JPH0533465A - Inorganic building board - Google Patents

Abstract

PURPOSE:To provide a lightweight and inorganic construction plate offering enough performance as a setting bed material. CONSTITUTION:An external layer mainly composed of mineral fiber and inorganic powder body and so formed with the addition of a bonding agent as to have specific gravity of 0.7 or more, is laid on both surfaces of a plate-like heat wood mainly composed of inorganic foam and so formed with the addition of a suitable amount of a fibrous material and a bonding agent as to have specific gravity of 0.4 or less. In this case, overall specific gravity is kept at 0.55 or less. According to this construction, both surfaces of the lightweight and plate-like heart wood are covered with the hard and dense external layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic building board used as a wall base material or the like.

[0002]

2. Description of the Related Art Generally,
Inorganic building boards used as wall base materials, etc. are required to have predetermined strength, surface hardness, thermal conductivity, etc. from the viewpoint of use, and are lightweight and have a predetermined overall hardness from the viewpoint of construction. However, it is required that it can be screwed. Therefore, gypsum board is widely used as a wall base material as compared with the conventional example.

However, in recent years, there has been a demand for a base material which is lighter than gypsum board and which meets the fire protection regulations due to the aging of construction workers and the congestion of city traffic. Therefore, in order to reduce the weight of the gypsum board, it has been considered to generate bubbles inside the gypsum board or to mix an inorganic foam, but this method has a problem that the strength of the gypsum board decreases. .. On the other hand, in order to reduce the weight and maintain the strength at the same time, it is conceivable to mix an organic fiber such as pulp into the gypsum board, but this method has a problem that the fireproof property is impaired.

In view of the above problems, it is an object of the present invention to provide a lightweight inorganic building board having sufficient performance as a base material.

[0005]

Means for Solving the Problems The present inventor has a three-layer structure by differentiating the composition of the plate-shaped core material and the outer layer portions provided on the front and back surfaces thereof, and thus is lighter than the gypsum board,
Moreover, they have found that an inorganic building board having sufficient performance as a base material can be obtained, and have completed the present invention. In order to achieve the above-mentioned object, the gist of the present invention is to provide a mineral substance on the front and back surfaces of a plate-like core material mainly composed of an inorganic foam and a fibrous material and having a specific gravity of 0.4 or less formed by adding a binder. Mainly composed of fibers and inorganic powder, with a specific gravity of 0.
It is an inorganic building board characterized by having an outer layer portion of 7 or more and having an overall specific gravity of 0.55 or less.

The inorganic foamed material forming the plate-shaped core material is for reducing the weight while maintaining the compressive strength.
There are pearlite, shirasu foam, silica flour, glass foam, etc. These can be used alone or in combination of two or more kinds. The composition ratio of the inorganic foam in the plate-shaped core material is preferably 50 to 90% by weight. When the amount is 50% by weight or less, the ratio of the fibrous substance relatively increases, so that the strength is improved, but the effect of lowering the specific gravity cannot be obtained. At the same time, it becomes difficult to make paper uniformly.

The fibrous material forming the plate-shaped core material is for connecting the inorganic foams to each other, and examples thereof include rock wool, slag wool, pulp and polypropylene fiber. Or 2
It can be used in combination of two or more species. The fibrous material is for connecting the inorganic foams to form a plate shape, and is added in an amount of at least 3% by weight, but if it is too much, the amount of the inorganic foams will relatively decrease and the weight reduction will be achieved. The purpose cannot be achieved.

The binder forming the plate-shaped core material is for connecting and integrating the fibrous material and the inorganic foam,
For example, polyvinyl alcohol resin, synthetic resin such as phenol resin, starch and the like can be mentioned.
Alternatively, two or more kinds can be used in combination.

Generally, the more the binder and the organic fibers are, the more the bending strength is improved. Therefore, it is effective from the viewpoint of strength to mix the organic fibers such as pulp into the plate-shaped core material in terms of strength. It is effective in terms of aspects. However, in order to obtain an inorganic building board as a semi-incombustible material, it is necessary that the total amount of organic components in the plate-shaped core material is 15% by weight or less including the binder. Further, in order to obtain an inorganic building board as a non-combustible material, it is necessary to set the total amount of organic components to 7% by weight or less, so it is preferable to use mineral fibers as the fibrous material.

The reason why the specific gravity of the plate-shaped core material is 0.4 or less is that
This is because if the specific gravity is 0.4 or more, it becomes difficult to reduce the weight of the inorganic building board. Since the plate-shaped core material forms an intermediate layer of the inorganic building board, increasing the thickness of the plate-shaped core material has an advantage that the bending moment that the inorganic building board can withstand becomes large.

The mineral fibers forming the outer layer include, for example, rock wool, slag wool, mineral wool,
Glass fiber etc. can be mentioned, these are alone,
Alternatively, two or more kinds can be used in combination. And
The composition ratio of the mineral fiber in the outer layer is 20 to 60% by weight.
Is preferred. When the content is 20% by weight or less, the bending strength is low and the surface is easily broken during screw driving,
This is because if it is 60% by weight or more, the amount of the inorganic powder to be added becomes low, and the surface hardness and overall hardness cannot be increased.

The inorganic powdery material forming the outer layer portion is for increasing hardness and screwing performance while maintaining fire resistance. Examples include calcium carbonate, silica sand, microsilica, slag, and aluminum hydroxide. Etc. can be mentioned. Then, the composition ratio of the inorganic powder in the outer layer portion,
It is preferably 40 to 70% by weight. This is because if the amount is less than 40% by weight, the desired surface hardness cannot be obtained.
This is because when the content is 0% by weight or more, the ratio of the mineral fiber is relatively reduced, and the desired strength cannot be obtained. Further, the strength of the outer layer portion is highest when the inorganic powder having a particle size of about 150 μ is used, but the inorganic powder has an average particle size of 40 μ.
˜300 μ may be used.

The specific gravity of the outer layer portion is set to 0.7 or more for the following reason. That is, when the proportion of the inorganic powder is constant, for example, 60% by weight, and the composition of the other material is made different to form the outer layer portion, the specific gravity and surface hardness of the outer layer portion, and the specific gravity and bending strength are There is a correlation between them, and the surface hardness and bending strength increase as the specific gravity increases (FIGS. 1 and 2). Then, in practical use, in order to obtain the outer layer portion having substantially the same surface hardness and bending strength as the gypsum board, the specific gravity of the outer layer portion needs to be 0.7 or more.

Since the material and the amount of the binder forming the outer layer portion are the same as in the case of the above-mentioned plate-shaped core material, the description thereof will be omitted.

As described above, the more the binder and the organic fibers are, the more the bending strength is improved. Therefore, organic fibers such as pulp may be used in the outer layer portion instead of the mineral fibers. However, to obtain an inorganic building board as a semi-combustible material,
The total amount of organic components needs to be 15% by weight or less. Therefore, when organic fibers such as pulp are used instead of mineral fibers, it is necessary to consider that the total amount of organic components such as binder is within the above range. Further, in order to obtain an inorganic building board as a non-combustible material, it is necessary to set the total amount of organic components to 7% by weight or less, like the above-mentioned plate-shaped core material.

Next, a method for manufacturing an inorganic building board according to this embodiment will be described. For example, an inorganic foam, a fibrous substance, and a binder are suspended in water to obtain an aqueous slurry, which is wet-processed to obtain a wet mat to be a plate-shaped core material, while a mineral fiber, an inorganic powdery substance are obtained. , A binder is suspended in water to obtain an aqueous slurry, which is wet-processed to obtain a wet mat to be an outer layer part, and then the wet mat to be an outer layer part is formed on the front and back surfaces of the wet mat to be a plate-shaped core material. After the mats are laminated and pressed, they are dried and integrated,
There is a method of manufacturing an inorganic building board.

In the above-mentioned manufacturing method, the case where the wet mats are laminated and integrated has been described, but an existing manufacturing method such as a dry method or a combination of dry and wet methods can be selected.

[0018]

EXAMPLES Examples according to the present invention will be described below. (Example 1) Unit volume mass as an inorganic foam 0.08
(Kg / l) 82% by weight of perlite, 10% by weight of pulp as a fibrous material, phenol resin and starch as a binder at a total ratio of 8% by weight were added and suspended in water to obtain an aqueous slurry. While making a sheet-like core material with a thickness of 11 mm and a specific gravity of 0.15 by papermaking, 27% by weight of rock wool as mineral fiber, 60% by weight of calcium carbonate as inorganic powder, and phenol resin and starch as binder are combined. 8% by weight and 5% by weight of pulp as a reinforcing material, and then mixed in water to obtain an aqueous slurry,
After this was made into a paper to obtain an outer layer portion having a thickness of 2.0 mm and a specific gravity of 0.6, the outer layer portion was laminated on the front and back surfaces of the plate-shaped core material and integrated by pressing with a press to form a plate-shaped body. , Dried to a thickness of 9m
A sample having m and an overall specific gravity of 0.45 was obtained. The calcium carbonate used had a particle size of 50 mesh, and the perlite used had an average particle size of 300 μm.

Example 2 80% by weight of perlite having a unit volume mass of 0.08 (kg / l) as an inorganic foam, 13% by weight of rock wool as a fibrous substance, and a total of 7% phenol resin and starch as a binder. An aqueous slurry is obtained by kneading the mixture in a weight% ratio, and this is made into paper and has a thickness of 11 m.
m, a specific gravity of 0.15 while obtaining a plate-shaped core material having a mineral fiber content of 36% by weight of rockwool, an inorganic powder form of 57% by weight of calcium carbonate, and a binder of 7% by weight of phenol resin and starch. Aqueous slurry is obtained by kneading at a ratio, and this is made into paper and has a thickness of 2.0 mm and a specific gravity of 0.6.
After obtaining the outer layer part, the outer layer part is laminated on the front and back surfaces of the plate-shaped core material, and pressed and integrated with a press to form a plate-like body, which is dried to have a thickness of 9 mm and an overall specific gravity of 0.45. I got a board.
The calcium carbonate used had a particle size of 50 mesh, and pearlite had an average particle size of 300 μm.
I used the one.

Comparative Example A commercially available gypsum board having a thickness of 9 mm and a specific gravity of 0.74 was used as a sample.

The measurement results regarding the physical properties of the samples obtained in Examples 1 and 2 and Comparative Example are shown below. Example 1 Example 2 Comparative example Thickness (mm) 9.0 9.0 9.0 Specific gravity 0.45 0.45 0.74 Bending strength (kgf / cm ² ) 75 70 50 Surface hardness (kgf) 170 160 220 Screw penetration force (kgf) 18 20 27 Thermal conductivity (kal / mh ℃) 0.06 0.06 0.27 Fire resistance Quasi-non-combustible pass Non-flammable pass Quasi-non-flammable pass

The measurement results are obtained based on the following method. Bending strength: Based on JIS 5907-1977. Surface hardness: Based on JIS HARDNESS TESTER. Screw penetration force: Based on the test method according to JIS A5910. Thermal conductivity: Based on JIS A1412. Fire resistance: Based on JIS A1321.

As is clear from the above measurement results, the specific gravity of Examples 1 and 2 is smaller than that of Comparative Example by 25 to 40%.
The 40% smaller specific gravity means that when the standard size gypsum board has a weight of about 11 kg, the inorganic building board of the present invention having the same size has a weight of about 6.7 kg. Therefore, in the case of the gypsum board, even if only about half of the loadable volume of a truck or the like can be used due to weight limitation, the inorganic building board of the present invention can be loaded to the full loadable volume of a truck or the like. As a result, not only can physical distribution costs be greatly reduced, but also manual transportation and handling to the construction site becomes easy. In addition, Example 1,
Since the bending strength of No. 2 was about 40% higher than that of Comparative Example, it was found that it was difficult to deform and was easy to use.
Furthermore, since the thermal conductivity of Examples 1 and 2 is extremely smaller than that of Comparative Example, it was found that Examples 1 and 2 have better heat insulating properties than Comparative Example.

Although the surface hardness and screw penetration of Examples 1 and 2 are smaller than those of the Comparative Examples, generally, if the surface hardness is 150 (kgf), dents or the like are less likely to occur and there is no problem in practical use. .. Further, the screw penetration force is required to be 2.5 times or more the weight of the inorganic building board, but since the inorganic building board according to the present invention itself is lightweight, there is no practical problem in this respect as well. Therefore, it was found that the inorganic building board according to the present application is about 40% lighter than the commercially available gypsum board, and can be used in the same manner as the commercially available gypsum board.

[0025]

As is apparent from the above description, according to the present invention, a plate-like core material mainly composed of an inorganic foam and a fibrous material and having a specific gravity of 0.4 or less is formed by adding a binder. The front and back surfaces of the light plate-shaped core material are composed of mineral fibers and inorganic powders, and are covered with an outer layer portion having a specific gravity of 0.7 or more formed by adding a binder. Will be covered with a hard and dense outer layer. Therefore, according to the present invention, it is possible to obtain an inorganic building board having a surface that is hard, can be screwed, has a large bending strength, and has a low thermal conductivity, which is a performance required for a base material. Moreover, since the overall specific gravity is 0.55 or less, it is lighter than the gypsum board, and has the effect of facilitating transportation and handling.

[Brief description of drawings]

FIG. 1 is a graph showing a correlation between specific gravity and surface hardness of an outer layer portion according to this example.

FIG. 2 is a graph showing a correlation between specific gravity and bending strength of an outer layer portion according to this example.

[Procedure amendment]

[Submission date] October 30, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] Inorganic building board

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic building board used as a wall base material or the like.

[0002]

2. Description of the Related Art Generally,
Inorganic building boards used as wall base materials, etc. are required to have predetermined strength, surface hardness, thermal conductivity, etc. from the viewpoint of use, and are lightweight and have a predetermined overall hardness from the viewpoint of construction. However, it is required that it can be screwed. Therefore, gypsum board is widely used as a wall base material as compared with the conventional example.

However, in recent years, there has been a demand for a base material which is lighter than gypsum board and which meets the fire protection regulations due to the aging of construction workers and the congestion of city traffic. Therefore, in order to reduce the weight of the gypsum board, it has been considered to generate bubbles inside the gypsum board or to mix an inorganic foam, but this method has a problem that the strength of the gypsum board decreases. .. On the other hand, in order to reduce the weight and maintain the strength at the same time, it is conceivable to mix an organic fiber such as pulp into the gypsum board, but this method has a problem that the fireproof property is impaired.

In view of the above problems, it is an object of the present invention to provide a lightweight inorganic building board having sufficient performance as a base material.

[0005]

Means for Solving the Problems The present inventor has a three-layer structure by differentiating the composition of the plate-shaped core material and the outer layer portions provided on the front and back surfaces thereof, and thus is lighter than the gypsum board,
Moreover, they have found that an inorganic building board having sufficient performance as a base material can be obtained, and have completed the present invention. In order to achieve the above-mentioned object, the gist of the present invention is to mainly use an inorganic foam, and to add a proper amount of a fibrous material and a binder to the surface of a plate-like core material having a specific gravity of 0.4 or less, a mineral. The inorganic building board is characterized in that it has an outer layer portion having a specific gravity of 0.7 or more formed by adding a binder and mainly composed of high-quality fibers and an inorganic powder, so that the overall specific gravity is 0.55 or less.

The inorganic foamed material forming the plate-shaped core material is for reducing the weight while maintaining the compressive strength.
There are pearlite, shirasu foam, silica flour, glass foam, etc. These can be used alone or in combination of two or more kinds. The composition ratio of the inorganic foam in the plate-shaped core material is preferably 50 to 90% by weight. When it is 50% by weight or less, the ratio of the fibrous substance added to form the plate-shaped core material relatively increases and the strength is improved, but the effect of lowering the specific gravity cannot be obtained. 9
This is because if it is 0% by weight or more, it becomes difficult to uniformly make paper together with the fibrous material.

The fibrous material added to the plate-shaped core material is for connecting the inorganic foams to each other, and examples thereof include rock wool, slag wool, pulp and polypropylene fiber. Alone or
Two or more kinds can be used in combination. The fibrous material is for connecting the inorganic foams to form a plate shape, and is added in an amount of at least 3% by weight, but if it is too much, the amount of the inorganic foams will relatively decrease and the weight reduction will be achieved. The purpose cannot be achieved.

The binder added to the plate-shaped core material is for connecting and integrating the inorganic foam and the fibrous material. For example, a synthetic resin such as polyvinyl alcohol resin or phenol resin, or starch. These may be used alone or in combination of two or more.

Generally, the more the binder and the organic fibers are, the more the bending strength is improved. Therefore, it is effective from the viewpoint of strength to mix the organic fibers such as pulp into the plate-shaped core material in terms of strength. It is effective in terms of aspects. Furthermore, the use of fusible fibers that also serve as fibrous substances and binders is also effective in improving strength and the like. However, in order to obtain an inorganic building board as a semi-incombustible material, it is necessary that the total amount of organic components in the plate-shaped core material is 15% by weight or less including the binder. Further, in order to obtain an inorganic building board as a non-combustible material, the total amount of organic components needs to be 7% by weight or less, so that it is preferable to employ mineral fibers as the fibrous material.

The reason why the specific gravity of the plate-shaped core material is 0.4 or less is that
This is because if the specific gravity is 0.4 or more, it becomes difficult to reduce the weight of the inorganic building board. Since the plate-shaped core material forms an intermediate layer of the inorganic building board, increasing the thickness of the plate-shaped core material has an advantage that the bending moment that the inorganic building board can withstand becomes large.

The mineral fibers forming the outer layer include, for example, rock wool, slag wool, mineral wool,
Glass fiber etc. can be mentioned, these are alone,
Alternatively, two or more kinds can be used in combination. And
The composition ratio of the mineral fiber in the outer layer is 20 to 60% by weight.
Is preferred. When the content is 20% by weight or less, the bending strength is low and the surface is easily broken during screw driving,
This is because if it is 60% by weight or more, the amount of the inorganic powder to be added becomes low, and the surface hardness and overall hardness cannot be increased.

The inorganic powdery material forming the outer layer portion is for increasing hardness and screwing performance while maintaining fire resistance. Examples include calcium carbonate, silica sand, microsilica, slag, and aluminum hydroxide. Etc. can be mentioned. Then, the composition ratio of the inorganic powder in the outer layer portion,
It is preferably 40 to 70% by weight. This is because if the amount is less than 40% by weight, the desired surface hardness cannot be obtained.
This is because when the content is 0% by weight or more, the ratio of the mineral fiber is relatively reduced, and the desired strength cannot be obtained. Further, the strength of the outer layer portion is highest when the inorganic powder having a particle size of about 150 μ is used, but the inorganic powder has an average particle size of 40 μ.
˜300 μ may be used.

The specific gravity of the outer layer portion is set to 0.7 or more for the following reason. That is, when the proportion of the inorganic powder is constant, for example, 60% by weight, and the composition of the other material is made different to form the outer layer portion, the specific gravity and surface hardness of the outer layer portion, and the specific gravity and bending strength are There is a correlation between them, and the surface hardness and bending strength increase as the specific gravity increases (FIGS. 1 and 2). Then, in practical use, in order to obtain the outer layer portion having substantially the same surface hardness and bending strength as the gypsum board, the specific gravity of the outer layer portion needs to be 0.7 or more.

The material of the binder added to the outer layer,
The addition amount is the same as in the case of the above-mentioned plate-shaped core material, and thus the description thereof is omitted.

As described above, the more the binder and the organic fibers are, the more the bending strength is improved. Therefore, organic fibers such as pulp may be used in the outer layer portion instead of the mineral fibers. However, to obtain an inorganic building board as a semi-combustible material,
The total amount of organic components needs to be 15% by weight or less. Therefore, when organic fibers such as pulp are used instead of mineral fibers, it is necessary to consider that the total amount of organic components such as binder is within the above range. Further, in order to obtain an inorganic building board as a non-combustible material, it is necessary to set the total amount of organic components to 7% by weight or less, like the above-mentioned plate-shaped core material.

Next, a method for manufacturing an inorganic building board according to this embodiment will be described. For example, an inorganic foam, a fibrous substance, and a binder are suspended in water to obtain an aqueous slurry, which is wet-processed to obtain a wet mat to be a plate-shaped core material, while a mineral fiber, an inorganic powdery substance are obtained. , A binder is suspended in water to obtain an aqueous slurry, which is wet-processed to obtain a wet mat to be an outer layer part, and then the wet mat to be an outer layer part is formed on the front and back surfaces of the wet mat to be a plate-shaped core material. After the mats are laminated and pressed, they are dried and integrated,
There is a method of manufacturing an inorganic building board.

In the above-mentioned manufacturing method, the case where the wet mats are laminated and integrated has been described, but an existing manufacturing method such as a dry method or a combination of dry and wet methods can be selected.

[0018]

EXAMPLES Examples according to the present invention will be described below. (Example 1) Unit volume mass of 0.08 as an inorganic foam
(Kg / l) 82% by weight of perlite, 10% by weight of pulp as a fibrous material, phenol resin and starch as a binder at a total ratio of 8% by weight were added and suspended in water to obtain an aqueous slurry. While making a sheet-like core material with a thickness of 11 mm and a specific gravity of 0.15 by papermaking, 27% by weight of rock wool as mineral fiber, 60% by weight of calcium carbonate as inorganic powder, and phenol resin and starch as binder are combined. 8% by weight and 5% by weight of pulp as a reinforcing material, and then mixed in water to obtain an aqueous slurry,
After this was made into a paper to obtain an outer layer portion having a thickness of 2.0 mm and a specific gravity of 0.6, the outer layer portion was laminated on the front and back surfaces of the plate-shaped core material and integrated by pressing with a press to form a plate-shaped body. , Dried to a thickness of 9m
A sample having m and an overall specific gravity of 0.45 was obtained. The calcium carbonate used had a particle size of 50 mesh, and the perlite used had an average particle size of 300 μm.

Example 2 80% by weight of perlite having a unit volume mass of 0.08 (kg / l) as an inorganic foam, 13% by weight of rock wool as a fibrous substance, and a total of 7% phenol resin and starch as a binder. An aqueous slurry is obtained by kneading the mixture in a weight% ratio, and this is made into paper and has a thickness of 11 m.
m, a specific gravity of 0.15 while obtaining a plate-shaped core material having a mineral fiber content of 36% by weight of rockwool, an inorganic powder form of 57% by weight of calcium carbonate, and a binder of 7% by weight of phenol resin and starch. Aqueous slurry is obtained by kneading at a ratio, and this is made into paper and has a thickness of 2.0 mm and a specific gravity of 0.6.
After obtaining the outer layer part, the outer layer part is laminated on the front and back surfaces of the plate-shaped core material, and pressed and integrated with a press to form a plate-like body, which is dried to have a thickness of 9 mm and an overall specific gravity of 0.45. I got a board.
The calcium carbonate used had a particle size of 50 mesh, and pearlite had an average particle size of 300 μm.
I used the one.

Comparative Example A commercially available gypsum board having a thickness of 9 mm and a specific gravity of 0.74 was used as a sample.

The measurement results regarding the physical properties of the samples obtained in Examples 1 and 2 and Comparative Example are shown below. Example 1 Example 2 Comparative example Thickness (mm) 9.0 9.0 9.0 Specific gravity 0.45 0.45 0.74 Bending strength (kgf / cm ² ) 75 70 50 Surface hardness (kgf) 170 160 220 Screw penetration force (kgf) 18 20 27 Thermal conductivity (kal / mh ℃) 0.06 0.06 0.27 Fire resistance Quasi-non-combustible pass Non-flammable pass Quasi-non-flammable pass

The measurement results are obtained based on the following method. Bending strength: Based on JIS 5907-1977. Surface hardness: Based on JIS HARDNESS TESTER. Screw penetration force: Based on the test method according to JIS A5910. Thermal conductivity: Based on JIS A1412. Fire resistance: Based on JIS A1321.

As is clear from the above measurement results, the specific gravity of Examples 1 and 2 is smaller than that of Comparative Example by 25 to 40%.
The 40% smaller specific gravity means that when the standard size gypsum board has a weight of about 11 kg, the inorganic building board of the present invention having the same size has a weight of about 6.7 kg. Therefore, in the case of the gypsum board, even if only about half of the loadable volume of a truck or the like can be used due to weight limitation, the inorganic building board of the present invention can be loaded to the full loadable volume of a truck or the like. As a result, not only can physical distribution costs be greatly reduced, but also manual transportation and handling to the construction site becomes easy. In addition, Example 1,
Since the bending strength of No. 2 was about 40% higher than that of Comparative Example, it was found that it was difficult to deform and was easy to use.
Furthermore, since the thermal conductivity of Examples 1 and 2 is extremely smaller than that of Comparative Example, it was found that Examples 1 and 2 have better heat insulating properties than Comparative Example.

Although the surface hardness and screw penetration of Examples 1 and 2 are smaller than those of the Comparative Examples, generally, if the surface hardness is 150 (kgf), dents or the like are less likely to occur and there is no problem in practical use. .. Further, the screw penetration force is required to be 2.5 times or more the weight of the inorganic building board, but since the inorganic building board according to the present invention itself is lightweight, there is no practical problem in this respect as well. Therefore, it was found that the inorganic building board according to the present application is about 40% lighter than the commercially available gypsum board, and can be used in the same manner as the commercially available gypsum board.

[0025]

As is apparent from the above description, according to the present invention, a plate-like core mainly composed of an inorganic foam and having a specific gravity of 0.4 or less formed by adding an appropriate amount of fibrous material and a binder. The front and back surfaces of the material are mainly composed of mineral fibers and inorganic powder,
Since the outer layer portion having a specific gravity of 0.7 or more formed by adding the binder is covered, the front and back surfaces of the light plate-shaped core material are covered with the hard and dense outer layer portion. Therefore, according to the present invention, the surface is hard, can be screwed and has a large bending strength,
It is possible to obtain an inorganic building board having the performance required for a base material that has a low thermal conductivity. Moreover, since the overall specific gravity is 0.55 or less, it is lighter than the gypsum board, and has the effect of facilitating transportation and handling.

[Brief description of drawings]

FIG. 1 is a graph showing a correlation between specific gravity and surface hardness of an outer layer portion according to this example.

FIG. 2 is a graph showing a correlation between specific gravity and bending strength of an outer layer portion according to this example.

Claims (1)

Claim: What is claimed is: 1. A mineral material and a fibrous material as main components, and a mineral fiber on the front and back surfaces of a plate-like core material formed by adding a binder and having a specific gravity of 0.4 or less. An inorganic building board comprising an inorganic powder material as a main component, and an outer layer portion having a specific gravity of 0.7 or more formed by adding a binder so as to have an overall specific gravity of 0.55 or less.