Calcium silicate molded body and method for producing the same

Abstract

To provide a calcium silicate molded body having a crystalline silica content of less than 0.10 mass% while maintaining desired physical properties without increasing the production cost.SOLUTION: The present invention provides a calcium silicate molded body and a method for producing the same. The calcium silicate molded body comprises 35.0-62.0 mass% of a calcium silicate matrix, 10.0-40.0 mass% of gypsum, and 3.0-10.0 mass% of a fiber raw material. The content of crystalline silica is less than 0.10 mass%, the bulk density is 0.70 g / cm3 or more and less than 1.20 g / cm3, the bending strength is 10.0 N / mm2 or more, and the length change rate is 0.15% or less. A raw material of the calcium silicate matrix comprises 9.5-30.0 mass% of amorphous silica and 0.3-7.5 mass% of crystalline silica. The mass ratio of the amorphous silica to the crystalline silica is 97:3-70:30 in the calcium silicate matrix raw material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a calcium silicate molded body and a method for manufacturing the same, and more specifically, to a calcium silicate molded body in which the content of crystalline silica is reduced while maintaining the physical properties of a conventional calcium silicate molded body, and a method for manufacturing the same.

Background Art

[0002] Calcium silicate molded bodies are lightweight and excellent in dimensional stability and strength. Calcium silicate molded bodies formed into plates (also referred to as calcium silicate plates) are widely used in construction materials, members of automobiles or aircraft, parts of industrial plant equipment, and the like. Conventionally, silica containing crystalline silica has been used as a siliceous raw material for calcium silicate molded bodies. Therefore, a certain amount of crystalline silica derived from raw materials such as silica is contained in the calcium silicate molded body.

[0003] In the GHS, which is an international classification standard, crystalline silica falls under the carcinogenic category of Category 1A (chemical substances known to be carcinogenic to humans), and furthermore, the Ministry of Health, Labour and Welfare has defined it as a "carcinogenic substance that requires the preservation of work records, etc. for 30 years based on the Labour Safety Standards and Health Regulations". Therefore, in products using calcium silicate molded bodies, it is necessary to minimize the content of crystalline silica.

[0004] On the other hand, when preparing a calcium silicate molded body, not using a raw material containing crystalline silica is one countermeasure, but there have been cases where the manufacturing cost increases and desired physical properties such as the required strength and dimensional stability of the calcium silicate molded body cannot be obtained.

[0005] The inventors of the present invention invented a method for producing a calcium silicate molded body by using calcium silicate hydrate obtained by reacting a calcareous raw material and a siliceous raw material under a saturated water vapor pressure as a matrix, a matrix raw material containing a specific amount of pre-synthesized tobermorite slurry, a fiber raw material, wollastonite, and dihydrate gypsum, adding these to water and mixing, molding this mixture, and subjecting it to autoclave curing to harden it (Patent Document 1). However, in Patent Document 1, the crystalline silica content in the obtained calcium silicate molded body is not sufficiently considered.

[0006] In addition, a method for producing calcium silicate with a reduced crystalline silica content is disclosed (Patent Document 2). However, no consideration has been given to any desired physical properties of the calcium silicate molded body (plate).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the conventional technology for producing a calcium silicate molded body as described in Patent Document 1 above, when the crystalline silica content is less than 0.10% by mass, there are problems that the desired physical properties, particularly the flexural strength, become small and the length change rate becomes large.

Means for Solving the Problems

[0009] Here, without increasing the manufacturing cost and while maintaining the desired physical properties, an object is to provide a calcium silicate molded body having a crystalline silica content of less than 0.10% by mass. As a result of intensive studies, the content and ratio of amorphous silica and crystalline silica in the raw materials constituting the calcium silicate matrix were adjusted, and depending on the Blaine specific surface area of the amorphous silica, the Ca / (Al + Si) molar ratio in the raw materials of the calcium silicate matrix was adjusted to a specific value, and it was found that a desired calcium silicate molded body can be obtained.

[0010] That is, as a first aspect of the calcium silicate molded body according to the present invention, it is the calcium silicate molded body shown below. [1] It contains 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and the content of crystalline silica is less than 0.10% by mass. Bulk density 0.70 g / cm 3 or more, 1.20 g / cm 3 less than Bending strength 10.0 N / mm 2 or more, Length change rate 0.15% or less, which is a calcium silicate molded body, The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:30. When the raw material of the calcium silicate matrix contains amorphous silica having a Blaine specific surface area of 400 cm 2 / g or more and less than 2,000 cm 2 / g, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 0.60 or more and less than 1.0, which is a calcium silicate molded body.

[0011] The second aspect of the calcium silicate molded body of the present invention is that when the value of the Blaine specific surface area as a raw material for preparing the calcium silicate matrix is 2,000 cm 2 / g or more and less than 5,000 cm 2 / g of amorphous silica is included, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.00 or more and less than 1.20, and other points are the same as those of the first aspect. It is a calcium silicate molded body.

[0012] The third aspect of the calcium silicate molded body of the present invention is that when the value of the Blaine specific surface area as a raw material for preparing the calcium silicate matrix is 5,000 cm 2 / g or more and less than 15,000 cm 2 / g of amorphous silica is included, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.20 or more and less than 1.45, and other points are the same as those of the first aspect. It is a calcium silicate molded body.

[0013] The fourth aspect of the calcium silicate molded body of the present invention is that when the value of the Blaine specific surface area as a raw material for preparing the calcium silicate matrix is 15,000 cm 2 / g or more of amorphous silica is included, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.45 or more and less than 1.80, and other points are the same as those of the first aspect. It is a calcium silicate molded body.

[0014] The calcium silicate molded bodies of the first to fourth aspects described above can contain 50.0% by mass or less of a filler.

[0015] Furthermore, the present invention provides a method for manufacturing a calcium silicate molded body, and its first aspect is as follows. [2] A method for producing a calcium silicate molded body containing less than 0.10% by mass of crystalline silica, which comprises using a calcium silicate hydrate obtained by reacting a calcareous raw material and a siliceous raw material under a saturated steam pressure as a calcium silicate matrix, further adding a previously synthesized tobermorite slurry as a solid content in an amount of 1.0% by mass or more and 16.0% by mass or less, adding 35.0% by mass or more and 62.0% by mass or less of a raw material of the calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material based on the total solid content, and including the following steps (1) to (3): The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:30. When the raw material of the calcium silicate matrix contains amorphous silica having a Blaine specific surface area of 400 cm 2 / g or more and less than 2,000 cm 2 / g, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 0.60 or more and less than 1.00. A method for producing a calcium silicate molded body. (1) A step of adding a calcium silicate matrix raw material, gypsum, and a fiber raw material to water (2) A step of molding the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body (3) A step of subjecting the uncured molded body to autoclave treatment at 150°C or higher and 220°C or lower for 2 hours or more and 20 hours or less to cure the uncured molded body

[0016] A second aspect of the method for producing a calcium silicate molded body of the present invention is that the raw material of the calcium silicate matrix has a Blaine specific surface area of 2,000 cm 2 / g or more and 5,000 cm 2When it contains amorphous silica of less than / g, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.00 or more and less than 1.20, and the other aspects are the same as those in the first aspect. This is a method for manufacturing a calcium silicate molded body.

[0017] The third aspect of the method for manufacturing a calcium silicate molded body of the present invention is that when the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 5,000 cm 2 / g or more and less than 15,000 cm 2 / g, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.20 or more and less than 1.45, and other points are the same as those in the first aspect. This is a method for manufacturing a calcium silicate molded body.

[0018] The fourth aspect of the method for manufacturing a calcium silicate molded body of the present invention is that when the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 15,000 cm 2 / g or more, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.45 or more and less than 1.80, and other points are the same as those in the first aspect. This is a method for manufacturing a calcium silicate molded body.

[0019] Furthermore, in step (1) of the method for manufacturing a calcium silicate molded body of the present invention, a filler of 50.0 mass% or less may be added.

Advantages of the Invention

[0020] According to the present invention, it is possible to provide a calcium silicate molded body having a crystalline silica content suppressed to less than 0.10 mass% and having desired physical properties (bulk density, flexural strength, length change rate) and a method for manufacturing the same. Also, even when using amorphous silica such as glass powder, it is possible to provide a calcium silicate molded body that meets the standards of JIS A 5430.

Modes for Carrying Out the Invention

[0021] The calcium silicate molded body of the present invention contains 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material. In addition, the above contents represent the contents of the respective components with respect to the mass of the total solid content of the calcium silicate molded body. Also, unless otherwise specified, the contents described below indicate the ratio with respect to the mass of the total solid content of the calcium silicate molded body.

[0022] (1) Calcium silicate matrix The calcium silicate matrix here is a calcium silicate hydrate obtained by reacting a calcareous raw material and a silicic acid raw material under saturated steam pressure. The raw materials forming this calcium silicate matrix include a calcareous raw material, a siliceous raw material, and a pre-synthesized tobermorite slurry (hereinafter referred to as "synthetic tobermorite").

[0023] Synthetic tobermorite is a raw material used to improve the moldability in the manufacturing process of the calcium silicate molded body or to obtain desired physical properties such as the length change rate of the calcium silicate molded body.

[0024] Synthetic tobermorite can be produced by mixing a calcareous raw material and a siliceous raw material with water and performing hydrothermal synthesis under high temperature and high pressure. As the calcareous raw material, quicklime, slaked lime, etc. can be used, and as the siliceous raw material, silica, diatomaceous earth, microsilica, silica fume, etc. can be used, but in particular, silica is preferable.

[0025] The synthesis of tobermorite can be carried out, for example, as follows. A calcareous raw material and a siliceous raw material are blended so that the CaO / SiO2 molar ratio is 0.3 or more and 1.2 or less. To this blend, water is added in a mass ratio of 5 times or more and 20 times or less, preferably 7 times or more and 16 times or less, and mixed and dispersed to form a raw material slurry. The raw material slurry is subjected to hydrothermal synthesis at a temperature of 150°C or more and 210°C or less for 1 hour or more and 12 hours or less in a pressure vessel capable of stirring. In this way, slurry-like synthetic tobermorite can be obtained. The synthetic tobermorite can be used as a raw material for a calcium silicate matrix in the form of a slurry. The average particle diameter of the synthetic tobermorite is preferably in the range of 30 μm to 110 μm, more preferably 50 μm to 105 μm.

[0026] The blending ratio of the synthetic tobermorite is 1.0% by mass or more and 16.0% by mass or less, preferably 2.0% by mass or more and 13.0% by mass or less, more preferably 4.0% by mass or more and 11.0% by mass or less, based on the total solid content of the calcium silicate molded body. Here, if the blending ratio of the synthetic tobermorite is less than 1.0% by mass as a solid content, it is not preferable because there will be a problem with the shape retention after molding. Also, if the blending ratio exceeds 16.0% by mass as a solid content, the bulk density becomes low and the strength decreases, which is not preferable.

[0027] As the calcareous raw material for preparing the calcium silicate matrix, the raw materials conventionally used for manufacturing the calcium silicate molded body can be used. For example, quicklime, slaked lime, etc. can be used. The blending ratio of the calcareous raw material is preferably 5.0% by mass or more and 25.0% by mass or less, more preferably 7.0% by mass or more and 22.0% by mass or less, based on the total solid content of the calcium silicate molded body of the present invention.

[0028] Portland cement can be used as a raw material for preparing the calcium silicate matrix. The mixing ratio of Portland cement is preferably 5.0% by mass or more and 20.0% by mass or less, more preferably 7.0% by mass or more and 15.0% by mass or less, based on the total solid content of the calcium silicate molded body of the present invention.

[0029] As a siliceous raw material for preparing the calcium silicate matrix, crystalline silica such as silica sand and silica stone can be used, and silica stone is preferably used. Here, when crystalline silica such as silica stone is used as a raw material for the above synthetic tobermorite, a part remains unreacted and exists as crystalline silica. Therefore, when crystalline silica is used in addition to the preparation of synthetic tobermorite to prepare the calcium silicate matrix, the total amount of the crystalline silica and the unreacted crystalline silica remaining in the synthetic tobermorite needs to be 0.3% by mass or more and 7.5% by mass or less, preferably 0.5% by mass or more and 7.0% by mass or less, more preferably 1.0% by mass or more and 6.5% by mass or less, based on the total solid content of the calcium silicate molded body. When the total amount of the crystalline silica is less than 0.3% by mass, the length change rate becomes large, which is not preferable. When it exceeds 7.5% by mass, the content of crystalline silica in the calcium silicate molded body becomes 0.10% by mass or more.

[0030] As a siliceous raw material for preparing the calcium silicate matrix, amorphous silica such as glass powder, silica fume, diatomaceous earth, and fly ash can be used, glass powder and silica fume are preferable, and glass powder is more preferable.

[0031] Except for the amorphous silica used in the synthesis of synthetic tobermorite, the blending ratio of amorphous silica as a raw material for preparing the calcium silicate matrix is 9.5% by mass or more and 30.0% by mass or less, preferably 10.0% by mass or more and 25.0% by mass or less, and more preferably 11.0% by mass or more and 20.0% by mass or less, based on the total solid content of the calcium silicate molded body.

[0032] The mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material needs to be 97:3 to 70:30, preferably 90:10 to 70:30, and more preferably 85:15 to 70:30. When the mass ratio of crystalline silica is higher than this range, it becomes difficult to make the content of crystalline silica remaining in the calcium silicate molded body less than 0.10% by mass based on the total solid content of the calcium silicate molded body. Also, when the mass ratio of crystalline silica is smaller than this range, the calcium silicate molded body may have undesired physical properties, particularly a large length change rate, which is not preferable. For example, in the raw material of the calcium silicate matrix, the mass ratio of the total amount of amorphous silica (e.g., fumed silica, glass powder, etc.) as a siliceous raw material, unreacted crystalline silica in synthetic tobermorite, and crystalline silica (e.g., silica) as a siliceous raw material needs to be 97:3 to 70:30.

[0033] The amorphous silica used as a raw material for the calcium silicate matrix has a Blaine specific surface area of 400 cm 2 / g or more and 2,000 cm 2 / g or less, and the Ca / (Al + Si) molar ratio in the raw materials constituting the calcium silicate matrix needs to be 0.60 or more and less than 1.00. When the Ca / (Al + Si) molar ratio is less than 0.60, the length change rate may be large, and when it is greater than 1.00, sufficient bending strength may not be obtained. Also, when the Blaine specific surface area is 400 cm 2If it is less than / g, even if the Ca / (Al + Si) molar ratio is 0.60 or more, sufficient bending strength of the calcium silicate-based molded body may not be obtained. The value of the Blaine specific surface area is measured according to JIS R 5201 (Physical test methods for cement - 8.1 Specific surface area test).

[0034] The amorphous silica used as a raw material for the calcium silicate-based matrix has a Blaine specific surface area of 2,000 cm 2 / g or more and 5,000 cm 2 / g or less, and it is necessary that the Ca / (Al + Si) molar ratio in the raw materials constituting the calcium silicate-based matrix is 1.00 or more and less than 1.20. If the Ca / (Al + Si) molar ratio is less than 1.20, the length change rate may increase, and if it is more than 1.20, sufficient bending strength may not be obtained.

[0035] The amorphous silica used as a raw material for the calcium silicate-based matrix has a Blaine specific surface area of 5,000 cm 2 / g or more and 15,000 cm 2 / g or less, and it is necessary that the Ca / (Al + Si) molar ratio in the raw materials constituting the calcium silicate-based matrix is 1.20 or more and less than 1.45. If the Ca / (Al + Si) molar ratio is less than 1.20, the length change rate may increase, and if it is more than 1.45, sufficient bending strength may not be obtained.

[0036] The amorphous silica used as a raw material for the calcium silicate-based matrix has a Blaine specific surface area of 15,000 cm 2 / g or more, and it is necessary that the Ca / (Al + Si) molar ratio in the raw materials constituting the calcium silicate-based matrix is 1.45 or more and less than 1.80. If the Ca / (Al + Si) molar ratio is less than 1.45, the length change rate may increase, and if it is more than 1.80, sufficient bending strength may not be obtained.

[0037] In addition, when, for example, synthetic tobermorite, Portland cement, quicklime, silica, and amorphous silica are used as raw materials for the calcium silicate matrix of the calcium silicate molded body of the present invention, the above Ca / (Al + Si) molar ratio is a value obtained by calculating Ca, Al, and Si in a mixture in which all of these raw materials are combined.

[0038] The above calcium silicate matrix is mainly formed from synthetic tobermorite, siliceous raw materials, and calcareous raw materials, and the total of these three components is 35.0% by mass or more and 62.0% by mass or less, preferably 40.0% by mass or more and 60.0% by mass or less, and more preferably 43.0% by mass or more and 58.0% by mass or less with respect to the total solid content of the calcium silicate molded body of the present invention.

[0039] In addition, a fiber raw material and gypsum can be blended in the calcium silicate molded body of the present invention. The fiber raw material plays a role in improving physical properties such as the strength of the calcium silicate molded body and also serves as a molding aid. As the fiber raw material, for example, organic fibers such as pulp, and inorganic fibers such as carbon fibers and glass fibers can be used. The blending ratio of the fiber raw material is preferably in the range of 3.0% by mass to 10.0% by mass, more preferably 4.0% by mass to 9.0% by mass, and even more preferably 4.0% by mass to 8.0% by mass with respect to the total solid content of the calcium silicate molded body of the present invention, from the viewpoint of dispersibility during raw material mixing and surface characteristics of the calcium silicate molded body.

[0040] As the gypsum, anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, etc., for example, natural anhydrous gypsum, natural dihydrate gypsum, flue gas desulfurization gypsum, pulverized gypsum board powder, etc. can be used. The blending ratio of the gypsum is in the range of 10.0% by mass to 40.0% by mass, preferably 15.0% by mass to 40.0% by mass, more preferably 18.0% by mass to 35.0% by mass, and even more preferably 20.0% by mass to 30.0% by mass with respect to the total solid content of the calcium silicate molded body of the present invention.

[0041] A filler may be blended into the calcium silicate molded body of the present invention. As the filler, for example, one or more selected from the group consisting of mica powder, calcium carbonate powder, dolomite powder, pulverized powder (scrap) of waste calcium silicate plates, etc. can be used. The blending amount of the filler is preferably 50.0% by mass or less, more preferably 1.0% by mass to 30.0% by mass, and even more preferably 1.0% by mass to 25.0% by mass with respect to the total solid content of the calcium silicate molded body of the present invention.

[0042] The calcium silicate molded body of the present invention has desired physical properties while the content of crystalline silica is less than 0.10% by mass with respect to the total solid content. As the desired physical properties, specifically, the calcium silicate molded body of the present invention has a bulk density of 0.70 g / cm 3 or more and less than 1.20 g / cm 3 and a flexural strength of 10.0 N / mm 2 or more and a length change rate of 0.15% or less.

[0043] The calcium silicate molded body of the present invention can be produced by the following steps. (1) A step of adding a calcium silicate matrix raw material, gypsum, and a fiber raw material to water (2) A step of molding the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body (3) A step of subjecting the uncured molded body to autoclave treatment at 150°C or higher and 220°C or lower for 2 hours or more and 20 hours or less to cure the uncured molded body

[0044] The raw material of the calcium silicate matrix is, as described above, synthetic tobermorite, a siliceous raw material, and a calcareous raw material (Portland cement is included in the siliceous raw material and the calcareous raw material). In step (1), water is added to each of the above-described raw materials and uniformly mixed to obtain a raw material slurry, and in step (2), an uncured molded body can be obtained by molding this raw material slurry.

[0045] The compounding quantity of water added when mixing the raw materials varies depending on the molding method of the raw material slurry. For example, when using the extrusion molding method as the molding method, it is in the range of 20 to 50 parts by mass with respect to 100 parts by mass of the raw material solid content. When using the mold pressing method as the molding method, it is in the range of 500 to 1500 parts by mass. When using the papermaking method as the molding method, it is preferably in the range of 500 to 4000 parts by mass. As the molding method, known methods such as the extrusion molding method, the mold pressing method, and the papermaking method can be used as described above, but it is preferable to use the papermaking method.

[0046] In step (3), the obtained uncured molded body is hydrothermally cured, so that the cement, the calcareous raw material, the siliceous raw material, and the moisture react to form calcium silicate hydrate, and synthetic tobermorite is incorporated into a part of the matrix during the hydrothermal reaction, thereby forming a tobermorite-based matrix composed of tobermorite and calcium silicate hydrate with low crystallinity, and the uncured molded body is cured. The hydrothermal curing is carried out using an autoclave for a predetermined time under a saturated steam pressure at a predetermined temperature. The conditions are a saturated steam pressure of 150 to 200 °C for 2 to 20 hours. If the autoclave temperature is less than 150 °C, it will cause a decrease in strength. On the other hand, if it exceeds 220 °C, it will cause an increase in energy cost, which is not preferable. If the autoclave time is less than 2 hours, it will cause a decrease in strength. On the other hand, if it exceeds 15 hours, it will cause a decrease in production efficiency, which is not preferable.

[0047] The calcium silicate molded body of the present invention has desired physical properties while the content of crystalline silica is less than 0.10% by mass based on the total solid content.

Examples

[0048] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0049] The raw materials used in the examples and comparative examples are as follows: Synthetic tobermorite Quicklime (CaO content: 97.2 mass %), 33.3 mass %; silica powder (SiO2 content: 94.7 mass %, Al2O3 content: 1.6 mass %), 66.7 mass % (Ca / (Al + Si) molar ratio = 0.54), with a Blaine specific surface area of 10300 cm 2 1000 mass parts of water was added to 100 mass parts of a mixture consisting of 33.3 mass % quicklime (CaO content 97.2 mass %) and 66.7 mass % silica powder (SiO2 content 94.7 mass %, Al2O3 content 1.6 mass %) (Ca / (Al + Si) molar ratio = 0.54) with a Blaine specific surface area of 10300 cm / g, and the mixture was mixed and dispersed to obtain a raw material slurry. This raw material slurry was hydrothermally synthesized in an autoclave at 190 °C for 2 hours to obtain synthetic tobermorite (solid content: 10.5 mass %, average particle diameter: 104 μm, unreacted crystalline silica content: 17.5 mass %).

[0050] Amorphous silica A: Blaine specific surface area 400 cm 2 / g or more and less than 2,000 cm 2 / g A1: Glass powder, Blaine specific surface area 1,530 cm 2 / g A2: Glass powder, Blaine specific surface area 460 cm 2 / g A3: Glass powder, Blaine specific surface area 1,980 cm 2 / g A’: Glass powder, Blaine specific surface area 340 cm 2 / g

[0051] Amorphous silica B: Blaine specific surface area 2,000 cm 2 / g or more and less than 5,000 cm 2 / g B1: Fumed silica, Blaine specific surface area 3,700 cm 2 / g B2: Fumed silica, Blaine specific surface area 2,150 cm 2 / g B3: Fumed silica, Blaine specific surface area 4,700 cm 2 / g

[0052] Amorphous silica C: Blaine specific surface area 5,000 cm 2 / g or more and less than 15,000 cm 2 / g C1: Fumed silica, Blaine specific surface area 5,400 cm 2 / g C2: Silica fume, Brunauer specific surface area 7,800 cm 2 / g C3: Silica fume, Brunauer specific surface area 14,200 cm 2 / g

[0053] Amorphous silica D: Brunauer specific surface area 15,000 cm 2 / g or more D1: Silica fume, Brunauer specific surface area 22,000 cm 2 / g D2: Silica fume, Brunauer specific surface area 15,900 cm 2 / g

[0054] Portland cement: CaO content 65 mass%, SiO2 content 22 mass%, Al2O3 content 5 mass% Quicklime: CaO content 97.2 mass% Silica: Brunauer specific surface area 3700 cm 2 / g, SiO2 content 93.8 mass%, Al2O3 content 1.6 mass% Gypsum: Average particle diameter 54 μm Calcium carbonate: Brunauer specific surface area 5500 cm 2 / g Pulp: Canadian freeness 350 cc

[0055] Raw material blends were obtained at the blending ratios described in Tables 1 and 2 below. 1000 parts by mass of water was added to and mixed with 100 parts by mass of the solid content of the raw material blend to obtain a raw material slurry. Next, a green sheet with a width of 150 mm and a length of 200 mm was obtained by dewatering and pressing the raw material slurry in a table test simulating the papermaking method at a pressing pressure of 1.8 MPa. The obtained green sheet was held in an autoclave at 180 °C for 8 hours to obtain a calcium silicate board with a thickness of 10 mm. Various properties of the obtained calcium silicate board are also shown in Tables 1 and 2.

[0056]

Table 1

[0057]

Table 2

[0058] The content of crystalline silica in the synthetic tobermorite, calcium silicate compacts of the examples and comparative examples was measured as follows. The crystalline silica to be quantified is α-Quartz.

[0059] a. Preparation and pretreatment of samples It was carried out according to the following methods a-1 to a-4 in "10 Preparation of pulverized samples" in JIS A 1481-5 "Method for measuring asbestos content in building materials - Part 5: Quantitative analysis method for asbestos by X-ray diffraction method". a-1 Pulverization and sampling of the compact: According to "10.1 Preparation of pulverized samples". a-2 Carbonization treatment of organic matter in the sample: According to "10.2 Heat treatment of pulverized samples containing organic components". Let the weight loss rate at this time be r (%). a-3 Pretreatment: According to "10-3 Pretreatment for adjusting the residue sample". Let the sample weighing value at this time be M1 (mg). (According to (10-3 b)) a-4 Treatment when the residue rate exceeds 15% in the above 1-3: According to "10.4 Preparation of secondary residue samples".

[0060] b. Calculation of the content of crystalline silica Using the above samples, the content of crystalline silica was calculated as follows. b-1 Using the sample of a-3, X-ray diffraction analysis was performed under the X-ray diffraction conditions in the following table, and the integrated intensity near 26.6° of the α-Quartz (101) plane was determined. b-2 From the integrated intensity near 26.6°, the mass (M2 (mg)) of α-Quartz was determined using a previously prepared calibration curve, and the content was calculated by the following calculation formula.

[0061] · For the sample M3 (mg) before carbonization treatment calculated from the sample weighing value M1 M1 + M3 × r / 100 = M3 M3 = M1 / (1 - r / 100) · Regarding the crystalline silica content (mass %) Crystalline silica content = M2 / M3 × 100 = (M2 / (M1 / (1 - r / 100))) × 100 (mass %)

[0062]

Table 3

[0063] The bulk densities in Table 1 and Table 2 were measured by the JIS A5430 8.5 bulk density test (calcium silicate board (Type 2)). The flexural strength was measured by the three-point bending test method with a span of 15 cm and a crosshead speed of 1 mm / min for a calcium silicate board with a size of 150 mm × 200 mm after drying at 60°C for 24 hours. The rate of change in length was measured by the JIS A5430 8.7 test for the rate of change in length due to water absorption (calcium silicate board (Type 2)).

[0064] As can be seen from the results of the above examples and comparative examples, by adjusting the Ca / (Al + Si) molar ratio corresponding to the blending amount of crystalline silica, the blending ratio of crystalline silica and amorphous silica, and the Blaine specific surface area of amorphous silica as the siliceous raw material in the raw material of the calcium silicate molded body, it is possible to obtain a calcium silicate molded body in which the residual crystalline silica is less than 0.10 mass% while maintaining the desired physical properties.

Claims

1. Containing 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and having a crystalline silica content of less than 0.10% by mass, Bulk density of 0.70 g / cm ３ or more and ３ less than 1.20 g / cm Bending strength 10.0 N / mm ２ Above, a length change rate of 0.15% or less, which is a calcium silicate molded body, wherein the raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:30, When the raw material of the calcium silicate matrix has a specific surface area of 400 cm ２ / g or more and less than 2,000 cm ２ / g of amorphous silica, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 0.60 or more and less than 1.00, and the calcium silicate molded body.

2. Containing 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and having a crystalline silica content of less than 0.10% by mass, Bulk density of 0.70 g / cm ３ or more and ３ less than 1.20 g / cm Bending strength 10.0 N / mm ２ Above, a length change rate of 0.15% or less, which is a calcium silicate molded body, wherein the raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:30, When the raw material of the calcium silicate matrix has a specific surface area of the bran of 2,000 cm ２ / g or more and less than 5,000 cm ２ / g of amorphous silica, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.00 or more and less than 1.20, and the calcium silicate molded body.

3. Containing 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and having a crystalline silica content of less than 0.10% by mass, Bulk density of 0.70 g / cm ３ or more and 1.20 g / cm ３ less than Bending strength: 10.0 N / mm ２ Above, a length change rate of 0.15% or less, which is a calcium silicate molded body, wherein the raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:30, When the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 5,000 cm ２ / g or more and less than 15,000 cm ２ / g, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.20 or more and less than 1.45, and it is a calcium silicate molded body.

4. Containing 35.0% by mass or more and 62.0% by mass or less of a calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and having a crystalline silica content of less than 0.10% by mass, Bulk density of 0.70 g / cm ３ or more and 1.20 g / cm ３ less than Bending strength: 10.0 N / mm ２ Above, a length change rate of 0.15% or less, which is a calcium silicate molded body, The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:

30. When the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 15,000 cm ２ / g or more, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.45 or more and less than 1.80, and the calcium silicate molded body.

5. Furthermore, the calcium silicate molded body according to any one of claims 1 to 4, which further contains a filler in an amount of 50.0% by mass or less.

6. A method for producing a calcium silicate molded body containing less than 0.10.0% by mass of crystalline silica, which comprises using a calcium silicate hydrate obtained by reacting a calcareous raw material and a siliceous raw material under saturated steam pressure as a calcium silicate matrix, and further containing 1.0% by mass or more and 16.0% by mass or less of a pre-synthesized tobermorite slurry as a solid content, with respect to the total solid content, 35.0% by mass or more and 62.0% by mass or less of the raw material of the calcium silicate matrix, 10.0% by mass or more and 40.0% by mass or less of gypsum, and 3.0% by mass or more and 10.0% by mass or less of a fiber raw material, and including the following steps (1) to (3): The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:

30. When the raw material of the calcium silicate matrix has an amorphous silica with a Blaine specific surface area of 400 cm ２ / g or more and less than 2,000 cm ２ / g, the production method of the calcium silicate molded body, wherein the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 0.60 or more and less than 1.

00. (1) A step of adding the calcium silicate matrix raw material, gypsum and the fiber raw material to water. (2) A step of molding the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body. (3) A step of subjecting the uncured molded body to autoclave treatment at 150°C or higher and 220°C or lower for 2 hours or more and 20 hours or less to cure the uncured molded body.

7. A method for producing a calcium silicate molded body containing less than 0.10% by mass of crystalline silica, comprising the following steps (1) to (3), wherein a calcium silicate hydrate obtained by reacting a calcium carbonate raw material and a siliceous raw material under a saturated steam pressure is used as a calcium silicate matrix, and a previously synthesized tobermorite slurry is further contained as a solid content in an amount of 1.0% by mass or more and 16.0% by mass or less. The raw material of the calcium silicate matrix is used in an amount of 35.0% by mass or more and 62.0% by mass or less based on the total solid content, gypsum is used in an amount of 10.0% by mass or more and 40.0% by mass or less, and a fiber raw material is used in an amount of 3.0% by mass or more and 10.0% by mass or less. The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:

30. When the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 2,000 cm ２ / g or more and less than 5,000 cm ２ / g, the production method of the calcium silicate molded body is such that the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.00 or more and less than 1.

20. (1) A step of adding a calcium silicate matrix raw material, gypsum and a fiber raw material to water (2) A step of molding the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body (3) A step of subjecting the uncured molded body to autoclave treatment at 150 ° C or higher and 220 ° C or lower for 2 hours or more and 20 hours or less to cure the uncured molded body

8. A method for producing a calcium silicate molded body containing less than 0.10% by mass of crystalline silica, comprising the following steps (1) to (3), wherein a calcium silicate hydrate obtained by reacting a calcium carbonate raw material and a siliceous raw material under a saturated steam pressure is used as a calcium silicate matrix, and a previously synthesized tobermorite slurry is further contained as a solid content in an amount of 1.0% by mass or more and 16.0% by mass or less. The raw material of the calcium silicate matrix is used in an amount of 35.0% by mass or more and 62.0% by mass or less based on the total solid content, gypsum is used in an amount of 10.0% by mass or more and 40.0% by mass or less, and a fiber raw material is used in an amount of 3.0% by mass or more and 10.0% by mass or less. The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:

30. When the raw material of the calcium silicate matrix has an amorphous silica with a Blaine specific surface area of 5,000 cm ２ / g or more and less than 15,000 cm ２ / g, the production method of the calcium silicate molded body is such that the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.20 or more and less than 1.

45. (1) A step of adding a calcium silicate matrix raw material, gypsum and a fiber raw material to water Step (2): shaping the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body Step (3): subjecting the uncured molded body to autoclave treatment at 150°C or higher and 220°C or lower for 2 hours or longer and 20 hours or shorter to cure the uncured molded body

9. A method for producing a calcium silicate molded body containing less than 0.10% by mass of crystalline silica, comprising the following steps (1) to (3), wherein a calcium silicate hydrate obtained by reacting a calcareous raw material and a siliceous raw material under saturated steam pressure is used as a calcium silicate matrix, and a previously synthesized tobermorite slurry is further contained as a solid content in an amount of 1.0% by mass or more and 16.0% by mass or less. The raw material of the calcium silicate matrix is used in an amount of 35.0% by mass or more and 62.0% by mass or less based on the total solid content, gypsum in an amount of 10.0% by mass or more and 40.0% by mass or less, and a fiber raw material in an amount of 3.0% by mass or more and 10.0% by mass or less. The raw material of the calcium silicate matrix contains 9.5% by mass or more and 30.0% by mass or less of amorphous silica and 0.3% by mass or more and 7.5% by mass or less of crystalline silica, and the mass ratio of amorphous silica to crystalline silica in the calcium silicate matrix raw material is 97:3 to 70:

30. When the raw material of the calcium silicate matrix contains amorphous silica with a Blaine specific surface area of 15,000 cm ２ / g or more, the Ca / (Al + Si) molar ratio in the raw material of the calcium silicate matrix is 1.45 or more and less than 1.80, and a method for producing a calcium silicate molded body. Step (1): adding the calcium silicate matrix raw material, gypsum, and fiber raw material to water Step (2): shaping the mixture obtained in step (1) into a predetermined shape to obtain an uncured molded body Step (3): subjecting the uncured molded body to autoclave treatment at 150°C or higher and 220°C or lower for 2 hours or longer and 20 hours or shorter to cure the uncured molded body

10. Furthermore, in step (1), a filler is added in an amount of 50.0% by mass or less based on the total solid content of the calcium silicate molded body. The method for producing a calcium silicate molded body according to any one of claims 6 to 9.

Images