JP7654484B2 - Swellable synthetic layered silicate lump and swellable synthetic layered silicate powder - Google Patents

Description

The present disclosure relates to a lump of swellable synthetic layered silicate. The present disclosure relates to a powder containing a powder of swellable synthetic layered silicate. The present disclosure also relates to a method for producing layered silicate.

The melt synthesis method is known as a method for producing layered silicates (see, for example, Patent Document 1). In the melt synthesis method, raw materials mixed according to the chemical composition of the layered silicate are heated and melted, and the resulting melt is cooled to produce a crystallized layered silicate. In the production method described in Patent Document 1, the raw materials are melted within 20 minutes, and the melt is cooled at a cooling rate of 0.01°C/min to 50°C/min.

Patent Document 2 describes a method for producing synthetic hectorite, in which a smectite-type clay mineral containing cristobalite is treated with alkali under conditions in which the crystal structure of the cristobalite is substantially eliminated.

Patent No. 4216510 Japanese Unexamined Patent Publication No. 62-59518

In a typical melt synthesis method, cristobalite is generated as an impurity. In the method described in Patent Document 1, the raw material is rapidly melted to reduce the amount of cristobalite impurities in the lumps of swellable synthetic layered silicate. However, even with the method described in Patent Document 1, the lumps of swellable synthetic layered silicate still contain 3 volume % (approximately 2.6 mass %) of cristobalite, and it is expected that the amount of cristobalite can be further reduced.

Swellable synthetic layered silicates are usually powdered by crushing the ore lumps. Therefore, the removal of cristobalite by classification after crushing is also considered. However, it is difficult to reduce the amount of cristobalite by classification, and there is also a large loss of swellable synthetic layered silicate.

In the method described in Patent Document 2, cristobalite in a clay mineral is treated by alkali treatment. However, it is difficult to reduce the amount of cristobalite in a swellable synthetic layered silicate even by the alkali treatment described in Patent Document 2. In addition, increasing the number of steps such as the alkali treatment leads to an increase in the production cost of the swellable synthetic layered silicate.

Therefore, there is a demand for lumps and powders of swellable synthetic layered silicate with reduced amounts of cristobalite impurities. There is also a demand for a simple method for producing layered silicate with reduced amounts of cristobalite impurities.

According to a first aspect of the present disclosure, there is provided a lump of a swellable synthetic layered silicate, the lump comprising a swellable synthetic layered silicate that is sodium tetrasilicic mica , the swellable synthetic layered silicate having an average crystallite size of 14 nm to 18 nm as determined from an X-ray diffraction peak of the (060) plane, and a cristobalite content of less than 1 mass% as calculated by the method described below .
[Method for measuring cristobalite content]
0.800±0.001 g of the ore powder and 0.200±0.001 g of alumina as an internal standard substance are weighed out and mixed together. The mixed sample is measured using an X-ray diffractometer. In the X-ray diffraction chart, the integrated intensity I1 (cps) of the cristobalite peak near 2θ=31.4° _and the integrated intensity I2 (cps) of the alumina peak near 2θ=25.6° _are read, and the cristobalite content X in the ore is calculated using the following formula.
X (mass%)=(I ₁ /I ₂ )/a=I ₁ /(I ₂ ×a)
In the formula, a represents the slope of the calibration curve, which is 0.0462.

According to a second aspect of the present disclosure, there is provided a powder of swellable synthetic layered silicate which is a pulverized product of a lump of the swellable synthetic layered silicate of the present disclosure . The powder of the swellable synthetic layered silicate has an average particle size of 5 μm to 30 μm. Cristobalite is present in an amount of 2×10 ⁻³ parts by mass or less per part by mass of the powder of the swellable synthetic layered silicate.

According to a third aspect of the present disclosure, there is provided a method for producing an expandable layered silicate, comprising a heating step of heating and melting a mixture of raw materials for synthesizing an expandable layered silicate, and a cooling step of cooling the molten material melted by the heating step to at least 900°C at a cooling rate of 100°C/min or more to produce a lump of the expandable layered silicate.

The amount of cristobalite, an impurity, contained in the lump of swellable synthetic layered silicate of the present disclosure is small. The lump of swellable synthetic layered silicate of the present disclosure makes it possible to obtain a powder of swellable synthetic layered silicate with few impurities.

The powder disclosed herein contains a small amount of cristobalite, an impurity. The powder disclosed herein can reduce the adverse effects caused by cristobalite.

The method for producing layered silicate disclosed herein makes it possible to easily reduce the amount of cristobalite, a by-product contained in swellable synthetic layered silicate.

X-ray diffraction patterns of the products in Test Examples 1 and 4. FIG. 2 is a partially enlarged view of the X-ray diffraction pattern of FIG. 1 . FIG. 2 is a partially enlarged view of the X-ray diffraction pattern of FIG. 1 .

The preferred forms for each of the above aspects are described below.

According to a preferred embodiment of the first aspect, the average crystallite size of the swellable synthetic layered silicate determined from the X-ray diffraction peak of the (060) plane is 14 nm to 18 nm.

According to a preferred embodiment of the first aspect, the swellable synthetic layered silicate is sodium tetrasilicic mica.

According to a preferred embodiment of the first aspect above, each lump weighs 10 g or more.

According to a preferred embodiment of the second aspect, the average crystallite size of the swellable synthetic layered silicate determined from the X-ray diffraction peak of the (060) plane is 14 nm to 18 nm.

According to a preferred embodiment of the second aspect, the powder is in the form of a slurry dispersed in an aqueous medium.

According to a preferred embodiment of the second aspect, the swellable synthetic layered silicate is sodium tetrasilicic mica.

According to a preferred embodiment of the third aspect, the cristobalite content in the lump is 1% by mass or less relative to the mass of the lump.

According to a preferred embodiment of the third aspect, the method for producing a swellable layered silicate further includes a grinding step in which the ore mass is wet or dry ground to produce a layered silicate powder.

According to a preferred embodiment of the third aspect, the swellable layered silicate is sodium tetrasilicic mica.

According to a preferred embodiment of the third aspect, the method for producing a swellable layered silicate does not include a removal step for removing cristobalite contained in the ore mass.

In the following description, reference numbers are added to aid in understanding the invention, and are not intended to limit the invention to the illustrated embodiment. The drawings are intended to aid in understanding the lumps and powders of swellable synthetic layered silicate and the manufacturing method thereof disclosed herein, and are not intended to limit the lumps and powders of swellable synthetic layered silicate and the manufacturing method thereof to the shapes, dimensions, scale, etc. of the drawings. In each embodiment, the same elements are given the same reference numbers.

In the present disclosure, the term "lump" refers to a lump of swellable synthetic layered silicate produced by cooling a melt obtained by melting the raw materials of the swellable synthetic layered silicate. The lump also includes a lump in a state before being crushed into powder. The lump is not limited to a solid lump after the production of the swellable synthetic layered silicate. The lump also includes a lump obtained by dividing or crushing a lump after production into smaller lump. The size of the lump depends on the production scale of the layered silicate and the subsequent processing. The lump can be, for example, 10 grams or more, 100 grams or more, 1 kilogram or more, 10 kilograms or more, 50 kilograms or more, or 100 kilograms or more. The lump can be 200 kilograms or less, 100 kilograms or less, 50 kilograms or less, 10 kilograms or less, 1 kilograms or less, 1 kilograms or less, 100 grams or less, or 50 grams or less. The shape of the lump depends on the shape of the molten body when it is cooled, the shape after it is divided and crushed, etc.

In this disclosure, swellable means that it expands (increases in volume) when it absorbs water. Unless otherwise specified, in this disclosure, swellable synthetic layered silicate refers to synthetic layered silicate in a dry state, i.e., synthetic layered silicate in a non-swollen state.

The swellable layered silicate of the present disclosure can be represented by the following formula:
X _1/3~1 Y _2~3 Z ₄ O ₁₀ F ₂
In the above formula, the elements which can be substituted at the X, Y and Z positions are shown in the form of ions as follows:
X: Na ⁺ , Li ⁺ , K ⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ ;
Y: Mg ²⁺ , Li ⁺ , Ni ²⁺ , B ³⁺ , Co ³⁺ , Zn ²⁺ , Mn ³⁺ , Al ³⁺ , Cr ³⁺ , Fe ²⁺ , Fe ³⁺ ;
Z: Al ³⁺ , Si ⁴⁺ , Ge ⁴⁺ , B ³⁺ , Fe ³⁺ , Ti ⁴⁺ .

Examples of layered silicates include swellable mica. Examples of mica include sodium tetrasilicic mica (NaMg _2.5 (Si ₄ O ₁₀ )F ₂ ).

This section describes the swellable synthetic layered silicate ore lump according to the first embodiment of the present disclosure.

The ore mass contains a swellable synthetic layered silicate. The content of the swellable synthetic layered silicate can be 99% by mass or more, 99.5% by mass or more, or 99.9% by mass or more based on the mass of the ore mass. If no impurities are detected, the ore mass can be considered to be substantially 100% by mass of swellable synthetic layered silicate.

The amount of cristobalite in the ore mass is preferably less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on the mass of the ore mass. It is even more preferable that the amount of cristobalite in the ore mass is below the detection limit in quantitative analysis based on X-ray diffraction. Cristobalite is a by-product in the production of swellable synthetic layered silicates.

The cristobalite content in the ore lump can be measured, for example, by quantitative analysis using an internal standard method based on X-ray diffraction. In the internal standard method, a calibration curve showing the correlation between the integrated intensity of the X-ray diffraction peak of cristobalite and an internal standard sample (e.g., alumina) is created to quantify cristobalite. The calibration curve can be created by measuring the X-ray diffraction patterns of a plurality of mixtures of cristobalite and an internal standard sample with different amounts of cristobalite, and plotting the integrated intensity I ₁ of the peak derived from cristobalite / the integrated intensity I ₂ of the peak derived from the internal standard sample against the amount X of cristobalite. The slope a is obtained from the created calibration curve. A predetermined amount of the internal standard sample is added and mixed into the measurement sample for quantifying cristobalite, and the X-ray diffraction pattern of the measurement sample is measured. The integrated intensity I ₁ of a given cristobalite peak (for example, the integrated intensity of a peak (Miller index (hkl): 102) near 2θ=31.4°) and the integrated intensity I ₂ of an internal standard sample peak (for example, in the case of alumina, the integrated intensity of a peak (Miller index (hkl): 012) near 2θ=25.5°) are read. The cristobalite content X (mass %) can be calculated from the following formula.
X (mass%)=(I ₁ /I ₂ )/a=I ₁ /(I ₂ ×a)

The average crystallite size of the swellable synthetic layered silicate is preferably 14 nm or more. The average crystallite size is preferably 18 nm or less. When the swellable synthetic layered silicate is synthetic mica, the crystallite size can be calculated from the following formula based on the X-ray diffraction peak of the (060) plane. The average crystallite size can be the average value of three measurements.
D=Kλ/(Bcosθ)
D: crystallite size (nm), K: Scherrer constant, λ: X-ray wavelength (nm), B: diffraction line width (full width at half maximum (FWHM)) (radian), θ: Bragg angle (radian)

The content of impurities, particularly cristobalite, contained in the lump of swellable synthetic layered silicate according to the first embodiment of the present disclosure is very low, less than 1 mass %. This makes it possible to obtain a powder of swellable synthetic layered silicate with few impurities, i.e., the powder according to the second embodiment, simply by crushing the lump.

The powder according to the second embodiment of the present disclosure will now be described.

The powder includes a powder of swellable synthetic layered silicate. The powder of swellable synthetic layered silicate can be obtained by pulverizing the ore mass according to the first embodiment. The particle shape of the powder can be, for example, a plate shape, a flake shape, a scale shape, or the like.

The average particle size of the particles (including the swellable synthetic layered silicate) in the powder is not particularly limited. The powder can have an average particle size according to the purpose. The average particle size can be the median particle size (the median value of the particle size). For example, the median particle size of the powder can be 0.1 μm or more, 1 μm or more, 2 μm or more, 5 μm or more, 7 μm or more, or 10 μm or more. The median particle size can be 200 μm or less, 100 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, or 5 μm or less. The median particle size can be measured, for example, by laser diffraction particle size distribution measurement.

The average thickness of the particles in the powder (including the swellable synthetic layered silicate) can be, for example, 1 nm or more, 5 nm or more, 10 nm or more, 50 nm or more, 0.1 μm or more, and 0.3 μm or more. The average thickness of the particles in the powder can be, for example, 1 μm or less, 0.5 μm or less, 0.3 μm or less, 0.2 μm or less, 0.1 μm or less, or 80 nm or less. There are no particular limitations on the method for measuring the average thickness, but for example, the thicknesses of any number of particles can be measured by tilted observation with an electron microscope, and the average thickness can be calculated.

The average aspect ratio (median particle size/average thickness) of the particles in the powder (including the swellable synthetic layered silicate) can be, for example, 20 or more, 50 or more, 70 or more, 100 or more, 200 or more, 300 or more, 400 or more, or 500 or more. The upper limit of the average aspect ratio of the particles in the powder is not particularly limited, and is preferably 10,000 or less from the viewpoint of viscosity. The average aspect ratio of the particles in the powder can be, for example, 5,000 or less, 4,000 or less, 3,000 or less, 2,000 or less, 1,000 or less, 500 or less, 400 or less, 300 or less, 200 or less, 150 or less, 100 or less, or 80 or less. The method for determining the average aspect ratio is not particularly limited, but can be calculated, for example, by measuring the particle size and thickness of any number of particles determined by tilt observation with an electron microscope, and dividing the obtained value of the median particle size by the value of the average thickness.

The crystallite size of the swellable synthetic layered silicate in the powder can be the same as in the first embodiment. It is believed that the smaller crystallite size allows the particles to be thinner.

The content of the swellable synthetic layered silicate powder in the powder can be 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, or 99.9% by mass or more, based on the mass of the powder. In addition, if no other powders or impurities are detected in the powder, the content of the swellable synthetic layered silicate in the powder can be considered to be 100% by mass. The method for quantifying the swellable synthetic layered silicate in the powder can be appropriately selected depending on the other powders contained. For example, an internal standard method based on X-ray diffraction is an option. In addition, if the swellable synthetic layered silicate contains fluorine, a fluorine component analysis is an option.

In the powder of the present disclosure, the amount of cristobalite is preferably 2×10 ⁻³ parts by mass or less , preferably 1.5×10 ⁻³ parts by mass or less, more preferably 1×10 ⁻³ parts by mass or less, even more preferably 5×10 ⁻⁴ parts by mass or less, and particularly preferably 1×10 ⁻⁴ parts by mass or less, per part by mass of the swellable synthetic layered silicate. The amount of cristobalite is more preferably below the detection limit. The amount of cristobalite in the powder can be measured by quantitative analysis using the internal standard method based on X-ray diffraction described above.

The powders disclosed herein may also contain powders other than swellable synthetic layered silicates.

The powder of the present disclosure may be in the form of a dry powder. The powder of the present disclosure may also be in the form of a slurry (suspension) dispersed in a dispersion medium. Examples of the dispersion medium that may be used include water, lower alcohols such as ethanol, and mixtures thereof. The content of the powder (in a dry state) in the slurry may be, for example, 0.1% by mass or more, 3% by mass or more, or 10% by mass or more relative to the mass of the slurry. The content of the powder in the slurry may be, for example, 50% by mass or less, 30% by mass or less, or 15% by mass or less relative to the mass of the slurry.

In the powder of the present disclosure, the relative amount of cristobalite to the swellable synthetic layered silicate is low. This can reduce the adverse effects of cristobalite. For example, when the powder of the present disclosure is a synthetic mica powder, when the powder of the present disclosure is applied to a skin topical agent, the foreign body sensation caused by cristobalite can be reduced and the user can obtain a smoother feeling of use than when a synthetic mica powder containing about 2 to 10% cristobalite is applied. In addition, when the powder of the present disclosure is applied to the skin, it can be made to adhere more closely to the skin and to be less likely to fall off. Furthermore, when the powder of the present disclosure is applied to a gas barrier film, the barrier performance can be improved compared to when a synthetic mica powder containing about 2 to 10% cristobalite is applied.

A method for producing layered silicate according to the third embodiment of the present disclosure will be described.

The manufacturing method disclosed herein includes a heating step for melting the raw material of the layered silicate, and a cooling step for cooling the melt melted in the heating step.

As the raw material of the layered silicate, those used in the conventional internal heat melting method can be used. For example, raw materials containing the constituent elements of the above-mentioned swellable synthetic layered silicate may be mixed and used according to the desired chemical composition. For example, when the swellable layered silicate is sodium tetrasilicic mica (NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ ), a mixture of SiO ₂ , MgO and Na ₂ SiF ₆ in a molar ratio of 3.15-3.85:2.25-2.75:0.45-0.55 may be used as the raw material. In addition, natural minerals such as feldspar, olivine, and talc may be used as the Si, Al, and Mg sources. When the X, Y, and Z are replaced with other elements, the oxide, fluoride, carbonate, etc. of the element to be replaced may be blended and melted in the mixture of the compounds exemplified above.

As a melting furnace for melting the raw materials, for example, a general internally heated melting furnace, an externally heated melting furnace, a high-frequency induction heating furnace, etc. can be used. Among them, a high-frequency induction heating furnace is preferably used. When an internally heated melting furnace or a high-frequency induction heating furnace is used, the heating time required for melting can be adjusted to be short by reducing the actual amount of raw materials input from the standard input amount. Also, in an externally heated melting furnace, instead of putting the mixed raw materials into the furnace at room temperature, the inside of the furnace is heated in advance and the raw materials are input when the temperature inside the furnace reaches 1200°C or higher, thereby adjusting the heating time required for melting to be short.

The heating temperature for melting the raw materials is 1200°C to 1800°C, preferably 1400°C to 1600°C.

In the cooling step, the molten body is quenched at a cooling rate of 100°C/min or more, preferably 150°C/min or more, and more preferably 200°C/min or more. Quenching is preferably performed in a temperature range from the molten state to at least 900°C. Temperatures below 900°C may be allowed to cool naturally. If the quenching rate is 100°C/min or more, the amount of cristobalite, a by-product, produced can be reduced. The temperature in the cooling step is the outer surface temperature (radiation temperature) of the molten body.

The method for quenching the molten body is not particularly limited and may be any method. For example, the molten body may be quenched in a mold equipped with a water-cooling jacket after being removed from the furnace, or in a cooling bed. The mold may be cooled by either water cooling or air cooling. The cooling bed may have a structure equipped with a cooling jacket.

This allows the production of the swellable synthetic layered silicate according to the first embodiment. The cristobalite content in the ore mass obtained by the cooling process can be the content in the ore mass shown above.

The method for producing layered silicate according to the third embodiment may further include a grinding step in which at least a portion of the lump obtained in the cooling step is ground to produce a layered silicate powder. The grinding method is not particularly limited and may be any method. For example, first, the lump of swellable layered silicate is coarsely ground using a general crusher such as a jaw crusher or a hammer crusher. After this, the coarsely ground raw material is powdered using a dry grinder such as a hammer mill, a roll mill, or a Raymond mill to produce a layered silicate powder. The grinding method may be a wet method or a dry method. The grinding can be performed so that the powder has a desired average particle size. The powder according to the second embodiment can be produced by the grinding step. The content of cristobalite in the powder obtained by the grinding step may be the content in the powder shown above.

When grinding in a wet manner, grinding can be performed in an aqueous medium. Examples of the aqueous medium that can be used include water and alcohols including ethanol. After grinding, a slurry (suspension) can be obtained in which the swellable synthetic layered silicate is dispersed.

By dispersing the powder obtained by the grinding process in an aqueous medium, a slurry in which the swellable synthetic layered silicate powder is dispersed can be obtained.

The method for producing a layered silicate according to the third embodiment does not need to include a removal step for removing cristobalite. Examples of the removal step include a method of classifying the powder to remove cristobalite, a method of heating the ore lump or powder to remove cristobalite, and a method of treating the powder with alkali to remove cristobalite. This can reduce the number of steps.

When the by-product cristobalite is contained in the ore and powder produced by a method other than that disclosed herein at 5% by mass or more, it is difficult to reduce the cristobalite content to 1% by mass or less even with the removal method described above.

The method for producing layered silicate according to the third embodiment makes it possible to produce the lump of swellable synthetic layered silicate according to the first embodiment and the powder according to the second embodiment.

According to the method for producing layered silicate according to the third embodiment, it is possible to suppress the production of cristobalite, a by-product, during the synthesis of layered silicate. This makes it possible to produce layered silicate with high purity.

The layered silicate ore masses and powders of the present disclosure may be difficult or impractical to directly identify by their composition, structure, identity, etc. In such cases, the layered silicate ore masses and powders of the present disclosure should be allowed to be identified by their manufacturing method.

Below, examples of the layered silicate lump, powder, and method for producing layered silicate of the present disclosure are described. However, the layered silicate lump, powder, and method for producing layered silicate are not limited to the following examples.

[Test Example 1]
100 kg of molten raw material containing 51.9 kg of silicon dioxide, 24.9 kg of magnesium oxide, and 23.2 kg of sodium silicofluoride was heated to 1450°C in an internally heated melting furnace using carbon electrodes and then held for 10 minutes to melt the raw material mixture. The molten material was removed from the furnace, placed in an iron mold equipped with a water-cooling jacket, and quenched to 900°C at a cooling rate of 203°C/min. The material was then cooled to room temperature and crystallized to obtain a lump of sodium tetrasilicic mica, a swellable synthetic layered silicate. The cristobalite content of the obtained lump was measured.

[Test Example 2]
Except for the cooling rate, the ore lump was prepared in the same manner as in Test Example 1. In Test Example 2, the melt was quenched at a cooling rate of 115° C./min. The cristobalite content of the obtained ore lump was measured.

[Test Example 3]
Except for the cooling method, ore lumps were prepared in the same manner as in Test Example 1. In Test Example 3, the molten material was poured into a cooling bed equipped with a water-cooling jacket and quenched at a cooling rate of 321° C./min. The cristobalite content of the obtained ore lumps was measured.

[Test Example 4]
100 kg of molten raw material mixed with the chemical composition of sodium tetrasilicic mica was heated to 1450°C in an internally heated melting furnace using carbon electrodes and held for 10 minutes to melt the raw material mixture. The melt was removed from the furnace, placed in an iron mold, and cooled to 900°C at a cooling rate of 36°C/min. It was then cooled to room temperature and crystallized to obtain a lump. The cristobalite content of the obtained lump was measured.

[Measurement of Cristobalite Content]
The amount of cristobalite produced in each test example was measured by an internal standard method based on X-ray diffraction. Alumina was used as the internal standard substance. A calibration curve was created in advance to identify the amount of cristobalite produced. The X-ray diffraction patterns were measured for mixtures of 20% by mass of alumina, cristobalite and calcium fluoride (remainder, dilution material) with the proportion of cristobalite changed to 1% by mass, 10% by mass, 25% by mass, and 50% by mass. For each X-ray diffraction chart, the integrated intensity I ₂ of the alumina peak (Miller index (hkl): 012) near 2θ = 25.6 ° and the integrated intensity I ₁ of the cristobalite peak (Miller index (hkl): 102) near 2θ = 31.4 ° were read. Then, the integrated intensity I ₁ of the cristobalite peak / the integrated intensity I ₂ of the alumina peak was plotted against the cristobalite content to create a calibration curve. The slope a of the created calibration curve was measured. The slope a of the calibration curve thus prepared was 0.0462.

Next, the X-ray diffraction pattern of the ore lump obtained in each test example was measured. First, the ore lump obtained in each test example was powdered and dried. Next, 0.800±0.001 g of the powder of each test example and 0.200±0.001 g of alumina as an internal standard were weighed and mixed. The X-ray diffraction pattern of the mixed sample was measured using Cu-Kα radiation with an X-ray diffractometer (MiniFlex600-C (manufactured by Rigaku Corporation)). In each X-ray diffraction chart, the integrated intensity I ₁ (cps) of the cristobalite peak (Miller index (hkl): 102) near 2θ = 31.4 ° and the integrated intensity I ₂ (cps) of the alumina peak (Miller index (hkl): 012) near 2θ = 25.6 ° were read. Then, the cristobalite content X contained in the synthetic mica produced in each test example was calculated from the following formula. The measurement results of the cristobalite content are shown in Table 1. In Table 1, "less than 0.1" indicates that the cristobalite content was below the detection limit because no significant peak of cristobalite could be detected, i.e., the integrated intensity of the cristobalite peak was zero.

X (mass%) = ( _I1 / _I2 )/0.0462 = _I1 /( _I2 x 0.0462)

Figure 1 shows a comparison of the X-ray diffraction patterns of the products in Test Example 1 and Test Example 4. Figure 2 shows an enlarged view of the cristobalite peak in the X-ray diffraction pattern shown in Figure 1. Figure 3 shows an enlarged view of the alumina (internal standard) peak in the X-ray diffraction pattern shown in Figure 1.

As shown in Figures 1 and 2 , in Test Examples 1 to 3 in which the cooling rate was 100°C/min or more, cristobalite was not detected in the X-ray diffraction patterns. On the other hand, in Test Example 4 in which the cooling rate was 36°C/min, 9.6 mass% of cristobalite was detected in the lump. This shows that the production of the by-product cristobalite can be suppressed by setting the cooling rate of the raw material melt to 100°C/min or more.

[Test Example 5]
5 g of the sodium tetrasilicic mica lump prepared in Test Example 1 was added to 100 ml of ion-exchanged water and stirred for 12 hours, after which it was classified by a centrifuge to obtain a slurry with an average particle size of 10 μm. The slurry had sufficient viscosity and was suitable as a coating material.

Even when the ore mass was crushed and converted into powder form, the cristobalite content in the powder and the amount of cristobalite per part by mass of synthetic mica were the same as in Test Examples 1 to 4.

[Test Example 6: Measurement of crystallite size]
The crystallite size was measured for the synthetic micas produced in Test Examples 1 to 4. The crystallite size was calculated from the following formula by measuring the half-width of the peak at about 2θ = 61° derived from the (060) plane by X-ray diffraction. CuKα rays were used for the X-rays, and λ = 0.154 nm. K was 0.89. The crystallite size was the average value of three X-ray diffraction measurements. The measurement results are shown in Table 2.

D=Kλ/(Bcosθ)
D: crystallite size (nm), K: Scherrer constant, λ: X-ray wavelength (nm), B: half-width (rad), θ: Bragg angle (rad)

The synthetic mica powders of Test Examples 6-1 to 6-3 produced in Test Examples 1 to 3 had smaller crystallite sizes than the synthetic mica powder of Test Example 6-4 produced in Test Example 4. It is believed that the crystallites were smaller because the synthetic mica of Test Examples 6-1 to 6-3 was crystallized by rapid cooling. It is believed that the smaller crystallite size allows the particles of the swellable synthetic layered silicate to be made thinner.

[Test Example 7: Friction test]
The effect of the content of cristobalite in the swellable synthetic layered silicate on the frictional sensation when the swellable synthetic layered silicate is applied was tested. In the friction test, the mean friction coefficient (MIU) and the mean deviation of the friction coefficient (MMD) were measured. MIU represents the slipperiness felt by the applicator when the swellable synthetic layered silicate powder is applied. The smaller the MIU value, the more slipperiness the applicator feels. The MIU value is preferably less than 0.8. MMD represents the smoothness and roughness felt by the applicator when the swellable synthetic layered silicate powder is applied. The smaller the MMD value, the more smooth the applicator feels.

For the friction test, the synthetic mica lump produced in Test Example 1, which had a cristobalite content below the detection limit (less than 0.1% by mass), and the synthetic mica lump produced in Test Example 4, which contained 9.6% by mass of cristobalite, were each pulverized by a Raymond mill. The lump in Test Examples 1 and 4 was pulverized to the same extent by the same method. The powders in Test Examples 7-1 and 7-3 were from the same lot. The powders in Test Examples 7-2 and 7-4 were from the same lot. For the friction test, a friction tester KES-KS (manufactured by Kato Tech Co., Ltd.) using a silicon sensor was used. The test was performed by applying 0.01 g of powder uniformly on artificial leather. The powder in each test example was measured three times, and the average value was calculated. The measurement results of MIU are shown in Table 3. The measurement results of MMD are shown in Table 4. The measurement conditions are as follows;
SENS:H
Frictional static load: 25gf
Measurement distance: 20 mm
Measurement speed: 1mm/sec
Sensor: 10mm square sensor Temperature: 20.5℃±2℃
Humidity: 60% ±2°C

The MIU of Test Examples 7-1 and 7-2 was less than 0.8, and both were slippery powders. The powder of Test Example 7-3 was smoother and less rough than Test Example 7-4. The particle shape of synthetic mica is flat (scaly), but the particle shape of cristobalite is other than flat. For this reason, the powder obtained from Test Example 1 was free of foreign matter and was therefore smoother and less rough. This demonstrated that the powder of the present disclosure is suitable for application to the skin.

The powder in Test Example 7-3 also had a smaller MMD value, which means that when the powder is applied, it has fewer irregularities and is easier to align uniformly and densely. This demonstrates that the powder of the present disclosure is also suitable for improving gas barrier properties, as shown in Test Example 8 below.

[Test Example 8: Gas Barrier Test]
The synthetic mica powder produced in Test Example 1, which had a cristobalite content below the detection limit (less than 0.1 mass%), and the synthetic mica powder produced in Test Example 4, which contained 9.6 mass% cristobalite, were coated with a film to test the gas barrier performance (water vapor permeability).

The gas barrier test was conducted in accordance with the cup method (JIS Z0208). For the gas barrier test, the ore lump produced in Test Example 1 and the ore lump produced in Test Example 4 were each pulverized in a Raymond mill to produce powder. The ore lump in Test Examples 1 and 4 were pulverized to the same extent by the same method.

The synthetic mica powder of each test example was dispersed in water to prepare a slurry. A polyurethane water-soluble resin (Takelac (registered trademark) WPB-341 (Mitsui Chemicals MC Co., Ltd.)) was added to this slurry so that the total mass of the powder and the water-soluble resin was 15% by mass relative to the mass of the slurry, and mixed to prepare a coating liquid. Coating liquids were prepared with different contents of synthetic mica powder in the coating liquid, namely, no addition (0% by mass), 10% by mass, and 20% by mass relative to the total mass of the water-soluble resin and the powder. Next, the coating liquid was applied to a polyethylene terephthalate film (PET film) having a thickness of 12 μm so that the thickness before drying was 10 μm, and dried in a dryer. The test cup with the obtained film attached and containing 7 g of calcium chloride as a moisture absorbent was left to stand for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 40° C. and a humidity of 90% RH. The water vapor transmission rate (WVTR) was calculated from the following formula. The water vapor permeability was calculated from the following formula: Table 5 shows the measurement results (g/( ^m2 ·day)).

WVTR (g/(m ² ·day))=(mass of test cup after water vapor exposure (g)−mass of test cup before water vapor exposure (g))/film area (m ² )

The higher the water vapor permeability value shown in Table 5, the lower the gas barrier performance of the film. Films coated with synthetic mica containing a low amount of cristobalite had higher gas barrier performance than films coated with synthetic mica containing a high amount of cristobalite. It is believed that the gas barrier performance was improved by reducing the gap between the powder and the PET film when there was less cristobalite, an impurity. It is also believed that the gas barrier performance was improved because the powder particles were thinner.

[Test Example 9: Cristobalite Removal Test by Alkaline Treatment]
The synthetic mica powder prepared in the above-mentioned Test Example 4 was subjected to alkali treatment to remove cristobalite. Synthetic mica powder containing 9.6% by mass of cristobalite was prepared from the lump prepared in Test Example 4, and the powder was dispersed in water to a concentration of 5% by mass to prepare a slurry. Sodium hydroxide, sodium carbonate, or magnesium hydroxide was added to the slurry in the amounts shown in Table 6 and heated at 95°C to 98°C for 5 hours. After the heat treatment, the treated product was dried and pulverized into powder. The content of cristobalite was measured by an internal standard method based on X-ray diffraction. The alkali treatment conditions and the amount of remaining cristobalite are shown in Table 6. Test Examples 9-2 to 9-4 are synthetic mica of the same production lot as Test Example 9-1 that was alkali treated. The reduction rate shown in Table 6 is the change rate relative to the content of cristobalite in Test Example 9-1.

Most of the cristobalite remained in both alkali treatments. It was found that it is difficult to reduce the cristobalite content to 1 mass% or less using alkali treatment.

[Test Example 10: Cristobalite Removal Test by Heat Treatment]
An attempt was made to remove cristobalite by heat treatment of synthetic mica powder made from the lump made in Test Example 4 above. 20 g of powder was heat treated at 450°C, 650°C, and 850°C, respectively. The heat treatment conditions, and the content and rate of change of cristobalite are shown in Table 7. Test Examples 10-2 to 10-4 were made by heat treating synthetic mica of the same production lot as Test Example 10-1. The rate of change shown in Table 7 is the rate of change relative to the content of cristobalite in Test Example 10-1.

Cristobalite tended to decrease when the powder was heat-treated. However, most of the cristobalite remained in all heat treatments. It was found that it is difficult to reduce the cristobalite content to 1 mass% or less through heat treatment.

[Test Example 11: Cristobalite Removal Test by Classification]
The synthetic mica powder prepared in the above Test Example 4 was subjected to a classification process to remove cristobalite. The classification process was carried out by dispersing the swellable synthetic layered silicate in water and then centrifuging it. The synthetic mica was reduced by about 30% by mass compared to before classification, but the content of cristobalite did not change. Therefore, it was found that it is difficult to remove cristobalite by classification.

The swellable synthetic layered silicate, powder and manufacturing method thereof of the present invention have been described based on the above embodiments and examples, but are not limited to the above embodiments and examples, and may include various modifications, changes and improvements to each disclosed element (including elements described in the claims, specification and drawings) within the scope of the present invention and based on the basic technical idea of the present invention. Furthermore, various combinations, substitutions or selections of each disclosed element are possible within the scope of the claims of the present invention.

Further objects, objectives and forms (including modifications) of the present invention will become apparent from the entire disclosure of the present invention, including the claims.

Regarding the numerical ranges set forth herein, any numerical value or range falling within the range should be construed as being specifically set forth herein, even if not otherwise specified.

The swellable synthetic layered silicate, powder, mixed powder, and the manufacturing method thereof disclosed herein can be applied to, for example, cosmetics, paints, metal ion adsorbents, films, nanocomposite materials, gas barrier improving materials for paper, films, paints, and other materials, viscosity adjusters for inks, paints, and cosmetics, modifiers for resins, etc., flame retardant materials, chemical resistant materials, ion adsorbents, gasket materials, lubricants, conductive materials, laser marking materials, thermal recording materials, dispersants, drawing materials, dispersants, etc.

Claims (9)

containing a swellable synthetic layered silicate which is sodium tetrasilicic mica ;
The average crystallite size of the swellable synthetic layered silicate determined from the X-ray diffraction peak of the (060) plane is 14 nm to 18 nm;
A lump of swellable synthetic layered silicate having a cristobalite content of less than 1 mass% as determined by the method described below .
[Method for measuring cristobalite content]
0.800±0.001 g of the ore powder and 0.200±0.001 g of alumina as an internal standard substance are weighed out and mixed together. The mixed sample is measured using an X-ray diffractometer. In the X-ray diffraction chart, the integrated intensity I1 (cps) of the cristobalite peak near 2θ=31.4° _and the integrated intensity I2 (cps) of the alumina peak near 2θ=25.6° _are read, and the cristobalite content X in the ore is calculated using the following formula.
X (mass%)=(I ₁ /I ₂ )/a=I ₁ /(I ₂ ×a)
In the formula, a is the slope of the calibration curve, which is 0.0462. 2. The lump according to claim 1, wherein the average crystallite size of the swellable synthetic layered silicate determined from the (060) plane X-ray diffraction peak is 15.4 nm to 17.1 nm . 3. The swellable synthetic layered silicate lump according to claim 1 or 2, wherein the cristobalite content is 0.1 mass% or less. The ore lump according to any one of claims 1 to 3, each lump weighing 10 g or more. A powder of swellable synthetic layered silicate which is a pulverized product of a lump of the swellable synthetic layered silicate according to any one of claims 1 to 4 ,
The powder of the swellable synthetic layered silicate has an average particle size of 5 μm to 30 μm ;
The powder of swellable synthetic layered silicate has 2×10 ⁻³ parts by mass or less of cristobalite per part by mass of the powder of the swellable synthetic layered silicate . The powder according to claim 5, wherein the average crystallite size of the swellable synthetic layered silicate determined from the X-ray diffraction peak of the (060) plane is 14 nm to 18 nm. The powder according to claim 5 or 6, wherein the powder is in the form of a slurry dispersed in an aqueous medium. The powder according to any one of claims 5 to 7, wherein the swellable synthetic layered silicate is sodium tetrasilicic mica. The powder according to any one of claims 5 to 8, wherein cristobalite has not been removed from the pulverized product.