JPH021527B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel aqueous slurry containing silica calcium carbonate composite secondary particles as a constituent component. Conventional technology Silica gel has been known as a typical example of amorphous silica, and is mainly produced by neutralizing an aqueous sodium silicate solution with an acid such as hydrochloric acid or sulfuric acid, precipitating a precipitate, washing with water, and drying. be done. If necessary, it is further activated by heating under reduced pressure. Further, the silica gel is obtained in an amorphous or spherical shape depending on the manufacturing method, and is shaped into a tablet or the like using a binder or the like as necessary. Due to its high hygroscopicity and large specific surface area, it can be used as a desiccant, adsorbent, etc.
Examples include dehydrating agents, deodorants, catalyst carriers, and the like. However, silica gel has the property of rapidly absorbing water and disintegrating when it comes into contact with water, making it impossible or difficult to use in systems where it comes into direct contact with water. Furthermore, silica gel generally has an average pore diameter of 20 to 220 Å, but those with a smaller average pore diameter usually have a bulk density of around 0.7 g/cm ³ , which is much the opposite, and a bulk density of 0.2
If the average pore diameter is around g/cm ³ , the average pore diameter will inevitably be large, usually about 180 to 220 Å. Therefore, silica gel having an average pore diameter of about 20 to 40 Å, which is suitable as an adsorbent for gases, water, etc., has a large bulk density, and its adsorption capacity per unit weight is naturally limited. Moreover, the oil absorption capacity increases as the bulk density and the specific surface area increase, but those with a large specific surface area also have a large bulk density and inevitably lack or are insufficient in oil absorption capacity. Furthermore, silica gel cannot be used as a raw material for fireproof and heat-resistant materials such as heat-resistant glass. Calcium carbonate is usually produced by mechanically crushing shells, chalk, sugar limestone, etc., or by adding water to quicklime to make lime milk, which is then reacted with carbon dioxide gas, and is available from relatively inexpensive sources. In the form of fine particles, it is used for a wide range of purposes, including the same applications as the above-mentioned silica gel, as a raw material for cement, as a raw material for various chemicals, and for neutralization. Problems to be Solved by the Invention The present invention provides a new method to replace the above-mentioned known silica gel by dispersing in water secondary particles of a composite consisting of crystal-like amorphous silica in appearance and ultrafine calcium carbonate attached to the silica. The present invention provides a new aqueous slurry. Means for Solving the Problems Namely, the present invention has at least two surfaces in a symmetrical relationship, a length of about 1 to 50μ and a diameter of about 0.02 to
Silica-calcium carbonate composite primary particles are composed of crystal-like amorphous silica in appearance and having a thickness of 0.5μ and a length at least 10 times the thickness and ultrafine calcium carbonate attached to the silica. It is formed by intertwining many irregularly three-dimensionally, about 10 to 150μ
The present invention relates to an aqueous slurry made by dispersing secondary particles having a diameter of , and having a substantially spherical shell shape, in water. In this specification, the above-mentioned composite primary particles constituting the slurry of the present invention will be referred to as "silsite", and the composite secondary particles will be referred to as "silsite". Further, the primary particles of amorphous silica that are crystal-like in appearance, which are one of the components constituting the above-mentioned composite, are called "opsil" and the secondary particles thereof are called "opsil." Silcite consists of opsil and extremely fine calcium carbonate attached to it. Opsil has at least two symmetrical faces and about 1
It has a length of ~500μ, a thickness of about 50A to about 1μ, and a size where the length is at least 10 times the thickness. As a result of X-ray diffraction analysis, no diffraction peaks were observed and it was found to be amorphous, and chemical analysis after ignited dehydration showed that the SiO ₂ content exceeded 98% by weight, and electron microscopy revealed that it was amorphous. It is characterized by having at least two symmetrical faces and a crystal-like appearance despite its crystalline texture. The calcium carbonate present attached to Opsil is extremely fine particles of about 2μ or less, and is attached to Opsil in a state that cannot be easily separated. For example, if silcite is dispersed in water at a concentration of 5% by weight,
After stirring for a minute and leaving it to stand, attempts to separate the silica (opsil) and calcium carbonate that make up silcite by sedimentation due to the difference in specific gravity between the two result in no separation at all, and the two adhere to each other due to chemical or physical forces. It is recognized that there are The fact that silsite is an amorphous silica-calcium carbonate complex is shown by the fact that the diffraction peak (2θ) characteristic of calcium carbonate is 23.0° as a result of X-ray diffraction analysis.
29.4° and 36.0° or 23.0°, 24.8°, 27.0°, 29.4°,
32.8° and 36.0°, and as a result of chemical analysis after ignited dehydration, the main components are SiO ₂ and CaO, and electron microscopic observation shows that it is composed of opsils, which have a crystal-like appearance, and fine particles. This is confirmed by the fact that The unique appearance of opsyl, which constitutes silsite, is brought about by the fact that it is derived from silicate crystals and is converted into amorphous silica while retaining the remains of the crystals. Therefore, opsil has substantially the same external shape and size as the silicate crystal that is the source crystal. For example, opsils derived from rectangular calcium silicate crystals such as wollastonite, zonotrite, and phosciasite have a rectangular outer diameter. tobermolite, gyrolite, α-
Dicalcium silicate hydrate (α-
Opsil derived from plate-shaped calcium silicate crystals such as C ₂ SH) has a plate-like external shape. The opsile, which is in the form of an isometric strip or a plate, has a length of about 1 to
500μ, a thickness of about 50A to 1μ, and a length that is at least 10 times the thickness. A rectangular optic derived from a zonotrite crystal retains the crystal habit of the crystal and is usually about 1 to 50μ in length, about 100Å to
It has a thickness of 0.5 μ and a width of about 100 Å to 2 μ, and the length is about 10 to 5000 times the thickness. A plate-shaped optic derived from tobermolite crystal retains the crystal habit of the crystal, and has a length of about 1 to 50μ, a thickness of about 100Å to 0.5μ, and a thickness of about 100Å to 0.5μ.
It has a width of 0.2 to 20μ and a length of about 10 to 5000 times the thickness. The strip-shaped opsyl derived from wollastonite crystal retains the crystal habit of the crystal and has a crystal habit of about 1~
500μ length, about 100Å~1μ thickness and about 100Å~
It has a width of 5μ and a length approximately 10 to 5000 times the thickness. A plate-shaped optic derived from a gyrolite crystal retains the crystal habit of the crystal and has a length of about 1 to 50 μ, a thickness of about 100 Å to 0.5 μ, and a width of about 1 to 20 μ, and the length is equal to the thickness. 10 to 5000 times. The plate-shaped opsyl derived from α-dicalcium silicate hydrate crystal retains its crystal habit, has a length of about 1 to 300μ, a thickness of about 500Å to 1μ, and a thickness of about 1 to 1μ.
It has a width of 50μ and a length 10 to 5000 times the thickness. The chemical composition of Opsil after ignited dehydration (Ig. loss about 4-7% by weight) is as follows, and its physical properties are as shown in Table 1 below in comparison with silica gel. Chemical composition of opsil (wt%) SiO ₂ >98.0 Al ₂ O ₃ < 1.0 Fe ₂ O ₃ < 0.01 CaO < 0.02

[Table] However, in Table 1, RD ⁽¹⁾ is regular density,
ID ⁽²⁾ indicates intermediate density, LD ⁽³⁾ indicates low density, and encyclopedia
of Chemical Technology (Encyclopedia
of Chemical Technology) Volume 18, 1969, No. 61
Quoted from page 67. Further, each physical property in Table 1 was measured by the following method. Bulk density: 50 g/cm ² Using the piston-cylinder method, 10 g of powder is placed in a cylinder with a cross-sectional area of 5 cm ² , a load of 250 g is applied to the cylinder, and the volume is determined using the following formula. 10 (g)/volume (cm ³ ) = bulk density true specific gravity: using a Beckman air comparison hydrometer,
Determined by He gas replacement. Average pore size: Based on BET nitrogen adsorption method. Specific surface area: Based on BET nitrogen adsorption method. Pore volume: Based on BET nitrogen adsorption method. Particle size: Based on optical microscope/electron microscope. Oil absorption: Dioctyl phthalate (C ₆ H ₄
(COOC ₈ H ₁₇ ) ₂ ) is dropped into 100 g of powder to absorb oil, and the amount of oil is shown when viscosity suddenly appears. Hygroscopicity: Put the powder in a container with relative humidity of 100% 25
It is maintained at ℃ and allowed to adsorb until it reaches an equilibrium state, and is expressed in weight %. However, each value in the table is a bulk density of 0.1 g/cm 3 as opsil, and a bulk density of 0.1 g/cm ³ as RD.
0.7g/cm ³ , bulk density 0.4g/cm ³ as ID and LD
This is data when a bulk density of 0.15 g/cm ³ is used. As is clear from Table 1 above, Opsil has small average pores of about 20 to 40 Å, which are suitable for adsorption of gas and water, and has a large specific surface area, although it has a small bulk density. Therefore, it exhibits excellent adsorption ability for gases, water, etc., and also has excellent oil absorption ability. Opsil also has excellent water resistance and does not disintegrate even when immersed in water, so it can be used very advantageously even in systems where it comes into direct contact with water. Furthermore, Opsil has a low thermal conductivity and can be sintered at temperatures up to 1000°C. In addition, it has a near-neutral pH of 6 to 7, and has excellent chemical resistance, and is not decomposed by acids such as hydrochloric acid. These properties are extremely advantageous compared to the original calcium silicate crystal, which has a high pH of 10 to 11 and is subject to decomposition by acids such as hydrochloric acid, which limits its use. be. Silsite, which is a component of the aqueous slurry according to the present invention, is formed by a large number of silsites being irregularly bonded together in a three-dimensional manner, and has a diameter in the range of about 10 to 150μ and is hollow or rough inside. Based on this shape, a molded product that is lightweight and has excellent mechanical strength can be produced by simply molding an aqueous slurry and drying it without using any binder. It has a unique moldability that gives . More specifically, when the aqueous slurry of silsite of the present invention is molded, the pressure during molding compresses the secondary particles at least in the direction of the pressure, and the compressed particles become entangled with each other, and when dried, In the above state, an integrally formed molded body is obtained. The bulk density of the molded product can be arbitrarily adjusted by adjusting the pressure during molding, and can be adjusted over a wide range.
Preferably the bulk density is from about 0.1 g/cm ³ to about 1.0 g/cm 3
cm ³ and the obtained molded body is 0.1 to 0.4
It has a bending strength ^of about ³ to 30Kg/cm2 at a low bulk density of about g/ ^cm3 , and a high bending strength of about 20 to 100Kg/cm2 at a bulk density of 0.4g/ ^cm3 to 1.0g/ ^cm2 . has.
This molded body is useful as a heat-resistant material, a filter material, a catalyst carrier, and the like. The aqueous slurry of silcite of the present invention is preferably prepared with a water to solids weight ratio in the range of 8 to 50:1, and the slurry may optionally include asbestos, glass fiber, rock wool, synthetic fiber, natural fiber, etc. fiber, pulp,
Various additives such as fibrous reinforcing agents such as carbon fiber and stainless fiber, alumina sol, colloidal silica sol, clay, cement, coloring agents, and fillers can be added, thereby improving the properties of the molded article. The silcite constituting the aqueous slurry of the present invention can be produced from various natural or synthetic silicate crystals having a SiO ₄ tetrahedral lattice or chain structure. The method for producing it is not particularly limited and any method can be adopted, but it is most advantageously produced as follows using calcium silicate crystals as a raw material. That is, it is produced by bringing calcium silicate crystals into contact with carbon dioxide gas in the presence of moisture. The greatest feature of this production method is that calcium silicate, which constitutes the calcium silicate crystal, can be converted into amorphous silica and calcium carbonate without substantially changing the external shape of the calcium silicate crystal. Calcium silicate crystals that are the origin crystals include wollastonite calcium silicate crystals such as wollastonite, zonotrite, phossiyaite, hillebrandite, and rosenhanite; tobermolite calcium silicate crystals such as tobermolite;
Included are gyrolite-based calcium silicate crystals such as gyrolite, trascotite, and lierite, γ-dicalcium silicate-based calcium silicate crystals such as calciochondrodite, circoniaite, and ahubilite, and α-dicium silicate hydrate. These isocrystals are used as source materials in the form of secondary particles. Since the external shape of the crystal is inherited substantially unchanged, the form of the original crystal is also inherited substantially unchanged by the silcite and the opsile that constitutes it. i.e. primary particles of calcium silicate crystals (having at least two symmetrical faces, having a length of 1 to 500 μ and a thickness of 50 Å to 1 μ, the length being at least 10 times the thickness) ) substantially spherical shell-shaped secondary particles with a diameter of about 10 to 150 μ, which are formed by irregularly entangling a large number of particles in a three-dimensional manner, have the form or structure of the secondary particles as they are. Silcite is obtained. Such calcium silicate crystal secondary particles used for producing silcite are all known and can be produced by known methods. For example, according to the method described in Japanese Patent Publication No. 45-25771,
Spherical shell-like calcium silicate crystals are formed by crystallizing a raw material slurry in which silicic acid raw materials and lime raw materials are dispersed in water, along with additives such as reinforcing agents as necessary, through a hydrothermal synthesis reaction while stirring. An aqueous slurry of secondary particles is obtained. As the silicic acid raw material for obtaining the above-mentioned calcium silicate crystals, various materials containing silicic acid as a main component such as natural amorphous silicic acid, silica sand, diatomaceous earth, clay, slag, white clay, fly ash, perlite, white carbon, and silicon dust are used. It can be used alone or in combination of two or more. As the lime raw material, various materials having lime as a main component, such as quicklime, slaked lime, carbide residue, and cement, can be used alone or in combination of two or more. These raw materials are usually blended so that the molar ratio of CaO:SiO ₂ is in the range of about 0.5 to 3.5:1. Additives such as reinforcing agents such as glass fibers, ceramic fibers, asbestos, rock wool, nylon, vinylon, natural fibers, pulp, stainless fibers, carbon fibers, and coloring agents may be blended with the above raw materials as necessary. In the above, the amount of water can be varied over a wide range, and is generally about 3.5 to 25 times the total weight of solids. The reaction temperature is the saturation temperature of water vapor pressure, and the reaction is usually completed in about 0.5 to 20 hours.
Calcium silicate crystals having various degrees of crystallinity can be obtained depending on the molar ratio of CaO:SiO ₂ , reaction pressure, temperature, time, etc. The calcium silicate crystals include, depending on their crystal system, zonotrite, tobermolite, phosiyaite, gyalolite, α-dicalcium silicate hydrate, and the like. Furthermore, by further firing the above-mentioned zonotrite crystals at about 1000°C, the crystals constituting the zonotrite crystals can be made into wollastonite without changing its shape (Japanese Patent Publication No. 50-29493
issue). Silsite can be obtained by forcibly carbonating calcium silicate crystals in the form of spherical secondary particles obtained as described above by bringing them into contact with carbon dioxide gas in the presence of water. The carbonation is carried out by introducing carbon dioxide gas into the reaction system and bringing the crystals into contact with the carbon dioxide gas in the presence of moisture. This can be done, for example, by placing calcium silicate crystals in a suitable airtight container and introducing carbon dioxide gas under high humidity or a humid atmosphere, or by immersing calcium silicate crystals in water or carbonated water and then introducing carbon dioxide gas. It can be carried out by a method. Of course, when calcium silicate crystals are obtained in the form of an aqueous slurry of secondary particles, carbon dioxide gas may be directly introduced therein. This carbonation can be carried out at room temperature as long as carbon dioxide gas is introduced into the system.
Although the reaction proceeds satisfactorily under normal pressure, it is preferable to carry out the reaction under increased pressure (gauge pressure of up to about 10 kg/cm ² ), which speeds up the carbonation rate and allows the reaction to be completed in a short time. Become. The amount of carbon dioxide used is stoichiometric or more. When carbonating calcium silicate crystals by immersing them in water, the carbonation rate can also be increased by stirring the reaction system. The ratio of water to calcium silicate crystals used is usually 1 to 50:1, preferably 1 to 25:1 (weight ratio). The rate of carbonation differs slightly depending on the crystallinity of the calcium silicate that makes up the raw material, but for example, when carbonating zonotrite crystals, which are recognized to have the slowest carbonation rate, it is necessary to add water to their dry weight. By increasing the amount by about 2 to 6 times, the reaction is completed in about 4 to 10 hours. Also, the amount of water added is 5
If the pressure is doubled and the reaction system is pressurized to 2Kg/cm ² (gauge pressure), the reaction will normally be completed in around 1 hour, but if this pressurization condition is 3Kg/cm ² (gauge pressure), it will take about 30 minutes. It is recognized that the reaction is completed in a short time. The carbonation reaction proceeds as shown in the following reaction formula depending on the type and crystallinity of calcium silicate crystals used as raw materials. xCaO·SiO ₂ ·mH ₂ O+CO ₂ →CaCO ₃ +SiO ₂ ·nH ₂ O However, in the above formula, x is 0.5 to 3.5. As a result of the above, calcium silicate crystals are converted into amorphous silica and ultrafine crystals of calcium carbonate without substantially changing the external shape of the primary particles and therefore without changing the secondary particle morphology. In other words, it forms the skeletal structure of primary calcium silicate crystals.
The chain structure of SiO ₄ tetrahedrons is maintained, and the chain structure produces amorphous silica (opsil) having a crystalline appearance and extremely fine calcium carbonate attached thereto. Calcium carbonate is an ultrafine particle of about 2 microns or less, and is attached to Opsil in a state that cannot be easily separated by chemical or physical force. Moreover, since there is no change in the external shape of the raw material crystals even after the above-mentioned carbonation, silcite can be obtained from the spherical shell-like secondary particles. Examples Reference examples and examples are given below to explain the present invention in more detail. Physical X-ray diffraction diagrams, electron micrographs, and scanning electron micrographs obtained in each reference example and example are shown in the drawings. FIGS. 1A and 1B are X-ray diffraction patterns of zonotrite crystal, which is a starting material, and silsite obtained by carbonating the crystal, respectively. These were recorded by using an X-ray diffractometer to generate X-rays with a wavelength of 1.5418 Å at a Cu target, irradiating the sample with this, and determining the diffraction angle and diffraction intensity. Figures 2 and 3 are electron micrographs at a magnification of 20,000 times, and in each figure, A is a photograph of calcium silicate crystals, which are the starting materials, and B is a photograph of silsite obtained therefrom. Figures 4 and 5 are scanning electron micrographs (600x magnification). In each figure, A is a photograph of spherical secondary particles of calcium silicate crystals, which are the starting materials, and B is a photograph of silsite obtained by carbonating the secondary particles. Reference example 1 Quicklime as lime raw material and 350 as silicic acid raw material
Uses silica powder from Metsuyu. A raw material slurry is prepared by dispersing the lime and silicic acid in water at a molar ratio of 0.98:1 and setting the water to solids ratio (weight) to 12:1. The raw material slurry is charged into an autoclave, heated to 191°C, and subjected to a hydrothermal reaction with stirring for 8 hours under a saturated steam pressure of 12 kg/cm ² to obtain a slurry of zonotrite crystals. The X-ray diffraction diagram of the obtained crystal is as shown in FIG. 1A, and shows diffraction peaks (2θ) characteristic of zonotrite crystals at 12.7°, 27.6°, and 29.0°. Its composition after ignition is as follows. SiO ₂ 48.88% CaO 45.60 Al ₂ O ₃ 0.26 Fe ₂ O ₃ 0.54 Ig.loss 4.51 99.79 As shown in Figure 4A, the slurry obtained above contained many zonotrite needle crystals as shown in Figure 4A as a result of scanning electron microscopy. It is composed of a large number of substantially spherical zonotrite secondary particles, which are irregularly intertwined in three dimensions and have a diameter in the range of about 10 to 60 microns, dispersed in water. The secondary particles are approximately 95.6
% porosity. Next, the slurry is dried at 150° C. and pulverized to separate the secondary particles into primary particles to obtain a fine white powder.
The electron micrograph is shown in FIG. 2A. From the figure, the above primary particles have at least a symmetrical relationship 2
It has two sides, about 1 to 20μ in length, and about 0.02 to 0.1μ in thickness.
It can be seen that it has a width of about 0.02 to 1.0μ, and a length that is at least about 10 times the thickness. The primary particles have a specific surface area of approximately 50 m ² /g. Reference example 2 Slaked lime as a lime raw material and 350 as a silicate raw material
Uses silica powder from Metsuyu. A raw material slurry is prepared by dispersing these in water at a molar ratio of lime to silicic acid of 0.80:1, and setting the water to solids ratio (weight) to 12:1. The raw material slurry is charged into an autoclave, heated to 191°C, and subjected to a hydrothermal reaction with stirring under a saturated steam pressure of 12 kg/cm ² for 5 hours to obtain a slurry of tobermolite crystals. As a result of X-ray diffraction analysis, the obtained crystal has an angle of 7.8°,
It shows diffraction peaks (2θ) characteristic of tobermolite crystals at 29.0° and 30.0°. Its composition after ignition is as follows. SiO ₂ 48.38% CaO 38.55 Al ₂ O ₃ 0.31 Fe ₂ O ₃ 0.45 Ig・loss 11.36 99.05 The slurry obtained above was observed as a plate-shaped crystal of tobermolite as shown in Figure 5A as a result of scanning electron microscopy. It is composed of a large number of substantially spherical tobermolite secondary particles, which are formed by irregularly intertwining in three dimensions and have a diameter in the range of about 10 to 60μ, dispersed in water. There is. The secondary particles are approximately 94.0
% porosity. Next, the slurry is dried at 150° C. and pulverized to separate the secondary particles into primary particles to obtain a fine white powder.
The electron micrograph is shown in FIG. 3A. From the figure, the primary particle has at least two symmetrical surfaces, a length of about 1 to 20 μm, and a thickness of about 0.02 to 20 μm.
It can be seen that the length is at least about 10 times the thickness, with dimensions of 0.1μ and about 0.2-5.0μ. The primary particles have a specific surface area of about 61 m ² /g. Example 1 Slurry of zonotrite crystals obtained in Reference Example 1
250g was dehydrated to a water to zonotrite crystal solid content ratio of 5/1, and this was placed in a sealed container with a humid atmosphere and carbon dioxide gas was pressurized to bring the internal pressure to 3Kg/cm ² .
The reaction was allowed to proceed for 30 minutes. In this way, amorphous silica-calcium carbonate composite secondary particles (silsite) are obtained. The analysis results are as follows. Composition (%) SiO ₂ 36.04 CaO 33.54 Al ₂ O ₃ 0.18 Fe ₂ O ₃ 0.38 Ig・loss 28.87 Total 99.01 The X-ray diffraction results are as shown in Figure 1B. All the peaks based on this have disappeared, and instead they are 23.0°, 29.4°,
Diffraction peak of calcium carbonate crystal at 36.0° (2θ)
It is confirmed that the composite secondary particles are composed of amorphous silica and calcium carbonate. Furthermore, the results of observation of the composite secondary particles with a 600x scanning electron microscope are shown in FIG. 4B. From the figure, this composite secondary particle is formed by a large number of amorphous silica-calcium carbonate composite primary particles entangled three-dimensionally on the irregular side, and has a diameter in the range of about 10 to 60μ. It can be seen that it exhibits a spherical shell shape.
It can be seen that the structure and morphology of these secondary particles are substantially the same as those of the zonotrite secondary particles (FIG. 4A) used as the starting material, and are maintained as they are even after carbonation. Further, the primary particles constituting the above-mentioned secondary particles have a length of about 1 to 20 μm, about 0.02 to 0.1 μm, and have at least two symmetrical surfaces, as shown in FIG. 2B as a result of electron microscopic observation. Amorphous silica having a thickness of about 0.02 to 1.0 μ and a length of at least 10 times the thickness.
It had a morphology in which calcium carbonate microparticles having the following ultrafine particle morphology were attached. Furthermore, the second
In Figure B, the primary particles of zonotrite needle crystals obtained in Reference Example 1 are charged into a closed pressure vessel together with 5 times the weight of water, and carbon dioxide gas is pressurized into the vessel at room temperature.
This is an electron micrograph of amorphous silica-calcium carbonate composite particles (silsite) obtained by carbonation for about 30 minutes while maintaining the internal pressure at 3 Kg/cm ² . Even after dispersing the composite secondary particles in water to a concentration of 5% by weight and stirring for 20 minutes, the amorphous silica and calcium carbonate constituting the secondary particles could not be separated by sedimentation. The properties of the silsite obtained above are shown below. Bulk density 0.110g/cm ³ Specific surface area 60m ² /g Oil absorption 400c.c./g Porosity 95.5% However, the porosity was calculated according to the following table. Porosity=(1-apparent specific gravity of silsite/true specific gravity of silsite)×100 100 parts by weight of the silsite powder obtained above and 2 parts by weight of glass fibers were dispersed in 800 parts by weight of water, and the present invention was prepared. An aqueous slurry is obtained. The resulting aqueous slurry was then 40 x 120 x 150
(mm), press dehydrated, remove from the mold, and dry at 105℃ for 24 hours. A molded body is thus obtained. Its physical properties are as follows. Bulk density 0.33g/cm ^3Porosity 86.4% Heat resistance at 950℃ No change Bending strength 13Kg/cm ^2Example 2 Slurry of tobermolite crystals obtained in Reference Example 2
250g was dehydrated, the water to tobermolite crystal solid content ratio was 5/1, and this was placed in a container with a humid atmosphere.
Carbon dioxide gas was introduced under pressure to give an internal pressure of 3 kg/cm ² , and the reaction was carried out for about 30 minutes. In this way, amorphous silica-calcium carbonate composite secondary particles (silsite) are obtained. The analysis results are as follows. Composition (%) SiO ₂ 39.77 CaO 31.43 Al ₂ O ₃ 0.24 Fe ₂ O ₃ 0.40 Ig.loss 27.42 Total 99.26 Also, according to the X-ray diffraction results, all peaks based on calcium silicate crystals before carbonation have disappeared. , instead, the diffraction peaks (2θ) of calcium carbonate crystals are at 23.0°, 24.8°, 27.0°, 29.4°, 32.8° and 36.0°.
It is confirmed that the composite secondary particles are composed of amorphous silica and calcium carbonate. The results of the 600x scanning electron microscope observation of the composite secondary particles are shown in FIG. 5B. From the figure, this composite secondary particle is formed by a large number of amorphous silica-calcium carbonate composite primary particles irregularly entangled in a three-dimensional manner, and has a diameter in the range of approximately 10 to 60μ. It can be seen that it exhibits a spherical shell shape. It can be seen that the structure and morphology of the secondary particles are substantially the same as the tobermolite secondary particles used as the starting material, and are maintained as they are even during carbonation.
Further, as shown in FIG. 3B, the primary particles constituting the above-mentioned secondary particles have at least two surfaces in a symmetrical relationship, and have approximately 1 to
20μ length, about 0.02~0.1μ thickness and about 0.2~5.0μ
It had a morphology in which calcium carbonate microparticles in the form of ultrafine particles of about 2 μm or less were attached to amorphous silica having a width of 100% and a length of 10 times or more the thickness. In addition, FIG. 3B shows that the tobermolite plate-like crystal primary particles obtained in Reference Example 2 were charged into a closed pressure vessel together with 5 times the weight of water, and carbon dioxide gas was pressurized into the vessel at room temperature. Amorphous silica-calcium carbonate composite particles (silsite) obtained by carbonation for about 30 minutes while maintaining the internal pressure at 3 Kg/cm ²
This is an electron micrograph. Even when the composite secondary particles were dispersed in water to a concentration of 5% by weight and stirred for 20 minutes, the amorphous silica and calcium carbonate constituting the secondary particles could not be separated by sedimentation. The properties of the silsite obtained above are shown below. Bulk density 0.100g/cm ³ Specific surface area 52m ² /g Oil absorption 380c.c./g Porosity 96.0% 100 parts by weight of the silcite powder and 2 parts by weight of glass fiber obtained above were dispersed in 800 parts by weight of water. Then, an aqueous slurry of the present invention is obtained. Next, the obtained aqueous slurry is molded in the same manner as in Example 1 to obtain a molded article of the present invention. Its physical properties are as follows. Bulk density 0.32g/cm ³ Porosity 87.0% Heat resistance at 950℃ No change Compressive strength 12Kg/cm ² Bending strength 7Kg/cm ² Example 3 The slurry of zonotrite crystals obtained in Reference Example 1 was heated at 1000℃ for 1 hour. Calcined to obtain β-wollastonite crystals, 250g of which was adjusted to a solid ratio of water to β-wollastonite crystals of 5/1, placed in a container with a humid atmosphere, and carbon dioxide gas was injected under pressure to reduce the volume to 3Kg/cm. The internal pressure was set to ² , and the reaction was carried out for about 30 minutes. In this way, amorphous silica-calcium carbonate composite secondary particles (silsite) are obtained. The analysis results are as follows. Composition (%) SiO 36.00 CaO 33.58 Al ₂ O ₃ 0.15 Fe ₂ O ₃ 0.35 Ig.loss 28.92 Also, according to the X-ray diffraction results, all the peaks based on calcium silicate crystals before carbonation disappeared, and instead Diffraction peaks (2θ) of calcium carbonate crystals at 23.0°, 24.8°, 27.0°, 29.4°, 32.8° and 36.0°
It is confirmed that the composite secondary particles are composed of amorphous silica and calcium carbonate. Furthermore, the results of scanning electron microscopy of the composite secondary particles are similar to those shown in FIGS. 4B and 5B, and the composite secondary particles are composed of a large number of amorphous silica-calcium carbonate composite primary particles. It can be seen that they are formed in a regular three-dimensional entanglement and exhibit a substantially spherical shell shape with a diameter in the range of about 10 to 60 microns. It can be seen that the structure and morphology of these secondary particles are substantially the same as the β-wollastonite secondary particles used as the starting material, and are maintained as they are even during carbonation. Further, as a result of electron microscopy observation, the primary particles constituting the above-mentioned secondary particles are at least two particles in a symmetrical relationship.
It has two sides, a length of about 1 to 20μ, a thickness of about 0.02 to 0.1μ, and a width of about 0.02 to 1.0μ, and the length is equal to the thickness.
Amorphous silica with a size that is 10 times more
It had a morphology in which calcium carbonate microparticles having the morphology of ultrafine particles of 2μ or less were attached. Even when the composite secondary particles were dispersed in water to a concentration of 5% by weight and stirred for 20 minutes, the amorphous silica and calcium carbonate constituting the secondary particles could not be separated by sedimentation. The characteristics of the silsite obtained above are shown. Bulk density: 0.108 g/cm ³ Oil absorption: 300 c.c./g The silsite obtained above is dispersed in water at a water to solid weight ratio of 5:1 to obtain an aqueous slurry of the present invention. This material has the ability to be molded into a lightweight molded product with excellent mechanical strength simply by dehydration molding and drying. Reference example 3 Slaked lime as a lime raw material and 350 as a silicic acid raw material
Uses silica powder from Metsuyu. A raw material slurry is prepared by dispersing these in water at a molar ratio of lime to silicic acid of 0.98:1, and setting the water to solids ratio (weight) to 12:1. The raw material slurry is charged into an autoclave, heated to 213° C., and subjected to a hydrothermal reaction under a saturated steam pressure of 20 Kg/cm ² with stirring for 12 hours to obtain a slurry of zonotrite crystals. As a result of scanning electron microscopy, the slurry obtained above was found to be a substantially spherical shell-like secondary zonotrite formed by a large number of irregularly entangled zonotrite needle crystals and having a diameter in the range of approximately 10 to 150μ. It is composed of a large number of particles dispersed in water. The secondary particles have a porosity of about 93%. Next, the slurry is dried at 150° C. and pulverized to separate the secondary particles into primary particles to obtain a fine white powder.
As observed by electron microscopy, the above primary particles have at least two symmetrical surfaces and have a length of approximately 5 to 50 μm.
It had a thickness of about 0.02 to 0.5 microns, a width of 0.02 to 1.0 microns, and a length at least about 10 times the thickness. The primary particles have a specific surface area of about 50 m ² /g Example 4 Slurry of zonotrite crystals obtained in Reference Example 3
250g was dehydrated to a water to zonotrite crystal solid content ratio of 5/1, and this was placed in a sealed container with a humid atmosphere and carbon dioxide gas was pressurized to bring the internal pressure to 3Kg/cm ² .
The reaction was allowed to proceed for 30 minutes. In this way, amorphous silica calcium carbonate composite secondary particles (silsite) are obtained. It is confirmed from X-ray diffraction that the composite secondary particles are composed of amorphous silica and calcium carbonate. Furthermore, scanning electron microscopy revealed that the composite secondary particles are formed by a large number of amorphous silica calcium carbonate composite primary particles irregularly entangled in a three-dimensional manner, and have a diameter in the range of approximately 10 to 150μ. It had a substantially spherical shell shape. It can be seen that the structure and morphology of these secondary particles are substantially the same as those of the zonotrite secondary particles used as the starting material, and are maintained as they are even during carbonation. Further, as a result of electron microscopic observation, the primary particles constituting the above-mentioned secondary particles have at least two symmetrical surfaces, and have approximately 5 to
50μ length, about 0.02~0.5μ thickness and about 0.02~
It has a form in which calcium carbonate microparticles in the form of ultrafine particles of approximately 2μ or less are attached to amorphous silica with a width of 1.0μ and a length that is 10 times or more the thickness. Was. Even when the composite secondary particles were dispersed in water to a concentration of 5% by weight and stirred for 20 minutes, the amorphous silica and calcium carbonate constituting the secondary particles could not be separated by sedimentation. The properties of the silsite obtained above are shown below. Bulk density: 0.120 g/cm ³ Oil absorption: 360 c.c./g The aqueous slurry of the present invention is obtained by dispersing the silcite obtained above in water such that the weight ratio of water to solid content is 5:1. This material has the ability to be molded into a lightweight molded product with excellent mechanical strength simply by dehydration molding and drying.

[Brief explanation of drawings]

FIG. 1 is an X-ray diffraction diagram, in which A shows the starting material zonotrite crystal and B shows the silsite obtained from the crystal. FIGS. 2 and 3 are electron micrographs, and in each figure, A indicates a calcium silicate crystal, which is a starting material, and B indicates a silsite obtained from the crystal. Figures 4 and 5 are scanning electron micrographs (magnification: 600x), and in each figure, A indicates spherical secondary particles of calcium silicate crystals, which are the starting materials, and B indicates secondary particles obtained from the secondary particles. Shows silcite.

Claims (1)

[Claims] 1. Crystal-like amorphous in appearance, having at least two planes in a symmetrical relationship, having a length of about 1 to 50 microns and a thickness of about 0.02 to 0.5 microns, with the length being at least 10 times the thickness. A silica-calcium carbonate composite primary particle composed of silica and ultrafine calcium carbonate attached to the silica is formed by irregularly entangling in a three-dimensional manner, and has a diameter of about 10 to 150μ, An aqueous slurry made by dispersing secondary particles that are substantially spherical in water.