KR101228880B1 - Hydrotalcite with extremely low content of sodium, process for preparing it and synthetic resin composition comprising it - Google Patents

Abstract

The present invention discloses a hydrotalcite having a characteristic and having a very low content of sodium, a method for preparing the same, and a synthetic resin composition hydrotalcite containing the same.
(1) general formula
[( Mg) _y (Zn) _z ] _1-x (Al) _x (OH) ₂ (CO ₃ ^2- ) _{x /} 2mH ₂ O
In the formula, x, y, z and m are values satisfying the following conditions.
0.2 ≦ x <0.4, y + z = 1, 0.7 ≦ y ≦ 1, 0 ≦ z ≦ 0.3, 0 ≦ m <1;
(2) the hydrotalcite particles have an average secondary particle diameter of 0.5 to 2 탆 as measured by laser diffraction scattering;
(3) The sodium component in the hydrotalcite particles is 80 ppm by weight or less.
(4) The hydrotalcite particles contain iron compounds and manganese compounds in a total amount of 0.005 wt% or less in terms of metal (Fe + Mn).
(5) The hydrotalcite particles have a specific surface area of 5 to 40 m 2 / g, preferably 5 to 20 m 2 / g as measured by the BET method.

Description

HYDROTALCITE WITH EXTREMELY LOW CONTENT OF SODIUM, PROCESS FOR PREPARING IT AND SYNTHETIC RESIN COMPOSITION COMPRISING IT}

The present invention relates to hydrotalcite particles in which the content of sodium is controlled in an extremely small amount, a method for preparing the same, a resin composition containing the same, and a molded article. More specifically, hydrotalcite has excellent thermal deterioration performance during the heat molding processing of synthetic resin, has excellent physical properties such as high dispersibility, non-aggregation resistance, and impact resistance to resins, and especially has new properties without containing sodium ions. And a method for producing the same, a resin composition containing the same, and a molded article.

Conventionally, an olefin-based polymer or copolymer prepared using a Ziegler-type polymerization catalyst using a halogen-containing compound as a catalyst and / or carrier component, or an olefin-containing olefin containing a catalyst for polymerization or post-chlorinated halogenation such as chlorinated polyethylene or the like. Hydrotalcite has been used for a long time to prevent thermal deterioration due to halogen compounds contained in resins produced by polyolefins and blend resins thereof (see, for example, Patent Documents 1 to 9 and the like).

In the above patent documents, a water-soluble metal compound was used to prepare hydrotalcite. However, in the preparation of these compounds, it has to be washed several times to remove the sodium (Na) component and hydro by-products contained in hydrotalcite. Due to the large amount of wastewater and by-products generated in this way, productivity is reduced, manufacturing costs are increased, and the environment is deteriorated. In order to solve this problem, a technique of using a crystalline metal hydroxide as a starting material in which the generation of by-products is suppressed has been proposed (see Patent Documents 1 and 2, etc.), but these methods have low reactivity and crystalline hydroxide. In order to solve this problem, a water-soluble compound was added, or an additive was used to adjust pH. These methods can reduce some of the generation of by-products and wastewater, but when using a high basic and high acidic pH, unreacted products are more likely to occur due to the dissolution of the product, and the particles are reaggregated into particles having a low particle size of 0.1 μm. The degree of borrowing may increase, and the initial thermal stability performance of the synthetic resin may be lowered due to irregular and large particle sizes, and thus the invention disclosed in the patent document is not very satisfactory for practical application.

In addition, when hydrotalcite is blended into halogen-containing polyolefins such as vinyl chloride resin, when the secondary average particle of the particles is large or the specific surface area is small, the dispersibility with the resin is not good, and the iron and manganese In the case where the same heavy metal is contained, it is disclosed to adversely affect the thermal deterioration resistance (Patent Document 3).

In addition, when the Na content in the hydrotalcite exceeds 100 ppm, when it is blended in a resin, in particular, a vinyl chloride resin, the electrical resistance decreases, the resin stability against heat and ultraviolet rays is poor, and the resin deteriorates during extrusion. It is known that there is a problem that occurs such as yellowing caused by a large amount of residue (reference: Patent Document 4). For this reason, hydrotalcite is washed with a large amount of water in order to remove salts such as sodium chloride, but since the solubility of the salt in water is not so great, a large amount of water (solvent) must be used. It is a phenomenon that the washing | cleaning process also needs to wash several times.

Patent Document 1: Patent Registration Publication 10-0388097

Patent Document 2: Patent Registration Publication No. 10-0486669

Patent Document 3: WO99 / 01509

Patent Document 4: WO2006 / 043352

Patent Literature 5: Japanese Special Forces 46-2280

Patent Literature 6: Japanese Special Forces 47-32198

Patent Literature 7: Japanese Special Employment Office 50-30039

Patent Literature 8: Japanese Special Forces 48-29477

Patent Document 9: Japanese Patent Application No. 51-29129

The inventors of the present invention overcome the many technical problems described above, and also use a small amount to prevent problems of excellent thermal deterioration or colorability, and also improve resin stability against heat or ultraviolet rays, and deteriorate resin during extrusion. In the preparation of hydrotalcite in order to suppress the occurrence of yellowing, etc., a crystalline inorganic metal compound is used as a starting material, and the compound is converted into fine particles through a wet or dry grinding process for controlling the reactivity and particle size. By using carbon dioxide (CO ₂ ) gas as an anion source and preventing the sodium ions incorporated into the final product in advance by using the alkali metal compound of carbonate, there is no by-product generation, the production cost is low, Remove hydrotalcite with uniform and small secondary particle size It has been found that the present invention can be completed and the present invention has been completed.

According to the present invention, no by-products are produced during production of the product, and manufacturing cost is low, uniformity, and hydrotalcite having a small secondary particle size can be produced. Excellent performance, excellent physical properties such as high dispersibility, non-aggregation, impact resistance to the resin, in particular, containing less than 80ppm sodium ions to suppress the coloration of the resin in the extrusion process, it is possible to suppress the occurrence of debris have.

Hereinafter, the present invention will be described in detail.

The hydrotalcite produced by the present invention has the following characteristics.

(1) General formula

[( Mg) _y (Zn) _z ] _1-x (Al) _x (OH) ₂ (CO ₃ ^2- ) _{x /} 2mH ₂ O

Food,

x, y, z and m are values satisfying the following conditions.

0.2 ≦ x <0.4, y + z = 1, 0.7 ≦ y ≦ 1, 0 ≦ z ≦ 0.3, 0 ≦ m <1;

(2) the hydrotalcite particles have an average secondary particle diameter of 0.5 to 2 탆 as measured by laser diffraction scattering;

(3) The sodium component in the hydrotalcite particles is 80 ppm by weight or less.

(4) The hydrotalcite particles contain iron compounds and manganese compounds in a total amount of 0.005 wt% or less in terms of metal (Fe + Mn).

(5) The hydrotalcite particles have a specific surface area of 5 to 40 m 2 / g, preferably 5 to 20 m 2 / g as measured by the BET method.

Hydrotalcite which does not contain sodium, iron, and manganese components of the present invention, M (II), which is a divalent metal, uses an oxide or hydroxide of magnesium, zinc, calcium, lithium metal, and preferably a metal oxide. It is to manufacture. M (III), a trivalent metal, represents an oxide or hydroxide of Al, with aluminum hydroxide being particularly preferred. These raw metal salts each use a purity of 99.9% or more. If impurities are mixed in the raw materials, impurities are included in the hydrotalcite obtained, and thus, in order to remove these impurities, especially sodium, iron, and manganese, no separate process or washing with water is required. Generated and not preferred. In the present invention, unlike the conventional art, only oxides and / or hydroxides of the metals are used, and sulfates are not used. When using sulfates, i.e. aluminum sulfate or magnesium sulfate, these sulfate compounds are preferable in terms of reactivity due to their good solubility in water, but in order to remove dissolved sulfuric acid groups (SO ₄ ^-2 ) after the reaction, alkali hydroxides or carbonic acid are used. The present invention does not use these sulphate metal compounds because they have to be neutralized with alkalis such as caustic soda or sodium carbonate and washed several times to remove the sodium component after neutralization.

A high purity raw material as described above is prepared, and the divalent metal and trivalent metal raw material thus prepared are dispersed. The mixing ratio for the reaction of the raw metals follows the conventional method. In other words, Japanese Special Forces 46-2280, Japanese Special Forces 47-32198, Japanese Special Forces 50-30039, Japanese Special Forces 48-29477, and Japanese Special Forces Mixing for reaction is carried out according to the method described in 51-29129 and the like. These mixed raw materials are ground using a dry or wet mill. Although it does not specifically limit as a kind of grinder, A wet mill is preferable. In the case of grinding using a wet mill, the rotation speed, time, and slurry concentration of the wet are not particularly limited, and milling is performed until the secondary particle diameter after grinding, D100, is 2 µm or less, preferably 1 µm or less. It is advantageous to adjust the particle size of the hydrotalcite obtained as the final object. If the secondary particle diameter after crushing, D100 is 4 μm or more, problems such as the secondary particle diameter of the hydrotalcite finally obtained, D100 of 10 μm or more may occur, resulting in a decrease in dispersibility when blended with the resin. .

The mixed aqueous solution pulverized in the above is put in a reaction tank, sealed, and then carbon dioxide gas is injected. The injection amount depends on the molar ratio of CO ₃ ^{2 −} by the conventional method, and the amount of CO ₂ equivalent to the molar ratio of CO ₃ ^{2 −} is measured using a high pressure vessel. The feeding method is injected into the closed high pressure reactor containing the reactant under stirring until the gas pressure reaches 0 kg / cm 2.

In the present invention, as described above, as described above, hydrotalcite containing divalent carbonate anion is produced using carbon dioxide gas, and other anions such as divalent ions such as sulfate ion, nitrate ion and chlorine ion are used. It is not intended to produce hydrotalcites with anions. When preparing hydrotalcites having divalent anions such as sulfate ions, nitrates and chlorine ions, sulfates, nitrates, hydrochloride compounds should be used, and when these salts are used, due to the alkali metals that form these salts In order to remove by-products, sodium components, etc., the process of washing | cleaning several times cannot be avoided, and it does not contain the above-mentioned anion, and is limited to anion divalent carbonate using carbon dioxide gas.

After the injection of carbon dioxide gas is completed, the hydrotalcite may be prepared by conventional hydrothermal synthesis of the mixed aqueous solution. For example, hydrotalcites obtained according to the method described above can be obtained by heating in an aqueous medium for about 5 to 30 hours at a temperature of about 150 ° C. or higher, such as about 150 to 250 in an autoclave. have. The heat treatment may be hydrothermal treatment under pressurized conditions until the above-described BET specific surface area condition is satisfied, and it is more preferable to employ a high temperature side rather than a low temperature side.

The hydrotalcites obtained in this way can be used by surface treatment with conventional methods in the art, for example, alkylalkyl sulfonic acid alkali metal salts such as stearic acid and oleic acid alkali metal salts, surfactants and the like.

The hydrotalcite in the slurry form obtained above is filtered, dried, and then ground. Such a process is a method known in the art, specifically, for example, drying at about 95 to 120 ° C. for about 5 to 24 hours, and grinding into a hammer mill.

Hereinafter, the resin composition containing the hydrotalcite of the present invention described above will be described.

In the practice of the present invention, about 0.001 to 30 parts by weight of the specific hydrotalcite, preferably about 0.001 to 20 parts by weight, and more preferably about 0.001 to 10 parts by weight of the specific hydrotalcite to halogen-containing polyolefins such as vinyl chloride resin. What is necessary is just to mix | blend and can provide the composition of this invention in this way.

There is no restriction | limiting in particular in the said mixing means itself, For example, the same mixing means as the usual means which mix | blends a stabilizer, a filler, etc. with these resin can be used. For example, a means, such as a ribbon blender, a gosol mixer corridor, a pelletizer, a mixing roll, an extruder, an intensive mixer, can be illustrated.

In the practice of the present invention, other additives conventionally used may be blended with the polyolefins in addition to the blending of the specific hydrotalcites. Examples of such additives include, for example, 2,6-di-t-butyl-p-cresol, 2,5-di-t-butylhydroquinone, 2,2'-methylene-bis (4-methyl-6- t-butylphenol), 4,4'-thiobis- (6-t-butylphenol), 4,4'-thiobis- (6-t-butyl-m-cresol), octadecyl 3- (3 ' Antioxidants such as 5'-di-t-butyl-4'-hydroxyphenyl) propionate; For example, ultraviolet light such as 2-hydroxy-4-octoxybenzophenone, 2 (2'-hydroxy-5-methylphenyl) benzotriazole, ethyl-2-cyano-3,3-diphenylacrylate Absorbents; Antistatic agents such as, for example, pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbowax; Lubricants such as calcium stearate, zinc stearate, butyl stearate and ethylene bis stearamide; For example, plasticizers, such as dimethyl phthalate, diethyl phthalate, an oleic acid ester, a phosphate ester, a wax, a liquid paraffin; For example, coloring agents, such as carbon black, a phthalocyanine, a quinacridone, an indoline, an azo pigment, titanium oxide, and bengal; For example, fillers, such as asbestos, glass fiber, talc, mica, ballastonite, calcium silicate, aluminum silicate, calcium carbonate; And the like. The compounding quantity of these additives can be selected suitably, for example, about 0.01 to about 1.0% of antioxidants, about 0.01 to about 1.0% of ultraviolet absorbers, and about 0.01 to about 1%, based on the weight of the halogen-containing polyolefin. Examples of the compounding amount, such as antistatic agents, about 0.1 to about 5% lubricants, about 0.1 to about 50% fillers.

Example

Hereinafter, the present invention will be described in more detail with examples and comparative examples. Magnesium sulfate heptahydrate, sodium hydroxide, sodium carbonate were also compared with the hydrotalcite of the Example of this invention using the thing of high purity, ie, 99.9% or more.

Example 1

2 L of distilled water was put into the 3 L raw material tank 1, and 0.903 mol of magnesium oxide and 0.42 mol of aluminum hydroxide were slowly disperse | distributed. The secondary particle diameter of the mixed aqueous solution pulverized by mixing the mixed aqueous solution (A) with a wet mill (wet mill, bead mill from Netzsch, 0.1 mm, SUS304) at 3000 rpm for 60 minutes was D50 0.75 μm / D100 1 μm. It was made. 2L of the pulverized mixed aqueous solution (B) was placed in a 3L reaction tank and sealed, and 0.21 mol of CO ₂ was quantitatively weighed in a high pressure vessel, and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / cm 2. . The mixed aqueous solution (C) in which CO ₂ injection was completed was hydrothermally synthesized at 170 ° C. for 6 hours. Thereafter, the slurry obtained by cooling was transferred to a 3L surface treatment tank and maintained at 80 ° C., and then 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried at 105 ° C. for 12 hours using a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

To do this, analyzing the obtained hydrotalcite-bar, its structural formula is Mg _0.68 Al _0.32 (OH) was _{2 (CO 2) 0.16 · 0.55} H 2 O, was the Na content was 3ppm, the specific surface area of the hydrotalcite obtained is 12m ² / g, and the secondary particle size was D50 1.95 µm / D100 6 µm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Comparative Example 1

A secondary particle diameter of the mixed aqueous solution pulverized by performing a wet mill operation at 3000 rpm for 30 minutes by preparing and mixing the same raw materials and amounts as in Example 1 was D50 1.2 μm / D100 4 μm. 2 L of the pulverized mixed aqueous solution was placed in a reaction tank (7) and sealed, followed by CO ₂ injection and reaction / maturation / surface treatment / drying / milling to prepare hydrotalcite.

The manufacturing process result of analyzing the obtained hydrotalcite, was his general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O, Na content was 3ppm, the specific surface area was 11m ² / g , Secondary particle size was confirmed that the D50 2.19㎛ / D100 10㎛.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Comparative Example 2

The same raw materials and amounts as in Example 1 were prepared and mixed to perform a wet mill operation at 3000 rpm for 10 minutes so that the secondary particle diameter of the pulverized mixed aqueous solution was D50 2.7 μm / D100 12 μm. 2 L of the pulverized mixed aqueous solution was placed in a reaction tank and sealed, and hydrotalcite was prepared by CO ₂ injection and reaction / maturation / surface treatment / drying / milling.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O was, was the Na content was 3ppm, were a specific surface area of 9m ² / g, ² The particle size was confirmed to be D50 2.62 µm / D100 18 µm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Example 2

2L of distilled water was put into the 3L raw material tank 1, and 0.42mol of 0.861mol of magnesium oxide and aluminum hydroxide were slowly dispersed. The mixed aqueous solution (A) was pulverized at 3000 rpm for 60 minutes using a wet mill, so that the secondary particle diameter of the mixed aqueous solution was D50 0.75 µm / D100 1 µm. 2L of the pulverized mixed aqueous solution (B) was put in a reaction tank, sealed, and weighed 0.21 mol of CO _{2 in a} high pressure vessel, and then 2.1 mol of CO ₂ was added to the reaction tank containing the reactant under pressure to '0 kg / ㎠'. Inject until. The mixed aqueous solution (C) in which CO ₂ injection was completed was hydrothermally synthesized at 170 ° C. for 6 hours. Thereafter, the slurry obtained by cooling was transferred to a 3L surface treatment tank and maintained at 80 ° C., and then 20 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried at 105 ° C. for 12 hours or more using a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.67 Al 0.33 (OH) 2} (CO 2) 0.17 · 0.49H 2 O was, was the Na content was 3ppm, were a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 1.97 µm / D100 6 µm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Example 3

2L of distilled water was put into the 3L raw material tank 1, and 0.42mol of 0.945mol of magnesium oxide and aluminum hydroxide were slowly disperse | distributed. The mixed aqueous solution (A) was pulverized at 3000 rpm for 60 minutes using a wet mill so that the secondary particle diameter of the mixed aqueous solution was D50 0.75 μm / D100 1 μm. 2L of the pulverized mixed aqueous solution (B) was put in a reaction tank, sealed, and weighed 0.21 mol of CO _{2 in a} high pressure vessel, and then 2.1 mol of CO ₂ was added to the reaction tank containing the reactant under pressure to '0 kg / ㎠'. Inject until. The mixed aqueous solution (C) in which CO ₂ injection was completed was hydrothermally synthesized at 170 ° C. for 6 hours. Thereafter, the slurry obtained by cooling was transferred to a 3L surface treatment tank and maintained at 80 ° C., and then 20 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried at 105 ° C. for 12 hours or more using a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.69 Al 0.31 (OH) 2} (CO 2) 0.15 · 0.54H 2 O was, was the Na content was 3ppm, were a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 1.89 µm / D100 6 µm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 104 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Example 4

2 L of distilled water was added to the 3 L raw material tank 1, 0.903 mol of magnesium oxide and 0.42 mol of aluminum hydroxide were slowly dispersed, and the resulting mixed aqueous solution (A) was pulverized at 3000 rpm for 60 minutes using a wet mill. The particle diameter was D50 0.75 µm / D100 1 µm. 2L of the pulverized mixed aqueous solution (B) was placed in a 3L reaction tank and sealed, and then 0.21 mol of CO ₂ was quantitatively weighed in a high pressure vessel and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / ㎠. do. Thereafter, hydrotalcite was prepared by aging / coating / drying / milling in the same manner as in Example 1.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) and _0.16 · 0.55H ₂ O, Na content of 40ppm were were, a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 1.97 µm / D100 6 µm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, the Na content of aluminum hydroxide was 117 ppm, and the Fe content was 5 ppm.

Example 5

2 L of distilled water was put into the 3 L raw material tank 1, and 0.903 mol of magnesium oxide and 0.42 mol of aluminum hydroxide were slowly disperse | distributed. It was confirmed that the secondary particle diameter of the mixed aqueous solution pulverized by pulverizing the mixed aqueous solution (A) at 3000 rpm for 60 minutes using a wet mill was D50 0.75 μm / D100 1 μm. 2L of the pulverized mixed aqueous solution (B) was placed in a 3L reaction tank and sealed, and then 0.21 mol of CO ₂ was quantitatively weighed in a high pressure container and injected into the reaction tank containing the reactant under stirring until the pressure reached 0 kg / cm 2. It was. Thereafter, hydrotalcite was prepared by aging / coating / drying / milling in the same manner as in Example 1.

It was the result of analyzing the obtained hydrotalcite in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · was 0.55H ₂ O, Na content was 48 ppm, the specific surface area is 12m ² / g, It was confirmed that the secondary particle diameter was D50 2.01 μm / D100 8 μm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, the Na content of aluminum hydroxide was 240 ppm, and the Fe content was 5 ppm.

Comparative Example 3

2 L of distilled water was put into the 3 L raw material tank 1, and 0.903 mol of magnesium oxide and 0.42 mol of aluminum hydroxide were slowly dispersed. The obtained mixed aqueous solution (A) is pulverized at 3000 rpm for 60 minutes using a wet mill. The secondary particle diameter of the pulverized mixed aqueous solution was D50 0.75 μm / D100 1 μm. 2L of the pulverized mixed aqueous solution (B) was placed in a 3L reaction tank and sealed, and then 0.21 mol of CO ₂ was quantitatively weighed in a high-pressure container and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / ㎠. do. Thereafter, hydrotalcite was prepared by aging / coating / drying / milling in the same manner as in Example 1.

Analysis of the hydrotalcite obtained above was his general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O, Na content was 200p pm, specific surface area was 12m ² / g, It was confirmed that the secondary particle diameter was D50 2.08 μm / D100 8 μm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, the Na content of aluminum hydroxide was 609 ppm, and the Fe content was 5 ppm.

Example 6

20 L of distilled water was put into the 3 L raw material tank 1, 6.93 mol of magnesium oxide, 2.1 mol of zinc oxide, and 4.2 mol of aluminum hydroxide were slowly added to disperse. The mixed aqueous solution (A) was pulverized at 3000 rpm for 60 minutes using a wet mill. The secondary particle diameter of the pulverized mixed aqueous solution was 0.75 μm / 1 μm. 2L of the pulverized mixed aqueous solution (B) was placed in a reaction tank, sealed, and 0.21 mol of CO ₂ was quantitatively weighed in a high-pressure container and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / cm 2. . The mixed aqueous solution (C) in which CO ₂ injection was completed was hydrothermally synthesized at 170 ° C. for 6 hours. After cooling, the slurry obtained by cooling was transferred to a 3L surface treatment tank, and maintained at 80 ° C. Then, 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried with a hot air dryer for 12 hours at 105 ° C., and then pulverized with a hammer mill to prepare hydrotalcite.

And the result of analyzing the obtained hydrotalcite in the above, whose general formula _{Mg 0.52 Zn 0.16 Al 0.32 (OH} ) 2 (CO 2) 0.16 · 0.55H 2 O, Na content was 3ppm, the specific surface area was 11m ² / g , Secondary particle size was confirmed that the D50 1.72㎛ / D100 6㎛.

The magnesium content of magnesium oxide used above was 3 ppm, the Fe content was 147 ppm, the zinc oxide Na content was 3 ppm, the Fe content was 5 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Example 7

20L of distilled water was put into the 3L raw material tank 1, and 6.93mol of magnesium oxide, 2.1mol of calcium oxide, and 4.2mol of aluminum hydroxide were slowly dispersed. The mixed aqueous solution (A) was pulverized at 3000 rpm for 60 minutes using a wet mill. The secondary particle diameter of the pulverized mixed aqueous solution was 0.75 μm / 1 μm. 2L of the pulverized mixed aqueous solution (B) was placed in a reaction tank, sealed, and 0.21 mol of CO ₂ was quantitatively weighed in a high-pressure container and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / cm 2. . The mixed aqueous solution (C) in which CO ₂ injection was completed was hydrothermally synthesized at 170 ° C. for 6 hours. After cooling, the slurry obtained by cooling was transferred to a 3L surface treatment tank, and maintained at 80 ° C. Then, 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried with a hot air dryer for 12 hours at 105 ° C., and then pulverized with a hammer mill to prepare hydrotalcite.

The manufacturing process result of analyzing the obtained hydrotalcite, and his general formula _{Mg 0.52 Ca 0.16 Al 0.32 (OH} ) 2 (CO 2) 0.16 · 0.55H 2 O, Na content was 3ppm, a specific surface area of 11m ² / g, and the secondary particle size was D50 1.82 μm / D100 6 μm.

The magnesium content of magnesium oxide used was 3 ppm, the Fe content was 141 ppm, the zinc oxide Na content was 3 ppm, the Fe content was 5 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Example 8

20 L of distilled water was put into the 3 L raw material tank 1, and 6.93 mol of magnesium oxide, 2.1 mol of lithium oxide, and 4.2 mol of aluminum hydroxide were slowly dispersed. The mixed aqueous solution (A) is pulverized at 3000 rpm for 60 minutes using a wet mill. The secondary particle diameter of the pulverized mixed aqueous solution was 0.75 μm / 1 μm. 2L of the pulverized mixed aqueous solution (B) was placed in a reaction tank, sealed, and 0.21 mol of CO ₂ was quantitatively weighed in a high-pressure container and injected into the reaction tank containing the reactant under stirring until the pressure was 0 kg / cm 2. . The mixed aqueous solution (C) in which the CO ₂ injection was completed is hydrothermally synthesized at 170 ° C. for 6 hours. After cooling, the slurry obtained by cooling was transferred to a 3L surface treatment tank and maintained at 80 ° C., and then 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried with a hot air dryer for 12 hours at 105 ° C., and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcite obtained above was his general formula _{Mg 0.52 Li 0.16 Al 0.32 (OH} ) 2 (CO 2) 0.16 · 0.55H 2 O, Na content was 3ppm, the specific surface area was 12m ² / g , The secondary particle diameter was confirmed that the D50 1.92㎛ / D100 6㎛.

The magnesium content of magnesium oxide used was 3 ppm, the Fe content was 132 ppm, the zinc oxide Na content was 3 ppm, the Fe content was 5 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Comparative Example 4

The same raw material as in Example (1) was added at the same concentration ratio, 2L of the mixed aqueous solution, which had not been subjected to the wet mill operation, was placed in a reaction tank and sealed, and then 2.1 mol of CO ₂ was injected until the pressure was 0 kg / cm 2. It was. The mixed aqueous solution of CO ₂ injection completed is hydrothermally synthesized at 170 ° C. for 6 hours. After cooling, the slurry obtained by cooling was transferred to a 3L surface treatment tank, and maintained at 80 ° C. Then, 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the solid material obtained by filtering the slurry at a water content of 70% was dried at 105 ° C. for 12 hours or more using a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H ₂ O was, was the Na content was 3ppm, 2 primary particle diameter D50 2.84㎛ / D100 18 It confirmed that it was μm.

The Na content of magnesium oxide used above was 5 ppm, the Fe content was 106 ppm, and the Na and Fe contents of aluminum hydroxide were 5 ppm, respectively.

Comparative Example 5

0.5 L of distilled water was put into the 2 L raw material tank 1, and 0.903 mol of magnesium oxide was slowly disperse | distributed. Subsequently, aluminum sulfate was prepared in the 2 L raw material tank 2 so that it might be set to 0.42 mol / L. Thereafter, 0.5L of an aqueous solution of Mg and an aqueous solution of Al were added to the 3L mixing tank 1 while stirring at the same ratio, thereby preparing 1L of the mixed aqueous solution (A). 0.5L of distilled water was added to the 2L raw material tank 3, 0.84mol of caustic soda was added to dissolve, 0.5L of distilled water was added to the 2L raw material tank 4, and 0.21mol of sodium carbonate was dissolved. An aqueous solution of caustic soda and an aqueous solution of sodium carbonate were added to the mixing tank 2 during stirring to prepare a mixed aqueous solution (B). The mixed aqueous solution (A) is taken into the reaction tank (7), and then the mixed aqueous solution (B) is gradually introduced into the reaction tank (7) while stirring. After completion of the addition, the reaction tank was hydrothermally synthesized at 170 ° C. for 6 hours. Thereafter, the slurry obtained by cooling was transferred to the surface treatment tank 8, and maintained at 80 ° C. Then, 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the slurry was filtered at a water content of 70%, and the solid material obtained was dispersed in one-fold water compared to the reactants, and then filtered. The washing operation was repeated one more time, washed with a hot air dryer for 12 hours at 105 ° C., and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H2O was was, Na content of 720ppm, were a specific surface area of 12m ² / g, ² primary particle size It confirmed that it was D50 7.42 micrometer / D100 45 micrometer.

The Na content of magnesium oxide used above was 1 ppm, the Fe content was 64 ppm, the Na content of aluminum sulfate was 1, the Fe content was 5 ppm, and the Fe content of caustic soda and sodium carbonate was 5 ppm, respectively.

Comparative Example 6

After hydrothermally synthesizing with the same raw materials and concentrations as in Comparative Example 5, the surface treatment was completed in the same manner. Thereafter, the slurry is filtered at a water content of 70%, and the solid material obtained is dispersed in one-fold water compared to the reactants and then filtered. The washing operation was repeated two more times, dried at 105 ° C. for 12 hours with a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

The manufacturing process result of analyzing the obtained hydrotalcite, whose general formula was _{1 Mg 0.68 Al 0.32 (OH)} 2 (CO 2) 0.16 · 0.55H 2 O, Na content of 260ppm, the specific surface area was 12m ² / g It was confirmed that the secondary particle diameter was D50 4.18 μm / D100 36 μm.

Comparative Example 7

After hydrothermally synthesizing with the same raw materials and concentrations as in Comparative Example 5, the surface treatment was completed in the same manner. Thereafter, the slurry was filtered at a water content of 70%, and the solid material obtained was dispersed in one-fold water compared to the reactants and then filtered. The washing operation was washed three more times, dried at 105 ° C. for 12 hours with a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O was, was was Na content of 110ppm, a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 2.93 µm / D100 30 µm.

Comparative Example 8

Magnesium sulfate was prepared in the 2 L raw material tank 1 to be 1.806 mol / L. Subsequently, aluminum sulfate was prepared in the 2 L raw material tank 2 so that it might be set to 0.42 mol / L. Thereafter, 0.5 L of the Mg aqueous solution and the Al aqueous solution were added to the 3 L mixing tank 1 at the same ratio, respectively, during stirring to prepare 1 L of the mixed aqueous solution (A). Subsequently, 0.5 L of distilled water is added to the 2 L raw material tank 3, 2.016 mol of caustic soda is added and dissolved. Subsequently, 0.5L of distilled water is put into a 2L raw material tank 4, 0.21mol of sodium carbonate is added, and it melt | dissolves. An aqueous solution of caustic soda and an aqueous solution of sodium carbonate were added to the mixing tank 2 during stirring to prepare a mixed aqueous solution (B). The mixed aqueous solution (A) was placed in the reaction tank (7), and then the mixed aqueous solution (B) was slowly introduced into the reaction tank (7) during stirring. After completion of the addition, the reaction tank was hydrothermally synthesized at 170 ° C. for 6 hours. Thereafter, the slurry obtained by cooling was transferred to the surface treatment tank 8, and the temperature was maintained at 80 ° C., and then 3 g of stearic acid was added while stirring, followed by stirring for 1 hour to complete the surface treatment. Thereafter, the slurry is filtered at a water content of 70%, and the solid material obtained is dispersed in one-fold water compared to the reactants and then filtered. The washing operation was repeated one more time, washed, dried at 105 ° C. for 12 hours with a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O was, was was Na content of 930ppm, a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 8.29 µm / D100 45 µm. The Na content of magnesium oxide used was 0 ppm, the Fe content was 9 ppm, the Na content of aluminum sulfate was 1 ppm, the Fe content was 5 ppm, the Fe content of caustic soda was 6 ppm, and the Fe content of sodium carbonate was 5 ppm.

Comparative Example 9

Hydrothermal synthesis was carried out using the same raw materials and concentrations as in Comparative Example 8, followed by surface treatment in the same manner. Thereafter, the slurry is filtered at a water content of 70%, and the solid material obtained is dispersed in one-fold water compared to the reactants and then filtered. The washing operation was repeated two more times, dried at 105 ° C. for 12 hours using a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O was, was was Na content of 380ppm, a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 5.74 µm / D100 36 µm.

Comparative Example 10

Hydrothermal synthesis was carried out using the same raw materials and concentrations as in Comparative Example 8, followed by surface treatment in the same manner. Thereafter, the slurry was filtered at a water content of 70%, and the solid material obtained was dispersed in one-fold water compared to the reactants, and then filtered. The washing operation was washed three more times, dried at 105 ° C. for 12 hours with a hot air dryer, and then pulverized with a hammer mill to prepare hydrotalcite.

Analysis of the hydrotalcites obtained in the above, whose general formula _{Mg 0.68 Al 0.32 (OH) 2} (CO 2) 0.16 · 0.55H 2 O was, was was Na content of 230ppm, a specific surface area of 12m ² / g, ² The particle size was confirmed to be D50 3.53 μm / D100 36 μm.

Test Example

Impurity Content Analysis:

1 g of the hydrotalcite prepared in Example 1 was collected and placed in a separate flask containing 50 ml of distilled water and diethyl ether each containing no impurities, 15 ml of 1: 1 hydrochloric acid was added, and then all the samples were dissolved. After mixing, the inorganic layer dissolved in water was separated and filtered, heated in a 60 ° C. water bath for 2 hours, transferred to a 100 ml round bottom flask and filled with 100 ml with distilled water, followed by atomic absorption spectrophotometer with Na, Ca, Fe, Mn, Cu, Impurity contents such as Ni, Co, V, and Cr were measured in ppm.

The hydrotalcites of Examples 2 to 8 and Comparative Examples 1 to 10 were also measured for impurity content in the same manner.

Specific surface area measurement:

BET measurement method (KS A 0094) using the degree of adsorption of nitrogen is used as the test method.

Secondary particle size:

The secondary particle diameters of D50 and D100 were measured using a particle size analyzer (Particle size analyzer, Cilas, 1180) using a laser diffraction scattering method using 0.05 g of hydrotalcite prepared in Example 1 as a sample.

The hydrotalcites of Examples 2 to 8 and Comparative Examples 1 to 10 were also measured in the secondary particle diameter in the same manner.

The hydrotalcites obtained in the above examples and comparative examples were analyzed, and the results are summarized in Table 1 below.

Note: Specific surface area values are BET specific surface area measurements by KS A 0094 method.

From the above analysis results, when comparing the hydrotalcite of Examples 1 to 6 and the hydrotalcite of Comparative Examples 1 and 2, the same bivalent value in the preparation of the hydrotalcite of Example 1 and the hydrotalcite of Comparative Examples 1 and 2 was observed. By using raw materials of metal oxide and trivalent hydroxide, Na content was only detected at 3 ppm. This indicates that there is no incorporation other than Na impurities by the raw material. However, in these comparative examples, since hydrotalcite was prepared by shortening the grinding time by 1/2 or 1/6 of the raw materials, the secondary particles D50 and D100 had a particle size of the hydrotalcite of Example. In comparison, it indicates that the dispersibility becomes worse.

In Examples 4 to 5, the Na content having a particle size in the same range as in Example 1 was prepared by the same procedure as in Example 3 using a raw material having a high Na content of aluminum hydroxide as a raw material when producing hydrotalcite. Hydrotalcite, from 40 to 200 ppm, was prepared. Na content is mixing of Na impurity by a raw material, and shows that there is no other mixing.

That is, the hydrotalcite prepared in Examples 1 to 9, as can be seen from the above analysis results, through the wet mill operation of the raw material, the primary particle size of the product is 0.5㎛ or less, the secondary particle size is less than 2㎛ at D50, It can be seen that the product can be manufactured in which D100 is 10 µm or less and in which Na other than Na impurities by the raw material is not mixed.

In addition, the analysis results of the hydrotalcite of Example 1 and Comparative Examples 4 to 10 are shown in Table 2 below.

Note: Specific surface area values are BET specific surface area measurements by KS A 0094 method.

In Comparative Example 4, the same raw material as in Example 1 was reacted at the same ratio, but hydrotalcite was prepared without a wet mill process. As a result, the secondary particle diameters of the hydrotalcite at D50 and D100 were 2.84 μm and 18 μm. The dispersibility becomes poor, indicating that the resin is poor in use.

In addition, Comparative Examples 5-10 show the case where magnesium sulfate, sodium carbonate, and caustic soda are used as a raw material. Since magnesium sulfate and sodium carbonate / caustic soda used in these examples are dissolved and used in water, it is the result of one or more washing processes performed in each comparative example in order to remove the generated sodium. As shown in these comparative examples, as the number of washing processes increases, the sodium content in the hydrotalcite may be reduced to some extent, but still contains much sodium. When one or more of the raw materials of divalent and trivalent metals are used as raw materials of water-soluble salts, the process requires a huge amount of washing water to be added for the removal of sodium, resulting in a large amount of Na-containing wastewater. do. In addition, since the washing water to be used in the washing process must use sodium free water, a sodium removal facility must be added.

In addition, a commercial hydrotalcite was purchased and compared with the hydrotalcite of Example 1 of the present invention. The results are shown in Table 3 below.

number Example 1 Reference substance 1 Reference substance 2 Na wt ppm 3 240 210 Secondary particle size (D50) ㎛ 1.95 1.62 3.63 Secondary particle size (D100) ㎛ 6 6 23

In the table, Reference material 1 is Kyowa Chemical's Alcamizer-1 which is widely used as LDH for PVC stabilizer, and Reference material 2 is Naox-33 of TODA KOGYO, which is widely used as LDH for PVC stabilizer.

As shown in Table 3, the hydrotalcite prepared in Example 1 is significantly reduced Na content compared to the reference materials 1 and 2, it can be seen that the secondary particle size is almost the same or have excellent performance.

Test Example 1

Fabrication of PVC sheets for performance evaluation as stabilizers for polyvinyl chloride resins.

Based on 100 parts by weight of PVC resin, 1.8 parts by weight of hydrotalcite obtained in Example 1, 1.2 parts by weight of zinc stearate, and 50 parts by weight of DINP with a plasticizer were uniformly mixed, and then heated to 170 ° C. for 8 inches (Kansai, Japan). The mixture was kneaded with a roll for 5 minutes to prepare a sheet having a thickness of 0.6 mm.

Gear Oven Thermal Stability Test

Performance evaluation of ordinary stabilizers for polyvinyl chloride resins tests the degree of deformation, coloring and deterioration by heat. In the gear oven thermal stability test, the workpiece exposed to air after PVC processing is evaluated by testing the degree of deformation, engraftment and carbonization under heat under severe conditions.

After preparing 11 specimens of 1 cm x 1.5 cm in width and length using the sheet prepared above, put into a 190 ℃ gear oven and take out every 10 minutes to measure the degree of degradation of the sheet.

Press Thermal Stability Test

Press thermal stability testing is a common method of evaluating the performance of stabilizers for polyvinyl chloride. During the processing of polyvinyl chloride resin, the equipment is placed in a confined space under conditions of high pressure and high temperature, specifically 160 ° C to 220 ° C. At this time, the stabilizer plays a role of preventing the physical properties, deformation, coloring, etc. of the workpiece due to high temperature and high pressure, and the normal press thermal stability test is used as a deterioration test method under the same conditions of high temperature and high pressure during processing.

Coloring and deterioration during processing of the stabilizer for polyvinyl chloride resin have a large influence on Na inside or on the surface of the hydrotalcite. Five sheets of 5 cm x 5 cm in width and length are prepared using the sheet prepared above. The test pieces are placed side by side with a comparative specimen in a 10 cm x 10 cm x 1 mm press mold, and the tests are performed at 180 ° C. for 30 minutes, 60 minutes and 120 minutes, respectively.

Volume Intrinsic Resistance Measurement

Soft PVC resins, particularly vinyl chloride resins for coated wires, are usually evaluated for electrical resistance performance in addition to performance evaluation for thermal deformation and coloring (ASTM D257). The problem of lowering the electrical resistance when using the stabilizer for the coated wire vinyl chloride resin has a large influence on Na inside or on the surface of the hydrotalcite.

Using the prepared sheet to prepare a press sheet in accordance with a press frame of 10cm × 10cm × 1mm, the specific resistance value is measured using a volume specific resistance measurement device. The measuring instrument used ULTRA MEGOHMMETER (SM-8210, TOA Electronics, Japan).

Test Examples 2-11

Except for using the hydrotalcite obtained in Comparative Examples 3 to 10 as the hydrotalcite, the sheet was made in the same manner as in Test Example 1, and then the gear oven thermal stability test, the press thermal stability test, and the volume resistivity were measured.

Test Examples 12-13

Except for using the reference material 1,2 as the hydrotalcite, the sheet was prepared in the same manner as in Test Example 1, and then the gear oven thermal stability test, the press thermal stability test, and the volume resistivity were measured.

Formulation composition and thermal stability test results are summarized in Table 4 below.

* The evaluation of thermal stability performance was marked as 5 points: very good, 4 points: excellent, 3 points: normal, 2 points: lower, 1 point: very deteriorated.

  Hydrotalcite having four or more points for each evaluation item can be used for PVC stabilizers. This can be confirmed by the test results of reference materials 1,2.

* In the above table, PVC resin used for polyvinyl chloride resin performance evaluation was 1000 degree of polymerization, product name P-1000, Hanwha Corporation, DINP was Aekyung Petrochemical Co., Ltd. zinc stearate was Junsei, Japan It was a product.

 As a result of evaluating hydrotalcite as a heat-resistant heat agent in the polyvinyl chloride resin, it can be seen that Test Example 1 (Example 1 using hydrotalcite) of the present invention has very excellent heat stability performance compared to other products. Comparing Test Example 1 with Test Example 5 (hydrotalcite of Comparative Example 3) without undergoing pulverization, it was found that performances such as oven, press, and electrical resistance performance were deteriorated.

 The test results of Test Examples 2 to 11 show that the higher the Na content of the product, the lower the gear oven, the press and the volume specific resistance performance, and the product having the Na content of 80 ppm or more is difficult to be applied as a PVC thermal stabilizer. (Test Examples 4, 5, 6, 7, 9, 10, 11).

 Test Example 8 (use of hydrotalcite of Comparative Example 7) has a Na content of 200 ppm or less, and can be used as a PVC stabilizer, but there is a problem of using excess Na-washed water during the manufacturing process. This confirms that the present invention is a technology that can effectively control the Na content of the product by using the raw material of the water-insoluble compound, there is no use of washing water and no by-products during the manufacturing process.

In addition, through the test results of Test Examples 12 to 13 (using hydrotalcite of Reference Materials 1 and 2), the hydrotalcite of Example 1 according to the present invention was compared with hydrotalcite which is commonly used. And it can be seen that the electrical resistance performance is the same or excellent.

Claims (9)

delete delete Magnesium, zinc metal oxides or hydroxides and aluminum oxides or hydroxides are mixed and ground to a secondary particle diameter after grinding, D50 of 2 μm or less, and the pulverized mixture is placed in a reaction tank and sealed. Method for producing a hydrotalcite satisfying all the following characteristics, characterized in that the injection of quantitatively measured carbon dioxide gas to a pressure of 0kg / ㎠ until 5-30 hours hydrothermal synthesis at a temperature of 150 ~ 250 ℃.
(1) general formula
[( Mg) _y (Zn) _z ] _1-x (Al) _x (OH) ₂ (CO ₃ ^2- ) _{x /} 2mH ₂ O
In the formula, x, y, z and m are values satisfying the following conditions.
0.2≤x <0.4, y + z = 1, 0.7≤y≤1, 0≤z≤0.3, 0≤m <1
(2) the hydrotalcite particles have an average secondary particle diameter of 0.5 to 2 탆 as measured by laser diffraction scattering;
(3) The sodium component in the hydrotalcite particles is 80 ppm by weight or less.
(4) The hydrotalcite particles contain iron compounds and manganese compounds in a total amount of 0.005 wt% or less in terms of metal (Fe + Mn).
(5) The hydrotalcite particles have a specific surface area of 5 to 40 m 2 / g as measured by the BET method. The method for producing hydrotalcite according to claim 3, wherein the grinding is performed using a wet mill. The method for preparing hydrotalcite according to claim 3, wherein the hydrothermal synthesis reaction is performed at 150 ° C to 190 ° C. The method for producing hydrotalcite according to claim 3, wherein the hydrotalcite obtained is surface treated with stearic acid, a salt thereof, or an anionic surfactant.
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