JP2013112560A - Layered double hydroxide particle group, method for producing the same, layered double hydroxide dispersion, and layered double hydroxide-added resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a layered double hydroxide particle group having a small average particle size of aggregate particles by a simple step, and to produce a layered double hydroxide dispersion and a layered double hydroxide-added resin by using the layered double hydroxide particle group.SOLUTION: This method for producing a layered double hydroxide particle group includes: a mixed liquid preparing step of preparing mixed liquid containing a layered double hydroxide particle group comprising aggregate particles of a layered double hydroxide represented by general formula MM(OH)(A)mHO (wherein Mis a divalent metal, Mis a trivalent metal, and Ais an n-valent negative ion, under the condition of 0<x<1 and m>0) and having an average crystallite size of ≤20 nm; and a classification step of subjecting the aggregate particles to centrifugal separation, and reducing the average particle size of the aggregate particles by utilizing a difference of the specific gravity.

Description

  The present invention relates to a layered double hydroxide particle group, a production method thereof, a layered double hydroxide dispersion, and a layered double hydroxide-added resin.

  Layered double hydroxides such as hydrotalcite have a structure in which various ions, molecules and the like can be inserted between layers, and can exhibit an anion exchange function. For this reason, it is utilized for uses, such as an ion exchange agent, an adsorbent, and a deodorizing agent, using the said anion exchange function. For example, a resin composition containing a halogen is unstable with respect to heat and light, and is discolored or deteriorated by heating or ultraviolet rays during production or use. For this reason, hydrotalcite powder is used as a stabilizer. In addition, layered double hydroxides are used in various catalysts, paints, inks, and the like (see, for example, Patent Document 1).

  On the other hand, in order to enhance the anion exchange function and the like, there is a layered double hydroxide having a crystallite size of 20 nm or less (see, for example, Patent Document 2). If this is used for stabilizers, various catalysts, paints, inks, etc., further improvement of the effect can be expected.

JP2001-164042A International Publication Number WO2005 / 087664

  However, the layered double hydroxide having a crystallite size of 20 nm or less has a problem that crystals are aggregated during the production process and are difficult to disperse finely.

  Accordingly, an object of the present invention is to provide a layered double hydroxide particle group having a small particle size, a production method thereof, a layered double hydroxide dispersion using these, and a layered double hydroxide-added resin.

In order to achieve the above object, the method for producing a layered double hydroxide particle group in the present invention has a general formula of M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (wherein, M ²⁺ is a divalent metal, M ³⁺ is a trivalent metal, a ^n-n-valent anion, 0 <x <1, m > 0) is represented by the average crystal A mixed solution preparation step for preparing a mixed solution containing a group of layered double hydroxide particles composed of layered double hydroxide aggregate particles having a child size of 20 nm or less, and the aggregate particles are centrifuged to obtain a difference in specific gravity And a classification step for reducing the average particle size of the aggregate particles.

In this case, it is preferable that the classifying step lowers the average particle size of the aggregate particles to 20 μm or less by the centrifugal separation. Moreover, after the classification step, the mixed solution containing the layered double hydroxide particle group may be dehydrated and dried. In the classification step, after the aggregate particles are dried, the average particle size of the aggregate particles may be lowered to 20 μm or less by centrifugation. Moreover, it is preferable to have a surface treatment step for coating the surface of the aggregate particles with higher fatty acids. In the mixed solution preparation step, an acidic solution containing aluminum ions and magnesium ions and an alkaline solution containing alkali are mixed, and the general formula is M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ). _{x / n} · mH ₂ O (wherein, M ²⁺ is a divalent metal, M ³⁺ is a trivalent metal, a ^n-n-valent anion, 0 <x <1, m > 0) with After producing the layered double hydroxide represented, the aging of the layered double hydroxide may be stopped within 120 minutes. Furthermore, the layered double hydroxide preferably has an average crystallite size of 10 nm or less.

The layered double hydroxide particles of the present invention have a general formula of M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (where M ²⁺ divalent metal, M ³⁺ is a trivalent metal, a ^n-n-valent anion, 0 <represented by x <1, m> 0), layered double the average crystallite size is 20nm or less It consists of hydroxide aggregate particles, wherein the average particle diameter of the aggregate particles is 20 μm or less.

  In this case, the surface of the aggregate particles is preferably coated with higher fatty acids.

  The layered double hydroxide dispersion of the present invention is characterized in that the layered double hydroxide particles of the present invention described above are dispersed in a liquid.

  Moreover, the layered double hydroxide-added resin of the present invention is characterized by containing the above-described layered double hydroxide particle group of the present invention in the resin.

  According to the present invention, a group of layered double hydroxide particles having a small average particle diameter of aggregate particles can be produced by a simple process. Moreover, a layered double hydroxide dispersion and a layered double hydroxide-added resin can be produced using this layered double hydroxide particle group.

It is a graph which shows the relationship between the particle diameter of the layered double hydroxide particle group which performed wet classification, and relative particle amount (%). It is a graph which shows the relationship between the particle diameter of the layered double hydroxide particle group which performed normal drying, and relative particle amount (%). It is a graph which shows the relationship between the particle diameter of the layered double hydroxide particle group which performed airflow type drying, and relative particle amount (%). It is a graph which shows the relationship between the particle diameter of the layered double hydroxide particle group which performed airflow type drying, and relative particle amount (%). It is a graph which shows the relationship between the particle diameter of the layered double hydroxide particle group which performed the surface treatment by a higher fatty acid, and relative particle amount (%).

  Hereinafter, the layered double hydroxide particles of the present invention and the production method thereof will be described.

  The method for producing a layered double hydroxide particle group of the present invention prepares a mixed solution containing a layered double hydroxide particle group composed of aggregated particles of a layered double hydroxide having an average crystallite size of 20 nm or less. It consists of a mixed solution preparation step, and a classification step of centrifuging the mixed solution to reduce the average particle size of the aggregate particles by utilizing the specific gravity difference.

Here, the layered double hydroxide has a general formula of M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (where M ²⁺ is divalent) metal, M ³⁺ is a trivalent metal, a ^n-means those represented by the n-valent anion, 0 <x <1, m > 0). The average crystallite size means a value obtained by the Scherrer method using an X-ray diffractometer.

  The aggregate particles mean particles formed by agglomerating a plurality of layered double hydroxide crystals. The particle size of the aggregate particles means the particle size of the aggregate particles measured using a laser diffraction / scattering method. For example, the particle diameter measured using the laser diffraction scattering type particle size distribution measuring device (model: LMS-2000e-MU) of Seishin Co., Ltd. can be used. The average particle size means the particle size when the total value of the aggregate volume from the small particle size side reaches 50% of the total.

  The mixed solution preparation step is to prepare a mixed solution of layered double hydroxide and water so that it can be centrifuged in the classification step, but the slurry produced in the process of producing the layered double hydroxide is used as it is. May be.

The layered double hydroxide may be produced by any method. For example, the general formula is Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O (A ^n- is explained below a method for manufacturing the n-valent layered double hydroxide anion, m> 0).

  First, an acidic solution containing aluminum ions and magnesium ions is prepared.

  Any aluminum source may be used as long as it generates aluminum ions in water, and is not limited to a specific substance. For example, alumina, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminum nitrate, bauxite, alumina production residue from bauxite, aluminum sludge and the like can be used. These aluminum sources may be used alone or in combination of two or more.

  The magnesium source of magnesium ions is not limited to a specific substance as long as it is a substance that generates magnesium ions in water. For example, calcite of brucite, magnesium hydroxide, magnesite, magnesite, or the like can be used. Any of these magnesium sources may be used alone or in combination of two or more.

  The aluminum compound as the aluminum source and the magnesium compound as the magnesium source do not need to be completely dissolved if aluminum ions and magnesium ions are present in the acidic solution. Therefore, even if it contains the aluminum compound and magnesium compound which are not melt | dissolved in an acidic solution, a layered double hydroxide can be manufactured without a problem.

The highly crystalline layered double hydroxide represented by the general formula Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O has a molar ratio of aluminum ion to magnesium ion. Is known to be 1: 3 (x = 0.25). Therefore, the molar ratio of aluminum ions to magnesium ions in the acidic solution is preferably in the range of 1: 5 to 1: 2. By setting it as this range, a layered double hydroxide can be produced advantageously in terms of mass balance without wasting the aluminum source and the magnesium source.

  In order to adjust the acidic solution to be acidic, nitric acid or hydrochloric acid is preferably used.

Next, the acidic solution containing aluminum ions and magnesium ions is mixed with an alkaline solution containing alkali. This alkaline solution preferably has a pH of 8-11.
The mixing of the acidic solution and the alkaline solution can be performed by adding the acidic solution to the alkaline solution at once, or by dropping the acidic solution into the alkaline solution. Preferably, depending on the stirring ability at the time of mixing. It is better to mix an appropriate amount of acidic solution and alkaline solution. Of course, other methods may be used as long as the acidic solution and the alkaline solution can be sufficiently stirred.

  Here, the alkali contained in the alkaline solution is not limited to a specific substance as long as the aqueous solution is alkaline. For example, sodium hydroxide or calcium hydroxide can be used. Further, sodium carbonate, potassium carbonate, ammonium carbonate, aqueous ammonia, sodium borate, potassium borate and the like can also be used. Any of these alkalis may be used alone or in combination of two or more.

  In addition, since the highly crystalline layered double hydroxide is preferentially ion-exchanged with carbonate ions, it cannot be efficiently ion-exchanged with the intended anion if carbonate ions are contained. Therefore, in the layered double hydroxide, it is preferable that the acidic solution and the alkaline solution do not contain carbonate ions in order to efficiently exchange ions with the target anions.

  If the aging is not performed after the mixing of the acidic solution and the alkaline solution is completed, the layered compound having a small crystallite size (crystallite size) can be obtained without growing the layered double hydroxide crystal. Hydroxides can be produced. The ripening is preferably stopped as soon as possible so that the crystallite size is 20 nm or less, preferably 10 nm or less.

In order not to perform aging, after the mixing of the acidic solution and the alkaline solution is completed, the pH of the mixed solution may be lowered to a value at which the crystal growth of the layered double hydroxide stops. For example, a layered double hydroxide represented by the general formula Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O is aged when the pH is 9 or less. Can be stopped. In addition, a layered form represented by the general formula Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (A ⁿ⁻ is an n-valent anion, m> 0) The aging of the double hydroxide can be stopped if the pH is 5 or less.

  Moreover, ripening can also be stopped by removing moisture. In order to remove moisture, an appropriate method such as suction filtration or centrifugation can be used.

Therefore, to reduce the crystallite size of the layered double hydroxide represented by the general formula Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O to 20 nm or less The pH of the mixed solution may be adjusted to 9 or less preferably within 120 minutes after the mixing of the acidic solution and the alkaline solution is completed. Any method may be used to adjust the pH to 9 or less. For example, there is a method in which an acidic solution and an alkaline solution are mixed and then immediately diluted with water. Of course, water may be removed by suction filtration, centrifugation, etc. within 120 minutes after mixing the acidic solution and the alkaline solution. In order to prevent the aging from occurring, the layered double hydroxide may be washed immediately after the mixing of the acidic solution and the alkaline solution is completed. The chloride such as NaCl produced in the synthesis process may be washed or contained according to the purpose of use.

  In the classification step, the aggregate particles are centrifuged using the specific gravity difference to lower the average particle diameter of the aggregate particles.

  Centrifugation includes a method of separating the liquid mixture described above by wet classification, and a method of separating the liquid mixture by dry classification after drying the liquid mixture.

  In the case of wet classification, for example, a generally known solid-liquid separator can be used. In the case of dry classification, it is necessary to dry the mixed solution first. Drying may be ordinary drying, but an airflow dryer that is dried with high-speed hot air while reducing the pressure is preferable in that the aggregate particles are refined by a dispersion effect.

  Conventionally, it has been considered preferable that the average particle size of the aggregate particles added to the resin or the like is 2 μm or less. However, in the present application, the average crystallite size of the layered double hydroxide is set to one tenth of that of the conventional layered double hydroxide, thereby increasing the surface area per volume by a factor of ten. Therefore, the average particle diameter of the aggregate particles may be adjusted to 20 μm or less.

  Moreover, you may have the surface treatment process which coat | covers the surface of an aggregate particle with a higher fatty acid further before a classification | category process. The surface of the aggregate particles with the higher fatty acid can be applied by either a dry surface treatment or a wet surface treatment.

  When wet surface treatment is performed, a higher fatty acid salt aqueous solution is added to the dispersion in which aggregate particles are dispersed, and the water temperature is adjusted to 20 to 90 ° C. and mixed and stirred, or if necessary, mixed. By adjusting the pH value after stirring, the particle surfaces of the aggregate particles may be coated with higher fatty acids, and then filtered, washed with water, dried, pulverized, and the like. As the higher fatty acid salt, sodium stearate, sodium laurate, sodium oleate and the like can be used.

  In the case of performing a dry surface treatment, the aggregated particle powder may be put into a Henschel mixer, a sand mill, an edge runner, a Taninaka grinder, a raker, etc., and a higher fatty acid may be added and dry mixed. As the higher fatty acid, stearic acid, lauric acid, oleic acid and the like can be used.

  The addition amount of the higher fatty acid salt or higher fatty acid is 0.2 to 20.0% by weight in terms of C with respect to the layered double hydroxide particle group. When it is less than 0.2% by weight, it is difficult to coat a sufficient amount of higher fatty acid on the particle surface. Moreover, it is because a coating effect will be saturated when it exceeds 20.0 weight%.

  The layered double hydroxide particle group thus prepared may be used as a layered double hydroxide particle dispersion while being dispersed in water, but the mixed liquid containing the layered double hydroxide particle group is dehydrated, It may be dried and powdered. For example, after removing moisture as much as possible by applying a predetermined pressure with a filter press, it may be dried in a drying furnace.

  The layered double hydroxide particles thus produced can be dispersed again in water or other liquids and used as a layered double hydroxide dispersion. It can also be used as a layered double hydroxide-added resin dispersed in a resin such as vinyl chloride, polypropylene, or polyethylene. When dispersed in a resin, it may be directly dispersed in a liquid resin, or a pellet may be once produced and dispersed using the pellet.

  Examples of the layered double hydroxide particle group and the production method thereof according to the present invention will be described below, but the present invention is not limited to these examples.

In the layered double hydroxide, magnesium ion was used as the divalent metal cation, and aluminum ion was used as the trivalent metal cation. The acidic solution was prepared by dissolving 1 mol of magnesium nitrate hexahydrate as a magnesium source and 0.5 mol of aluminum nitrate nonahydrate as an aluminum source in 1 L of distilled water. Further, an alkaline solution was prepared by dissolving 3 mol of sodium hydroxide and 0.25 mol of sodium carbonate in 1 L of distilled water. An acidic solution is added to the alkaline solution so as not to ripen, and the mixture contains a layered double hydroxide represented by the chemical formula [Mg _5.33 Al _2.67 (OH) ₁₆ ] [(CO ₃ ) _1.335 · 4H ₂ O]. A liquid (sample 1) was prepared. When the crystallite size of the layered double hydroxide was determined by the Scherrer method using an X-ray diffractometer, the average crystallite size was 9.1 nm.

  Moreover, the particle size distribution of the sample 1 was measured using the laser diffraction scattering type particle size distribution measuring device (Seishin corporation / model: LMS-2000e-MU). Table 1 shows the results of the relative particle amount (%) relative to the particle diameter and the total volume, and the integrated value (%) of the volume from the small particle diameter side.

  Next, the sample 1 was centrifuged with a solid-liquid separator (CMS Co., Ltd./Solid-liquid separator Rex) to obtain a sample 2. The particle size distribution of Sample 2 was measured using a laser diffraction / scattering particle size distribution analyzer (Seishin Enterprise Co., Ltd./model: LMS-2000e-MU). Table 2 shows the results of the relative particle amount (%) relative to the particle diameter and the total volume, and the integrated value (%) of the volume from the small particle diameter side. A graph showing the particle size distribution of Sample 1 and Sample 2 is shown in FIG.

  Sample 1 has an average particle size of 40.870 μm and a maximum particle size of 741.259 μm, whereas Sample 2 has an average particle size of 14.051 μm and a maximum particle size of 40.870 μm. It can be seen that both the average particle size and the maximum particle size of the group are very small.

  Sample 1 was dried in a normal drying furnace to obtain Sample 3. The particle size distribution of Sample 3 was measured using a laser diffraction / scattering particle size distribution analyzer (Seishin Enterprise Co., Ltd./model: LMS-2000e-MU). Table 3 shows the results of the relative particle amount (%) relative to the particle diameter and the total volume, and the integrated value (%) of the volume from the small particle diameter side. A graph showing the particle size distribution of Sample 3 is shown in FIG.

  Moreover, the sample 1 was dried with the airflow dryer (Hiraiwa Iron Works / Jet dryer, model number: HTD-2022L). The inlet temperature of the air dryer was 240 ° C. and the outlet temperature was 180 ° C. This sample was classified with a dry classifier to obtain Sample 4. Moreover, the gas used for classification was passed through a bag filter and collected to obtain Sample 5. The particle size distribution of Samples 4 and 5 was measured using a laser diffraction / scattering particle size distribution analyzer (Seishin Enterprise Co., Ltd./model: LMS-2000e-MU). Tables 4 and 5 show the results of the relative particle amount (%) relative to the particle diameter and the total volume, and the integrated value (%) of the volume from the small particle diameter side. A graph showing the particle size distribution of sample 4 is shown in FIG. 3, and a graph showing the particle size distribution of sample 5 is shown in FIG.

  Sample 3 has an average particle size of 67.523 μm and a maximum particle size of 344.206 μm, whereas sample 4 has an average particle size of 5.079 μm and a maximum particle size of 36.801 μm. It can be seen that both the average particle size and the maximum particle size are very small. Sample 5 has an average particle size of 2.106 μm and a maximum particle size of 19.018 μm, and it can be seen that both the average particle size and the maximum particle size of the layered double hydroxide particle group are further reduced.

  Further, NaCl or the like was removed by washing with pure water of Sample 1, and surface treatment was performed by adding 1% by weight of potassium oleate thereto. This mixed solution was dried in a normal drying furnace to obtain Sample 6. The particle size distribution of this sample 6 was measured using a laser diffraction scattering type particle size distribution measuring instrument (Seishin Enterprise Co., Ltd./model: LMS-2000e-MU). Table 6 shows the results of the relative particle amount (%) with respect to the particle diameter and the total volume, and the integrated value (%) of the volume from the small particle diameter side. A graph showing the particle size distribution of Sample 6 is shown in FIG.

  Sample 3 has an average particle size of 67.523 μm and a maximum particle size of 344.206 μm, whereas sample 4 has an average particle size of 19.018 μm and a maximum particle size of 213.976 μm. It can be seen that both the average particle size and the maximum particle size are smaller.

Claims (11)

The general formula is M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O (where M ²⁺ is a divalent metal and M ³⁺ is a trivalent metal) A ⁿ⁻ is an n-valent anion, 0 <x <1, m> 0), and a layered double hydroxide comprising aggregated particles of a layered double hydroxide having an average crystallite size of 20 nm or less A liquid mixture preparing step of preparing a liquid mixture containing the particles,
A step of centrifuging the aggregate particles and reducing the average particle size of the aggregate particles using a difference in specific gravity;
A method for producing a layered double hydroxide particle group, comprising:   The method for producing a layered double hydroxide particle group according to claim 1, wherein the classification step lowers the average particle diameter of the aggregate particles to 20 µm or less by centrifuging the mixed solution.   3. The method for producing a layered double hydroxide particle group according to claim 1, wherein after the classification step, the mixed liquid containing the layered double hydroxide particle group is dehydrated and dried.   The method for producing a layered double hydroxide particle group according to claim 1, wherein, in the classification step, after the aggregate particles are dried, the average particle size of the aggregate particles is lowered to 20 µm or less by centrifugation. .   The method for producing a layered double hydroxide particle group according to any one of claims 1 to 4, further comprising a surface treatment step of coating the surface of the aggregate particles with a higher fatty acid. In the mixed solution preparation step, an acidic solution containing aluminum ions and magnesium ions and an alkaline solution containing alkali are mixed, and the general formula is M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{x / n} · mH ₂ O (wherein, M ²⁺ is a divalent metal, M ³⁺ is a trivalent metal, a ^n-n-valent anion, 0 <x <1, m > 0) are represented by 6. The layered double hydroxide according to claim 1, wherein the aging of the layered double hydroxide is stopped within 120 minutes after forming the layered double hydroxide. Production method of particle group.   The method for producing a layered double hydroxide particle group according to any one of claims 1 to 6, wherein the layered double hydroxide has an average crystallite size of 10 nm or less. The general formula is M ²⁺ _1-x M ³⁺ _x (OH) ₂ (A ^n- ) _{x / n} · mH ₂ O (where M ²⁺ is a divalent metal and M ³⁺ is a trivalent metal) A ⁿ⁻ is an n-valent anion, 0 <x <1, m> 0), and a layered double hydroxide comprising aggregated particles of a layered double hydroxide having an average crystallite size of 20 nm or less A group of particles,
A group of layered double hydroxide particles, wherein the aggregate particles have an average particle size of 20 μm or less.   The layered double hydroxide particle group according to claim 8, wherein the surface of the aggregate particles is coated with a higher fatty acid.   A layered double hydroxide dispersion liquid, wherein the layered double hydroxide particle group according to claim 8 or 9 is dispersed in a liquid.   A layered double hydroxide-added resin comprising the layered double hydroxide particle group according to claim 8 or 9 in a resin.

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