of the porous ceramic particles using, for example, a scanning electron microscope.

<Method for producing surface-coated porous ceramic particles>
FIG. 3 is a diagram showing step by step a method for producing the surface-coated porous ceramic particles 1 shown in FIG. The surface-coated porous ceramic particle 1 of the present invention described above includes a step of filling a volatile liquid in the pores of the porous ceramic particle, and a coating film of the porous ceramic particle filled with the volatile liquid. After dispersing in the solution to be formed, adding a poor solvent to coat the surface of the porous ceramic particles with a coat film, heating and evaporating the volatile liquid, then forming the coat film And a step of heat-treating in a temperature range between the glass transition temperature of the material to be heated and a temperature higher by 40 ° C. than the glass transition temperature. The present invention also provides a method for producing such surface-coated porous ceramic particles.

  First, as shown in FIG. 3A, a volatile liquid is filled in the pores of the porous ceramic particles 2. Since the porous ceramic particle 2 has pores on its surface, the inside of the pores can be filled with a volatile liquid by performing vacuum deaeration in a volatile liquid. The volatile liquid is not particularly limited as long as it can dissolve the material forming the coat film. For example, when polyvinyl butyral is used as the material forming the coat film, the viscosity of the solution is not limited. In view of the above, it is preferably used as a volatile liquid such as ethanol, 1-propanol, N-pentyl alcohol and the like. The vacuum degassing is not particularly limited as long as a known means is appropriately used.

  Next, as shown in FIG. 3B, the porous ceramic particles 2 filled with a volatile liquid are dispersed in a solution for forming the coating film 3, and then the porous solvent is added by adding a poor solvent. The surface of the ceramic particle 2 is coated with a coat film. Specifically, the porous ceramic particles filled with the volatile liquid obtained in the above-described step are added and dispersed in the volatile liquid in which the material forming the coating film is dissolved. . At this time, it is preferable to carry out stirring while stirring a volatile liquid in which a material for forming the coat film is dissolved (preferably in a range of 500 to 1000 rpm). The mixing amount of the porous ceramic particles and the volatile liquid in which the material forming the coating film is dissolved is preferably in the range of 1: 0.5 to 2.0 in terms of mass ratio. More preferably, it is within the range of 1: 1.0 to 1.5. If there are too many porous ceramic particles, the coating area will be wide, so there is a possibility that the material for forming the coating film will be insufficient. On the other hand, if there are too few porous ceramic particles, a coating film will be formed. There is a possibility that the material to be used becomes excessive and the coating film is deposited alone. The amount of porous ceramic particles is preferably in the range of 50 to 200 g.

  The concentration of the material forming the coating film is not particularly limited, but is preferably in the range of 2 to 10 wt%, and more preferably in the range of 5 to 8 wt%. If the concentration of the material forming the coating film is too high, the viscosity becomes high when the solution is made into a solution, and thus it may be difficult to disperse the porous ceramic particles. Further, when the concentration of the material forming the coat film is too low, the material forming the coat film may be insufficient.

  Thereafter, a poor solvent is added to the volatile liquid in which the material for forming the coat film is dissolved, in which the porous ceramic particles are dispersed. Here, the poor solvent means a poor solvent for the material for forming the coat film, and is not particularly limited as long as it is a liquid that does not dissolve the material for forming the coat film, but for example, polyvinyl butyral is used as the material for forming the coat film. When used, it is preferable to use pure water as a poor solvent. By adding a poor solvent in this way, a coat film is formed on the surface of the porous ceramic particles. The poor solvent is preferably added one drop at a time using, for example, a burette while stirring the solution under the same conditions as described above.

  The amount of the poor solvent added is not particularly limited, but is preferably 800 g or more per 100 g of porous ceramic particles, and more preferably 900 to 1300 g. If the amount of the poor solvent added is too small, the coating film may be insufficiently deposited on the surface of the porous ceramic particles.

  Next, the porous ceramic particles having the coat film 5 formed on the surface are heated to evaporate the volatile liquid. At this time, as shown in FIG. 3C, when the volatile liquid filled in the pores of the porous ceramic particles volatilizes, on the surface of the porous ceramic particles, A plurality of through holes 6 are formed at random. In FIG.3 (c), the place which expanded the whole porous ceramic particle on the left side and the one part on the right side is shown typically. Such heating of the porous ceramic particles is preferably performed under vacuum because it enables volatilization below the boiling point of the volatile liquid. For example, when ethanol is used as a volatile liquid, its boiling point is 78 ° C., but in a vacuum, it is volatilized by heating at a temperature lower than that, for example, at 50 ° C. for 3 hours. The liquid having properties can be suitably volatilized. On the other hand, when heating at room temperature, the volatile liquid can be suitably volatilized by heating at a temperature equal to or higher than the boiling point at which the volatile liquid evaporates, for example, at 80 ° C. for 3 hours. At this time, the through hole 6 formed in the coating film preferably has a diameter of 3 μm or less, and more preferably within a range of 1 to 2 μm.

  Next, it heat-processes in the temperature range between the glass transition temperature of the material which forms a coat film, and the temperature 40 degreeC higher than the said glass transition temperature. As a result, as shown in FIG. 3 (d), the coating film can have a small fluidity, and the surface of the porous ceramic particles 2 can be spotted. In addition, like FIG.3 (c), in FIG.3 (d), the place which expanded the whole porous ceramic particle | grains on the left side and the part on the right side is shown typically. In this way, the coating film 3 having a hole that covers the surface of the porous ceramic particle 2 and does not penetrate to the surface of the porous ceramic particle 2 is formed.

  If the temperature is too high during this heat treatment, the fluidity of the coating film is too high, and the entire through hole of the coating film may be blocked. For this reason, the heat treatment is performed in a temperature range between the glass transition temperature of the material forming the coat film as described above and a temperature 40 ° C. higher than the glass transition temperature. The glass transition temperature is a value determined by the type and molecular weight of the material. For example, when polyvinyl butyral having a number average molecular weight of 110000 is used as a material for forming a coat, the glass transition temperature is about 70 ° C. The glass transition temperature of the material forming such a coat can be confirmed by differential scanning calorimetry.

  In this way, the surface-coated porous ceramic particles 1 of the present invention shown in FIG. 1 are preferably produced. As will be described later in Examples, using polyvinyl butyral as a material for forming a coating film, the surface-coated porous ceramic particles of the present invention were actually produced by the above-described production method, and observed with a scanning electron microscope. It was observed that the surface of the porous ceramic particles was covered with polyvinyl butyral and that the surface of the coat film had holes. Furthermore, when the cross section of the sample was observed with a scanning electron microscope, it was observed that the polyvinyl butyral was present only on the surface of the porous ceramic particle without the polyvinyl butyral entering the pores of the porous ceramic particle.

<Insulating material>
FIG. 5 is a view schematically showing an insulating material 11 using the surface-coated porous ceramic particles 1 of the present invention shown in FIG. In the present invention, the surface-coated porous ceramic particles include porous ceramic particles 2 containing air therein, and holes 4 that cover the surface of the porous ceramic particles 2 and do not penetrate to the surface of the porous ceramic particles 2. Also provided is a surface-coated porous ceramic particle 1 having a coating film 3 having an insulating material 11 and an insulating material 11 composed of the surface-coated porous ceramic particle 1 and a resin 12 (Embodiment 2). In such an insulating material 11 of the present invention, the resin 12 enters the inside of the hole 4 of the coating film 3 so that the adhesion strength between the surface-coated porous ceramic particles 1 and the resin 12 is increased due to the anchor effect of the resin 12. It is an improved composite material having both a high flexural modulus and a low dielectric constant.

  Here, the high flexural modulus exhibited by the insulating material 11 of the present invention means that the flexural modulus measured at room temperature (25 ° C.) according to JIS-K6911 is in the range of 10 GPa or more. . Moreover, the low dielectric constant exhibited by the insulating material 11 of the present invention means that the dielectric constant measured at room temperature (25 ° C.) according to JIS-K6911 is 5 or less.

  As the resin 12 used for the insulating material 11 of the present invention, for example, a thermosetting resin such as an epoxy resin or a phenol resin is preferably used. Among these, an epoxy resin is particularly preferable from the viewpoint of viscosity when it is made into a solution.

  In the insulating material 11 of the present invention, the mixing ratio of the surface-coated porous ceramic particles 1 and the resin 12 is not particularly limited, but is preferably in the range of 9: 1 to 2: 8 by weight, More preferably, it is in the range of 4 to 3: 7. This is because when the mixing ratio of the surface-coated porous ceramic particles 1 and the resin 12 is less than 9: 1 by weight (when the resin is too small), the dielectric constant of the insulating material tends to increase. This is because when the ratio exceeds 2: 8 (when the resin is too much), the strength of the insulating material tends to decrease.

<Insulating material manufacturing method>
The insulating material 11 of the present invention described above can be preferably manufactured as follows, for example. First, surface-coated porous ceramic particles (for example, porous ceramic particles are porous alumina particles, and the material for forming the coating film is polyvinyl butyral) are introduced into the main component of a resin (for example, epoxy resin) and dispersed uniformly. Stir so that. Thereafter, after adding a curing agent for the resin, the mixture is further mixed with stirring. Next, vacuum deaeration (for example, 1 minute) is performed to remove air from the resin, and then the resin is molded and cured (for example, in the case of an epoxy resin, cured at 130 ° C. for 12 hours).

  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>
As porous ceramic particles, porous alumina particles having an average particle size of 100 μm were used, vacuum deaeration was performed in ethanol (a volatile liquid), and ethanol was filled into the pores of the porous alumina particles. Polyvinyl butyral having a number average molecular weight of 110000 was used as a material for forming the coat film, and dissolved in ethanol to a concentration of 2 wt% while stirring at 700 rpm using a stirring bar. Thereafter, porous alumina particles filled with ethanol were put into a polyvinyl butyral solution. At this time, the polyvinyl butyral solution was 100 g with respect to 100 g of porous alumina particles. Thereafter, while stirring at 700 rpm, pure water (poor solvent) was added at a speed of 1 drop per second using a burette to form a coating film having no holes on the surface of the porous alumina particles. The amount of pure water added was 1000 g per 100 g of porous alumina particles. Then, it heated at 50 degreeC under vacuum for 3 hours, and the ethanol with which the internal pore of the porous alumina particle was filled was volatilized. At this time, a plurality of through holes were randomly formed in the holes penetrating the coat film surface. Next, heat treatment was performed at 90 ° C. to impart fluidity to the coat film, and the surface of the porous alumina particles was aspired. In this way, surface-coated porous ceramic particles comprising porous ceramic particles and a coating film covering the surface of the porous ceramic particles and having a hole not penetrating to the surface of the porous ceramic particles were formed.

  When the surface of the obtained surface-coated porous ceramic particles was observed with a scanning electron microscope, the surface of the porous alumina particles was coated with polyvinyl butyral, and the coating film surface had holes. I was able to observe. Further, when the cross section of the sample was observed with an electron beam microanalyzer, it was observed that polyvinyl butyral was present only on the surface of the porous alumina particles without the polyvinyl butyral entering the pores of the porous alumina particles. The thickness of the coating film measured by cross-sectional observation was 0.1 μm, the hole diameter was 1.1 μm, and the hole depth was 0.05 μm.

  The obtained surface-coated porous ceramic particles were put into an epoxy resin main agent and mixed for 1 hour with stirring at a rotation speed of 70 rpm in order to uniformly disperse the particles. At this time, the mixing ratio of the porous alumina particles and the epoxy resin was 50 wt%: 50 wt%. Then, after adding a hardening | curing agent, it mixed for 5 minutes, stirring at 70 rpm. In order to remove the air in the resin, vacuum deaeration was performed for 1 minute, followed by curing at 130 ° C. for 12 hours to obtain an insulating material as shown in FIG.

  The obtained insulating material was processed into a length of 70 mm, a width of 10 mm, and a thickness of 3 mm, and the bending elastic modulus was measured at room temperature (25 ° C.) according to JIS-K6911. As a result, it was 11.1 GPa. Moreover, the dielectric constant measured at room temperature (25 degreeC) according to JIS-K6911 was 4.5.

<Example 2>
Surface-coated porous ceramic particles in the same manner as in Example 1 except that polyvinyl butyral (material forming the coating film) was dissolved in ethanol (volatile liquid) so as to have a concentration of 5 wt%. Formed. The thickness of the coating film of the surface-coated porous ceramic particles was 1.1 μm, the hole diameter was 1.3 μm, and the hole depth was 0.5 μm. Thereafter, an insulating material was manufactured in the same manner as in Example 1. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.5 GPa, and the dielectric constant was 4.3.

<Example 3>
Surface-coated porous ceramic particles in the same manner as in Example 1 except that polyvinyl butyral (material forming the coating film) was dissolved in ethanol (volatile liquid) to a concentration of 10 wt%. Formed. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 2.1 μm, the hole diameter was 1.3 μm, and the hole depth was 1.1 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.4 GPa, and the dielectric constant was 4.5.

<Example 4>
Polycarbonate is used as the material for forming the coating film, tetrahydrofuran is used as the volatile liquid, and the concentration of the polycarbonate (the material forming the coating film) in tetrahydrofuran (the volatile liquid) is 2 wt%. Surface-coated porous ceramic particles were formed in the same manner as in Example 1 except that the solution was dissolved and pure water was used as the poor solvent. The thickness of the coat film of the obtained surface-coated porous ceramic particles was 0.2 μm, the hole diameter was 1.1 μm, and the hole depth was 0.06 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.0 GPa, and the dielectric constant was 4.4.

<Example 5>
Surface-coated porous ceramic particles were obtained in the same manner as in Example 4 except that polycarbonate (material for forming the coating film) was dissolved in tetrahydrofuran (volatile liquid) so as to have a concentration of 5 wt%. Formed. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 1.3 μm, the hole diameter was 1.5 μm, and the hole depth was 0.7 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.5 GPa, and the dielectric constant was 4.2.

<Example 6>
Surface-coated porous ceramic particles were prepared in the same manner as in Example 4 except that polycarbonate (material forming the coating film) was dissolved in tetrahydrofuran (volatile liquid) so as to have a concentration of 10 wt%. Formed. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 2.5 μm, the hole diameter was 1.6 μm, and the hole depth was 1.3 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.5 GPa, and the dielectric constant was 4.1.

<Example 7>
Polylactic acid is used as the material for forming the coating film, methylene chloride is used as the volatile liquid, and the concentration of polylactic acid (the material forming the coating film) is 2 wt% in methylene chloride (the volatile liquid). Surface-coated porous ceramic particles were formed in the same manner as in Example 1 except that the solution was dissolved in the following manner and that pure water was used as the poor solvent. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 0.1 μm, the hole diameter was 1.4 μm, and the hole depth was 0.07 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 10.9 GPa, and the dielectric constant was 4.3.

<Example 8>
Surface-coated porous ceramics in the same manner as in Example 7 except that polylactic acid (material forming the coating film) was dissolved in methylene chloride (volatile liquid) so as to have a concentration of 5 wt%. Particles were formed. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 1.2 μm, the hole diameter was 1.4 μm, and the hole depth was 0.6 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.6 GPa, and the dielectric constant was 4.3.

<Example 9>
Surface-coated porous ceramics in the same manner as in Example 7 except that polylactic acid (material forming the coating film) was dissolved in methylene chloride (volatile liquid) so as to have a concentration of 10 wt%. Particles were formed. The thickness of the coating film of the obtained surface-coated porous ceramic particles was 2.4 μm, the hole diameter was 1.5 μm, and the hole depth was 1.2 μm. Thereafter, an insulating material was produced in the same manner as in Example 1 using the obtained surface-coated porous ceramic particles. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.4 GPa, and the dielectric constant was 4.2.

<Comparative Example 1>
Polyvinyl butyral (a material for forming a coating film) was dissolved in ethanol (a volatile liquid) so as to have a concentration of 5 wt%, and described in JP-A-63-113081 (Patent Document 2). By the method, the insulating material of the surface coat porous alumina particle | grains which do not have a hole on the surface, and an epoxy resin was produced. FIG. 6 is a diagram schematically showing the insulating material obtained in Comparative Example 1. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 7.2 GPa, and the dielectric constant was 4.4.

<Comparative Example 2>
An insulating material was produced by mixing untreated porous alumina particles having no coating film on the surface and an epoxy resin. FIG. 7 is a diagram schematically showing the insulating material obtained in Comparative Example 2. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 11.3 GPa, and the dielectric constant was 6.0.

<Comparative Example 3>
An insulating material was produced in the same manner as in Comparative Example 1 except that polycarbonate was used as the material for forming the coating film and tetrahydrofuran was used as the volatile liquid. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 7.0 GPa, and the dielectric constant was 4.2.

<Comparative Example 4>
An insulating material was produced in the same manner as in Comparative Example 1 except that polylactic acid was used as the material for forming the coating film and methylene chloride was used as the volatile liquid. With respect to the obtained insulating material, the flexural modulus measured in the same manner as in Example 1 was 6.9 GPa, and the dielectric constant was 4.1.

  Table 2 shows the results of Examples 1 to 9 and Comparative Examples 1 to 4.

  Moreover, the result of the bending elastic modulus of Examples 1-9 and Comparative Examples 1-4 is shown in FIG. 8, and the result of the dielectric constant of Examples 1-9 and Comparative Examples 1-4 is shown in FIG. From the results shown in Table 2 and FIGS. 8 and 9, it can be seen that Comparative Example 1 does not have a hole in the coating film on the surface of the porous alumina particles, and thus does not have an epoxy resin anchor effect. On the other hand, in Comparative Example 2, it is considered that the epoxy resin penetrates into the pores of the porous alumina particles and has an anchor effect of the epoxy resin.

  From the results shown in Table 2 and FIG. 8, in Examples 1, 2, and 3, the bending elastic moduli are 11.1 GPa, 11.5 GPa, and 11.4 GPa, respectively, and the bending elasticity of Comparative Example 2 having a resin anchor effect. It turns out that the value equivalent to 11.3 GPa which is a rate is shown. On the other hand, the bending elastic modulus of Comparative Example 1 is 7.2 GPa, and since it does not have the resin anchor effect, it can be seen that the bending elastic modulus is low.

  From the results shown in Table 2 and FIG. 9, in Examples 1, 2, and 3, the dielectric constants were 4.5, 4.3, and 4.5, respectively, and Comparative Example 1 in which air remained inside the porous alumina particles It can be seen that the value is equivalent to 4.4, which is the dielectric constant of. This is because the dielectric constant of alumina is about 9.3 and the dielectric constant of epoxy resin is about 4.2, whereas the dielectric constant of air is 1.0. This is because the rate can be lowered and a low dielectric constant material can be obtained. On the other hand, the dielectric constant of Comparative Example 2 is 6.0, which is thought to be because the resin entered into the pores of the porous alumina particles and no air remained inside.

  From these results, in order to have a high flexural modulus and a low dielectric constant, it can be seen that a structure having holes that do not penetrate through the surface of the coating film as in Examples 1, 2, and 3 is effective. Further, even when the concentration of the material forming the coating film was changed in the range of 2 wt% or more and 10 wt% or less as in Examples 1, 2, and 3, no significant difference was found in the flexural modulus and dielectric constant.

  In Examples 4, 5, 6 and Comparative Example 3, when polycarbonate was used as a material for forming a coat film, Examples 7, 8, 9 and Comparative Example 4 used polylactic acid as a material for forming a coat film. It is a bending elastic modulus and dielectric constant measurement result in the case. The bending elastic moduli of Examples 4, 5, and 6 using polycarbonate as the material for forming the coating film are 11.0 GPa, 11.5 GPa, and 11.5 GPa, respectively, and the bending elasticity of Comparative Example 2 that has a resin anchor effect. It turns out that the value equivalent to 11.3 GPa which is an elastic modulus is shown. On the other hand, the bending elastic modulus of Comparative Example 3 is 7.0 GPa, and since it does not have the resin anchor effect, it can be seen that the bending elastic modulus is low. The dielectric constants of Examples 4, 5, and 6 are 4.4, 4.2, and 4.1, respectively, which is the dielectric constant of Comparative Example 3 in which air remains in the porous alumina particles. It turns out that the value equivalent to 2 is shown. On the other hand, the dielectric constant of Comparative Example 2 is 6.0, and it is considered that the resin penetrates into the pores of the porous alumina particles and no air remains inside. From these results, even when polycarbonate is used as the material for forming the coat, in order to have a high flexural modulus and a low dielectric constant, it penetrates the coat film surface as in Examples 4, 5, and 6. A structure with no holes is found to be effective.

  In addition, the flexural moduli of Examples 7, 8, and 9 using polylactic acid as the material for forming the coating film are 10.9 GPa, 11.6 GPa, and 11.4 GPa, respectively, and are comparative examples that have a resin anchor effect. It can be seen that the value is equivalent to 11.3 GPa, which is a flexural modulus of 2. On the other hand, the bending elastic modulus of Comparative Example 4 is 6.9 GPa, and since it does not have the resin anchor effect, it can be seen that the bending elastic modulus is low. The dielectric constants of Examples 7, 8, and 9 are 4.3, 4.3, and 4.2, respectively, which are the dielectric constants of Comparative Example 4 in which air remains in the porous alumina particles. It turns out that the value equivalent to 1 is shown. On the other hand, the dielectric constant of Comparative Example 2 is 6.0, and it is considered that the resin penetrates into the pores of the porous alumina particles and no air remains inside. From these results, even when polylactic acid is used as the material for forming the coating film, in order to have a high flexural modulus and a low dielectric constant, the coating film as in Examples 7, 8, and 9 of the present invention. It can be seen that a structure having a hole not penetrating the surface is effective.

  DESCRIPTION OF SYMBOLS 1 Surface coat porous ceramic particle, 2 Porous ceramic particle, 3 Coat film | membrane, 4 holes, 5 Coat film | membrane without an unevenness | corrugation on the surface, 6 Through-hole, 11 Insulating material, 12 Resin.

Claims (5)

Porous ceramic particles;
A surface-coated porous ceramic particle comprising: a coating film covering a surface of the porous ceramic particle and having a hole that does not penetrate to the surface of the porous ceramic particle.   The surface-coated porous ceramic particle according to claim 1, wherein the coating film is formed of any material selected from polyvinyl butyral, polyvinyl alcohol, polycarbonate, and polylactic acid. Surface-coated porous ceramic particles comprising porous ceramic particles containing air inside and a coating film that covers the surface of the porous ceramic particle and has a hole that does not penetrate to the surface of the porous ceramic particle;
An insulating material comprising the composite material of the surface-coated porous ceramic particles and a resin. Filling a volatile liquid into the pores of the porous ceramic particles;
A step of dispersing porous ceramic particles filled with a volatile liquid in a solution for forming a coating film, and then coating the surface of the porous ceramic particles with a coating film by adding a poor solvent;
Heating and evaporating the volatile liquid;
And a step of heat-treating in a temperature range between a glass transition temperature of a material forming the coat film and a temperature higher by 40 ° C. than the glass transition temperature.   The method for producing surface-coated porous ceramic particles according to claim 4, wherein the coat film is formed of any material selected from polyvinyl butyral, polyvinyl alcohol, polycarbonate, and polylactic acid.

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