JPS6149264B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a calcium silicate molded body. Specifically, the present invention relates to a method for producing a calcium silicate molded body using glass fiber, which has a low bulk density, excellent heat resistance, mechanical strength, and dimensional stability, and is therefore suitable as a heat insulating material and a heat insulating material.
Calcium silicate molded bodies, especially those containing xonotlite as a main component, have heat resistance of 1000°C or higher and are therefore suitable as heat insulators and heat insulators. In general, calcium silicate molded bodies are produced by decomposing silicic raw materials and calcareous raw materials into water, reacting them under heating at 80°C or higher and 100°C or lower, dehydrating the resulting slurry, and steam-curing the molded product under pressure. Manufactured by The calcium silicate molded article contains inorganic reinforcing fibers in order to increase its mechanical strength and improve its water resistance during molding. Inorganic reinforcing fibers need to be heat resistant and alkali resistant in order to withstand steam curing under lime alkaline conditions, and for this reason asbestos, especially amosite asbestos, is used as inorganic reinforcing fibers. The above purpose can be achieved with a relatively low content of asbestos, for example, 10% by weight or less, but in that case, the heat shrinkage during heating is large, and it is specified in the JIS standard.
It is not satisfied that the linear shrinkage rate of the calcium silicate molded product after heating at 1000°C for 3 hours is 2.0% or less. Of course, this problem can be solved by containing a large amount of asbestos, for example 10% by weight or more. However, asbestos is expensive, and since it is a natural resource, there is a risk of depletion, so it is most desirable not only to reduce the amount of asbestos used, but also to not use it at all. Other possible inorganic reinforcing fibers for calcium silicate moldings include rock wool glass fibers and alkali-resistant glass fibers. Among these, rock wool and glass fiber are relatively inexpensive and easily available. However, when rock wool or glass fibers are used as reinforcing fibers for calcium silicate molded bodies, in the conventional method, during production, the rock wool or glass fibers react with the alkali content of the raw material, or are eroded by the alkali content, resulting in mechanical problems. It is difficult to obtain a molded product with excellent mechanical strength. For this reason, rock wool or glass fibers are not actually used as reinforcing fibers for calcium silicate molded bodies. Also, like asbestos, alkali-resistant glass fibers are highly resistant to alkali and can be used as reinforcing fibers for calcium silicate molded bodies, but they are extremely expensive and have not yet been used industrially. In view of this, the present inventors conducted extensive research and found that glass fiber can be used instead of asbestos as the inorganic reinforcing fiber in the manufacturing method of a specific calcium silicate molded product, and has low bulk density, heat resistance, and mechanical properties. It was discovered that a calcium silicate molded article with excellent mechanical strength could be obtained, and the present invention was achieved. That is, the gist of the present invention is to prepare a calcium silicate hydrate consisting of tobermorite group having a sedimentation volume of 15 cm ³ /g or more obtained by reacting a silicate raw material and a calcareous raw material dispersed in water under heating. Glass fiber is added to the aqueous slurry so that the final molded product contains 0.5 to 10% by weight of glass fiber, dehydrated and molded, and then cured with steam under pressure to form calcium silicate hydrate. The present invention relates to a method for producing a calcium silicate molded body, which is characterized by displacing crystals. The method of the present invention will be explained in detail below. In the method of the present invention, first, a siliceous raw material and a calcareous raw material dispersed in water are reacted under heating.
It is necessary to produce a slurry containing calcium silicate hydrate crystals consisting of compounds of the tobermorite group with a sedimentation volume of usually greater than 15 cm ³ /g. Silicic acid raw materials include natural products such as diatomaceous earth and silica stone, silicon dust, and silica obtained by reacting hydrosilicic acid, a by-product of the wet phosphoric acid manufacturing process, with aluminum hydroxide (hereinafter simply referred to as wet phosphoric acid by-product silica). ) and other industrial by-products. As the calcareous raw material, conventionally known materials such as quicklime, slaked lime, and carbide slag can be used. Mixing molar ratio of siliceous raw material and calcareous raw material (CaO/
SiO ₂ ) is commonly used when xonotlite is desired as calcium silicate hydrate crystals in the final molded product.
It is within the range of 0.8 to 1.2, and if crystalline tobermorite is desired, it is usually within the range of 0.7 to 1.0. The amount of water for dispersing both of the raw materials may be at least 15 times the solid content of the raw materials, particularly 17 to 40 times the solid content of the raw materials.
A range of times the weight is preferred. If both of the above raw materials dispersed in water are reacted under heating, an aqueous slurry containing calcium silicate hydrate crystals can be obtained. In this method, the calcium silicate hydrate crystals in the slurry are first must be 15 cm ³ /g or more. Here, the sedimentation volume is a value calculated by the following equation (). Sedimentation volume = V/W ...... () In formula (), W is the total weight of raw material solid content (e.g. calcareous raw material + silicic raw material) (However, if calcareous raw material other than quicklime is used, it is converted to quicklime. The total weight is determined), and V is the volume occupied by the solid content that settled after the slurry obtained after the reaction was allowed to stand for 24 hours. In practice, it is usually determined as follows. First, from the slurry with a total weight of W ₀ g obtained after the reaction, W ₁ g was collected into a measuring cylinder, and this was
After standing for a period of time, the amount of solid content that settles out is V ₁ cm ³
is measured and calculated using the following formula (). Note that W has the same meaning as the formula () and indicates the total weight of the raw materials. As a method to increase the sedimentation volume to 15cm ³ /g or more,
The reaction is carried out under stirring at 130°C or higher, especially at 150-230°C.
The most suitable method is a method carried out at 160 to 210°C. In this case, the reaction system must be kept in a liquid state, and therefore the reaction is carried out under pressure. Second, the calcium silicate hydrate crystals in the slurry must be a tobermorite group compound. Various types of calcium silicate hydrate crystals are known, and they are generally described in "The Chemistry of Cement" by HFWTaylor.
Cements) Volume 1, page 182 Tobermorite group compounds include tobermorite gel, C-S-H (), C-S
-H() and crystalline tobermorite, but
It may be either. Calcium silicate hydrate crystals are produced by tobermorite gel → C-S-H ()
Since the transition normally occurs in the order of →C-S-H() → 11 Å tobermorite (crystalline tobermorite) → xonotrite, it is sufficient to adjust the reaction temperature and time to obtain the desired crystal. In other words, if the reaction temperature is increased or the reaction time is increased,
The crystals transfer in the direction of the arrow (→) mark. If the reaction is carried out in a temperature range to achieve the first condition,
Compounds of the tobermorite group are usually obtained.
However, if the reaction temperature is particularly high or the reaction time is particularly long, xonotlite will be obtained, so in that case, the temperature may be lowered or the reaction time may be shortened. In addition, when crystalline tobermorite is desired as crystals in the final molded product, the calcium silicate hydrate in the slurry is tobermorite gel, C-S-
It must be H() or C-S-H(). In the method of the present invention, it is necessary for the calcium silicate in the aqueous slurry to satisfy both the first and second conditions mentioned above, and even if either of these conditions is lacking, the bulk density can be increased by using glass fiber. It becomes impossible to obtain a molded product with low mechanical strength and excellent mechanical strength. The aqueous slurry thus obtained contains glass fibers in the final molded product.
The purpose of the present invention cannot be achieved if the content of glass fiber added is from 0.5 to 10% by weight, preferably from 0.5 to 6% by weight, if the content is too much or too little than the above range. Although glass fibers may be added as they are, it is preferable to disperse them well in water in advance. Further, if it is added in advance before producing the aqueous slurry, it is not preferable because it becomes difficult to obtain a molded product with excellent mechanical strength. As the glass fiber, any glass fiber normally used for building materials can be used. Specific examples include E glass fiber, C glass fiber, and A glass fiber. Such an aqueous slurry to which glass fibers have been added is subjected to pressure dehydration molding according to a conventional method. The pressure at that time is usually in the range of 1 to 200 kg/cm ² G, and the bulk density of the molded product is adjusted by adjusting the piston stroke of the pressure molding machine. Next, the obtained molded body is subjected to steam curing under pressure, so-called autoclave curing, according to a conventional method. By this steam curing, the crystals of the molded body are removed from tobermorite gel, C-S-H () or C-S-H
In the case of (), it is necessary to transform into crystalline tobermorite or xonotlite, and in the case of crystalline tobermorite, it is necessary to transform it into xonotlite. The crystal transformation caused by this steam curing makes it possible to obtain a molded article with low bulk density and excellent mechanical strength. Generally, the higher the water vapor pressure, the shorter the reaction time, but it is usually in the range of 5 to 50 kg/cm ² G. 12 to 40 if xonotlite is desired as crystals in the final molded product
Kg/cm ² G, and if crystalline tobermorite is desired, 6 to 30 Kg/cm ² G water vapor is suitable. Under such conditions, the above-mentioned transfer is usually easily carried out. If the transfer does not occur as desired,
Although such cases are extremely rare, for example, if you want xonotlite but crystalline tobermorite is obtained, you can increase the steam pressure or extend the steam curing time; If xonotlite can be obtained, conversely, the steam pressure should be lowered or the steam curing time should be shortened. In applications requiring high heat resistance, it is preferable to transform it into xonotlite. The present invention has been described in detail above, and the molded article obtained by the method of the present invention has the following characteristics. (1) Despite being a glass fiber-containing molded product, it has physical properties equivalent to or better than asbestos-containing molded products. (2) Good dimensional stability despite low glass fiber content. (3) Despite its low bulk density, it has mechanical strength equivalent to that of a material with a higher bulk density. (4) High heat resistance. Such molded bodies are expected to have a wide range of uses as heat insulating materials and fireproof heat insulating materials. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, "parts" in the examples indicate "parts by weight." Examples 1 to 3 and Comparative Examples 1 to 2 The amount of quicklime (CaO 98%) shown in Table 1 was digested by adding warm water, and the amount of silica (wet phosphoric acid by-product silica, composition SiO ₂ 97.8%,
After adding 0.4% Al ₂ O _{3 and} 1.5% loss on ignition, water was added so that the total amount of water was 25 times the solid content. The suspension thus obtained was stirred and reacted in an autoclave at 12 Kg/cm ² G and 191°C for 4 hours. A slurry was obtained. In this aqueous slurry, glass fibers (manufactured by Asahi Fiber Glass, trademark
CS13HB630B) was added in the amount shown in Table 1, and then dehydrated and molded. This molded body was placed in an autoclave, steam-cured for 8 hours under conditions of a steam pressure of 18 Kg/cm ² G and 209°C, and then dried at 150°C for 8 hours. The type of crystal, which is the main component of the calcium silicate molded body thus obtained, the bulk density, the bending strength, and the linear shrinkage rate after heating at 1000°C for 3 hours were
Shown in the table. Note that in Comparative Example 2, amosite asbestos was used instead of glass fiber.

[Table] Comparative Example 3 45.8 parts of quicklime (CaO98%) was digested by adding warm water, and silica (wet phosphoric acid by-product silica, composition
After adding 49.2 parts of _SiO2 (97.8%, _{Al2O3 0.4} %, loss on ignition 1.5%), water was added so that the total amount of water was 10 times the solid content. The suspension thus obtained was stirred at 90°C for 2 hours to react, and then heated to room temperature.
The mixture was allowed to stand for 24 hours for aging. The settling volume of this aqueous slurry was 8 cm ³ /g and the product was a gel. After adding 5 parts of glass fiber to this aqueous slurry, it was dehydrated and molded. This molded body was placed in an autoclave, steam-cured for 20 hours under conditions of a steam pressure of 18 Kg/cm ² G and 209°C, and then dried at 150°C for 8 hours. The main component of the calcium silicate molded body thus obtained is xonotlite, and the bulk density is 0.20.
The bending strength was 1.8 kg/cm ² in g/cm ³ , and the linear shrinkage rate after heating at 1000° C. for 3 hours was 2.2%.

Claims (1)

[Claims] 1 The sedimentation volume obtained by reacting siliceous raw materials and calcareous raw materials dispersed in water under heating is 15 cm ³ /
Glass fibers are added to an aqueous slurry containing calcium silicate hydrate consisting of a tobermorite group having an amount of 0.5 to 10% by weight in the final molded product, and after dehydration molding, 1. A method for producing a calcium silicate molded article, which comprises transferring crystals of calcium silicate hydrate by steam curing under pressure.