JPH0559843B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing synthetic hectorite, and more particularly, to a method for producing synthetic hectorite which has excellent transparency when made into an aqueous dispersion. . (Prior Art and Technical Problems of the Invention) Synthetic hectorite has high water swelling properties and is used as a thickener and gelling agent. Conventionally, many proposals have been made regarding the manufacturing method. For example, U.S. Pat. Nos. 3,586,478 and 3,671,190 disclose that certain water-soluble magnesium salts, sodium silicate, sodium carbonate or sodium hydroxide and compounds capable of releasing both fluoride and lithium ions are A method is disclosed for producing synthetic hectorite by mixing in proportions and hydrothermally treating the aqueous slurry formed. Furthermore, in JP-A No. 52-130499, magnesium oxide, water, hydrofluoric acid and lithium hydroxide are mixed, silica sol is added thereto, the mixture is heated and mixed to form a gel, and this gel is mixed with water. A method for synthesizing hectorite by heat treatment is described. Furthermore, JP-A No. 59-21517 discloses that sodium silicate and magnesium salt are mixed to form an evenly mixed solution of both, then both components are precipitated with alkali, and by-product solutes are removed by washing with water. It is described that hectorite-type minerals are synthesized by subsequently adding monovalent or divalent cations and fluorine ions and subjecting them to a hydrothermal reaction. However, these synthetic methods generally require a large amount of alkaline agents or require reaction operations to be carried out in multiple stages, and are still unsatisfactory in terms of manufacturing costs. Synthetic hectorite itself requires an extremely long time to achieve sufficient thickening effect.
The properties as a thickener and a gelling agent were still not fully satisfactory. The present inventors previously discovered that when activated aluminosilicate obtained by acid-treating natural clay minerals such as acid clay under certain conditions is used as a silica raw material for hectorite synthesis, the reaction conditions are extremely mild. Moreover, synthetic hectorite can be obtained through simple operations, and the resulting synthetic hectorite has unique X-ray diffraction characteristics due to its chemical composition in which part of the silica content is replaced by alumina content. It has been discovered that it exhibits not only excellent water swelling properties but also excellent viscosity increasing speed. However, the synthetic hectorite obtained by this method has a somewhat cloudy appearance when made into an aqueous dispersion, and is not yet fully satisfactory for applications requiring transparency. (Gist and Object of the Invention) The present inventors have discovered that by treating the clay mineral with an alkali prior to the above-mentioned acid treatment of the clay mineral, cristobalite in the clay mineral can be selectively converted into an alkali silicate; It has been found that by acid-treating this alkali-treated clay and synthesizing hectorite using this clay as a raw material, synthetic hectorite with excellent transparency can be obtained in the form of an aqueous dispersion. That is, an object of the present invention is to provide a method for producing synthetic hectorite with excellent transparency in the form of an aqueous dispersion using naturally occurring clay minerals as a silica raw material. Another object of the present invention is to provide a method for producing synthetic hectorite that has excellent transparency, water swelling properties, and thickening speed. Still another object of the present invention is to provide a method for producing synthetic hectorite in which the hydrothermal synthesis reaction to hectorite can be performed in a substantially stoichiometric amount, under relatively mild reaction conditions, and with a small number of steps. There is something to do. Still another object of the present invention is to provide a method for easily producing synthetic hectorite with uniform particle size and excellent permeability and water washability. (Structure of the Invention) According to the present invention, a smectite clay mineral containing cristobalite as an impurity is treated with an alkali under conditions in which the crystal structure of cristobalite substantially disappears, and the generated alkali silicate is separated or treated with an alkali. In a state containing acid and alkali,
When the alkali-treated clay was treated, the X-ray diffraction peak of surface index [001] substantially disappeared and the product Al ₂ O ₃ :
Active aluminosilicic acid is produced by acid treatment under conditions such that the molar ratio of SiO ₂ is in the range of 1:11 to 1:330, and (a) the activated aluminosilicic acid, (b) a magnesium component, and (c) an alkali. A process for producing synthetic hectorite is provided, which comprises hydrothermally treating at least one compound or combination of compounds capable of releasing metal ions and fluorine ions in a hectorite product composition. (Characteristics and Effects of the Invention) The present inventors have investigated the cause of hectorite synthesized from naturally occurring clay minerals as a silica raw material, which exhibits a cloudy appearance in the state of an aqueous dispersion and lacks transparency. It was found that the cause of turbidity was cristobalite, which is inevitably contained as an impurity in the smectite structure. In addition to smectite, naturally occurring clay minerals include
It contains impurities such as quartz, feldspar, and cristobalite. Among these impurities, impurities such as quartz and feldspar have different specific gravity from smectite, so they can be easily separated by means such as elutriation, but cristobalite is different from smectite. It has a specific gravity close to that of smectite, and some of it exists in the form of a mixed crystal with smectite, so it is difficult to separate it by normal physical means. In addition, cristobalite is stable against mineral acids and has poor reactivity with other components for hectorite production, so its remaining in synthetic hectorite causes turbidity. . The present invention utilizes the property that cristobalite reacts relatively easily with alkali to become an alkali silicate, while smectite is relatively stable under alkali treatment conditions. By treating cristobalite with alkali and converting cristobalite into alkali silicate, we succeeded in removing cristobalite, which is the substance that causes turbidity in synthetic hectorite. The synthetic hectorite according to the present invention has excellent transparency and is synthesized from acid-treated clay minerals as a raw material for silica. It has water swelling properties and thickening speed. (Preferred Embodiment of the Invention) In the present invention, clay minerals include smectite group clay minerals, such as so-called montmorillonite group clay minerals such as acid clay, bentonite, subbentonite, and Frass earth, beidellite,
One type or a combination of two or more types of saponite, nontronite, etc. are preferably used. These clay minerals are rarely produced in pure form and are produced together with impurities such as quartz, feldspar, and cristobalite. Impurities such as feldspar and quartz can be separated and removed by physical means such as hydroxyl and classification. The amount of cristobalite contained in clay minerals varies considerably depending on the type of clay, the ore deposit, etc., but generally speaking, it is in the range of 2 to 40% by weight, and according to the present invention, By treating the mineral with an alkali, the cristobalite contained therein is converted into an alkali silicate. The amount of alkali to be used is such that the crystal structure of cristobalite can be virtually completely disappeared, and specifically, the amount of alkali is 0.2 to 2 times, particularly 0.5 to 1 times by mole, based on cristobalite SiO ₂ . (based on alkali metal oxides) may be used. As the alkali, an alkali hydroxide such as sodium hydroxide or potassium hydroxide, an alkali carbonate salt such as sodium carbonate, or a mixture thereof is used. The alkaline treatment can be carried out wet or dry in the presence of water; in the former case, the alkaline solution and the clay mineral are brought into contact with each other under stirring. In the latter case, an alkali treatment is performed by adding an alkali or an alkaline solution to the clay mineral and kneading this composition by utilizing the water contained in the clay mineral. Although the treatment can proceed at room temperature, it is generally desirable to heat the reaction to a temperature of 60 to 160° C. in order to accelerate the reaction. Alkali silicate is produced by the reaction of cristobalite with alkali, and this alkali silicate may be separated from purified smectite or may be directly subjected to acid treatment without separation. This is because the generated sodium silicate becomes easily reactive amorphous silica by neutralization with acid, and this is effectively used in the synthesis of hectorite. Next, the alkali-treated clay has a surface index [001]
The X-ray diffraction peak of the product virtually disappears, and the molar ratio of Al ₂ O ₃ :SiO ₂ in the product ranges from 1:11 to 1:330.
The activated aluminosilicate obtained by acid treatment is used as a silica raw material. This activated aluminosilicate and the like have several characteristics that are not found in other silicic acid raw materials when synthesizing hectorite. First, this activated aluminosilicate has a significantly large specific surface area and is generally
It is an amorphous aluminosilicate gel with a BET specific surface area in the range of 50 to 300 m ² /g, and has the advantage of outstandingly excellent reactivity. Moreover,
Activated aluminosilicate is completely different from ordinary gel-like silica, and has a microstructure suitable for the synthesis of microstructured layered silicates. Clay minerals are generally
The base is a two- or three-layer structure in which a tetrahedral layer of SiO ₄ and an octahedral layer of AlO ₆ etc. are combined in a layered manner, and these basic structures are further stacked to form a multilayer structure. When these clay minerals are treated with acid, the octahedral layer of _AlO6 is extracted as a soluble salt by reaction with acid, and its crystal structure is virtually destroyed, but
The SiO ₂ tetrahedral layer still remains in the form of a fine layered structure, which forms the main body of the activated aluminosilicate. Furthermore, the tetrahedral layer of SiO ₄ exists in a form in which AlO ₄ is partially substituted, or in the form in which an alumina octahedral layer is bonded to the tetrahedral layer. Therefore, the fine layered structure produced by acid treatment has Alumina is contained in the amount ratio mentioned above. On the other hand, Hectorite, as already mentioned,
It mainly has a three-layer structure in which an octahedral layer of MgO ₆ is sandwiched between two tetrahedral layers of SiO ₄ , but these are composed of a SiO ₄ tetrahedral layer and a MgO ₆ or AlO _{6 octahedral} layer.
It has the same structure as the raw clay in that the octahedral layers of SiO ₄ are bonded together in a layered manner, and it also has a SiO 4 tetrahedral layer. In the present invention, by using activated aluminosilicate as a raw material, it is believed that recombination to hectorite can be easily performed while maintaining the fine layered structure, and a predetermined amount of alumina can be introduced. The X-ray diffraction peak of the plane index [001] of clay minerals indicates the degree of stacking of layered crystals in the C-axis direction, and the disappearance of this diffraction peak indicates that the level below the basic unit layer This means that crystal destruction has occurred. It is also important that the molar ratio of Al ₂ O ₃ :SiO ₂ is within the range of 1:11 to 1:330 in order to provide the synthetic hectorite with the chemical composition and laminated irregular structure described below. Except for the above-mentioned limitations, acid treatment conditions can be based on conditions known per se. For example, as the acid, mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as benzenesulfonic acid, toluenesulfonic acid, and acetic acid are used, and mineral acids such as sulfuric acid are generally used. The method of contacting the clay mineral and acid may be arbitrary, such as a slurry activation method in which clay and acid are brought into contact in a slurry state, a granular activation method in which granulated clay and acid are brought into solid-liquid contact, A mixture of clay and acid is reacted dry (inside the granules),
Next, a dry activation method or the like may be employed in which by-product salts are extracted. The amount of acid used varies depending on the acid treatment conditions, but the molar ratio of Al ₂ O ₃ :SiO ₂ in the product is within the range mentioned above, and Fe 2 O 3 and Fe ₂ O ₃ in the clay mineral are
Any material may be used as long as MgO or other basic components such as alkali metal components are substantially removed. for example,
In the dry activation method, acid treatment is performed using 0.3 to 1.5 equivalents, particularly 0.6 to 1.2 equivalents of acid or acid aqueous solution relative to the basic component in the clay mineral. The reaction conditions are
A temperature of 60 to 300°C and a time of 10 to 600 minutes are determined so that the above requirements are met. The extraction of the soluble base components from the reaction product is carried out in an aqueous medium with a pH below 1 so that their hydrolysis is prevented. It is desirable that the particle size of acid-treated clay be as fine as possible, and particles with a particle size of 5μ or less account for 20% of the total.
More than 30% by weight, especially 30% by weight or more, and particles larger than 20μ are smaller than 30% by weight of the whole, especially 10
It is preferable to adjust the particle size so that it is smaller than % by weight before using it in the reaction. According to the present invention, (a) the thus obtained activated aluminosilicate, (b) a magnesium component, and (c) at least one compound capable of releasing alkali metal ions and fluorine ions. The combination is subjected to hydrothermal treatment at a hectorite-forming composition ratio. As the magnesia raw material, a magnesium oxide, hydroxide, or a compound capable of forming the above-mentioned oxide or hydroxide under reaction conditions can be used. Examples of such compounds include magnesium carbonates and alkoxides. Various magnesium salts can be decomposed into magnesium hydroxide on the spot and subjected to the reaction, but in order to produce high-quality magnesium phyllosilicate salts, it is necessary to mix various water-soluble salts into the reaction system. should be avoided at all costs. Magnesium oxides and hydroxides are preferred raw materials. At least one compound or a combination of compounds capable of releasing alkali metal ions and fluorine ions may be used alone, such as lithium fluoride, sodium fluoride, lithium hexafluorosilicate, or sodium hexafluorosilicate. In addition to the compounds capable of releasing ions, combinations of fluorine-containing acids such as hydrofluoric acid and fluorosilicic acid with lithium hydroxide, sodium hydroxide, lithium carbonate, sodium carbonate, and the like may be mentioned. Of course, any combination of a plurality of types can be used. The usage ratio of the above components (a), (b) and (c) is determined so as to give the chemical composition of hectorite. According to the present invention, a remarkable feature is that synthetic hectorite can be easily obtained using stoichiometric amounts of each raw material. The pH of the reaction mixture is generally between 8 and 11, particularly between 8.5 and 10.
It is desirable that it be within the range of . The pH is adjusted by adding an alkali metal hydroxide or carbonate to the reaction system, if necessary. The hydrothermal reaction is generally carried out in the form of an aqueous slurry, with the solids concentration ranging from 1 to 30% by weight, especially from 5 to 15% by weight.
It is advantageous in terms of operability to set the weight percentage within the range. The hydrothermal treatment is performed by charging the above raw materials into an autoclave and heating them. As for reaction conditions, generally a treatment time of 0.5 to 10 hours at a temperature of 110 to 200°C is sufficient. At this time, the stress in the reaction system is
Maintained at 0.5 to 15.5Kg/cm ² gauge. According to the present invention, the desired hectorite can be easily obtained in one step of reaction (hydrothermal treatment), and one advantage is that the synthesis conditions are relatively mild compared to conventional methods. . Moreover, the obtained hectorite is substantially unswollen not only in the slurry or overcake state but also in the water-washed state, and by drying it, the swelling property and viscosity increase rate can be improved A completely unexpected fact has been discovered that it makes an excellent synthetic hectorite. Moreover, this newly generated hectorite is
It has the advantage that it has excellent permeability and that purification operations such as washing with water can be carried out very easily. The synthetic hectorite according to the present invention ideally has
The following formula (M′ _x+z ) M _x Mg _3-x Si _4-z Al _z O ₁₀ (OH) _2-y F _y
...(1) In the formula, each of M and M' is an alkali metal such as lithium and/or sodium, and x is 0.1
y is a number from 0 to 2, especially 0.8 to 1.8, and z is a number from 0.02 to 1.8.
0.6, in particular a number between 0.04 and 0.2. As is clear from the above formula, the synthetic hectorite according to the present invention has a remarkable chemical composition in that a part of the silica component is replaced with an alumina component. In other words, in this synthetic hectorite, in order to compensate for the lack of valence due to a part of the skeleton of the SiO ₄ tetrahedral layer being replaced with AlO ₄ , there is an excess of valence between the basic layer units compared to conventional hectorite. of alkali metal components (M′ _z ) are present. It is understood that due to the presence of this excess alkali metal component between the layers, the synthetic hectorite of the invention exhibits significantly better water swellability and a significantly increased rate of thickening. In the synthetic hectorite according to the present invention,
Alkali metal content M substituted in MgO ₆ octahedral layer
is preferably a lithium component, while the alkali metal component M' present between the basic layer units is preferably a sodium component from the viewpoint of water coordination. It is important that the alumina component exists in a form that replaces the silica tetrahedral layer, but a part of it may also exist in a form that replaces the magnesia octahedral layer. The synthetic hectorite according to the present invention has an X-ray diffraction pattern characteristic of the layered structure described above. FIG. 1 of the accompanying drawings shows that the synthetic hectorite according to the present invention is Cu
- An X-ray diffraction spectrum using Kα rays is shown. From FIG. 1, the synthesized hectorite according to the present invention has plane spacings of 4.5 to 4.6 Å (corresponding to the [020] plane and [110] plane), 2.5 to 2.6 Å (corresponding to the [200] plane), and 1.5 to 4.6 Å (corresponding to the [200] plane).
It is clear that each has a diffraction peak at 1.6 Å (corresponding to the [060] plane), which is an X-ray diffraction peak common to natural trioctahedral layered clay minerals. In the synthetic hectorite according to the present invention, each of the layers described above overlaps in parallel, but a certain specific irregularity is observed in the relative position of each layer. FIG. 2 of the accompanying drawings is an enlarged diagram of the diffraction peak around d=4.5 Å in the X-ray diffraction spectrum of FIG. 1. From FIG. 2, this peak has a relatively steep rise on the narrow angle side (the side where 2θ is small), and shows an asymmetric peak with a gentle slope on the wide angle side (the side where 2θ is large). In a structure in which the layers are regularly stacked, this peak is symmetrical, and the asymmetric peak described above indicates that there is some irregularity in the relative position of each layer. In this specification, the stacking irregularity index (I _s ) of synthetic hectorite is defined as follows. That is,
An X-ray diffraction chart as shown in FIG. 2 is obtained by the method described in the Examples below. This d=4.5~4.6
For the peak of Å, draw a maximum slope peak tangent a on the narrow-angle side and a maximum slope peak tangent b on the wide-angle side of the peak, and draw a perpendicular line e from the intersection of tangents a and tangents b. Next, the angle θ ₁ between the tangent line a and the perpendicular line c, and the angle θ 1 between the tangent line a and the perpendicular line c
Find the angle θ ₂ with The stacking irregularity index (I _s ) is obtained as the value of I _s = tanθ ₂ /tanθ ₁ (2). This index (I _s ) is 1.0 when the peak is completely symmetrical, and increases as the degree of asymmetry increases. The synthetic layered magnesium phyllosilicate according to the present invention has a novel laminated disordered structure with a lamination irregularity index (I _s ) of 2.4 or more. It is thought that such a laminated irregular structure also exhibits a remarkable effect in increasing the water swelling property and increasing the rate of viscosity increase. Although this synthetic hectorite is synthesized using naturally occurring clay minerals as a silica source, it is characterized by outstanding transparency when made into an aqueous dispersion. The transparency of the clay aqueous dispersion is determined by the turbidity measured by a Poitzk integrating sphere turbidity meter for a dispersion with a solid content concentration of 1% (corresponding turbidity of a standard kaolin turbidity solution).
It can be evaluated by Synthetic hectorite made from non-alkali treated clay generally exhibits a turbidity of 100 to 1000 ppm, whereas in the synthetic hectorite of the present invention, this turbidity is suppressed to 30 ppm or less. The synthetic hectorite according to the invention generally comprises:
Obtained as particles with a residue of 10% or less after passing through 100 meshes and 5% or less after passing through 55 meshes using the JIS K0069 chemical sieve residue test method (dry method). In addition, this powder generally has a bulk density of 0.4 to 0.8 g/ml, has a low content of impurities in relation to being obtained by a synthetic method, and has a Hunter whiteness of generally 80% or more, especially 90%. That's all. The invention is illustrated by the following example. Test method The test method for each item in this specification was as follows. 1 X-ray diffraction In this example, an X-ray diffraction device manufactured by Rigaku Denki Co., Ltd. (X-ray generator 4036A1, goniometer
2125D1, counting device 5071) was used. The diffraction conditions are as follows. Target Cu Filter Ni Detector SC Voltage 35kVP Current 15mA Count full scale 8000c/s Time constant 1sec Scanning speed 2°/min Chart speed 2cm/min Radiation angle 1° Slit width 0.3mm Glancing angle 6° 2 Stacking irregularity index (I _s ) Measurement method a X-ray diffraction conditions Target Cu Filter Ni Detector SC Voltage 40kVP Current 20mA Count/full scale 4000c/s Time constant 2sec Scanning speed 0.5°/min Chart speed 0.5cm/min Radiation angle 1 ° Slit width 0.15mm Viewing angle 6° Measured diffraction angle range 17° to 22° (2θ) In this example, the conditions are not limited to the above, and the peak height from the baseline is set to 2 to 5 cm. Conditions such as voltage and current may be set so as to fall within the range. b Stacking irregularity index (I _s ) calculation method The absolute value of the slope is maximized on the narrow-angle side and wide-angle side of the peak at the diffraction angle (2θ) of 19.5° to 19.7° obtained by the above X-ray diffraction. Draw the peak tangent lines (a, b) to . Next, a perpendicular line c is lowered from the intersection of the narrow-angle side peak tangent line a and the wide-angle side peak tangent line b, and the angle θ ₁ between the tangent line a and the perpendicular line c and the angle θ ₂ between the tangent line b and the perpendicular line c are determined. Find the stacking irregularity index (I _s ) using the following formula. I _s = tan θ ₂ / tan θ ₁ 3 Transparency measurement method Place 1 g of sample in a 200 ml glass standard bottle containing 99 g of deionized water, shake vigorously several times, and add paint shaker (manufactured by Red Deville).
After shaking for 15 minutes, leave at room temperature.
After that, shake occasionally and leave at room temperature for 24 hours.
Transparency (standard kaolin turbidity liquid concentration) under the following conditions:
PPM). Turbidity meter: Poituta integrating sphere turbidity meter SEP-PL model manufactured by Nippon Seimitsu Kogaku Co., Ltd. Measurement conditions: Cell liquid layer - 30 mm Standard solution - Distilled water Reflector plate - White plate Sample turbidity concentration - 0 to 100 ppm (100 ppm or more Transparency display unit: Displayed as standard kaolin turbidity liquid concentration (ppm) 4 Viscosity measurement method: Pour 4g of sample into a 250ml glass standard bottle containing 196g of deionized water and test several times. After shaking vigorously, the mixture was further shaken for 15 minutes using a paint shaker (manufactured by Red Devil Co., Ltd.), and then allowed to stand at room temperature. After that, shake the mixture occasionally and measure the viscosity after a predetermined number of days under the following conditions. Viscometer: Tokyo Keiki B-type viscometer (BH type) Rotor used: No. 2 Number of rotations: 20 rotations Measurement temperature: 20°C Example 1 Acidic clay from Odo, Shibata City, Niigata Prefecture (moisture approx. 35
%, containing about 20% cristobalite) 4 kg of water 4
was added and crushed for 5 minutes using a Waring blender. Water was added to the crushed slurry, stirred well (10%), and placed in a transparent container to allow rocks and foreign matter to settle out.The homogeneous slurry at the top was transferred to another container using a siphon to remove foreign matter. This operation 5
A homogeneous slurry 5 was obtained by repeating the process. This slurry was transferred to a stainless steel container, 1.07 kg of 49% sodium hydroxide solution was added, and the mixture was heated at 95° C. for 5 hours to obtain a slurry containing sodium silicate and acid clay. Transfer this slurry to a glass beaker and add 98%
2.7 kg of concentrated sulfuric acid was added, and acid treatment was carried out for 10 hours while stirring at a temperature of 95°C. Acid-soluble components were separated by filtration and further washed with water to obtain a cake. Take the resulting cake in a glass beaker and add water.
was redispersed as a slurry. To this slurry, 2 kg of 98% concentrated sulfuric acid was added again, and acid treatment was carried out for 10 hours while stirring at a temperature of 95°C. Acid-soluble components were separated by filtration and washed with water until no sulfate ions were observed to obtain a cake. A part of the obtained cake was dried and analyzed by X-ray diffraction.
It was amorphous silica, and no impurities such as cristobalite or quartz were observed. Deionized water was added to this cake and pulverized in a Waring blender for 10 minutes to obtain an active aluminosilicate slurry containing 6.51% _SiO2 . (First step) Next, the obtained activated aluminosilicate slurry
230g (SiO ₂ min: 15g), magnesium hydroxide (first class reagent) 15.2g, sodium hydroxide (first class reagent) 0.96g, lithium hydroxide (first class reagent) 0.83
g, 4.1 g of hydrofluoric acid (first grade reagent), and 400 g of water were placed in a Waring blender and mixed for 10 minutes to obtain a uniform slurry. This slurry was placed in an autoclave container No. 1, and a hydrothermal synthesis reaction was carried out at 190° C. for 5 hours under stirring conditions of 500 revolutions/minute. After cooling, the reaction product was taken out, water was separated by filtration, and then dried at 130°C. The dried product was ground in a ball mill to obtain a white powder. (Second Step) When this product was analyzed by X-ray diffraction, it was found to be a synthetic hectorite having the desired hectorite crystal structure. Moreover, the 1% slurry of this product was a transparent slurry. Table 1 shows the lamination irregularity index of this product, the transparency (turbidity) of 1% slurry, and the viscosity of 2% slurry. Example 2 230 g of activated aluminosilicate slurry obtained in the first step of Example 1 (SiO ₂ minutes: 15 g), 15.2 g of magnesium hydroxide (first grade reagent), 1.65 g of lithium hydroxide (first grade reagent), hydrogen fluoride Acid (first class reagent)
Put 4.1g and 400g of water in a Waring blender,
Mixed for 10 minutes to obtain a homogeneous slurry. This slurry was placed in an autoclave container No. 1, and a hydrothermal synthesis reaction was carried out at 175° C. for 5 hours under stirring conditions of 500 revolutions/minute. After cooling, the reaction product was taken out, water was separated by filtration, and then dried at 130°C. The dried product was ground in a ball mill to obtain a white powder (second
process). When this product was analyzed by X-ray diffraction, it was found to be a synthetic hectorite having the desired hectorite crystal structure. Moreover, the 1% slurry of this product was a transparent slurry. Table 1 shows the lamination irregularity index of this product, the transparency (turbidity) of 1% slurry, and the viscosity of 2% slurry. Example 3 Pentonite from Mikawa Village, Niigata Prefecture (approx. 50% moisture,
(Contains quartz and cristobalite as foreign substances) 2Kg
4 parts of water was added to the mixture, and the mixture was ground for 5 minutes using a Waring blender. Water was added to the crushed slurry, stirred well to make it 20 ml, placed in a transparent container, and the homogeneous slurry at the top was transferred to another container using a siphon to remove foreign substances. This operation was repeated 5 times to obtain a homogeneous slurry 10. This slurry was transferred to a stainless steel container, 100 g of 49% sodium hydroxide solution was added, and the mixture was heated at 95° C. for 5 hours to obtain an alkali-treated bentonite slurry. The alkali-soluble components of this slurry were separated by filtration to obtain a cake. This case was added to water and redispersed as a slurry of No. 5. Next, 2 kg of 98% concentrated sulfuric acid was added to this slurry, and acid treatment was performed for 10 hours while stirring at a temperature of 95°C. Acid-soluble components are separated by filtration.
The cake was further washed with water to obtain a cake. The resulting cake was placed in a glass beaker and water was added to redisperse it as a slurry in step 5. To this slurry, 1 kg of 98% concentrated sulfuric acid was added again, and acid treatment was carried out for 10 hours while stirring at a temperature of 95°C. Acid-soluble components were separated by filtration and washed with water until no sulfate ions were observed to obtain a cake. A part of the resulting cake was dried and analyzed by X-ray diffraction, and it was found to be amorphous, with no impurities such as cristobalite or quartz observed. Add deionized water to this cake, crush it in a Waring blender for 10 minutes, and SiO ₂ minutes 4.36
% activated aluminosilicate slurry was obtained. (First step) Next, 344 g of the obtained slurry (SiO ₂ minutes: 15
g), Magnesium hydroxide (first class reagent) 15.2g,
0.96 g of sodium hydroxide (first grade reagent), 0.83 g of lithium hydroxide (first grade reagent), 4.1 g of hydrofluoric acid (first grade reagent), and 300 g of water were placed in a Waring blender and mixed for 10 minutes to obtain a uniform slurry. Take this slurry in autoclave container 1,
Hydrothermal synthesis reaction was carried out at 190° C. for 5 hours under stirring conditions of 500 revolutions/minute. After cooling, take out the reactant,
After separating water by filtration, it was dried at 130°C.
The dried product was ground in a ball mill to obtain a white powder (second step). This product was analyzed by X-ray diffraction and was found to be a synthetic hectorite having the desired hectorite crystal structure. Moreover, the 1% slurry of this product was a transparent slurry. Table 1 shows the lamination irregularity index of this product, the transparency (turbidity) of 1% slurry, and the viscosity of 2% slurry. Comparative Example 1 3 kg of 25% sulfuric acid was added to 740 g of coarsely crushed acid clay from Odo, Shibata City, Niigata Prefecture (moisture 32.4%).
After heating at 95℃ for 10 hours and passing through once to remove the treated solution, 3 kg of 25% sulfuric acid was added again.
Acid treatment was performed by heating at 95°C for 10 hours. The mixture was filtered and washed with water to obtain a cake. a small amount of the cake
After drying at 110°C, pulverization, and quantitative analysis, the _SiO2 content was 91.5% (based on dry matter at 110°C). The resulting cake was placed in a pot mill, water was added, and it was wet-milled with Korean balls to obtain a slurry containing ₁₅ % SiO2. (1st step) Next, 200 g of the obtained slurry (SiO ₂ minutes: 30
g) and magnesium hydroxide (first class reagent) 20.3g,
1.65 g of lithium hydroxide (first grade reagent), 8.2 g of hydrofluoric acid (first grade reagent), and 400 g of water were placed in a Waring blender and mixed for 10 minutes to obtain a uniform slurry. This slurry was placed in an autoclave container No. 1, and a hydrothermal synthesis reaction was carried out at 190° C. for 5 hours under stirring conditions of 500 revolutions/minute. After cooling, the reaction product was taken out, water was separated by filtration, and then dried at 130°C. The dried product was ground in a ball mill to obtain a white powder. (Second Step) When this product was analyzed by X-ray diffraction, it was found to be a synthetic hectorite having the desired hectorite crystal structure, but the 1% slurry of this product was a milky white translucent slurry. Table 1 shows the lamination irregularity index of this product, the transparency (turbidity) of 1% slurry, and the viscosity of 2% slurry. Comparative Example 2 Put 300ml of water in the beaker of 1, and add No. 3 sodium silicate (SiO ₂ min: 25%, Na ₂ O content: 7%)
139 g was dissolved and 35 g of hydrochloric acid (first grade reagent: 35%) was added to obtain an acidic silica solution. Add 68g of magnesium chloride (first grade reagent: MgCl ₂ 6H ₂ O) to this and 200g of water.
ml of the solution was added to prepare a mixed solution. This mixed solution was poured into 250 ml of aqueous ammonia (first class reagent: 28%) with stirring to obtain a white slurry. This slurry was filtered and washed with water to obtain a filter cake. Transfer this cake to autoclave container 1, add 100g of water, lithium hydroxide (reagent grade 1:
LiOH・H ₂ O) 2.5g, sodium hydroxide (first grade reagent) 2.5g, hydrofluoric acid (first grade reagent: 46%) 5.4
A hydrothermal synthesis reaction was carried out at 200° C. for 5 hours under stirring conditions of 500 rpm. After cooling, water was separated by filtration and then dried at 130°C. The dried product was ground in a ball mill to obtain a white powder. When this product was analyzed by X-ray diffraction, synthetic hectorite having a hectorite-type crystal structure was obtained. Table 1 shows the lamination irregularity index of this product, the transparency (turbidity) of 1% slurry, and the viscosity of 2% slurry. 【table】

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction spectrum using Cu-Kα rays of the synthesized hectorite according to Example 1 of the present invention. Figure 2 is an enlarged diagram of the diffraction peak near d = 4.5 Å in the X-ray diffraction spectrum of Figure 1, and shows θ ₁ and θ ₂ for calculating the stacking irregularity index (I _s ).
This is a diagram showing how to find it.

Claims (1)

[Scope of Claims] 1 A smectite-type clay mineral containing cristobalite as an impurity is treated with an alkali under conditions in which the crystal structure of cristobalite substantially disappears, and the alkali silicate produced is separated or the alkali silicate is separated. In this state, the alkali-treated clay was treated so that the X-ray diffraction peak of surface index [001] substantially disappeared and the molar ratio of Al ₂ O ₃ :SiO ₂ in the product was in the range of 1:11 to 1:330. producing activated aluminosilicic acid by acid treatment under conditions such that (a) the activated aluminosilicic acid, (b) a magnesia component, and (c) at least one compound capable of releasing alkali metal ions and fluorine ions. A method for producing synthetic hectorite, which comprises hydrothermally treating a combination of compounds at a hectorite-producing composition ratio.