JPS6323148B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a calcium silicate molded body and a method for manufacturing the same, and more particularly to a calcium silicate molded body that blocks radiant heat transfer and has extremely excellent heat insulation properties, and a method for manufacturing the same. In general, when performing insulation construction, it is desirable to design the material to have low conductive heat transfer in solids, conductive heat transfer in air layers, convective heat transfer in air, and radiant heat transfer that contribute to heat conduction. Therefore, as a means of reducing the conductive heat transfer in solids, a method of reducing the density of the solid has been adopted. Solid conduction generally decreases due to lower density, but in high temperature regions, lower density increases the number of pores, and the vacancies increase compared to increases in conductive heat transfer in solids, conductive heat transfer in air, and convective heat transfer. There was a problem that the contribution of radiation heat transfer passing through the heat exchanger was large, making it impossible to expect an overall improvement in insulation performance. In addition, vacuum insulation is a method for reducing conductive heat transfer and convective heat transfer in an air layer, but in this case, it is necessary to ensure that the vacuum container can sufficiently withstand atmospheric pressure and not deform. Since the material needs to be quite thick, it also has the disadvantage of being heavy. For this purpose, it is possible to reduce the thickness of the metal material by placing a core material with strong compressive strength in the vacuum container, but this method increases the proportion of radiation heat transfer in the total heat transfer of the vacuum insulation material. Become. It can be seen that reducing the radiant heat transfer in the heat insulating material is a very effective means for improving the heat insulating performance. Conventional methods for reducing radiant heat transfer include inserting shiny metal foil into heat-insulating molded bodies, and mixing metal powder with powdered heat-insulating materials such as calcium silicate and perlite as a core material between walls for vacuum insulation. It is known how to use In the former case, it is difficult to integrate the metal foil and the heat insulating molded body, and there are problems in terms of adhesive deterioration and workability. In addition, in the case of the latter powder heat insulating material, the metal powder is not fixed, and vibrations during transportation often cause the metal powder to move and become unevenly distributed, making it difficult to achieve the intended purpose. For example, 94 parts by weight of calcium silicate powder and 6 parts by weight of copper powder were evenly mixed, and the mixture was poured into a metal container (thickness: 25 mm, length: 300 mm, width: 0.3 mm) made from a stainless steel plate (thickness: 0.3 mm).
When measuring the thermal conductivity when a 300 mm thick tube was filled and subjected to vibration for 24 hours, there was a change in the thermal conductivity as shown in Table 1 below.

[Table] In view of the above-mentioned current situation, the present inventor focused on a calcium silicate heat-insulating molded body in the process of continuing research for the purpose of reducing radiation heat transfer, and uniformly contained metal powder in this molded body. I came up with a completely new idea that I might be able to achieve my desired purpose if I did so, and as a result of further research, I was able to complete the present invention. That is, the present invention provides a calcium silicate heat-insulating molded body in which 1 to 30% by weight of metal powder passing through a 150 mesh is almost uniformly dispersed in the calcium silicate heat-insulating molded body, and an aqueous calcium silicate slurry. The present invention relates to a method for producing a heat-insulating calcium silicate molded body, which is characterized by mixing metal powder that passes through 150 meshes and drying with or without steam curing after molding. Specific examples of the metal powder used in the present invention include powders of various metals such as aluminum, copper, iron, chromium, nickel, and brass, and those with metallic luster and high reflectance are particularly desirable. The metal powder may be subjected to known pretreatment such as chemical treatment such as pH adjustment. Furthermore, it is essential to use metal powder that can pass through 150 meshes. As a result, radiant heat can be effectively blocked and sufficient insulation performance can be achieved. The preferred one is one that passes through the entire 250 meshes. If the metal powder is larger than the one that completely passes through 150 meshes, the improvement in insulation performance will be insufficient. The amount of this metal powder used is usually about 1 to 30% by weight, preferably about 3 to 10% by weight of the total weight of the calcium silicate heat insulating molded article. In this case, if the amount is less than 1% by weight, the radiant heat will not be blocked sufficiently, and if it exceeds 30% by weight, the radiant heat transfer will be suppressed, but the solid heat transfer of the metal powder will increase, and the overall effect will be There is a tendency that the insulation performance does not improve. The calcium silicate heat insulating molded body used in the present invention can be used in a wide variety of crystal forms manufactured by various manufacturing methods, and it is particularly preferable that secondary particles of calcium silicate crystals are immersed in water. Moldings made from dispersed slurries are preferred. In preparing the molded article of the present invention, it is first necessary to prepare a slurry of calcium silicate. This calcium silicate slurry includes a calcium silicate gel slurry and a calcium silicate crystal slurry. In order to produce the former slurry of calcium silicate gel, a raw material slurry prepared from a silicate raw material, a lime raw material, and water may be heated and reacted. In preparing the latter calcium silicate crystal slurry, the above raw material slurry is heated under pressure while stirring to obtain a slurry of calcium silicate crystals all at once. All of these calcium silicate slurries are known, and include those produced by various manufacturing methods. In the case of a slurry of calcium silicate gel, the specified metal powder is added in a specified amount of one or more of various other additives as required, mixed uniformly, and then molded to crystallize the calcium silicate gel under saturated water vapor pressure. It is then hardened to form a molded product. On the other hand, in the case of a slurry of calcium silicate crystals, a predetermined metal powder may be added together with one or more of various other additives as required, mixed uniformly, then shaped and dried. Other additives that can be used at this time include a wide range of additives that have been used to produce this type of calcium silicate molded product, such as asbestos, rock wool, glass fiber, and even silicic acid as a calcium silicate slurry. When calcium crystal slurry is used, pulp and various natural or synthetic fibers can be used, and clay, cement, etc. can also be used. In the thus obtained molded article of the present invention, the metal powder is dispersed and held almost uniformly over the entire molded article, so the metal powder does not move even if vibrations are applied, and the radiant heat is reliably and stably radiated. can be blocked. EXAMPLES The present invention will be specifically described below with reference to Examples. However, in the following examples, parts refer to parts by weight. Example 1 Silica powder with an average particle size of about 5 μm was added to lime milk obtained by slaking 47 parts of quicklime in 500 parts of hot water at 90°C.
A raw material slurry was prepared by adding 53 parts and further adding water so that the total amount of water was 24 times the weight of the solid content. This raw material slurry was heated under saturated steam pressure for 12 hours.
Kg/cm ² and hydrothermal synthesis at 191° C. for 8 hours with stirring to obtain an aqueous slurry consisting of zonotrite crystals. For 85 parts of solid content of this calcium silicate crystal slurry, 6 parts of glass fiber, 3 parts of pulp and
A slurry obtained by uniformly mixing 6 parts of copper powder for a total of 250 meshes was molded into two types of molded bodies of 25 x 300 x 300 mm with varying densities as shown below and dried. The density of the molded body is 0.10g/ ^cm3 and 0.14g/cm3, respectively.
cm ³ and was measured using the JISA-1413 thermal conductivity measurement method for heat insulating materials (flat plate direct method). For comparison, two types of molded bodies with densities of 0.1 g/cm ³ and 0.14 g/cm ³ were prepared in the same manner as above except that copper powder was not added. The thermal conductivity of this material was also measured in the same manner. The results of these measurements were as shown in Table 2.

【table】

[Table] Example 2 After adjusting the calcium silicate crystal slurry obtained in the same manner as in Example 1 to pH 9.5, 6.3 parts of glass fiber, 4.5 parts of pulp, and 250 mesh were added to the solid content of 79.2 parts of the crystal slurry. whole aluminum powder
10 parts were uniformly mixed to obtain a slurry. The slurry was molded into a size of 25 x 300 x 300 mm and the dried molded product had a density of 0.12 g/cm ³ and its thermal conductivity was measured in the same manner as in Example 1. For comparison, the thermal conductivity of a molded article having a density of 0.12 g/cm ³ was also measured in the same manner as above, except that no aluminum powder was added. The results of these measurements were as shown in Table 3.

[Table] Regarding the aluminum powder-containing calcium silicate molded bodies obtained in Example 2, the thermal conductivity was measured for various molded bodies in which only the aluminum powder content was varied. The results are shown in FIG. The measurement was performed with the molded body in a vacuum state (1×
The test was carried out at an average temperature of ²⁰ °C. As is clear from FIG. 1, the proportion of aluminum powder is 1 to 30% by weight, preferably 3 to 10% by weight, and is maximum at 6 to 8% by weight. Furthermore, when vibration experiments were conducted on the molded bodies of the present invention obtained in Examples 1 and 2 above, it was found that there was no effect on thermal conductivity due to the application of vibration for 24 hours, and the results showed that the thermal conductivity was not affected over a long period of time (one week). No change in thermal conductivity was observed even when vibration was applied. Example 3 For 80 parts of solid content of calcium silicate crystal slurry obtained in the same manner as in Example 1, 4 parts of glass fiber was added.
1 part, 3 parts of cement, 3 parts of pulp, and 10 parts of iron powder for 150 meshes were uniformly mixed to obtain a slurry. The slurry was molded into a size of 25 x 300 x 300 mm, and the density of the dried molded product was 0.15 g/cm ³ .
Thermal conductivity was measured using the same method. For comparison, we also used a compact with a density of 0.15 obtained by processing in the same manner as above without adding iron powder.
The thermal conductivity of g/cm ³ was also measured in the same manner. The results of these measurements were as shown in Table 4.

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the content of aluminum powder and the thermal conductivity of a calcium silicate molded body containing aluminum powder.

Claims (1)

[Claims] 1. 1 to 30% by weight of calcium silicate heat insulating molded body.
150 A calcium silicate heat insulating molded body characterized by metal powder being almost uniformly dispersed throughout the mesh. 2. A method for producing a heat-insulating calcium silicate molded article, which comprises mixing an aqueous slurry of calcium silicate with metal powder that passes through 150 meshes, and drying with or without steam curing after molding. 3. The manufacturing method according to claim 2, characterized in that the calcium silicate crystal slurry is mixed with metal powder that passes through 150 meshes, molded, and then dried.