JPH0547496B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a calcium silicate molded body having excellent heat resistance, light weight, and high strength by extrusion molding. Calcium silicate molded bodies have excellent heat resistance, are lightweight, have high strength, and are highly processable, so they are particularly suitable as building materials. Prior art and its disadvantages Conventionally, molded bodies of calcium silicate crystals have been produced by adding a slurry of secondary particles of calcium silicate crystals, which is obtained by subjecting a raw material slurry containing a silicate raw material, a lime raw material, and water to a hydrothermal synthesis reaction, as needed. It is manufactured by adding reinforcing fibers and the like, filling it into a molding die, molding it by press dehydration molding, etc., and then drying it. However, this method has drawbacks such as difficulty in manufacturing long, thin, and complex-shaped products. Continuous extrusion molding can be used to improve the above drawbacks, but calcium silicate crystal slurry does not have the properties required of a molding material for extrusion, and cannot be extruded as is. It was said that In other words, the molding material for extrusion molding has (1) plasticity so that it can be deformed and molded into a predetermined shape by stress, (2) smoothness so that the material can be extruded smoothly through the die during molding, and (3)
It is necessary for the molded product to have properties such as shape retention to maintain its shape during the drying process, but calcium silicate crystal slurry does not have these properties sufficiently, so it cannot be extruded as it is. I can't do it. Therefore, it is necessary to add some forming aid. To produce calcium silicate molded bodies by extrusion molding, a binder such as water glass and an extrusion accelerator such as methylcellulose are added to calcium silicate, and the mixture is extruded to a total moisture content of 70 to 80% by weight. A method (Japanese Unexamined Patent Publication No. 191260/1983) has also been proposed. However, since this method requires the use of a binder such as water glass, the strength is low, and the strength is only strong enough to be used mainly as a support material for vacuum insulated containers. The drawback is that it is not possible to obtain a material with enough strength to be used as a building material. In addition, since a large amount of extrusion accelerator is used in order to prevent dehydration during extrusion, amounting to 5 to 15% by weight based on the solid content, there is also a drawback that heat resistance is reduced. Solution The present inventors solved the drawbacks of the above conventional method,
We conducted intensive research with the aim of efficiently producing by extrusion molding a calcium silicate molded body that has excellent heat resistance, is lightweight, and has high strength, and can be particularly suitable for use as a building material. In particular, in order to make the resulting molded product lighter and stronger, it is preferable to use calcium silicate crystals in the form of spherical secondary particles obtained by a calcium silicate hydrothermal synthesis reaction;
Research was conducted with consideration given to obtaining a molded product with even higher strength by making extrusion molding possible over a wide range of overall moisture content of the extrusion molding material. As a result, by adding a water-soluble organic polymer substance and a water-absorbing fibrous substance to calcium silicate crystals obtained through a hydrothermal synthesis reaction, we have achieved the appropriate plasticity, smoothness, and shape retention necessary for extrusion molding materials. It was discovered that the objective could be achieved by adding In other words, the calcium phosphate crystal slurry in the form of secondary particles obtained by a hydrothermal synthesis reaction has thixotropic properties, and when it is stirred, water is separated, and when it is extruded as it is, the particles between the secondary particles are separated. Extrusion molding is difficult because it promotes lubrication between the extrusion molding machine and the particles, but here, 2 to 10% by weight of a water-absorbing fibrous material and 0.2 to 5% by weight of a water-soluble organic polymeric material are added to the solid content. %, the water-absorbing fibrous material absorbs the water separated by stirring the slurry, making it suitable for smoothness and also contributing to shape retention. By simply adding a small amount of molecular substance, from 0.2% to less than 5% by weight, it is possible to impart appropriate plasticity and shape retention to the slurry, and these effects allow smooth extrusion of the calcium silicate crystal slurry, as well as the resulting It has been found that the molded product has excellent heat resistance, is lightweight, and has high strength, and can be particularly advantageously used as a building material. The present invention has been completed based on the above findings. Structure of the Invention The present invention provides secondary particles of calcium silicate crystals obtained by hydrothermal synthesis reaction of a raw material slurry containing a silicic acid raw material, a lime raw material, and water. % to less than 5% by weight and 2 to 10% by weight of a water-absorbing fibrous material, and the material has a total moisture content of 20 to 85% by weight. Pertains to manufacturing method. The calcium silicate crystal slurry in the present invention is produced by subjecting a raw material slurry consisting of a silicate raw material, a lime raw material, and water to a hydrothermal synthesis reaction while heating and stirring under pressure. The obtained calcium silicate crystals are three-dimensionally bonded to form approximately spherical secondary particles, thereby increasing the strength of the finally obtained molded product. The size of the spherical secondary particles varies depending on the conditions of the hydrothermal synthesis reaction, especially the amount of water, etc., but is usually 5-
It is about 150 μm. As silicic acid raw materials and lime raw materials, any of those used as raw materials for producing ordinary calcium silicate crystals can be effectively used. For example, silicic acid raw materials include silica stone, silica sand, silica flour, and diatoms. Soil, silicon dust, ferrosilicon dust, etc. are used as lime raw materials, quicklime, slaked lime, etc.
An example is carbide slag. Amount of water during hydrothermal synthesis reaction (ratio of water when silicic acid raw material, lime raw material, and water are subjected to hydrothermal synthesis reaction)
It is usually preferable to set the amount to about 83 to 97% by weight (5 to 30 times the solid content). At this time, the CaO/SiO ₂ molar ratio of the silicic acid raw material and the lime raw material is 0.70 to 0.70 when trying to synthesize tobermolite crystals.
It should be about 0.90, or about 0.90 to 1.15 when trying to synthesize xonotlite crystals. The hydrothermal synthesis reaction is
It is carried out under a saturated steam pressure of usually 4 kg/cm ² or more, preferably 6 kg/cm ² or more. This reaction yields a calcium silicate crystal slurry in which spherical secondary particles made of tobermolite crystals and/or xonotrite crystals are dispersed in water. Next, a water-soluble organic polymer substance, a water-absorbing fibrous substance, etc. are mixed with the calcium silicate crystal slurry, and the total water content is adjusted to about 20 to 85% by weight to prepare a material for extrusion molding. At this time, the calcium silicate crystal slurry obtained by hydrothermal synthesis reaction may of course be used as it is, but it is dehydrated under pressure and the water content is usually 20 to 90% by weight.
It is convenient to adjust the dehydrated cake to a certain degree, and then mix a predetermined composition and water as necessary to this dehydrated cake. Here, the moisture content of the extrusion molding material is 85% by weight.
If the water content exceeds 20% by weight, the shape retention during extrusion will deteriorate and dehydration will occur during extrusion, which is disadvantageous.If the water content is less than 20% by weight, the extrusion material will lose its plasticity and extrusion will become difficult. So I don't like it. Examples of water-soluble organic polymer substances in the present invention include water-soluble cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, water-soluble polymers such as polyvinyl alcohol, sodium polyacrylate, and polyacrylic acid amide. At least one of these is used. Examples of water-absorbing fibrous substances include organic fibrous substances such as natural fibers such as pulp and cotton, synthetic fibers such as acrylic fibers, and inorganic fibrous substances such as asbestos. Use. Particularly preferred among these are pulp, especially powder pulp, asbestos, etc. from the viewpoint of dispersibility.Powder pulp has high hydrophilicity, so it easily retains water and is extremely effective in suppressing slippage during molding. The extrusion molding material in the present invention basically consists of the above-mentioned components, but cement, gypsum, clay, glass fiber, steel fiber, etc. may be added as necessary. The amount of the water-soluble organic polymer substance and the water-absorbing fibrous substance to be used can be selected from a wide range, but the former is usually 0.2% by weight or more of the total solid content of the extrusion molding material.
It is desirable that the amount is less than 2% by weight, and the latter is usually about 2 to 10% by weight. If the amount of the water-soluble organic polymer substance used exceeds the above range, the molding material tends to become slippery in the extrusion screw part of the extrusion molding machine, making molding difficult.
Moreover, the amount of water-soluble organic polymer substances used is 5% by weight.
Since the effect as a molding aid can be expressed by using a small amount of less than 100 ml, the heat resistance of the calcium silicate molded article is not impaired. On the other hand, if the amount used is less than the above range, the plasticity and shape retention of the molding material tend to be insufficient, which is not preferable. Furthermore, if the amount of water-absorbing fibrous material used exceeds the above range, the plasticity of the molding material tends to decrease, and if the amount used is less than the above range, the smoothness and shape retention of the molding material will decrease. This is not preferable because it tends to decrease. Further, it is desirable that the amounts of the water-soluble organic polymeric substance and the water-absorbing fibrous substance used be appropriately adjusted within the above ranges depending on the amount of water during the calcium silicate crystal hydrothermal synthesis reaction. That is, the size of the secondary particles produced varies depending on the amount of water during the hydrothermal synthesis reaction, and usually the larger the amount of water, the smaller the secondary particles. It is recognized that as the secondary particles become smaller, the above-mentioned thixotropy increases, and on the other hand, the smoothness of the slurry becomes relatively high although it cannot be extruded as it is. Therefore, as the amount of separated water increases, it is better to increase the amount of water-absorbing fibrous material used, while decreasing the amount of water-soluble organic polymer material used. When the amount of water during the hydrothermal synthesis reaction decreases, the amount of water-absorbing fibrous material used can be relatively small for the opposite reason to the above, while the amount of water-soluble organic polymer material used can be reduced. It is better to have a relatively large amount. The preferred amount of the water-soluble organic polymer substance and water-absorbing fibrous substance is that the amount of water during the hydrothermal synthesis reaction is 95%
If it exceeds 0.2 to 2.5% by weight and 3 to 10% by weight, more preferably 1.5 to 2% by weight and 4 to 10% by weight, respectively, based on the total solid content of the extrusion molding material.
8% by weight, and when the amount of water during the hydrothermal synthesis reaction is 91% to 95% by weight, respectively, based on the total solid content.
About 0.2 to 3.7% by weight and about 2.5 to 8.7% by weight, more preferably 1.8 to 2.5% by weight and 3.5 to 6.5% by weight,
When the amount of water during the hydrothermal synthesis reaction is less than 91% by weight, it is about 0.2 to less than 0.5% by weight and about 2.0 to 6.5% by weight, more preferably 2.0 to 6.5% by weight, respectively, based on the total solid content.
3.0% by weight and 3.0-5.0% by weight. In the present invention, as described above, by sufficiently uniformly mixing each component using a kneader or the like,
Water-soluble organic polymer substances, water-absorbing fibrous substances, etc. and calcium silicate crystals become homogeneous and exhibit properties suitable for extrusion molding. By extrusion molding and drying, a calcium silicate molded product having excellent properties can be obtained with high productivity. In addition, the moisture content in the present invention is defined as follows. Moisture content (%)=W/W+S×100 where W indicates water (g) and S indicates solid content (g). Effects of the Invention According to the present invention, the following remarkable effects can be obtained. (1) It becomes possible to easily produce molded bodies of various shapes by extrusion molding from a molding material of calcium silicate crystal secondary particles, which was previously thought to be impossible to extrude as it is. (2) The calcium silicate crystals in the extrusion molding material used are in the form of secondary particles obtained by a hydrothermal synthesis reaction, a water-absorbing fibrous substance is added, and the extrusion molding material contains By reducing the amount of water, a lightweight and high-strength calcium silicate molded body can be obtained. (3) Since only a small amount of combustible material is added, the resulting molded product has high heat resistance. (4) Due to (2) and (3) above, it is particularly suitable as a building material. (5) Since the surface of the molded product is extremely smooth, no surface finishing is required. (6) Extrusion molding is possible with a wide range of moisture content by adjusting the composition. (7) Molded bodies with various cross-sectional shapes can be obtained by simply replacing the extruder mouthpiece, making it easy to produce long molded bodies, thin molded bodies, and molded bodies with complex shapes such as honeycomb shapes. can. (8) Manufacturing by extrusion molding allows continuous manufacturing, resulting in high productivity and easy labor savings. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples. In each example, all parts indicate parts by weight, and all percentages indicate weight %. Example 1 42.3 parts of quicklime (CaO content 95.2%) was slaked in 500 parts of warm water and dispersed in water for 30 minutes using a homomixer. Add 45.2 parts of silica powder (SiO ₂ component 97.0%) with an average particle size of about 5.3 μm to this milk of lime, add water so that the amount of water becomes 96%, and press it to 15
A hydrothermal synthesis reaction was carried out at Kg/cm ² and a temperature of 200.4° C. for 3.5 hours with stirring. The reaction product is xonotlite crystal, and this product is dehydrated under pressure to determine the water content.
An 80% dehydrated cake was obtained. The above raw materials were uniformly and sufficiently mixed in a kneader so that the solid content of this cake was 93% of the solid content of the extrusion molding material, 2% of methyl cellulose, and 5% of powder pulp. Moisture content is 78.8
%. This pasty extrusion molding material was molded using a vacuum extruder and then dried at 160°C for 12 hours. The physical properties of the obtained molded products are shown in Table 1 Sample No.
1 and 2. Example 2 67.7 parts of quicklime (CaO content 95.2%) was slaked in 700 parts of warm water. 72.3 parts of the silica powder used in Example 1 was added to this milk of lime, and water was added so that ^the amount of water became 94%.
A hydrothermal synthesis reaction was carried out at 208.8°C with stirring for 2.5 hours to obtain a xonotlite crystal slurry. This reaction slurry was dehydrated under pressure to obtain a dehydrated cake with a water content of 60%. The raw materials were uniformly and sufficiently mixed using a kneader so that the solid content of this cake was 93.3% of the extrusion molding material, 2.2% of methyl cellulose, and 4.5% of cotton. The moisture content was 58.3%. This was extruded using a vacuum extruder and dried at 150°C for 14 hours. The physical properties of the molded products obtained are shown in Sample Nos. 3 and 4 in Table 1. Example 3 Add 101.5 parts of quicklime (CaO content 95.0%) to 1000 g of hot water
It all went away in the club. Add silica powder (SiO ₂ ingredients) to this.
97.5%, average particle size 3.9μm) was added, then water was added so that the amount of water was 90%, and this was heated under pressure.
A hydrothermal synthesis reaction was carried out at 12 Kg/cm ² and a temperature of 190.7° C. for 8 hours with stirring to obtain a xonotrite crystal slurry. This product slurry was dehydrated to a moisture content of 35
% dehydrated cake was obtained. The raw materials were sufficiently uniformly mixed using a kneader so that the solid content of this cake was 93.5% of the solid content of the extrusion molding material, 2.5% of methyl cellulose, and 4% of powder pulp. The moisture content was 33.5%. This was extruded using a vacuum extruder and dried at 150°C for 14 hours. The physical properties of the molded products obtained are shown in Samples No. 5 and 6 in Table 1. Example 4 38.0 parts of quicklime (CaO content 95.0%) was slaked in 500 parts of warm water. Add silica powder (SiO ₂ component 94
%, average particle size 4.2 μm), then water was added so that the amount of water was 94%, and this was heated under pressure.
A hydrothermal synthesis reaction was carried out at 15 kg/cm ² and a temperature of 200.4° C. with stirring for 2.0 hours to obtain tobermolite crystal slurry. This reaction slurry was dehydrated under pressure,
A dehydrated cake with a moisture content of 70% was obtained. The raw materials were uniformly and sufficiently mixed using a kneader so that the solid content of this cake was 93.3% of the extrusion molding material, 2.1% of carboxymethyl cellulose, and 4.6% of powder pulp. The moisture content was 68.5%. This pasty extrusion material is molded in a vacuum extruder, and then
Dry at ℃ for 13 hours. The physical properties of the molded articles obtained are shown in Sample Nos. 7 and 8 in Table 2.

【table】

[Table] Comparative Example 1 An extrusion molding material was prepared in the same manner as in Example 1 except that powder pulp was not used. Next, when this material was extruded using a vacuum extrusion molding machine in the same manner as in Example 1, the extruded molded product was too soft and cracked, making it impossible to obtain the desired molded product by extrusion molding. It was hot. Comparative Example 2 An extrusion material was prepared in the same manner as in Example 1 except that the content of powder pulp (based on solid content) in the extrusion material was 13%. Next, an attempt was made to mold this material using a vacuum extrusion molding machine in the same manner as in Example 1, but the material had poor fluidity and was difficult to extrude from the die, and the surface of the extruded molded product was rough. However, it was impossible to obtain a desired molded product by extrusion molding. From the above results, extrusion molding cannot be performed smoothly when no water-absorbing fibrous material is used, and when it is used but the amount exceeds 10% (based on solid content), It can be seen that good extrusion molding can only be achieved by the method of the present invention using an extrusion molding material containing a fibrous substance.

Claims (1)

[Scope of Claims] 1 Calcium silicate crystals obtained by hydrothermal synthesis reaction of silicic acid raw materials, lime raw materials, and water are mixed with a water-soluble organic polymer substance and a water-absorbing fibrous substance, and the total water content is determined. A method for producing a calcium silicate molded body, which comprises adjusting the amount of calcium silicate to 20 to 85% by weight and extrusion molding. 2 The amount of water-soluble organic polymer substances used in the total solid content
The manufacturing method according to claim 1, wherein the content is 0.2% by weight or more and less than 5% by weight.