JPWO2020009226A1 - Insulation filler, insulation, insulation structure - Google Patents

Abstract

It is a heat insulating filler containing a mixed silica powder consisting of 10% by mass to 80% by mass of dry silica and 20% by mass to 90% by mass of wet silica having a water content of 2% by mass or more, with respect to 100 parts by mass of the mixed silica powder. It is preferable that the inorganic fiber contains 1 part by mass to 10 parts by mass, and the inorganic fiber preferably has an average fiber diameter of 0.1 μm to 50 μm.

Description

The present invention relates to a heat insulating filler, a heat insulating material, and a heat insulating structure.

In recent years, the demand for heat insulating materials has been increasing more and more in order to suppress heat dissipation energy from the viewpoint of energy saving. In addition to conventional applications such as housing, piping, blast furnaces, and electric furnaces, heat insulating materials are attracting attention not only from the viewpoint of heat retention of internal combustion engines and fuel cells, for example, and can be applied to various shapes not limited to molded bodies. Insulation material is required.

Since the mean free path of air near room temperature is 100 nm, it is well known that a porous body containing fine pores of 100 nm or less exhibits excellent heat insulating properties. There are various types of such porous heat insulating materials, and examples thereof include inorganic porous heat insulating materials using silica fine particles produced by a dry method as shown in Patent Documents 1 to 5. This is because the fluid heat transfer is suppressed by forming a fine porous structure by the dry silica containing fine pores, so that it exhibits excellent heat insulating properties.

Many of the forms of use as a heat insulating material in the above-mentioned prior art are based on a molded body formed by mechanical pressing, and many studies have been made to improve dust generation and strength after molding as in the above-mentioned patent documents. ing. At this time, in order to obtain a uniform molded body, the powder used is required to have good fluidity that can be uniformly filled in the mold. However, the dry silica fine particles have a problem of handleability in the manufacturing process in order to exhibit strong adhesion and ejection property due to a small bulk density and Coulomb force.

Further, as shown in Patent Documents 6 and 7 about a heat insulating material produced by filling a bag-shaped outer skin material with powder, a heat insulating layer is formed by filling the space with powder by the flow of powder. There is a method of forming, and a heat insulating powder having excellent filling property is required. However, filling by flow replaces the air in the target space with powder, so it is not suitable for dry silica fine particles having a very small bulk density.

Patent Document 8 describes a method for producing a heat insulating material in which a mixture containing 1) silica fine particles as a main component, 2) reinforcing fibers, and 3) a liquid storage substance impregnated with water is wet-molded and dried. doing. Patent Documents 9 and 10 describe a heat insulating board in which two or more kinds of fine particles having different primary particle diameters are filled. However, Patent Documents 8 to 10 do not describe the water content.

Japanese Patent No. 4860005 Japanese Unexamined Patent Publication No. 7-237957 Japanese Patent No. 05081464 Japanese Patent No. 4367612 Special Table No. 11-513349 Japanese Patent No. 5738717 Japanese Unexamined Patent Publication No. 2013-1596 Japanese Patent No. 5409939 Japanese Unexamined Patent Publication No. 1-199095 Japanese Unexamined Patent Publication No. 1-135998

The present invention has been made in view of the above problems and background, and an object of the present invention is to provide a heat insulating filler having good heat insulating properties and capable of exhibiting excellent filling properties.

As a result of diligent studies in view of the above problems and background, the present inventors have solved the problem with a heat insulating filler containing mixed silica powder obtained by mixing dry silica fine particles and wet silica fine particles in a predetermined ratio. I found that it could be solved. That is, the present invention is as follows.

[1] A heat insulating filler containing a mixed silica powder containing 10% by mass to 80% by mass of dry silica and 20% by mass to 90% by mass of wet silica having a water content of 2% by mass or more.
[2] The heat insulating filler according to [1], which contains 1 part by mass to 10 parts by mass of inorganic fibers with respect to 100 parts by mass of the mixed silica powder.
[3] The heat insulating filler according to [2], wherein the inorganic fibers have an average fiber diameter of 0.1 μm to 50 μm.
[4] The heat insulating filler according to any one of [1] to [3], which contains radiant scattering particles.
[5] The heat insulating filler according to any one of [1] to [4], wherein the dry silica has an average particle size of 0.8 μm or less, and the wet silica has an average particle size of 1 μm or more.
[6] The heat insulating filler according to any one of [1] to [5], which is a solid.
[7] A heat insulating material obtained by blending the heat insulating filler according to any one of [1] to [6].
[8] A heat insulating structure including the heat insulating material according to [7].

According to the present invention, it is possible to provide a heat insulating filler having good heat insulating properties and capable of exhibiting excellent filling properties. As a result, excellent heat insulating effect and heat retaining effect can be provided for various shaped objects.

The details of the present invention will be described below.
[1. Insulation filler]
The heat insulating filler according to one embodiment of the present invention (the present embodiment) is a mixture of 10% by mass to 80% by mass of dry silica and 20% by mass to 90% by mass of wet silica having a water content of 2% by mass or more. Contains silica powder.

Specifically, in the present embodiment, low thermal conductivity can be maintained by the fine pore structure formed by dry silica, and the charge on the surface is diffused by the moisture in the wet silica, so that the adhesiveness is improved. As a result, it is presumed that the fluidity is improved and excellent filling property is exhibited. Furthermore, it was found that the fluidity was further improved by the aggregation of the mixed silica powder in which these were mixed and the attachment of the mixed silica fine particles to the inorganic fibers.

The "dry silica" used in the present invention is a general term for amorphous silica substances produced by a dry method, and those produced by any method such as a combustion method or an arc method can be used. The combustion method is, for example, a method of reacting silicon tetrachloride in a high-temperature flame. Dry silica (preferably dry silica fine particles) is particles containing fine pores and gives a fine porous structure in the mixed silica powder. Therefore, from the viewpoint of reducing the thermal conductivity, the content is preferably 10% by mass to 80% by mass and preferably 30 to 70% by mass. If it is less than 10% by mass, sufficient heat insulating properties may not be exhibited, and if it exceeds 80% by mass, sufficient powder fluidity cannot be ensured and the filling property may be lowered.

The "wet silica" used in the present invention is a general term for amorphous silica substances produced by a wet method, and those produced by any method such as a precipitation method or a gel method can be used. The precipitation method is, for example, a method in which an aqueous solution of sodium silicate is neutralized to precipitate silica, which is then filtered and dried. The wet silica (preferably wet silica fine particles) is particles that suppress the adhesion and ejection property of the powder by adhering dry silica around itself. The content is preferably 20% by mass to 90% by mass and preferably 30 to 70% by mass from the viewpoint of fluidity and adhesiveness when the mixed silica powder is prepared. If it is less than 20% by mass, good handleability may not be exhibited, and even if it is added in excess of 90% by mass, further improvement of the effect cannot be expected. Here, the mixed silica powder is a powder obtained by mixing dry silica and wet silica with arbitrary inorganic fibers (and radiation scattering particles if necessary).

Moisture contained in the mixture of dry silica and wet silica has the role of suppressing the van der Waals force acting on the particles. This water content is not particularly limited as long as it is 2% by mass or more with respect to the mass of the wet silica. If it is less than 2% by mass, the adhesiveness increases due to static electricity acting on the particles, so that good handleability may not be exhibited. The water content of the wet silica is preferably 3 to 15% by mass, more preferably 5 to 10% by mass.

Further, the water content of the mixed silica powder obtained by mixing dry silica and wet silica is preferably 2 to 8% by mass, more preferably 3 to 7% by mass, from the viewpoint of good handleability. preferable.

The water content of the dry silica, wet silica, and mixed silica is raised to 200 ° C. by a thermogravimetric analyzer (TGA), and the water content W is calculated using _{the weight X before the temperature rise and the reduced weight X 1.} ..
Moisture content W (mass%) = (X ₁ / X) x 100

Fumed silica and respective average particle size of wet silica (50% cumulative particle diameter D ₅₀ that is measured by the more specifically a laser diffraction particle size analyzer (Coulter "Model LS-230" _type)) is zero. The average particle size of the dry silica is preferably 10 μm or less, preferably 01 μm to 100 μm, and from the viewpoint of suppressing fluid heat transfer. Further, in order to improve the fluidity of the mixed silica powder and suppress the ejection property, the average particle size of the wet silica is preferably larger than that of the dry silica.

The average particle size of the dry silica is preferably 1 μm or less, more preferably 0.8 μm or less, and most preferably 0.5 μm or less. The average particle size of the dry silica is preferably 0.01 μm or more, more preferably 0.03 μm or more, and most preferably 0.05 μm or more. The average particle size of the wet silica is preferably 0.5 μm or more, more preferably 1 μm or more, and most preferably 5 μm or more. The average particle size of the wet silica is preferably 50 μm or less, more preferably 30 μm or less, and most preferably 20 μm or less.

In the present embodiment, it is preferable to further mix the inorganic fiber with the mixed silica powder.
The inorganic fiber used in the present invention is not particularly limited as long as it improves the filling property by fiber imposition of the mixed silica powder, and any inorganic fiber can be used. In addition, it has a role of imparting moldability to the heat insulating filler during molding. Typical examples are silica fiber, alumina silica fiber, glass fiber, zirconia fiber, silicon carbide fiber, rock wool manufactured from minerals, natural mineral wollastonite, sepiolite, etc., which are artificial fibers with excellent heat resistance. However, one or more of these can be used as needed.

The average fiber diameter of the inorganic fibers is an average value of the diameters of 100 fibers confirmed by scanning electron microscope (SEM) observation. The average fiber diameter is preferably 0.1 μm to 50 μm, and since the probability of adhesion of silica fine particles is increased and the ejection property of powder can be suppressed, 1 μm or more is more preferable, and 5 μm or more is most preferable.

The average fiber length of the inorganic fibers is not particularly limited, but is preferably 10 μm or more, more preferably 15 to 35 μm in consideration of the filling property of the mixed silica powder.
The average fiber length of the inorganic fibers can be determined as the average value of the fiber lengths of 100 fibers confirmed by scanning electron microscope (SEM) observation.

The content of the inorganic fiber is preferably 1 part by mass to 10 parts by mass, and more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the mixed silica powder.
When it is 1 part by mass or more, sufficient moldability is easily exhibited, and when it is 10 parts by mass or less, contact between fibers is suppressed, material heat conduction is reduced, and thermal conductivity can be lowered. ..

The adiabatic filler of the present invention can further contain radiant scattering particles in order to improve the adiabatic properties at high temperatures (200 ° C. or higher). The radiant scattering particles are not particularly limited as long as they can effectively scatter or absorb infrared rays, and for example, silicon carbide, zirconium oxide, titanium oxide, copper oxide and the like can be used, and one or more of these particles can be used. Seeds may be used.
The amount of the radiant scattering particles used is preferably 0.5% by mass to 35% by mass, more preferably 1.0% by mass to 20% by mass, based on 100% by mass of the heat insulating filler.

The thermal conductivity of the heat insulating filler obtained by the present invention is preferably 0.05 W / (m · K) or less, preferably 0.029 W / (m · K) or less at 25 ° C. Is more preferable.

The sparsely filled bulk density is the density obtained when powder is dropped from a certain height into a ground container and filled, and the powder is ground.

Insulation filler obtained in the present invention is preferably loosely packed bulk density in the state of the mixed silica powder from the viewpoint to approach the packing density designed is 40 kg / m ³ or more, it is 50~80kg / m ³ More preferred. When the content is 40 kg / m ³ or more, sufficient filling property is exhibited, voids do not increase too much, and sufficient heat insulating property can be easily obtained.

The method for producing the heat insulating filler is not particularly limited, and for example, dry silica 10% by mass to 80% by mass and wet silica having a water content of 2% by mass or more of 20% by mass to 90% by mass are several mm. Examples thereof include a method of obtaining by mixing with a grinding mill having a clearance of the above, and a method of obtaining by biaxial mixing in which these are mixed with metal blades while being wound up by an air stream.
The heat insulating filler of the present embodiment as described above can be used as a solid. In addition, it can be used as a powder in a solid.

[2] Insulation Material The heat insulating material according to the present embodiment contains the above-mentioned heat insulating filler.
Specifically, it is a heat insulating layer or a heat insulating material obtained by filling the above-mentioned heat insulating filler as a raw material. For example, a heat insulating layer obtained by filling a space using the flow of powder. Therefore, a heat insulating material obtained by pressurizing and filling a mold can be mentioned.

The detailed method for obtaining by pressure filling is not particularly limited, but for example, it may be molded into a plate shape by a dry uniaxial press using a die. However, dry molding is preferable from the viewpoint of molding defects due to the generation of voids and cracks during drying.

Further, the heat insulating material according to the present embodiment may be formed by covering the entire heat insulating filler described above with an outer skin material. The outer skin material is preferably a sheet-shaped material such as an inorganic fiber woven fabric such as glass fiber or alumina fiber, an inorganic fiber non-woven fabric, a resin film, an organic fiber woven fabric, an organic fiber non-woven fabric, or a metal foil such as aluminum or copper foil. It is not particularly limited.

The coating method is not particularly limited, and the filling rate of the heat insulating filler can be appropriately set depending on the intended use. For example, the pressure-molded heat-insulating filler may be coated with the above-mentioned sheet, or the sheet may be processed into a bag shape and filled with the heat-insulating filler.

[3] Insulation structure The insulation structure according to the present embodiment includes the above-mentioned heat insulating material.
The heat insulating filler according to the present embodiment may be used as it is as a heat insulating material, but may be combined with other heat insulating materials to form a heat insulating structure. When used in combination with other heat insulating materials, for example, in a heat insulating structure composed of a laminated structure filled and laminated on another heat insulating material having different heat resistance, the heat insulating material is added to the heat insulating filler according to the present embodiment. It can be said that it is a combined layered heat insulating structure. Further, a heat insulating structure may be formed in which a hollow box is filled with the heat insulating filler according to the present embodiment as a heat insulating material.

Hereinafter, the contents will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

"Experimental Example 1"
A heat insulating filler was prepared by mixing dry silica and wet silica at the mixing ratio shown in Table 1 and mixing 4.5 parts by mass of inorganic fibers with 100 parts by mass of the mixture (mixed silica powder).

For these dry silica, wet silica, mixed silica powder, heat insulating filler, etc., the water content, the ratio of the sparsely packed bulk density, and the thermal conductivity were measured, respectively. The results obtained are shown in Table 1. The materials used are as follows.

(Material used)
Dry silica 1 (F1): CAB-O-SIL M-5 powder (trade name, manufactured by Cabot Specialty Chemicals) Average particle size 0.20 μm, bulk density 70 g / L, moisture content 0.9% by mass
Dry silica 2 (F2): AEROSIL 380 (trade name, manufactured by Nippon Aerosil Co., Ltd.) Average particle size less than 0.05 μm, bulk density 50 g / L, moisture content 1.0 mass%
Dry silica 3 (F3): NDK-N20 (trade name, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.) Average particle size 0.15 μm, bulk density 40 g / L, moisture content 1.2% by mass

Wet silica 1 (W1): CARPLEX # 80 powder (trade name, manufactured by Ebonic Japan Co., Ltd.) Average particle size 15 μm, bulk density 145 g / L, moisture content 8.0% by mass
Wet silica 2 (W2): Toxile NP (trade name, manufactured by Oriental Silicon Corporation) average particle size 10 μm, bulk density 63 g / L, moisture content 6.2 mass%
Wet silica 3 (W3): Mizukasil P-527 (trade name, manufactured by Mizusawa Industrial Chemicals, Inc.) Average particle size 1.8 μm, bulk density 190 g / L, moisture content 5.2 mass%

Inorganic fiber 1 (IF1): Silica fiber sheet AS-300 (trade name, manufactured by Asahi Sangyo Co., Ltd.) Average fiber diameter 10 μm, 25 mm cutting and defibration processing (average fiber length: 25 mm)

The bulk density of the material used is the tightly packed bulk density, and is measured by "Powder Tester PT-S type" manufactured by Hosokawa Micron Co., Ltd.

(Evaluation method)
Moisture content: The water content of dry silica, wet silica, and mixed silica powder was determined as the weight reduction rate at 200 ° C. using a differential thermogravimetric analyzer TG-DTA 2000SR (trade name, BrukerAXS).

The sparsely filled bulk density was determined by dropping a heat insulating filler from a funnel and grinding it into a stainless steel beaker having an inner diameter of Φ63 mm and a capacity of 200 mL at intervals of 150 mm. The larger the sparse filling bulk density, the better the filling property, preferably 40 kg / m ³ or more.

Thermal conductivity: A molded body (200 mm × 200 mm × 20 mm, density 230 kg / m ³ ) is prepared by molding the prepared heat insulating filler with a uniaxial press, and a thermal conductivity measuring device (ISO8301 compliant). It was measured at 23 ° C. using a product manufactured by Eiko Seiki Co., Ltd.

Moldability: A molded product (dimensions, etc.) was produced by mold molding using a uniaxial press, and the moldability was visually evaluated. The case where no crack was confirmed in the molded body was evaluated as ◯, and the case where crack or breakage was confirmed was evaluated as x.

From Table 1, it can be seen that as the proportion of wet silica increases, the packing property of the powder is improved without adversely affecting the thermal conductivity, and the water content, the sparsely packed bulk density, and the moldability are improved. ..

"Experimental Example 2"
Dry silica F1 was mixed at a ratio of 50% by mass and wet silica W1 was mixed at a ratio of 50% by mass, and the inorganic fibers shown in Table 2 were used with respect to the obtained mixture (mixed silica powder: Experiment No. 1-4). As shown in Table 2, the same procedure as in Experimental Example 1 was carried out except that the heat insulating filler was prepared by changing the blending amount. The results are shown in Table 2.

(Material used)
Inorganic fiber 2 (IF2): Glass fiber (manufactured by Nippon Electric Glass Co., Ltd.) Average fiber diameter 50 μm, average fiber length 25 mm
Inorganic fiber 3 (IF3): Alumina silica fiber (trade name: Denka Arsen, manufactured by Denka) Average fiber diameter 5.0 μm, average fiber length 25 mm

From Table 2, by blending the inorganic fibers within the scope of the present invention, the filling property of the powder is improved without adversely affecting the thermal conductivity, and the water content, the sparse filling bulk density, and the moldability are improved. You can see that there is.

"Experimental Example 3"
Experiment No. Except for the fact that the compounding of 1-4 was used, the radiant scattering particles shown in Table 3 were used, the compounding amount was changed as shown in Table 3, and the thermal conductivity (high temperature thermal conductivity) at a high temperature (600 ° C.) was measured. Was carried out in the same manner as in Experimental Example 1.

(experimental method)
High-temperature thermal conductivity: A protective heat plate method thermal conductivity measuring device that complies with JIS A 1412-1 by producing a molded body (dimensions, etc.) of the prepared heat insulating filler by die molding using a uniaxial press. It was measured at 600 ° C. using (manufactured by Eiko Seiki Co., Ltd.).

(Material used)
Radiant scattering particles (R1): Silicon carbide (manufactured by Denka) Average particle size 4.2 μm
Radiant scattering particles (R2): Titanium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Average particle size 5.0 μm
Radiant Scattered Particles (R3): Zirconium Zirconium Wako First Class (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Average particle size 5.0 μm

From Table 3, it can be seen that the high temperature thermal conductivity is reduced by blending the radiant scattering particles within the range of the present invention without adversely affecting other physical characteristics.

The heat insulating filler of the present invention constructed as described above has excellent operability and filling property, and also has heat resistance and heat insulating property higher than those of the conventional one, so that it can be applied to a complicated shape. It can contribute to energy saving of vehicles, airplanes, other internal combustion engines, and piping.

Claims (8)

A heat insulating filler containing a mixed silica powder containing 10% by mass to 80% by mass of dry silica and 20% by mass to 90% by mass of wet silica having a water content of 2% by mass or more. The heat insulating filler according to claim 1, which contains 1 part by mass to 10 parts by mass of inorganic fibers with respect to 100 parts by mass of the mixed silica powder. The heat insulating filler according to claim 2, wherein the inorganic fibers have an average fiber diameter of 0.1 μm to 50 μm. The heat insulating filler according to any one of claims 1 to 3, which contains radiant scattered particles. The heat insulating filler according to any one of claims 1 to 4, wherein the dry silica has an average particle size of 0.8 μm or less, and the wet silica has an average particle size of 1 μm or more. The heat insulating filler according to any one of claims 1 to 5, which is a solid. A heat insulating material obtained by blending the heat insulating filler according to any one of claims 1 to 6. A heat insulating structure including the heat insulating material according to claim 7.