JP2010173870A - 2:1 type 3 octahedral synthetic clay, transparent clay gel, coating clay film and self-supporting clay film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a 2:1 type 3 octahedral synthetic clay capable of obtaining a coating clay film and a self-supporting clay film which have high transparency and high water resistance, and a coating clay film and a self-supporting clay film which have high transparency and high water resistance. <P>SOLUTION: The 2:1 type 3 octahedral synthetic clay contains stevensite which contains Li, Mg and Si in the ranges of Li/Si=0.08-0.17 and Mg/Si=0.65-0.72. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to 2: 1 type 3 octahedral synthetic clay, transparent clay gel, coating clay film and self-supporting clay film.

  In order to improve the low heat resistance of the polymer (for example, about 350 ° C. with an imide resin having the highest heat resistance) and low gas barrier properties, polymer clay nanocomposites using clay as an additive have been studied ( For example, see Patent Documents 1 and 2). These polymer clay nanocomposites are improved in performance such as heat resistance and gas barrier property as the clay content increases. However, since clay is inferior in moldability, the blending ratio of clay in the polymer clay nanocomposite is limited to ensure moldability.

On the other hand, in recent years, clay films having performance exceeding the heat resistance and gas barrier properties of polymer clay nanocomposites have been developed (see, for example, Patent Documents 3 and 4). Patent Document 3 contains 90 to 100% by mass of clay with respect to the total solid content of the clay film, has mechanical strength that can be used as a self-supporting film, and has excellent flexibility even at a high temperature of 350 ° C or higher. A clay film that achieves high heat resistance (maximum 600 ° C.) and gas barrier properties (gas permeability coefficient: less than 3.2 × 10 ⁻¹¹ cm ² s ⁻¹ cmHg ⁻¹ ) is disclosed (see Patent Document 3). Further, Patent Document 4, a high gas barrier property at a content of clay 70 mass% or more (gas permeability coefficient: 3.2 × ¹⁰ -11 ^cm 2 ^s less than -1 cmHg ^-1) have, 200 ° C. or higher Disclosed is a clay film that is chemically stable even at high temperatures in excess of the above, has transparency (total transmittance of 80% or more), and is flexible. These clay films are expected to be used as display materials, packaging materials, electronic device sealing materials, and the like.

  The above-mentioned clay-based film (clay film) uses smectite as clay. It is known that smectite swells in water to form a uniform clay dispersion, and the clay dispersion is applied and dried to form a film in which clay layers are uniformly laminated (see Non-Patent Document 1). ). The clay film can be formed even when the clay film contains a large amount of clay by using smectite having a high film forming property even with clay alone.

  The swelling property of smectite with respect to a dispersion medium such as water is an important property for forming a clay film. However, on the other hand, high dispersibility and swellability in water and the like cause a decrease in water resistance of the formed clay film. Therefore, as the content of smectite in the clay film is increased, the water vapor barrier property of the clay film is lowered and there is a problem that it is dispersed again in water.

  As one method for solving this problem, a clay film using a modified clay has been reported (see Patent Document 5). The modified clay contains less than 30% by mass of organic cations, and at least 50% of the exchangeable cations of the clay are lithium ions. In the clay film using the modified clay, the lithium between layers moves into the octahedral layer of the clay by heat treatment, and the water resistance is improved by reducing the ionic components between the layers. This improvement in water resistance becomes significant when the lithium ion content of the interlayer ionic substance is 50% or more.

  As described above, the improvement in water resistance due to the migration of lithium ions into the octahedral layer of the clay is that the main source of charge is the octahedral layer, for example, there are voids in the octahedral layer, such as montmorillonite. It is reported that the behavior is unique to a certain dioctahedral clay (see Non-Patent Documents 2 and 3). However, dioctahedral clay is difficult to synthesize and not industrialized, and natural clay is mainly used for industrial applications. Natural clay is unavoidably mixed with impurities, and a transparent clay gel or clay film cannot be obtained.

  On the other hand, trioctahedral clay is relatively mild compared to dioctahedral clay, such as a low synthesis temperature. Therefore, a highly pure trioctahedral can obtain a transparent clay gel or clay film. Clay is also industrially synthesized and is commercially available. Therefore, in the case of trioctahedral clay, if water resistance can be improved on the same principle as that of dioctahedral clay, a transparent and water-resistant clay gel or clay film can be produced.

  Stevensite, one of the three octahedral clays, is a clay in which part of the octahedral magnesium is missing. Therefore, since the charge generation source is the octahedral layer and there are voids in the octahedral layer, it is considered that the improvement in water resistance can be expected from the principle reported for the dioctahedron.

  The phenomenon in which the above smectite swells with water or the like is a phenomenon that occurs when water enters between layers of clay. The degree of swelling varies depending on the type of interlayer ions, but as long as there are cations between the layers, moisture absorption will inevitably occur. In particular, sodium ions have a very high water adsorbing power, so that water can easily enter between layers and cause infinite swelling to moisture. However, sodium ions, together with calcium ions, are surface ions of natural smectite interlayer ions, and are always contained in natural clay. In addition, even in synthetic clay, there have been few reported cases of smectite containing no sodium.

  As described above, one of the reasons why the development of synthetic clay not containing sodium has not been carried out is that clay has not been used in industrial fields where sodium content becomes a problem. In addition, since sodium serves as an accelerator for clay formation in the synthesis, it is difficult to synthesize clay (particularly, stevensite) without sodium (see Non-Patent Document 4).

  In the case of using clay as a coating liquid for forming a film and a surface coating agent for a metal material, sodium ions cause corrosion of the substrate material and peeling of the coating film. Therefore, synthesis of lithium-type hectorite has been reported as a clay synthesis method with reduced sodium ion content (Patent Document 7), and the sodium content is 0.5 wt% or less (compared to commercially available hectorite). Synthetic clays are disclosed in amounts of about 10%). However, since this method uses a sodium silicate aqueous solution as a raw material for the silica sol, it is difficult to completely eliminate sodium, although it is unavoidable to contain sodium, although in a small amount.

  Another method for obtaining lithium smectite having a reduced sodium content is an ion exchange method. There are several methods for ion exchange of clay, but the most commonly used method is to disperse sodium-type or calcium-type clay in a solution containing lithium ions, and interlaminate ions of clay and This is a method of exchanging ions. Clay is dispersed in a solution in which lithium ion chloride (eg, lithium chloride, lithium nitrate, lithium sulfate, etc.) is dissolved, and then filtered. This operation is repeated several times to exchange interlayer ions. After the replacement, repeat the water or alcohol washing to remove the salt adhering as impurities. Although this ion exchange method using a chloride solution is very time-consuming, complete ion exchange cannot be performed. In addition, the influence of chloride impurities that cannot be washed remains, and the clay is also washed away during washing, so that there is a problem that the yield of clay decreases drastically as the degree of ion exchange increases and the purity increases. Although an ion exchange method using an ion exchange resin has also been reported (Patent Document 6), about 15% of interlayer sodium ions cannot be exchanged and remain in the clay.

US Pat. No. 4,733,007 JP-A-51-7056 JP 2006-77237 A JP 2007-63118 A JP 2007-277078 A JP 2007-302897 A Japanese Patent Laid-Open No. 9-249412

Cray Science 13 (2007) 159 Abstracts of Lecture Meeting 31 (1987) 67 Abstracts 44 Annual Meeting of the Japan Society for Clay Science Discussion (2000) 238 Journal of mineralogy 14 (1979) 170

  An object of the present invention is to provide a 2: 1 type 3 octahedral synthetic clay capable of obtaining a coating clay film and a self-supporting clay film having high transparency and high water resistance. Another object of the present invention is to provide a coating clay film and a self-supporting clay film having high transparency and high water resistance.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by including a stevensite having a specific composition.

That is, the present invention is characterized by the following items (1) to (14).
(1) 2: 1 type 3-octahedron synthetic clay containing Li, Mg and Si, and containing stevensite in the range of Li / Si = 0.08 to 0.17 and Mg / Si = 0.65 to 0.72. .
(2) The 2: 1 type 3 octahedral synthetic clay according to (1), which does not contain Na.
(3) The 2: 1 type 3 octahedral synthetic clay according to (1) or (2), wherein the water absorption after heat treatment at 500 ° C. is less than 5%.
(4) The 2: 1 type 3 octahedral synthetic clay according to any one of (1) to (3), wherein Li as an impurity is Li / Si <0.15.
(5) A transparent clay gel having thixotropic properties, comprising 2: 1 type 3 octahedral synthetic clay according to any one of (1) to (4) above and water as a dispersion medium.
(6) A coated clay film formed using the transparent clay gel described in (5) above.
(7) The coated clay film according to (5), wherein the transparency is 90% or more of the total light transmittance.
(8) The coated clay film according to (6) or (7), wherein the total light transmittance after heat treatment at 400 ° C. or lower is 70% or more.
(9) The coated clay film according to any one of (6) to (8), wherein water resistance is improved by heat treatment.
(10) A self-supporting clay film using the transparent clay gel described in (5) above.
(11) The self-supporting clay film according to (10), wherein the transparency is 80% or more of the total light transmittance.
(12) The self-supporting clay film according to (10) or (11) having a thickness of 30 to 500 μm.
(13) The self-supporting clay film according to any one of (10) to (12), wherein the total light transmittance after the heat treatment at 400 ° C. or lower is 70% or more.
(14) The self-supporting clay film according to any one of (10) to (13), wherein water resistance is improved by heat treatment.

  According to the present invention, it is possible to obtain a 2: 1 type 3 octahedral synthetic clay that can obtain a coating clay film and a self-supporting clay film having high transparency and high water resistance. In addition, the present invention makes it possible to obtain a coated clay film and a self-supporting clay film having high transparency and high water resistance.

2 is an XRD pattern of the clay obtained in Example 1. (A) It is a XRD pattern of the clay obtained in Example 7. (B) It is a XRD pattern of the clay obtained in Example 8. (C) It is a XRD pattern of the clay obtained in Example 9. 2 is a photograph of a self-supporting clay film obtained in Example 1. 2 is a SEM photograph of the end face of the self-supporting clay film obtained in Example 1. FIG. 3 is a photograph after the self-supporting clay film obtained in Example 1 was heat-treated at 400 ° C. for 3 hours, then placed in water and left overnight.

  Hereinafter, the present invention will be described in detail.

  The 2: 1 type 3 octahedral synthetic clay of the present invention contains Li, Mg, and Si, and has a range of Li / Si = 0.08 to 0.17 and Mg / Si = 0.65 to 0.72. It is characterized by including. The value of Li / Si is preferably 0.10 to 0.17 from the viewpoint of high crystallinity and a higher quality clay.

The 2: 1 type 3 octahedron synthetic clay of the present invention contains Li, Mg and Si, and a pair of tetrahedron layers (tetrahedron sheets) having Si are arranged with their apexes facing each other, and the pair of tetrahedra An octahedral layer (octahedron sheet) having Mg is positioned so as to be sandwiched between layers, and Li is arranged as an interlayer cation.

In the present invention, Li / Si and Mg / Si indicate values calculated by the following method.
Li / Si was calculated by measuring interlayer ions or Li contained in the layer with respect to the amount of Si contained in the synthetic raw material. The amount of Li as interlayer ions was converted by measuring the amount of methylene blue exchanged with Li between layers using the methylene blue adsorption method. On the other hand, the amount of Li entering the layer was calculated from the difference between the amount of Li added to the synthetic raw material and the amount of Li detected by ICP measurement. Mg / Si was measured using EDX elemental analysis.

  The 2: 1 type 3 octahedral synthetic clay of the present invention is characterized by not containing Na. When it does not contain Na, it means that Na is not detected even at the detection limit value when interlayer ions of the obtained clay are measured by ICP, and it is not intended that Na is detected with a measurement error. Since the 2: 1 type 3 octahedral synthetic clay does not contain Na, almost all cations (interlayer cations) existing between the layers become lithium ions. Water resistance is improved by moving into the face layer and reducing the interlayer cation component. The 2: 1 type 3 octahedral synthetic clay of the present invention is improved in water resistance, for example, by heating at 500 ° C. for 12 hours. Specifically, the clay before the heat treatment was measured by the same method as the moisture absorption rate when left for 5 hours in a constant temperature and high humidity chamber set at a temperature of 40 ° C. and a humidity of 90%. When the moisture absorption rate of the clay subjected to the heat treatment at 500 ° C. for 12 hours is compared, the moisture absorption rate of the clay after the heat treatment is reduced by 95% or more as compared with the moisture absorption rate of the clay before the heat treatment.

  The heating temperature for improving water resistance is preferably 350 to 500 ° C. Since lithium ions have a small ion radius, the lithium ions move into the octahedral layer of clay by the heat treatment and are fixed. This reaction is an irreversible reaction, and once the lithium ions move into the layer, they do not return to the clay layer again. This lowers the layer charge of the clay and makes it difficult to swell in water (improves water resistance). On the other hand, since sodium ions have a large radius, they cannot move into the octahedral layer even if heat treatment is performed, and the above-described clay layer charge change does not occur. Thus, since the synthetic clay of the present invention does not contain sodium ions between the layers, and almost only lithium ions exist, almost all lithium ions move into the octahedral layer by heat treatment, and thus have high water resistance. It is thought that clay is obtained.

In addition, the 2: 1 type 3 octahedral synthetic clay of the present invention may contain Li / Si <0.15 as an impurity, not as a constituent element of the clay. In general, trioctahedral clay is synthesized by blending raw materials according to the required theoretical composition ratio of clay. However, in an example of the method for synthesizing the 2: 1 type 3 octahedral synthetic clay of the present invention, which will be described later, even if the raw materials are blended according to the theoretical composition ratio, the clay having the theoretical composition may not be synthesized. This is presumably because the example of the method for synthesizing 2: 1 type 3 octahedral synthetic clay of the present invention uses a sodium-free raw material that functions as an accelerator for clay synthesis. In an example of the method for synthesizing the 2: 1 type 3 octahedral synthetic clay of the present invention, it is preferable to make the amount of lithium ions as interlayer ions excessive from the theoretical composition ratio. In an environment where lithium ions are excessive, it is considered that 2: 1 type 3 octahedral clay containing stevensite can be synthesized without sodium.
In the synthesis of lithium ions under an excessive condition, lithium existing excessively after the synthesis is not formed as a constituent element of clay but is generated in the form of a salt. This lithium salt may be removed after the synthesis, for example, by washing, but if it is within the above range (Li / Si <0.15) without washing, the effect of the present invention is greatly affected. Not give. On the other hand, if the lithium salt contained as an impurity is 0.15 or more in terms of Li / Si, crystallization of the clay may be hindered during clay synthesis.
In addition, Li / Si as an impurity in the present invention indicates a value calculated by the following method. The amount of Li as an impurity is a value obtained by subtracting the amount of Li as interlayer ions and the amount of Li contained in the layer from the amount of added Li. The amount of Li as interlayer ions was converted by measuring the amount of methylene blue exchanged with Li between layers using the methylene blue adsorption method. The amount of Li entering the layer was calculated from the difference between the amount of Li added to the synthesis material and the amount of Li detected by ICP measurement. Li / Si was calculated from the ratio of the amount of Si put into the synthetic raw material and the amount of Li as an impurity.

  The 2: 1 type 3 octahedral synthetic clay of the present invention can be easily dispersed, for example, by mixing with water as a dispersion medium to form a transparent clay gel having thixotropic properties. This is due to having monovalent lithium ions as interlayer ions.

  By applying the clay gel on a substrate and allowing it to stand and dry, it is possible to form a coated clay film with uniform particle orientation. There are no particular restrictions on the substrate on which the coated clay film can be formed. For example, glass such as borosilicate glass, Pyrex (registered trademark), and quartz, metals such as stainless steel, aluminum, iron, and copper, alumina, and zirconia And ceramics such as titania, plastics such as polypropylene (PP), polyethylene terephthalate (PET), and naflon (PTEF).

  Further, the coating clay film of the present invention preferably has a transparency of 90% or more in terms of total light transmittance, and more preferably has a total light transmittance of 70% or more after the heat treatment at 400 ° C. or less. preferable.

  The total light transmittance of the coating clay film can be measured with a turbidimeter (haze meter).

  In addition, the transparent clay gel of the present invention can be applied on a substrate and dried to form a transparent film. For example, when applied to a substrate made of polypropylene and dried, The substrate and the formed film can be easily separated, and a self-supporting clay film can be produced. The self-supporting clay film of the present invention preferably has a strength capable of being handled even when separated from the substrate. The thickness (film thickness) of the self-supporting clay film of the present invention can be adjusted as appropriate depending on the concentration of the clay gel applied to the substrate for the time being, the thickness of the transparent clay gel, and the like. In view of handling strength, transparency, etc., a self-supporting clay film of 30 to 150 μm is preferable.

  The self-supporting clay film of the present invention preferably has a transparency of 80% or more in terms of total light transmittance, and after heat treatment at 400 ° C. or less, the self-supporting clay film has a total light transmittance of 70% or more. More preferred.

  It is preferable that the coated clay film and the self-supporting clay film of the present invention have improved water resistance, like the 2: 1 type 3 octahedral synthetic clay.

  Next, an example of a method for synthesizing the 2: 1 type 3 octahedral synthetic clay of the present invention will be described. The 2: 1 type 3 octahedral synthetic clay of the present invention can be synthesized by a hydrothermal method. Hereinafter, each process of the hydrothermal method will be described in detail.

(First step)
An aqueous solution containing a silicon compound as a silica source of clay and a magnesium compound as a magnesium source is prepared. The aqueous solution can be adjusted, for example, by mixing an aqueous solution containing each compound at room temperature (15 to 25 ° C.).

  Examples of the aqueous solution containing a silicon compound include an aqueous solution containing non-crystalline silica, such as colloidal silica, amorphous silica, ethyl silicate, silicon dioxide, and the like. These may be used alone or in combination of two or more. In general, water glass is a silica source, but since water glass contains about 9 to 10% of sodium oxide, the effect of the present invention tends not to be obtained, which is not preferable. In the synthesis of the clay of the present invention, it is preferable to use a material containing no sodium from the raw material stage. When adjusting the aqueous solution containing a silicon compound, the pH is preferably 5 or less, and may be adjusted with a mineral acid such as nitric acid, hydrochloric acid, or sulfuric acid, if necessary.

  Moreover, as an aqueous solution containing a magnesium compound, the aqueous solution containing magnesium chloride, magnesium sulfate, magnesium nitrate etc. is mentioned, for example. These may be used alone or in combination of two or more.

  Next, an aqueous alkaline solution is dropped into an aqueous solution containing a silicon compound and a magnesium compound at room temperature (15 to 25 ° C.) to obtain a dispersion containing a homogeneous composite precipitate.

  Examples of the alkaline aqueous solution include ammonia water and a lithium hydroxide aqueous solution. However, since the lithium hydroxide aqueous solution contains lithium ions, it may affect the amount of clay interlayer ions. It is preferable to use water.

  It is preferable that the alkaline aqueous solution is dripped by slowly mixing the alkaline aqueous solution while stirring to make the entire solution uniform. Moreover, it is preferable to perform dripping of aqueous alkali solution until pH becomes 10 or more. After completion of the dropwise addition, if necessary, it is allowed to stand for several hours to make the formation of a homogeneous composite precipitate sufficient.

The obtained homogeneous composite precipitate is preferably sufficiently washed with water to sufficiently remove by-product electrolytes such as NH ₄ ⁺ , NO ₃ ⁻ and Cl ⁻ . For example, aqueous ammonia is used as an alkaline aqueous solution. If so, it is preferable to repeat the water washing until the ammonia odor disappears. In the water washing, distilled water is added to the homogeneous composite precipitate, followed by shaking and solid-liquid separation. The homogeneous composite precipitate after washing can be mixed with water to form a dispersion used in the next step.

(Second step)
An aqueous solution containing a lithium compound as a lithium ion source is mixed with the dispersion of the homogeneous composite precipitate obtained in the first step to obtain a starting raw material slurry.

  Examples of the aqueous solution of the lithium compound include an aqueous solution containing lithium hydroxide, lithium hydroxide monohydrate, lithium hydride, lithium peroxide and the like. These may be used alone or in combination of two or more. The amount of addition of the lithium compound is preferably such that Li in the lithium compound is (0.45 to 1.20) when Si in the silicon compound used as the silica source is 4. If it is in the said range, there exists a tendency for the target clay to be obtained easily, without wash | cleaning in the 3rd process mentioned later.

(Third step)
In the third step, the hydrothermal reaction of the starting material slurry obtained in the second step is performed. In this step, the starting material slurry is charged into an autoclave and subjected to a hydrothermal reaction. The temperature of the hydrothermal reaction is preferably 100 to 300 ° C. The hydrothermal reaction time is preferably 24 hours or longer. Before charging the starting material slurry into the autoclave and after completion of the hydrothermal reaction, the lithium salt contained as an impurity in the starting material slurry can be washed as necessary.

(Fourth process)
After the hydrothermal reaction in the third step, the content in the autoclave is taken out, dried at a temperature of 15 to 150 ° C., and appropriately pulverized, whereby the 2: 1 type 3 octahedral synthetic clay of the present invention can be obtained. .

  The obtained clay can be confirmed to be trioctahedral clay containing stevensite by measuring EDX, ICP, XRD and the like.

  Specifically, the ratio of Si and Mg or the impurity component of clay can be confirmed by EDX.

  The type and amount of interlayer ions or the amount of Li ions in the interlayer / layer can be confirmed by ICP.

  By XRD, the type, orientation, crystallinity, and crystal impurities of the clay can be confirmed.

  As described above, the 2: 1 type 3 octahedral synthetic clay obtained by the above synthesis method can be mixed with a dispersion medium such as water to produce a transparent clay gel having thixotropy. Moreover, a coating clay film can be obtained by applying the transparent clay gel to a substrate and drying, and a self-supporting clay film can be obtained by peeling off from the substrate. The coated clay film and the self-supporting clay film of the present invention have high transparency and excellent water resistance.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

Example 1
20 ml of nitric acid was added to a dispersion obtained by mixing 60 g of colloidal silica (Ludox ™ 50, manufactured by SigmaAldrich) and 120 ml of distilled water. A solution prepared by mixing 91 g of magnesium nitrate (primary reagent) and 128 ml of distilled water was added thereto, and ammonia water (28% aqueous solution) was slowly added dropwise with stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 25.4 ml of a 10 wt% lithium hydroxide aqueous solution was added to the well-mixed homogeneous composite precipitation dispersion and mixed well to obtain a starting raw material slurry. The starting material slurry was charged into an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized to obtain 2: 1 type 3 octahedral synthetic clay. The following various evaluations were performed using the obtained clay.
[Confirmation of 2: 1 type 3 octahedral synthetic clay]
It was confirmed from the XRD pattern (Bruker / MacScience M21X) whether the target clay was produced. The obtained clay aqueous dispersion (2.5 wt%) was dropped on a glass substrate and dried to measure the XRD pattern of the clay film. When the target clay is obtained, a smectite pattern in which a d (001) peak as shown in FIG. 1 appears in the vicinity of 2θ = 6 ° C. is shown. Whether or not the target clay was obtained was determined based on the presence or absence of the d (001) peak. The results are shown in Table 1.
[Calculation of Li / Si and Mg / Si]
Li / Si and Mg / Si were calculated by the following method.
Li / Si was calculated by measuring interlayer ions or Li contained in the layer with respect to the amount of Si contained in the synthetic raw material.
The amount of Li as interlayer ions was converted by measuring the amount of methylene blue exchanged with Li between layers using the methylene blue adsorption method. Specifically, the obtained clay was dried at 110 ° C. for 1 hour, 0.02 g was weighed, added to 30 ml of a methylene blue aqueous solution having a concentration of 1.5 × 10 ⁻⁶ mol / ml, and stirred at room temperature for 3 days. Left alone. Thereafter, the clay and the solution were separated using a filter having a pore diameter of 0.45 μm. After diluting 3 ml of distilled water to 0.1 ml of the separated solution, the methylene blue concentration of the diluted solution was measured. The concentration was measured using a spectrophotometer (MPS-2450, manufactured by Shimadzu Corporation) at a wavelength of 665 nm, and the amount of methylene blue adsorbed per 100 g of clay was calculated. The amount of methylene blue adsorption calculated here was the amount of Li existing as interlayer ions.
On the other hand, the amount of Li entering the layer was calculated from the difference between the amount of Li added to the synthetic raw material and the amount of Li detected by ICP measurement. Specifically, 0.1 mg of the obtained clay was put into 10 ml of an ammonium acetate solution (1N) and shaken at 100 rpm overnight. Thereafter, the supernatant was passed through a filter having a pore diameter of 0.45 μm, and ICP analysis (ICP emission analyzer (SPS-1500R manufactured by Seiko Electronics Co., Ltd.)) was performed.
Mg / Si was measured using EDX elemental analysis (S-800, manufactured by Hitachi, Ltd.).
The results are shown in Table 1.
[Calculation of Li / Si as an impurity]
Li / Si was calculated by the following method.
The amount of Li as an impurity is a value obtained by subtracting the amount of Li as interlayer ions and the amount of Li contained in the layer from the amount of added Li. The amount of Li as interlayer ions was converted by measuring the amount of methylene blue exchanged with interlayer Li using the methylene blue adsorption method as described above. The amount of Li entering the layer was calculated from the difference between the amount of Li added to the synthesis raw material and the amount of Li detected by ICP measurement in the same manner as described above. Li / Si was calculated from the ratio of the amount of Si put into the synthetic raw material and the amount of Li as an impurity. The results are shown in Table 1.
[Na content]
The amount of sodium ions contained in the clay was measured. 0.1 mg of the clay obtained was put into an ammonium acetate solution (1N) and shaken at 100 rpm overnight. Thereafter, the supernatant was passed through a filter (pore size: 0.45 μm), and then ICP analysis (ICP emission spectroscopic analyzer (manufactured by Seiko Denshi Co., Ltd./SPS-1500R) was performed. The results are shown in Table 1. Detection of the above device When the value was less than the limit value, it was described as ND.
[Water dispersibility (preparation of transparent clay gel)]
The obtained clay was dispersed in distilled water to obtain a 2.5 wt% transparent clay gel. The water dispersibility was judged as ◯ when it was well dispersed in water and confirmed to have thixotropic properties, and as x when the formation of precipitates was confirmed after dispersion. The results are shown in Table 1.
[Filmability (Preparation of self-supporting clay film)]
The transparent clay gel obtained by the water dispersibility evaluation was poured into a polypropylene container and naturally dried at room temperature. The dried clay film was physically peeled from the container to obtain a self-supporting clay film. The photograph of the obtained self-supporting clay film is shown in FIG. 3, and the SEM photograph of the end face of the self-supporting clay film is shown in FIG. The SEM photograph used was HITACHI / S-800. Evaluation of film formability was made visually according to the following criteria. The results are shown in Table 1.

Self-supporting clay film that can be handled: ○
Although the film is formed, the shrinkage is large and the lump state is: Δ
Powder state without film formation: ×
[Transparency]
Transparency was measured using the self-supporting clay film obtained by the evaluation of the film forming property. The transparency was evaluated by measuring the total light transmittance with a turbidimeter (Nippon Denshoku Industries Co., Ltd./NDH5000). Moreover, the same evaluation was performed using the coating clay film obtained by apply | coating the transparent clay film obtained by water dispersibility evaluation on a slide glass, and drying. The results are shown in Table 1.
[Water resistance (solubility in water)]
The water resistance was evaluated using the self-supporting clay film obtained by the evaluation of the film formability. The obtained self-supporting clay film was heat-treated at 400 ° C. for 3 hours, then placed in water and allowed to stand overnight, and it was visually determined whether or not the self-supporting clay film was dissolved. The case where dissolution in water was not observed was evaluated as ◯, and the case where dissolution in water was observed was evaluated as ×. The results are shown in Table 1.
[Water resistance (change in moisture absorption)]
The moisture absorption rate before and after the heat treatment was measured using the self-supporting clay film obtained by the evaluation of the film forming property. The obtained self-supporting clay film was heated at 500 ° C. for 12 hours and then left in a constant temperature and high humidity chamber set at a temperature of 40 ° C. and a humidity of 90% for 5 hours. The water absorption was calculated by measuring the mass of the self-supporting clay film after heat treatment at 500 ° C. and the mass of the self-supporting clay film after being left in a constant temperature and high humidity chamber, and calculating the change in mass.
(Example 2)
Synthesis was performed in the same manner as in Example 1 except that 30.8 ml of an aqueous lithium hydroxide solution was added to 10 wt% and hydrothermal synthesis was performed at 150 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1.
(Example 3)
Synthesis was performed in the same manner as in Example 1 except that 30.8 ml of an aqueous lithium hydroxide solution was added to 10 wt% and hydrothermal synthesis was performed at 200 ° C. for 24 hours, and evaluation was performed in the same manner as in Example 1.
Example 4
Synthesis was performed in the same manner as in Example 1 except that 30.8 ml of an aqueous lithium hydroxide solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1.
(Example 5)
Synthesis was performed in the same manner as in Example 1 except that 33.2 ml of lithium hydroxide aqueous solution was added to 10 wt% and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
(Example 6)
Synthesis was performed in the same manner as in Example 1 except that 42.2 ml of lithium hydroxide aqueous solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
(Example 7)
Synthesis was performed in the same manner as in Example 1 except that 50.8 ml of an aqueous lithium hydroxide solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
(Example 8)
Synthesis was performed in the same manner as in Example 1 except that 58.9 ml of an aqueous lithium hydroxide solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
Example 9
Example 1 except that 58.9 ml of lithium hydroxide aqueous solution was added to 10 wt%, hydrothermal synthesis was performed at 200 ° C. for 48 hours, the reaction product generated after hydrothermal synthesis was taken out, and water washing was repeated 5 times. Was synthesized in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.
(Example 10)
40 ml of nitric acid was added to a dispersion obtained by mixing 60 g of amorphous silica (Cab-O-SilM5, manufactured by Cabot) and 600 ml of distilled water. A solution obtained by mixing 182 g of magnesium nitrate (primary reagent) and 256 ml of distilled water was added thereto, and ammonia water (28% aqueous solution) was slowly added dropwise while stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 58.0 ml of 10 wt% lithium hydroxide aqueous solution was added to the well-washed homogeneous composite precipitation dispersion and mixed well to obtain a starting material slurry. The starting material slurry was charged in an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. Evaluation was performed in the same manner as in Example 1.
(Example 11)
Synthesis was performed in the same manner as in Example 10 except that 67.0 ml of lithium hydroxide aqueous solution was added to 10 wt% and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1.
Example 12
Synthesis was performed in the same manner as in Example 10 except that 73.2 ml of lithium hydroxide aqueous solution was added to 10 wt% and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1.
(Example 13)
Synthesis was performed in the same manner as in Example 10 except that 95.6 ml of an aqueous lithium hydroxide solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1.
(Example 14)
A solution of 182 g of magnesium nitrate (primary reagent) and 182 ml of distilled water was mixed with 208 g of ethyl silicate, and ammonia water (28% aqueous solution) was slowly added dropwise with stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 61.6 ml of a 10 wt% aqueous lithium hydroxide solution was added to the well-mixed homogeneous composite precipitation dispersion and thoroughly mixed to obtain a starting raw material slurry. The starting material slurry was charged in an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. Evaluation was performed in the same manner as in Example 1.
(Example 15)
To a dispersion obtained by mixing 71 g of silicon dioxide n hydrate and 600 ml of distilled water, 40 ml of nitric acid was added. A solution obtained by mixing 182 g of magnesium nitrate (primary reagent) and 256 ml of distilled water was added thereto, and ammonia water (28% aqueous solution) was slowly added dropwise while stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 61.6 ml of a 10 wt% aqueous lithium hydroxide solution was added to the well-mixed homogeneous composite precipitation dispersion and thoroughly mixed to obtain a starting raw material slurry. The starting material slurry was charged in an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. Evaluation was performed in the same manner as in Example 1.
(Comparative Example 1)
70 ml of nitric acid was added to a dispersion obtained by mixing 200 g of No. 3 water glass (SiO ₂ : 28%, NaO ₂ : 9%, manufactured by Oso Chemical Co., Ltd.) and 1000 ml of distilled water. A solution obtained by mixing 182 g of magnesium nitrate (primary reagent) and 182 ml of distilled water was added thereto, and an aqueous sodium hydroxide solution (20 wt% aqueous solution) was slowly added dropwise while stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, washing with water by repeated addition of distilled water, shaking, and solid-liquid separation was repeated. The obtained starting material slurry was charged into an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
(Comparative Example 2)
20 ml of nitric acid was added to a dispersion obtained by mixing 60 g of colloidal silica (Ludox ™ 50, manufactured by SigmaAldrich) and 120 ml of distilled water. A solution prepared by mixing 91 g of magnesium nitrate (primary reagent) and 128 ml of distilled water was added thereto, and ammonia water (28% aqueous solution) was slowly added dropwise with stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 16.8 ml of a 10 wt% aqueous lithium hydroxide solution was added to the well-washed homogeneous composite precipitation dispersion and mixed well to obtain a starting raw material slurry. The starting material slurry was charged in an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. In Comparative Example 2, no clay was obtained.
(Comparative Example 3)
Synthesis was performed in the same manner as in Comparative Example 2 except that 84.3 ml of lithium hydroxide aqueous solution was added to 10 wt% and hydrothermal synthesis was performed at 200 ° C. for 48 hours, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
(Comparative Example 4)
40 ml of nitric acid was added to a dispersion obtained by mixing 60 g of amorphous silica (Cab-O-SilM5, manufactured by Cabot) and 600 ml of distilled water. A solution obtained by mixing 182 g of magnesium nitrate (primary reagent) and 256 ml of distilled water was added thereto, and ammonia water (28% aqueous solution) was slowly added dropwise while stirring. The dripping was stopped when the pH reached 10, and the mixture was aged at room temperature overnight to obtain a uniform composite precipitate. Thereafter, water washing by adding distilled water, shaking, and solid-liquid separation was repeated until the ammonia odor disappeared. 19.4 ml of 10 wt% lithium hydroxide aqueous solution was added to the well-washed homogeneous composite precipitation dispersion and mixed well to obtain a starting material slurry. The starting material slurry was charged in an autoclave and hydrothermally reacted at 200 ° C. for 48 hours. After cooling, the reaction product in the autoclave was taken out, dried at 60 ° C., and then pulverized. In Comparative Example 4, no clay was obtained.
(Comparative Example 5)
Synthesis was performed in the same manner as in Comparative Example 4 except that 38.6 ml of an aqueous lithium hydroxide solution was added to 10 wt%, and hydrothermal synthesis was performed at 200 ° C. for 48 hours.

The clay obtained in the example showed a smectite pattern in which the d (001) peak as shown in FIG. 1 appears in the vicinity of 2θ = 6 °, and the desired 2: 1 type 3 octahedral synthetic clay was obtained. I understood. In Examples 7 and 8, a sharp peak due to lithium ions appeared in addition to the above peaks (FIGS. 2A and 2B). In addition, since the peak due to the lithium ion disappeared in Example 9 in which washing was performed after the hydrothermal reaction (FIG. 2 (c)), if the excess lithium ion coexists, It has been shown that it does not affect the properties of the clay and can be removed by post-synthesis washing.
In the clays obtained in the examples, a transparent gel having thixotropic properties was obtained in the water dispersibility evaluation. On the other hand, the clays of Comparative Examples 2 to 5 showed clay precipitation in the evaluation of water dispersibility.
In the evaluation of film formability, the clay obtained in the examples formed a transparent clay film, and had a regular laminated structure as shown in FIG. On the other hand, the clays of Comparative Examples 2 to 5 were white powdery after drying or were shrunk during drying to form a thick white lump in film forming property evaluation.
In the evaluation of water resistance, the clay obtained in the example maintained its shape without dissolving in water. On the other hand, the clay of Comparative Example 1 was dissolved in water and water resistance was not observed.
In Examples 2 to 4, the conditions of the hydrothermal method (hydrothermal reaction temperature, hydrothermal reaction) are within the preferable Li addition amount in an example of the synthesis method of the 2: 1 type 3 octahedral synthetic clay of the present invention of the present invention. The clay having the same water dispersibility and film formability as those of the other examples can be synthesized, and the coated clay film and the self-supporting clay film having the same transparency and water resistance as those of the other examples. Was formed.
In Examples 10 to 15, amorphous silica and silicic acid are used as lithium compounds to be a lithium ion source within the preferable Li addition amount range in one example of the method for synthesizing the 2: 1 type 3 octahedral synthetic clay of the present invention. Synthesis was performed using ethyl and silicon dioxide n-hydrate. As a result, it is possible to synthesize clay having water dispersibility and film formability equivalent to those obtained when colloidal silica is used, and to obtain a coated clay film and a self-supporting clay film having transparency and water resistance equivalent to those of other examples. It was.

Claims (14)

  2: 1 type 3 octahedron synthetic clay containing Li, Si and 0.07 to 0.17, and stevensite containing Mg / Si = 0.65 to 0.72.   The 2: 1 type 3 octahedral synthetic clay according to claim 1, which does not contain Na.   The 2: 1 type 3 octahedral synthetic clay according to claim 1 or 2, wherein the water absorption after the heat treatment at 500 ° C is less than 5%.   The 2: 1 type 3 octahedral synthetic clay according to any one of claims 1 to 3, wherein Li as an impurity is Li / Si <0.15.   A transparent clay gel having thixotropic properties, comprising 2: 1 type 3 octahedral synthetic clay according to any one of claims 1 to 4 and water as a dispersion medium.   A coated clay film using the transparent clay gel according to claim 5.   The coated clay film according to claim 5, wherein the transparency is 90% or more of the total light transmittance.   The coated clay film according to claim 6 or 7, wherein the total light transmittance after heat treatment at 400 ° C or lower is 70% or more.   The coated clay film according to any one of claims 6 to 8, wherein the water resistance is improved by heat treatment.   A self-supporting clay film using the transparent clay gel according to claim 5.   The self-supporting clay film according to claim 10, wherein the transparency is 80% or more of the total light transmittance.   The self-supporting clay film according to claim 10 or 11, having a thickness of 30 to 500 µm.   The self-supporting clay film according to any one of claims 10 to 12, wherein the total light transmittance after heat treatment at 400 ° C or lower is 70% or more.   The self-supporting clay film according to any one of claims 10 to 13, wherein water resistance is improved by heat treatment.