JP4611071B2 - Light weight inorganic board and method for producing the light weight inorganic board - Google Patents

Description

  The present invention relates to a lightweight inorganic board used for a building board such as an outer wall material and an interior material, and a method for producing the inorganic board.

BACKGROUND OF THE INVENTION
An inorganic plate obtained by molding and firing ceramic powders such as silica and alumina into a plate shape is excellent in durability, and is frequently used as a building plate having a high-quality design with a sense of beauty and texture.
The inorganic plate is manufactured by adding a binder and water to a ceramic powder and kneading, forming the kneaded product into a plate shape by extrusion molding or casting, and firing the plate-shaped product, It has high hardness and poor machinability, and it is difficult to easily cut to a predetermined size on site. In the case of a large plate, the weight is large and labor is required for transportation and construction work, and when it is attached to a wall frame or the like, the weight load on the wall frame becomes large.

[Conventional technology]
Therefore, as a means for solving the problems of the above-mentioned inorganic board, a mat is formed by spraying a raw material mixture in which a flammable organic material such as blast furnace slag or slaked lime is added with a combustible organic component such as wood chips or wood powder on a substrate. A porous and lightweight inorganic board is formed by forming, pressing and curing the mat to form a green board, firing the green board, and burning off the combustible organic components contained in the green board. It has been proposed to obtain. (For example, refer to Patent Documents 1 to 5).

JP-A-6-345529 JP-A-6-144923 Japanese Patent Laid-Open No. 9-30873 JP 2005-60163 A Japanese Patent Application No. 2003-31856

In the above prior art, the strength of the green plate obtained by press-curing and curing the mat of the raw material mixture is not sufficient, so that it is easily chipped, deformed or collapsed, and there is a problem in handling properties. In addition, when a concavo-convex pattern is formed on the plate surface by embossing, a too deep concavo-convex pattern cannot be formed, and thus the concavo-convex pattern is restricted. Furthermore, there is a problem that the strength required for cutting a real edge or the like on the edge of the plate cannot be obtained, and it is easily chipped during processing.
In order to increase the strength of the green plate, curing may be performed for a long time, but if so, the production efficiency of the inorganic plate is deteriorated.

In the present invention, as means for solving the above conventional problems, a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass 15 to A hardened and fired layer of a raw material mixture containing 50% by mass, glassy-containing material 1 to 15% by mass, aggregate 10 to 45% by mass, and reinforcing fiber 20 to 30% by mass is used as a front and back layer. 15 to 50% by weight of a mixture of a hydraulic inorganic material other than the inorganic inorganic material in a ratio of 1: 2.5 to 2.5: 1, 1 to 15% by weight of a vitreous material, 0 to 30% by weight of aggregate, A lightweight inorganic board having a cured and fired layer of a raw material mixture containing 20 to 30% by mass of a reinforcing fiber, 15 to 30% by mass of a combustible organic component and / or an inorganic lightweight body, and a cement-based inorganic material and the cement-based material Hydraulic inorganic materials other than inorganic materials 15 to 35% by weight of a mixture of 1: 2.5 to 2.5: 1 by weight, 1 to 15% by weight of a vitreous material, 20 to 45% by weight of aggregate, and 20 to 30% by weight of reinforcing fibers 15 to 35% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass. Curing and firing of raw material mixture containing 1 to 15% by mass of glassy material, 10 to 30% by mass of aggregate, 20 to 30% by mass of reinforcing fiber, 15 to 30% by mass of flammable organic component and / or inorganic lightweight body 35 to 50% by mass of a lightweight inorganic plate having a layer as a core layer, or a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass (Excluding 35% by mass), glassy material 1-15 %, A hardened and fired layer of a raw material mixture containing 10 to 30% by mass of aggregate and 20 to 30% by mass of reinforcing fibers is used as a front and back layer, and 1 of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material : A mixture of 35 to 50% by mass (excluding 35% by mass) of 2.5 to 2.5: 1 mass ratio, 1 to 15% by mass of a vitreous material, 0 to 10% by mass of aggregate, and 20 to 30 of reinforcing fibers The present invention provides a lightweight inorganic plate having a core layer of a cured and fired layer of a raw material mixture containing 15% by mass, 15% by mass of a combustible organic component and / or an inorganic lightweight body.
As a desirable method for producing the lightweight inorganic board, a raw material mixture for the front and back layers having the above composition is spread on a substrate to form a surface layer or a back layer mat, and the raw material mixture for the core layer having the above composition is applied to the front layer or the surface layer. 3 layers obtained by spraying on the back layer mat to form the core layer mat and further spraying the raw material mixture for the front and back layers onto the core layer mat to form the back layer or the surface layer mat. A mat having a structure is pressed and hardened in the presence of moisture to obtain a green plate, which is then fired.
The firing temperature is desirably set in a range of 1100 ° C. or higher (including 1100 ° C.) and 1300 ° C. or lower (including 1300 ° C.).

[Action]
In the present invention, a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material are used as the hydraulic inorganic material. The cement-based inorganic material has a fast hydraulic reaction. When other hydraulic inorganic materials are added to the inorganic material, the hydraulic reaction of the mixture is further promoted, so that the curing progresses very smoothly in a short time in the process of pressing and curing the three-layer mat. In addition, the other hydraulic inorganic materials improve the hard and brittle properties of the cured cement-based inorganic material, and a green plate having high strength and good impact resistance can be obtained.

〔effect〕
Therefore, in the present invention, the raw plate is not easily chipped, deformed or collapsed during handling or actual cutting processing, so that handling and workability are improved, and deep uneven patterns are easily formed by embossing. The degree of freedom of the concavo-convex pattern can be increased. Furthermore, the time required for the compression curing and curing is shortened, and the production efficiency is improved.

The present invention is described in detail below.
[Cement-based inorganic materials]
Examples of the cement-based inorganic material used in the present invention include ordinary Portland cement, early-strength Portland cement, alumina cement, blast furnace slag cement, silica cement, fly ash cement and the like.
The cement-based inorganic material has a high hydraulic reaction rate.

[Other hydraulic inorganic materials]
Examples of other hydraulic inorganic materials used in the present invention include slags such as blast furnace slag, electric furnace oxidation slag and electric furnace reduction slag, limes such as slaked lime and quicklime, gypsum, magnesium carbonate and the like. The hydraulic inorganic material is mixed with the cement-based inorganic material to further promote the hydraulic reaction, greatly reducing the time required for compression bio-curing, and improving the strength and impact resistance of the resulting green plate .

[Glass-containing material]
Furthermore, in this invention, the vitreous content material which fuse | melts by baking and becomes a binder is added. Examples of such a vitreous material include shirasu, fly ash, mine stone, glass powder, and ground glass. What is desirable as the glassy-containing material is a low-melting glass having a softening point of 900 ° C. or lower. As the low-melting glass, a glass having an increased content of low-melting-point components such as PbO, B ₂ O ₃ and ZnO is used. For example, E glass powder having a softening point of 840 ° C. and a melting point of 1200 ° C. is a desirable low-melting glass. E glass, or electrical glass, is a glass fiber powder, the average particle size is 30 μm, the main components are SiO ₂ 54 mass%, Al ₂ O ₃ 15 mass%, CaO 23 mass%, B ₂ O ₃ 7 mass%. Because it contains B ₂ O ₃ , it has a low melting point and enables low-temperature firing at around 1000 ° C.

〔aggregate〕
Furthermore, in the present invention, an aggregate which is melted by firing and becomes a main element of the plate structure is added. Examples of the aggregate include clay minerals such as ceramic stone, feldspar, wax stone, kaolin, halosite, kibushi clay, glazed clay, sericite, chamotte (ceramic stone powder), dolomite, silica sand, quartzite powder, There are siliceous materials such as diatomaceous earth, glitter, and silica fume. Among the above-mentioned aggregates, silica sand or quartzite powder having a brain value of 3800 and a SiO ₂ purity of 95% by mass or more, or chamotte is preferable.

[Reinforcing fiber]
Furthermore, in the present invention, reinforcing fibers are added to suppress expansion and contraction due to firing. Examples of the reinforcing fibers include mineral fibers such as wollastonite and sepiolite, metal fibers such as steel fibers and stainless fibers, glass fibers, and ceramic fibers. A desirable reinforcing fiber is wollastonite. Wollastonite has a larger aspect ratio (15) than ordinary reinforcing fibers. Wollastonite improves the dispersibility of the raw material mixture, and the dry method in which the raw material mixture is sprayed on the template prevents the formation of agglomerates and lumps in the raw material mixture and improves the spraying workability. . Generally, wollastonite having an average fiber length of 600 μm and an average fiber diameter of 40 μm is used. Further, wollastonite improves shape retention and cutting properties, and facilitates the production of large size plates.

[Flammable organic components]
In the present invention, a flammable organic component may be added together with the inorganic lightweight body or in place of the inorganic lightweight body in order to burn out during firing and form a porous structure in the core layer. Examples of such combustible organic components include wood materials such as wood chips, wood fiber bundles, wood pulp, wood wool, and wood flour, and organic materials such as polyester fibers, polyamide fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, and vinylon fibers. There are synthetic resin components such as fibers, expanded polystyrene beads, expandable polyethylene beads, expandable polypropylene beads, or wood cement board waste.
Wood cement board waste materials used as a source of combustible organic components are wood reinforcing materials such as wood chips, wood fiber bundles, wood pulp, wood wool, wood flour, ordinary Portland cement, early strength cement, alumina cement, blast furnace Using a raw material mixture mainly composed of cements such as slag cement and fly ash cement, limes such as quick lime and slaked lime, or hydraulic inorganic materials such as gypsum and magnesium carbonate, dry method, semi-dry method, wet method The waste material of the wood cement board formed into a plate shape by the extrusion molding method or the like is used to grind and recycle the end material in the manufacturing process and these waste materials generated at the time of extension and reconstruction.
The wood cement board usually contains 10 to 30% by mass of the wood content.

  The wood cement board may further contain organic fibers such as polyester fiber, polyamide fiber, polyethylene fiber, polypropylene fiber, acrylic fiber and vinylon fiber, and flammable organic components such as expanded polystyrene beads, polyethylene beads and polypropylene beads. During burning, these combustible organic components are also burned out, contributing to the porous structure of the core layer together with the wood.

  The wood cement board waste is usually pulverized to a particle size of about 10 to 100 μm by an impact pulverizer, a grinding pulverizer, or the like, and used as a raw material of the present invention.

[Inorganic lightweight body]
In the present invention, in order to form a porous structure in the core layer, an inorganic lightweight body may be added instead of the combustible organic component or together with the combustible organic component. Examples of the inorganic lightweight body include pearlite, fly ash balloon, shirasu balloon, and glass foam, and those having a bulk specific gravity of 0.4 or less and a compressive strength of 10 N / mm ² or more are preferable.

[Raw material mixture for front and back layers]
As the raw material for the front and back layers, the cement-based inorganic material, the other hydraulic inorganic material, the vitreous material, the aggregate, and the reinforcing fiber are used.
In the raw material mixture for the front and back layers, 15-50% by mass of a mixture of the cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass, The ratio is about 1 to 15% by mass of the vitreous material, 10 to 45% by mass of the aggregate, and 20 to 30% by mass of the reinforcing fiber. When the aggregate is added in an amount exceeding 45% by mass, the specific gravity of the plate becomes high, and it is difficult to reduce the weight, and the workability also deteriorates. In the present invention, since other hydraulic inorganic materials are used together with the cement-based inorganic material, the strength of the plate and the resistance to freezing and thawing are ensured, and the aggregate does not necessarily have to be added. Moreover, the combustible organic component and / or inorganic lightweight body which are used for a core layer may be added to the said raw material mixture for front and back layers.

  In the practice of the present invention, the raw material mixture for the front and back layers is prepared in two compositions within the above range. That is, the composition of the raw material mixture (1) for the front and back layers is 15 to 35 mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1. %, A raw material mixture containing 1 to 15% by mass of a glassy-containing material, 20 to 45% by mass of an aggregate, and 20 to 30% by mass of a reinforcing fiber, and a raw material mixture for front and back layers (2) A mixture of hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass 35 to 50% by mass (excluding 35% by mass), glassy material 1 to 15% by mass The raw material mixture contains 10-30% by mass of aggregate and 20-30% by mass of reinforcing fibers.

[Raw material mixture for core layer]
As a raw material for the core layer, 15-50% by mass of a 1: 2.5 to 2.5: 1 mass ratio mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material, a glassy-containing material It is set to a ratio of 1 to 15% by mass, aggregate 0 to 30% by mass, reinforcing fibers 20 to 30% by mass, combustible organic components and / or inorganic lightweight bodies 15 to 30% by mass.
In the raw material mixture for the core layer, when the amount of the combustible organic component and / or the inorganic lightweight body is less than 15% by mass, the core layer is not sufficiently porous and the weight is not reduced. On the other hand, when the amount of the combustible organic component and / or the inorganic lightweight body is more than 30% by mass, the core layer becomes excessively porous, resulting in poor mechanical strength and frost resistance.

  In the practice of the present invention, the core layer raw material mixture is prepared in two compositions within the above range. That is, the composition of the core layer raw material mixture (1) is 15 to 35 masses of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1. %, Glass material-containing material 1-15% by mass, aggregate 10-30% by mass, reinforcing fiber 20-30% by mass, combustible organic component and / or inorganic lightweight body 15-30% by mass, core mixture, core The composition of the layer raw material mixture (2) is 35 to 50% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass ( 35% by mass), 1-15% by mass of glass-containing material, 0-10% by mass of aggregate, 20-30% by mass of reinforcing fibers, 15-30% by mass of flammable organic component and / or inorganic lightweight body The raw material mixture layer.

[Method for producing lightweight inorganic board]
As a method for producing the lightweight inorganic board of the present invention, a semi-dry method using a raw material mixture in which a predetermined amount (usually 5 to 20% by mass) of water is added is generally applied, but water is added to the raw material mixture. Alternatively, a dry method in which water is added immediately before or after compression curing biocure may be applied.
That is, in the production method of the present invention, a raw material mixture for front and back layers is formed on a substrate such as a template, a conveyance plate, and a flat plate to form a surface layer or a back layer mat, and a core is formed on the surface layer or the back layer mat. The raw material mixture for the layer is sprayed to form the core layer mat, the raw material mixture for the front and back layers is sprayed on the core layer mat to form the back layer or the surface layer mat, and the three-layer structure thus obtained is formed. The mat is cured by pressing and curing in the presence of moisture, and the resulting inorganic plate green plate is fired to obtain the lightweight inorganic plate of the present invention.

In the above method, a predetermined uneven shade pattern may be formed on the substrate surface. The pressing is usually performed at a surface pressure of 5 to 8 MPa in a pressing apparatus in which a substrate is further stacked on a formed three-layer mat, and the upper surface of the mat is used as a surface to the upper substrate surface. A predetermined uneven shade pattern may be formed.
Curing and curing is performed in the above-mentioned pressed state, and a condition of 6 to 10 hours is usually employed at a temperature of 45 to 65 ° C.
After curing and curing, it is depressurized and desirably dried in an absolutely dry state, and subjected to predetermined processing such as actual processing. Further, if desired, a glaze is applied to at least the surface of the raw inorganic plate. As the glaze used in the present invention, general glazes such as lead yu, frit yu, bristol yu, porcelain yu and the like are used. Thereafter, the raw inorganic plate is introduced into a firing furnace and fired. Desirable firing conditions are 1100 ° C. or higher (including 1100 ° C.) and 1300 ° C. or lower (including 1300 ° C.), preferably 1150 ° C. or higher (including 1150 ° C.) and 1250 ° C. or lower (including 1250 ° C.) for 10 to 20 minutes. The following conditions are adopted.
The lightweight inorganic board thus produced usually has a thickness of 12 to 25 mm, a specific gravity of the front and back layers of 1.5 to 1.8, and a specific gravity of the core layer of about 0.8 to 1.3.

[Examples 1-6, Comparative Examples 1-3]
Spread the raw material mixture for the front and back layers shown in Table 1 on the template, spread the raw material mixture for the core layer on it, and form a mat with a three-layer structure on which the raw material mixture for the front and back layers is further spread, The mat having the three-layer structure is subjected to pressing and curing and curing for 10 hours under the conditions of a surface pressure of 5 MPa and a temperature of 50 ° C. in the presence of moisture, and the resulting inorganic plate green plate is kept in an absolutely dry state at a temperature of 105 ° C. for 24 hours. Light weight inorganic materials of Examples 1 to 6 and Comparative Examples 1 to 3 having a three-layer structure which is dried, introduced into a baking furnace having a glaze applied to the surface, and baked for 10 minutes at the temperature shown in the table to a thickness of 18 mm. A plate sample was prepared. The following physical property evaluation was performed about the said lightweight inorganic board sample. The results are shown in Table 1.

〔Evaluation of the physical properties〕
(1) Shrinkage ratio: Ratio of dimension after molding to dimension after firing (%)
(2) Specific gravity: Absolute dry specific gravity
(3) Bending strength (after raw plate and firing): Conforms to JIS A 1408 (N / mm ² )
(4) High surface design: The following standards are given for a cured product formed by a semi-dry method using a mold plate having a concave convex portion with an embossing depth of 11 mm and an embossing angle of 60 °, set to a plate thickness of 25 mm by a table test. It was evaluated with.
◎: No irregularity ○: Slight burrow in the convex part △: Slightly missing in the convex part ×: Large chipped in the convex part (pattern missing)
(5) Cutability: Can be cut with a hand saw, and can be cut smoothly without cracks or chipping. (If you can cut smoothly ○)
(6) Freezing and thawing resistance: ASTM B method Whether there is any abnormality after 300 cycles. (No abnormality ○)
(7) Impact resistance: According to JIS A 1408, the height at which a 500 g iron ball does not crack when dropped. (M)

  Referring to Table 1, the sample of Example 1 is cement-based inorganic material: other hydraulic inorganic material = 1: 2.5, and the amount of cement-based inorganic material and other hydraulic inorganic material is within the set range. However, since there are few, the intensity | strength of the raw board after hardening is a little low and the design property is also slightly bad, but there is no trouble practically. The sample of Example 2 is cement-based inorganic material: other hydraulic inorganic material = 1: 1, and the sample of Example 3 is cement-based inorganic material: other hydraulic inorganic material = 2.5: 1. In addition, since the amount of the cement-based inorganic material and other hydraulic inorganic materials was a large addition amount within the set range, the strength after curing was large and other physical properties were also good. In the samples of Examples 4 to 6, the mixing ratio of the cement-based inorganic material to the other hydraulic inorganic material of the samples of Examples 1 to 3 is the same, but the cement-based inorganic material and the other hydraulic inorganic material are mixed. Samples with a large addition amount and a high firing temperature of 1160 ° C. all had high strength after curing, and other physical properties showed good results.

  Since the sample of Comparative Example 1 does not use a cement-based inorganic material and is within a set range but only a hydraulic inorganic material other than the cement-based inorganic material, the bending strength of the green board after curing is low, and therefore the surface height is high. The designability is significantly reduced. Since the sample of Comparative Example 2 is only a cement-based inorganic material and no other hydraulic inorganic material is added, the bending strength of the green plate after curing is high, but the plate after baking becomes too hard and inferior in impact resistance. It was. In the sample of Comparative Example 3, the cement-based inorganic material and other hydraulic inorganic materials are within the set range, but the firing temperature is low at 1050 ° C. due to the large amount of 35% by mass or more. The strength is inferior.

  The inorganic board of the present invention has high productivity, light weight, good transportability, workability, workability, excellent mechanical properties such as impact resistance and freeze-thaw resistance, and deep uneven pattern on the surface Since it is excellent in design properties, it is useful for exterior wall materials and interior materials.

Claims (7)

15 to 50% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass , containing B ₂ O ₃ as a vitreous material A cement-based inorganic material and the cement comprising a cured and fired layer of a raw material mixture containing 1 to 15% by mass of E glass powder , 10 to 45% by mass of aggregate, and 20 to 30% by mass of wollastonite as a reinforcing fiber. E glass powders 1 to 15 containing B ₂ O ₃ as a glassy material, 15 to 50% by weight of a mixture of 1: 2.5 to 2.5: 1 by weight with a hydraulic inorganic material other than a system inorganic material A cured and fired layer of a raw material mixture containing 10% by mass, aggregate 0-30% by mass, wollastonite 25-30 % by mass as a reinforcing fiber, and combustible organic component and / or inorganic lightweight body 15-30% by mass is a core layer and, said surface backing layer and the core layer And pressing cured cured in the presence of moisture, further (including 1100 ° C.) 1100 ° C. or higher 1300 ° C. or less lightweight inorganic board characterized that you have been fired 10-20 minutes (1300 including ° C.). 15 to 35% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass , containing B ₂ O ₃ as a vitreous material The hardened and fired layer of a raw material mixture containing 1 to 15% by mass of E glass powder, 20 to 45% by mass of aggregate, and 20 to 30% by mass of wollastonite as a reinforcing fiber is used as a front and back layer, and a cement-based inorganic material and the cement E glass powder 1 to 15 containing B ₂ O ₃ as a vitreous material, 15 to 35% by mass of a mixture of 1: 2.5 to 2.5: 1 mass ratio with a hydraulic inorganic material other than the organic inorganic material A core layer comprising a cured and fired layer of a raw material mixture containing 10% by mass, 10-30% by mass of aggregate, 25-30 % by mass of wollastonite as a reinforcing fiber , and 15-30% by mass of a combustible organic component and / or an inorganic lightweight body. and, said surface back layer and the core Lightweight inorganic board is pressing aged cured in the presence moisture, it characterized that you have been fired 10-20 minutes further (including 1100 ° C.) 1100 ° C. or higher 1300 ° C. or less (including 1300 ° C.). 35 to 50% by mass (excluding 35% by mass) of a 1: 2.5 to 2.5: 1 mass ratio mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material, a glassy material As the front and back layers, a raw material mixture cured and fired layer containing 1 to 15% by mass of E glass powder containing B ₂ O ₃ , 10 to 30% by mass of aggregate, and 20 to 30% by mass of wollastonite as a reinforcing fiber is used as a cement. 35 to 50% by mass (excluding 35% by mass) of a 1: 2.5 to 2.5: 1 mass ratio of an inorganic inorganic material and a hydraulic inorganic material other than the cement inorganic material, as a vitreous material E glass powder containing B ₂ O ₃ 1 to 15% by mass, aggregate 0 to 10% by mass, wollastonite 25 to 30% by mass as a reinforcing fiber, flammable organic component and / or inorganic lightweight body 15 to 30% % Of the raw material mixture containing The reduction baked layer and the core layer, said surface backing layer and the core layer is pressing aged cured in the presence of moisture, 10 to 20 at further 1100 ° C. or more (including 1100 ° C.) 1300 ° C. or less (including 1300 ° C.) lightweight inorganic board characterized that you have been divided fired. 15 to 50% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass , containing B ₂ O ₃ as a vitreous material A surface layer or back layer mat is formed by spraying a raw material mixture for front and back layers containing 1 to 15% by mass of E glass powder , 10 to 45% by mass of aggregate, and 20 to 30% by mass of wollastonite as a reinforcing fiber on a substrate. 15 to 50% by mass of a 1: 2.5 to 2.5: 1 mass ratio mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material, and B ₂ O as a vitreous material ₃ containing 1 to 15% by mass of E glass powder , 0 to 30% by mass of aggregate, 25 to 30% by mass of wollastonite as a reinforcing fiber , 15 to 30% by mass of combustible organic component and / or inorganic lightweight body Raw material mixture for core layer The core layer mat is formed by spraying a product on the front layer or back layer mat, and the raw material mixture for the front and back layers is further sprayed on the core layer mat to form the back layer or the surface layer mat. The resulting three-layered mat is pressed and cured in the presence of moisture to form a green plate, and the green plate is 10 to 20 at 1100 ° C. (including 1100 ° C.) or 1300 ° C. (including 1300 ° C.). The method for producing a lightweight inorganic board according to claim 1, wherein the calcining is performed . 15 to 35% by mass of a mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material in a ratio of 1: 2.5 to 2.5: 1 by mass , containing B ₂ O ₃ as a vitreous material A surface layer or a back layer mat is formed by spreading a raw material mixture for front and back layers containing 1 to 15% by weight of E glass powder, 20 to 45% by weight of aggregate, and 20 to 30% by weight of wollastonite as a reinforcing fiber on a substrate. 15 to 35% by mass of a 1: 2.5 to 2.5: 1 mass ratio mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material, and B ₂ O as a vitreous material ₃ containing E glass powder 1-15% by mass, aggregate 10-30% by mass, wollastonite 25-30 % by mass as a reinforcing fiber, combustible organic component and / or inorganic lightweight body 15-30% by mass Raw material for core layer The compound is sprayed on the front or back layer mat to form the core layer mat, and the raw material mixture for the front and back layers is further sprayed onto the core layer mat to form the back layer or the surface layer mat. The mat having the three-layer structure thus obtained is pressed and hardened in the presence of moisture to obtain a green plate. The green plate is 1100 ° C. or higher (including 1100 ° C.) and 1300 ° C. or lower (including 1300 ° C.). The method for producing a lightweight inorganic board according to claim 2, wherein the firing is performed for 20 minutes . 35 to 50% by mass (excluding 35% by mass) of a 1: 2.5 to 2.5: 1 mass ratio mixture of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material, a glassy material As a surface layer, a raw material mixture containing 1 to 15% by mass of E glass powder containing B ₂ O ₃ , 10 to 30% by mass of aggregate, and 20 to 30% by mass of wollastonite as a reinforcing fiber is dispersed on a substrate. The backing layer mat is formed, and a mixture of 35 to 50% by mass (35% by mass) of a 1: 2.5 to 2.5: 1 mass ratio of a cement-based inorganic material and a hydraulic inorganic material other than the cement-based inorganic material. 1) 15% by mass of E glass powder containing B ₂ O ₃ as a vitreous material, 0-10% by mass of aggregate, 25-30 % by mass of wollastonite as a reinforcing fiber, combustible organic component and / or Or inorganic lightweight body 15 ~ A core layer raw material mixture containing 0% by mass is sprayed onto the front or back layer mat to form the core layer mat, and the front or back layer raw material mixture is further sprayed onto the core layer mat to form a back layer or The surface layer mat is formed and the three-layered mat thus obtained is pressed and hardened in the presence of moisture to obtain a green plate. The green plate is 1100 ° C. or higher (including 1100 ° C.) and 1300 ° C. or lower. The method for producing a lightweight inorganic board according to claim 3, wherein baking is performed for 10 to 20 minutes (including 1300 ° C.) . The method for producing a lightweight inorganic board according to claim 4, 5 or 6, wherein the firing is set at a temperature of 1150 ° C or higher (including 1150 ° C) and 1300 ° C or lower (including 1300 ° C) for 10 to 20 minutes. .