JPH10265258A - Method for producing hardened calcium silicate hydrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an energy-saving type cured product of a calcium silicate hydrate, in which many steps in a conventional production process are simplified. SOLUTION: A hardened calcium silicate hydrate is produced by hydrothermal hot pressing a powdery mixture of amorphous silicic acid to which NH ₄ ⁺ has been adsorbed and a calcium raw material selected from slaked lime, quicklime and calcined dolomite. Method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cured product of a calcium silicate hydrate, and more particularly, to a building material such as a heat insulating material, a fire-resistant coating material, a non-combustible building material, a humidity control material, and the like.
The present invention relates to a method for producing a porous calcium silicate-based hydrate which is useful as an odor carrier or a catalyst.

[0002]

2. Description of the Related Art Conventional autoclaved calcium silicate products as building materials include ALC (Autoclaved Ligh
t-weight Concrete), calcium silicate board (artificial wood), calcium silicate heat insulating material and the like. Each of these products is a porous body formed of an aggregate of calcium silicate hydrate generated by a hydrothermal reaction at 250 ° C or less,
The production process is complicated. For example, in the case of ALC, the raw material silica, quicklime, Portland cement, dihydrate gypsum, and metal aluminum are mixed with water to form a slurry, molded in a mold, and after demolding, autoclaved under a saturated vapor pressure of 180 ° C. It is obtained by performing for 5 to 10 hours.
In the case of calcium silicate plate and calcium silicate insulation,
In the static reaction method, water is mixed with a raw material of silicic acid, lime, and reinforcing fiber to form a slurry, and after molding, the molded body is cured by a hydrothermal reaction in an autoclave, and then the cured body is dried. To be obtained. In the dynamic reaction method, water is mixed with the raw material of silicic acid, lime, and reinforcing fiber to form a slurry, which is reacted in an autoclave. A molded article is obtained.

[0003] As described above, in the process of producing an autoclaved calcium silicate product, the steps of slurry treatment, autoclave treatment and drying treatment are indispensable, and since a large amount of water is used in these steps, a large amount of energy is consumed. There is a problem.

[0004]

Accordingly, the present invention simplifies conventional production processes such as slurry treatment, autoclave treatment, dehydration press treatment, drying treatment, etc., and consumes less energy. An object of the present invention is to provide a method for producing a cured hydrate.

[0005]

Under such circumstances, the present inventors have conducted intensive studies, and as a result, using amorphous silicic acid to which NH ₄ ⁺ has been adsorbed and slaked lime as raw materials, these powdery mixtures have been produced. By hydrothermal hot pressing, conventionally used slurry processing, autoclave processing, dehydration press,
The inventors have found that a calcium silicate-based hydrate can be produced by simplifying many steps such as a drying process, and have completed the present invention.

That is, the present invention is characterized by hydrothermal hot pressing a powdery mixture of amorphous silicic acid to which NH ₄ ⁺ is adsorbed and a calcium raw material selected from slaked lime, quicklime and calcined dolomite. It is intended to provide a method for producing a hardened calcium hydrate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the NH ₄ ⁺ -adsorbed amorphous silicic acid used as a raw material is NH ₄ ⁺
The adsorption amount 5 to 100 ppm, an average particle diameter of 10μm or less, BET specific surface area by nitrogen adsorption 1 m ² / g or more, moisture content of 30 wt%
More preferably, the content is at least 50% by weight. If the amount of NH ₄ ⁺ adsorbed by the amorphous silicic acid is less than 5 ppm, the progress of the reaction is poor, and if it exceeds 100 ppm, a large amount of ammonia is generated, which is not preferable because the working environment deteriorates. When the average particle size exceeds 10 μm, the difference in the progress of the reaction between the surface layer and the inside increases,
It is not preferable because the obtained cured product is separated into layers. If the BET specific surface area is less than 1 m ² / g, the progress of the reaction will be poor. The water content can be in the range of 30% by weight or more, but if it is close to this lower limit, it is necessary to increase the sealing performance during the reaction.

[0008] A preferred example of the amorphous silicic acid satisfying the above conditions is silica produced as a by-product in the cryolite manufacturing process. Further, even amorphous silica having no NH ₄ ⁺ adsorption such as diatomaceous earth, or amorphous silica having an insufficient amount of NH ₄ ⁺ adsorbed thereto, is equivalently wet-pulverized in an aqueous ammonium nitrate solution. Amorphous silicic acid to which NH ₄ ⁺ has been adsorbed can be obtained.

The calcium raw material used in the present invention can be selected from slaked lime, quick lime and calcined dolomite. Among them, slaked lime is preferable, and particularly those satisfying the quality of JIS R 9001 industrial slaked lime. preferable. When quick lime is used, soft calcination is preferred, and it is necessary to use more water during the reaction.

[0010] These raw materials are sufficiently pulverized and mixed to obtain Ca
/ Si molar ratio [(Ca + Mg) when calcined dolomite is used
/ Si molar ratio] is preferably 0.02 to 3.00, particularly 0.3 to 3.0. By subjecting this powdery mixture to a hydrothermal hot press, a cured product comprising a calcium silicate-based hydrate and unreacted starting materials is obtained. The conditions of the hydrothermal hot press are as follows: the reaction temperature is 100 ~ 300 ℃, especially 120
Preferably to 180 ° C., also pressing pressure 190kgf / cm ² or more,
The reaction time is preferably set so that the temperature of the center of the cured product reaches 100 ° C. or higher, particularly 120 ° C. or higher. If the reaction temperature is lower than 100 ° C., the strength of the cured product decreases, and even if it exceeds 300 ° C., the strength does not improve any more and reaches a plateau. If the pressing pressure is less than 190 kgf / cm ² , the strength of the cured product will be low.

[0011] The calcium silicate-based cured product obtained as described above is an aggregate of fine crystals, has excellent properties such as light weight, heat insulation and gas absorption / release properties, and has a heat insulating material, a fireproof coating material, In addition to building materials such as nonflammable building materials and humidity control materials, they are useful as odor carriers and catalysts. In addition, when calcined dolomite is used as a raw material, the strength of the obtained cured body is inferior to that of a case where lime is used, but since it has excellent gas adsorption properties, it is suitable as a humidity control material, an odor carrier, a catalyst, and the like. is there.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
In the following examples, the formation of calcium silicate was confirmed by 29Si-NMR.

Example 1 As a starting material, high-purity silicic acid by-produced in the cryolite manufacturing process (NH ₄ ⁺ adsorption amount 10 ppm, average particle size 1.0 μm, BET specific surface area by nitrogen adsorption 3 m ² / g, water content 50% by weight) and slaked lime (J
Using a commercial grade of reagent that satisfies the quality of industrial slaked lime of IS R 9001), the Ca / Si molar ratio was adjusted to 0.8, and the mixture was sufficiently mixed and subjected to hydrothermal hot pressing. The conditions of the hydrothermal hot pressing were a reaction temperature of 180 ° C., a pressing pressure of 3000 kgf / cm ² , and a reaction time of 20 minutes. As a result of qualitative analysis of the obtained cured product by X-ray diffraction, amorphous calcium silicate-based hydrate was observed in addition to unreacted starting materials.

Example 2 High-purity silicic acid and slaked lime by-produced in the cryolite production process used in Example 1 were used as starting materials, and the Ca / Si molar ratio was 0.0
The mixture was adjusted to 4, 0.81 and 1.62 and sufficiently mixed and subjected to a hydrothermal hot press. The conditions of the hydrothermal hot press are as follows: a press pressure of 1500 kgf / cm ² , a reaction time of 5 minutes, and a reaction temperature of 10 minutes.
Various changes were made to 0, 120, 140, 160, 180, and 200 ° C. FIG. 1 shows the compressive strength of the obtained cured product. FIG. 1 shows that the compressive strength can be increased by increasing the amount of slaked lime to be mixed and increasing the reaction temperature. Also,
At the reaction temperature of 100 to 120 ° C and 180 to 200 ° C, no increase in compressive strength is observed.

Example 3 High purity silicic acid and slaked lime by-product of the cryolite production process used in Example 1 used in Example 1 were used as starting materials, and the Ca / Si molar ratio was 0.8.
The resulting mixture was subjected to hydrothermal hot pressing. The conditions of the hydrothermal hot press were such that the reaction temperature was 200 ° C., the reaction time was 5 minutes, and the press pressure was variously changed from 190 to 3000 kgf / cm ² . FIG. 2 shows the compressive strength of the obtained cured product. FIG. 2 shows that the compressive strength of the cured body increases with an increase in the pressing pressure. The press pressure is 190kgf / cm ²
Below this, a cured product of calcium silicate hydrate was not obtained.

Example 4 As starting materials, diatomaceous earth was wet-pulverized with water (average particle size: 4 μm, BET specific surface area by nitrogen adsorption: 3 m ² / g, water content: 50% by weight), and diatomaceous earth in 10% by weight aqueous ammonium nitrate solution Using a wet crushed material (NH ₄ ⁺ adsorption 50 ppm, average particle diameter 4 μm, BET specific surface area by nitrogen adsorption 3 m ² / g or more, water content 50% by weight) and slaked lime used in Example 1, Ca / Si molar ratio is set to 0 to 0.5 for each diatomaceous earth.
The mixture was adjusted variously until the mixture was sufficiently mixed and subjected to a hydrothermal hot press. The condition of hydrothermal hot pressing is to set the reaction temperature to 18
0 ° C., press pressure 3000 kgf / cm ² , and reaction time 5 minutes.
FIG. 3 shows the compressive strength of the obtained cured product. From FIG. 3, it can be seen that the compressive strength increases with an increase in the amount of slaked lime mixed with any of the diatomaceous earths. However, when diatomaceous earth obtained by wet pulverization with water is used, defects such as cracking and cracking of the cured body are caused at the time of demolding after hydrothermal hot pressing. On the other hand, when diatomaceous earth was wet-pulverized with an aqueous solution of ammonium nitrate, the sample could be easily taken out, and no defects such as cracking and cracking were observed.

Example 5 High-purity silicic acid and quicklime produced as a starting material in the cryolite manufacturing process used in Example 1 (calcium carbonate, a special grade of calcium carbonate reagent for alkali analysis, was calcined at 1050 ° C. for 3 hours to obtain a particle size of 600 μm
Using the following adjustment) and Ca /
The Si molar ratio was adjusted to 0.04, 0.81 and 1.62, and the resulting mixture was subjected to hydrothermal hot pressing. The conditions of the hydrothermal hot press were a reaction temperature of 180 ° C., a reaction time of 5 minutes, and a press pressure of 1500 kgf / cm ² . As a result, even if the starting material is changed to quicklime, the reaction proceeds by hydrothermal hot pressing because the high-purity silicic acid by-produced in the cryolite manufacturing process has enough water necessary for digestion of quicklime, A cured product strength equivalent to that of Example 2 was obtained.

Example 6 High-purity silicic acid by-produced in the cryolite production process used in Example 1 as a starting material and calcined dolomite (dolomite was 1050)
(Calcination at 3 ° C. for 3 hours and the particle size adjusted to 600 μm or less), and the molar ratio of (Ca + Mg) / Si was determined in the same manner as in Example 2.
The mixture was adjusted to 0.04, 0.81 and 1.62 and sufficiently mixed, and subjected to a hydrothermal hot press. The conditions of the hydrothermal hot press are as follows: reaction temperature 180 ° C, reaction time 5 minutes, press pressure 1500k
gf / cm ² . As a result, even if the starting material is changed to calcined dolomite, the high-purity silicic acid by-produced in the cryolite manufacturing process has sufficient water required for digestion of calcined dolomite. Proceeded to obtain a cured product of calcium silicate hydrate containing magnesium silicate hydrate, and this cured product had a cured product strength equivalent to that of Example 2.

[0019]

The method for producing a cured product of a calcium silicate hydrate according to the present invention comprises a conventional production process, for example, crystallization and curing by a slurry treatment of a starting material, heat aging treatment, press dehydration treatment, and autoclave treatment. It is possible to simplify many steps for preparing a cured product such as drying of a molded product, and it is possible to reduce a large amount of energy consumption.
Therefore, it can be said that the method of the present invention is a method for producing an energy-saving cured product of a calcium silicate hydrate.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the Ca / Si molar ratio, the reaction temperature of hydrothermal hot pressing, and the compressive strength of a cured calcium silicate hydrate obtained in Example 2.

FIG. 2 is a view showing a relationship between a difference in press pressure of a hydrothermal hot press and a compressive strength of a cured product of a calcium silicate hydrate obtained in Example 3.

FIG. 3 is a graph showing the relationship between the difference in the treatment of the starting material of the calcium silicate-based hydrate obtained in Example 4 and the compressive strength.

Claims (5)

[Claims] 1. A calcium silicate-based water obtained by hydrothermal hot pressing a powdery mixture of amorphous silicic acid to which NH ₄ ⁺ is adsorbed and a calcium raw material selected from slaked lime, quick lime and calcined dolomite. A method for producing a cured Japanese product. 2. The amorphous silicic acid used has an NH ₄ ⁺ adsorption amount of 5 to 100 ppm, an average particle diameter of 10 μm or less, and BET by nitrogen adsorption.
A specific surface area of 1 m ² / g or more, a manufacturing method of the calcium silicate based hydrates cured product of claim 1, wherein those water content of 30 wt% or more. 3. The amorphous silicic acid used is obtained by wet-pulverizing amorphous silicic acid having an adsorption amount of NH ₄ ⁺ of 0 ppm or more and less than 5 ppm in an ammonium nitrate solution. Or a method for producing a cured product of a calcium silicate hydrate according to 2 above. 4. The method according to claim 1, wherein the molar ratio of Ca / Si or (Ca + Mg) / Si of the powdery mixture of the raw material amorphous silicic acid and the calcium raw material is 0.02 to 3.00. A method for producing a cured product of the above described calcium silicate hydrate. 5. The condition of hydrothermal hot pressing is a reaction temperature of 10
The pressure is 0 to 300 ° C. and the press pressure is 190 kgf / cm ² or more.
The method for producing a cured product of a calcium silicate hydrate according to any one of the above.