Method for producing swellable layered silicate and method for reducing cristobalite

Abstract

To provide a method for producing a swellable layered silicate capable of producing a swellable synthetic layered silicate having a reduced amount of cristobalite impurities, and a method for reducing cristobalite.SOLUTION: A method for producing a swellable layered silicate comprises a heating step of heating and melting a mixture of raw materials for synthesizing the swellable 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 mineral mass of the swellable layered silicate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a swellable layered silicate. The present disclosure also relates to a method for reducing cristobalite. [Background technology]

[0002] A 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 blended 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.

[0003] Patent Document 2 describes a method for producing synthetic hectorite, in which a smectite clay mineral containing cristobalite is treated with alkali under conditions in which the crystal structure of the cristobalite substantially disappears. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4216510 [Patent Document 2] Japanese Unexamined Patent Publication No. 62-59518 Summary of the Invention [Problem to be solved by the invention]

[0005] In a typical melt synthesis method, cristobalite is produced as an impurity. In the method described in Patent Document 1, the raw materials are rapidly melted to reduce the amount of cristobalite impurity in the swellable synthetic layered silicate ore mass. However, even with the method described in Patent Document 1, the swellable synthetic layered silicate ore mass still contains 3% by volume (approximately 2.6% by mass) of cristobalite, and it is expected that the cristobalite content can be further reduced.

[0006] Swellable synthetic layered silicates are usually powdered by crushing ore lumps. Therefore, removal of cristobalite by classification after crushing has also been considered. However, classification treatments are difficult to reduce the amount of cristobalite, and also result in significant loss of swellable synthetic layered silicates.

[0007] 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. Furthermore, adding an additional step such as alkali treatment increases the production cost of the swellable synthetic layered silicate.

[0008] Therefore, there is a need for lumps and powders of swellable synthetic layered silicates with reduced amounts of cristobalite impurities, and there is also a need for a simple method for producing layered silicates with reduced amounts of cristobalite impurities. [Means for solving the problem]

[0009] According to a first aspect of the present disclosure, there is provided a nugget of swellable synthetic layered silicate, comprising a swellable synthetic layered silicate and having a cristobalite content of less than 1 mass %.

[0010] According to a second aspect of the present disclosure, there is provided a powder containing a powder of swellable synthetic layered silicate. The swellable synthetic layered silicate is a powder having an average particle size of 5 μm to 30 μm. Cristobalite is present in an amount of 2×10 per part by mass of the swellable synthetic layered silicate. -3 parts by mass or less.

[0011] 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 produced in the heating step to at least 900°C at a cooling rate of 100°C / min or more to produce a mass of the expandable layered silicate. [Effects of the Invention]

[0012] The amount of cristobalite, an impurity, contained in the lump of swellable synthetic layered silicate of the present disclosure is small, and the lump of swellable synthetic layered silicate of the present disclosure can produce a powder of swellable synthetic layered silicate with few impurities.

[0013] The powder of the present disclosure contains a small amount of cristobalite, an impurity, and the powder of the present disclosure can reduce the adverse effects caused by cristobalite.

[0014] According to the method for producing a layered silicate of the present disclosure, the amount of cristobalite, a by-product contained in a swellable synthetic layered silicate, can be reduced in a simple manner. [Brief explanation of the drawings]

[0015] [Figure 1] X-ray diffraction patterns of the products in Test Examples 1 and 4. [Figure 2] Enlarged view of the X-ray diffraction pattern in Figure 1. [Figure 3] Enlarged view of the X-ray diffraction pattern in Figure 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of each of the above aspects will be described below.

[0017] According to a preferred embodiment of the first aspect, the swellable synthetic layered silicate has an average crystallite size of 14 nm to 18 nm as determined from the X-ray diffraction peak of the (060) plane.

[0018] According to a preferred embodiment of the first aspect, the swellable synthetic layered silicate is sodium tetrasilicic mica.

[0019] According to a preferred embodiment of the first aspect, each lump weighs 10 g or more.

[0020] According to a preferred embodiment of the second aspect, the swellable synthetic layered silicate has an average crystallite size of 14 nm to 18 nm as determined from the X-ray diffraction peak of the (060) plane.

[0021] According to a preferred embodiment of the second aspect, the powder is in the form of a slurry dispersed in an aqueous medium.

[0022] According to a preferred embodiment of the second aspect, the swellable synthetic layered silicate is sodium tetrasilicic mica.

[0023] According to a preferred mode of the third aspect, the content of cristobalite in the lump is 1 mass % or less relative to the mass of the lump.

[0024] According to a preferred embodiment of the third aspect, the method for producing a swellable layered silicate further comprises a grinding step of wet or dry grinding the ore mass to produce a powder of the layered silicate.

[0025] According to a preferred embodiment of the third aspect, the swellable layered silicate is sodium tetrasilicic mica.

[0026] According to a preferred mode of the third aspect, the method for producing an expandable layered silicate does not include a removal step for removing cristobalite contained in the ore mass.

[0027] In the following description, reference numerals to the drawings are used to aid in understanding the invention and are not intended to limit the invention to the illustrated embodiments. Furthermore, the drawings are intended to aid in understanding the lumps and powders of swellable synthetic layered silicate and their manufacturing methods of the present disclosure, but are not intended to limit the lumps and powders of swellable synthetic layered silicate and their manufacturing methods to the shapes, dimensions, scales, etc. of the drawings. In each embodiment, the same elements are designated by the same numerals.

[0028] In this disclosure, the term "lump" refers to a lump of swellable synthetic layered silicate produced by cooling a melt obtained by melting raw materials for the swellable synthetic layered silicate. The lump also includes a lump in a state before being crushed into powder. Furthermore, the lump is not limited to a solid lump of swellable synthetic layered silicate after production. The lump also includes a lump obtained by dividing or crushing a lump into smaller lump after production. The size of the lump depends on the scale of production of the layered silicate and 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 also be 200 kilograms or less, 100 kilograms or less, 50 kilograms or less, 10 kilograms or less, 1 kilograms or less, 100 grams ...50 grams or less, or 50 grams or less. The shape of the lump depends on the shape of the molten material upon cooling, the shape after division and crushing, etc.

[0029] In this disclosure, swellable refers to the ability to expand (increase in volume) when it absorbs water. Unless otherwise specified, in this disclosure, swellable synthetic layered silicate refers to a synthetic layered silicate in a dry state, i.e., a synthetic layered silicate in an unswollen state.

[0030] The swellable layered silicate of the present disclosure can be represented by the following formula: X 1 / 3~1 Y 2~3 Z4O 10 F2 In the above formula, the elements that 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+ .

[0031] Examples of layered silicates include swellable mica. Examples of mica include sodium tetrasilicic mica (NaMg 2.5 (SiO 10 )F2) can be mentioned.

[0032] A lump of swellable synthetic layered silicate according to the first embodiment of the present disclosure will be described.

[0033] 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 essentially 100% by mass of the swellable synthetic layered silicate.

[0034] The amount of cristobalite in the ore lump 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 lump. The amount of cristobalite in the ore lump is preferably 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.

[0035] The cristobalite content in a mineral ingot 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 is created to quantify cristobalite, showing the correlation between the integrated intensity of the X-ray diffraction peaks of cristobalite and an internal standard sample (e.g., alumina). The calibration curve can be created by measuring the X-ray diffraction patterns of multiple mixtures of cristobalite and the internal standard sample, each containing varying amounts of cristobalite, and plotting the integrated intensity I1 of the cristobalite-derived peak / integral intensity I2 of the internal standard sample peak against the amount X of cristobalite. The slope a is then determined from the created calibration curve. A predetermined amount of the internal standard sample is added to and mixed with the measurement sample for quantifying cristobalite, and the X-ray diffraction pattern of the measurement sample is measured. The integrated intensity I1 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 I2 of the peak of the internal standard sample (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 using the following formula: X(mass%)=(I1 / I2) / a=I1 / (I2×a)

[0036] The average crystallite size of the swellable synthetic layered silicate is preferably 14 nm or more. Furthermore, 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 X-ray diffraction peak of the (060) plane using the following formula. The average crystallite size can be the average 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)

[0037] 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 extremely low, less than 1% by mass, so that a powder of swellable synthetic layered silicate with few impurities, i.e., the powder according to the second embodiment, can be obtained simply by crushing the lump.

[0038] A powder according to a second embodiment of the present disclosure will now be described.

[0039] 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.

[0040] 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 depending on the purpose. The average particle size can be the median particle size (median value of particle sizes). 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 also 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.

[0041] 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, or 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. The method for measuring the average thickness is not particularly limited, but can be, for example, by measuring the thicknesses of any number of particles using tilted observation with an electron microscope and calculating the average value.

[0042] The average aspect ratio (median particle size / average thickness) of particles in the powder (including swellable synthetic layered silicates) 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 particles in the powder is not particularly limited, but is preferably 10,000 or less from the viewpoint of viscosity. The average aspect ratio of 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 an arbitrary number of particles determined by tilted observation with an electron microscope, and dividing the obtained median particle size value by the average thickness value.

[0043] The crystallite size of the swellable synthetic layered silicate in the powder can be the same as in Embodiment 1. It is believed that the smaller crystallite size allows the particles to be thinner.

[0044] 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. Furthermore, 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. Furthermore, if the swellable synthetic layered silicate contains fluorine, fluorine component analysis is an option.

[0045] In the powder of the present disclosure, cristobalite is used in an amount of 2×10 per part by mass of the swellable synthetic layered silicate. -3 parts by mass or less, preferably 1.5 x 10-3 parts by mass or less, more preferably 1×10 -3 parts by mass or less, more preferably 5×10 -4 parts by mass or less, particularly preferably 1×10 -4 It is preferable that the amount of cristobalite is less than parts by mass. It is more preferable that the amount of cristobalite is less than 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.

[0046] Powders of the present disclosure can also include powders other than swellable synthetic layered silicates.

[0047] The powder of the present disclosure can be in the form of a dry powder. The powder of the present disclosure can also be in the form of a slurry (suspension) dispersed in a dispersion medium. Examples of the dispersion medium that can be used include water, lower alcohols such as ethanol, and mixtures thereof. The content of the powder (dry state) in the slurry can 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 can 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.

[0048] In the powder of the present disclosure, the relative amount of cristobalite to the swellable synthetic layered silicate is low. This reduces the adverse effects of cristobalite. For example, when the powder of the present disclosure is a synthetic mica powder, applying the powder to a skin topical preparation reduces the foreign body sensation caused by cristobalite, compared to applying a synthetic mica powder containing approximately 2 to 10% cristobalite, and the user can enjoy a smoother application experience. Furthermore, when applied to the skin, the powder of the present disclosure adheres more closely to the skin and is less likely to come off. Furthermore, when the powder of the present disclosure is applied to a gas barrier film, the barrier performance can be improved compared to applying a synthetic mica powder containing approximately 2 to 10% cristobalite.

[0049] A method for producing a layered silicate according to a third embodiment of the present disclosure will be described.

[0050] The manufacturing method of the present disclosure includes a heating step of melting a raw material for a layered silicate, and a cooling step of cooling the melt melted in the heating step.

[0051] As the raw material for 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 (SiO 10 In the case of )F2), the raw materials can be a mixture of SiO2, MgO, and Na2SiF6 in a molar ratio of 3.15-3.85:2.25-2.75:0.45-0.55. Natural minerals such as feldspar, olivine, and talc can also be used as sources of Si, Al, and Mg. When X, Y, and Z are to be replaced with other elements, the oxide, fluoride, carbonate, etc. of the element to be replaced can be blended and melted into a mixture of the compounds exemplified above.

[0052] As the 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 charged below the standard amount. Furthermore, in the case of an externally heated melting furnace, instead of charging the blended raw materials into the furnace at room temperature, the furnace can be heated in advance and the raw materials can be charged when the temperature inside the furnace reaches 1200°C or higher, thereby adjusting the heating time required for melting to be short.

[0053] The heating temperature for melting the raw materials is 1200°C to 1800°C, preferably 1400°C to 1600°C.

[0054] In the cooling step, the melt 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 carried out in a temperature range from the molten state to at least 900°C. In a temperature range below 900°C, the melt may be allowed to cool naturally. A quenching rate of 100°C / min or more can reduce the amount of cristobalite produced as a by-product. The temperature in the cooling step is the outer surface temperature (radiation temperature) of the melt.

[0055] The method for quenching the molten body is not particularly limited, and any method may be used. For example, a method in which the molten body is removed from the furnace and then quenched in a mold equipped with a water-cooling jacket, or a method in which the molten body is quenched in a cooling bed, etc. may be applied. The mold may be cooled by either water cooling or air cooling. The cooling bed may have a structure equipped with a cooling jacket.

[0056] This allows the production of the swellable synthetic layered silicate according to the first embodiment. The cristobalite content in the lump obtained by the cooling step can be the content in the lump shown above.

[0057] The method for producing a layered silicate according to the third embodiment can 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 can 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. The coarsely ground raw material is then 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 can be wet or dry. 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 cristobalite content in the powder obtained by the grinding step can be the content in the powder shown above.

[0058] When wet milling is used, milling can be carried out in an aqueous medium. Examples of the aqueous medium that can be used include water and alcohols including ethanol. After milling, a slurry (suspension) in which the swellable synthetic layered silicate is dispersed can be obtained.

[0059] The powder obtained by the milling step is dispersed in an aqueous medium to obtain a slurry in which the powder of the swellable synthetic layered silicate is dispersed.

[0060] The method for producing a layered silicate according to the third embodiment does not necessarily include a removal step of removing cristobalite. Examples of the removal step include a method of removing cristobalite by classifying the powder, a method of removing cristobalite by heating the ore lump or powder, and a method of removing cristobalite by treating the powder with alkali. This allows the number of steps to be reduced.

[0061] When ore nuggets and powders produced without using the manufacturing method of the present disclosure contain 5% by mass or more of the by-product cristobalite, it is difficult to reduce the cristobalite content to 1% by mass or less even with the removal method described above.

[0062] According to the method for producing a layered silicate according to the third embodiment, it is possible to produce the lump of swellable synthetic layered silicate according to the first embodiment and the powder according to the second embodiment.

[0063] According to the method for producing a layered silicate according to the third embodiment, it is possible to suppress the production of cristobalite, a by-product, during the synthesis of the layered silicate, thereby producing a layered silicate with high purity.

[0064] There are cases where it is difficult or even impractical to directly identify the layered silicate nuggets and powders of the present disclosure by their composition, structure, characteristics, etc. In such cases, it should be permitted to identify the layered silicate nuggets and powders of the present disclosure by their manufacturing method. [Example]

[0065] The layered silicate lump, powder, and method for producing the layered silicate of the present disclosure will be described below using examples, but the layered silicate lump, powder, and method for producing the layered silicate are not limited to the following examples.

[0066] [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 using carbon electrodes in an internally heated melting furnace and held at that temperature for 10 minutes to melt the raw material mixture. The melt was removed from the furnace, placed in an iron mold equipped with a water-cooling jacket, and rapidly cooled to 900°C at a cooling rate of 203°C / min. The mixture 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 resulting lump was measured.

[0067] [Test Example 2] Except for the cooling rate, ore lumps were 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 lumps was measured.

[0068] [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 melt 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.

[0069] [Test Example 4] 100 kg of molten raw materials containing the chemical composition of sodium tetrasilicic mica were 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 melt was removed from the furnace, placed in an iron mold, and cooled to 900°C at a cooling rate of 36°C / min. The mixture was then cooled to room temperature and crystallized to obtain an ore lump. The cristobalite content of the resulting ore lump was measured.

[0070] [Measurement of cristobalite content] The amount of cristobalite produced in each test example was measured using an internal standard method based on X-ray diffraction. Alumina was used as the internal standard. A calibration curve was prepared in advance to identify the amount of cristobalite produced. X-ray diffraction patterns were measured for mixtures of 20% alumina by mass, cristobalite, and calcium fluoride (remainder, diluted material), with cristobalite percentages of 1%, 10%, 25%, and 50% by mass. For each X-ray diffraction chart, the integrated intensity I2 of the alumina peak (Miller index (hkl): 012) near 2θ = 25.6° and the integrated intensity I1 of the cristobalite peak (Miller index (hkl): 102) near 2θ = 31.4° were read. A calibration curve was then prepared by plotting the integrated intensity I1 of the cristobalite peak / integrated intensity I2 of the alumina peak against the cristobalite content. The slope a of the prepared calibration curve was measured. The slope a of the calibration curve was 0.0462.

[0071] Next, the X-ray diffraction patterns of the ore lump obtained in each test example were measured. First, the ore lump obtained in each test example was powdered and dried. Next, 0.800±0.001 g of each powder 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 an X-ray diffractometer (MiniFlex600-C, manufactured by Rigaku Corporation) with Cu-Kα radiation. In each X-ray diffraction chart, the integrated intensity I1 (cps) of the cristobalite peak (Miller index (hkl): 102) near 2θ = 31.4° and the integrated intensity I2 (cps) of the alumina peak (Miller index (hkl): 012) near 2θ = 25.6° were read. The cristobalite content X contained in the synthetic mica produced in each test example was calculated using the following formula. Table 1 shows the measurement results of the cristobalite content. 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.

[0072] X(mass%)=(I1 / I2) / 0.0462=I1 / (I2×0.0462)

[0073] Figure 1 shows a comparison of the X-ray diffraction patterns of the products in Test Examples 1 and 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.

[0074] [Table 1]

[0075] As shown in Figures 1 and 2, in Test Examples 1 to 3, in which the cooling rate was 100°C / min or more, no cristobalite was 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 ore mass. This shows that by setting the cooling rate of the raw material melt to 100°C / min or more, it is possible to suppress the generation of cristobalite as a by-product.

[0076] [Test Example 5] Five grams 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 that, the slurry was classified using 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.

[0077] Even when the lump was pulverized and changed 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.

[0078] [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 using the following formula, measuring the half-width of the peak at approximately 2θ=61° derived from the (060) plane by X-ray diffraction. CuKα rays were used for X-rays, with λ=0.154 nm. K was set to 0.89. The crystallite size was the average value of three X-ray diffraction measurements. The measurement results are shown in Table 2.

[0079] D=Kλ / (Bcosθ) D: crystallite size (nm), K: Scherrer constant, λ: X-ray wavelength (nm), B: half-width (rad), θ: Bragg angle (rad)

[0080] [Table 2]

[0081] The synthetic mica powders of Test Examples 6-1 to 6-3, which were produced in Test Examples 1 to 3, had smaller crystallite sizes than the synthetic mica powder of Test Example 6-4, which was produced in Test Example 4. The synthetic mica of Test Examples 6-1 to 6-3 were crystallized by rapid cooling, which is thought to be why the crystallites were smaller. It is thought that the smaller crystallite size allows the particles of the swellable synthetic layered silicate to be made thinner.

[0082] [Test Example 7: Friction Test] The effect of the cristobalite content in the swellable synthetic layered silicate on the frictional sensation when applied was tested. In the friction test, the mean coefficient of friction (MIU) and mean deviation of the coefficient of friction (MMD) were measured. MIU represents the slipperiness felt by the applicator when applying the swellable synthetic layered silicate powder. The smaller the MIU value, the more slipperiness the applicator feels. The MIU value is preferably less than 0.8. MMD represents the smoothness or roughness felt by the applicator when applying the swellable synthetic layered silicate powder. The smaller the MMD value, the more slipperiness the applicator feels.

[0083] For the friction test, synthetic mica lump produced in Test Example 1, which had a cristobalite content below the detection limit (less than 0.1% by mass), and synthetic mica lump produced in Test Example 4, which contained 9.6% by mass of cristobalite, were milled in a Raymond mill. The lump in Test Examples 1 and 4 was milled to the same degree using 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. The friction test was performed using a friction feel tester KES-KS (manufactured by Kato Tech Co., Ltd.) with a silicon sensor. 0.01 g of powder was uniformly applied to artificial leather and the test was conducted. Three measurements were performed on each powder in each test example, and the average value was calculated. The MIU measurement results are shown in Table 3. The MMD measurement results are shown in Table 4. The measurement conditions were as follows: SENS:H Frictional static load: 25gf Measurement distance: 20mm Measurement speed: 1mm / sec Sensor: 10mm square sensor Temperature: 20.5℃±2℃ Humidity: 60%±2℃

[0084] [Table 3]

[0085] [Table 4]

[0086] The MIU of Test Examples 7-1 and 7-2 was less than 0.8, and both were slippery powders. Furthermore, 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), while the particle shape of cristobalite is not flat. Therefore, the powder obtained from Test Example 1 is thought to be smoother and less rough because it is free of foreign matter. This demonstrates that the powder of the present disclosure is suitable for application to the skin.

[0087] Furthermore, the powder of Test Example 7-3 had a smaller MMD value, which means that when the powder is applied to a film, it has less unevenness and is more likely to be uniformly and densely aligned. From this, as shown in Test Example 8 below, it was found that the powder of the present disclosure is also suitable for improving gas barrier properties.

[0088] [Test Example 8: Gas Barrier Test] The gas barrier performance (water vapor permeability) of films coated with 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, was tested.

[0089] The gas barrier test was carried out 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 the same extent. The ore lump in Test Examples 1 and 4 was pulverized to the same extent by the same method.

[0090] The synthetic mica powder of each test example was dispersed in water to prepare a slurry. A polyurethane water-soluble resin (Takelac® WPB-341 (Mitsui Chemicals MC)) was added to the slurry and mixed so that the total mass of the powder and water-soluble resin was 15% by mass relative to the total mass of the slurry, to prepare a coating solution. Coating solutions with different synthetic mica powder contents (no additives, 0%, 10%, and 20% by mass relative to the total mass of the water-soluble resin and powder) were prepared. The coating solution was then applied to a 12-μm-thick polyethylene terephthalate film (PET film) to a thickness of 10 μm before drying and dried in a dryer. A test cup containing the resulting film and 7 g of calcium chloride as a moisture absorbent was placed in a thermo-hygrostat chamber adjusted to a temperature of 40°C and a humidity of 90% RH for 24 hours. The water vapor transmission rate (WVTR) was calculated using the following equation. The water vapor transmission rate was calculated using the following equation. Table 5 shows the measurement results (g / (m2·day)).

[0091] 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 )

[0092] [Table 5]

[0093] 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 with a low amount of cristobalite had higher gas barrier performance than films coated with synthetic mica with a high amount of cristobalite. It is thought that the lower amount of cristobalite impurity reduces the gap between the powder and the PET film, improving gas barrier performance. It is also thought that the thinner powder particles contribute to improved gas barrier performance.

[0094] [Test Example 9: Cristobalite removal test by alkali treatment] An attempt was made to remove cristobalite from the synthetic mica powder prepared in Test Example 4 above by alkali treatment. 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 the mixture was heated at 95°C to 98°C for 5 hours. After the heat treatment, the treated product was dried and pulverized into powder. The cristobalite content 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 were prepared by alkali treatment of synthetic mica from the same production lot as Test Example 9-1. The reduction rates shown in Table 6 are the rate of change relative to the cristobalite content of Test Example 9-1.

[0095] [Table 6]

[0096] In both alkali treatments, most of the cristobalite remained. It was found that it is difficult to reduce the cristobalite content to 1 mass% or less using alkali treatment.

[0097] [Test Example 10: Cristobalite removal test by heat treatment] An attempt was made to remove cristobalite from synthetic mica powder prepared from the lump prepared in Test Example 4 above by heat treatment. 20 g of powder was heat treated at 450°C, 650°C, and 850°C. The heat treatment conditions, cristobalite content, and rate of change are shown in Table 7. Test Examples 10-2 to 10-4 were obtained by heat treating synthetic mica from 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 cristobalite content of Test Example 10-1.

[0098] [Table 7]

[0099] Heat treatment of the powder tended to reduce the amount of cristobalite. However, most of the cristobalite remained in all heat treatments. It was found that it is difficult to reduce the cristobalite content to 1% by mass or less through heat treatment.

[0100] [Test Example 11: Cristobalite removal test by classification] An attempt was made to remove cristobalite from the synthetic mica powder prepared in Test Example 4 above by classification. The classification was performed by dispersing the swellable synthetic layered silicate in water and then centrifuging. Compared to before classification, the synthetic mica was reduced by approximately 30% by mass, but the cristobalite content remained unchanged. This indicated that it was difficult to remove cristobalite by classification.

[0101] The swellable synthetic layered silicate, powder, and method for producing the same 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 can 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, and selections of each disclosed element are possible within the scope of the claims of the present invention.

[0102] Further objects, purposes and modes (including modifications) of the present invention will become apparent from the entire disclosure of the present invention including the claims.

[0103] With respect to numerical ranges set forth herein, unless otherwise specified, any numerical value or range falling within that range should be construed as being specifically set forth herein. [Industrial Applicability]

[0104] The swellable synthetic layered silicate, powder, mixed powder, and their manufacturing methods of the present disclosure 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 and the like, flame retardant materials, chemical resistant materials, ion adsorbents, gasket materials, lubricants, conductive materials, laser marking materials, thermal recording materials, dispersants, drawing materials, dispersants, and the like.

Claims

1. a heating step of heating and melting a mixture of raw materials for synthesizing a swellable layered silicate; a cooling step in which the melt melted in the heating step is cooled to at least 900°C at a cooling rate of 100°C / min or more to produce a lump of the swellable layered silicate; Including, A method for producing a swellable layered silicate, wherein the swellable layered silicate is sodium tetrasilicic mica.

2. 2. The method for producing an expandable layered silicate according to claim 1, wherein the content of cristobalite in the lump is 1 mass % or less relative to the mass of the lump.

3. 3. The method for producing the swellable layered silicate according to claim 1, further comprising a grinding step of wet or dry grinding the ore mass to produce a powder of the swellable layered silicate.

4. The method for producing the swellable layered silicate according to any one of claims 1 to 3, which does not include a removal step for removing cristobalite contained in the ore mass.

5. The method for producing a swellable layered silicate according to any one of claims 1 to 4, wherein one lump weighs 10 g or more.

6. 2×10 cristobalite per 1 part by mass of the swellable layered silicate powder －３ The method for producing the swellable layered silicate according to any one of claims 3 to 5, wherein the amount of the swellable layered silicate is not more than parts by mass.

7. 7. The method for producing a swellable layered silicate according to claim 3, wherein the powder of the swellable layered silicate has an average particle size of 5 μm to 30 μm.

8. The method for producing a swellable layered silicate according to any one of claims 3 to 7, wherein the powder of the swellable layered silicate has an average crystallite size of 14 nm to 18 nm as determined from the X-ray diffraction peak of the (060) plane.

9. 1. A method for reducing cristobalite in a swellable layered silicate ore mass, comprising: a heating step of heating and melting a mixture of raw materials for synthesizing a swellable layered silicate; a cooling step in which the melt melted in the heating step is cooled to at least 900°C at a cooling rate of 100°C / min or more to produce a lump of the swellable layered silicate; Including, A method for reducing cristobalite, characterized in that the swellable layered silicate is sodium tetrasilicic mica.

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