KR20100004252A - Method of manufacturing hematite platelets, hematite platelets and hematite platelets pigment fabricated using thereof - Google Patents

Abstract

PURPOSE: Hematite platelets are provided to ensure a property suitable for metallic pigment, low gloss, and aspect ratio of 20 or more to express color by interference. CONSTITUTION: A method for manufacturing hematite platelets comprises: a precursor preparation step(S10) of preparing an aqueous solution of iron oxide precursor; a mixing step(S20) of mixing the aqueous solution of iron oxide precursor to obtain an intermediate containing at least one of Fe^(+3), 'K^+, Na^+, Li^+, and Ca^+; and a hydrothermal treatment step(S30) of performing hydrothermal treatment the aqueous solution of iron oxide precursor.

Description

METHOD OF MANUFACTURING HEMATITE PLATELETS, HEMATITE PLATELETS AND HEMATITE PLATELETS PIGMENT FABRICATED USING THEREOF}

The present invention relates to a method for producing a plate-shaped iron oxide, a plate-shaped iron oxide and a plate-iron iron pigment produced therefrom, and more particularly, to a production method for producing a plate-type iron oxide having an aspect ratio of 20 or more suitable for metallic pigments, plate iron oxide and plate iron oxide pigment It is about.

Iron oxides such as hematite, pyrite and magnetite, which are widely produced in nature, have red, yellow and black colors, respectively, and have been used as colorants since BC. The murals painted by them remain in caves around the world, and they still maintain their colors. Currently, most of these iron oxides are made of synthetic materials and are used in many fields as high stability pigments of vivid color, good durability, low cost and low toxicity. For example, it is applied to many products such as paint, ink, rubber, plastic, paper, glass, cement, etc. Furthermore, high purity is harmless to the human body and is used as food, medicine and cosmetics.

Specifically, as the synthetic iron oxide pigment, red to reddish brown hematite (α-Fe ₂ O ₃ , hematite or MIO (Micaceous Iron Oxide) particle powder, yellow to dark brown based margeite ( γ-Fe ₂ O ₃ , maghemite) particle powder and black system magnetite (FeOx · Fe ₂ O ₃ , 0 <x ≦ ₁ , magnetite) particle powder are known.

In such iron oxide pigments, iron oxide pigments (hereinafter referred to as 'plate iron oxides'), particularly hematite, which exhibit a plate-like form, are thin sheets of several micrometers to 10 micrometers due to their shape so that they are arranged in layers in the coating film. As it has excellent characteristics (environmental barrier property), it is used as a rust-preventive pigment of steel structure, wood protective paint, plywood printing ink, or transparent iron oxide with a small particle diameter. It is also used as a coloring pigment. In addition, it has ultraviolet absorption characteristics and concealability to the skin (skin cover effect), and thus is useful as a food packaging film, a colorant of a pharmaceutical container, and a cosmetic extender pigment.

Among these, metallic pigments, such as cosmetic extender pigments, have good slipperiness and adhesion, and have a good skin feel.There is no bleeding due to reflected light through suppression of excessive gloss, and it is based on translucency and natural color tone on the skin. It is desirable to have an appropriate concealment effect. In particular, the glossiness should be adjusted to have a low gloss and at the same time have a color by interference. Therefore, the property to have in order to have such a characteristic should have a particle size of at least 1 micrometer or more, and an aspect ratio defined by the ratio of the particle diameter / thickness of a pigment particle to at least 10 or more.

Conventional plate iron oxide production methods include a dry method and a wet method, and the wet method includes a melting method and a hydrothermal synthesis method. Among these, the dry method is rarely used because the cost of pollution measures due to the generation of a large amount of sulfurous acid gas, sulfuric acid gas and the like is large. In the wet method, the melting method is obtained by reacting iron sulfate or iron hydrochloride solution with alkali to obtain magnetite (black iron) or goethite (iron iron), which is calcined to obtain plate iron oxide.

As a kind of the melting method, for example, as described in Korean Patent Publication No. 1992-11922, a method of co-precipitating barium ions and iron ions followed by heat treatment, wherein the barium ions and iron ions are hydrated or carbonate. A method of preparing hexagonal barium ferrite fine particles having a diameter of 0.2-0.5 μm by coprecipitation in the form of (Carbonate) and then heat-treating at a temperature of 900 ° C. or more has been proposed.

However, in the melting method, the iron oxide particles having an excellent aspect ratio can be obtained and mass-produced, but since the dispersibility of the particles in the solution is poor, it is difficult to control the size of the particles, and it is difficult to obtain the plate-shaped particles. Since the process is carried out at a high temperature of at least 800 ° C. or above, there is a disadvantage that sintering between particles occurs and is uneconomical. In particular, barium ferrite plate has a magnetic property has a disadvantage to be used as a pearl pigment.

On the other hand, US Patent US4867795 proposed a method of obtaining iron oxide in the form of Mn, Al solid solution by synthesizing FeSO ₄ in an autoclave with a precursor consisting of Al (OH) ₃ , KMnO ₄ , NaAlO ₂ as a raw material. The aspect ratio of the iron oxide produced by this method is good as 20 or more, but there is a problem that the synthesis temperature exceeds 800 ℃.

As a hydrothermal synthesis method, for example, Japanese Patent Laid-Open Publication No. 55-154319 discloses economical α- by means of hydrothermal treatment in an aqueous alkali solution together with an oxidizing agent using iron oxides such as iron ore as raw materials, and via magnetite. A method of obtaining Fe ₂ O ₃ has been proposed.

On the other hand, European Patent EPA0180881 proposes a method of obtaining α-Fe ₂ O ₃ by Fe (NO ₃ ) ₃ .9H ₂ O as a raw material by hydrothermal synthesis.

In addition, Japanese Patent Application Laid-Open No. 58-69730 proposes a method capable of efficiently producing plate-shaped particles by hydrothermally treating γ-Fe ₂ O ₃ alone in an aqueous alkaline solution.

Further, in Japanese Patent Laid-Open Publication No. Hei 6-166520, 1 - ferrous salt aqueous solution, a mixture of aluminum salt solution and the carbonate solution, Fe ^{2 +,} and a hydrotalcite of the sheet containing Al ^{3 +} (hydrotalcite) the particles form The method of obtaining the plate-shaped hematite microparticles | fine-particles which obtained the solid solution of aluminum by the hydrothermal treatment was proposed.

According to the hydrothermal synthesis method, it is possible to produce a plate-like iron oxide at a relatively low temperature, there is no sintering phenomenon between the particles, it is easy to control the particle size, while the hydrothermal synthesis method is mainly used for nanometer iron oxide particles Although suitable for preparation, the particle size is inadequate for metallic pigments such as cosmetic pigments which should be formed in micron size or larger. In particular, the plate-shaped iron oxide thus obtained has a disadvantage in that it does not satisfy the optical properties and adhesion as metallic pigments or pearl pigments because the aspect ratio is as small as 2 to 10.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to use a hydrothermal synthesis method, which is suitable as a metallic pigment, and has a low gloss and at the same time a plate-type iron oxide having an aspect ratio of 20 or more in order to have color by interference. It is to provide a plate iron oxide pigment.

Hereinafter, the present invention will be described.

The present invention is a means for solving the above problems, the plate iron oxide production method according to the present invention, as shown in Figure 1, the ferric salt; Alkaline aqueous solution; And potassium salts consisting of potassium phosphate, potassium sulfate, potassium chloride, potassium nitrate, potassium carbonate, potassium hydrogencarbonate, potassium bromide and potassium fluoride, sodium salts having the same anion as the potassium salts, lithium salts, and calcium Precursor manufacturing step (S10) for producing an iron oxide precursor solution containing an additive consisting of at least one of the salt; Mixing the iron oxide precursor aqueous solution uniformly to obtain an intermediate product including at least one of Fe ^{+ 3} and K ⁺ , Na ⁺ , Li ⁺ , and Ca ⁺ (S20); It includes a hydrothermal treatment step (S30) for hydrothermal treatment of the aqueous solution of the iron oxide precursor.

The ferric salt used in the present invention is not particularly limited as long as it is in the form of a salt containing Fe ^{+ 3} ions, but it may be ferric chloride (FeCl ₃ ) or ferric sulfate (Fe ₂ (SO _{4). 3} ) and ferric nitrate (Fe (NO ₃ ) ₃ ) are preferably used alone or in combination.

Alkali aqueous solution is used individually or in mixture of 2 or more types of potassium hydroxide, sodium hydroxide, calcium hydroxide, and lithium hydroxide which are common alkali aqueous solution. The aqueous alkali solution, which is generally used in the wet manufacturing method of iron oxide, in the present invention adjusts the pH, serves to neutralize the ferric salt alkali.

Here, the pH of the aqueous solution of the iron oxide precursor is preferably 11 or more, preferably 13 or more, in order to obtain an intermediate including at least one of Fe ^{+ 3} and K ⁺ , Na ⁺ , Li ⁺ , Ca ⁺ , which will be described later. . When the pH is lowered to 11 or less, it is difficult to produce the intermediate product.

In addition, in the present invention, in the precursor manufacturing step or mixing step, it is preferable to change the amount of the aqueous alkali solution to be mixed properly. Alkali aqueous solution added in the initial mixing step reacts with Fe ⁺³ to produce an initial product of Fe (OH) ₃ , whereas in an additional mixing step, the aqueous alkali solution is added, thereby reacting with an additive cation to Since the intermediate product is obtained, both are distinguished.

In the mixing step (S20), the aqueous alkali solution, 80 to 300 parts by weight, more preferably 100 to 200 parts by weight is added to 100 parts by weight of the ferric salt, 30 to 900 parts by weight, more in the pretreatment step Preferably from 50 to 600 parts by weight is added to produce an initial product and an intermediate product, respectively.

In addition, the additive of the present invention is amorphous alkali system that is an intermediate product together with Fe ^{+ 3} ions of the ferric salt in the state of being ionized to at least one of K ⁺ , Na ⁺ , Li ⁺ , Ca ⁺ in a mixed solution Iron oxide, for example, in the form of K _x Fe _y O _z (x, y is 1 to 2, z is 1 to 4), or is dissolved in the nano-sized α-Fe ₂ O ₃ as the final product It plays a role of seed in the crystallization of the particles. Also, more specifically, the K _x Fe _y O _z iron oxide mixture reacts with the nano-sized α-Fe ₂ O ₃ as a final product, resulting in the growth of the plate iron oxide particles, K ⁺ , Na ⁺ , Li ⁺ , Ca ^As the addition amount of the alkali metal salt containing at least one ion of ⁺ increases, the aspect ratio (particle size / thickness) can be obtained while the diameter increases, and the color of the pigment varies according to the treatment temperature and the treatment method. You can. It is also possible to produce plate iron oxide crystals having various aspect ratios depending on the amount of the additive in the form of the neutral alkali metal salt used.

That is, after the additive is oxidized, it adheres to the crystal surface of the plate-shaped iron oxide during the crystallization process, and the growth in the radial direction is promoted, while the growth in the thickness direction is relatively suppressed, so that the iron oxide is formed alone. Is similar, but serves to form plate iron oxide crystals which can effectively reduce the thickness.

Here, the ratio of the ferric salt and the additive is ferric salt It is preferable that the additive in the form of a neutral alkali metal salt is 0.01 to 4 parts by weight, more preferably 0.05 to 4 parts by weight based on 100 parts by weight. When the additive is added in less than 0.01 parts by weight, it is difficult to obtain an aspect ratio of 10 or more, and when the addition amount exceeds 4 parts by weight, there is a problem in that the size of the plate-shaped iron oxide obtained is small.

In addition, as the additive, in addition to the above-described potassium salt, sodium salt, lithium salt, and calcium salt, diethanolamine containing K ⁺ , Na ⁺ , Li ⁺ , Ca ⁺ ions (di-ethanol amine ), Tri-ethanol amine, chelate organic compounds and the like can be used.

In addition to the above method, the plate-type iron oxide may be prepared by adding iron oxide seeds of 1 to 50 nm uniform nanoparticles to the iron oxide precursor aqueous solution in the precursor preparation step (S10). This is a method of growing plate-like iron oxide crystals by initially adding nanometer-sized iron oxide particles as seeds of the crystals.

The iron oxide seed is preferably added in an amount of 0.001 to 1 part by weight, more preferably 0.005 to 0.2 part by weight, based on 100 parts by weight of the ferric salt. When the addition amount of the iron oxide seed is added less than 0.001, the effect on the plate-shaped iron oxide aspect ratio and dispersion is less, and when the addition amount exceeds 1 part by weight, the particles of iron oxide is too small to obtain a plate-shaped iron oxide having an effective aspect ratio There is a problem that is not easy.

Mixing step (S20) for uniformly mixing the iron oxide precursor solution, the obtained iron oxide mixed solution is stirred at a rotation speed of 200rpm or more, or a homogenizer, ball milling, static mixer, ultrasonic, microwave equipment It is preferable to perform these etc. individually or in combination of 2 or more types.

Hydrothermal treatment step (S30), using an autoclave device, it is preferably carried out at 150 to 250 ℃ temperature, for 2 to 240 hours. In general, as the alkali concentration increases, the reaction temperature for producing the plate-like hematite particles obtained tends to decrease. If it is less than 150 ° C., plate-shaped particles tend not to be obtained. If it exceeds 250 ° C., plate-shaped particles may be obtained, but suitable upper limit temperatures for stable operation of the hydrothermal treatment apparatus and economical production of plate-shaped iron oxides. It is preferable to set it as 250 degreeC.

In the hydrothermal treatment step (S30), the intermediate product produced by performing the mixing step (S20) acts as a seed of the crystal, plate-shaped hematite (α-) in which K, Na, Li, Ca is dissolved through the hydrothermal reaction Fe ₂ O ₃ ) iron oxide crystals are produced.

In addition, after the hydrothermal treatment step (S30), it is preferable to further include a washing step (S40) for filtering, washing and drying the plate-shaped iron oxide particles in order to obtain a plate-shaped iron oxide particles of the desired size and thickness.

The size (diameter) of the plate-shaped iron oxide particles thus prepared is 1 to 100 µm, more preferably 5 to 80 µm. If the particle diameter is less than 1 µm, the reflectance drops, and if the particle diameter exceeds 100 µm, it is not suitable as a metallic pigment.

The aspect ratio of the plate iron oxide is 20 or more, preferably 25 or more. When the aspect ratio is less than 20, there is a problem in that interference color development as an optical characteristic is difficult, the adhesion of particles is lowered, and the usability is poor. Although there is no restriction | limiting in the upper limit of an aspect ratio, when it exceeds 100, strong particle gloss may be expressed.

Based on the plate-like iron oxide synthesized as described above, a plate-like iron oxide pigment of a metallic luster coated with a metal oxide thereon can be prepared, and thus a pearl pigment having a strong metallic effect can be produced.

The plate-shaped iron oxide pigment is, for example, suspended in deionized water, the plate-like iron oxide obtained by the production method, and then added with an acid such as hydrochloric acid or sulfuric acid and stirred, and simultaneously adding a metal chloride solution and an aqueous alkali solution to the aqueous solution To reflux to prepare an aqueous solution of a plate-shaped iron oxide particle coated with a hydrated metal oxide layer, and to prepare a pigment by filtration, washing, drying and firing the aqueous solution.

In this way, the metal oxide coated on the surface of the plate-shaped iron oxide, in the field of producing a metallic pigment, is generally used to express the metallic luster and interference color by coating the surface of the pigment, but is not particularly limited, specifically SnO ₂ One or two or more selected from TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , MgO, and MnO ₂ may be coated. More preferably, it is preferable to form a multi-layer coating layer using various metal oxides. For example, after forming a coating layer as SiO ₂ , TiO ₂ is formed on the surface of the formed coating layer. The coating layer can be formed. Such a multilayer coating layer has an advantage of increasing the hiding power and obtaining a high quality interference color.

According to the present invention, there is an advantage that a plate-shaped iron oxide having a particle size of 1 to 100 µm, a particle thickness of 0.3 to 4 µm, and an aspect ratio of 20 or more.

Hereinafter, the effect of the present invention will be described with reference to specific experimental examples of the present invention.

First, the synthesis of plate iron oxide will be described.

Experimental Example  One

Synthesis of Plate Iron Oxide with Changes in Potassium Chloride (KCl) as Additive Salt in Precursor Mixtures

Stir the mixed solution of 10 g of iron chloride (FeCl ₃ ), 12 g of potassium hydroxide (KOH), and 120 g of water.

A plate iron oxide precursor mixed solution was prepared. Next, 0.1 to 0.4 g of potassium chloride and 30 g of potassium hydroxide were further added to the mixed solution as an additive salt to change the composition ratio. At this time, the mixed solution was prepared by uniformly mixing at 200rpm or more with a stirrer. The mixture was then placed in a hydrothermal reactor and heated at 170 ° C. for 20 hours. After the hydrothermal reaction was completed, the hydrothermal reaction vessel was cooled at room temperature, washed three times or more with distilled water, and then dried at 60 ° C. for 1 day to obtain a final product.

In this case, the obtained product is a plate-shaped iron oxide (α-Fe ₂ O ₃ ) of a single crystal structure, the aspect ratio of the powder of Experimental Example 1-4 as shown in the SEM (Scanning Electron Microscopy) photograph of Fig. It can be seen that the single crystal plate iron oxide having a 27 (particle size / thickness ratio = 17 μm / 0.63 μm) was prepared, and FIG. 3A shows the overall shape of the plate iron oxide particles obtained as a result as shown in FIG. Figure 3b is a photograph of the upper surface of the particles of Experimental Example 1-4 by an optical microscope, showing that the particles are close to the hexahedron of the plate-like body and reddish purple single crystals. Figure 4 shows the particle size distribution of the plate iron oxide measured by a particle size analyzer (Malvern Co.). The particle size D ₁₀ was measured at 9 μm, D ₅₀ at 17 μm, and D ₉₀ at 25 μm. As a result of the crystallinity evaluation according to the X-ray diffraction analysis shown in FIG. 5, it was confirmed that the product was iron oxide (α-Fe ₂ O ₃ , JCPDS No. 86-0550).

Experimental Example  2

Change in Plate Iron Oxide Synthesis Temperature

Stir the mixed solution of 10 g of iron chloride (FeCl3), 12 g of potassium hydroxide (KOH), and 120 g of water.

A plate iron oxide precursor mixed solution was prepared. Next, 0.3 g of KCl and 30 g of potassium hydroxide were further added to the mixed solution to change the composition ratio. At this time, the mixed solution was prepared by uniformly mixing at 200rpm or more with a stirrer. Then, the mixture was placed in a hydrothermal reactor and heated at 170 to 220 ° C. for 20 hours. After the hydrothermal reaction was completed, the hydrothermal reaction vessel was cooled at room temperature, washed three times or more with distilled water, and then dried at 60 ° C. for 1 day to obtain a final product.

At this time, the obtained product is a plate-shaped iron oxide (α-Fe ₂ O ₃ ) of a single crystal structure, the powder of Experimental Example 2-1 as shown in the SEM (Scanning Electron Microscopy) photograph of Fig. It can be seen that a single crystal plate-shaped iron oxide having a ratio of 25 (particle size / thickness ratio = 20 μm / 0.8 μm) was produced.

Experimental Example  3

Synthesis of Plate Iron Oxide with Variation of KOH in Precursor Mixture

A mixed solution of 10 g of iron chloride (FeCl 3), 12 g of potassium hydroxide (KOH), and 120 g of water was stirred to prepare a plate-shaped iron oxide precursor mixed solution. Next, the amount of potassium hydroxide was changed to 6 to 60 g in the mixed solution, which was further added to change the composition ratio. At this time, the mixed solution was prepared by uniformly mixing at 200rpm or more with a stirrer. The mixture was then placed in a hydrothermal reactor and heated at 170 ° C. for 20 hours. After the hydrothermal reaction was completed, the hydrothermal reaction vessel was cooled at room temperature, washed three times or more with distilled water, and then dried at 60 ° C. for 1 day to obtain a final product.

At this time, the obtained product is a plate crystal iron oxide (α-Fe ₂ O ₃ ) of a single crystal structure, the powder of Experimental Example 3-4 was observed through the SEM (Scanning Electron Microscopy) photograph of Figure 7, the aspect ratio is 13 (particle size It can be seen that a single crystal plate-shaped iron oxide having a ratio of / thickness = 23 μm / 1.8 μm) was produced.

From Experimental Example 3, it can be seen that as the KOH content increases, the size of the plate-shaped iron oxide particles increases proportionally and the aspect ratio increases slightly, and the aspect ratio of the plate-shaped iron oxide particles obtained without the addition of an additive salt is less than 20. there was.

Experimental Example  4

Method for manufacturing by adding iron oxide seeds of nanoparticles to plate iron oxide

The manufacturing method was performed in the same manner as in Experimental Example 2-1.

8 is a transmission electron microscopy (TEM) photograph of the nanoparticle iron oxide seed used in the experiment. FIG. 9 is a SEM (Scanning Electron Microscopy) photograph of the powder obtained by adding the iron oxide nanoparticle seed of FIG. 8 by 0.01 part by weight based on 100 parts by weight of the ferric salt, and prepared by the method of Experimental Example 2-1. As a result of measuring the particle side surface, it can be seen that a single crystal plate-shaped iron oxide having an aspect ratio of 17 (ratio of particle size / thickness = 10 μm / 0.6 μm) was produced.

division  Weight of precursor mixed solution (g) Hydrothermal synthesis Particle Size / Thickness ^* (µm / µm) Aspect ratio Particle color Fe (NO ₃ ) ₃ KOH KCl H ₂ O Temperature / hour ( ^o C / h) Experimental Example 1 1-1 10 42 0.1 120 170/20 19 / 0.95 20 Purple 1-2 10 42 0.2 120 170/20 19 / 0.90 21 Purple 1-3 10 42 0.3 120 170/20 19 / 0.80 24 Fuchsia 1-4 10 42 0.4 120 170/20 17 / 0.63 27 Fuchsia Experimental Example 2 2-1 10 42 0.3 120 180/20 20 / 0.80 25 Fuchsia 2-2 10 42 0.3 120 200/20 21 / 1.00 21 Purple 2-3 10 42 0.3 120 220/20 22 / 1.20 18 Purple Experimental Example 3 3-1 10 24 - 120 180/20 11 / 1.20 9 Black purple 3-2 10 30 - 120 180/20 15 / 1.40 9 black 3-3 10 42 - 120 180/20 19 / 1.70 11 black 3-4 10 48 - 120 180/20 23 / 1.80 13 black

* The particle size and thickness of the plate-shaped iron oxide are the average values of 20 particles on the electron micrograph.

Next, the plate-shaped iron oxide pigment was obtained based on the plate-shaped iron oxide obtained by the manufacturing method of the above experimental example, and the study about the effect was performed through the following Example.

Example  One

100-150 g of the plate-shaped iron oxide particles obtained in Experimental Example 1-1 were suspended in 2 L of deionized water, and then heated to 70-80 ° C., 5% hydrochloric acid was added to adjust the pH to 2, followed by stirring for 30 minutes. . 40% of TiOCl ₂ and sodium hydroxide solution are then added to form a TiO (OH) ₂ coating layer on the particle surface. The addition amount of TiOCl ₂ and sodium hydroxide solution increased, resulting in interference colors of gold, red, purple, blue, and green. When the desired interference color was obtained, the addition of TiOCl ₂ and sodium hydroxide solution was stopped and stirred for at least 10 minutes. . After filtration, washing, and drying, and then calcining at 800 ° C., an anatase titanium dioxide layer was formed on the surface of the plate-shaped iron oxide particles.

Example  2

100-150 g of the plate-shaped iron oxide particles obtained in Experimental Example 1-1 were suspended in 2 L of deionized water, and then heated to 70-80 ° C., 5% hydrochloric acid was added to adjust the pH to 2, followed by stirring for 30 minutes. . 60 mL of 5% SnCl ₄ · 5H ₂ O solution was added simultaneously with sodium hydroxide solution, stirred for 30 minutes, and then TiO (OH) ₂ coated layer on the surface of iron oxide particles by adding 40% TiOCl ₂ and sodium hydroxide solution. Creates. The amount of TiOCl ₂ and sodium hydroxide solution was increased, and as the thickness of the coating layer was increased, interference colors of gold, red, purple, blue, and green appeared, and when the desired interference color was obtained, the addition of TiOCl ₂ and sodium hydroxide solution was stopped. Then, the mixture was stirred for 10 minutes or more. After filtration, washing, and drying and baking at 800 ° C., a layer of titanium dioxide (TiO ₂ ) having a rutile structure was formed on the surface of plate-shaped iron oxide particles. 10 is a SEM photograph of the plate-shaped iron oxide pigment coated with the titanium dioxide (TiO ₂ ) layer.

Example  3

100-150 g of the plate-shaped iron oxide particles prepared in Experimental Example 1-2 were suspended in 2 L of deionized water, and then heated to 70-80 ° C., 5% hydrochloric acid was added to adjust the pH to 2, followed by stirring for 30 minutes. I was. Then, 40% of TiOCl ₂ and sodium hydroxide solution were added to form a TiO (OH) ₂ coating layer on the plate iron oxide particle surface. At this time, the addition amount of TiOCl ₂ and the sodium hydroxide solution was added until it turned gold. After stirring for at least 30 minutes and adjusting the pH to 3 by the addition of aqueous sodium hydroxide solution, the ferric chloride solution was added until the required pearl color appeared, and then filtered, washed and dried, and then calcined at 900 ° C. A layer (III) was formed on the surface of the plate-shaped iron oxide particles.

Example  4

100-150 g of the plate-shaped iron oxide particles obtained in Experimental Example 1-2 were suspended in 2 L of deionized water, and then heated to 70-80 ° C., 5% hydrochloric acid was added to adjust the pH to 3, followed by stirring for 30 minutes. . Aqueous solution of sodium hydroxide was added to maintain the pH, then the ferric chloride solution was added until the required pearl color appeared, followed by filtration, washing and drying, followed by calcination at 900 ° C. Formed.

Although the preferred experimental examples and examples of the present invention have been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above experimental examples and examples. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

1 is a flow chart sequentially showing a method for producing a plate-type iron oxide according to an experimental example of the present invention

Figure 2 is a SEM photograph showing the side of the plate-shaped iron oxide particles prepared by Experimental Example 1-4

3A is a SEM photograph showing the top surface of the plate-shaped iron oxide particles of FIG.

3b is an optical microscope photograph of the top surface of the plate-shaped iron oxide particles of FIG.

4 is a view showing a particle size distribution of the plate-shaped iron oxide of FIG.

5 is a view showing an XRD pattern of the plate-shaped iron oxide powder of FIG.

6 is a SEM photograph showing the side surface of the plate-shaped iron oxide particles prepared by Experimental Example 2-1

7 is a SEM photograph showing the side surface of the plate-shaped iron oxide particles prepared by Experimental Example 3-4

8 is a TEM photograph of the particle size and shape of the nanoparticle iron oxide seed

9 is a SEM photograph of the upper surface of the plate-shaped iron oxide particles prepared using the iron oxide seed of FIG.

FIG. 10 is a SEM photograph of the side surface of TiO ₂ coated particles on the plate iron oxide surface of FIG. 2.

Claims (11)

Ferric salts; Alkaline aqueous solution; And Potassium salts consisting of potassium phosphate, potassium sulfate, potassium chloride, potassium nitrate, potassium carbonate, potassium hydrogencarbonate, potassium bromide, potassium fluoride, sodium salts having the same anion as the potassium salts, lithium salts, and calcium salts Precursor preparation step of preparing an aqueous solution of the iron oxide precursor containing an additive consisting of at least one of the salts; Mixing the iron oxide precursor aqueous solution to obtain an intermediate product including Fe ^{+ 3} and at least one of K ⁺ , Na ⁺ , Li ⁺ , and Ca ⁺ ; A plate-type iron oxide manufacturing method comprising a hydrothermal treatment step of hydrothermally treating the iron oxide precursor solution. The method of claim 1, The hydrothermal treatment step, a plate-shaped iron oxide manufacturing method, characterized in that performed for 2 to 240 hours at a temperature of 150 to 250 ℃. The method of claim 1, The ferric salt is a plate iron oxide manufacturing method, characterized in that at least one of FeCl ₃ , Fe ₂ (SO ₄ ) ₃ , Fe (NO ₃ ) ₃ . The method of claim 1, The alkaline aqueous solution is at least one of potassium hydroxide, sodium hydroxide, calcium hydroxide, lithium hydroxide manufacturing method of the plate iron oxide. The method of claim 1, PH of the iron oxide precursor aqueous solution is a plate iron oxide manufacturing method, characterized in that 11 or more. The method of claim 1, After the hydrothermal treatment step, the plate-type iron oxide manufacturing method characterized in that it further comprises a washing step of filtering, washing and drying. The method of claim 1, The iron oxide precursor aqueous solution further comprises 0.001 to 1 parts by weight of iron oxide seed (seed), which is iron oxide nanoparticles having a size of 1 to 50 nm with respect to 100 parts by weight of the ferric salt. In the plate-shaped iron oxide produced by the manufacturing method according to claim 1, The plate-shaped iron oxide, hematite (α-Fe ₂ O ₃ ) particles of the solid solution of K, Na, Li, Ca is contained, A plate-shaped iron oxide, characterized by having a particle size of 1 to 100 µm, a particle thickness of 0.3 to 4 µm, and an aspect ratio of 20 or more. A plate-shaped iron oxide pigment coated with a metal oxide thereon, based on the plate-shaped iron oxide according to claim 8. The method of claim 9, wherein the metal oxide is SnO ₂ , TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , MgO, and MnO _2. It is at least one of a plate iron oxide pigment. The method of claim 9 or 10, The plate-shaped iron oxide pigment, characterized in that the metal oxide coating layer is formed in a multilayer of two or more layers.

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