CA6 particles and method for producing an inorganic fiber molded body using the same

Abstract

The CA6 particles according to the prevent invention are CA6 particles for use in forming molded inorganic-fiber objects and include a crystalline phase comprising CaO·6Al2O3. When the CA6 particles are sieved with a sieve having an opening size of 1 mm, the amount of particles remaining on the sieve is 0 wt%. When examined by a laser diffraction / scattering method, the CA6 particles give a volume-frequency particle size distribution in which, when the 50%-cumulative particle diameter is expressed by D50, then D50 is 10.0-40.0 μm.

Description

Technical Field

[0001] The present invention relates to CA6 particles and a method for manufacturing an inorganic fiber molded body using the same.

Background Art

[0002] Various developments have been made so far in powder materials containing CaO·6Al2O3. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a heat-insulating castable refractory in which a porous heat-insulating aggregate (CA6 aggregate) mainly composed of CaO·6Al2O3 is blended in a proportion of 65% by mass or more based on 100% by mass of the coarse grain region having a particle size of 1 mm or more (Claim 1 of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1 above, sufficient consideration has not been given to manufacturing an inorganic fiber molded body by a papermaking method using CA6 aggregates having a particle size of 1 mm or more. As a result of investigations by the present inventor, it has been found that there is room for improvement in terms of the manufacturing stability of an inorganic fiber molded body in the CA6 aggregates having a particle size of 1 mm or more described in Patent Document 1.

Means for Solving the Problems

[0005] As a result of further investigations by the present inventor, it has been found that the manufacturing stability of an inorganic fiber molded body can be improved by appropriately controlling the particle size distribution of fine CA6 particles composed of the fraction passing through a sieve having an opening of 1 mm. As a result of further studies based on such findings, using the average particle diameter (D50) of fine CA6 particles containing CaO·6Al2O3 in the crystal phase as an index and controlling this index within an appropriate range, it was found that clogging and peeling can be suppressed during the manufacturing process of the inorganic fiber molded body by the papermaking method, and thus the manufacturing stability of the inorganic fiber molded body can be improved, leading to the completion of the present invention.

[0006] According to one aspect of the present invention, the following CA6 particles and a method for manufacturing an inorganic fiber molded body using the same are provided.

[0007] 1. CA6 particles used for forming an inorganic fiber molded body, containing CaO·6Al2O3 in the crystal phase, when the CA6 particles are sieved using a sieve with an aperture of 1 mm, the remaining amount remaining on the sieve is 0% by weight, when the particle diameter at which the cumulative value in the volume frequency particle size distribution of the CA6 particles measured by the laser diffraction scattering method is 50% is defined as D50, D50 is 10.0 μm or more and 40.0 μm or less, CA6 particles. 2. The CA6 particles according to 1., when the particle diameter at which the cumulative value in the volume frequency particle size distribution is 10% is defined as D10, (D50 - D10) is 6.0 μm or more and 30 μm or less, CA6 particles. 3. The CA6 particles according to 1. or 2., when the particle diameter at which the cumulative value in the volume frequency particle size distribution is 90% is defined as D90, D90 is 350 μm or less, CA6 particles. 4. The CA6 particles according to any one of 1. to 3., with a bulk density of 0.6 g / cm 3 or more and 0.9 g / cm 3 or less, CA6 particles. 5. The CA6 particles according to any one of 1. to 4., wherein the boron content contained in the CA6 particles is 0.002% by mass or more and 0.05% by mass or less, CA6 particles. 6. A step of preparing a water slurry containing the CA6 particles according to any one of 1. to 5. and an inorganic fiber filler; A step of obtaining an inorganic fiber molded body by removing water in the water slurry, and A method for manufacturing an inorganic fiber molded body. 7. The method for manufacturing an inorganic fiber molded body according to 6., wherein During the preparation step, the water slurry contains an inorganic binder and / or an organic binder. A method for manufacturing an inorganic fiber molded body. 8. The method for manufacturing an inorganic fiber molded body according to 6. or 7., wherein During the preparation step, the inorganic fiber filler contains alumina fiber. A method for manufacturing an inorganic fiber molded body.

Advantages of the Invention

[0008] According to the present invention, CA6 particles excellent in the manufacturing stability of an inorganic fiber molded body and a method for manufacturing an inorganic fiber molded body using the same are provided.

Embodiments for Carrying Out the Invention

[0009] The CA6 particles of the present embodiment will be described.

[0010] The CA6 particles of the present embodiment contain CaO·6Al2O3 in the crystal phase and are used to form an inorganic fiber molded body. When the CA6 particles are sieved using a sieve with an opening of 1 mm, the remaining amount remaining on the sieve is 0% by weight, and when the particle diameter at which the cumulative value becomes 50% in the volume frequency particle size distribution measured by the laser diffraction scattering method is defined as D50, D50 is configured to be 10.0 μm or more and 40.0 μm or less.

[0011] The inorganic fiber molded body may be composed of a hand-formed body. The hand-formed body can be formed using various hand-forming methods. Examples of the hand-forming method include a vacuum forming method (suction forming method) and a compression forming method. The vacuum forming method is a method of manufacturing a formed body by, for example, sucking and dehydrating a raw material slurry containing raw material components with a papermaking machine such as a suction pump to obtain a formed body on a mesh (net), and heating this. In this manufacturing process, a plurality of combinations of the shape of the mesh, the number of suction times, the raw material slurry, etc. can be made. Therefore, the degree of freedom in shape design of the formed body can be increased by the suction forming method. The compression forming method is a method of manufacturing a formed body by, for example, compressing the formed body obtained by the vacuum forming method with a roll or the like. The inorganic fiber formed body obtained by the compression forming method has a higher bulk density than that obtained by the suction forming method.

[0012] In the volume frequency particle size distribution of CA6 particles measured by the laser diffraction scattering method, the particle diameter at which the cumulative value from the small particle size side becomes 10% is defined as D10, the particle diameter at which the cumulative value becomes 50% is defined as D50, and the particle diameter at which the cumulative value becomes 90% is defined as D90.

[0013] The lower limit of D50 in CA6 particles is, for example, 10.0 μm or more, preferably 13 μm or more, more preferably 15 μm or more. As a result, clogging during papermaking is less likely to occur, a fiber formed body with a homogeneous structure can be obtained, and the manufacturing amount can be improved by shortening the papermaking time. The upper limit of D50 in CA6 particles is, for example, 40.0 μm or less, preferably 35 μm or less, more preferably 30 μm or less. Thereby, the adhesion between the inorganic porous filler and the inorganic fiber filler via the organic binder and the inorganic binder, or the adhesion between the inorganic porous fillers can be made good. Therefore, it becomes difficult to separate from the fibers and fillers, and separation of the raw materials during slurry production can be suppressed. Also, when the organic binder burns out and the adhesive force is lost when used at high temperature, it is possible to suppress the inorganic porous filler from being easily peeled off.

[0014] The lower limit of (D50 - D10) is, for example, 6.0 μm or more, preferably 8.0 μm or more, more preferably 10.0 μm or more. As a result, the space between the fibers is easily filled with CA6 particles, and the heat insulation property can be improved. The upper limit of (D50 - D10) is, for example, 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less. Thereby, appropriate voids are formed in the inorganic fiber molded body, and the light weight can be improved.

[0015] The upper limit of D90 is, for example, 350 μm or less, preferably 200 μm or less, more preferably 160 μm or less. Thereby, sedimentation separation of CA6 particles in the raw material slurry and peeling of CA6 particles from the inorganic fiber molded body can be prevented. The lower limit of D90 is, for example, more than 40 μm, preferably 43 μm or more, more preferably 45 μm or more. Thereby, the strength of the inorganic fiber molded body can be improved.

[0016] The upper limit of the bulk density of CA6 particles is, for example, 0.9 g / cm 3 or less, preferably 0.89 g / cm 3 or less, more preferably 0.81 g / cm 3 or less. Thereby, the heat insulation property of the inorganic fiber molded body can be enhanced. The lower limit of the bulk density of CA6 particles is, for example, 0.6 g / cm 3 or more, preferably 0.61 g / cm 3 or more, more preferably 0.62 g / cm 3 or more. Thereby, the strength of the inorganic fiber molded body can be enhanced.

[0017] In the present embodiment, for example, by appropriately selecting the types and blending amounts of the respective components contained in the CA6 particles, the production method of the CA6 particles, etc., it is possible to control the above particle size distribution (D10, D50, D90) and bulk density. Among these, for example, mixing a boron compound as a sintering aid, performing a pulverization treatment using a roller mill, appropriately controlling the rotation speed of the roller mill, etc. can be cited as factors for making the above particle size distribution (D10, D50, D90) and bulk density within a desired numerical range.

[0018] The upper limit of the boron content contained in CA6 particles is, for example, 0.05% by mass or less, preferably 0.04% by mass or less. Thereby, particles with a porous structure excellent in heat insulation can be obtained. The lower limit of the boron content is, for example, 0.002% by mass or more, preferably 0.003% by mass or more. Thereby, the particle strength can be improved.

[0019] CA6 particles are composed of calcium aluminate porous particles containing CaO·6Al2O3 in the crystal phase.

[0020] CA6 particles may, if necessary, contain other crystal phases. Examples of other crystal phases include 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, etc. These may be used alone or in combination of two or more.

[0021] Hereinafter, a method for manufacturing CA6 particles will be described. The above CA6 particles can be obtained, for example, by mixing or mixing and grinding raw materials such as a calcia raw material, an alumina raw material, and, if necessary, a boron compound, and finally formulating them so that the molar ratio of CaO to Al2O3 of the synthesized calcium aluminate is approximately 1:6, kneading with water, molding, firing at a temperature of 1000°C to 1700°C, and then grinding with a grinder.

[0022] As the calcia raw material, it is possible to use powdered limestone, quicklime, or CaO·Al2O3 (CA), CaO·2Al2O3 (CA2), 12CaO·7Al2O3 (C12A7), 3CaO·Al2O3 (C3A), etc., and a plurality of these raw materials may be used in combination.

[0023] As alumina raw materials, aluminum oxide (Al2O3), transitional alumina, gibbsite (Al(OH)3), boehmite (AlO(OH)), etc. can be used, and a plurality of these raw materials can be combined and used. However, it is known that it is advantageous to use gibbsite or boehmite, which are hydrates of aluminum, to synthesize CA6 particles of the porous body. By using gibbsite as the alumina raw material, it is easy to obtain a porous structure in which primary crystals of flaky CA6 are aggregated, which is preferable.

[0024] In order to increase the amount of pores inherent in CA6 particles, a pore former can be added to the raw materials. For example, by adding a combustible substance as a pore former to the raw materials, the pore former burns and vaporizes during firing, voids are formed in the synthesized CA6 particles, and CA6 particles with many pores are formed. As the pore former, starch (corn starch), polyvinyl alcohol, methyl cellulose, acrylic resin, latex, etc. can be used. Among them, when using starch (corn starch), it is possible to form voids with a size of several tens of μm at a relatively low cost.

[0025] However, the voids formed by the pore former are larger than the gaps of about several μm generated between the crystals of CA6, which becomes a defect and a factor for reducing the strength of the particles. When using corn starch as the pore former, its addition amount is preferably less than 20% by mass in the total raw materials.

[0026] By adding a boron compound to the raw materials, it acts as a flux during firing, promotes the mass diffusion of various raw materials through the formed liquid phase, suppresses the residue of unreacted raw materials, and also strengthens the bond between the primary crystals of flaky CA6, resulting in an effect of increasing the strength of the CA6 particles.

[0027] As the boron compound, boric acid (H3BO3), sodium tetraborate anhydrous (Na2B4O7), sodium tetraborate decahydrate (Na2B4O7·10H2O), etc. can be used.

[0028] The method of mixing the raw materials is not particularly limited. Each material can be blended in a predetermined ratio and uniformly mixed using a mixer such as a V-type blender, a cone blender, a Nauta mixer, a pan-type mixer, and an omnimixer. Further, mixing and pulverization may be performed using a pulverizer such as a ball mill or a vibration mill. The mixing time is not particularly limited. Although there is an optimum value depending on the mixer, it is preferably 5 minutes or more, more preferably 15 minutes or more. There is no specified upper limit for the mixing time.

[0029] The raw materials are mixed with water, formed, and then charged into a firing furnace and fired at about 1000°C to 1700°C to obtain a fired product. As the firing method, it is possible to use equipment such as an electric furnace, a shuttle kiln, and a rotary kiln.

[0030] By subjecting the above-mentioned fired product to pulverization and classification treatment, CA6 particles can be obtained. The crusher is not limited, but a jaw crusher, an impact crusher, a roll crusher, a cone crusher, a hammer mill, etc. can be used. The pulverizer is not limited, but a roller mill, a ball mill, a vibration mill, a tower mill, a jet mill, etc. can be used. The classifier can obtain particles of a predetermined particle size by adjusting the sieve size using a sieving device such as a gyro shifter, a trommel, or a vibrating sieve.

[0031] The above-mentioned inorganic fiber formed body is composed of a formed body obtained by papermaking and forming a slurry containing raw material components such as CA6 particles of the present embodiment.

[0032] The method for manufacturing an inorganic fiber formed body includes, for example, a step of preparing an aqueous slurry containing CA6 particles and an inorganic fiber filler of the present embodiment (slurry step), and a step of removing water in the aqueous slurry to obtain an inorganic fiber formed body (papermaking step).

[0033] The slurry process adjusts a water slurry by dissolving or dispersing fiber raw materials such as inorganic fiber fillers, inorganic porous fillers, inorganic binders, and organic binders in water. The water slurry may include additives generally used in papermaking methods such as flocculants, if necessary.

[0034] Subsequently, in the papermaking process, the obtained slurry is passed through a mesh to dehydrate the water in the slurry, leaving the fiber raw materials on the mesh to obtain a papermaking body. Suction may be applied from below the mesh. Drying may be performed after or during dehydration. Also, the surface shape of the mesh is appropriately selected and may be planar or may have a three-dimensional structure in part.

[0035] As an example of papermaking, there are methods such as flowing the water slurry into a box-shaped container equipped with a wire mesh on the bottom surface, dehydrating while applying suction below the mesh, and drying the cake on the mesh surface; submerging a flat mesh equipped with a suction mechanism in the water slurry, suctioning and lifting the filtered cake, and drying it; and methods using continuous papermaking equipment such as a round wire papermaking machine or a long wire papermaking machine. Drying of the cake may be performed by hot air drying.

[0036] Thereafter, by heat-treating the obtained formed body, a papermaking formed body with a predetermined shape is manufactured. For example, heat and pressure treatment may be performed by pressing. The papermaking formed body may be processed into a board.

[0037] The thickness of the inorganic fiber formed body composed of the papermaking formed body is not particularly limited, but may be 1 mm to 100 mm, preferably 10 mm to 60 mm. Thereby, an inorganic fiber formed body with excellent handleability can be realized.

[0038] The inorganic fiber formed body contains an inorganic porous filler. The inorganic porous filler contains CA6 particles composed of calcium aluminate porous particles containing CaO·6Al2O3 in the crystal phase.

[0039] From the perspective of thermal conductivity, the inorganic fiber formed body preferably contains alumina fiber as the inorganic fiber filler.

[0040] Examples of other inorganic fiber fillers include oxide fibers such as titania and silica, alkali earth silicate wool (AES), refractory ceramic fiber (RCF), etc. These may be used alone or in combination of two or more.

[0041] The inorganic fiber molded body may contain a binder selected from at least one of an inorganic binder or an organic binder. By using the inorganic binder remaining in the inorganic fiber molded body after firing, peeling and spalling of the inorganic fiber filler and the inorganic porous filler can be suppressed, and the heat shrinkage rate of the inorganic fiber molded body can be reduced. The organic binder can bind inorganic fillers such as inorganic fiber fillers and inorganic porous fillers to each other during the manufacturing process of the inorganic fiber molded body, for example, in the sheet formed body described later.

[0042] The inorganic binder may contain one or more selected from the group consisting of colloidal silica, alumina sol, and water-curable alumina.

[0043] The organic binder may contain, for example, one or more selected from the group consisting of polyvinyl alcohol, polyethylene oxide, polyethylene glycol, starch, (meth)acrylate copolymer, and polyoxyethylene alkyl ether. In addition, adhesives such as epoxy-based, phenol-based, acrylate-based, polyurethane-based, isocyanate-based, polyimide-based, vinyl acetate-based, etc., and various rubber-based adhesives may be used as the organic binder.

[0044] Examples of the (meth)acrylate copolymer include copolymers of (meth)acrylate esters, copolymers of (meth)acrylate esters and monomers other than (meth)acrylate esters, etc.

[0045] The inorganic fiber molded body is not particularly limited and can be applied as long as it is a member that requires heat resistance. For example, it can be suitably used to constitute at least a part of a member used in a high-temperature environment such as a firing furnace.

[0046] Examples of the firing furnace include industrial furnaces such as iron-making furnaces, non-iron-making furnaces, ceramic industry furnaces, and chemical industry furnaces. Among these, it may be used for a firing furnace (heating furnace) that requires heat resistance of 1400 °C or higher. In addition, the inorganic fiber molded body may be used as a high-temperature refractory heat insulation material in a wide range of fields such as steel, metals, ceramics, and automobiles.

[0047] In this specification, "~" represents including the upper limit value and the lower limit value unless otherwise specified. In this specification, the term "paper-making body" is generally used as a technical term indicating the state of an object obtained by using a method of draining a fiber material.

[0048] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the range that can achieve the object of the present invention are included in the present invention.

Examples

[0049] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the descriptions of these examples at all.

[0050] <Preparation of CA6 Particles> (Comparative Example 1) As a calcium raw material, 8.4% by mass of calcium carbonate (Funemine limestone produced by Funemine Mine), as an alumina raw material, 76.7% by mass of aluminum hydroxide (C301N produced by Sumitomo Chemical), as a pore-forming material, 15.0% by mass of corn starch (Y-3P produced by Nippon Corn Starch), and as a sintering aid, 0.5% by mass of boric acid (Kanto Chemical special grade reagent) were weighed and mixed using a Nautamixer.

[0051] The mixed raw materials were granulated and formed into granules with a diameter of about 20 mm while adding water using a pan granulator, placed in a container made of alumina, and fired in an electric furnace (atmospheric atmosphere) at a maximum temperature of 1500 °C for 1 hour. After that, the fired product obtained by air cooling was crushed with a hammer mill, sieved using a sieve with an opening of 1 mm, and only the fraction passing through the sieve was collected to obtain CA6 particles A.

[0052] (Examples 1 - 8) The crushed product obtained by crushing the fired product obtained above with a hammer mill was pulverized using a roller mill. In each of the examples, except that the rotation speed of the roller mill and the amount of corn starch blended were changed, CA6 particles B to CA6 particles I were obtained in the same manner as the above CA6 particles A.

[0053] (Comparative Example 2) Regarding the CA6 particles A obtained above, they were pulverized using a jet mill for 5 minutes to obtain CA6 particles J.

[0054] When observing the fracture surface of the SEM image by a scanning electron microscope for the obtained CA6 particles A - J, it was found that a large number of secondary particles with a porous structure composed of a plurality of scaly primary particles aggregated (sintered).

[0055] (X - ray Diffraction Analysis) Regarding the obtained CA6 particles A - J, using an X - ray diffractometer, from the X - ray diffraction spectrum obtained by the powder X - ray diffraction analysis method, it was confirmed that a plurality of peaks corresponding to each crystal phase were almost those corresponding to CaO·6Al2O3. Also, as a result of identifying and quantifying the mineral composition (%) by the Rietveld method from the X - ray diffraction spectrum, the content of CaO·6Al2O3 in CA6 particles A - J was 80 mass% or more respectively.

[0056] (ICP Emission Analysis) The content of boric acid contained in the obtained CA6 particles A - J was measured by ICP (Inductively Coupled Plasma) emission analysis method. The results are shown in Table 1.

[0057] <Bulk density> The obtained CA6 particles A to J were allowed to fall naturally and placed in a SUS container with an internal volume of 400 cm 3 until it overflowed from the mouth of the container. Subsequently, tapping was performed 10 times with a drop height of more than 1 cm. Subsequently, after shaving off the CA6 particles overflowing from the mouth of the container, the increment in the weight of the container (g) was divided by the internal volume of the container (cm 3 ) to obtain a value, and the obtained value was taken as the bulk density (g / cm 3 ). The results are shown in Table 1.

[0058] <Particle size> The obtained CA6 particles A to J were sieved using a sieve with a mesh size of 1 mm, and the remaining amount remaining on the sieve was 0% by weight in all cases. The volume frequency particle size distribution of the obtained CA6 particles A to J was obtained by the laser diffraction scattering method. In the volume frequency particle size distribution, the particle size at which the cumulative value becomes 10% was defined as D10, the particle size at which the cumulative value becomes 50% was defined as D50, and the particle size at which the cumulative value becomes 90% was defined as D90. The results are shown in Table 1.

[0059]

Table 1

[0060] The above CA6 particles A to J were evaluated for the following evaluation items.

[0061] <Peeling suppression and clogging> Using the above CA6 particles A to J, an inorganic fiber molded body was manufactured according to the following procedure. First, as an inorganic fiber filler, 32% by mass of alumina fiber (manufactured by Denka Co., Ltd., product name: B80K2, composition ratio (mass ratio) Al2O3:SiO2 = 80%:20%, bulk, true specific gravity: 3.4, average fiber length (diameter): 3.0 μm), as an inorganic porous filler, 59% by mass of the above CA6 particles A to J, as an inorganic binder, 5% by mass in terms of solid content of colloidal silica (solid content concentration 30% by mass, manufactured by Nissan Chemical Industries, Ltd.), and as an organic binder, 4% by mass of starch (manufactured by Nippon Starch Chemical Co., Ltd.) were wet-mixed for 20 minutes to prepare an aqueous slurry (mixture) with a slurry concentration (total content ratio of inorganic fiber filler, inorganic porous filler, organic binder, and inorganic binder) of 2.0% by mass. Into the obtained aqueous slurry, a cylindrical molding die equipped with a wire mesh having an opening of 80 mesh and a diameter of 210 mm was immersed while being sucked by a vacuum pump from below the bottom mesh. By sucking the aqueous slurry, the raw materials were deposited on the wire mesh, and when the thickness of the deposited layer exceeded 30 mm, the molding die was taken out from the aqueous slurry to produce a columnar hand-formed body. After stopping the suction and demolding, the plate-shaped hand-formed body was dried in a hot air dryer at 100 °C for 16 hours, and then the upper and lower parts of the hand-formed body were cut and polished so that the thickness became 25 mm to produce a plate-shaped hand-formed molded body (inorganic fiber molded body).

[0062] The CA6 particles of Examples 1 to 8 were suppressed from peeling off from the inorganic fiber molded body formed by the hand-forming method as compared with Comparative Example 1, and showed the result that clogging of the wire mesh was less likely to occur during the hand-forming process of the inorganic fiber molded body as compared with Comparative Example 2. Such CA6 particles of Examples 1 to 8 can be suitably used for an inorganic fiber molded body composed of a hand-formed molded body.

[0063] This application claims the priority based on Japanese Patent Application No. 2022-001850 filed on January 7, 2022, and incorporates the entire disclosure thereof herein.

Claims

1. CA particles used for forming an inorganic fiber molded body, ６ which are contained in a crystal phase with CaO·6Al ２ O ３ and when the CA particles are sieved using a sieve with an opening of 1 mm, the remaining amount remaining on the sieve is 0% by weight, ６ and when the particle diameter at which the cumulative value is 50% in the volume frequency particle size distribution of the CA particles measured by the laser diffraction scattering method is defined as D50, D50 is 10.0 μm or more and 40.0 μm or less, ６ CA particles. CA ６ particles.

2. CA particles according to Claim 1, ６ which are when the particle diameter at which the cumulative value is 10% in the volume frequency particle size distribution is defined as D10, (D50 - D10) is 6.0 μm or more and 30 μm or less, CA ６ particles.

3. CA particles according to Claim 1 or 2, ６ which are when the particle diameter at which the cumulative value is 90% in the volume frequency particle size distribution is defined as D90, D90 is 350 μm or less, CA ６ particles.

4. CA particles according to Claim 1 or 2, ６ which are and have a bulk density of 0.6 g / cm ３ or more and 0.9 g / cm ３ or less, CA ６ particles.

5. CA particles according to Claim 1 or 2, ６ which are and ６ the boron content contained in the CA particles is 0.002% by mass or more and 0.05% by mass or less, CA ６ particles.

6. The CA according to claim 1 or 2 ６ A step of preparing a water slurry containing particles and an inorganic fiber filler; A step of obtaining an inorganic fiber formed body by removing water in the water slurry, the method for producing an inorganic fiber formed body comprising: A method for producing an inorganic fiber formed body.

7. A method for producing an inorganic fiber formed body according to claim 6, wherein during the step of preparation, the water slurry contains an inorganic binder and / or an organic binder.

8. A method for producing an inorganic fiber formed body according to claim 6, wherein during the step of preparation, the inorganic fiber filler contains alumina fiber.

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