JP2016088819A - Powder, molded body thereof and packaged body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder low in electrification characteristic during agitation and low in adhesive force.SOLUTION: There is provided a powder containing a silica particle and an inorganic fiber and the inorganic fiber contains iron of 1 mass% to 40 mass% in terms of FeObased on 100 mass% of the inorganic fiber.SELECTED DRAWING: None

Description

  The present invention relates to a powder, a molded body thereof, and an encapsulated body.

  At room temperature, the mean free path of air molecules is about 100 nm. Therefore, a porous body having a void having a diameter of 100 nm or less suppresses convection by air and heat transfer by conduction, and exhibits a heat insulating action.

In accordance with this heat insulating action, a heat insulating material with low thermal conductivity can be obtained by using ultrafine particles for the heat insulating material. For example, Patent Document 1 is formed by including a plurality of small particles containing silica and / or alumina and having a particle diameter D _S of 5 nm to 30 nm, and the maximum load at a compression rate of 0 to 5% is 0.00. A heat insulating material having a thermal conductivity of 30 MPa or more and 0.05 W / m · K or less and a method for producing the same are disclosed.

International Publication No. 2012/090566

  However, when the above-described heat insulating material is to be put into practical use, there are problems such as handleability other than thermal conductivity. First, when controlling the thermal conductivity, only the structure of the heat insulating material may be specified. For example, if a material with low thermal conductivity, such as silica, is selected, powder is produced, and the porous body is made to have voids shorter than 100 nm, the desired thermal conductivity can be obtained. .

  However, when the above powder is stored for a certain period of time after manufacture, the composition of the powder varies, or the bulk density is distributed due to the weight of the powder. If it does so, before construction or before shaping | molding, another stirring and mixing will be needed. In addition, the powder disclosed in Patent Document 1 also has a problem that it is easily charged and has high adhesion.

  Furthermore, the molded body formed by molding the powder of Patent Document 1 and the fired and cured body thereof are also easily charged similarly to the above powder. When the molded body or the baked cured body is charged, the adhesive force is increased, and due to this, the problem of handling properties such as the surface of the heat insulating material being slippery and the powder adhering during the manufacture of the encapsulant are reduced. This causes problems in manufacturing such as adhesion to the jacket material, causing a sealing failure, and a decrease in yield.

  In view of the above, an object of the present invention is to provide a powder having low chargeability during stirring and low adhesion.

  As a result of intensive studies in order to solve the problems of the conventional technique, the present inventors have found that a powder containing silica particles and specific inorganic fibers can solve the problems of the conventional technique. The present invention has been completed.

That is, the present invention is as follows.
[1] containing silica particles and inorganic fibers,
The inorganic fibers, with respect to the inorganic fibers 100 wt%, an inorganic fiber comprising Fe ₂ O ₃ 40 wt% or more 1 wt% of iron in terms of the following powder.
[2] The powder according to [1], wherein the silica particles include a plurality of small particles having a particle diameter D _S of 5 nm to 30 nm.
[3] The powder according to [1] or [2], further comprising infrared opaque particles.
[4] The powder according to any one of [1] to [3], further comprising alumina particles.
[5] The powder according to any one of [1] to [4], which is used for a heat insulating material.
[6] A molded article comprising the powder according to any one of [1] to [5].
[7] The molded article according to [6], wherein the maximum load at a compression rate of 0% or more and 5% or less is 0.7 MPa or more.
[8] A core material including the powder according to any one of [1] to [5] and / or the molded body according to [6] or [7], and a jacket material that accommodates the core material; An enveloping body.

  According to the powder of the present invention, low chargeability during stirring and low adhesion can be obtained.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiment is an exemplification for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be implemented with various modifications within the scope of the gist.

〔powder〕
The powder of the present embodiment includes silica particles and inorganic fibers, and the inorganic fibers contain iron in an amount of 1% by mass to 40% by mass in terms of Fe ₂ O _{3 with} respect to 100% by mass of the inorganic fibers. Inorganic fiber containing.

<Silica particles>
The powder of this embodiment contains silica particles. The silica particles of the present embodiment refer to particles composed of components represented by the composition formula SiO ₂ and materials containing SiO ₂ , including particles containing metal components, inorganic compounds, etc. in addition to SiO _2. is there. That is, in addition to pure silicon dioxide, the silica particles may contain a salt with Si or various other elements and a composite oxide, or may contain a hydrated oxide such as a hydroxide. Moreover, the silica particle may have a silanol group. Silica in the silica particles may be crystalline, amorphous, or a mixture thereof. It is preferable that the silica of the silica particles is amorphous because heat transfer due to solid conduction is small when used as a heat insulating material, and the heat insulating performance tends to be improved.

  Specific examples of silica particles include silicon oxides such as “silica” and “quartz”; silicon partial oxides; silicon composite oxides such as silica alumina and zeolite; Na, Ca, K, Mg, Ba Silicate (glass) of any one of Ce, B, Fe, and Al; oxides, partial oxides, salts, or complex oxides (alumina, titania, etc.) of elements other than silicon, and oxides of silicon , Partial oxides, salts, or mixtures with complex oxides; oxides such as SiC and SiN.

  Silica is preferably contained in an amount of 50% by mass or more and more preferably 75% by mass or more with respect to 100% by mass of the powder. By including 50 mass% or more of silica, heat transfer due to solid conduction of the powder becomes small, and it tends to be suitable for use as a heat insulating material. By including 75% by mass or more of silica, the cohesive force between the powders is increased and the powder scattering tends to be reduced.

  Depending on the application of the powder, the powder may contain materials other than silica particles and inorganic fibers. Materials other than silica particles will be described in detail later. When the powder contains materials other than silica particles and inorganic fibers, silica is contained in an amount of 50% by mass or more and 99.9% by mass with respect to 100% by mass of the powder. % Is preferably 50% by mass or more and 97.5% by mass or less, and more preferably 60% by mass or more and 97.5% by mass or less. When the silica particles are 50% by mass or more and 97.5% by mass or less, in the case of a powder containing infrared opaque particles and the like, the scattering of the powder is suppressed, and the effect of improving the heat insulation performance at a high temperature is obtained. It tends to appear. Moreover, it exists in the tendency for the bulk density of powder to become smaller because a silica particle is 60 to 97.5 weight%.

  When using a 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 mass of the silica particles does not decrease by 10% or more when held at the maximum use temperature of the heat insulating material for 1 hour. The silica particles preferably have water resistance. Specifically, the amount of silica particles dissolved in 100 g of water at 25 ° C. is preferably less than 0.1 g, 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, and preferably 2.0 or more and 3.0 or less because the bulk density of the heat insulating material tends to be small when the powder is used as a heat insulating material. More preferably, 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.

  The powder of the present embodiment may contain only one kind of silica particles or two or more kinds, and includes two kinds of silica particles having different particle diameters, that is, small particles and large particles made of silica. It is preferable. By including two types of silica particles with different particle sizes, the chargeability and thermal conductivity of small particles and large particles differ. Can be adjusted.

The silica particles of the present embodiment more preferably include a plurality of small particles having a particle diameter D _S of 5 nm to 30 nm, more preferably a plurality of small particles of 5 nm to 25 nm. It is particularly preferred to include a plurality of small particles that are 20 nm or less. By particle diameter D _S is 5nm or more, the silica particles are small particles chemically stable, heat insulating performance is in a stable prone. By particle diameter D _S is 30nm or less, small contact area between the silica particles are small particles, heat transfer is reduced by the powder of the solid conduction, tends to thermal conductivity is reduced. By particle diameter D _S is 25nm or less, there is a tendency that the thermal conductivity becomes smaller.

The particle diameter of the silica particles can be measured by observing with a field emission scanning electron microscope (FE-SEM) and determining the equivalent area equivalent circle diameter. The average particle diameter can be confirmed by observing 100 particles with FE-SEM, obtaining the equivalent area equivalent circle diameter, and calculating the number average. At this time, particles having an equivalent area circle equivalent diameter of less than 35 nm are measured as small particles, the particle diameter of the small particles is taken as the particle diameter D _S , and the average of the particle diameters of the small particles is taken as the D _{S average} . There the more particles 35nm measured as large particles, large particle size particles size of the particles D _L, the average particle diameter of the large particles and D _{L average.}

Silica particles of the present embodiment, D _{L mean,} D _{S mean} <D _{L average} satisfied, more preferably comprising a plurality of small particles is 40nm or more 60μm or less, a plurality of small particles is 40nm or more 10μm or less Is more preferable, and it is particularly preferable to include a plurality of small particles having a size of 40 nm to 5 μm. When the DL _average is 40 nm or more, the spring back tends to be small when the powder is molded. When the DL _average is 60 μm or less, the thermal conductivity tends to be small. When the _{DL average} is 10 μm or less, the inorganic fibers and infrared opaque particles in the powder tend to be uniformly mixed. When the _{DL average} is 5 μm or less, the adhesion force of the particles is large, and the dropout of the particles from the powder tends to be reduced.

The D _{L average} is preferably at least twice the _{DS average} , more preferably at least 3 times, and even more preferably at least 4 times. When it is twice or more, the springback tends to be small when the powder is molded. By being 3 times or more, the bulk specific gravity of the powder in which the small particles and the large particles are mixed tends to be large, the powder volume is small, and the workability tends to be high. By being 4 times or more, the difference in particle size between the small silica particles and the large silica particles is large, and the large silica particles tend to be easily dispersed with respect to the small silica particles. When the dispersibility of the silica particles is good, the solid heat conductivity tends to be small when the powder is used as a heat insulating material.

<Inorganic fiber>
Powder of the present embodiment, the inorganic fibers 100 wt%, including inorganic fibers containing iron 1 mass% to 40 mass% in terms of Fe ₂ O _3. By including inorganic fibers containing 1% by mass or more and 40% by mass or less of iron in terms of Fe ₂ O ₃ , the chargeability of the powder is suppressed, and adhesion to the stirring vessel is reduced during stirring. The reason for this is not clear, but there is a reduced Fe compound, etc., as compared with FeO and FeO, which are iron oxides. As a result, this interacts electrically with the powder and suppresses charging during stirring. Guessed. In addition, since the inorganic fiber has a shape with a high aspect ratio, it can be efficiently contacted with the powder and the stirring container at the time of stirring. Is done.

Specifically, as iron of this embodiment, Fe; FeO, Fe ₂ O ₃ , iron oxide such as Fe ₃ O ₄ ; iron hydroxide such as Fe (OH) ₂ and Fe (OH) ₃ ; FeOOH, etc. Iron oxyhydroxide; iron salts such as iron sulfide, iron sulfate, iron nitrate, iron acetate, iron oxalate, iron carbonate, iron chloride, iron phosphate; NaFeO ₂ , NaFe ₂ O ₃ , KFeO ₂ , K ₂ FeO ₄ , CaFeO ₂ , CaFe ₂ O ₄ , MgFe ₂ O _{4 and} other iron oxide salts; NaFeSiO ₃ , FeSiO _{4 and} other iron silicates; NaFeSi ₂ O ₆ , KFeSi ₂ O ₆ , CaFeSi ₂ O ₆ , MgFeSi ₂ O Iron silicates such as ₆ ; iron aluminates such as FeAl ₂ O ₄ ; iron aluminates such as Na (Fe _0.75 Al _0.25 ) O ₂ , Ca ₂ FeAlO ₅ , MgFeAlO ₄ ; Fe and Ti such as FeTiO ₃ Composite oxide of NaTiFeO ₄ , K Examples thereof include salts of complex oxides of Fe and Ti such as FeTi ₃ O ₈ , CaFeTi ₂ O ₆ , and MgFeTi ₄ O ₁₀ .

The iron of this embodiment is more preferably 1% by mass to 30% by mass and more preferably 1% by mass to 25% by mass in terms of Fe ₂ O _{3 with} respect to 100% by mass of the inorganic fibers. It is particularly preferably 2% by mass or more and 25% by mass or less, and particularly preferably 5% by mass or more and 25% by mass or less. When the amount of iron is 30% by mass or less, heat insulation performance tends to be excellent. When the amount is 25% by mass or less, inorganic fibers are difficult to cut and the strength tends to be excellent. The dispersibility tends to be improved, and when it is 5% by mass or more, the cohesive force with the powder is increased and the scattering of the powder tends to be suppressed.

With Fe ₂ O ₃ conversion, the total amount of each component contained in the inorganic fiber converted as an oxide is 100% by mass of the inorganic fiber, and the iron according to this embodiment is converted into the mass converted to Fe ₂ O _3. It is. Specifically, it calculates | requires by the measuring method described in an Example.

When the inorganic fiber can be classified from the powder, the mass ratio of iron in the inorganic fiber is determined by fluorescent X-ray measurement according to the following method. After mixing 1 g of inorganic fiber and 1 g of Fungusel II powder of crystalline cellulose powder (trade name, manufactured by Funakoshi Co., Ltd.) for 30 minutes in a mortar, 2 g of the mixed powder is a ring made of vinyl chloride having an inner diameter of 25 mm, a thickness of 5 mm, and a width of 3 mm. The sample is filled in and pressed into a thickness of 3 mm with a press machine to obtain a measurement sample. A total qualitative analysis of this sample is performed, and the mass of Fe in terms of Fe ₂ O ₃ is determined by the fundamental parameter method, with the component form being an oxide. Funacell II powder is excluded from the calculation as flux. For example, when a scanning fluorescent X-ray analyzer ZSX Primus II (trade name, manufactured by Rigaku Corporation) is used as the fluorescent X-ray measuring device, the compound as a flux of composition C ₆ H ₁₀ O ₅ is used in advance. By registering, the sample model is bulk, the component form is oxide, the flux is Funasel II powder, the dilution rate is 1, and the SQX calculation is performed to determine the mass% of Fe ₂ O ₃ .

  Moreover, when the inorganic fiber in a heat insulating material cannot be classified from powder for reasons, such as sintering, it calculates | requires by measuring the iron content of the inorganic fiber seen in the cross section of a heat insulating material by SEM-EDX.

  The inorganic fiber of the present embodiment preferably has a ratio (aspect ratio) of the average length of the inorganic fiber to the average thickness of the inorganic fiber of 10 or more, more preferably 50 or more, and 100 or more. Some are more preferred. When the aspect ratio is 10 or more, the powder tends to be molded with a small pressure when it is molded. Moreover, it exists in the tendency which improves the productivity of a molded object because an aspect-ratio is 50 or more. Furthermore, when the aspect ratio is 100 or more, the bending strength of the molded product tends to be excellent.

  The aspect ratio of the inorganic fiber is determined from the average value of the thickness and length of 100 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 a bundle in which a plurality of inorganic fibers are aligned in the same direction. Absent. In addition, the inorganic fibers may be in a monodispersed state in which the directions of the inorganic fibers are aligned in the same direction. However, from the viewpoint of reducing the thermal conductivity, the inorganic fibers are preferably oriented in a direction perpendicular to the heat transfer direction.

Specific 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 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 fiber (mullite fiber) (Al ₂ O ₃ —SiO ₂ ), silica fiber (SiO ₂ ), alumina fiber (Al ₂ O ₃ —SiO ₂ ), basalt fiber (SiO ₂ —Al _{2 O 3 -Fe 2 O 3 -MgO} -CaO), potassium titanate fibers, alumina whiskers, silicon carbide whiskers, silicon nitride whiskers, calcium carbonate whiskers, basic sulfate Magnesium whisker, calcium sulfate whisker (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, brucite and the like. These inorganic fibers are not particularly limited as long as they contain 1% by mass or more and 40% by mass or less of iron in terms of Fe ₂ O ₃ .

When preparing these inorganic fibers, by using a raw material containing iron or adjusting the amount used, an inorganic fiber containing 1 mass% or more and 40 mass% or less of iron in terms of Fe ₂ O ₃ is obtained. Can do.

Inorganic fibers are preferably those containing SiO ₂ from the viewpoint of heat insulation performance. It can be confirmed by the above-mentioned XRF that the inorganic fiber contains SiO ₂ . Specific examples of the material containing SiO ₂ 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-resistant 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 fiber (mullite fiber) (Al ₂ O ₃ —SiO ₂ ), silica fiber (SiO ₂ ), alumina fiber (Al ₂ O ₃ —SiO ₂ ), basalt fiber (SiO _{2 —} Al ₂ O ₃ —Fe ₂ O ₃ —MgO—CaO), AES (Alkaline Earth Silicate) fiber (SiO ₂ —CaO—MgO), natural mineral wallus Tonite, sepiolite, attapulgite and the like can be mentioned.

The inorganic fibers, from the viewpoint of heat resistance, those containing Al ₂ O ₃ is preferred. It can be confirmed by the above-mentioned XRF that the inorganic fiber contains Al ₂ O ₃ . As including al ₂ O _3, specifically, long glass fibers _{(filaments) (SiO 2 -Al 2 O 3} -B 2 O 3 -CaO), glass wool _{(SiO 2 -Al 2 O 3 -CaO} -Na2O ), 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 fiber (mullite fiber) ( Al ₂ O ₃ —SiO ₂ ), alumina fibers (Al ₂ O ₃ —SiO ₂ ), basalt fibers (SiO ₂ —Al ₂ O ₃ —Fe ₂ O ₃ —MgO—CaO), natural mineral attapulgite and the like. .

  The average thickness of the inorganic fibers is preferably 1 μm or more from the viewpoint of preventing scattering. When using as a heat insulating material, it is preferable that it is 20 micrometers or less from a viewpoint of suppressing the heat transfer by solid conduction. The average thickness of the inorganic fibers is determined by calculating the thickness of 100 inorganic fibers by FE-SEM and averaging them.

  The inorganic fiber of the present embodiment is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more with respect to 100% by mass of the powder. 10 mass% or less is still more preferable. When the inorganic fiber is 0.1% by mass or more, the chargeability tends to be suppressed. Moreover, it exists in the tendency for heat conductivity to become small because inorganic fiber is 20 mass% or less. Furthermore, when the content is 0.5% by mass or more and 20% by mass or less, the influence of the adhesion of fibers to the mixing container wall is reduced, and the reproducibility of the fiber content tends to be improved. When it is 15% by mass or less, there is a tendency that mixing does not occur and the mixing becomes easy. It tends to occur less easily and productivity tends to be good.

  Depending on the inorganic fiber, a surface treatment with a high insulating property may be applied, but after removing the surface treatment agent with a high insulating property such as washing the inorganic fiber, it is also possible to use it as a raw material for powder. It is.

<Infrared opaque particles>
It is preferable that the powder of this embodiment further contains infrared opaque particles from the viewpoint of obtaining heat insulation performance at a high temperature. An infrared opaque particle refers to a particle containing a material that reflects, scatters, or absorbs infrared light. When infrared opaque particles are included in the powder, heat transfer due to radiation is suppressed, so that the heat insulation performance particularly in a high temperature region of 200 ° C. or higher tends to be high.

  Specific 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 fiber, spinel pigment, aluminum particles, stainless steel particles, bronze particles, copper / zinc alloy particles, copper / chromium alloy particles, and the like. These metal particles or non-metal particles may be used alone or in combination of two or more.

  Of these infrared opaque particles, zirconium oxide, zirconium silicate, titanium dioxide, and silicon carbide particles are preferred. The composition of the infrared opaque particles is determined by FE-SEM EDX.

The average particle size of the infrared opaque particles is preferably 0.5 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 10 μm or less. When the average particle diameter is 0.5 μm or more, the heat insulation performance at 200 ° C. or more tends to be excellent, and when the average particle diameter is 30 μm or less, the heat insulation performance at less than 200 ° C. due to suppression of solid conduction. It tends to be excellent. Also, depending on the size of the inorganic fibers and silica particles, when the average particle diameter D _S and D _L of the silica particles is 5nm or more 50μm or less, an average particle diameter of the infrared opacifying particles 0.5μm or 10μm or less Therefore, mixing with silica particles tends to be easy. The average particle size of the infrared opaque particles is determined by the same method as that for the silica particles described above.

  The infrared opaque particles are preferably more than 0% by mass and 49.5% by mass or less, and more preferably 2% by mass to 30% by mass with respect to 100% by mass of the powder. When the infrared opaque particles are 49.5% by mass or less, heat transfer due to solid conduction is small, and heat insulation performance at less than 200 ° C. tends to be high. When the infrared opaque particles are 2% by mass or more, the heat insulation performance at 200 ° C. or higher tends to be improved, and when the infrared opaque particles are 30% by mass or less, mixing with silica particles is easy. Tend to be.

  The mass ratio of the infrared opaque particles is determined by measuring the composition of the infrared opaque particles by SEM-EDX, examining the elements contained only in the infrared opaque particles, and then quantifying the elements by fluorescent X-ray analysis. Can be sought.

<Alumina particles>
The powder of the present embodiment preferably further contains alumina particles from the viewpoint of obtaining high heat resistance. Alumina particles refer to particles containing a material represented by the composition formula Al ₂ O ₃ . The alumina particles contained in the powder may be particles containing a material represented by pure Al ₂ O ₃ , or may be a particle containing a salt of Al and various other elements or a composite oxide material. Specifically, composite oxides containing aluminum oxide (α-alumina, γ-alumina, β-alumina, θ-alumina, fumed alumina, amorphous alumina, etc.), aluminum hydroxide, aluminum, and the like ( And particles containing an oxide material obtained by oxidizing the surface of silica alumina, zeolite, etc.), aluminum carbide, aluminum nitride and the like.

  Among these alumina particles, particles containing materials of α-alumina, γ-alumina, θ-alumina, and fumed alumina are preferable from the viewpoint of achieving both heat insulation performance and heat resistance. In addition, particles containing α-alumina material are more preferred because the bulk density of the powder increases during molding and the molding tends to be easy.

  It can confirm that the particle | grains containing the material of (alpha)-alumina, (gamma) -alumina, and (theta) -alumina are contained in the molded object by measuring the powder X-ray-diffraction measurement (XRD) of a porous body. Specifically, the XRD pattern has a JCPDS card number 46-1212 for α-alumina, a JCPDS card number 23-1009 for γ-alumina, and a JCPDS card number 35-0121 for θ-alumina. This can be confirmed by having a peak. In addition, in α-alumina, it can be confirmed that the d value is 2.5508 (Å), 1.6016 (Å), 2.0853 (Å), 3.49797 (Å), and in γ-alumina, the d value is 1.3883 (Å), 2.8370 (Å), 2.7300 (Å), 2.4440 (Å), and θ-alumina has a d value of 2.7300 (Å), 1. 3880 (Å), 2.8400 (Å), and 2.3120 (Å).

The alumina particles preferably contain 1% by mass to 80% by mass of aluminum in terms of Al ₂ O _{3 with} respect to 100% by mass of the powder, more preferably 1% by mass to 40% by mass. More preferably, the content is from 25% to 25% by mass. When the alumina particles are contained in an amount of 1% by mass or more, a change in the heat insulating performance of the molded body tends to be suppressed when exposed to a temperature exceeding 900 ° C. When the alumina particles are contained in an amount of 80% by mass or less, an increase in the mass of the molded body and a decrease in heat insulation performance tend to be suppressed. By containing 25% by mass or less of alumina particles, the adhesion of powder tends to be reduced.

  The mass ratio of the alumina particles is determined by fluorescent X-ray measurement by the same method as that for measuring the content of silica particles.

  The powder preferably further contains a water repellent from the viewpoint of preventing water from penetrating into the powder or the molded body to reduce handling properties, deformation of the molded body, cracking, and the like. Specific examples of water repellents 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 fluoroalkylcarboxylates, perfluoroalkyl phosphates, perfluoroalkyltrimethylammonium salts, silane coupling agents such as alkoxysilanes containing alkyl groups and perfluoro groups, trimethylsilyl chloride and 1,1 Silylating agents such as 1,3,3,3-hexamethyldisilazane and the like. 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. Among these, a wax-based water repellent and a silicon-based water repellent are preferable.

  From the viewpoint of imparting a sufficient water repellent effect, the ratio of the mass of the entire powder to the mass of the water repellent is preferably from 100/30 to 100 / 0.1, and preferably from 100/20 to 100 / 0.5. More preferably, it is 100/10 or more and 100/1 or less.

[Production method of powder]
The method for producing a powder according to the present embodiment preferably includes a mixing step of mixing a powder containing silica particles and an inorganic fiber containing 1 mass% or more and 40 mass% or less of iron in terms of Fe ₂ O _3. .

  As the silica particles, particles having a silica component produced by a conventional production method can be used as a raw material. Specifically, the silica particles used as a raw material are produced by condensing silicate ions by a wet method under acidic or alkaline conditions, and produced by hydrolyzing and condensing alkoxysilane by a wet method. Inorganic compound particles containing silica, silica particles produced by firing a silica component produced by a wet method, and the like. The inorganic compound particles containing silica may be produced by burning a silicon compound such as chloride in the gas phase. Further, the silica particles may be produced by oxidizing and burning silicon gas obtained by heating a raw material containing silicon metal or silicon, or may be produced by melting silica.

  A natural silicate mineral can be used as the inorganic compound particles containing silica. Specific examples of natural minerals include olivine, chlorite, quartz, feldspar, and zeolite.

  Components other than the silica component contained in the silica particles may be used as impurities in the raw material in the above production method, or may be added during the silica production process.

The following are mentioned as a manufacturing method of a well-known silica.
(Silica synthesized by wet method)
Gel silica produced with sodium silicate as a raw material.
Precipitated silica produced with alkalinity from sodium silicate.
Silica synthesized by hydrolysis and condensation of alkoxysilanes.
(Silica synthesized by dry method)
Fumed silica produced 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.

  Among 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.

[Mixing process]
In the mixing step of the present embodiment, at least silica particles and inorganic fibers may be mixed, and infrared opaque particles and alumina particles may be further mixed. Silica particles and inorganic fibers can be mixed using a mixer (specifically, those listed in the revised sixth edition Chemical Engineering Handbook (Maruzen), etc.). Specifically, as a mixer, a container rotating type (the container itself rotates, vibrates and swings) is 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. Dynamic rotating type; mechanical stirring type (container is fixed and stirred with blades, etc.), single axis ribbon type, double axis paddle type, rotary saddle type, biaxial planetary stirring type, conical screw type, high speed stirring type, rotation As a disk type, a rotating container type with a roller, a rotating container type with stirring, a high-speed elliptical rotor type; a flow stirring type (stirring by air or gas), an airflow stirring type, a non-stirring type by gravity and the like can be mentioned. These mixers may be used in combination.

  The mixing process uses a pulverizer (specifically, those listed in the Revised Sixth Edition Chemical Engineering Handbook (Maruzen), etc.) to pulverize particles, cut inorganic fibers, You may mix, improving the dispersibility of a fiber.

  Specific examples of pulverizers include roll mills (high-pressure compression roll mills, roll rotating mills), stamp mills, edge runners (fret mills, Chillian mills), cutting and shearing mills (cutter mills, etc.), rod mills, and self-pulverizing mills (Erofol). Mill, cascade mill, etc.), vertical roller mill (ring roller mill, rollerless mill, ball race mill), high-speed rotary mill (hammer mill, cage mill, disintegrator, screen mill, disc pin mill), high-speed rotary mill with built-in classifier (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 fluidizing mill) Medium agitation mill (tower crusher, agitation tank mill, horizontal flow tank mill, vertical flow tank mill, annular mill), airflow crusher (airflow suction type, nozzle passage type, collision type, flow) Layer jet blowing type), compaction shear mill (high-speed centrifugal roller mill, inner piece type), mortar, stone mill and the like. These pulverizers may be used in combination.

  Among these mixers and pulverizers, powder mixers with stirring blades, high-speed rotary mills, high-speed rotary mills with built-in classifiers, container drive media mills, compaction shear mills, particles such as silica particles and inorganic fibers This is preferable because the dispersibility tends to be improved. From the viewpoint of further improving the dispersibility of particles such as silica particles and inorganic fibers, the peripheral speed at the tips of stirring blades, rotating plates, hammer plates, blades, pins, etc. is preferably 100 km / h or more, and 200 km / h. h or higher is more preferable, and 300 km / h or higher is further preferable.

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

  When using the powder as a heat insulating material, it may be used as it is without filling the part where the powder is used without going through a molding process or the like. May be.

  The compact containing the powder of the present embodiment can be obtained by pressure molding the powder of the present embodiment. Specific examples of methods for pressure forming powders include: die press molding method (ram type pressure molding method), rubber press method (hydrostatic pressure molding method), extrusion molding method, and conventionally known ceramic pressing. Examples include molding methods. Among these, the die press molding method is preferable from the viewpoint of productivity.

  When filling a mold with powder by a mold press molding method or a rubber press method, it is likely that the thickness of the molded body tends to be uniform, such as by giving vibration to the powder uniformly. preferable. Moreover, filling the mold with the powder while reducing the pressure and degassing the mold is preferable from the viewpoint of productivity because it can be molded in a short time.

The bulk density of the molded body is preferably from 0.25 g / cm ³ or more 2.0 g / cm ³ or less, more preferably 0.25 g / cm ³ or more 1.7 g / cm ³ or less, 0.25 g / cm ³ or more 1 More preferably, it is 5 g / cm ³ or less. When the bulk density is 0.25 g / cm ³ or more and 2.0 g / cm ³ or less, the burden during transportation tends to be reduced. A specific measuring method is measured by the method described in the examples described later.

  Molding may be controlled by the pressure of pressurization, or may be controlled by the bulk density of the molded body. However, when the molding conditions are controlled by the pressure of the pressurization, the time of holding in the pressurized state depends on the slipperiness of the powder used, the amount of air taken in between the particles of the powder and the pores, etc. The pressure value changes with time. On the other hand, when controlling by the bulk density of the molded body, it is preferable because the maximum load of the obtained molded body can be easily set to the target value without requiring time control, and production management tends to be facilitated.

  In the molded body of the present embodiment, the maximum load at a compression rate of 0% or more and 5% or less is preferably 0.7 MPa or more. A specific measuring method is measured by the method described in the examples described later.

  The powder or the molded body during or after pressure molding is heat-dried within the temperature and time conditions within which 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 tends to be improved, and in particular, it tends to be suitably used in applications where the load on the molded body is large.

  From the viewpoint of dimensional stability, the temperature of the heat treatment 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 molded product, it is preferably 400 ° C. or higher and 1200 ° C. or lower, more preferably 500 ° C. or higher and 1200 ° C. or lower, and further preferably 600 ° C. or higher and 1200 ° C. or lower.

  Specifically, the atmosphere for the heat treatment of the powder or molded body is in the air (or in the air), in an oxidizing atmosphere (oxygen, ozone, nitrogen oxide, carbon dioxide, hydrogen peroxide, hypochlorous acid) And inorganic / organic peroxides), and 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.

[Encapsulation]
The enveloping body of this embodiment is provided with the core material containing the above-mentioned powder and / or the above-mentioned molded object, and the outer covering material which accommodates a core material. Note that the powder or the molded body may be referred to as a core material.

<Coating material>
The jacket material of the present embodiment is not particularly limited as long as it can accommodate a core material including powder and / or a molded body, and specifically, inorganic fibers such as glass cloth, alumina fiber cloth, silica cloth, and the like. Woven fabric, inorganic fiber knitted fabric, polyester film, polyethylene film, polypropylene film, nylon film, polyethylene terephthalate film, resin film such as fluororesin film, plastic-metal film, metal foil such as aluminum foil, stainless steel foil, copper foil, ceramic Examples include 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, and other resin coatings.

  The thickness of the jacket material is preferably selected from the viewpoint of reducing the heat capacity of the jacket material when the enveloping body is used as a heat insulating material. Is possible.

  When the outer cover material is stable even at the temperature at which the core material is used, the outer cover material can be in a state of containing powder or a molded body that is the core material even during use. In the case of an enveloping body used at a high temperature, an outer covering material having high heat resistance is preferable from the viewpoint of easy handling of the core material after use. However, the “cover material” in the present specification includes not only the core material that is accommodated when the core material is used, but also the material that accommodates the core material in the process of transporting or constructing the core material. 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 the jacket material itself and the organic components contained in the jacket material are It may melt or disappear at the use temperature of the material.

  As the covering 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, Resin film such as fluorine 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, Sheet-shaped paper such as inorganic filled paper, organic fiber paper and the like is preferable.

  When the enveloping body is used at a high temperature, as the covering material, from the viewpoint of thermal stability, inorganic fiber fabrics such as glass cloth, alumina fiber cloth, silica cloth, inorganic fiber knitted fabric, ceramic paper, An inorganic fiber nonwoven fabric is more preferable. As the jacket material, an inorganic fiber fabric is more preferable from the viewpoint of strength.

  The encapsulant includes silica particles and inorganic fibers, and further, depending on the use situation, a powder formed by adding silica particles having a relatively large diameter, infrared opaque particles, and alumina particles, as a core material, What was filled in the jacket material processed into the bag shape or the tube shape may be used. Further, the powder may be formed by pressing the powder into a molded body, which is then used as a core material and covered 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 set as appropriate according to the object using the powder. When using the molded body 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. It is.

  The method of coating the core material with the jacket material is not particularly limited, and the core material may be prepared or molded and coated with the jacket material at the same time, or the core material may be coated with the jacket material after preparation or molding. May be.

  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 In the case of a sheet-like form such as, specifically, it is possible to cover with sewing with inorganic fiber yarn or resin fiber yarn, adhesive fixing of the jacket material, both sewing and bonding, etc. .

  When the sheet-shaped outer covering 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 formed by ceramic coating, resin coating, or the like, the core material can be coated with the jacket material by applying the core material with a brush or spray.

  It is also possible to provide a linear recess in the enveloping body including the core material and the outer covering material that have been pressure-molded, thereby imparting flexibility to the enveloping body. 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.

  When using a jacket material having thermal adhesiveness, a bag making and filling machine can be used. Specifically, as a bag making and filling machine, it has the function of filling, sealing, and cutting powder while making bags, and the function of sealing the envelope material after making it into a bag that has been cut and filled with powder. And the like. In order to fill the powder into the bag, a chute (a bowl-like or tubular tool for flowing the powder from a high place to a low place) is used. There is a tendency that adhesion of the powder to the sealing surface is suppressed.

  The enveloping body of this embodiment becomes easier to handle than powders and molded bodies, and tends to be excellent in workability.

  It is preferable to use the powder, the molded body, and the encapsulated body of this embodiment for a heat insulating material. By being used for a heat insulating material, a heat insulating material having low thermal conductivity and excellent handleability and manufacturability can be obtained. The powder, molded body, and encapsulant 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, an adsorbent, an fragrance, or a sterilizer. It can also be preferably used for a carrier that adsorbs a drug such as an agent, a deodorant, a deodorant, a humidity control material, a filler, a pigment, and the like.

  Hereinafter, the present embodiment will be described in more detail with specific examples and comparative examples, but the present embodiment is not limited by these examples and comparative examples unless they exceed the gist thereof. . In the following Examples and Comparative Examples, powders and molded products were evaluated as follows.

(1) Composition analysis by XRF for inorganic fiber, measurement of iron content 1 g of inorganic fiber and 1 g of Funacelle II powder (trade name, manufactured by Funakoshi Co., Ltd.) of crystalline cellulose powder for 30 minutes in a mortar, and then 2 g of mixed powder Was filled in a ring made of vinyl chloride having an inner diameter of 25 mm, a thickness of 5 mm, and a width of 3 mm, and press-molded to a thickness of 3 mm by a press machine to obtain a measurement sample for fluorescent X-ray analysis. A compound model is previously registered as a flux of composition C6H10O5 in a scanning X-ray fluorescence analyzer ZSX Primus II (trade name, manufactured by Rigaku Co., Ltd.), and a sample model is bulky after a qualitative analysis of the measurement sample. The component form is oxide, the flux is Funasel II powder, the dilution rate is 1, and the SQX calculation is performed to convert the iron contained in the inorganic fiber to Fe ₂ O ₃ with respect to 100% by mass of the inorganic fiber. The content (mass%) was measured. Similarly, the content was measured for various compositions as described in Table 1 by converting silicon to SiO ₂ and converting aluminum to Al ₂ O ₃ and content (% by mass).

(2) Charge amount evaluation by powder agitation and adhesion evaluation 50 g of a powder sample was put in a 2 L φ140 mm SUS304 container equipped with a stirring seal, and two SUS316 75 φmm 4-paddles with an angle were attached. A SUS316 agitation shaft was attached to an agitation motor SM-101 (manufactured by As One Co., Ltd.) via an agitation seal, and the container was sealed and rotated at 3000 rpm for 1 minute. Thereafter, the container lid was opened, the container was rotated 180 degrees, and the internal powder was discharged. At that time, the charge amount (nC / g) of the powder was measured using a Coulomb meter NK-1001 and Faraday cage KQ-1400 manufactured by Kasuga Electric Co., Ltd. In the adhesion evaluation, the mass (g) of the powder that adhered to the container and could not be collected was measured.

(3) Measurement of bulk density of molded body and fired and cured body By measuring the size and mass of a sample of about 30 cm in length, about 30 cm in width and about 20 mm in thickness, and a sample of the fired and cured body, and dividing the mass by the volume. The bulk density (g / cm ³ ) was measured.

(4) Measurement of thermal conductivity at 30 ° C. of molded body and fired and cured body A molded body that is a porous body molded into a shape having a length of about 30 cm, a width of about 30 cm, and a thickness of about 20 mm and its fired and cured body were used as samples. The thermal conductivity (W / m · K) at ° C. was 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.

(5) Evaluation of chargeability of molded body and fired cured body In a constant temperature and humidity chamber at a temperature of 20 ° C. and a humidity of 50% RH using an electrostatic charge diffusivity measuring device NS-D100 (trade name, manufactured by Nano Seeds Co., Ltd.) Then, the distance from the corona discharge site and the surface potential meter was set to 10 mm with respect to the molded body formed into a disk shape having a diameter of about 4 cm and a thickness of 10 mm and the sample which was the fired and cured body. Charging by corona discharge from a 6 kV needle electrode was performed for 10 seconds, and the surface potential (kV) after 1 second and 10 seconds after corona charging was measured with a surface potentiometer. The measurement was performed according to JIS C 61340-2-1.

(6) Measurement of maximum load of fired and cured body A cube having one side equal to the thickness of the porous body is cut out from a sample that is a fired and cured body, and is produced by a precision universal testing machine Autograph AG-100KN (manufactured by Shimadzu Corporation) ) Was used to measure the maximum load (MPa) at a compression rate of 0% or more and 5% or less of the sample with respect to the thickness.

[Example 1]
1600 g of fumed silica having an average particle diameter of 14 nm, 4000 g of silica fume having an average particle diameter of 120 nm, 1200 g of zirconium silicate, and 800 g of α-alumina were uniformly mixed with a hammer mill to obtain a mixed powder.

3960 g of this mixed powder and 40 g of basalt fiber having an iron content of 26.9% in terms of Fe ₂ O ₃ , an average fiber diameter of 13 μm, and an average fiber length of 6 mm were mixed with a high-speed shear mixer, Got the body. The charge amount evaluation and adhesion evaluation (above (2)) were performed by stirring this powder. Table 1 shows the results of composition analysis by XRF of (1) above in the inorganic fibers of the inorganic fibers, and Table 2 shows the results of chargeability evaluation and adhesion evaluation.

In order to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 2 cm, and a bulk density of 0.40 g / cm ³ , 720 g of the above-obtained powder was filled in a 30 cm long and 30 cm wide mold and pressed. Molded to obtain a molded body having a bulk density of 0.40 g / cm ³ . The thermal conductivity of the above (4) at 30 ° C. of this molded body was evaluated. The results are shown in Table 2.

In order to obtain a molded body having a diameter of 4 cm, a thickness of 1 cm, and a bulk density of 0.40 g / cm ³ , 5 g of the above-obtained powder was filled in a 4 cm diameter mold and pressure-molded. A molded body of 0.40 g / cm ³ was obtained. The chargeability of (5) above of this molded product was evaluated. The results are shown in Table 2.

In order to obtain a molded body having a length of 30 cm, a width of 30 cm, a thickness of 2 cm, and a bulk density of 0.50 g / cm ³ , 900 g of the powder obtained above was filled in a 30 cm long and 30 cm wide mold and pressed. Molded to obtain a molded body having a bulk density of 0.50 g / cm ³ . This molded body was fired at 1000 ° C. for 1 hour to obtain a fired and cured body having a thickness of 1.8 cm and a bulk density of 0.62 g / cm ³ . The thermal conductivity at 30 ° C. of (4) above and the compressive strength of (6) above were evaluated for this fired cured product. The results are shown in Table 2.

In order to obtain a molded body having a diameter of 4 cm, a thickness of 1.2 cm, and a bulk density of 0.50 g / cm ³ , 8 g of the above-obtained powder was filled in a 4 cm diameter mold, and pressure-molded. A disk-shaped molded body having a density of 0.50 g / cm ³ was obtained. This molded body was fired at 1000 ° C. for 1 hour to obtain a fired and cured body having a thickness of 1.0 cm and a bulk density of 0.62 g / cm ³ . The chargeability of the above (5) was evaluated for this fired and cured product. The results are shown in Table 2.

Two more fired and cured bodies having a thickness of 1.8 cm and a bulk density of 0.62 g / cm ³ were prepared, and two disk-shaped samples having a diameter of 28 cm and a thickness of 1.8 cm were prepared by cutting. It was 0.115 (W / m * K) when the heat conductivity in 800 degreeC was measured with the protection hot plate method thermal conductivity measuring apparatus (made by Eihiro Seiki Co., Ltd.). The results are shown in Table 2.

[Comparative Example 1]
A powder was obtained in the same manner as in Example 1 except that E glass fiber having an average fiber diameter of 10 μm and an average fiber length of 6 mm was used as the inorganic fiber. The composition analysis by XRF of the inorganic fiber (1) is shown in Table 1. The charge amount evaluation and adhesion evaluation (above (2)) were performed by stirring this powder. The results are shown in Table 2.

Except for the obtained powder, a molded body having a length of 30 cm, a width of 30 cm, a thickness of 2 cm, and a bulk density of 0.40 g / cm ³ was obtained in the same manner as in Example 1, and the heat conduction at 30 ° C. of (4) above. Rate was evaluated. The results are shown in Table 2.

Except for the obtained powder, a molded body having a diameter of 4 cm, a thickness of 1 cm, and a bulk density of 0.40 g / cm ³ was obtained in the same manner as in Example 1, and the chargeability of the above (5) was evaluated. The results are shown in Table 2.

Except for the obtained powder, as in Example 1, a shaped body having a length of 30 cm, a width of 30 cm, a thickness of 2 cm, and a bulk density of 0.50 g / cm ³ was fired at 950 ° C. for 1 hour, and the thickness was 1.8 cm. A fired and cured body of 0.62 g / cm ³ was obtained. The thermal conductivity at 30 ° C. of (4) above and the compressive strength of (6) above were evaluated for this fired cured product. The results are shown in Table 2.

Except for the obtained powder, it was obtained in the same manner as in Example 1 so that a molded body having a diameter of 4 cm, a thickness of 1.2 cm, and a bulk density of 0.50 g / cm ³ was obtained. 8 g of the obtained powder was filled and pressure-molded to obtain a disk-shaped molded body having a bulk density of 0.50 g / cm ³ . This molded body was fired at 950 ° C. for 1 hour to obtain a fired and cured body having a thickness of 1.0 cm and a bulk density of 0.62 g / cm ³ . The chargeability of the above (5) was evaluated for the fired cured product. The results are shown in Table 2.

Claims (8)

Silica particles and inorganic fibers,
The inorganic fibers, with respect to the inorganic fibers 100 wt%, an inorganic fiber comprising Fe ₂ O ₃ 40 wt% or more 1 wt% of iron in terms of the following powder. The powder according to claim 1, wherein the silica particles include a plurality of small particles having a particle diameter D _S of 5 nm or more and 30 nm or less.   The powder according to claim 1 or 2, further comprising infrared opaque particles.   The powder according to any one of claims 1 to 3, further comprising alumina particles.   The powder according to any one of claims 1 to 4, which is used for a heat insulating material.   The molded object containing the powder of any one of Claim 1 to 5.   The molded product according to claim 6, wherein the maximum load at a compression rate of 0% or more and 5% or less is 0.7 MPa or more.   An enveloping comprising: a core material including the powder according to any one of claims 1 to 5 and / or the molded body according to claim 6 or 7; and an outer covering material that accommodates the core material. body.