JPS6235989B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a lightweight calcium silicate molded body. As a carbon-containing calcium silicate molded body, Japanese Patent Publication No. 1983-6038 describes a method for producing a calcium silicate molded body containing activated carbon. This manufacturing method involves adding activated carbon in a specific amount of 0.5 to 7% by weight based on the solid content of the raw materials to a raw material slurry prepared from silicic acid raw materials, lime raw materials, and water, and causing a hydrothermal synthesis reaction with stirring to form zonotrite crystals and activated carbon. This method is used to form an aqueous slurry, which is formed and dried, and by adding a specific amount of activated carbon, the reaction rate of the above synthesis reaction can be increased and the amount of water can be significantly reduced. be. It is also described that the obtained carbon-containing zonotrite crystalline calcium silicate molded body has almost the same physical properties as a calcium silicate molded body that does not contain the carbon-containing zonotrite. That is, although conventional activated carbon-containing calcium silicate molded bodies have some effects in terms of their manufacturing process, it has been thought that the molded bodies themselves have almost no specific effects. On the other hand, the use of rice hull ash as a silicate raw material in producing calcium silicate molded bodies has recently been announced. This method uses rice husk ash, which is produced as a by-product when utilizing the combustion heat of rice husk, as a type of silicate raw material for producing calcium silicate molded bodies, and although there are cases in which calcium silicate molded bodies can be manufactured, The properties of the rice husk ash significantly affect the physical properties of the molded product obtained, and in extreme cases, a calcium silicate molded product cannot be obtained. This is thought to be caused by the fact that the burning conditions of rice husk and the properties of rice husk are not constant. The present inventors have been conducting research on calcium silicate molded bodies for many years, and in this research, when using charcoal as a silicate raw material for calcium silicate molded bodies, unlike rice husk ash, it was always found that An amorphous carbon-containing zonotritic calcium silicate molded product that can stably obtain a calcium silicate molded product (more specifically, a molded product mainly composed of zonotolite crystals and amorphous carbon) that has almost constant desired physical properties. The inventors discovered that the body is extremely lightweight, has sufficient strength for practical use, and has an extremely high adsorption capacity, especially moisture absorption capacity, and has completed the invention based on this finding. The present inventors further continued their research and found that when a carbon-containing calcium silicate molded body produced from the above-mentioned charcoal as a silicate raw material was fired to volatilize the carbon content,
It was discovered that it was possible to obtain a calcium silicate molded body that was made into activated carbon and had excellent mechanical strength.
We have finally completed the present invention. That is, in the present invention, a raw material slurry obtained by mixing a silicic acid raw material containing charcoal as a main component and a lime raw material with water such that the amount of water relative to the solid content is 5 times or more by weight is prepared by heating and stirring under pressure. Performing a hydrothermal synthesis reaction to obtain an aqueous slurry containing zonotrite crystals and amorphous carbon as main components, then molding and drying this to obtain a carbon-containing calcium silicate molded body, and firing the molded body obtained in a mold. The present invention relates to a method for producing a lightweight calcium silicate molded body, characterized by: The feature of the present invention is that by firing a calcium silicate molded body using Kuhn charcoal, the practical strength is sufficiently maintained.In particular, even when the above molded body containing about 30% by weight of carbon is fired, the practical strength is maintained. The carbon content is volatilized while the carbon content is sufficiently maintained, resulting in an extremely lightweight calcium silicate molded body. The amorphous carbon-containing calcium silicate molded body used as a raw material in the present invention contains 7.0 to 30% by weight of amorphous carbon, and it is particularly noteworthy that the amorphous carbon in the molded body is 7% by weight. If the temperature exceeds this value, the amount of moisture absorbed by the molded body itself increases rapidly. The present invention will be explained below based on its manufacturing method. In principle, the molded article of the present invention is produced by subjecting a raw material slurry prepared from charcoal as a silicic acid raw material, other ordinary silicic acid raw materials, lime raw materials, and water with stirring to a hydrothermal synthesis reaction with zonotrite crystals. It is produced by obtaining an aqueous slurry containing amorphous carbon as a main component, molding this, drying it to form an amorphous carbon-containing calcium silicate molded body, and firing this. Drying and firing at this time may be performed separately, or drying and firing may be performed simultaneously. The charcoal used in the present invention is produced by dry distilling rice husk, wheat husk, rice straw, wheat straw, wild grass, fallen leaves, etc., and usually has a particle size of 100 μm.
It is best to use it after crushing it to a size smaller than m. The chemical components include 30 to 80% by weight of SiO ₂ (hereinafter referred to as the same %), 20 to 50% of carbon, 0 to 10% of water, and about 0 to 10% of others. Particularly preferred examples of charcoal include rice husk charcoal and wheat husk charcoal. In the present invention, charcoal alone can be used as the silicic acid raw material, but if necessary, it can also be used in combination with other ordinary silicic acid raw materials. Even when used together, the main ingredient must be charcoal. As other silicic acid raw materials used at this time, any of those conventionally used for producing this type of calcium silicate molded body can be effectively used. For example, silica stone, silica sand, etc. can be used as crystalline silicic acid raw materials, and amorphous Examples of the silicic acid raw material include silica gel, silica flour, white carbon, and diatomaceous earth. As raw materials for lime, any of the conventionally used materials can be used, such as quicklime, slaked lime,
Carbide slag or the like can be used as a specific example, and especially when producing a lightweight molded product, for example, a molded product with a density of about 0.1 g/cm ³ , it is preferable to use milk of lime having a settling volume of 5 ml or more. The sedimentation volume of the milk of lime refers to the sedimentation volume of lime particles after 50 ml of milk of lime with a water to lime solids ratio of 120 times is left to stand for 20 minutes in a measuring cylinder with a diameter of 1.3 cm and a volume of 50 cm ^or more. The volume of sedimentation is shown in ml. The amount of water is at least 5 times (weight) the solid content of the raw material slurry, and when producing the above lightweight body,
It is preferable to make it 15 times or more. Silicic acid raw material (Kun charcoal, or this and other silicic acid raw materials) and lime raw material
The CaO/ _SiO2 molar ratio is about 0.90 to 1.15. Inactive additives may be added to this raw material slurry in the subsequent hydrothermal synthesis reaction, and inorganic fibers such as asbestos, rock wool, etc. can be exemplified as additives at this time. The raw material slurry thus prepared is then subjected to a hydrothermal synthesis reaction while being stirred. This reaction condition is usually carried out under a saturated steam pressure of 8 Kg/cm ² or more, preferably 10 Kg/cm ² or more. Through this reaction, the silicic acid content in the Kuhn charcoal reacts with lime, producing secondary particles of approximately 5 to 100 μm mainly composed of zonotrite crystals, and amorphous carbon from which the silicic acid content has been removed from the Kuhn charcoal fine particles. A slurry is obtained in which granules containing as a main component are uniformly dispersed in water. When this aqueous slurry mainly composed of zonotrite crystals and amorphous carbon particles is passed through a cloth, the liquid becomes transparent. When exposed to water, the liquid turns black. Based on this fact, in the present invention, it is considered that the above-mentioned amorphous carbon granules exist as being included in the secondary particles of the zonotrite crystal, or are attached to the particles by some force. It will be done. Various additives may be added to the aqueous slurry made of the zonotrite crystals and amorphous carbon as necessary. As additives in this case, a wide range of materials can be used that have been used in the production of this type of calcium silicate molded body, such as fibers, clays, cements, etc., and more specifically, asbestos, rock wool,
Specific examples include inorganic fibers such as glass fibers and carbon fibers, organic fibers such as pulp, cellulose, and various synthetic fibers, clays such as kaolin and bentonite, gypsum, Portland cement, alumina cement, and other various cements. In the present invention, an amorphous carbon-containing zonotrite crystal molded body can be obtained by molding and drying the aqueous slurry by a conventional method. The thus obtained amorphous carbon-containing zonotrite molded body is mainly composed of secondary particles of zonotrite crystals and amorphous carbon, and the content of amorphous carbon in the molded body is about 7.0 to 30% by weight. . This molded article has sufficient practical bending strength even though it is lightweight. What is particularly noteworthy is that the adsorption capacity is extremely large, and above all, the moisture absorption capacity is excellent. This hygroscopic ability has a close relationship with the amount of amorphous carbon contained, and according to the research of the present inventor, the content of amorphous carbon is
If the amount does not reach 7.0% by weight, the hygroscopicity does not increase, but if it exceeds 7.0% by weight, the hygroscopicity rapidly increases significantly. In addition, the specific surface area of the powder obtained by crushing the compact is about 80 to 200 m ² /g (measured by BET method), and the specific surface area of the powder obtained by pulverizing it is about 430 to 200 m An exothermic peak is seen between 480℃. Furthermore, the molded body is composed of secondary particles of calcium silicate crystals mainly composed of zonotrite crystals and amorphous carbon, or these and other additives, and the secondary particles are compressed and deformed to each other. It is configured by connecting. Moreover, among the molded bodies, high-density products are preferentially oriented. In the present invention, the thus obtained molded body is fired. This firing may be performed simultaneously with the drying, or may be performed separately. Firing is usually at an ambient temperature of 300-700℃, preferably 400-600℃
The heating is carried out at a temperature of approximately 0.degree. C., thereby essentially burning and volatilizing the amorphous carbon. Furthermore, energy can be saved by using the heat generated by combustion of amorphous carbon for drying and/or firing. The thus obtained molded article of the present invention is extremely lightweight, and yet maintains almost its practical strength. The method of the present invention will be specifically explained below with reference to Examples. However, parts and percentages in the following examples indicate parts by weight and percentages by weight, respectively, and various physical properties were measured by the following methods. (a) Bending strength According to the method of JIS A 9510. (b) Carbon content According to the method of JIS R 6124. Example 1 30.7 parts of quicklime (CaO95.0%) was added to 80°C warm water.
The sedimentation volume of the milk of lime, which was slaked in a vacuum chamber and dispersed in water using a homomixer, was 11.8 ml. The above milk of lime has a specific surface area of 165 m ² /g and an average particle size of 4 μm.
Rice husk charcoal powder (SiO ₂ 55.1%, C32.1%,
Add the slurry obtained by dispersing 56.8 parts (adsorbed moisture 9.8%) with 10 times the weight of water in a homomixer for 2 minutes, and then add more water and mix so that the total amount of water is 24 times the weight of the solid content. This was stirred in an autoclave at a saturated water vapor pressure of 12 Kg/cm ² and a temperature of 191°C with a stirring blade rotating at a rotation speed of 102 rpm, and a hydrothermal synthesis reaction was performed for 5 hours to obtain a slurry. Ta. When the slurry obtained above was dried at 100° C. for 24 hours and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. In addition, when this slurry was dried in the same manner as above and observed with a scanning electron microscope, the outer diameter was 5 to 5.
Spherical secondary particles of 100 μm were observed, and chemical analysis of the same dried slurry showed a concentration of 20.7%.
of carbon was analyzed. From the above, it can be seen that the dried slurry contains zonotrite crystals and amorphous carbon as main components. Next, 7 parts of glass fiber and 3 parts of Portland cement were added as additives to 90 parts (solid content) of the slurry obtained above, which was then press-molded, dried at 100°C for 24 hours, and then fired in an atmosphere at 500°C for 1 hour. , the amorphous carbon was removed to obtain a molded body. The physical properties of the obtained molded product were as shown in Table 1.

[Table] Furthermore, when the molded body samples No. 1 and 2 listed in Table 1 were crushed and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. Example 2 24.6 parts of quicklime (CaO95.0%) was added to 295% of warm water at 80°C.
The sedimentation volume of the milk of lime, which was slaked in a vacuum chamber and dispersed in water using a homomixer, was 15.3 ml. Add the above lime milk to the same rice husk charcoal powder as in Example 1.
Add the slurry obtained by dispersing 45.4 parts with 10 times the weight of water in a homomixer for 2 minutes, then add more water and mix so that the total amount of water is 30 times the weight of the solid content to obtain a raw material slurry. , this is the saturated water vapor pressure
A hydrothermal synthesis reaction was carried out for 5 hours with stirring at 12 Kg/cm ² and a temperature of 191° C. in an autoclave with a stirring blade rotating at a rotational speed of 102 rpm to obtain a slurry. When the slurry obtained above was dried at 100° C. for 24 hours and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. Furthermore, when this slurry was dried in the same manner as above and observed under a scanning electron microscope, spherical secondary particles similar to those in Example 1 were observed, and chemical analysis of the same dried slurry revealed that 21.0% Carbon was analyzed. From the above, it can be seen that the dried slurry contains zonotrite crystals and amorphous carbon as main components. Next, 7 parts of glass fiber and 3 parts of Portland cement were added as additives to 90 parts (solid content) of the slurry obtained above, which was then press-molded, dried at 100°C for 24 hours, and then fired in an atmosphere at 500°C for 1 hour. , the amorphous carbon was removed to obtain a molded body. The physical properties of the obtained molded product were as shown in Table 2.

[Table] Furthermore, when the molded body samples No. 1 and 2 listed in Table 2 were crushed and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. Example 3 56.6 parts of quicklime (CaO95.0%) was added to 679 parts of warm water at 80°C.
The sedimentation volume of the milk of lime obtained by slaking in the chamber was 4.7 ml. To the above lime milk, barley charcoal powder ( _{SiO 2} ^48.6 %,
Add 118.5 parts of carbon (C42.3%, adsorbed moisture 6.3%), add water, and mix so that the total amount of water is 12 times the weight of the solid content to obtain a raw material slurry. cm ² and a temperature of 191° C., the mixture was stirred in an autoclave with a stirring blade rotating at a rotation speed of 102 rpm, and a hydrothermal synthesis reaction was carried out for 5 hours to obtain a slurry. When the slurry obtained above was dried at 100° C. for 24 hours and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. In addition, when this slurry was dried in the same manner as above and observed with a scanning electron microscope, spherical secondary particles similar to those in Example 1 were observed, and chemical analysis of the same dried slurry revealed that 27.9% Carbon was analyzed. From the above, it can be seen that the dried slurry contains zonotrite crystals and amorphous carbon as main components. Next, 7 parts of glass fiber and 3 parts of Portland cement were added as additives to 90 parts (solid content) of the slurry obtained above, which was then press-molded, dried at 100°C for 24 hours, and then fired in an atmosphere at 500°C for 1 hour. , the amorphous carbon was removed to obtain a molded body. The physical properties of the obtained molded product were as shown in Table 3.

[Table] Furthermore, when molded body samples No. 1 and 2 listed in Table 3 were crushed and subjected to X-ray diffraction analysis, a peak of zonotrite crystals was observed. Example 4 35.9 parts of quicklime (CaO95.0%) was added to 430 parts of warm water at 80°C.
The sedimentation volume of the milk of lime obtained by slaked in a vacuum chamber and dispersed in water using a homomixer was 17.5 ml. The above lime milk and the same rice husk charcoal powder as in Example 1 31.0
Silica powder (SiO ₂ 94.7
%) and further water to obtain a raw material slurry, which was mixed so that the total amount of water was 24 times the weight of ^the solid content.
A slurry was obtained by stirring in an autoclave at 191° C. with a stirring blade rotating at a rotational speed of 138 rpm to perform a hydrothermal synthesis reaction for 5 hours. When the slurry obtained above was dried at 100° C. for 24 hours and subjected to X-ray diffraction analysis, peaks of zonotrite crystals and a small amount of tobermolite crystals were observed. In addition, when this slurry was dried in the same manner as above and observed with a scanning electron microscope, the outer diameter was 5 to 80 mm.
Spherical secondary particles of μm in size were observed, and chemical analysis of the dried slurry revealed that it contained 10.7% carbon. From the above, it can be seen that the dried slurry contains zonotrite crystals and amorphous carbon as main components. Next, 7 parts of glass fiber and 3 parts of Portland cement were added as additives to 90 parts (solid content) of the slurry obtained above, which was then press-molded, and dried and fired at the same time in an atmosphere of 500°C for 2 hours to produce amorphous carbon. It was removed to obtain a molded body. The physical properties of the obtained molded product were as shown in Table 4.

[Table] Furthermore, when molded body samples No. 1 and 2 listed in Table 4 were crushed and subjected to X-ray diffraction analysis, peaks of zonotrite crystals and a small amount of tobermolite crystals were observed.

Claims (1)

[Claims] 1 A raw material slurry obtained by mixing a silicic acid raw material mainly composed of charcoal and a lime raw material with water such that the amount of water is 5 times or more by weight relative to the solid content is hydrothermally synthesized while heating and stirring under pressure. The reaction is carried out to form an aqueous slurry mainly composed of zonotrite crystals and amorphous carbon, which is then molded.
1. A method for producing a lightweight calcium silicate molded body, which comprises drying to obtain a carbon-containing calcium silicate molded body, and then firing the molded body.