JP5424479B2 - Water-dispersed colloidal solution and method for producing the same - Google Patents

Description

The present invention relates to a water-dispersed colloidal solution obtained by dispersing a layered double hydroxide in water, and more specifically, substantially having the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} The present invention relates to a water-dispersed colloidal solution comprising only the compound shown and a monovalent inorganic anion, wherein the monovalent inorganic anion is in a molar ratio of 0.1 to 0.4 with respect to the compound, and a method for producing the same.

The layered double hydroxide is also called a hydrotalcite-like substance and is represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] [A ⁿ⁻ _{x / n} · mH ₂ O] A compound. Here, M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, x is less than one positive real number, n is a positive integer, m represents a positive real number. The structure of the layered double hydroxide consists of a metal hydroxide layer (base layer) with a positive charge represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , and its interlayer In addition, an anion represented by the general formula [A ⁿ⁻ _{x / n} · mH ₂ O] ⁿ⁻ and an intermediate layer composed of water molecules are alternately stacked to form a layered compound.

  This layered double hydroxide is used as a catalyst carrier, and the double oxide obtained by calcination of the layered double hydroxide as a catalyst. In the plastic field, it is used as a stabilizer, a flame retardant, and a moisture retention improver. It is used as an antacid. In recent years, research on application to drug delivery systems and controlled releases for the purpose of sustained drug efficacy has also been actively conducted. Furthermore, in the environmental field, studies as an adsorbent are also being made. However, in the state of the layered double hydroxide, it is not compatible with the resin and dispersibility is bad, and intensive research has been conducted for this improvement, and in other fields, further improvement in performance and functionality will be achieved. Nano-size is being studied for the purpose.

One of them is a method in which a layered double hydroxide is exfoliated to an elementary layer in an organic solvent to form a colloidal dispersion state. For example, a layered double hydroxide containing glycine (Patent Document 1) or fluorine-based imide (Patent Document 2) in the intermediate layer is prepared, and this is made into a colloidal dispersion state with an organic solvent such as formamide or alcohol. is there. However, since the use of an organic solvent has a problem of harm to the environment, it is desired to develop a water-dispersed colloidal solution from which layered double hydroxide is peeled off using harmless water as a solvent.
As such a water-dispersed colloidal solution, a layered double hydroxide containing an organic compound such as carboxylic acid such as lactic acid (Patent Literature 3, Non-Patent Literature 1) or magnesium lactate (Patent Literature 4) in an intermediate layer. It is disclosed that a water-dispersed colloidal solution can be obtained by exfoliating in a water solvent. However, since the colloidal solution obtained by these disclosed techniques necessarily contains an organic substance derived from the intermediate layer of the layered double hydroxide, for example, in a catalyst application in an organic synthesis reaction, the organic substance causes a side reaction. In addition, when this is coated on various substrates, dried, and fired, it is still difficult to obtain a coating film having high gas transparency and still containing the problem of gas generation.
For this reason, there is a strong demand for a water-dispersed colloidal solution that does not contain organic substances, that is, is composed essentially of only inorganic substances, particularly in fields that require high functionality such as catalysts.

JP2003-221226 JP 2005-272323 A JP 2006-052114 A JP 2008-214127 A

T. Hibino, M. Kobayashi, “Delamination of layered double hydroxides in water”, J. Mater. Chem., 2005, Vol.15, p.653-656

  While the present inventors are diligently studying to solve the required problem, it was discovered by chance that a layered double hydroxide containing only a monovalent inorganic anion in the intermediate layer is dispersed in water. The present invention has been completed on the basis of such findings, and an object is to provide a water-dispersed colloidal solution of a metal hydroxide substantially consisting of an inorganic substance and a method for producing the same.

That is, the present invention substantially consists of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} and a monovalent inorganic anion, and the monovalent inorganic anion Is a water-dispersed colloidal solution having a molar ratio of 0.1 to 0.4 with respect to the compound (provided that
(i) In the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , M ²⁺ represents a divalent metal ion, and M ³⁺ represents a trivalent metal ion.
(ii) _{x in the} general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} is in the range of 0.13 <x <0.28. )

  Furthermore, the present invention provides a mixed aqueous solution of a divalent metal salt composed of a divalent metal ion and a monovalent inorganic anion, and a trivalent metal salt composed of a trivalent metal ion and a monovalent inorganic anion, Reacting with alkaline aqueous solution under neutral to alkaline conditions, co-precipitating divalent metal component and trivalent metal component to synthesize and wash layered double hydroxide, and disperse it in water And a method for producing the water-dispersed colloidal solution.

  As described above, the water-dispersed colloidal solution of the present invention is composed of only a basic layer and a monovalent inorganic anion that does not substantially contain an organic substance. Can be avoided, and its use is remarkably wide. Furthermore, since the water-dispersed colloidal solution of the present invention has a low viscosity and is highly dispersed and nanosized, it has high transparency. Accordingly, the water-dispersed colloidal solution of the present invention includes a wide range of applications including catalysts requiring high functionality, coating agents requiring high transparency, cosmetics and resin compounding agents requiring high dispersibility, and optical functional materials. Applications can be expected.

The water-dispersed colloidal solution of the present invention is an aqueous dispersion substantially consisting of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} and a monovalent inorganic anion. Type colloidal solution.
Here, “substantially” means that the water-dispersed colloidal solution of the present invention does not contain any organic substance except for organic substances derived from impurities in the raw material in the production of the water-dispersed colloidal solution of the present invention. .

As is well known, the compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} is a divalent metal ion M ²⁺ and a trivalent metal ion M ^3+. It is a sheet-like compound formed by crosslinking with oxygen atoms of a hydroxyl group, and is a metal hydroxide layer peeled off from a layered double hydroxide, that is, a basic layer. Here, the layered double hydroxide is a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] [A ⁿ⁻ _{x / n} · mH ₂ O], and M ^{2 +} is a divalent metal ion, M ³⁺ is a trivalent metal ion, a ^n-represents an n-valent anion, x is less than one positive real number, n represents a positive integer, m is a positive real number Indicates. The structure of the layered double hydroxide includes a metal hydroxide layer represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} and a general formula [A ⁿ⁻ _{x /} and _n · mH ₂ O] intermediate layer consisting of anions and water molecules represented by ^n- is one that alternately stacked.

As a specific example of the divalent metal ion M ^{2+ in} the compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} in the water-dispersed colloidal solution of the present invention, Mg ^{2 Examples} include ⁺ , Ca ²⁺ , Sr ²⁺ , Pd ²⁺ , Ba ²⁺ , Zn ²⁺ , Co ²⁺ , Ni ²⁺ , Pt ²⁺ , Cu ²⁺ , and Fe ²⁺ . Among these, Mg ²⁺ and Zn ²⁺ can be suitably used because the layered double hydroxide as a precursor can be easily obtained in a single phase. Of these, Mg ²⁺ and Zn ²⁺ may be used ^alone or in combination. Specific examples of the trivalent metal ion M ³⁺ include Al ³⁺ , Ga ³⁺ , Fe ³⁺ , Co ³⁺ , Au ³⁺ , Ce ³⁺ , Bi ^{3+ and the} like. Among these, Al ³⁺ has high stability as a trivalent ion, and therefore can be suitably used for preparing a layered double hydroxide that is a precursor of an aqueous dispersion colloidal solution. In the water-dispersed colloidal solution of the present invention, a combination of Mg ²⁺ and / or Zn ²⁺ and Al ³⁺ is particularly preferable as a combination of a divalent metal ion and a trivalent metal ion.

In the layered double hydroxide, the upper limit of x in the general formula [M ²⁺ _1−x M ³⁺ _x (OH) ₂ ] ^{x +} is generally said to be 0.33. However, when x is such a value, the water-dispersed colloidal solution of the present invention is not desired. As a result of various investigations, it was found that a stable colloidal solution was obtained when x was in the range of 0.13 <x <0.28, but the stability of the colloidal solution was drastically improved particularly in the range of 0.15 <x <0.22. .

Examples of the monovalent inorganic anion contained in the water-dispersed colloidal solution of the present invention include I ⁻ , Br ⁻ , Cl ⁻ , F ⁻ , NO ₃ ⁻ , NO ₂ ⁻ , ClO ₄ ⁻ , ClO ⁻ and PF _{6. ^{-, BF 4 -, SCN -}} , CN -, OH - can be exemplified. These monovalent inorganic anions may be used alone or in combination of two or more. Among these, in particular, Cl ⁻ and NO ₃ ^— can be suitably used for stably dispersing the water-dispersed colloidal solution of the present invention. Most monovalent inorganic anions are derived from an intermediate layer consisting of an anion represented by [A ⁿ⁻ _{x / n} · mH ₂ O] ⁿ⁻ and water molecules in the general formula of the layered double hydroxide. However, those derived from the anion of the acid added as necessary to further stabilize the colloidal solution are also included. Type of anions of the acid is not necessarily the same as the anion of the intermediate layer, OH ^- it is not particularly limited as long as it is within the range of types of anions shown above except.

Next, regarding the amount of monovalent inorganic anion, as described above, this amount is the anion derived from the layered double hydroxide and the acid added as necessary to further stabilize the colloidal solution. It is the total amount with the derived anion. That is, the amount of the monovalent inorganic anion is in the range of 0.1 to 0.4 in terms of molar ratio with respect to the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} . When the molar ratio is in the range of 0.1 to 0.4, it is possible to obtain a water-dispersed colloidal solution in a stable state in which colloidal particles are notably dissolved, and white turbidity and aggregation are not observed during production and storage.

The water-dispersed colloidal solution of the present invention can be obtained in a concentration range of 20% by mass or less as [M2 ⁺ _1- ^{xM3 +} _x (OH) ₂ ] ^{x +} . In order to keep the colloid solution in a more stable state, the concentration is preferably 15% by mass or less, more preferably 12% by mass or less. As for the lower limit of the concentration, no matter how low the colloidal solution quality is, there is no problem, but from a practical point of view, [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} is 5% by mass or more. It is preferable to contain. If the content is 20% by mass or more, the viscosity of the colloidal solution becomes high, and it is difficult to obtain a stable colloidal solution.

  In the preparation of the water-dispersed colloidal solution of the present invention, the process of colloidalization and the properties of the obtained solution were determined according to the method disclosed in Patent Document 3 specifically describing the contents of Non-Patent Document 1 (after the preparation example). The same behavior as the colloidal solution prepared in [Reference Example] is shown. Non-Patent Document 1 and Patent Document 3 are methods in which a layered double hydroxide containing an organic acid in an intermediate layer is prepared, and then the layered double hydroxide is delaminated to form a colloidal solution. From this, it can be presumed that the colloidal solution of the present invention is also colloidalized by delamination of the layered double hydroxide.

Next, the method for producing the water-dispersed colloidal solution of the present invention will be described in detail.
The method for producing a water-dispersed colloidal solution according to the present invention is a method in which a layered double hydroxide is first synthesized as a precursor of a water-dispersed colloidal solution, then washed and dispersed in water.
In the present invention, this layered double hydroxide is synthesized by a coprecipitation method. The reason why the coprecipitation method is used in the present invention is that, as a result of various studies, a layered double hydroxide having a small crystal size, that is, a layered double water having a small thickness in the stacking direction and a small area of the metal hydroxide sheet. This is because an oxide is obtained, the intermediate layer is easily in contact with water, and delamination is easy, that is, colloidalization and nano-sizing are easy.

  There are several methods for synthesizing the layered double hydroxide as a precursor. To obtain the water-dispersed colloidal solution of the present invention, it is optimal to synthesize by the coprecipitation method. In the coprecipitation method, divalent metal ions and trivalent metal ions are hydroxylated by neutralizing the mixed aqueous solution of divalent metal salt and trivalent metal salt with an alkaline aqueous solution while maintaining an appropriate pH. In this method, a layered double hydroxide is obtained by coprecipitation as a product. When this method is used, colloidalization is the easiest, and the resulting water-dispersed colloidal solution is also most stable.

In the present invention, the divalent metal salt and the trivalent metal salt used in the synthesis of the layered double hydroxide are organic substances that can be incorporated between the metal hydroxide layers or inorganic anions having a valence of 2 or more. It does not contain. Examples of the divalent and trivalent metal ions include the same as described above, and salts thereof are as follows. That is, as salts of divalent metal ions, Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Zn ²⁺ , Pd ²⁺ , Co ²⁺ , Ni ²⁺ , Pt ²⁺ , Cu ² Examples include ⁺ , Fe ²⁺ chloride or nitrate. Examples of the trivalent metal ion salt include chlorides or nitrates of Al ³⁺ , Ga ³⁺ , Fe ³⁺ , Co ³⁺ , Au ³⁺ , Ce ³⁺ , Bi ³⁺ . Among these, the divalent metal salt is particularly preferably at least one of magnesium chloride, magnesium nitrate, zinc chloride, and zinc nitrate, and the trivalent metal salt is either aluminum chloride or aluminum nitrate or Both are particularly preferred.

The mixing ratio of the divalent metal salt and the trivalent metal salt is preferably such that the layered double hydroxide is obtained in a single phase. That is, ^x in the compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} in the finally obtained colloid solution is in the range of 0.13 <x <0.28. It is desirable to determine the mixing ratio of the divalent metal salt and the trivalent metal salt.

The neutralization method will be further described. First, an aqueous solution (hereinafter referred to as an aqueous solution A) adjusted to pH 7 to 12 using an alkali is prepared. Examples of the alkali used here include sodium hydroxide and potassium hydroxide. Next, a mixed aqueous solution of a divalent metal salt and a trivalent metal salt is added to the aqueous solution A under stirring. However, with this operation alone, the neutralization reaction hardly proceeds because the pH drops instantaneously due to the addition of the metal salt. Accordingly, in order to proceed with the neutralization reaction, an aqueous alkali solution is appropriately added simultaneously with the addition of the metal salt, and neutralization is performed while maintaining an optimum pH. The optimum neutralization pH differs depending on the type of divalent metal salt and trivalent metal salt used, but it is neutral to alkaline, and the numerical range is generally within the range of pH 7-12. When magnesium chloride and / or zinc chloride is used as the divalent metal salt and aluminum chloride is used as the trivalent metal salt, the pH range of 9 to 11 is more preferable.
The alkaline aqueous solution used for neutralization is not particularly limited as long as the layered double hydroxide that becomes the precursor of the present invention can be obtained by neutralization, but sodium hydroxide and potassium hydroxide are preferable examples.

In order to stabilize the pH during neutralization, salts such as a buffering agent may be added to the aqueous solution A and the alkaline aqueous solution used for neutralization, if necessary. Such a salt may be any salt composed of a monovalent inorganic anion, and examples thereof include sodium chloride, potassium chloride, sodium hypochlorite, sodium perchlorate, and hydrogen peroxide.
The amount of the salt is not particularly limited as long as the layered double hydroxide is obtained, but is generally 10% by mass or less based on the total amount of the reaction solution.

  As described above, in the neutralization method of the present invention, it is extremely important to carry out the neutralization reaction on the alkali side. At the same time, an indispensable factor in the production method of the present invention is the addition time of the mixed aqueous solution of the above divalent metal salt and trivalent metal salt. To explain this, the addition time of the mixed aqueous solution of the divalent metal salt and the trivalent metal salt is optimally set in the range of 2 minutes to 50 minutes. That is, when added for longer than 50 minutes, the layered double hydroxide is obtained in a single phase, but the colloidal solution obtained by the subsequent treatment becomes cloudy, and the water-dispersed colloidal solution of the present invention is obtained. It becomes extremely difficult. On the other hand, when added in less than 2 minutes, it becomes difficult to maintain an optimum pH range for neutralization with an aqueous alkaline solution, resulting in the formation of an impurity phase in addition to the layered double hydroxide, which is dispersed. Even if it is processed, it is difficult to obtain a highly transparent colloidal solution.

The concentration at the time of neutralization is not particularly limited, but the raw material is blended so that the slurry concentration at the end of neutralization is 0.5 to 4.0% by mass as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , It is recommended to add. That is, if the concentration is less than 0.5% by mass, the productivity is poor because the concentration is low, and if the concentration exceeds 4.0% by mass, the viscosity tends to be very viscous and stirring during the reaction tends to be difficult.

  The layered double hydroxide obtained by the coprecipitation method as described above contains a large amount of excess salts and does not colloid in this state. Therefore, a step of washing and desalting (hereinafter referred to as a desalting step) is indispensable in order to separate the produced layered double hydroxide from the by-product salt. In the present invention, there is no particular problem as long as the layered double hydroxide can be sufficiently desalted under conditions that do not dry, for example, a method of repeatedly performing ion exchange or decantation, filtration treatment such as ultrafiltration or suction filtration, etc. The method of repeating repeatedly, pouring suitably is mentioned. The degree of desalting is about 50 ppm or less of the total amount of by-product salt produced during the neutralization reaction, that is, washing until the decantation waste liquid or filtrate has an electrical conductivity (EC) of approximately 150 μS / cm or less. It is desirable to do.

The layered double hydroxide after the desalting step is subjected to a dispersion treatment in a turbid state in water without drying. Although the appearance in this turbid state is a white slurry, it becomes a transparent colloidal solution by dispersion treatment. The dispersion treatment is preferably performed at a concentration of 15% by mass or less as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} . If it exceeds 15% by mass, colloidalization by dispersion treatment becomes difficult.

In addition, it is possible to add an acid for the purpose of adjusting pH during the dispersion treatment. This is added for the purpose of further stabilizing the colloidal solution by keeping the pH of the colloidal solution obtained after the dispersion treatment away from the isoelectric point of [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +.} is there. The type of acid to be added need not be an acid containing the same anion as the monovalent anion derived from the divalent and trivalent metal salts, but I ⁻ , Br ⁻ , Cl ⁻ , F shown above. One or two or more of monovalent acids containing ⁻ , NO ₃ ⁻ , NO ₂ ⁻ , ClO ₄ ⁻ , ClO ⁻ , PF ₆ ⁻ , BF ₄ ⁻ , SCN ⁻ and CN ⁻ as anions. Of these, hydrochloric acid or nitric acid is more preferable. In general, the rate of colloidalization tends to be slowed by surplus anions, that is, anions other than those derived from layered double hydroxides, but aggregation tends to occur simultaneously with the progress of colloidalization. In some cases, excess anions may be effective in inhibiting the progress of aggregation.

The amount of monovalent acid added for the purpose of adjusting the pH is determined by the total amount of monovalent inorganic anions contained in the finally obtained colloidal solution represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] can be added in a molar ratio of 0.1 to 0.4 with respect to ^{x +} . When the molar ratio is in the range of 0.1 to 0.4, a water-dispersed colloidal solution in a stable state is obtained in which the layered double hydroxide is dissolved by an acid, and is less prone to white turbidity or aggregation during production and storage of the colloidal solution. Can do.

Examples of the dispersion treatment method include a room temperature aging method, a sonication method, and a heat treatment method that are allowed to stand at room temperature for about 5 to 12 days. Among these, the ultrasonic treatment method is not preferable because the metal hydroxide of [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} may be destroyed by ultrasonic waves. In view of industrial production, the heat treatment method is most preferable.

  The heating temperature in the heat treatment method is preferably in the temperature range of 40 to 100 ° C. That is, when the temperature is lower than 40 ° C., the time required for colloidalization is remarkably increased and productivity is deteriorated. On the other hand, when the temperature exceeds 100 ° C., the colloidalization takes place in a very short time. However, if the heating time is not strictly controlled, the colloidal solution becomes opaque and precipitates due to aggregation. The time for the heat treatment is not particularly limited as long as the colloidal solution is obtained, but it can be colloided in about 30 minutes to 6 hours.

The obtained colloidal solution can be concentrated to a required concentration by ultrafiltration, an evaporator or the like. However, the upper limit of the concentration stable as a colloidal solution is 20% by mass as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , and 15% by mass or less to maintain a more stable state. The concentration is preferable, and more preferably 12% by mass or less. Regarding the lower limit of the concentration, no matter how low the concentration of the colloidal solution is, there is no problem, but it is preferably 5% by mass or more from a practical viewpoint.

In the production of the water-dispersed colloidal solution of the present invention, CO ₃ ²⁻ derived from atmospheric carbon dioxide gas may be mixed into the colloidal solution, but CO ₃ ²⁻ has an interlayer cohesive strength of the layered double hydroxide. In order to strengthen, it is desirable to avoid contamination during the production of the layered double hydroxide as much as possible. As a method for avoiding the contamination of CO ₃ ²⁻ as much as possible, it is desirable to produce in an atmosphere of an inert gas such as nitrogen or argon, but there is no particular limitation as long as the method can avoid contamination as much as possible.

  As described above, the reason why the layered double hydroxide composed only of the inorganic substance of the present invention containing no special release agent or dispersant between the layers is colloidalized in the same manner as in Patent Document 3 (Japanese Patent Laid-Open No. 2006-52114). Not sure about. However, the reason for this is that because of the use of layered double hydroxides with a small crystal size, water molecules are likely to be taken in between the layers, and the water molecules are thermally vibrated to spread the layers and cause a peeling reaction. It is presumed that In other words, this difference of about 30 minutes to 6 hours in the heat treatment method compared to about 5 to 12 days in the room temperature aging method is considered to be due to the difference in thermal vibration force of water molecules. It is done.

The water-dispersed colloidal solution of the present invention thus obtained shows the appearance of a translucent to transparent white solution.
When the range of transparency of the water-dispersed colloidal solution of the present invention is expressed in terms of total light transmittance (hereinafter referred to as transmittance) and haze rate, [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} In the colloidal solution containing 0.5% by mass, the transmittance is 30% or more and the haze ratio is 55% or less. More preferably, the transmittance is 30% or more and the haze ratio is 55% or less when stored at room temperature after one month of production.

Further, the viscosity of the water-dispersed colloidal solution of the present invention is such that a colloidal solution containing 10% by mass of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} is an E-type viscometer. Is approximately 1.5 mPa · s to 5.0 mPa · s, so that it is easy to handle and extremely easy to mix and disperse with other substances such as resins.

  Furthermore, the dispersed particle diameter (median diameter) of the water-dispersed colloidal solution of the present invention is generally in the range of 10 nm to 150 nm as measured by a dynamic light scattering particle size distribution measuring device (LB-500 manufactured by Horiba, Ltd.). Since it is nano-sized, it has a number of characteristics such as being able to obtain a good-quality mixture by uniformly dispersing in mixing with various substances.

  The water-dispersed colloidal solution of the present invention can be used for various applications such as resin additives such as flame retardants, harmful substance removing agents utilizing cation adsorption ability, battery materials, UV absorbers, rust preventives, and catalysts. It is. At this time, if necessary, various additives can be added to the colloid solution of the present invention within a range in which the colloidal state can be maintained. Examples of additives include amines such as diethanolamine, tetramethylammonium hydroxide, ammonia, organic acids such as acetic acid, propionic acid, citric acid and lactic acid, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, etc. And organic surfactants such as sodium alkyl sulfonate, polyoxyethylene alkyl ether, polyoxyethylene sorbitan fatty acid ester, carboxybetaine, and the like.

The colloidal solution of the present invention is a colloidal solution dispersed in water. However, since it has a high affinity with an organic solvent, it can be made into an organic solvent-dispersed colloidal solution by replacing the aqueous solvent with an organic solvent. . Examples of the organic solvent include alcohols such as methanol, ethanol and isopropanol, ethers such as tetrahydrofuran and diethyl ether, cellosolves such as 2-methoxypropanol and 2-n-butoxyethanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, Examples include formamide and dimethyl sulfoxide.
Examples of the present invention are shown below, but the present invention is not particularly limited thereby.

Example 1
234 g of magnesium chloride hexahydrate and 64 g of aluminum chloride hexahydrate were dissolved in 252 g of pure water to prepare an aqueous metal salt solution. This metal salt aqueous solution was added with stirring to 2000 g of a 2.5% sodium chloride aqueous solution adjusted to pH 10 with sodium hydroxide. The addition time of the metal salt aqueous solution was 5 minutes. At this time, a sodium hydroxide aqueous solution adjusted to 20% by mass was appropriately added so as to keep the pH in the range of 9 to 11. The coprecipitation slurry obtained by the above operation was desalted by washing by ultrafiltration until the filtrate EC reached 70 μS / cm. The resulting solution was not colloidal but had a white slurry appearance with very low transparency (hereinafter, this slurry is referred to as “slurry A”). This slurry A was subdivided and subjected to the following Examples 1-1 to 1-5. The powder obtained by drying the slurry A at 100 ° C. has a bottom reflection at 2θ = 10.9 degrees as measured by an X-ray diffractometer (hereinafter referred to as XRD) (XRD-7000 manufactured by Shimadzu Corporation). It was confirmed that the layered double hydroxide was obtained in a single phase.

[Example 1-1]
The slurry A was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. Based on the results of elemental analysis and gravimetric analysis using an X-ray fluorescence spectrometer (PW2400 manufactured by Philips) (hereinafter referred to as XRF), the colloidal solution contains a metal with the composition [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18+ It was revealed that the hydroxide layer was 10.8% by mass and chlorine was 1.23% by mass. That is, Cl ⁻ / [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18+ (molar ratio) = 0.19. The yield of the metal component (hereinafter referred to as the yield) calculated from the amount of the metal salt of the raw material and the amount of the metal hydroxide layer in the colloidal solution was about 90%.

[Example 1-2]
The slurry A was heated at 90 ° C. for 1 hour to obtain a white transparent colloidal solution. The composition and concentration of the metal hydroxide layer in the colloidal solution and the chlorine concentration are the same as in Example 1-1.

[Example 1-3]
A white transparent colloidal solution was obtained by heating the slurry A at 50 ° C. for 6 hours. The composition and concentration of the metal hydroxide layer in the colloidal solution and the chlorine concentration are the same as in Example 1-1.

[Example 1-4]
A 1% by mass hydrochloric acid aqueous solution was added to Slurry A at a molar ratio of 0.025 to [Mg _0.82 Al _0.18 (OH) ₂ ] ^{0.18 and} heated at 70 ° C. for 5 hours to obtain a white transparent colloidal solution. From the results of elemental analysis and gravimetric analysis by XRF, it was revealed that [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18+ was 10.0 mass% and chlorine was 1.33 mass% in the colloidal solution. That is, Cl ⁻ / [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18+ (molar ratio) = 0.22. The colloidal solution obtained under these conditions was particularly stable, and even when stored at 50 ° C. for 1 month, the transmittance, haze ratio, and viscosity remained almost unchanged from the initial values.

[Example 1-5]
A white transparent colloidal solution was obtained by aging the slurry A at room temperature for 10 days. The composition and concentration of the metal hydroxide layer in the colloidal solution and the chlorine concentration were the same as in Example 1-1.

(Example 2)
Layered double hydroxide as in Example 1 except that a metal salt aqueous solution in which 221 g of magnesium chloride hexahydrate and 76 g of aluminum chloride hexahydrate were dissolved in 253 g of pure water was used and the addition time was 10 minutes. A slurry of the product was made. When XRD measurement was performed on the powder dried at 100 ° C., it was confirmed that a layered double hydroxide having bottom reflection at 2θ = 11.2 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. From the results of elemental analysis and gravimetric analysis by XRF, it was revealed that [Mg _0.77 Al _0.23 (OH) ₂ ] ^0.23+ was 10.6% by mass and chlorine was 1.40% by mass in the colloidal solution. That is, Cl ⁻ / [Mg _0.77 Al _0.23 (OH) ₂ ] ^0.23+ (molar ratio) = 0.22.

Example 3
Layered double hydroxide as in Example 1, except that an aqueous metal salt solution in which 124 g of magnesium chloride hexahydrate and 26 g of aluminum chloride hexahydrate were dissolved in 125 g of pure water was used and the addition time was 40 minutes. A slurry of the product was made. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that a layered double hydroxide having bottom reflection at 2θ = 10.9 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. The results of elemental analysis and gravimetric analysis by XRF revealed that [Mg _0.84 Al _0.16 (OH) ₂ ] ^0.16+ was present in the colloidal solution at 10.2% by mass and chlorine at 0.96% by mass. That is, Cl ⁻ / [Mg _0.84 Al _0.16 (OH) ₂ ] ^0.16+ (molar ratio) = 0.16.

Example 4
A layered double hydroxide slurry was prepared in the same manner as in Example 1 except that an aqueous metal salt solution in which 88 g of zinc chloride and 64 g of aluminum chloride hexahydrate were dissolved in 398 g of pure water was used. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that a layered double hydroxide having a bottom reflection at 2θ = 11.0 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. From the results of elemental analysis and gravimetric analysis by XRF, it was found that [Zn _0.81 Al _0.19 (OH) ₂ ] ^0.19+ was 10.0% by mass and chlorine was 0.73% by mass in the colloidal solution. That is, Cl ⁻ / [Zn _0.81 Al _0.19 (OH) ₂ ] ^0.19+ (molar ratio) = 0.19.

Example 5
A white slurry was obtained in the same manner as in Example 1, except that an aqueous metal salt solution in which 117 g of magnesium chloride hexahydrate, 44 g of zinc chloride and 64 g of aluminum chloride hexahydrate were dissolved in 389 g of pure water was used. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that a layered double hydroxide having a bottom reflection at 2θ = 11.0 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. The results of elemental analysis and gravimetric analysis by XRF revealed that [Mg _0.39 Zn _0.41 Al _0.20 (OH) ₂ ] ^0.20+ was present in 10.1% by mass and chlorine was 0.90% by mass in the colloidal solution. That is, it was Cl ⁻ / [Mg _0.39 Zn _0.41 Al _0.20 (OH) ₂ ] ^0.20+ (molar ratio) = 0.19.

Example 6
A white slurry was obtained in the same manner as in Example 1 except that an aqueous metal salt solution in which 295 g of magnesium nitrate hexahydrate and 100 g of aluminum nitrate nonahydrate were dissolved in 155 g of pure water was used. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that a layered double hydroxide having a bottom reflection at 2θ = 11.0 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. From the results of elemental analysis and gravimetric analysis by XRF, it was found that [Mg _0.80 Al _0.20 (OH) ₂ ] ^0.20+ was present in the colloidal solution at 10.5 mass% and nitrate ions at 2.2 mass%. That is, nitrate ion / [Mg _0.80 Al _0.20 (OH) ₂ ] ^0.20+ (molar ratio) = 0.20.

Example 7
A layered double hydroxide slurry was prepared in the same manner as in Example 1 except that a metal salt aqueous solution in which 251 g of magnesium chloride hexahydrate and 48 g of aluminum chloride hexahydrate were dissolved in 251 g of pure water was used. When XRD measurement was performed on the powder dried at 100 ° C., it was confirmed that the layered double hydroxide having bottom reflection at 2θ = 10.7 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. From the results of elemental analysis and gravimetric analysis by XRF, it was revealed that [Mg _0.86 Al _0.14 (OH) ₂ ] ^0.14+ was present at 10.6% by mass and chlorine at 0.89% by mass in the colloidal solution. That is, Cl ⁻ / [Mg _0.86 Al _0.14 (OH) ₂ ] ^0.14+ (molar ratio) = 0.14.

(Example 8)
A layered double hydroxide slurry was prepared in the same manner as in Example 1 except that a metal salt aqueous solution in which 209 g of magnesium chloride hexahydrate and 87 g of aluminum chloride hexahydrate were dissolved in 254 g of pure water was used. When XRD measurement was performed on the powder dried at 100 ° C., it was confirmed that the layered double hydroxide having bottom reflection at 2θ = 11.0 degrees was obtained in a single phase. The layered double hydroxide slurry was heated at 70 ° C. for 2 hours to obtain a white transparent colloidal solution. The results of elemental analysis and gravimetric analysis by XRF revealed that [Mg _0.74 Al _0.26 (OH) ₂ ] ^0.26+ was 10.7% by mass and chlorine was 1.61% by mass in the colloidal solution. That is, Cl ⁻ / [Mg _0.74 Al _0.26 (OH) ₂ ] ^0.26+ (molar ratio) = 0.25.

(Comparative Example 1)
A white slurry was obtained in the same manner as in Example 1 except that an aqueous metal salt solution in which 279 g of magnesium chloride hexahydrate and 22 g of aluminum chloride hexahydrate were dissolved in 249 g of pure water was used. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., a brucite structure derived from magnesium hydroxide was confirmed in addition to the layered double hydroxide having bottom reflection at 2θ = 10.9 degrees. Although this was heated at 70 ° C. for 2 hours, it remained as a cloudy slurry solution, and no colloidal solution was obtained. The results of elemental analysis and gravimetric analysis by XRF revealed that [Mg _0.92 Al _0.08 (OH) ₂ ] ^0.08+ was present in the slurry at 11.0% by mass and chlorine at 1.27% by mass. That is, Cl ⁻ / [Mg _0.92 Al _0.08 (OH) ₂ ] ^0.08+ (molar ratio) = 0.19.

(Comparative Example 2)
A white slurry was obtained in the same manner as in Example 1 except that an aqueous metal salt solution in which 192 g of magnesium chloride hexahydrate and 104 g of aluminum chloride hexahydrate were dissolved in 254 g of pure water was used. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that a layered double hydroxide having a bottom reflection at 2θ = 11.4 degrees was obtained in a single phase. Although this was heated at 70 ° C. for 2 hours, it remained as a cloudy slurry solution, and no colloidal solution was obtained. The results of elemental analysis and gravimetric analysis by XRF revealed that [Mg _0.66 Al _0.34 (OH) ₂ ] ^0.34+ was present in the slurry at 10.5% by mass and chlorine at 2.15% by mass. That is, Cl ⁻ / [Mg _0.66 Al _0.34 (OH) ₂ ] ^0.34+ (molar ratio) = 0.34.

(Comparative Example 3)
When 10 mass% hydrochloric acid aqueous solution was added at a molar ratio of 0.4 to [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18 to the slurry A of the layered double hydroxide shown in Example 1 (chloride ions in the slurry) / [Mg _0.82 Al _0.18 (OH) ₂ ] ^0.18+ (molar ratio) = 0.59), the slurry was colorless and transparent and had no Tyndall phenomenon, and the layered double hydroxide was completely dissolved. That is, a colloidal solution could not be obtained.

[Reference example]
The synthesis was performed according to the method of Patent Document 3, which specifically describes the contents of Non-Patent Document 1.
73.9 g of magnesium lactate trihydrate and 19.6 g of aluminum lactate were dissolved in 406.5 g of pure water to prepare an aqueous metal salt solution. This metal salt aqueous solution was added to 500 g of 20% sodium lactate aqueous solution under stirring in a nitrogen atmosphere. At this time, a 20% by mass aqueous sodium hydroxide solution was appropriately added so as to keep the pH in the range of 9.5 to 10.5. The coprecipitation slurry obtained by the above operation was washed and desalted by ultrafiltration treatment until the filtrate EC became 70 μS / cm to obtain a white slurry. When XRD measurement was performed on the powder obtained by drying this slurry at 100 ° C., it was confirmed that the layered double hydroxide was obtained in a single phase. When this was aged at room temperature for 10 days, a white transparent colloidal solution was obtained with the same behavior as in Examples 1-8. From the results of elemental analysis and gravimetric analysis by XRF, it was confirmed that the colloidal solution contained 4.6% by mass of [Mg _0.81 Al _0.19 (OH) ₂ ] ^0.19+ . Further, when the total organic carbon content was measured by a total organic carbon analyzer (TOC-Vc manufactured by Shimadzu Corporation) and converted into the molecular weight of lactic acid, it was confirmed that 1.55% by mass of lactic acid was present. That is, CH ₃ CH (OH) COO ⁻ / [Mg _0.81 Al _0.19 (OH) ₂ ] ^0.19+ (molar ratio) = 0.22.
The yield of this colloidal solution was as low as about 35%. This is because the magnesium and aluminum components, which are the components of the layered double hydroxide, are not captured by the ultrafiltration membrane in the desalting process by ultrafiltration treatment, but are mixed into the filtrate and discharged out of the system. It was because it was done. This is because the metal ion component is stabilized by the organic acid (complex formation, etc.), so the formation of the metal hydroxide layer that should be neutralized by the addition of the alkaline aqueous solution does not proceed sufficiently, and as a result, a large amount It was speculated that this metal ion component remained unreacted, and the unreacted ion component was not captured by the filtration membrane during the ultrafiltration treatment and was discharged out of the system as a filtrate. Concentration of the colloidal solution was attempted with an ultrafiltration device until the liquid volume allowed by the device. However, because the yield was low, the result was 4.6 mass as [Mg _0.81 Al _0.19 (OH) ₂ ] ^0.19+. Only% colloidal solution was obtained.

For the colloidal solutions and slurries obtained in these Examples and Comparative Examples, the transmittance, haze ratio, particle diameter, and viscosity after 1 day of synthesis were measured. Further, for Examples 1 to 8, the concentration of the colloidal solution was adjusted to [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} at 10% by mass and then permeated after storage at room temperature for 1 month. Rate, haze ratio, and viscosity were measured. These measurements were performed by the following method, and the results are shown in Table 1.

<Measurement of transmittance and haze ratio>
The obtained colloidal solution or slurry is diluted with pure water so as to be 0.5% by mass as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , and then manufactured by Nippon Denshoku Industries Co., Ltd. The transmittance and haze ratio were measured with a side color difference meter ND-300A.
<Measurement of dispersed particle size>
The obtained colloidal solution or slurry is diluted with pure water to [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} to 1% by mass, and then manufactured by Horiba Ltd. The dispersed particle diameter (median diameter) was measured with a light scattering particle size distribution analyzer LB-500.
<Measurement of viscosity>
The viscosity of the colloidal solution having a concentration of 10% by mass as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} was measured using an E-type viscometer manufactured by Tokimec Corporation.

※ 4.6質量％時の粘度 Table 1

* Viscosity at 4.6% by mass

Claims (9)

It consists of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} and a monovalent inorganic anion, and the monovalent inorganic anion has a molar ratio of 0.1 to the compound. Water-dispersed colloidal solution in the range of ~ 0.4 (however,
(i) In the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} , M ²⁺ represents a divalent metal ion, and M ³⁺ represents a trivalent metal ion.
(ii) _{x in the} general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} is in the range of 0.13 <x <0.28.
(iii) The water-dispersed colloidal solution does not contain organic substances except organic substances derived from impurities in the raw material. ). The water-dispersed colloidal solution according to claim 1, wherein the divalent metal ion is Mg ²⁺ and / or Zn ²⁺ and the trivalent metal ion is Al ³⁺ . Monovalent inorganic anions Cl ^- or NO ₃ ^- a water-dispersible colloidal solution according to claim 1 or 2, wherein. The water-dispersed colloidal solution according to any one of claims 1 to 3, containing 5 to 20% by mass of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} . A water-dispersed colloidal solution containing 0.5% by mass of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} has a total light transmittance of 30% or more and a haze ratio of 55%. The water-dispersed colloidal solution according to any one of claims 1 to 4, which is the following. A water-dispersed colloidal solution containing 10% by mass of a compound represented by the general formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^{x +} has a viscosity of 1.5 mPa · s to 5.0 mPa · s. The water-dispersed colloidal solution according to any one of 1 to 5. A mixed aqueous solution of a divalent metal salt composed of a divalent metal ion and a monovalent inorganic anion, a trivalent metal ion composed of a trivalent metal ion and a monovalent inorganic anion, and an alkaline aqueous solution. It is characterized by synthesizing and washing a layered double hydroxide by co-precipitation of a divalent metal component and a trivalent metal component by reacting under alkaline to alkaline conditions, and dispersing this in water The method for producing a water-dispersed colloidal solution according to any one of claims 1 to 6 . The divalent metal ion of the divalent metal salt is Mg ²⁺ and / or Zn ²⁺ , and the monovalent inorganic anion is Cl ⁻ or NO ₃ ⁻ ,
The trivalent metal ions of trivalent metal salt is Al ^3+, 1 monovalent inorganic anions Cl ^- or NO ₃ ^- is The process of claim 7 water-dispersible colloidal solution wherein. The method for producing a water-dispersed colloidal solution according to claim 7 or 8 , wherein the temperature when dispersed in water is 40 ° C to 100 ° C.