JP2012081701A - Heat insulating material and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulating material that prevents desorption of inorganic fine particles from a heat insulating molding as a base material, has a highly smooth surface preventing cracks on its outer surface, and is free from any restriction on working temperature and shape.SOLUTION: On the heat insulating molding containing nano-particles, a coating layer is formed which contains aluminum phosphate of 5-50 mass%, inorganic particles of 0.5-10 μm in arithmetic mean particle diameter and of 40-90 mass%, and an inorganic binder of 0-10 mass% in terms of solid content. The coating layer has an intruding part through which a component constituting the coating layer intrudes into the heat insulating molding on an interface with the heat insulating molding.

Description

  The present invention relates to a heat insulating material and a method for manufacturing the heat insulating material.

  Conventionally, a nanoparticle, that is, a heat insulating material obtained by pressure-molding inorganic fine particles such as silica fine particles, alumina fine particles, and aluminum silicate fine particles having a primary particle diameter of about 3 to 1000 nm, and the above inorganic fine particles Further, a heat-insulating molded article obtained by molding a reinforcing fibrous material or milky white material that suppresses transmission of radiant light to improve a heat insulating effect and then press-molds the same has been known.

The heat insulating molded body formed from the inorganic fine particles has a large specific surface area with a BET specific surface area of 15 to 500 m ² / g, and the large specific surface area is a secondary particle formed by pressurizing the inorganic fine particles. Is provided by having a ring-shaped hole. That is, in the ring-shaped hole, movement of molecules such as nitrogen molecules and oxygen molecules constituting the air is restricted and confined inside the ring-shaped hole, so that collision between the molecules is suppressed and convection is caused. Heat transfer becomes small, and it becomes possible to provide a heat insulating molded body with low thermal conductivity.

  A method of performing pressure molding of the inorganic fine particles in the presence of a binder is also conceivable, but in this case, if the binder content increases, the number of contacts between the inorganic fine particles increases, and the solid heat transfer increases. Therefore, the above molding is usually performed in a state where no binder is present or in a state where the amount of the binder is reduced as much as possible.

  On the other hand, since the heat-insulating molded product has a reduced binder content, the bonding force between the fine particles is small, the surface is very brittle, and the surface inorganic fine particles are easily detached. Yes, when manufacturing or constructing a heat insulating material containing the above inorganic fine particles, inorganic fine particles adhere to the worker to reduce workability, or when using indoors where a blower is installed, a large amount of inorganic Fine particles are scattered.

  Therefore, a heat insulating material in which the surface of the heat insulating molded body is covered with a surface layer material made of a metal film, a plastic film, a woven fabric made of glass fiber, etc. is known, but this heat insulating material is used depending on the type of the surface layer material. The temperature is limited, and there is a limitation on the form that it can be applied only to a flat plate-like heat insulating molded body.

  Further, a heat insulating material (see Patent Document 1 (Japanese Patent Laid-Open No. 61-106476)) on which a dense coating made of glaze is formed on the surface, and a heat insulating material whose surface is densified with a binder or the like (Patent Document 2 (special No. 2005-36975)) has also been reported.

  However, the heat insulating material described in Patent Document 1 is one in which the surface film itself is cracked or peeled off by sintering of the glaze, and the heat insulating material described in Patent Document 2 is formed by heat insulating molding. Since the inorganic fine particles on the body surface are aggregated, the outer surface of the heat insulating material is cracked. For this reason, the heat insulating materials described in Patent Document 1 and Patent Document 2 have technical problems such as poor appearance and separation of inorganic fine particles from surface cracks.

  In addition, the airgel fused with nanoparticles can also exhibit low thermal conductivity, and it is considered that a heat insulating material made of aerogel reinforced with a fibrous material can also exhibit low thermal conductivity. Like the heat insulating material made, the surface has a technical problem of being fragile.

JP 61-106476 A JP 2005-36975 A

  The present invention has been made in view of such circumstances, and has high smoothness that suppresses the release of inorganic fine particles from the heat-insulating molded body that is a base material and suppresses the occurrence of cracks on the outer surface. An object of the present invention is to provide a heat insulating material that has a surface and is hardly subject to restrictions on use temperature and shape, and a method for manufacturing the heat insulating material.

  In order to solve the above technical problem, the present inventors have conducted intensive studies. On the heat-insulating molded body containing nanoparticles, 5 to 50% by mass of aluminum phosphate in terms of solid content, arithmetic average A coating layer containing 40 to 90% by mass of inorganic particles having a particle diameter of 0.5 to 10 μm and 0 to 10% by mass of an inorganic binder is formed, and the coating layer is an interface with the heat insulating molded body. The present inventors have found that the above technical problem can be solved by a heat insulating material having a penetrating portion through which the component constituting the coating layer penetrates the heat insulating molded body.

That is, the present invention
(1) On a heat-insulating shaped product comprising nanoparticles,
A coating layer containing 5 to 50% by mass of aluminum phosphate, 40 to 90% by mass of inorganic particles having an arithmetic average particle size of 0.5 to 10 μm, and 0 to 10% by mass of an inorganic binder is formed in terms of solid content. Being
The heat insulating material, wherein the coating layer has a penetrating portion through which the components constituting the coating layer penetrate into the heat insulating molded body at the interface with the heat insulating molded body,
(2) When the total content of aluminum phosphate contained in the coating layer, the inorganic particles having an arithmetic average particle diameter of 0.5 to 10 μm, and the inorganic binder is 100 parts by mass in terms of solid content. Furthermore, the heat insulating material according to the above (1), which further contains 0.5 to 10 parts by mass of reinforcing fibers,
(3) The heat insulating material according to (1) or (2), wherein the inorganic particles having an arithmetic average particle diameter of 0.5 to 10 μm constituting the coating layer are alumina particles or silica particles,
(4) The heat insulating material according to any one of (1) to (3), wherein the penetration portion has an average depth of 10 to 1000 μm.
(5) On the heat-insulating molded product comprising nanoparticles,
In terms of solid content, the total amount of aluminum phosphate is 5 to 50% by mass, the total amount of inorganic particles having an arithmetic average particle size of 0.5 to 10 μm is 40 to 90% by mass, and the total amount of inorganic binder is 0 to 10% by mass. A method for producing a heat insulating material, characterized by applying a coating layer-forming dispersion liquid,
(6) The method for producing a heat insulating material according to (5), wherein the inorganic binder is colloidal silica having a pH of 1 to 5.

  According to the present invention, the aluminum phosphate forms a crack (crack) on the surface of the heat insulating formed body at the interface between the heat insulating formed body and the coating layer, and the formation component of the coating layer penetrates into the crack. Can be firmly fixed, so that the detachment of fine particles constituting the heat-insulating molded body that is the base material is suppressed, and the occurrence of cracks on the outer surface is suppressed to improve the smoothness. In addition, it is possible to provide a heat insulating material that is not easily affected by the restriction, and a method for easily manufacturing the heat insulating material.

It is a figure which shows sectional drawing of the heat insulating material of this invention. It is a figure which shows the crack (crack) formed on the heat insulation molded object which comprises the heat insulating material of this invention.

First, the heat insulating material of the present invention will be described.
The heat insulating material of the present invention is an inorganic particle 40 having an aluminum phosphate content of 5 to 50% by mass and an arithmetic average particle size of 0.5 to 10 μm in terms of solid content on a heat insulating molded body comprising nanoparticles. A coating layer containing ~ 90% by mass and 0-10% by mass of an inorganic binder is formed, and the coating layer is a component that constitutes the coating layer at the interface with the heat insulating molded body. It has a penetration part that penetrates into the molded body.

  In the heat insulating material of the present invention, as the heat insulating molded body containing nanoparticles, a nanoparticle-containing compression molded body, or a fibrous body filled with airgel fused with nanoparticles (hereinafter referred to as an airgel fibrous body as appropriate). ).

The nanoparticle-containing compression-molded body is a heat insulating structure formed by compression-molding nanoparticles.
The nanoparticles constituting the nanoparticle-containing compression-molded body preferably have an average primary particle size in the range of 3 to 1000 nm, more preferably in the range of 3 to 100 nm, and further in the range of 3 to 50 nm. preferable.

In the present application documents, the average diameter of the primary particles is the case where the true density (g / m ³ ) of the nanoparticles is “a” and the BET specific surface area (m ² / g) of the nanoparticles is “S”. Furthermore, it means the converted particle diameter D (m) calculated by the formula “D = 6 / (a × S)”. For example, since the true density of silica is 2.2 × 10 ⁶ g / m ³ , the average diameter (converted particle diameter) of silica nanoparticles having a specific surface area of 300 m ² / g is calculated to be about 9 nm.

Primary particles having an average diameter of 1 μm or less can be aggregated to form secondary particles when compressed. For this reason, the nanoparticle-containing compression-molded product includes secondary particles of the nanoparticles.
By using nanoparticles having a small average diameter of primary particles, the size of voids formed in the secondary particles can be reduced. Further, by reducing the size of these voids, the air in the compression molded body can be reduced. Convection can be effectively suppressed. For this reason, for example, a nanoparticle compression-molded body having an average primary particle diameter of less than 10 nm can exhibit excellent heat insulation.

  In the heat insulating material of the present invention, examples of the nanoparticles constituting the nanoparticle-containing compression-molded body include nanoparticles composed of inorganic materials (inorganic nanoparticles) or nanoparticles composed of organic materials (organic nanoparticles). Among these nanoparticles, inorganic nanoparticles can be preferably used because they can effectively enhance the heat resistance of the compression molded body.

As an inorganic nanoparticle, the inorganic nanoparticle which consists of metal oxides, such as a silica, an alumina, aluminum silicate, a titanium oxide, can be mentioned, for example.
Among these inorganic nanoparticles, nanoparticles made of silica (silica nanoparticles) can effectively enhance the heat insulating properties of the heat insulating molded body.

As silica nanoparticles, dry silica (so-called fumed silica) produced by a gas phase method or wet silica produced by a liquid phase method can be preferably used.
As dry silica, hydrophilic fumed silica having abundant hydrophilic groups such as silanol groups on its surface, or hydrophobic fumed silica produced by subjecting the surface of the hydrophilic fumed silica to hydrophobic treatment Can be used. Hydrophobic fumed silica compression-molded bodies are less susceptible to thermal insulation degradation due to moisture absorption than hydrophilic fumed silica compression-molded bodies.

  The nanoparticle-containing compression-molded body preferably contains 50 to 100% by mass of nanoparticles, more preferably 50 to 99% by mass, further preferably 70 to 99% by mass, and more preferably 80 to 99% by mass. % Content is particularly preferable.

  Further, the nanoparticle-containing compression-molded body can further contain a fibrous substance in addition to the nanoparticles, and as the fibrous substance, a fiber made of an inorganic material (inorganic fiber) or a fiber made of an organic material ( Organic fiber).

  Examples of the inorganic fibers include glass fibers and ceramic fibers such as alumina fibers. Examples of organic fibers include aramid fibers, carbon fibers, and polyester fibers.

  The form of the fibrous substance contained in the nanoparticle-containing compression-molded body includes chopped fibers obtained by cutting long fibers (filaments) having a constant fiber diameter into a predetermined length, and fiber diameters and fiber lengths are not uniform. And short fiber (staple fiber) and porous fiber substrate.

Examples of chopped fibers include those having an average fiber diameter of 3 to 15 μm and an average length of 1 to 20 mm, preferably an average fiber diameter of 6 to 12 μm. The thing of the range of 3-9 mm can be mentioned.
As the average fiber diameter of the chopped fiber is smaller and the average length is longer, the flexibility of the nanoparticle-containing compression-molded body can be improved, and crack formation associated with deformation of the compression-molded body can be effectively suppressed. .
In addition, in this application document, the said average fiber diameter and average length mean each average value when the diameter and length of 300-500 chopped fibers used as a measurement sample are measured with an optical microscope.

Further, specific examples of staple fibers include short aramid fibers. Examples of the short aramid fibers include, for example, paraphenylene terephthalamide, which is a polycondensate of terephthalic acid dichloride and paraphenylene diamine, by a dry spinning method. The thing made into fiber can be mentioned.
The staple fiber preferably has a fiber diameter in the range of 0.1 to 12 μm. The staple fiber can be produced by, for example, a melt blow method.

  When the fibrous material is chopped fiber or staple fiber, the fibrous material can be suitably dispersed and irregularly oriented in the nanoparticle-containing compression-molded body.

In the nanoparticle-containing compression molded body, the content of the fibrous substance is preferably 0 to 20% by mass, more preferably 1 to 18% by mass, and further preferably 5 to 18% by mass. .
Since the thermal conductivity of the fibrous material is larger than the thermal conductivity of the nanoparticles or aggregates thereof, the content ratio of the fibrous material after taking into account the thermal conductivity of the nanoparticle-containing compression molded product to be used Is preferably determined.

The nanoparticle-containing compression-molded body may contain a radiation scattering material, and examples of the radiation scattering material include silicon carbide, zirconia, and titania.
The radiation scattering material preferably has an average particle size of 50 μm or less, more specifically 1 to 50 μm, and a relative refractive index with respect to light having a wavelength of 1 μm or more is suitably 1.25 or more. is there.

In the nanoparticle-containing compression-molded body, the content ratio of the radiation scattering material is not particularly limited, but is preferably, for example, 0 to 40% by mass, more preferably 5 to 40% by mass, and 15 to 30% by mass. % Is more preferable.
By adding such a radiation scattering material, the thermal conductivity at a high temperature such as 800 ° C. or higher can be reduced.

  The nanoparticle-containing compression-molded body can also contain a binder (binder) regardless of whether or not it contains a fibrous substance. Examples of the binder include organic binders such as fluororesin, polyimide resin, and PET resin, and inorganic binders such as glass frit.

  When the amount of the binder in the nanoparticle-containing compression-molded body increases, the heat insulating property of the compression-molded body tends to decrease. Therefore, the binder content is preferably reduced as much as possible. The content of is preferably 3% by mass or less, more preferably 1% by mass or less, and still more preferably substantially no binder (0.1% by mass or less).

In the heat insulating material of the present invention, BET specific surface area of the nanoparticles containing the compression molded article, preferably has a 15~500m ² / g, more preferably those which are ^{20~500m 2 / g, 20~450m 2 /} g Is more preferred.
The BET specific surface area can be adjusted by appropriately adjusting the average particle diameter of the nanoparticles constituting the compression molded body and the compression conditions described later during the production of compression molding.

  The nanoparticle-containing compression-molded body contains nanoparticles and has a BET specific surface area in the above range, thereby suppressing thermal conduction by convection and maintaining low thermal conductivity of inorganic fine particles, thereby reducing thermal conductivity. It becomes easy.

The nanoparticle-containing compression-molded body can be produced by compressing a nanoparticle powder into a predetermined shape.
That is, for example, a nano-sized powder is spread in a mold having a predetermined shape, and the powder is then compressed in the mold to obtain a compression-molded body having the predetermined shape. In addition, for example, by continuously supplying nanoparticle powder to a compression molding apparatus equipped with a roller and compressing the powder with the roller, a belt-like compression molded body extending continuously for a long time can be obtained.

Moreover, when manufacturing the compression molding body containing a fibrous substance, the powder of a nanoparticle etc. and the said fibrous substance are integrally compression-molded.
That is, for example, a nanoparticle and a fibrous substance (for example, chopped fiber or staple fiber) are mixed at a predetermined weight ratio to prepare a mixed powder in which the fiber is dispersed in the nanoparticle powder. By compressing the mixed powder, a desired compression molded product can be obtained.

In the heat insulating material of the present invention, the bulk density of the nanoparticle-containing compacts is preferably 20~500kg / ^{m 3,} more preferably 100 to 300 / ^{m 3.}

  There are no particular restrictions on the compression conditions during the formation of the nanoparticle-containing compression-molded body, and it is preferable to adjust the pressing pressure and pressing time so that the bulk density of the resulting heat-insulating molded body is within the above range.

  In the heat insulating material of the present invention, examples of the airgel fiber body, which is a heat-insulating shaped body containing nanoparticles, include those in which the airgel is fixed in the pores of the porous fiber base material.

  As said porous fiber base material, the woven fabric or nonwoven fabric which consists of an inorganic fiber or organic fiber mentioned above can be mentioned. In particular, when a nonwoven fabric in which fibers are entangled irregularly is used as the porous fiber substrate, the airgel can be more effectively held between the fibers.

  Moreover, as a fiber which comprises a porous fiber base material, ceramic fibers, such as resin fibers, such as a polyethylene terephthalate (PET) fiber, carbon fiber, an alumina fiber, may be sufficient, for example.

  As the airgel, an airgel made of an inorganic material (inorganic airgel) or an airgel made of an organic material (organic airgel) can be used. By using the inorganic airgel, the heat resistance of the airgel fiber can be effectively increased.

The inorganic airgel is produced by hydrolysis and condensation using a metal alkoxide as a raw material, and appropriately contains materials such as silica, carbide and alumina. Specific examples include silica airgel, alumina airgel, titania airgel, zirconia airgel, and the like.
Moreover, polymer airgel, such as carbon airgel and a polyimide, can be mentioned as organic airgel.
Among these, silica airgel is preferable because it has many production examples and is easily available. A method for producing an airgel is described in, for example, JP-T-2004-517222.

  In addition, the content ratio of the airgel and the porous fiber base material contained in the airgel fiber body is appropriately determined according to the characteristics (for example, heat insulating property, flexibility, heat resistance, dust generation property) that the airgel fiber body should have. Can be set.

The airgel is a light-transmitting porous body having a uniform ultrafine structure formed by removing a mobile solvent phase between lattices from the pores of a gel structure having open cells.
Accordingly, the airgel has a low density and a cluster structure in which spherical nanoparticles are fused. Moreover, an airgel is an open cell structure which has a very small pore diameter with an average diameter of about 2 to 7 nm, for example, and has a large surface area.
Moreover, since airgel cannot convect over a grid | lattice-like structure, the heat transfer by a convection can be suppressed efficiently and a remarkable heat insulation is shown. The average size and density of the pores can be controlled during manufacture.

  The average diameter of the nanoparticles constituting the airgel is not particularly limited as long as it has the same average diameter as the primary particles of the nanoparticles constituting the nanoparticle-containing compression-molded body.

In the heat insulating material of the present invention, the bulk density of the airgel fibrous body, for example, be in the range of 20~500kg / ^{m 3,} preferably in the range of 100 to 300 / ^{m 3.}
In the heat insulating material of the present invention, the BET specific surface area of the airgel fiber body is not particularly limited, but may be the same as that of the nanoparticle-containing compression molded body.

  The airgel fiber body can be produced by supercritical drying of a fiber base material impregnated with an airgel raw material (metal alkoxide or the like). And the airgel which fills the space | gap between fibers can prevent effectively the convection of the air in an airgel fiber body by the micropore in the said airgel. For this reason, an airgel fiber body can have the outstanding heat insulation.

In the heat insulating material of the present invention, the heat conductivity at 25 ° C. of the heat-insulating molded body comprising nanoparticles is suitably, for example, 0.024 W / m · K or less, and 0.020 W / m · It is more suitable that it is K or less, and it is further suitable that it is 0.018 W / m · K or less.
In addition, the heat conductivity at 80 ° C. of the heat-insulating molded product comprising nanoparticles is suitably 0.035 W / m · K or less, more preferably 0.027 W / m · K or less. It is suitable, and it is further suitable that it is 0.025 W / m · K or less.

In the heat insulating material of this invention, when the heat insulating molded object containing a nanoparticle has the heat insulation which was excellent, it can reduce in thickness, maintaining sufficient heat insulation.
For example, when the heat-insulating molded body has a plate-like structure, the thickness can be, for example, in the range of 1 to 200 mm, preferably in the range of 5 to 150 mm, and more preferably 10 It can be in the range of ˜100 mm, more preferably in the range of 10 to 70 mm.

  In the heat insulating material of the present invention, on the heat insulating shaped body, in terms of solid content, 5 to 50% by mass of aluminum phosphate and 40 to 90% by mass of inorganic particles having an arithmetic average particle diameter of 0.5 to 10 μm. And the coating layer containing 0-10 mass% of inorganic binders is formed.

In the heat insulating material of the present invention, the content of aluminum phosphate constituting the coating layer is 5 to 50% by mass in terms of solid content, preferably 10 to 40% by mass, and 20 to 35% by mass. More preferably.
When the content of aluminum phosphate is within the above range, a crack (crack) is formed on the surface of the heat-insulating molded body, and the coating layer forming component penetrates into the crack to firmly fix the coating layer. Therefore, it is possible to easily provide a heat insulating material that is less susceptible to shape restrictions by suppressing the detachment of the fine particles constituting the heat insulating molded body that is the base material.

In the heat insulating material of the present invention, the content of the inorganic particles having an arithmetic average particle size of 0.5 to 10 μm constituting the coating layer is 40 to 90% by mass and 55 to 80% by mass in terms of solid content. It is preferable that it is 63 to 75% by mass.
When the content of the inorganic particles having an arithmetic average particle size of 0.5 to 10 μm is within the above range, the heat resistance and strength of the heat insulating material can be easily improved.

  In addition, in this application document, the arithmetic mean particle diameter of the inorganic particle which comprises a coating layer means the value measured using the laser diffraction type particle size distribution measuring apparatus. The arithmetic average particle diameter of such inorganic particles can be measured, for example, using a laser diffraction particle size distribution measuring device “SLDA-2200” manufactured by Shimadzu Corporation.

  In the heat insulating material of the present invention, the inorganic particles constituting the coating layer are not particularly limited, and examples thereof include alumina particles, silica particles, silicon carbide particles, and among these, alumina particles or silica particles are preferable.

  In the heat insulating material of the present invention, the content of the inorganic binder constituting the coating layer is 0 to 10% by mass, preferably 1 to 7% by mass, and 3 to 5% by mass in terms of solid content. It is more preferable.

  When the content of the inorganic binder is within the above range, it is easy to bind the constituent components of the coating layer while maintaining the heat resistance and strength of the heat insulating material, and the occurrence of cracks on the outer surface of the heat insulating material is suppressed and smoothed. It becomes easy to improve property.

Examples of the inorganic binder include one or more selected from colloidal silica, glass frit, alumina sol, silica sol, sodium silicate, titania sol, lithium silicate, water glass, and the like.
In this application document, the inorganic binder does not include aluminum phosphate.
As the inorganic binder, colloidal silica is preferable, and colloidal silica having a pH of 1 to 5 is more preferable. By using acidic colloidal silica having such a pH of 1 to 5, the reaction of acidic aluminum phosphate is suppressed. Therefore, in the coating layer forming dispersion described later, problems such as gelation are avoided, and appropriate fluidity is ensured. As a result, the coating layer forming dispersion can be suitably applied to the surface of the heat insulating material.

  In the heat insulating material of the present invention, the coating layer may further contain an organic binder, and the organic binder is not particularly limited. One or more selected from carboxymethyl cellulose ammonium salt, cellulose acetate, cellulose acetate butyrate (CAB), methyl cellulose (MC) and the like can be mentioned.

  In the heat insulating material of the present invention, when the coating layer contains an organic binder, the content ratio is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass in terms of solid content. 1 to 3% by mass is more preferable.

In the heat insulating material of the present invention, the coating layer preferably contains reinforcing fibers.
Examples of reinforcing fibers include wollastonite, sepiolite powder, attapulgite, and shotless ceramic fibers.

Wollastonite is an inorganic substance having a needle-like crystal structure having an infinite silicon-oxygen chain (SiO ₃ ) structure connected by calcium cations expressed by CaSiO ₃ (CaO · SiO ₂ ). is there. Wollastonite produced as a natural mineral is produced in the limestone area as wollastonite, and may contain trace amounts (for example, less than 0.5% by weight) of Al ₂ O ₃ and Fe ₂ O ₃ as impurities.

Sepiolite is a clay-like hydrous magnesium silicate mineral and has a compositional formula represented by Mg ₄ Si ₆ O ₁₅ (OH) ₂ .6H ₂ O, and has an inorganic crystal structure. Attapulgite is a clay-like hydrous aluminum silicate / magnesium compound, and is represented by a compositional formula represented by Si ₈ O ₂₀ Mg ₅ (OH) ₂ .Al (OH ₂ ) ₄ .4H ₂ O. The crystal structure is an inorganic substance having a needle shape.

  Further, the shotless ceramic fiber is prepared by adjusting the shot content of 45 μm or more to 5% or less (preferably 2% or less) by degreasing the shot (granular material) formed in the fiberizing process of the ceramic fiber. For example, “T-fiber TFA-05” manufactured by NICHIAS Corporation is marketed.

The reinforcing fiber preferably has an average fiber diameter of 1 to 80 μm, more preferably 1 to 60 μm, and still more preferably 2 to 60 μm. The reinforcing fiber preferably has an average length of 10 to 1000 μm, more preferably 10 to 800 μm, and still more preferably 20 to 800 μm.
In addition, the said average fiber diameter and average length mean each average value when the diameter and length of 300-500 reinforcement fibers used as a measurement sample are measured with an optical microscope.

  In the heat insulating material of the present invention, when the coating layer contains reinforcing fibers, the content ratio is preferably 1 to 20% by mass, more preferably 1 to 15% by mass in terms of solid content, More preferably, it is 2-15 mass%.

  In the heat insulating material of the present invention, the coating layer has an intrusion portion through which a component constituting the coating layer penetrates the heat insulating molded body at the interface with the heat insulating molded body.

  The penetration portion is formed by penetration of a component constituting the coating layer into a recess of a crack (crack) formed on the surface of the heat insulating molded body at the interface between the coating layer and the heat insulating molded body.

The average width of the opening of the penetration portion (average width of the crack opening) is suitably 5 to 1000 μm, more preferably 10 to 500 μm, and further preferably 20 to 300 μm. Is appropriate.
The average width of the opening of the penetration portion is such that an aluminum phosphate solution having a concentration corresponding to the concentration of aluminum phosphate constituting the coating layer is applied to the surface of the heat insulating molded body, dried, and heat insulating. It means an average value when the width of 10 cracks is measured with a scanning electron microscope (SEM) after causing cracks on the surface of the molded body.

Further, the average depth of the penetration portion (average depth of cracks) is suitably 10 to 1000 μm, more suitably 50 to 800 μm, and even more suitably 200 to 600 μm. It is.
A layered portion of the coating layer is formed on the outermost surface of the coating layer, and the average thickness (average depth) of the layered portion of the coating layer is suitably 10 to 1000 μm, and 25 to 500 μm. It is more suitable, and it is still more suitable that it is 50-200 micrometers.
The average depth of the penetration part and the average thickness of the layered part constituting the coating layer are determined by observing the cross section of the heat insulating material of the present invention with a scanning electron microscope (SEM), and the depth of each of the 10 penetration parts or the layered part. It means the average value when measuring the thickness.

  The heat insulating material of the present invention is a base material that allows the coating layer to penetrate into the surface of the heat-insulating molded body and firmly fix the coating layer because the coating layer has the penetration portion. It is possible to prevent the fine particles constituting the heat insulating molded body from being detached.

Heat insulating material of the present invention is preferably one bulk density is 20~500kg / ^{m 3,} more preferably those which are 100~400kg / ^{m 3,} more preferably those which are 100 to 300 / ^{m 3.}

The heat insulating material of the present invention preferably has a thermal conductivity at 25 ° C. of, for example, 0.024 W / m · K or less, more preferably 0.020 W / m · K or less, and What is 018 W / m * K or less is still more preferable.
Furthermore, the heat insulating material of the present invention preferably has a thermal conductivity at 80 ° C. of, for example, 0.035 W / m · K or less, more preferably 0.027 W / m · K or less, and 0 More preferably, it is not more than 0.025 W / m · K.
In the heat insulating material of this invention, desired heat resistance can be exhibited because the heat conductivity in 25 degreeC is 0.024 W / m * K or less.

  The heat insulating material of the present invention has, for example, a shrinkage ratio in the length direction when heated at 1100 ° C. for 24 hours in an air atmosphere ({(length before heating−length after heating) / length before heating). }) × 100) is suitably 5% or less, more suitably 3.0% or less, and even more suitably 1.0% or less.

The hardness of the heat insulating material of the present invention is not particularly limited, but is preferably 75 to 95, more preferably 80 to 90.
When the hardness of the heat insulating material of this invention exists in the said range, desired intensity | strength can be exhibited.

  In addition, in this application document, the hardness of a heat insulating material means the average value at the time of measuring 10 times using Asker rubber hardness meter Type C based on JISK7312.

According to the present invention, the aluminum phosphate forms a crack (crack) on the surface of the heat insulating formed body at the interface between the heat insulating formed body and the coating layer, and the formation component of the coating layer penetrates into the crack. Can be firmly fixed, so that the detachment of fine particles constituting the heat-insulating molded body that is the base material is suppressed, and the occurrence of cracks on the outer surface is suppressed to improve the smoothness. Thus, it is possible to provide a heat insulating material that is not easily affected by the restrictions.
The heat insulating material of the present invention can be produced by the method for manufacturing a heat insulating material of the present invention described in detail below.

Next, the manufacturing method of the heat insulating material of this invention is demonstrated.
In the method for producing a heat insulating material of the present invention, the total amount of aluminum phosphate is 5 to 50% by mass, and the arithmetic average particle size is 0.5 to 10 μm in terms of solid content on a heat-insulating shaped body comprising nanoparticles. The coating layer-forming dispersion is applied so that the total amount of inorganic particles is 40 to 90% by mass and the total amount of inorganic binder is 0 to 10% by mass.

  In the method for manufacturing a heat insulating material of the present invention, examples of the heat insulating molded body containing nanoparticles may include the same ones as described above.

In the manufacturing method of the heat insulating material of the present invention, the total amount of aluminum phosphate is 5 to 50% by mass, and the arithmetic average particle diameter is 0.5 to 0.5% in terms of solid content on the heat insulating formed body including nanoparticles. The dispersion for forming a coating layer is applied so that the total amount of inorganic particles of 10 μm is 40 to 90% by mass and the total amount of inorganic binder is 0 to 10% by mass.
Specific examples of the inorganic particles and the inorganic binder having an arithmetic average particle diameter of 0.5 to 10 μm are as described above.

In the method for manufacturing a heat insulating material of the present invention, the total amount of aluminum phosphate contained in the coating layer-forming dispersion is 5 to 50% by mass, preferably 10 to 40% by mass, in terms of solid content. More preferably, it is 20-35 mass%.
When the total amount of aluminum phosphate contained in the dispersion for forming the coating layer is within the above range, the surface of the heat insulating molded body is cracked (cracked), and the coating layer forming component penetrates into the crack and covers the surface. Since the layer can be firmly fixed, it is possible to easily produce a heat insulating material that is less susceptible to shape restrictions by suppressing the detachment of the fine particles constituting the heat insulating molded body that is the base material.

In the manufacturing method of the heat insulating material of the present invention, the content of the inorganic particles having an arithmetic average particle size of 0.5 to 10 μm contained in the coating layer forming dispersion is 40 to 90% by mass in terms of solid content. It is preferable that it is 55-80 mass%, and it is more preferable that it is 63-75 mass%.
When the total amount of inorganic particles having an arithmetic average particle size of 0.5 to 10 μm contained in the coating layer forming dispersion is within the above range, the heat resistance and strength of the obtained heat insulating material can be easily improved. it can.

In the method for producing a heat insulating material of the present invention, the total amount of the inorganic binder contained in the coating layer-forming dispersion is 0 to 10% by mass, preferably 1 to 7% by mass, in terms of solid content. More preferably, it is -5 mass%.
When the total amount of the inorganic binder contained in the dispersion for forming the coating layer is within the above range, it is easy to bind the constituent components of the coating layer while maintaining heat resistance and strength, and suppresses the occurrence of cracks on the outer surface. It becomes easy to produce the heat insulating material which improved smoothness.

In the heat insulating material manufacturing method of the present invention, the coating layer forming dispersion may further contain an organic binder. Specific examples of the organic binder are as described above.
When the coating layer forming dispersion contains an organic binder, the total amount of the organic binder contained in the coating layer forming dispersion is preferably 0.5 to 5% by mass in terms of solid content, and 1 to 4 It is more preferable that it is mass%, and it is still more preferable that it is 1-3 mass%.

In the heat insulating material manufacturing method of the present invention, the coating layer forming dispersion may further contain reinforcing fibers. Specific examples of the reinforcing fibers are as described above.
When the coating layer forming dispersion contains reinforcing fibers, the total amount of reinforcing fibers contained in the coating layer forming dispersion is preferably 1 to 20% by mass in terms of solid content, and 1 to 15% by mass. It is more preferable that it is 2-15 mass%.

  The solid content concentration in the dispersion for forming a coating layer is not particularly limited, but may be, for example, 0.1 to 75% by mass, more preferably 15 to 70% by mass, and further preferably 45 to 65% by mass. If the solid content concentration is less than 0.1% by mass, the amount of the solvent to be removed after coating becomes excessive, which is inefficient. If the solid content concentration exceeds 75% by mass, the solid content is uniform in each dispersion. Difficult to disperse.

  In the method for producing a heat insulating material of the present invention, the liquid medium constituting the dispersion for forming a coating layer is not particularly limited, and examples thereof include water and a polar organic solvent. Examples of the polar organic solvent include ethanol and propanol. And divalent alcohols such as ethylene glycol. Among these liquid media, water is preferable in consideration of the working environment and environmental load. Moreover, it does not restrict | limit especially as water, Distilled water, ion-exchange water, tap water, groundwater, industrial water etc. can be mentioned.

In the method for producing a heat insulating material of the present invention, the coating layer-forming dispersion is one as long as the total amount of aluminum phosphate, the inorganic particles having an arithmetic average particle size of 0.5 to 10 μm, and the inorganic binder is within the above range. It may be a liquid type or a two-part type.
For example, formation of a one-liquid coating layer in which aluminum phosphate, an inorganic particle having an arithmetic average particle diameter of 0.5 to 10 μm, and an inorganic binder are mixed in a liquid medium so that the total amount thereof is within the above range. A dispersion for forming a coating layer for pretreatment containing aluminum phosphate as an essential component, and aluminum phosphate A dispersion for forming a coating layer for post-treatment that does not contain as an essential component, and the total amount of each of aluminum phosphate, inorganic particles having an arithmetic average particle size of 0.5 to 10 μm, and inorganic binder in both dispersions You may apply | coat so that may become in the said range.

  In the method for producing a heat insulating material of the present invention, the number of coatings of the coating layer forming dispersion is not particularly limited. The one-liquid coating layer forming dispersion may be applied only once or a plurality of times so as to obtain a coating layer having a desired thickness. Further, the coating liquid for forming a coating layer for pretreatment may be applied a desired number of times, and then the dispersion for forming a coating layer for post-treatment may be applied for a desired number of times.

  As the above-mentioned coating method, for the heat-insulating molded product comprising nanoparticles, a coating layer forming dispersion, a method of brush coating, a method of coating by spray, a method of coating using a spin coater, The method of apply | coating by immersing in the processing tank filled with the dispersion liquid for coating layer formation can be mentioned.

  In the method for producing a heat insulating material of the present invention, a coating layer-forming dispersion is applied onto a heat-insulating molded body, and then the applied dispersion is dried. The drying is preferably natural drying, and may be forced drying with a dryer or the like as long as the object of the present invention is not adversely affected. In addition, examples of the atmosphere during drying include an air atmosphere, an oxygen atmosphere, and a nitrogen atmosphere.

  In the case of forced drying, the drying temperature is preferably 40 to 180 ° C, more preferably 60 to 150 ° C, and further preferably 80 to 120 ° C. The drying time is preferably 6 to 48 hours, more preferably 8 to 40 hours, and further preferably 10 to 36 hours.

Moreover, in the manufacturing method of the heat insulating material of this invention, after performing the said drying process, you may give a baking process further.
The firing temperature is preferably 600 to 1300 ° C, and more preferably 700 to 900 ° C. The atmosphere during firing is not particularly limited, but is preferably an air atmosphere, an oxygen atmosphere, or a nitrogen atmosphere. The firing time is preferably 0.5 to 4 hours.
By performing the baking treatment, the molded product can be prevented from degreasing and shrinkage during actual use.

According to the method for producing a heat insulating material of the present invention, aluminum phosphate causes a crack (crack) on the surface of the heat insulating formed body at the interface between the heat insulating formed body and the coating layer, and the component for forming the coating layer is formed in the crack. Since it can penetrate and firmly fix the coating layer, while suppressing the detachment of the fine particles constituting the heat-insulating molded body that is the base material, the occurrence of cracks on the outer surface is suppressed, and the smoothness is improved. The heat insulating material which is hard to receive restrictions on use temperature or a shape can be manufactured simply.
The details of the heat insulating material obtained by the method of the present invention are as described above.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by the following examples.

Example 1
(1) Preparation of heat insulating molded body
A mixture obtained by mixing 80% by mass of silica fine particle powder having an average primary particle size of 15 nm and 20% by mass of silicon carbide powder having an average particle size of 5 μm by dry press molding is used to form a flat heat insulating molded body (150 mm long, 100 mm wide and 25 mm thick). In dry press molding, the press pressure was adjusted so that the bulk density of the heat insulating molded body was 250 kg / m ³ .
This heat insulating molded body had a thermal conductivity of 0.01 W / m · K at 25 ° C.

(2) Preparation of coating layer-forming aqueous dispersion Aluminum phosphate aqueous dispersion having a solid content concentration of 30% by mass, alumina powder having an arithmetic average particle diameter of 5 μm, and acidic colloidal silica aqueous dispersion having a solid content concentration of 20% by mass A liquid (pH 3) is mixed, and in terms of solid content, it contains 21.4% by mass of aluminum phosphate, 71.4% by mass of alumina powder, and 7.1% by mass of colloidal silica. An aqueous dispersion for forming a coating layer was prepared.

(3) Formation of coating layer The aqueous dispersion for coating layer formation obtained in (2) above is sprayed on the entire surface of the heat insulating molded body obtained in (1) so as to have a desired coating layer thickness. Then, it was naturally dried at room temperature (25 ° C.) for 6 hours, and then dried at 105 ° C. for 6 hours to obtain a heat insulating material having a coating layer formed on the heat insulating molded body.

(Thermal conductivity)
When the heat conductivity of the said heat insulating material was measured by the periodic heating method, the heat conductivity in 25 degreeC was 0.01 W / mK.

(hardness)
It was 84.7 when the hardness of the said heat insulating material was computed by the average value when measured 10 times using the polymer meter Co., Ltd. product Asker rubber hardness meter Type C based on JISK7312.

(Powder)
The adhesion amount (mg) per 10 mm ² of the adhesive tape when an adhesive tape (Cellohone tape 596-921 manufactured by Askul) was applied to the surface of the heat insulating material and peeled off was measured and judged according to the following criteria. The results are shown in Table 1.
A: The amount of powder adhering to less than 0.032 mg / 10 mm ² ○: The amount of adhering powder of 0.032 to 0.043 mg / 10 mm ² Δ: The amount of adhering powder of 0.043 mg / 10 mm ² Exceeding 0.065 mg / 10 mm ² or less X: Powder adhering amount exceeding 0.065 mg / 10 mm ²

(Ease of painting)
The ease of application of the aqueous dispersion for forming a coating layer during the formation of the coating layer in (3) above was judged according to the following criteria. The results are shown in Table 1.
◎: Can be applied by spraying ○: Cannot be applied by spray but can be applied easily by brush △: Can be applied by brush but not easy

When a vertical cross-section with respect to the main surface of the heat insulating material was observed with a scanning electron micrograph, as shown in FIG. 1, the component constituting the coating layer was a heat insulating molded body at the interface between the coating layer and the heat insulating molded body. A penetration part b penetrating into the film was observed, and a layered part a of the coating layer was observed on the upper part. The average thickness (average depth) of the layered portion a of the coating layer was 120 μm, and the average depth of the penetration portion b was 350 μm.
In addition, when an aqueous dispersion containing the same amount of aluminum phosphate as the amount contained in the aqueous dispersion for forming a coating layer was prepared on the surface of the heat-insulating molded body, applied, and then naturally dried, FIG. As shown, a crack (crack) was formed on the heat insulating molded body, and it was confirmed that this crack formed an intrusion portion. When the opening width in the opening of the penetration portion was measured, the average width in the opening was 50 μm.

(Example 2 to Example 28)
In Example 1 (2), using a dispersion that was changed so that the composition (solid content concentration) of the aqueous dispersion for forming a coating layer was as shown in Tables 1 to 7, and using the same dispersion as in Example 1, (In Tables 1 to 7, the amount of each component used in preparing the aqueous dispersion for forming a coating layer is described in parts by mass, and the solid content equivalent amount of each component is described in mass%).
In Example 3 to Example 5, Example 14 to Example 18, and Example 24 to Example 27, wollastonite (NYAD-G manufactured by NYCO) was used as the reinforcing fiber, and Example 19 and Example 20 were used. Carboxymethylcellulose (CMC) was used as the organic binder, and in Examples 22 and 23, an aqueous alkaline colloidal silica dispersion (pH 10) having a solid content concentration of 20 mass% was further used as the inorganic binder.
In Examples 24 to 27, the coating amount of the coating layer-forming aqueous dispersion is set to about 1/4 of the coating amount in Example 1, and three times, four times, six times, By applying eight times, the total amount of coating was adjusted to the amount shown in Table 7.
In each obtained heat insulating material, it carried out similarly to Example 1, and measured thermal conductivity, hardness, powderiness, and the ease of application. The results are shown in Tables 1-7.

  Moreover, in each obtained heat insulating material, when cross-sectional observation was carried out similarly to Example 1, the penetration part into which the component which comprises a coating layer penetrates into a heat insulating molded object in the interface of a coating layer and a heat insulating molded object. The average depth (average thickness) in the layered portion of the coating layer is 10 to 1000 μm, the average depth in the penetration portion of the coating layer is 10 to 1000 μm, and the average width in the opening portion of the penetration portion is 5 to 1000 μm. Was in range.

(Comparative Examples 1 to 4)
In Example 1 (2), the composition of the coating layer forming aqueous dispersion was changed as shown in Table 8, and a comparative heat insulating material was produced in the same manner as in Example 1 except that this dispersion was used ( In Table 8, the content ratio of each component in the aqueous dispersion for forming a coating layer is described in parts by mass, and is also described in mass% in which each component is converted into solid content).
In Comparative Example 1, an aqueous sodium carbonate solution having a solid concentration of 20% was used.
In each of the obtained comparative heat insulating materials, the thermal conductivity, hardness, powderiness, and ease of application were measured in the same manner as in Example 1. The results are shown in Table 8.
(Comparative Example 5)
The heat insulating formed body used in Example 1 was used as a comparative heat insulating material as it was without applying the coating layer forming dispersion.
In the obtained comparative heat insulating material, the thermal conductivity, hardness, and powderiness were measured in the same manner as in Example 1. The results are shown in Table 8.

  From the results of Tables 1 to 7, the heat insulating materials obtained in Examples 1 to 27 are 5 to 50% by mass of aluminum phosphate and arithmetic average particles on the heat insulating shaped body containing nanoparticles. A coating layer containing 40 to 90% by mass of inorganic particles having a diameter of 0.5 to 10 μm and 0 to 10% by mass of an inorganic binder is formed, and the coating layer is formed at the interface with the heat insulating molded body. Since the component constituting the coating layer has a penetration portion that penetrates into the heat insulating molded body, a crack (crack) is formed at the interface between the heat insulating molded body and the coating layer. Since the formation component of the coating layer penetrates into the substrate and the coating layer can be firmly fixed, the detachment of fine particles constituting the heat insulating molded body as the base material is suppressed, and the occurrence of cracks on the outer surface is suppressed. To improve smoothness and limit operating temperature and shape It can be seen only those hard.

  Further, from the results of Table 8, the heat insulating materials obtained in Comparative Examples 1 to 5 are those in which the coating layer-forming dispersion does not contain aluminum phosphate (Comparative Example 1 and Comparative Example 2) or inorganic powder. And the content of the inorganic binder is too high or too low (Comparative Example 3 and Comparative Example 4) or the coating layer itself does not exist (Comparative Example 5). It can be seen that the porosity is not improved.

  According to the present invention, the inorganic fine particles are prevented from being detached from the heat insulating molded body as a base material, and have a highly smooth surface that suppresses the occurrence of cracks on the outer surface. It is possible to provide a heat insulating material that is not easily affected by the above-described restrictions and a method for manufacturing the heat insulating material.

Claims (6)

On the heat insulating molded body comprising nanoparticles,
A coating layer containing 5 to 50% by mass of aluminum phosphate, 40 to 90% by mass of inorganic particles having an arithmetic average particle size of 0.5 to 10 μm, and 0 to 10% by mass of an inorganic binder is formed in terms of solid content. Being
The said coating layer has a penetration part into which the component which comprises the said coating layer penetrates into the said heat insulating molded object in the interface with the said heat insulating molded object, The heat insulating material characterized by the above-mentioned.   When the total content of the aluminum phosphate contained in the coating layer, the inorganic particles having an arithmetic average particle size of 0.5 to 10 μm, and the inorganic binder in terms of solid content is 100 parts by mass, further reinforcement The heat insulating material according to claim 1, comprising 0.5 to 10 parts by mass of a fiber.   The heat insulating material according to claim 1 or 2, wherein the inorganic particles having an arithmetic average particle diameter of 0.5 to 10 µm constituting the coating layer are alumina particles or silica particles.   4. The heat insulating material according to claim 1, wherein the penetration portion has an average depth of 10 to 1000 μm. On the heat insulating molded body comprising nanoparticles,
In terms of solid content, the total amount of aluminum phosphate is 5 to 50% by mass, the total amount of inorganic particles having an arithmetic average particle size of 0.5 to 10 μm is 40 to 90% by mass, and the total amount of inorganic binder is 0 to 10% by mass. A method for producing a heat insulating material, characterized by applying a coating layer-forming dispersion.   The method for producing a heat insulating material according to claim 5, wherein the inorganic binder is colloidal silica having a pH of 1 to 5.