JP2013001587A - Powder, molded body, wrapped body, and method for producing powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide powder maintaining a uniform mixed state.SOLUTION: The powder includes silica, exhibits an angle of repose of 35° to 55°, and has thermal conductivity of 0.05W/m.K or less at 30°C.

Description

  The present invention relates to a powder, a molded body thereof, an encapsulant, and a method for producing the powder.

  The mean free path of air molecules at room temperature is about 100 nm. Therefore, in a porous body having voids with a diameter of 100 nm or less, heat transfer due to air convection and conduction is suppressed, and such a porous body exhibits an excellent heat insulating effect.

  It is known that ultrafine particles have a low thermal conductivity and are suitable as a heat insulating material in accordance with the principle of the heat insulating action. For example, Patent Document 1 below discloses a thermal insulating material and a method for manufacturing the same, which are a mixture of a microporous insulating material, an infrared shielding agent, and a granular insulating filler material.

Special table 2008-533402 gazette

  However, when a plurality of substances are mixed as in the heat insulating material described in Patent Document 1, when the mixture is transported by a vehicle or the like, the mixing situation changes due to the influence of vibration or the like, and is stored in, for example, a bag. If the upper part and the lower part of the stored bag are compared, the mixing situation may be different. For example, if the angle of repose is too large, it will be difficult for fluid to flow near the inner wall of the bag or near the inner wall of the filling location in the bag containing the powder or at the filling location of the powder. Then, other mixed components (particularly particles having a large specific gravity) are separated with vibration and collected in the lower layer, resulting in a change in the mixed state. In addition, this problem does not occur only during transportation, and in the case of using it as a heat insulating material in the state of powder, the mixed state changes due to continuous vibration for many years, and the heat insulating performance is reduced. In some cases, it may cause a decrease.

  When the mixed state changes, the composition of the mixed powder differs between the upper part and the lower part in the bag, and a problem arises in that, for example, a predetermined heat insulating performance is not exhibited when the powder is used. Even when these powders are molded as raw materials, the composition of the mixture changes from one molded body to another, and the dispersion in performance is so great that defects frequently occur and the yield decreases, which is not preferable.

  This invention is made | formed in view of the subject which such a prior art has, and aims at providing the powder which can maintain a uniform mixed state. Moreover, it aims at providing the manufacturing method of the molded object containing the said powder, the said powder and / or the envelopment in which the said molded object was accommodated in the jacket material, and the said powder.

  As a result of intensive investigations for overcoming the problem based on the prior art, the present inventor has determined that the repose angle of the silica powder having low thermal conductivity is appropriately set so that the mixed state is less likely to change. To the present invention. That is, the present invention is a powder, a molded body, an encapsulant and a method for producing the powder as described below.

  The powder of the present invention contains silica, has an angle of repose of 35 ° to 55 °, and a thermal conductivity at 30 ° C. of 0.05 W / m · K or less. With such a powder, it is possible to maintain a uniform mixed state.

  The powder of the present invention, which contains infrared opaque particles, preferably has a thermal conductivity at 800 ° C. of 0.15 W / m · K or less.

  The average particle diameter of the infrared opaque particles contained in the powder of the present invention is preferably 0.5 μm or more and 30 μm or less, and the content of the infrared opaque particles is 0 based on the total mass of the powder. It is preferable that they are 1 mass% or more and 39.5 mass% or less.

  The powder of the present invention contains sodium (Na), and the content of sodium (Na) is preferably 0.005% by mass or more and 3% by mass or less based on the total mass of the powder.

  The powder of the present invention contains iron (Fe), and the iron (Fe) content is preferably 0.005 mass% or more and 6 mass% or less based on the total mass of the powder.

  The powder of the present invention further contains inorganic fibers, and the content of the inorganic fibers is preferably 0.1% by mass or more and 50% by mass or less based on the total mass of the powder.

  The inorganic fibers contained in the powder of the present invention preferably have biosolubility.

  The powder of the present invention contains germanium (Ge), and the content of germanium (Ge) is preferably 10 mass ppm or more and 1000 mass ppm or less based on the total mass of the powder.

  The molded body of the present invention contains the powder. Since such a molded body contains the powder of the present invention capable of maintaining a uniform mixed state, it is possible to suppress variation in performance due to a change in the mixed composition for each molded body. This is possible, and the yield can be improved.

  The enveloping body of the present invention includes an outer covering material, and the powder and / or the molded body accommodated in the outer covering material. Such an encapsulated body not only has the excellent characteristics of the powder and molded body of the present invention, but is also easier to handle than the powder and molded body, and therefore has excellent workability. .

  In the envelope according to the present invention, the outer covering material preferably contains inorganic fibers.

  In the envelope according to the present invention, the outer covering material is preferably a resin film.

The above method for producing a powder of the present invention comprises a silica, and small particles having an average particle diameter D _S is at 5nm or 30nm or less, comprises silica, and large particles having an average particle diameter D _L is at 40nm or more 60μm or less , To obtain an inorganic mixture, wherein the angle of repose of the small particles is 25 degrees or more and 80 degrees or less, and the angle of repose of the large particles is 25 degrees or more and 80 degrees or less, and the small particles contained in the inorganic mixture This is a production method in which the ratio of the mass of the large particles to the total mass of the particles and large particles is adjusted to 0.02 to 0.95. According to this production method, a powder capable of maintaining a uniform mixed state can be produced.

  According to the present invention, a powder capable of maintaining a uniform mixed state can be provided. Moreover, the molded object containing the said powder, the said powder and / or the encapsulation body in which the said molded object was accommodated in the jacket material, and the manufacturing method of the said powder can be provided. A molded body produced using the powder of the present invention as a raw material has little variation in heat insulating performance. Even if it is processed into an encapsulant, it is excellent in retention in a mixed state.

It is a cross-sectional schematic diagram of the envelope which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram of the small particle and large particle which the molded object which concerns on one Embodiment of this invention contains.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

[1] Powder The powder of the present embodiment contains silica, has an angle of repose of 35 ° to 55 °, and a thermal conductivity at 30 ° C. of 0.05 W / m · K or less. Even if such a powder continues to receive vibration during transportation of the powder, it is possible to maintain a good mixed state.

[1-1] Silica (silica particles)
In the powder, the silica component is preferably contained as silica particles. When the content of the silica particles in the powder is 50% by mass or more, heat transfer due to solid conduction is small, which is preferable for use as a heat insulating material. It is more preferable that the content of the silica particles is 75% by mass or more of the powder because the adhesion between the powders increases and the scattering of the powder decreases. In the present specification, the silica particles, contain other particles comprised of component represented by the composition formula SiO _2, it refers to a material containing SiO _2, a metal component or the like in addition to SiO _2, other inorganic compounds Including particles. In addition to pure silicon dioxide, the silica particles may contain salts and complex oxides with Si and various other elements, or may contain hydrated oxides such as hydroxides. It may have a silanol group. The silica in the silica particles may be crystalline, amorphous, or a mixture thereof. However, in the case of a heat insulating material, the silica in the heat insulating material It is preferable because heat transfer by solid conduction is small and heat insulation performance is high.

Specific examples of the silica particles include the following.
An oxide of silicon called “silica” or “quartz”.
Partial oxide of silicon.
Silicon complex oxide such as silica alumina and zeolite.
Any one of silicate (glass) of Na, Ca, K, Mg, Ba, Ce, B, Fe and Al.
A mixture of an oxide, partial oxide, salt or composite oxide (alumina, titania, etc.) of an element other than silicon and an oxide, partial oxide, salt or composite oxide of silicon.
SiC and SiN oxides.

  When using powder as a heat insulating material, it is preferable that a silica particle is thermally stable in the temperature used. Specifically, it is preferable that the weight of the silica particles does not decrease by 10% or more when held for 1 hour at the maximum use temperature of the heat insulating material. Moreover, it is preferable that a silica particle has water resistance from a viewpoint of maintaining heat insulation performance, when using it as a heat insulating material, and a viewpoint of the shape maintenance of a molded object. Specifically, the amount of silica particles dissolved in 100 g of water at 25 ° C. is preferably less than 0.1 g, and more preferably less than 0.01 g.

  The specific gravity of the silica particles is preferably 2.0 or more and 4.0 or less when the powder is a heat insulating material. It is more preferable that it is 2.0 or more and 3.0 or less because the bulk density of the heat insulating material is small, and it is more preferable that it is 2.0 or more and 2.5 or less. Here, the specific gravity of the inorganic compound particles containing silica refers to the true specific gravity determined by the pycnometer method.

  Depending on the use of the powder, the powder may contain materials other than silica particles. The materials other than the silica particles will be described in detail later. When the powder contains a material other than the silica particles, the content of the silica particles is 50% by mass or more and 99.9% by mass based on the total mass of the powder. % Or less is preferable. Powders containing 50% by mass or more and 97.5% by mass or less of silica particles and containing inorganic fibers and infrared opaque particles are more effective in reducing powder scattering and improving heat insulation performance at high temperatures. Appears suitably and is more preferred. It is more preferable that the content is 60% by mass or more and 97.5% by mass or less because the bulk density of the powder is smaller.

  In general, silica particles having a particle diameter of 30 nm or less (hereinafter referred to as “small particles”) tend to have a large angle of repose. For this reason, the present inventor assumes that the repose angle increases because silica particles having a particle diameter of 30 nm or less tend to aggregate. Therefore, since it is difficult to obtain a powder satisfying an angle of repose of 55 degrees or less, a powder consisting only of small particles is mixed with silica particles having a relatively large particle diameter and a small angle of repose (hereinafter “large particles”). Thus, it is preferable to adjust the angle of repose of the powder. From the viewpoint of easy adjustment of the angle of repose of the whole powder when mixed with small particles, the particle diameter of the large particles is preferably 40 nm or more and 60 μm or less. The angle of repose is a characteristic value related to the resistance to interparticle friction or interparticle motion, and is affected by particle size distribution, particle surface roughness, powder layer porosity, moisture, and the like. Therefore, depending on the properties of the particles, even a powder consisting only of large particles may not satisfy an angle of repose of 55 degrees or less. However, the present inventors have surprisingly found that the angle of repose can be made 55 degrees or less by mixing large particles having an angle of repose of more than 55 degrees and small particles having an angle of repose of more than 55 degrees. discovered. The reason for this is not clear, but by mixing particles with different particle sizes, the interparticle friction angle, which is the physical friction angle between particles, the internal friction angle, which is the friction angle between layers within the powder, etc. By changing, it is estimated that the angle of repose in the mixed state decreases.

That is, the powder may contain only one kind of silica particles, or may contain two or more kinds, but when containing two kinds of particles having different particle diameters, that is, small particles and large particles made of silica, Since the angle of repose and thermal conductivity are different from the case where only particles or large particles exist, the angle of repose and / or thermal conductivity can be adjusted by mixing two kinds of particles at an appropriate ratio.
For example, the average particle diameter _{D S} is less small particles 30nm or 5nm is an angle of repose is the case of 55 degrees greater than this, for example, an average particle diameter _{D L} is large angle of repose of about 30 degrees 40nm or more 60μm or less When particles are mixed, the angle of repose is easily set to 35 degrees or more and 55 degrees or less. Moreover, even large particles of an angle of repose 55 degrees greater, _{D L} is the 60μm or less large particles above 40 nm _{D S} that is mixed with the following small particles 30nm or more 5 nm, the angle of repose below 55 degrees It is possible to prepare. In addition, large particles have large solid heat conduction, and the thermal conductivity may exceed 0.05 W / m · K. When small particles are mixed with the large particles, the solid heat conduction of the obtained mixed powder is large particles. It tends to be smaller than the above, and tends to be 0.05 W / m · K or less.

As described above, when mixing multiple types of particles, the angle of repose and thermal conductivity of the resulting mixed powder are different from those before mixing. It is preferable to appropriately measure the angle and the thermal conductivity and adjust the mixing ratio of the powder so that the angle of repose is 35 ° to 55 ° and the thermal conductivity is 0.05 W / m · K or less.
When the powder contains two or more types of silica particles, large particles are used so that the angle of repose of the powder is 35 degrees or more and 55 degrees or less and the thermal conductivity is 0.05 W / m · K or less. The content of small particles may be adjusted. For example, when small particles of about 10 nm and large particles of about 5 μm are mixed, the mass of large particles / (mass of small particles + mass of large particles) is preferably set to 0.1. When it is 02 to 0.95, more preferably 0.10 to 0.90, and particularly preferably 0.15 to 0.85, the thermal conductivity is about 0.028 W / m · K to 0.047 W / m · K. The thermal conductivity can be adjusted. The void formed by these particles becomes a bottleneck for heat conduction in the space, and heat conduction in the space is easily suppressed. As described above, it is known that a porous body having voids with a diameter of 100 nm or less has a low thermal conductivity and is suitable for a heat insulating material. When such a powder is desired, it is simple to form ultrafine particles having a particle diameter of 100 nm or less by pressing or the like. On the other hand, it was conventionally considered not suitable as a heat-insulating material, for example, even if particles with a particle size not so small on the order of micrometers are used as raw materials, they are mixed with ultrafine particles (small particles) in an appropriate amount. It has been discovered that it is possible to develop excellent heat insulation performance. Utilizing this discovery is one of the preferred embodiments of the present invention.

The particle diameter of the silica particles can be measured by observing with a field emission scanning electron microscope (FE-SEM). The average particle diameter D _S of the small particles and the average particle diameter D _L of the large particles are obtained by observing 1000 small particles and 1000 large particles, respectively, with an FE-SEM, calculating the equivalent area circle equivalent diameter, and calculating the number average. Can be obtained. From the viewpoint of solid conduction of the silica particles, the average particle size of the silica particles is preferably 5 nm to 60 μm, more preferably 5 nm to 40 μm, and further preferably 5 nm to 30 μm.

In the powder containing large particles and small particles, the average particle diameter D _S of the small particles is preferably 5nm or more 30nm or less. If D _S is in 5nm or more, compared to the case D _S is outside the above numerical range, they tend small particles are chemically stable, heat-insulating performance may stable tendency. If D _S is a 30nm or less, compared with the case D _S is outside the above numerical range, small contact area between the small particles, less heat transfer due to the powder of the solid conduction, tends low thermal conductivity There is. D _S is, if it is 5nm or 25nm or less, more preferably from the viewpoint of thermal conductivity and further preferably 5nm or 20nm or less.

The average particle diameter D _L of the large particles preferably satisfies D _S <D _L and is 40 nm or more and 60 μm or less. D _L is obtained by the same method as D _S described above. When _DL is 40 nm or more, when the powder is molded, the spring back in the molded product tends to be small. When D _L is at 60μm or less, they tend low thermal conductivity. The average particle diameter D _L of the larger particles, if it is 40nm or more 10μm or less, since the powder is easy uniform mixing thereof with the case containing the inorganic fibers and the infrared opacifying particles, more preferred. D _L is, if it is 40nm or more 5μm or less, increase adhesion of the particles, for separation of particles from the powder is low, more preferably.

When D _L is at least twice the D _S, since the springback is reduced when molded powder, preferred. D _L is the is more than three times D _S, large bulk density of the mixed powder of small particles and large particles, because of their high workability powder volume is small, more preferred. D _L is the is more than 4 times the D _S, large difference in particle size of the small particles and large particles, since it is easy to disperse for small particles of large particles when mixed with small particles and large particles, further preferable. When the powder is used as a heat insulating material, each particle is preferably dispersed from the viewpoint of solid heat transfer due to aggregation of the particles.

  The powder preferably contains a water repellent from the viewpoint of suppressing deterioration in handling properties, deformation of the molded body, cracking, and the like when water is immersed in the powder or the molded body. Examples of the water repellent include wax-based water repellents such as paraffin wax, polyethylene wax, and acrylic / ethylene copolymer wax; silicon-based water repellents such as silicone resin, polydimethylsiloxane, and alkylalkoxysilane; Fluorine-based water repellents such as carboxylates, perfluoroalkyl phosphates, perfluoroalkyltrimethylammonium salts, silane coupling agents such as alkoxysilanes containing alkyl or perfluoro groups, trimethylsilyl chloride, 1,1,1 And silylating agents such as 3,3,3-hexamethyldisilazane. These can be used alone or in combination of two or more. These may be used as they are, or in the form of a solution or an emulsion. Of these, wax-based water repellents and silicon-based water repellents are preferably used. From the viewpoint of imparting a sufficient water repellent effect, the content ratio of the water repellent in the powder is preferably 100/30 to 100 / 0.1, and preferably 100/30 to 100 / 0.1. 20-100 / 0.5 is more preferable, and 100 / 10-100 / 1 is still more preferable. The method of adding the water repellent is not particularly limited. For example, the method of drying the powder while stirring the water repellent diluted with a solvent such as water or alcohol, the method of drying the powder, water or alcohol, etc. Examples of such a method include a method of adding a water repellent to the slurry, stirring and filtering, drying the mixture, and steaming with chlorotrimethylsilane.

[1-2] Inorganic fiber When powder is formed, the powder preferably contains inorganic fiber. The powder containing inorganic fibers has the advantage that, in pressure molding, there is little dropout of particles from the molded body and the productivity is high. Furthermore, the molded object containing an inorganic fiber has the advantage that it is hard to disintegrate and is easy to handle. Even in the state of powder, there is little scattering, which is preferable in handling. In the present specification, the term “inorganic fiber” means that the ratio of the average length of the inorganic fiber to the average thickness (aspect ratio) is 10 or more. The aspect ratio is preferably 10 or more. When molding a powder, it is preferably 50 or more from the viewpoint of enabling molding with a small pressure and improving the productivity of the molded body, and from the viewpoint of bending strength of the molded body. 100 or more is more preferable. The aspect ratio of the inorganic fiber can be determined from the average value of the thickness and length of 1000 inorganic fibers measured by FE-SEM. The inorganic fibers are preferably monodispersed and mixed in the powder. However, the inorganic fibers may be mixed in a state where the inorganic fibers are entangled with each other or in a bundle in which a plurality of inorganic fibers are aligned in the same direction. . In the monodispersed state, the inorganic fibers may be aligned in the same direction, but from the viewpoint of reducing the thermal conductivity, the inorganic fibers are oriented in a direction perpendicular to the heat transfer direction. It is preferable. The method for orienting the inorganic fibers perpendicularly to the heat transfer direction is not particularly limited. For example, when filling the powder into the jacket material or the construction site, the powder is dropped and filled from the high place to the filling site. As a result, the inorganic fibers tend to be oriented perpendicular to the heat transfer direction. In the case of a pressure-molded body, for example, by applying pressure in the same direction as the heat transfer direction, the inorganic fibers that have been oriented in the heat transfer direction can be easily oriented in a direction perpendicular to the heat transfer direction.

Examples of inorganic fibers include long glass fibers (filaments) (SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —CaO), glass wool (SiO ₂ —Al ₂ O ₃ —CaO—Na ₂ O), alkali resistance Glass fiber (SiO ₂ —ZrO ₂ —CaO—Na ₂ O), rock wool (basalt wool) (SiO ₂ —Al ₂ O ₃ —Fe ₂ O ₃ —MgO—CaO), slag wool (SiO ₂ —Al ₂ O) ₃ -MgO-CaO), ceramic fibers (mullite _{fiber) (Al 2 O 3 -SiO 2} ), silica fibers _(SiO 2), alumina fibers _{(Al 2 O 3 -SiO 2)} , potassium titanate fibers, alumina whiskers, Silicon carbide whisker, silicon nitride whisker, calcium carbonate whisker, basic magnesium sulfate whisker, calcium sulfate Muwisuka (gypsum fiber), zinc oxide whisker, zirconia fiber, carbon fiber, graphite whisker, phosphate fibers, AES (Alkaline Earth Silicate) fiber _(SiO 2 -CaO-MgO), natural mineral wollastonite, sepiolite, attapulgite, Blue site can be mentioned.

Among inorganic fibers, it is preferable to use biosoluble AES fiber (Alkaline Earth Silicate Fiber) that is safe for the human body. Examples of the AES fiber include SiO ₂ —CaO—MgO-based inorganic glass (inorganic polymer).

  The average thickness of the inorganic fibers is preferably 1 μm or more from the viewpoint of preventing scattering. In the case of a heat insulating material, the thickness is preferably 20 μm or less from the viewpoint of suppressing heat transfer by solid conduction. The average thickness of the inorganic fibers can be obtained by obtaining the thickness of 1000 inorganic fibers by FE-SEM and averaging them.

  In the case of heat insulation, the content of inorganic fibers in the powder is preferably 0.1% by mass or more with respect to the total mass of the powder from the viewpoint of suppressing the detachment of the powder from the pressure-formed molded body, From the viewpoint of making the thermal conductivity 0.05 W / m · K or less, it is preferably 50% by mass or less.

  When the powder contains infrared opaque particles, the inorganic fiber content is more preferably 0.2% by mass or more and 40% by mass or less from the viewpoint of easy mixing with the infrared opaque particles. From the viewpoint of reducing the density, the content is more preferably 0.2% by mass or more and 20% by mass or less.

  The content of the inorganic fiber can be obtained, for example, by classifying the inorganic fiber from powder.

[1-3] Infrared opacifying particles It is preferable that the powder contains infrared opacifying particles when heat insulation performance at a high temperature is required. The infrared opaque particles refer to particles made of a material that reflects, scatters, or absorbs infrared rays. When infrared opaque particles are mixed in the heat insulating material, heat transfer due to radiation is suppressed, so that the heat insulating performance is particularly high in a high temperature region of 200 ° C. or higher.

  Examples of infrared opaque particles include zirconium oxide, zirconium silicate, titanium dioxide, iron titanium oxide, iron oxide, copper oxide, silicon carbide, gold ore, chromium dioxide, manganese dioxide, graphite and other carbonaceous materials, carbon fibers , Spinel pigments, aluminum particles, stainless steel particles, bronze particles, copper / zinc alloy particles, and copper / chromium alloy particles. Conventionally, the above metal particles or nonmetal particles known as infrared opaque materials may be used alone or in combination of two or more.

  As the infrared opaque particles, zirconium oxide, zirconium silicate, titanium dioxide or silicon carbide is particularly preferable. The composition of the infrared opaque particles is determined by FE-SEM EDX.

  The average particle diameter of the infrared opaque particles is preferably 0.5 μm or more from the viewpoint of heat insulation performance at 200 ° C. or more, and preferably 30 μm or less from the viewpoint of heat insulation performance at less than 200 ° C. due to suppression of solid conduction. The average particle size of the infrared opaque particles is determined by the same method as that for silica particles. Depending on the size of the inorganic fibers and silica particles, when the silica particles are 5 nm to 60 μm, the average particle diameter of the infrared opaque particles is 0.5 μm or more and 10 μm or less from the viewpoint of easy mixing with the silica particles. It is more preferable.

  The content of the infrared opaque particles in the powder is preferably 0.1% by mass or more and 39.5% by mass or less. If the content of the infrared opaque particles is larger than 39.5% by mass, heat transfer by solid conduction is large, so that the heat insulation performance at less than 200 ° C. tends to be low. In order to improve the heat insulation performance at 200 ° C. or higher, the content of the infrared opaque particles is more preferably 0.5% by mass or more and 35% by mass or less, and further preferably 1% by mass or more and 30% by mass or less. A mixed powder obtained by mixing silica-containing powder having an angle of repose of 55 degrees or less and infrared opaque particles is less likely to adhere to the inner wall of a bag or container for storing the powder during transportation. In addition, when taking out the powder from the bag or container, there is an effect that the weight loss of the powder due to adhering to the inner wall of the bag or container is small.

  The content of the infrared opacifying particles can be determined, for example, by measuring the composition of the infrared opacifying particles with FE-SEM EDX and quantifying the elements contained only in the infrared opacifying particles by fluorescent X-ray analysis. it can.

[1-4] Angle of repose The angle of repose of the powder is not less than 35 degrees and not more than 55 degrees. When the angle is less than 35 degrees, for example, powder tends to blow out easily from a joint such as a lid of a mixer. When the angle of repose is more than 55 degrees, for example, the supply line is blocked during the supply of powder, and the supply state tends to become unusable, and the mixing condition tends to change due to the influence of vibration or the like. The reason for this is not clear, but is estimated as follows. The angle of repose is an index for evaluating the fluidity of powder, and a powder having a small angle of repose is excellent in fluidity and has less clogging in the production facility. However, it is presumed that the powder having a small angle of repose and excessively excellent fluidity enters a minute space in the production facility, and as a result, is ejected from a connection location of the production apparatus. On the other hand, with a powder having a large angle of repose, for example, in a bag containing the powder or at a powder filling location, it becomes difficult to flow near the inner wall of the bag or the filling location. Then, it is presumed that other components (particularly particles having a large specific gravity) that have been mixed are separated by vibration and accumulate in the lower layer, resulting in a change in the mixed state. The angle of repose is preferably 35 degrees or more and 53 degrees or less, more preferably 35 degrees or more and 50 degrees or less, and further preferably 38 degrees or more and 50 degrees or less. The angle of repose can be quantified by the method described later.

  Even when the powder contains inorganic fibers and / or infrared opaque particles, the angle of repose of the mixed powder composed of silica particles, inorganic fibers and / or infrared opaque particles is measured, and the mixing ratio is adjusted accordingly. It is preferable. When adding and mixing the infrared opaque particles, the angle of repose of the infrared opaque particles is measured in advance, and the infrared opaque particles having a small angle of repose are used as a raw material, whereby it is easy to prepare a powder. Even when the repose angle of the infrared opaque particles is large, as described above, the repose angle can be adjusted to 55 degrees or less by mixing with other particles (silica particles). When inorganic fibers are added and mixed, it is difficult to measure the angle of repose of the inorganic fibers, so the angle of repose of the powder composed of silica particles and / or infrared opaque particles is set to 35 ° to 55 ° in advance. If inorganic fibers are added and mixed in advance, the angle of repose of the mixed powder tends to be 35 degrees or more and 55 degrees or less.

[1-5] Thermal conductivity The powder of this embodiment has a thermal conductivity at 30 ° C. of 0.05 W / m · K or less. From the viewpoint of heat insulation performance, the thermal conductivity is preferably 0.045 W / m · K or less, more preferably 0.040 W / m · K or less, and even more preferably 0.037 W / m · K or less. The powder containing the infrared opaque particles is preferable particularly when heat insulation performance in a high temperature range of 200 ° C. or higher is required. When the powder contains infrared opaque particles, the thermal conductivity at 800 ° C. is preferably 0.15 W / m · K or less, more preferably 0.14 W / m · K or less, and 0.13 W / m · K or less. Is more preferable. A method for measuring the thermal conductivity will be described later.

  When preparing a powder by mixing a plurality of types of silica particles, for example, small particles and large particles, the silica particles are blended so that the average particle diameter is 5 nm or more and 60 μm or less, and the angle of repose is set as described above. It is preferable to measure the thermal conductivity after setting to 35 degrees or more and 55 degrees or less. When the thermal conductivity is more than 0.05 W / m · K, it is preferable to change the mixing amount in a range in which the angle of repose is maintained in the range of 35 degrees to 55 degrees. In the case of using inorganic fibers and infrared opaque particles, the mixing amount can be similarly determined. When powder is prepared by mixing small particles and large particles, the thermal conductivity tends to be smaller than when the powder is composed only of large particles. For example, when a small particle of about 10 nm and a large particle of about 5 μm are mixed, the mass of the large particle / (the mass of the small particle + the mass of the large particle) is preferably 0.02 to 0.95. It is more preferably 10 to 0.90, and further preferably 0.15 to 0.85. If the mixing amount of the inorganic fibers and the infrared opaque particles is excessive, the heat insulating property may be lowered. Therefore, it is preferable to appropriately prepare while measuring and confirming the thermal conductivity. For example, when inorganic fibers having an average fiber diameter of 12 μm and an average length of 5 mm are mixed with silica, the mixing amount of the inorganic fibers is preferably 30% by mass or less. For example, when infrared opaque particles having an average particle diameter of 2 μm are mixed with silica, the amount of infrared opaque particles to be mixed is preferably 23% by mass or less. Further, when inorganic fibers or infrared opaque particles made of a material having a low thermal conductivity are selected, a mixed powder having a thermal conductivity of 0.05 W / m · K or less tends to be easily prepared.

[1-6] Content of Na, Fe, Ge From the viewpoint of excellent moldability and less powder scattering, the content of Na in the powder of this embodiment is 0 based on the total mass of the powder. It is preferably 0.005% by mass or more and 3% by mass or less, more preferably 0.005% by mass or more and 2% by mass or less, and further preferably 0.005% by mass or more and 1.5% by mass or less. . Similarly, the Fe content is preferably 0.005 mass% or more and 6 mass% or less, more preferably 0.005 mass% or more and 3 mass% or less, and 0.005 mass% or more and 2 mass% or less. More preferably, it is as follows. Similarly, the Ge content is preferably 10 mass ppm or more and 1000 mass ppm or less, more preferably 20 mass ppm or more and 900 mass ppm or less, and 20 mass ppm or more and 800 mass ppm or less. Is more preferable.

  The powder may contain potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), and sulfur (S) in addition to Na, Fe, and Ge. The content of each element is such that the K content is 0.003% by mass to 3% by mass, the Mg content is 0.002% by mass to 2% by mass, and the Ca content is 0.002% by mass or more. 0.5 mass% or less, P content is preferably 0.003 mass% or more and 0.3 mass% or less, and S content is preferably 0.003 mass% or more and 0.3 mass% or less. The content is 0.005 mass% to 2 mass%, the Mg content is 0.002 mass% to 1.8 mass%, the Ca content is 0.002 mass% to 0.4 mass%, More preferably, the P content is 0.003% by mass or more and 0.25% by mass or less, the S content is 0.003% by mass or more and 0.00.2% by mass or less, and the K content is 0. 0.005 mass% or more and 1.5 mass% or less, Mg content is 0.002 mass% or more and 1.6 mass% or less, The a content is 0.002 mass% to 0.2 mass%, the P content is 0.003 mass% to 0.2 mass%, and the S content is 0.003 mass% to 0.1 mass%. More preferably, it is at most mass%. The content of each element such as Na, Fe, and Ge in the powder can be quantified by XRF (fluorescence X-ray analysis).

[2] The method for producing production method of the powder of this embodiment of the powder comprises silica, and small particles having an average particle diameter _{D S} is at 5nm or 30nm or less, comprises silica, average particle diameter _{D L} is 40nm And a step of mixing the large particles having a particle size of 60 μm or less to obtain an inorganic mixture, wherein the repose angle of the small particles is 25 ° to 80 °, and the repose angle of the large particles is 25 ° to 80 °. Yes, the ratio of the mass of the large particles to the total mass of the small and large particles contained in the inorganic mixture, that is, the mass of the large particles / (the mass of the small particles + the mass of the large particles) is 0.02 to 0.95. The manufacturing method to be adjusted.

[2-1] Silica particles Silica particles are particles having a silica component, and the repose angle and the thermal conductivity can be adjusted. For example, the silica particles may be particles produced by condensing silicate ions by a wet method under acidic or alkaline conditions. Silica particles may be obtained by hydrolyzing and condensing alkoxysilane by a wet method, by firing a silica component produced by a wet method, or by burning a silicon compound such as chloride in the gas phase. You may have done. The silica particles may be produced by oxidizing and burning silicon gas obtained by heating a raw material containing silicon metal or silicon. The silica particles may be produced by melting silica or the like.

  The silica particles may contain components other than silica, and examples thereof include those present as impurities in the raw material in the above production method. Components other than silica may be added during the silica production process.

  Known methods for producing silica include the following.

<Silica synthesized by wet method>
Gel silica made from sodium silicate and made acidic.
Precipitated silica made from sodium silicate and made alkaline.
Silica synthesized by hydrolysis and condensation of alkoxysilanes.

<Silica synthesized by dry method>
Fumed silica made by burning silicon chloride.
Silica produced by burning silicon metal gas.
Silica fume by-produced during ferrosilicon production.
Silica produced by the arc method or plasma method.
Fused silica that melts and spheroidizes pulverized silica powder in a flame.

  Of the silica obtained by each manufacturing method, gel method silica made acidic using sodium silicate as a raw material, precipitation method silica made alkaline using sodium silicate as a raw material, silica synthesized by hydrolysis and condensation of alkoxysilane Fumed silica made by burning silicon chloride, silica made by burning silicon metal gas, and silica produced by the arc method or plasma method have an angle of repose of more than 55 degrees. It is possible to adjust the angle of repose to 55 degrees or less by mixing silicas having different average particle diameters by the above-described method. Therefore, a plurality of silica particles, including silica particles obtained by other production methods, can be prepared. It is preferable to mix.

  Silica fume by-produced at the time of ferrosilicon production, etc., and fused silica that melts and spheroidizes pulverized silica powder in a flame have a thermal conductivity of more than 0.05 W / m · K. Therefore, using only the silica obtained by this production method as a raw material for silica particles is not a preferred embodiment in terms of thermal conductivity, but may be useful in terms of cost. It is possible to adjust the thermal conductivity to 0.05 W / m · K or less by mixing silica obtained by other production methods. It is preferable to mix the silica particles obtained by the method. For example, the thermal conductivity of silica particles containing silica fume and the like can be reduced by mixing fumed silica made by burning silicon chloride and silica made by burning silicon metal gas.

  Of the above silica, fumed silica, silica produced by burning silicon metal gas, silica fume, and fused silica are more preferable from the viewpoint of productivity and cost.

  As silica particles, it is possible to use natural silicate minerals. Examples of natural minerals include olivine, chlorite, quartz, feldspar, zeolite and the like. A natural silicate mineral is subjected to a treatment such as pulverization to adjust the average particle diameter, and can be used as silica particles constituting the powder.

[2-2] Na, Fe, Ge, and other elements During the silica production process and the powder production process, they are added as compounds containing Na, Fe, Ge, K, Mg, Ca, P, and S, respectively. However, silica particles containing a sufficient amount of Na, Fe, Ge, K, Mg, Ca, P, and S in advance may be used as the raw material of the powder. Although it does not specifically limit as a compound containing Na, Fe, Ge, K, Mg, Ca, P, S, For example, the oxide of Na, Fe, Ge, K, Mg, Ca, P, S, complex oxide, Examples include hydroxides, nitrides, carbides, carbonates, acetates, nitrates, sparingly soluble salts, and alkoxides. These may be added alone or a mixture thereof may be added. The use of inorganic compound particles containing silica containing Na, Fe, Ge, K, Mg, Ca, P, and S as impurities is a preferred embodiment from the viewpoint of productivity, cost, and workability. is there. Such inorganic compound particles containing silica can be obtained, for example, as silica fume that replicates during the production of silica gel-derived particles or ferrosilicon produced by a precipitation method.

  The method for adding a compound containing each of Na, Fe, Ge, K, Mg, Ca, P, and S is not particularly limited. For example, you may add to the silica obtained by the said wet method or the dry method, and may add in each said manufacturing process of a silica. The compound containing each of Na, Fe, Ge, K, Mg, Ca, P, and S may be water-soluble or insoluble in water. It may be added as an aqueous solution of a compound containing Na, Fe, Ge, K, Mg, Ca, P, and S, respectively, and may be dried as necessary. Na, Fe, Ge, K, Mg, Ca, P, A compound containing S may be added in a solid or liquid state. The compound containing each of Na, Fe, Ge, K, Mg, Ca, P, and S may be previously pulverized to a predetermined particle diameter, or may be preliminarily coarsely pulverized.

  If the silica particles contain an excessive amount of Na, Fe, Ge, K, Mg, Ca, P, S, some treatment is performed during the silica production process or the powder production process, The content may be adjusted to a predetermined range. A method for adjusting an excessive amount of Na, Fe, Ge, K, Mg, Ca, P, and S to a predetermined range is not particularly limited. For example, the method for adjusting the content of Na includes substitution, extraction, removal methods, etc. with an acidic substance or other elements. The inorganic compound particles containing silica are treated with nitric acid or aqua regia, and then dried. It can be used as a raw material for powder. Adjustment of an excessive amount of Na, Fe, Ge, K, Mg, Ca, P, S may be performed after previously pulverizing inorganic compound particles containing silica to a desired particle diameter, or Na, Fe, Ge After adjusting K, Mg, Ca, P, and S to a predetermined range, the silica particles may be pulverized.

[2-3] Mixing method Silica particles, infrared opaque particles and inorganic fibers should be mixed using a known powder mixer, for example, those listed in the revised sixth edition Chemical Engineering Handbook (Maruzen). Can do. At this time, it is possible to mix two or more kinds of inorganic compound particles containing silica, or to mix a compound containing Na, Fe, Ge, K, Mg, Ca, P, and S or an aqueous solution thereof. Known powder mixers include a horizontal cylindrical type, a V type (which may be equipped with a stirring blade), a double cone type, a cubic type, and a shaking type as a container rotating type (the container itself rotates, vibrates and swings). Dynamic rotation type, mechanical agitation type (container is fixed and agitated with blades), single axis ribbon type, double axis paddle type, rotary saddle type, biaxial planetary agitation type, conical screw type, high speed agitation type, rotation Examples of the disk type, the rotating container type with roller, the rotating container type with stirring, the high-speed elliptical rotor type, and the fluid stirring type (stirring by air and gas) include an airflow stirring type and a non-stirring type by gravity. You may use combining these mixers.

  Mixing of silica particles, infrared opacifying particles and inorganic fibers is known as a pulverizer, such as those listed in the revised 6th edition, Chemical Engineering Handbook (Maruzen). You may carry out, cutting a fiber or improving the dispersibility of particle | grains and an inorganic fiber. At this time, it is possible to pulverize and disperse two or more types of silica particles, or to pulverize and disperse a compound containing Ge, Fe, K, Mg, Ca, P, and S and an aqueous solution thereof. Known mills include roll mills (high-pressure compression roll mills, roll rotating mills), stamp mills, edge runners (fret mills, Chillian mills), cutting / shear mills (cutter mills, etc.), rod mills, self-pulverizing mills (erofall mills, Cascade mills), vertical roller mills (ring roller mills, rollerless mills, ball race mills), high-speed rotary mills (hammer mills, cage mills, disintegrators, screen mills, disc pin mills), high-speed rotary mills with built-in classifiers (fixed) Impact plate mill, turbo mill, centrifugal classification mill, annular mill, container drive media mill (rolling ball mill (pot mill, tube mill, conical mill)), vibration ball mill (circular vibration mill, rotational vibration mill, centrifugal mill) ), Planetary mill, centrifugal fluidization mill), medium Stirring mill (tower crusher, stirring tank mill, horizontal flow tank mill, vertical flow tank mill, annular mill), airflow grinder (airflow suction type, nozzle passage type, collision type, fluidized bed) Jet blow type), compaction shear mill (high-speed centrifugal roller mill, inner piece type), mortar, stone mill and the like. You may use combining these grinders.

  Among these mixers and pulverizers, powder mixers with stirring blades, high-speed rotary mills, high-speed rotary mills with built-in classifiers, container drive medium mills, and compaction shear mills improve the dispersibility of particles and inorganic fibers. Therefore, it is preferable. In order to improve the dispersibility of the particles and inorganic fibers, it is preferable to set the peripheral speed of the tip of the stirring blade, rotating plate, hammer plate, blade, pin, etc. to 100 km / h or more, more preferably 200 km / h or more, More preferably, it is 300 km / h or more.

  When mixing a plurality of types of silica particles, it is preferable to introduce the silica particles into a stirrer or a pulverizer in order of increasing bulk specific gravity. In the case where inorganic fibers or infrared opaque particles are included, it is preferable to add and mix infrared opaque particles after mixing silica particles, and then add and mix inorganic fibers.

When preparing a powder by mixing a plurality of types of silica particles, for example, small particles and large particles, each angle of repose is measured in advance, and the angle of repose of the powder after mixing is 35 degrees or more and 55 degrees or less. Thus, it is preferable to adjust the mixing amount. At this time, in order for the repose angle of the powder after mixing to be within the above numerical range, the repose angle of the small particles is 25 degrees or more and 80 degrees or less, but 25 degrees or more and 75 degrees or less. Is more preferable, and it is more preferably 25 degrees or more and 70 degrees or less. Similarly, at this time, the repose angle of the large particles is from 25 degrees to 80 degrees, preferably from 25 degrees to 75 degrees, and more preferably from 25 degrees to 70 degrees. The angle of repose of small particles and large particles before mixing is, for example, changing the surface roughness of the particles by physical treatment or chemical treatment such as surface treatment, making the shape of the particles spherical, and the water content. It is possible to adjust to a preferable range by a method such as changing. The ratio of the mass of the large particles to the total mass of the small particles and the large particles, that is, the mass of the large particles / (the mass of the small particles + the mass of the large particles) is 0.02 It is good to mix so that it may become -0.95, Preferably it may become 0.10-0.90, More preferably, it may become 0.15-0.85. For example, when small particles each having an angle of repose of about 65 degrees and large particles of about 30 degrees are mixed, the mass of large particles / (mass of small particles + mass of large particles) is in the range of 0.05 to 0.85. It is preferable that On the other hand, as described above, even if the angle of repose of each of the small particles and the large particles exceeds 55 degrees, it is possible to adjust the angle of repose to 55 degrees or less by mixing both, so that the average particle and small particles diameter _{D S} is at 5nm or 30nm or less, the mass of the average particle diameter _{D L} is selected large particles is 40nm or more 60μm or less, first both large particle mass / (small particle mass + large particles ) Is 0.5, that is, it is preferable to appropriately adjust the mixing ratio based on the angle of repose measured for the powder mixed so that the mass ratio of the small particles to the large particles is 1: 1. Of course, the silica particles to be mixed are not limited to two types, and three or more types can be mixed.

  When the powder is used for heat insulation, a molded body obtained by pressure-molding the powder as described later can be used as a heat insulating material. However, in the present embodiment, the powder undergoes a process such as molding. Alternatively, the powder can be used as it is simply by filling the portion where the powder is used.

[3] Molded body The molded body contains the powder of the present embodiment. Since such a molded body contains the powder of the present embodiment that can maintain a uniform mixed state, it suppresses variation in performance due to a change in the mixed composition for each molded body. Is possible, and the yield can be improved.

[3-1] Molding method When a molded body is produced by pressure molding powder, a die press molding method (ram type pressure molding method), a rubber press method (hydrostatic pressure molding method), an extrusion molding method, etc. It can be formed by a conventionally known ceramic pressure forming method. From the viewpoint of productivity, a die press molding method is preferable.

When the powder is filled into the mold by a die press molding method or a rubber press method, it is preferable to uniformly fill the powder by vibration or the like because the thickness of the molded body becomes uniform. Filling the mold with powder while decompressing and degassing the inside of the mold is preferable from the viewpoint of productivity because it can be filled in a short time.
The bulk density of the resulting molded article is preferably set from the viewpoint of reducing the burden during transportation so as to ^{0.25g / cm 3 ~2.0g / cm 3} . When trying to control the molding conditions with pressurized pressure, with the passage of time to hold in the pressurized state due to the slipperiness of the powder used, the amount of air taken in between the powder particles and into the pores, etc. Because the pressure value changes, production management tends to be difficult. On the other hand, the method of controlling the bulk density is preferable in that the load of the molded body obtained without requiring time control can be easily set to the target value. Bulk density of the shaped body ^is more preferably ^{0.25g / cm 3 ~1.7g / cm 3} , 0.25g / cm 3 ~1.5g / cm 3 is more preferred.

An example of a method for producing a molded body will be described so that the bulk density of the obtained molded body has a predetermined size. First, the weight of the necessary inorganic mixture is obtained from the volume and bulk density of the molded body. Next, the weighed inorganic mixture is filled in a mold and pressed to a predetermined thickness and molded. Specifically, in the case of producing a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm and a bulk density of 0.5 g / cm ³ , the molded body is multiplied by the volume of the molded body to be manufactured to the target bulk density. It is possible to determine the weight of the powder necessary for the production. That is, in the example of the molded body described above, 0.5 [g / cm ³ ] × 30 [cm] × 30 [cm] × 2 [cm] = 900 [g], and necessary powder is 900 g.
In general, when producing a molded body having a volume αcm ³ and a bulk density of βg / cm ³ (where β is larger than the bulk density of the powder), the powder is weighed by αβg and the powder is made up to the volume α. Form by compressing the body.

  The powder and the molded body during or after pressure molding are heat-dried within the temperature and time conditions where the heat resistance of the powder or molded body is sufficient, and the powder or molded body It is preferable to put it to practical use after removing the adsorbed water because the thermal conductivity is lowered. Furthermore, you may heat-process.

  The molding may be performed only by pressure molding, but it is preferable to heat-treat the pressure molded product. When heat treatment is performed on a powder-molded powder, the compressive strength is improved and the powder can be used particularly suitably in applications where the load is large.

  From the viewpoint of dimensional stability, the heat treatment temperature is preferably higher than the maximum use temperature of the powder or molded product. Although it varies depending on the use of the powder or the molded product, specifically, it is preferably 400 to 1200 ° C, more preferably 500 to 1200 ° C, still more preferably 600 to 1200 ° C.

  The atmosphere for the heat treatment of the powder or compact is in the air (or in the air), in an oxidizing atmosphere (oxygen, ozone, nitrogen oxide, carbon dioxide, hydrogen peroxide, hypochlorous acid, inorganic / organic peroxidation In an inert gas atmosphere (helium, argon, nitrogen, etc.). The heat treatment time may be appropriately selected according to the heat treatment temperature and the amount of the heat insulating material. The heat treatment may be performed after filling the portion where the powder is used, or may be performed on a pressure-molded powder.

[4] Enveloping body The encapsulating body includes an outer covering material and a molded body made of powder and / or powder accommodated in the outer covering material. The encapsulated body has the advantage that it is easier to handle and easier to construct than a powder or molded body. FIG. 1 is a schematic cross-sectional view of an enveloping body according to the present embodiment. FIG. 2 is a schematic cross-sectional view of small particles and large particles contained in the molded product according to this embodiment. As shown in FIG.1 and FIG.2, the envelope 1 of this embodiment is a molded body 2 containing a plurality of small particles S and a plurality of large particles L having a particle diameter larger than that of the small particles S. The outer casing 3 is configured to accommodate the molded body 2. In the molded body 2, the small particles S and the large particles L are mixed, and the small particles S exist around the large particles L. Such a molded body 2 may be referred to as a core material.

[4-1] Cover Material The cover material is not particularly limited as long as it can accommodate the core powder and / or molded body, but examples include inorganic materials such as glass cloth, alumina fiber cloth, and silica cloth. Textile fabric, inorganic fiber knitted fabric, polyester film, polyethylene film, polypropylene film, nylon film, polyethylene terephthalate film, resin film such as fluorine resin film, plastic-metal film, aluminum foil, stainless steel foil, metal foil such as copper foil, Examples include ceramic paper, inorganic fiber nonwoven fabric, organic fiber nonwoven fabric, glass fiber paper, carbon fiber paper, rock wool paper, inorganic filler paper, organic fiber paper, ceramic coating, fluororesin coating, siloxane resin coating, etc. it can. When the encapsulant is a heat insulating material, it is preferable that the thickness of the outer covering material is thin from the viewpoint of reducing the heat capacity of the outer covering material, but it can be appropriately selected according to the use situation, required strength, etc. is there. When the outer cover material is made of a material that is stable at the temperature at which the core material is used, the outer cover material is in a state of accommodating the powder or molded body that is the core material even during use. In the case of an envelope to be used at a high temperature, a highly heat-resistant outer covering material is preferable from the viewpoint of easy handling of the core material after use. In addition to what contains the core material at the time of use, the thing which accommodates the core material in the process of conveyance and construction of the core material is included. In other words, the jacket material protects the core material only during transportation and construction, and includes those that melt and / or volatilize during use, so that the organic material contained in the jacket material itself or the jacket material is the core. It may melt or disappear at the use temperature of the material.

  From the viewpoint that the coating process is easy, inorganic fiber fabrics such as glass cloth, alumina fiber cloth, silica cloth, inorganic fiber knitted fabric, polyester film, polyethylene film, polypropylene film, nylon film, polyethylene terephthalate film, fluorine Resin film such as plastic resin film, plastic-metal film, aluminum foil, stainless steel foil, metal foil such as copper foil, ceramic paper, inorganic fiber nonwoven fabric, organic fiber nonwoven fabric, glass fiber paper, carbon fiber paper, rock wool paper, inorganic Sheet shapes such as filled paper and organic fiber paper are preferred.

  When the enveloping body is used at high temperature, the covering material is made of inorganic fiber woven fabric such as glass cloth, alumina fiber cloth, silica cloth, inorganic fiber knitted fabric, ceramic paper, inorganic fiber non-woven fabric from the viewpoint of thermal stability. Is more preferable. The jacket material is more preferably an inorganic fiber fabric from the viewpoint of strength.

[4-2] Method of coating with outer jacket material The powder contains silica particles, and the powder formed by adding large particles, infrared opacifying particles and inorganic fibers according to the use situation is used as a core material to form a bag. Alternatively, it may be filled with a jacket material processed into a tube shape, or may be formed by pressing this powder into a core material and covering with a jacket material. When the powder is used as the core material, the filling rate of the powder with respect to the volume formed by the jacket material can be appropriately set according to the object using the powder. When the molded body is used as a core material, as described later, both the powder and the jacket material may be pressure-molded, or the powder may be pressure-molded and covered with the jacket material. is there.

  The method for coating the core material with the outer jacket material is not particularly limited, and the core material preparation and molding and the coating with the outer jacket material may be performed simultaneously, or the core material is prepared or molded after the outer jacket material. You may coat with.

  Cover material is inorganic fiber fabric, resin film, plastic-metal film, metal foil, ceramic paper, inorganic fiber nonwoven fabric, organic fiber nonwoven fabric, glass fiber paper, carbon fiber paper, rock wool paper, inorganic filler paper, organic fiber paper, etc. In the case of the sheet-like form, for example, it is possible to cover with stitching with inorganic fiber yarn or resin fiber yarn, adhesion fixing of the jacket material, and both stitching and adhesion.

  When the jacket material is a resin film, a plastic-metal film, a metal foil or the like, a vacuum pack or a shrink pack is preferable from the viewpoint of ease of the coating process.

  When the jacket material is ceramic coating, resin coating, or the like, the core material can be covered with the jacket material by applying the core material with a brush or spray.

  It is also possible to provide the envelope with flexibility by providing a linear recess in the envelope composed of the pressure-molded core material and the jacket material. The form of the line can be selected from a straight line shape, a curved line shape, a broken line shape, and the like according to the usage state of the enveloping body, and two or more of these may be combined. The thickness of the line and the depth of the dent are determined according to the thickness, strength, and usage of the envelope.

  The jacket material may cover the entire surface of the core material, or may partially cover the core material.

[5] Applications The powder, molded product and encapsulant containing silica particles of the present embodiment include a heat absorbing material, a sound absorbing material, a sound insulating material, a sound insulating material, an anti-reflection material, a sound deadening material, an abrasive, a catalyst carrier, It can also be suitably used for carriers that adsorb chemicals such as adsorbents, fragrances and bactericides, deodorants, deodorants, humidity control materials, fillers, pigments and the like.

[6] Measurement of parameters The angle of repose and the thermal conductivity of the powder are measured by the following method. The mixed state of the powder is evaluated by the following method.

[Measurement of angle of repose of powder]
The angle of repose is measured using a repose angle measuring instrument (made by Tsutsui Riken Kikai Co., Ltd.) using a cylinder rotation method. A 500 cc glass sample container (cylindrical measuring bottle) is filled with 250 cc of powder, and the side of the cylindrical measuring bottle is in contact with the roller on the roller part of the measuring device, and the center of the cylindrical measuring bottle. Position the axis so that it is horizontal. Next, the angle between the surface of the powder layer inside the cylindrical measurement bottle and the horizontal plane is measured while rotating the roller section at 2.4 rpm to rotate around the central axis of the cylindrical measurement bottle.

[Measurement of thermal conductivity of powder]
A central portion of a polystyrene foam having a length of 30 cm, a width of 30 cm, and a thickness of 5 cm is hollowed into a square shape having a length of 24 cm and a width of 24 cm to form a foamed polystyrene frame. A concave part is formed by attaching aluminum foil of 30 cm in length and 30 cm in width to one side of the frame to form a sample table. In addition, let the surface covered with aluminum foil be the bottom face of a sample stand, and let the other surface with respect to the thickness direction of a polystyrene foam be a ceiling surface. After the powder is loosely filled into the recesses without being tapped or pressurized and ground, the sample is placed on the ceiling surface with 30 cm long and 30 cm wide aluminum foil. Using the measurement sample, the thermal conductivity at 30 ° C. is measured using a heat flow meter HFM 436 Lambda (trade name, manufactured by NETZSCH). Calibration is performed according to JIS A1412-2 using a NIST SRM 1450c calibration standard plate having a density of 163.12 kg / m ³ and a thickness of 25.32 mm under the condition that the temperature difference between the high temperature side and the low temperature side is 20 ° C. 20, 24, 30, 40, 50, 60, and 65 ° C. in advance. When measuring a compact, a compact with a length of 30 cm, a width of 30 cm, and a thickness of 20 mm is used as a measurement sample. The thermal conductivity at 800 ° C. is measured according to the method of JIS A 1422-1. Two compacts having a disk shape of 30 cm in diameter and 20 mm in thickness are used as measurement samples, and a protective hot plate method thermal conductivity measuring device (manufactured by Eiko Seiki Co., Ltd.) is used as a measuring device.

[Evaluation of powder mixing state]
A cylindrical tank with a capacity of 19L (diameter: 280mm, height: 380mm, made of HDPE) is filled with powder 18L without tapping or pressurizing, and vibration test equipment (interlocking with constant temperature and humidity) (model: J230 / SA3M) , Syn-3HA-40 manufactured by IMV Co., Ltd.) in accordance with the random vibration test method of JIS Z 0232. The acceleration power spectral density follows the acceleration power spectral density shown in Annex A Table 1 of JIS Z 0232, and the vibration time is 30 minutes. After oscillating under the above-mentioned conditions, the filled powder layer is divided into three equal parts, which are the upper part, middle part and lower part, respectively, and the BET specific surface area of the powder in each powder layer is measured. The BET specific surface area of the powder is measured by measuring the specific surface area of the powder using nitrogen as an adsorbed gas with a gas adsorption amount measuring device “Autosorb 3MP” (trade name) manufactured by Yuasa Ionics. Law). The BET method is adopted for the specific surface area. When the mixing state of the powder is changed by vibration and each constituent particle is separated and segregated, the BET specific surface area is changed accordingly. The mixed state is changed by vibration, and for example, the BET specific surface area of the mixed powder where particles having a small particle size are unevenly distributed tends to be larger than the BET specific surface area before vibration. On the other hand, the BET specific surface area where the particles having a large particle diameter and the substance having a small specific surface area such as inorganic fibers are unevenly distributed tends to be smaller than the BET specific surface area before vibration. As a result of studies by the present inventor, when the BET specific surface area of the powder before vibration is 1, and the BET specific surface area after vibration exceeds 1 ± 0.1, the heat insulation performance of the powder varies. Therefore, assuming that the BET specific surface area of the powder before vibration is 1, the mixed state is uniformly maintained if the BET specific surface area is within 1 ± 0.1 in any of the upper, middle and lower parts. If it is more than 1 ± 0.1 in one of the upper, middle and lower parts, the mixed state is not maintained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples. Those skilled in the art can implement various modifications as well as the following embodiments, and such modifications are also included in the scope of the claims of the present invention. In addition, the measurement of the angle of repose, the measurement of thermal conductivity, and the evaluation of the mixed state of the powder in the examples and comparative examples were as described above.

[Example 1]
Example 1 A silica powder of 57% by mass with an angle of repose of 62 ° and an average particle size of 14 nm and 43% by mass of silica powder with an angle of repose of 29 ° and an average particle size of 60 μm were uniformly mixed in a hammer mill. Of powder was obtained. The repose angle of this powder was 53 degrees, and the thermal conductivity at 30 ° C. was 0.0223 W / m · K. When the BET specific surface areas of the powder of Example 1 before and after the vibration test were compared, the BET specific surface areas of the upper, middle, and lower portions of the powder after the vibration test were 1. It was 08, 0.97, and 0.92, and the mixed state was kept uniform. Using this powder 702g, pressure molding is performed with a mold having an inner dimension of 30 cm in length and 30 cm in width to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.39 g / cm ^3. It was. The thermal conductivity of the molded body at 30 ° C. was 0.0225 W / m · K.

[Example 2]
EXAMPLE 2 Silica powder having an angle of repose of 62 degrees and an average particle diameter of 14 nm and 25% by mass of silica powder and 61% of silica powder having an angle of repose of 61 degrees and an average particle diameter of 10 μm were uniformly mixed with a hammer mill. Of powder was obtained. The repose angle of this powder was 40 degrees, and the thermal conductivity at 30 ° C. was 0.0313 W / m · K. When the BET specific surface area before and after the vibration test was compared for this powder, the BET specific surface area of the powder after the vibration test was 1.07, 0.04 and 0.96, and the mixed state was kept uniform. Using 1267 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.70 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0314 W / m · K.

[Example 3]
EXAMPLE 3 Silica powder 50 mass% with an angle of repose of 62 degrees and an average particle diameter of 14 nm and silica powder 50 mass% with an angle of repose of 65 degrees and an average particle diameter of 150 nm were uniformly mixed with a hammer mill. Of powder was obtained. The repose angle of this powder was 41 degrees, and the thermal conductivity at 30 ° C. was 0.0214 W / m · K. When the BET specific surface area before and after the vibration test was compared for this powder, the BET specific surface areas of the upper, middle and lower portions of the powder after the vibration test were 1.05 and 1 respectively. 0.01 and 0.97, and the mixed state was kept uniform. Using 576 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.32 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0211 W / m · K.

[Example 4]
50% by mass of silica powder having an angle of repose of 65 degrees and an average particle diameter of 7.5 nm and 50% by mass of silica powder having an angle of repose of 61 degrees and an average particle diameter of 80 nm were uniformly mixed using a hammer mill. The powder of Example 4 was obtained. The repose angle of this powder was 43 degrees, and the thermal conductivity at 30 ° C. was 0.0199 W / m · K. When the BET specific surface areas of the powder before and after the vibration test were compared, the BET specific surface areas of the upper, middle and lower portions of the powder after the vibration test were 1.06 and 1 respectively. 0.02 and 0.98, and the mixed state was kept uniform. Using 594 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.33 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0198 W / m · K.

[Example 5]
After uniformly mixing 21% by mass of silica powder having an angle of repose of 62 ° and an average particle diameter of 14 nm and 63% by mass of silica powder having an angle of repose of 65 ° and an average particle diameter of 150 nm with a hammer mill, the average particle 16 mass% of zirconium silicate which is an infrared opaque particle having a diameter of 1 μm was added and then mixed uniformly to obtain a powder of Example 5. The repose angle of this powder was 46 degrees, and the thermal conductivity at 30 ° C. was 0.0273 W / m · K. When the BET specific surface area before and after the vibration test was compared for this powder, the BET specific surface area of the upper, middle and lower portions of the silica powder after the vibration test was 1.07, respectively. 1.03 and 0.95, and the mixed state was kept uniform. Using 1042 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.58 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0275 W / m · K. Further, 819 g of each of the powders was used, and pressure molding was performed using a cylindrical mold having an inner diameter of 30 cm to obtain two disk-shaped molded bodies having a diameter of 30 cm and a thickness of 20 mm. Using these two molded bodies, the thermal conductivity at 800 ° C. was measured to be 0.0851 W / m · K.

[Example 6]
After mixing 20% by mass of silica powder with an angle of repose of 62 degrees and an average particle diameter of 14 nm and 60% by mass of silica powder with an angle of repose of 68 degrees and an average particle diameter of 6 μm with a hammer mill, the average particle Add 15% by mass of infrared opacity particles, zirconium silicate, having a diameter of 1 μm, and mix uniformly, and then add 5% by mass of glass fiber having an average fiber diameter of 11 μm and an average fiber length of 6.4 mm Then, it was mixed with a high-speed shear mixer to make it uniform, and the powder of Example 6 was obtained. The repose angle of this powder was 46 degrees, and the thermal conductivity at 30 ° C. was 0.0315 W / m · K. When the BET specific surface area before and after the vibration test was compared for this powder, the BET specific surface area of the upper, middle and lower portions of the silica powder after the vibration test was 1.03, respectively. 0.98 and 0.94, and the mixed state was kept uniform. Using 491 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.27 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0311 W / m · K.

[Example 7]
After uniformly mixing with a hammer mill 19 mass% of silica powder having an angle of repose of 65 degrees and an average particle diameter of 7.5 nm and 57 mass% of silica powder having an angle of repose of 61 degrees and an average particle diameter of 80 nm, Add 14% by mass of zirconium silicate, which is an infrared opaque particle having an average particle diameter of 1 μm, and then mix uniformly, and further 10% by mass of glass fiber having an average fiber diameter of 11 μm and an average fiber length of 6.4 mm Was added and mixed with a high-speed shear mixer to obtain a powder of Example 7. The repose angle of this powder was 47 degrees, and the thermal conductivity at 30 ° C. was 0.0273 W / m · K. When the BET specific surface areas of the silica powder before and after the vibration test were compared, the BET specific surface areas of the upper, middle and lower portions of the silica powder after the vibration test were 1.04 respectively. 0.97 and 0.95, and the mixed state was kept uniform. Using 970 g of this powder, pressure molding was performed using the same mold as in Example 1 to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 20 mm, and a bulk density of 0.54 g / cm ³ . The thermal conductivity of the molded body at 30 ° C. was 0.0272 W / m · K.

[Comparative Example 1]
Using a hammer mill, uniformly mix 90 mass% of silica powder having an angle of repose of 62 degrees and an average particle diameter of 14 nm and 10 mass% of silica powder having an angle of repose of 29 degrees and an average particle diameter of 60 μm, The powder of Comparative Example 1 was obtained. The repose angle of this powder was 58 degrees, and the thermal conductivity at 30 ° C. was 0.0200 W / m · K. When the BET specific surface areas of the powder before and after the vibration test were compared, the BET specific surface areas of the powder after the vibration test were 1.13, 1 0.03 and 0.87, and the mixed state was not maintained.

[Comparative Example 2]
80% by mass of silica powder having an angle of repose of 62 degrees and an average particle size of 14 nm and 15% by mass of infrared opacity particles of zirconium silicate having an average particle size of 1 μm were mixed with a hammer mill to make it uniform. Thereafter, 5% by mass of glass fiber having an average fiber diameter of 11 μm and an average fiber length of 6.4 mm was added and mixed with a high-speed shear mixer to obtain a powder of Comparative Example 2. The repose angle of this powder was 71 degrees, and the thermal conductivity at 30 ° C. was 0.0219 W / m · K. When the BET specific surface areas of the powder before and after the vibration test were compared, the BET specific surface areas of the upper, middle and lower portions of the powder after the vibration test were 1.15 and 0, respectively. .99 and 0.86, and the mixed state was not maintained.

[Comparative Example 3]
The thermal conductivity at 30 ° C. of silica powder having an angle of repose of 29 degrees and an average particle diameter of 60 μm was 0.814 W / m · K.

DESCRIPTION OF SYMBOLS 1 ... Enveloping body, 2 ... Molded object, 3 ... Cover material, S ... Small particle, L ... Large particle.

Claims (13)

  A powder containing silica, having an angle of repose of 35 ° to 55 ° and a thermal conductivity at 30 ° C. of 0.05 W / m · K or less.   The powder according to claim 1, comprising infrared opaque particles and having a thermal conductivity at 800 ° C of 0.15 W / m · K or less.   The infrared opaque particles have an average particle size of 0.5 μm or more and 30 μm or less, and the content of the infrared opaque particles is 0.1% by mass or more and 39.5% by mass or less based on the total mass of the powder. The powder according to claim 2, wherein   The powder according to any one of claims 1 to 3, comprising sodium, wherein the content of the sodium is 0.005 mass% or more and 3 mass% or less based on the total mass of the powder.   The powder according to any one of claims 1 to 4, comprising iron, wherein the iron content is 0.005 mass% or more and 6 mass% or less based on the total mass of the powder.   The powder as described in any one of Claims 1-5 which contains inorganic fiber and content of the said inorganic fiber is 0.1 to 50 mass% on the basis of the total mass of powder. .   The powder according to claim 6, wherein the inorganic fiber has biosolubility.   The powder according to any one of claims 1 to 7, comprising germanium, wherein a content of the germanium is 10 mass ppm or more and 1000 mass ppm or less based on a total mass of the powder.   The molded object containing the powder as described in any one of Claims 1-8. A jacket material;
The powder according to any one of claims 1 to 8 and / or the molded article according to claim 9 accommodated in the jacket material,
An enveloping body comprising   The enveloping body according to claim 10 in which said covering material contains inorganic fiber.   The encapsulant according to claim 10, wherein the covering material is a resin film. It comprises silica, and small particles having an average particle diameter _{D S} is at 5nm or 30nm or less, comprises silica, and large particles having an average particle diameter _{D L} is at 40nm or more 60μm or less, were mixed, the step of obtaining the inorganic mixture Have
The repose angle of the small particles is 25 degrees or more and 80 degrees or less, the repose angle of the large particles is 25 degrees or more and 80 degrees or less, and the small particles included in the inorganic mixture and the total mass of the large particles Adjusting the mass ratio of the large particles to 0.02-0.95,
Powder manufacturing method.

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