JPH0116783B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a molding material containing silica-calcium carbonate composite primary 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 is made by dispersing in water a composite consisting of a new crystal-like amorphous silica that replaces the above-mentioned known silica gel and ultrafine calcium carbonate attached to the silica. The object of the present invention is to provide a novel molding material that can be molded without using any binder or the like, thereby producing a lightweight and strong molded product. Means for solving the problem According to the present invention, at least two
It has two sides, a length of about 1 to 300μ, and a length of about 0.02 to
It has a thickness of about 1μ and the length is at least 10μ thick
A molding material is provided in which primary particles of a silica-calcium carbonate composite composed of amorphous silica having a crystal-like appearance and ultrafine calcium carbonate attached to the silica are dispersed in water. In this specification, the silica-calcium carbonate composite primary particles constituting the molding material of the present invention will be referred to as "silsite". The primary particles of amorphous silica, which is one of the constituents of silsite, 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 as a result of electron microscopy observation, it is composed of opsil and fine particles that have a crystal-like appearance. Confirmed by. 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 phosiadite have a rectangular outer shape. 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. These opsiles, which are strip-shaped, plate-shaped, etc., have a length of about 1~
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 50 μ, a thickness of about 100 Å to 0.5 μ, and a width of about 0.2 to 20 μ. It is approximately 10 to 5,000 times larger than the original size. 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, RD ⁽¹⁾ in Table 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 was maintained at ℃ and adsorbed until it reached an equilibrium state, and the adsorption 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 0.7 as RD.
g/cm ³ , a bulk density of 0.4 g/cm ³ as ID, and a bulk density of 0.15 g/cm ³ as LD, respectively. As is clear from Table 1 above, Opsil has a small average pore diameter of about 20 to 40 Å, which is suitable for adsorbing gas and water, even though it has a small bulk density. It exhibits excellent adsorption ability for water, etc., and also has excellent oil absorption ability. Opsil also has excellent water resistance and does not disintegrate in any way 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, around neutrality of 6 to 7
It has a pH value and has excellent chemical resistance, and is not decomposed by acids such as hydrochloric acid. These properties are advantageous compared to the source crystal, 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. . Silcite, which constitutes the molding material of the present invention, is composed of opsil having the above-mentioned unique particle shape and characteristics and ultrafine calcium carbonate that is physically or chemically attached to the opsil. It can be molded in the form of a slurry without using any binder, and it has unique properties that allow it to produce molded products that are lightweight and strong, and the molded products obtained by molding this have the characteristics of Opsil. It can be used as an alternative to applications where silica gel has traditionally been used, and it can also be used in applications where silica gel cannot be used, and by utilizing the properties of calcium carbonate, it can be used as an alternative to applications where calcium carbonate has been used. can. Typical examples include various fillers, desiccants, adsorbents, deodorants, filter agents, additives for adhesives, heat resistant agents, matting agents for paper manufacturing, emulsifiers for cosmetics,
Anti-wear agents, heat insulating agents, thickeners, pigments, toothpaste, agricultural carriers, medical carriers, catalysts, catalyst carriers, fillers for gas chromatography, excipients, anti-caking agents,
It is useful for applications such as volatile substance fixatives, molecular sieves, and heat-resistant glass raw materials. It is particularly useful as a heat-resistant material, a heat-retaining material, a superagent, a catalyst carrier, etc. In obtaining the above-mentioned molded article, the molding material of the present invention is
It is usually desirable to form an aqueous slurry with a water to solids ratio (by weight) of 4 to 50:1. In addition, the slurry may optionally contain fibrous reinforcing agents such as asbestos, glass fiber, ceramic fiber, rock wool, synthetic fiber, natural fiber, pulp, carbon fiber, metal fiber, stainless fiber, alumina sol, colloidal silica sol, clay, etc. Various additives such as cement, colorants, fillers, etc. can be added, thereby imparting further useful properties. The molded body obtained is usually 0.1
It has a low bulk density of about 0.4 g/cm ³ and a high bending strength of about 3 to 30 Kg/cm ² . It is also possible to increase the above-mentioned bulk density, and a molded article having greater mechanical strength in proportion to the bulk density can be obtained. For example, a molded product having a bulk density of 0.4 g/cm ³ to 1.0 g/cm ³ has a high bending strength of about 20 to 100 Kg/cm ² . The reason why the above-mentioned molded product is so lightweight and has excellent mechanical strength is that the silcite particles are firmly bonded to each other and have a large porosity. This porosity increases as the density decreases. 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 network 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 origin crystals include wollastonite calcium silicate crystals such as wollastonite, zonotrite, phosiyaite, 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-dicalcium silicate hydrate. These crystals are used as a source material in the form of primary particles, and are passed on substantially unchanged to silcite or opsyl, which constitutes it, without damaging the external shape of the crystal.
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) ), silsite, that is, opsil which has the remains of the above-mentioned crystal particles as it is, and calcium carbonate present attached thereto are obtained. The above-mentioned calcium silicate crystalline primary particles used for producing silcite can be prepared by known methods, such as Japanese Patent Publication No. 45-25771, Japanese Patent Publication No. 4040-1982, Japanese Patent Publication No. 1953-1973, and U.S. Patent No. 2699097. It can be easily produced by pulverizing spherical shell-like secondary particles or molded bodies of calcium silicate crystals obtained by the method described in US Pat. No. 2,665,996 and the like. 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 vinylon, natural fibers, pulp, stainless fibers, carbon fibers, and coloring agents may be blended. Further, in the above, the amount of water can be varied over a wide range, and is generally preferably 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 primary 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 implemented by This carbonation will proceed satisfactorily at room temperature and pressure as long as carbon dioxide gas is introduced into the system, but it is preferably carried out under pressure (gauge pressure up to about 10 kg/ ^cm2 ), which will speed up the carbonation. This makes it possible to complete the reaction in a short time. 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 accelerated 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. Furthermore, if the amount of water added is increased five times and the reaction system is pressurized to 2 kg/cm ² (gauge pressure), the reaction will normally be completed in around 1 hour ^;
(gauge pressure), it is recognized that the reaction can be completed in an extremely short time of about 30 minutes. 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 their primary particles and thus without any morphological change. In other words, the chain structure of SiO ₄ tetrahedrons that forms the skeleton structure of the primary calcium silicate crystal is maintained as it is, and due to this chain structure, the amorphous silica (opsil) that has a crystal appearance and the ultrafine calcium carbonate attached to it are is generated. 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. Examples Reference examples and examples are given below to explain the present invention in more detail. The X-ray diffraction diagram, electron micrograph, and pore size distribution diagram of the substances obtained in each Reference Example and Example are shown in the drawings. FIGS. 1A and 1B are X-ray diffraction patterns of starting materials, zonotrite crystals and silsite, respectively. This was 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 the X-rays, 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. Figure 4 is a 5000x electron micrograph.
B is a photograph of the starting material α-dicalcium silicate crystal, and B is a photograph of silsite obtained from the crystal. Figure 5 is a pore size distribution map of silcite,
The horizontal axis is the pore diameter (Å) and the vertical axis is the pore volume [(cc/
g・Å)×10 ³ ]. 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 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 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 Next, the slurry is dried at 150°C and pulverized to obtain a white fine powder. The electron micrograph is shown in FIG. 2A. From the figure, the primary particle has at least two symmetrical surfaces and has a length of about 1 to 1.
20μ, a thickness of about 0.02 to 0.1μ, and a width of about 0.02 to 1.0μ, and the length 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 a diameter 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 Next, the slurry is dried at 150°C and pulverized to obtain a white fine powder. The electron micrograph is shown in FIG. 3A. From the figure, the primary particle has at least two symmetrical surfaces and has a length of about 1 to 1.
20μ, a thickness of about 0.02-0.1μ, and a width of about 0.2-5.0μ, with the length being at least about 10 times the thickness. The primary particles have a specific surface area of about 61 m ² /g. Reference example 3 Quicklime as a lime raw material and commercially available white carbon as a silicic acid raw material (particle size 100 mμ or less, SiO ₂
(approximately 88% by weight). Disperse these in water at a molar ratio of lime and silicic acid of 0.57:1,
A raw material slurry is prepared with a water to solids ratio (weight) of 12:1. The raw material slurry is charged into an autoclave, heated to 200°C, and subjected to a hydrothermal reaction with stirring for 8 hours under a saturated steam pressure of 15 kg/cm ² to obtain a slurry of gyrolite crystals. As a result of X-ray diffraction analysis, the obtained crystal has a diameter of 4.0°,
It exhibits diffraction peaks (2θ) at 28.2° and 28.9° that are characteristic of gairolite crystals. Its composition after ignition is as follows. SiO ₂ 56.88% CaO 30.75 Al ₂ O ₃ 0.39 Fe ₂ O ₃ 0.29 Ig.loss 11.39 99.70 Next, the above slurry is dried at 150°C and pulverized to obtain a white fine powder. As a result of electron microscopy, the obtained primary particles have at least two symmetrical surfaces and have a length of about 1 to 20 μm, a thickness of about 0.02 to 0.1 μm, and a width of about 0.2 to 5 μm. It can be seen that the thickness is at least 10 times the thickness. The primary particles are approximately
It has a specific surface area of 60 m ² /g. Reference example 4 Quicklime as lime raw material and 350 as silicic acid raw material
Uses silica powder from Metsuyu. These are dispersed in water at a molar ratio of lime to silicic acid of 2.0:1, and a raw material slurry is prepared with a water to solid content ratio (weight) of 4:1. The raw material slurry is charged into an autoclave, heated to 191° C., and subjected to heating reaction under a saturated steam pressure of 12 kg/cm ² for 5 hours to obtain a slurry of α-dicalcium silicate hydrate crystals. As a result of X-ray diffraction analysis, the obtained crystal was 16.6°,
Diffraction peaks (2θ) characteristic of α-dicalcium silicate hydrate crystals are shown at 27.3° and 37.2°. Its composition after ignition is as follows. SiO ₂ 30.81% CaO 57.02 Al ₂ O ₃ 0.45 Fe ₂ O ₃ 0.50 Ig.loss 10.05 98.83 The slurry obtained above is dried at 150° C. and then ground to obtain white fine powder primary particles. The electron micrograph is shown in FIG. 4A. From the figure, the primary particle has at least two symmetrical surfaces and a length of approximately 1.
~300μ, a thickness of about 0.1-1μ, and a width of about 1-30μ, and the length is at least 10 times the thickness. The primary particles are about 6
It has a specific surface area of m ² /g. Example 1 The zonotrite needle-like crystal primary particles obtained in Reference Example 1 were used as a starting material. This was placed in a closed pressure vessel along with 5 times its weight of water, and carbon dioxide gas was pressurized into the vessel at room temperature, and the internal pressure was maintained at 3 kg/cm ² for approximately 30 minutes.
Carry out carbonation for a minute. In this way, amorphous silica-calcium carbonate composite 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, and the results observed in Figure 1A All the peaks characteristic of calcium silicate crystals have disappeared and are replaced by 23.0°.
Only the diffraction peaks (2θ) of calcium carbonate crystals appeared at 29.4° and 36.0°, indicating that calcium silicate was converted into amorphous silica and calcium carbonate by carbonation. Furthermore, the results of electron microscopic observation are shown in FIG. 2B. From the figure, the composite particle has at least two symmetrical surfaces, a length of about 1 to 20 μm, and a length of about 1 to 20 μm.
It has a thickness of 0.02 to 0.1μ and a width of about 0.02 to 1.0μ,
It can be seen that calcium carbonate microparticles in the form of ultrafine particles of about 2 μm or less are attached to amorphous silica whose length is 10 times or more the thickness. It can be seen that the shape of the amorphous silica is exactly the same as that of the needle-like zonotolite crystals used as the starting material (FIG. 2A), and that it maintains the acicular outer shape of the zonotolite as it is. These composite particles were dispersed in water to a concentration of 5% by weight, stirred for 20 minutes, and then left to stand. Even if the silica and calcium carbonate constituting the particles were attempted to be separated by sedimentation due to the difference in specific gravity, they could not be separated at all. Strong chemical or physical adhesion is observed. The characteristics of the silsite obtained above are shown below. Bulk density: 0.139 g/cm ³ Specific surface area: 63 m ² /g Oil absorption: 300 c.c./100 g Furthermore, the state of the pore size distribution of the above silsite is as shown in curve 1 in Figure 5, with a peak at 27 Å. It will be done. The silsite obtained above is dispersed in water so that the weight ratio of water to solids is 5:1 to obtain an aqueous slurry of the present invention. Next, the obtained aqueous slurry is placed in a mold, dehydrated, molded, and dried to obtain a molded body. The physical properties of the obtained molded article are shown below. Bulk density 0.37 g/cm ³ Porosity 84.8% Heat resistance at 950°C No change Compressive strength 12 Kg/cm ² Bending strength 8 Kg/cm ² Example 2 Starting from the tobermolite plate crystal primary particles obtained in Reference Example 2 Use as raw material. This was placed in a closed pressure vessel along with 5 times its weight of water, and carbon dioxide gas was pressurized into the vessel at room temperature, and the internal pressure was maintained at 3 kg/cm ² for approximately 30 minutes.
Carry out carbonation for a minute. In this way, amorphous silica-calcium carbonate composite 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 The X-ray diffraction results are the same as shown in Figure 1B, and the tobermolite crystal used as the starting material All the characteristic peaks have disappeared, and instead they are 23.0°, 24.8°,
Only diffraction peaks (2θ) of calcium carbonate crystals appeared at 27.0°, 29.4°, 32.8°, and 36.0°, indicating that calcium silicate was converted into amorphous silica and calcium carbonate by carbonation. Further, the results of electron microscopic observation are shown in FIG. 3B. From the figure, the composite particle has at least two symmetrical surfaces, a length of about 1 to 20 μm, and a length of about 1 to 20 μm.
Amorphous silica having a thickness of 0.02 to 0.1μ, a width of about 0.2 to 5.0μ, and a length of at least 10 times the thickness, with the form of ultrafine particles of about 2μ or less It can be seen that fine particles of calcium carbonate are attached to the surface. The shape of the amorphous silica is that of the tobermolite plate crystals used as the starting material (Figure 3A).
It can be seen that the plate-like external shape of the tobermolite is maintained as it is. This composite particle was obtained by dispersing it in water to a concentration of 5% by weight, stirring it for 20 minutes, and then allowing it to stand. Even if the silica and calcium carbonate constituting the particles were attempted to be separated by sedimentation due to the difference in specific gravity, the two could not be separated at all. It is recognized that there is strong adhesion either chemically or physically. The characteristics of the silsite obtained above are shown below. Bulk density 0.101g/cm ³ Specific surface area 55m ² /g Oil absorption 300c.c./100g Furthermore, the state of the pore size distribution of the above silsite is as shown in curve 2 in Figure 5, with a peak at 23 Å. It will be done. The slurry of the present invention is obtained by dispersing the silsite obtained above in water such that the weight ratio of water to solids is 5:1. Next, the obtained aqueous slurry is placed in a mold, dehydrated, and then dried to obtain a molded body. The physical properties of the obtained molded article are shown below. Bulk density 0.50 g/cm ³ Porosity 80.0% Heat resistance at 950°C No change Compressive strength 15 Kg/cm ² Bending strength 8 Kg/cm ² Example 3 The primary particles of gyrolite plate crystals obtained in Reference Example 3 were used as the starting material. do. This was placed in a closed pressure vessel along with 5 times its weight of water, and carbon dioxide gas was pressurized into the vessel at room temperature, and the internal pressure was maintained at 3 kg/cm ² for approximately 30 minutes.
Carry out carbonation for a minute. In this way, amorphous silica-calcium carbonate composite particles are obtained. The analysis results are as follows. Composition (%) SiO ₂ 48.22 CaO 26.07 Al ₂ O ₃ 0.33 Fe ₂ O ₃ 0.25 Ig.loss 24.33 Total 99.20 The X-ray diffraction results are the same as shown in Figure 1B, and the calcium silicate used as the starting material All the crystal-specific peaks have disappeared and are replaced by 23.0°,
Only the diffraction peaks (2θ) of calcium carbonate crystals appear at 24.8°, 27.0°, 29.4°, 32.8° and 36.0°. Carbonation converts calcium silicate into amorphous silica and calcium carbonate. Further, according to the results of electron microscopy, the composite particles have at least two symmetrical surfaces, a length of about 1 to 20 μm, a thickness of about 0.02 to 0.1 μm, and a thickness of about 0.2 μm.
Calcium carbonate microparticles in the form of ultrafine particles of approximately 2μ or less are attached to amorphous silica with a width of ~5μ and a length approximately 10 times or more than the thickness. . The shape of the amorphous silica is exactly the same as that of the gyrolite plate crystals used as the starting material, and maintains the plate-like outer shape of the gyrolite as it is. This composite element was obtained by dispersing it in water to a concentration of 5% by weight, stirring it for 20 minutes, and then allowing it to stand. Even if an attempt was made to separate the silica and calcium carbonate that make up the particles by sedimentation due to the difference in specific gravity, the two could not be separated at all. It is recognized that there is strong chemical or physical adhesion. The characteristics of the silsite obtained above are shown below. Bulk density 0.135 g/cm ³ Specific surface area 50 m ² /g Oil absorption 260 c.c./100 g Furthermore, the state of the pore size distribution of the above silsite is as shown by curve 3 in Figure 5, with a peak at 28 Å. It will be done. 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 solids is 5:1. This material has the ability to form a molded product that is lightweight and has mechanical strength simply by dehydration molding and drying. Example 4 The plate-like crystal primary particles of α-dicalcium silicate hydrate obtained in Reference Example 4 were used as a starting material. This was placed in a closed pressure vessel together with 5 times its weight of water, and carbon dioxide gas was pressurized into the vessel at room temperature.
Carbonation is carried out for about 30 minutes while maintaining the internal pressure at 3 kg/cm ² . In this way, amorphous silica-calcium carbonate composite particles (silsite) are obtained. The analysis results are as follows. Composition (%) SiO ₂ 22.86 CaO 42.24 Al ₂ O ₃ 0.31 Fe ₂ O ₃ 0.33 Ig.loss 34.50 Total 100.24 The X-ray diffraction results are the same as shown in Figure 1B, and are unique to the calcium silicate crystal used as the starting material. The peaks of 23.0°, 24.8°, and 23.0° have all disappeared.
Only the diffraction peaks (2θ) of calcium carbonate crystals appear at 27.0°, 29.4°, 32.8°, and 36.0°. Carbonation converts calcium silicate into amorphous silica and calcium carbonate. Further, according to the results of electron microscopy, the composite particles have at least two symmetrical surfaces and a length of about 1 to 300 μm, as shown in FIG. 4B, and a length of about 0.1 to 1 μm.
It has a thickness of about 1 to 30μ, and the length is about the same as the thickness.
Amorphous silica with a size that is 10 times more
Calcium carbonate fine particles in the form of ultrafine particles of 2μ or less are attached to it. The shape of the amorphous silica is exactly the same as that of the α-dicalcium silicate hydrate plate crystals used as the starting material (FIG. 4A), and maintains the crystal habit as it is. These composite particles were obtained by dispersing the particles in water to a concentration of 5% by weight, stirring for 20 minutes, and then allowing the particles to stand. Even if the silica and calcium carbonate that constitute the particles were attempted to be separated by sedimentation due to the difference in specific gravity, the two could not be separated at all. It is recognized that there is strong adhesion either chemically or physically. The characteristics of the silsite obtained above are shown below. Bulk density: 0.656 g/cm ³ Specific surface area: 8 m ² /g Oil absorption: 100 c.c./100 g Further, the state of the pore size distribution of the above-mentioned silcite is as shown by curve 4 in FIG. The peak is observed at 24 Å. The aqueous slurry of the present invention is obtained by dispersing the silsite obtained above in water such that the weight ratio of water to solids is 5:1. This material has the ability to be molded into a lightweight and mechanically strong molded product 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. FIG. 4 is an electron micrograph, in which A shows the starting material α-C ₂ SH crystal and B shows the silsite obtained from the crystal. FIG. 5 is a pore size distribution map of silsite.

Claims (1)

[Claims] 1 Crystal-like amorphous silica in appearance, having at least two planes in a symmetrical relationship, having a length of about 1 to 300 μ and a thickness of about 0.02 to 1 μ, the length being at least 10 times the thickness. and a forming raw material obtained by dispersing in water primary particles of a silica-calcium carbonate composite composed of ultrafine calcium carbonate adhered to the silica.