JPH0587463B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for producing a calcium silicate molded body with significantly improved heat insulation performance. Background of the Invention Calcium silicate molded bodies are widely used in various fields because they are lightweight, have excellent heat insulation properties, have high fire resistance, and have many other properties. In recent years, in the fields of heat retaining materials, heat insulating materials, etc., there has been a demand for calcium silicate molded bodies with even higher heat insulation performance. JP-A-58-145652 discloses a method of improving the heat insulation performance by incorporating a substance that absorbs or scatters radiant energy into a calcium silicate molded body. However, in this method, if the content of the above substances exceeds 20% by weight in the molded article, the thermal conductivity increases, and silicon carbide is the only material that can reduce the thermal conductivity when the content is less than 20% by weight. It was limited to three types: , silicon nitride, and ilmenite. DISCLOSURE OF THE INVENTION The present invention overcomes the limitations of the conventional methods described above, and its purpose is to provide a new method for producing a calcium silicate molded body with significantly improved heat insulation performance. In the present invention, an aqueous slurry of a calcium silicate crystal precursor is prepared by preliminarily reacting a raw material slurry containing a silicate raw material, a lime raw material, and water while heating and stirring under normal pressure or pressure, and then molding the slurry. In the method of producing a calcium silicate molded body by steam curing and drying the resulting formed body, titanium oxide is added to a raw material slurry or an aqueous slurry of a calcium silicate crystal precursor, and dry heat curing is performed instead of steam curing. The present invention relates to a method for producing a calcium silicate molded body, which is characterized by the following. The calcium silicate molded body obtained by the method of the present invention has significantly improved heat insulation performance by containing titanium oxide, which is an infrared shielding material, and also maintains sufficient strength for practical use. be. According to the method of the present invention, titanium oxide, which is an infrared shielding material, is used, but its content is not substantially limited. That is, it is possible to improve the heat insulation performance by using titanium oxide as an infrared shielding material, and in particular, when the shielding material is contained in an amount exceeding 20% by weight in the total solid content of the molded article, the heat insulation performance is further significantly improved. . In addition, conventional steam curing of formed bodies has the disadvantage that the formed bodies may undergo shrinkage, deformation, cracks, etc. (this disadvantage usually increases as the amount of additives increases). According to the method of the invention, this drawback can be overcome despite the inclusion of an infrared shielding material. The reason why the above-mentioned effects are obtained by the present invention is not clear, but the residual stress strain caused by molding in the formed body and the stress strain on the calcium silicate precursor due to the infrared shielding material contained in the formed body are caused by steam curing. Instead, it can be alleviated by performing dry heat curing, so it can be assumed that deformation of the molded article can be prevented. In the present invention, titanium oxide such as rutile and anatase is used as an infrared shielding material. Such an infrared shielding material is a compound that has the property of shielding infrared rays, which are heat rays, and is chemically inert to the reaction for producing calcium silicate crystals. In the present invention, a formed body obtained by molding an aqueous slurry of a calcium silicate crystal precursor is subjected to dry heat curing. The dry heat curing in the present invention is
Usually in a pressure-resistant sealed container such as an autoclave,
Normally the temperature inside the container is 130℃ without blowing in steam.
This is done by heating to about ~300°C.
The dry heat curing time is usually about 3 to 30 hours.
The heating temperature and time in the dry heat curing are determined as appropriate within the above range depending on the type of calcium silicate crystal precursor constituting the formed body, the type of calcium silicate crystal to be obtained, the shape and size of the formed body, etc. It is determined. Through the dry heat curing, water vapor is generated from the formed body, and the calcium silicate crystal precursor in the formed form is converted into calcium silicate crystals such as tobermolite crystals, xonotrite crystals, and phosiyaite crystals by this water vapor and heat. This dry heat curing not only prevents deformation of the molded product, but also improves the strength and dimensional stability compared to the case without this treatment. The production method of the present invention basically consists of the following steps: Except for adding a specific infrared shielding material to the raw material slurry or the aqueous slurry of calcium silicate crystal precursor and dry heat curing instead of steam curing,
No. 1953 or Japanese Patent Publication No. 58-30259, a raw material slurry containing a silicic acid raw material, a lime raw material, and water is preliminarily reacted with heating and stirring under normal pressure or pressure to form an aqueous slurry of calcium silicate crystal precursor. The method is similar to the method of producing a calcium silicate molded body by preparing the molded body, then molding it, and then curing and drying the resulting molded body with steam. As the silicic acid raw materials used in the present invention, any of those conventionally used in the production of calcium silicate molded bodies can be effectively used. Examples include silica gel, silica flour (ferrosilicon dust, etc.), white carbon, diatomaceous earth, and silica obtained by reacting hydrosilicic acid and aluminum hydroxide, which are by-produced in the wet phosphoric acid production process. In addition, all the materials that have been used traditionally can be used as lime raw materials, such as quicklime,
Examples include slaked lime and carbide slag. Moreover, the CaO/SiO ₂ molar ratio of the silicic acid raw material and the lime raw material is usually about 0.5 to 1.5. For example, if you are trying to synthesize tobermolite crystal, it is 0.70 to 0.90.
It is preferable to set it to about 0.90 to 1.15 when trying to synthesize xonotlite crystals, and about 1.1 to 1.5 when trying to synthesize phosciaite crystals. In the production method of the present invention, a raw material slurry is prepared by adding an infrared shielding material to the silicic acid raw material, lime raw material, and water, or to these materials. Conventionally known additives may be added to the raw material slurry, and examples of such additives include inorganic fibers such as asbestos and rock wool. The amount of water when preparing the raw material slurry is 5 times or more by weight, preferably 10 to 50 times the solid content of the raw material slurry. Next, this raw material slurry is preliminarily reacted to prepare an aqueous slurry of calcium silicate crystal precursor. Calcium silicate crystal precursors refer to various intermediates when calcium silicate crystals are generated from silicate raw materials and lime raw materials, such as calcium silicate gel, C-S-H (), C-S-H (), etc. can be mentioned. The method for obtaining the precursor is, for example, by heating the raw material slurry to about 80 to 98°C under normal pressure and reacting it, or by carrying out a hydrothermal synthesis reaction under a saturated steam pressure of usually 3 kg/cm ² or more. It can be done. This provides an aqueous slurry of calcium silicate crystal precursor. When the infrared shielding material is not added to the raw material slurry, the infrared shielding material is added to the aqueous slurry of the precursor and mixed uniformly. The amount of infrared shielding material added in the present invention is such that the content in the molded product is 1 to 70% by weight based on the total solid content of the molded product.
It is appropriate to set the amount to about 10 to 60% by weight, preferably about 10 to 60% by weight. If the amount added is within this range, a significant improvement in heat insulation performance can be obtained while maintaining sufficient practical strength. In addition, the infrared shielding material used is usually in the form of a powder, and its particle size is usually about 0.001 to 150 μm, preferably 0.001 to 150 μm.
Approximately 100 μm is appropriate. Furthermore, as the above-mentioned infrared shielding material, both synthetic and natural materials can be used, and although these may contain impurities, they are acceptable as long as they do not have any adverse effects. Next, the aqueous slurry of the calcium silicate crystal precursor containing the infrared shielding material obtained above is molded. At this time, prior to molding, various additives may be further added and mixed as necessary. As additives in this case, those that have been used in the production of calcium silicate molded bodies can be used in a wide range.
Examples include fibers. The molding method may be, for example, press dehydration molding, centrifugal dehydration molding, roll dehydration molding, mold molding, paper forming, extrusion molding, or the like. Next, the green body obtained above is subjected to dry heat curing as described above. Next, the desired calcium silicate molded body is obtained by drying. In addition, during molding, if necessary, an aqueous slurry of calcium silicate crystal precursor containing an infrared shielding material and the slurry not containing an infrared shielding material are used, for example, the former slurry is placed in a mold and pressed. A laminate molded product can be obtained by dehydration molding, and then placing the latter slurry in a mold and press dehydration molding, or by performing the reverse operation. The calcium silicate molded body obtained by the present invention can be easily manufactured from high density to low density.
Even molded articles of about 0.1 g/cm ³ can be easily produced. EXAMPLES The present invention will be specifically described 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: Measured according to the method of JIS A9510. (b) Thermal conductivity...Measured according to the cylinder method of JIS A9510. Example 1 Quicklime (CaO 94.8%) was slaked in warm water at 80°C and dispersed in water using a homomixer to obtain milk of lime. Silica stone powder (SiO ₂ 97.6%) with an average particle size of 4.6 μm was added to the above milk of lime so that the CaO/SiO ₂ molar ratio was 1.00, and water or a predetermined amount of titanium oxide (rutile, average Particle size
2.0 μm) powder and water were added and mixed so that the total amount of water was 24 times the weight of the solid content to obtain a raw material slurry. This is saturated water vapor pressure 14Kg/cm ² and temperature
The reaction was carried out for 2 hours by stirring in an autoclave at 197°C with a stirring blade rotating at a rotation speed of 40 rpm, and the main components were C-S-H () or C-S-H () and rutile crystals. An aqueous slurry was obtained. Next, 5 parts of alkali-resistant glass fiber and 3 parts of pulp were added to 92 parts (solid content) of the slurry obtained above, and press dehydration molding was performed to form a product with an inner diameter of 114 mm, a thickness of 50 mm, and a length of 50 mm.
A 610 mm cylindrical shaped product was obtained. This formed body was placed in an indirect heating autoclave and dry heat cured at 180°C for 8 hours. After dry heat curing, this molded body was heated to 100℃.
dried with. It should be noted that the molded product did not experience any shrinkage, deformation, cracks, etc. during dry heat curing. When the obtained compact was analyzed by X-ray diffraction, peaks of xonotrite crystals and rutile crystals were observed in the case where titanium oxide powder was added. The physical properties of each molded article were as shown in Table 1.

【table】

[Table] It is clear from Table 1 that the molded bodies obtained by the method of the present invention all have significantly improved heat insulation performance, and also maintain sufficient practical strength.

Claims (1)

[Claims] 1 A raw material slurry containing a silicic acid raw material, a lime raw material, and water is preliminarily reacted with stirring under normal pressure or pressure to prepare an aqueous slurry of a calcium silicate crystal precursor, and then this is obtained by molding. A method for producing a calcium silicate molded body by steam curing and drying a formed body, characterized by adding titanium oxide to a raw material slurry or an aqueous slurry of a calcium silicate crystal precursor, and performing dry heat curing instead of steam curing. A method for producing a calcium silicate molded body.