KR102124124B1 - Method for producing plate-like Alumina with excellent aspect ratio - Google Patents

Abstract

Disclosed is a method for producing plate-like alumina having an excellent aspect ratio. According to one aspect of the present embodiment, aluminum hydroxide particles having a desired particle size are easily produced, and a method for producing plate-like alumina having a uniform particle size distribution is provided based thereon.

Description

Method for producing plate-like alumina with excellent aspect ratio}

The present invention relates to a method for producing plate-shaped alumina having excellent squareness ratio and little aggregation.

The contents described in this section merely provide background information for this embodiment, and do not constitute a prior art.

Plate-shaped alumina is widely used as various ceramics, abrasives, functional cosmetics, pigments, paints, heat dissipation, separators or additives for increasing strength.

When manufacturing such plate-shaped alumina, an aluminum compound, transitional alumina or aluminum hydroxide heat-treated after mechanical grinding was used as the main raw material of plate-shaped alumina. Alumina compounds are aluminum hydroxide processed into different forms, and include aluminum sulfate, aluminum nitrate, or aluminum chloride. The process of manufacturing a plate-shaped alumina using such a conventional alumina compound has a problem that the alumina content of the raw material itself is less than 30%, resulting in low yield, and air pollutants such as sulfur, nitric acid, or hydrochloric acid are generated in the process. In addition, in order to use an aluminum compound in a conventional plate-shaped alumina production process, the aluminum compound is completely dissolved in an aqueous solution, GEL-ized by hydrolysis, and has a problem that a aging process is separately required.

The process of manufacturing plate-shaped alumina using transitional alumina boehmite, delta, beta, or gamma alumina has the inconvenience of pretreatment such as heat treatment or pressurization of aluminum hydroxide separately.

Aluminum hydroxide particles have characteristics that are difficult to grow into thin plate-like particles having a good squareness ratio, and they are not used as a raw material in the manufacture of plate-shaped alumina because they are highly agglomerated even when grown in a plate shape. To use such aluminum hydroxide in a plate-shaped alumina manufacturing process, the aluminum hydroxide is heat-treated and mechanically pulverized for a long time to separate the particle size, followed by heat treatment by adding a large amount of a flux with a fluorine compound to the aluminum hydroxide using a mineralizer addition method. , Aluminum hydroxide must be grown with plate-shaped alumina. In this way, when aluminum hydroxide is grown into plate-shaped alumina, the plate-shaped alumina becomes thicker and does not have a uniform particle size, so there is a problem that it is insufficient to be used as a pigment.

In addition, when the aluminum hydroxide is crushed and heat-treated, as a large amount of flux is added, the volume of the flux increases in proportion to the amount of flux during heat treatment, so the crucible used during heat treatment may be damaged by the volume of flux. It occurs a lot. In addition, after the heat treatment reaction, the plate-like alumina that has undergone natural cooling forms a hardly agglomerated crystal due to the melted flux, which causes a problem that it is not separated by being deposited on the crucible wall.

One embodiment of the present invention, by using aluminum hydroxide as a raw material to easily produce aluminum hydroxide particles of a desired particle size, on the basis of this to provide a plate-shaped alumina manufacturing method of uniform particle size distribution without separate particle size separation .

In addition, an embodiment of the present invention provides a high refractive index, high saturation, and high brightness pearl luster when TiO2 is coated by depositing aluminum hydroxide particles of almost constant size in caustic soda solution and growing them into plate-shaped alumina particles of almost uniform size. There is a purpose.

In addition, one embodiment of the present invention, by reducing the amount of the flux added compared to the conventional, aluminum hydroxide particles to prevent damage to the crucible when heat-treated in the form of plate-shaped alumina and can easily separate the plate-shaped alumina from the crucible It is an object to provide a method for manufacturing plate-shaped alumina.

According to one aspect of this embodiment, caustic soda and aluminum hydroxide are dissolved in caustic soda solution to a predetermined ratio (Al ₂ O ₃ /Na ₂ CO ₃ ) to obtain a solution and a seed is obtained from the solution. (Seed) is added and stirred to precipitate the aluminum hydroxide until the ratio of the caustic soda and aluminum hydroxide reaches a predetermined reference value to obtain a mixed solution, and a flux mixed by adding a molten salt and a dispersant used as a flux to the mixed solution. After the mixing process and the flux mixing process, a neutralization process to generate a neutralization solution by adding a neutralizing agent to the mixed solution, a drying process to dry the neutralization solution to produce an aluminum hydroxide compound, and heat-treating the aluminum hydroxide compound, and then cooling the mixture. The heat treatment process to produce a powder containing plate-shaped alumina particles and the filtering process to produce a cake by filtering particles and flux having a predetermined size contained in the plate-shaped alumina particles, and slurrying the cake, to form a slurry ( Slurry) a decomposition process of decomposing at least one plate-shaped alumina particle or plate-shaped alumina twins, and drying the slurry, and removing particles in the dried slurry (Slurry) to remove plate-shaped alumina particles having a predetermined particle size It provides a plate-shaped alumina production method characterized in that.

According to one aspect of this embodiment, the process of obtaining the lysate is characterized by using 200-300 g/L (Na ₂ CO ₃ ) caustic soda and aluminum hydroxide having a purity of 95% or more.

According to one aspect of this embodiment, the predetermined ratio (Al ₂ O ₃ /Na ₂ CO ₃ ) of the caustic soda and aluminum hydroxide is 0.6 to 0.8, and is characterized in that the aluminum hydroxide is supersaturated.

According to an aspect of the present embodiment, the predetermined reference value of the process of obtaining the mixed liquid is characterized in that it is less than 0.3.

According to one aspect of this embodiment, the heat treatment process is characterized in that the aluminum hydroxide compound is maintained for 1 to 4 hours in the first temperature section, the second temperature section, and the third temperature section, respectively, without adding a separate gas.

As described above, according to an aspect of the present invention, using normal aluminum hydroxide (Wet-Al(OH) ₃ ) as a raw material, aluminum hydroxide particles having a desired particle size are easily produced, and based on this, a particle size distribution is uniform. There is an advantage that alumina can be produced.

In addition, according to an aspect of the present invention, by depositing aluminum hydroxide particles having a substantially constant size and growing them into plate-shaped alumina particles having a substantially uniform size, the TiO2 coating has a high refractive index, high saturation, and high brightness pearl luster.

In addition, according to an aspect of the present invention, by reducing the amount of the flux added compared to the prior art, when the aluminum hydroxide particles are grown in the form of plate-shaped alumina, the crucible is prevented from breaking and the plate-shaped alumina is easily separated from the crucible. There is this.

1 is a flow chart showing a plate-shaped alumina production method according to an embodiment of the present invention.
2 is a view showing a scanning electron microscope observation result of the plate-shaped alumina powder according to an embodiment of the present invention.
3 is a graph showing the results of particle size analysis of a plate-shaped alumina powder according to an embodiment of the present invention.
Figure 4 is a graph showing the results of XRD (X-Ray Diffraction) analysis of the plate-shaped alumina powder according to an embodiment of the present invention.

The present invention can be applied to various changes and may have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing each drawing, similar reference numerals are used for similar components.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. The term and/or includes a combination of a plurality of related described items or any one of a plurality of related described items.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. It should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

Terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. It should be understood that terms such as “include” or “have” in the present application do not preclude the existence or addition possibility of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. .

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains.

Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

In addition, each configuration, process, process or method included in each embodiment of the present invention may be shared within a technically inconsistent range.

1 is a flow chart showing a plate-shaped alumina manufacturing method according to an embodiment of the present invention.

Caustic soda and aluminum hydroxide are mixed, and aluminum hydroxide is dissolved in caustic soda (S105).

200-300 g/L of caustic soda solution and general aluminum hydroxide (Wet-Al(OH) ₃ ) having a purity of 95% or more are mixed so that aluminum hydroxide is in a supersaturated state. When a seed is added in the supersaturation state of aluminum hydroxide, precipitation of aluminum hydroxide particles occurs well, so the ratio of alumina and caustic soda (Al ₂ O ₃ /Na ₂ CO ₃ , abbreviated as A/C hereinafter) is 0.6. It is desirable to mix aluminum hydroxide and caustic soda to be ~0.8. When caustic soda and aluminum hydroxide are mixed at an A/C ratio of 0.8 or more, waste of aluminum hydroxide particles is generated because aluminum hydroxide is poorly soluble in caustic soda. Conversely, when caustic soda and aluminum hydroxide are mixed at an A/C ratio of 0.6 or less, aluminum hydroxide saturation is lowered, and thus aluminum hydroxide precipitation is less likely.

Caustic soda and aluminum hydroxide (Wet-Al(OH) ₃ ) A pressure of 4 to 6 atmospheres is added to the mixed solution, and the temperature of the solution is raised to 150°C and heated by sealing for 3 to 4 hours to produce caustic soda and aluminum hydroxide ( Wet-Al(OH) ₃ ) The mixed solution is made into a completely dissolved sodium aluminate supersaturated solution. And the temperature is lowered so that the temperature of the sodium aluminate supersaturated solution becomes 60 to 70°C.

Aluminum hydroxide is precipitated by adding a seed to the sodium aluminate supersaturated solution (S110).

The seed is added to the sodium aluminate supersaturated solution (hereinafter referred to as the'dissolution'). Examples of seeds include aluminum sulfate or 0.1 to 1.0 μm aluminum hydroxide or alumina GEL (aluminum ammonium sulfate, sodium aluminum sulfate), but are not limited thereto. When the seed is added to the solution and mixed, the dissolved aluminum hydroxide adheres to the seed and grows as particles to precipitate. At this time, the seed serves as a nucleus for the growth of aluminum hydroxide particles. It is important to disperse the seeds evenly in the lysate because the aluminum hydroxide may aggregate and precipitate if the seeds are not evenly dispersed and mixed in the lysate. Therefore, the seeds added to the lysate are stirred so that the seeds are evenly dispersed in the lysate and aluminum hydroxide having a size of 1 to 10 μm is precipitated. Aluminum hydroxide adheres to the seed, grows as particles, and takes an average of 2 to 3 days to precipitate, and when precipitated for 2 to 3 days or more, most of the aluminum hydroxide is precipitated and hardly precipitates. Therefore, the stirring time is preferably 2-3 days. And when adding a seed, the aluminum hydroxide added as a seed is preferably 5 to 10% of the amount of the added aluminum hydroxide. When the amount of the seed to be added is too small compared to the amount of aluminum hydroxide, precipitation of aluminum hydroxide does not occur well. Conversely, when the amount of the seed exceeds 10% of the amount of aluminum hydroxide, the precipitated aluminum hydroxide particles become too fine, and there is a fear that platelet alumina with a small particle size will be generated later from the aluminum hydroxide particles.

When aluminum hydroxide having a size of 1 to 10 μm is precipitated and particles are generated, the A/C ratio of the lysate is gradually lowered in proportion to the generated particles. At this time, aluminum hydroxide is precipitated until the A/C ratio of the dissolved solution becomes less than 0.3. When the A/C ratio of the lysate is 0.3 or more, the aluminum hydroxide that can be precipitated from the lysate remains, so that the A/C ratio of the lysate is allowed to precipitate as much as 1-10 μm aluminum hydroxide in the lysate. It precipitates until it becomes less than 0.3. When aluminum hydroxide is precipitated in the solution as described above, a mixture solution in which aluminum hydroxide particles are formed in the solution is obtained.

After the molten salt is added to the mixed solution where aluminum hydroxide is precipitated as a fluxing agent, a dispersing agent is further added to mix (S115).

Aluminum hydroxide is precipitated and a molten salt is added as a flux to the mixed liquid present as particles. The molten salt serves to grow the aluminum hydroxide particles in a plate shape in the heat treatment process to be performed later. The molten salt includes at least one of sodium sulfate, sodium carbonate, sodium hydrogen carbonate, potassium sulfate, potassium carbonate, potassium chloride, magnesium sulfate, sodium chloride, calcium sulfate and calcium carbonate. When adding molten salt, 40 to 80% of molten salt is added based on the amount of aluminum hydroxide dissolved in the dissolved solution. For example, when 100 g of aluminum hydroxide is dissolved in a dissolved solution, 50 g of sodium sulfate may be added or 50 g of sodium sulfate and 25 g of sodium carbonate may be added to the molten salt. After the molten salt is added to the solution as described above, in order to disperse the aluminum hydroxide particles, a dispersant is added in an amount of 0.5 to 2% based on the amount of aluminum hydroxide dissolved in the solution and stirred for 3 to 5 hours. As the dispersing agent, sodium hexametaphosphate, sodium monophosphate, dibasic sodium phosphate, and tribasic sodium phosphate may be used. The mixed solution obtained by adding the molten salt and the dispersing agent to the mixed solution in which aluminum hydroxide is precipitated has a strong alkali of pH 12 to 14 due to caustic soda in the mixed solution.

Conventional aluminum hydroxide production process using general aluminum hydroxide precipitates aluminum hydroxide and then separates and discards caustic soda, a waste solution, but the present invention uses caustic soda as a mother liquor for dissolving molten salt. When caustic soda is used as a mother liquor, there is no need to hydrolyze water to dissolve the molten salt, and the added flux is deposited on the surface of aluminum hydroxide in the solution, so 3 to 7 times higher flux than aluminum hydroxide is added. A flux of 60 to 70% less than the conventional plate-shaped alumina manufacturing process can be added.

The neutralizing agent is added to neutralize the pH of the mixed solution in which the flux is mixed (hereinafter abbreviated as the flux mixture) (S120).

As described above, a neutralizing agent is added to the flux mixture containing caustic soda and having a strong alkali of pH 12 to neutralize the pH to 6-8. By neutralizing the pH in this way, an environment in which particles can grow is created. At this time, sulfuric acid, hydrochloric acid or nitric acid having a high concentration of 90% or more may be used as a neutralizing agent. If the concentration of the neutralizing agent is too low, the manufacturing volume may increase and drying time may increase.

The neutralization solution is dried (S125).

The neutralized solution in which the pH of the flux mixture is neutralized is dried to produce an aluminum hydroxide compound. When drying the neutralization liquid, the neutralization liquid may be dried within a temperature range of 110 to 200°C using a hot air dryer or a distillation dryer. Drying may proceed until the moisture in the neutralization solution is within 1%. If the neutralizing liquid is not dried, the neutralizing liquid is completely dried because the water particles cause aggregation of plate-like alumina and may cause abnormal particle growth.

The aluminum hydroxide compound is heat treated (S130).

The aluminum hydroxide compound is pulverized to a size of 1 cm or less in diameter to form a powder. When grinding, a roll mill or a ball mill may be used as a grinder. Although there is no problem in heat treatment even if the aluminum hydroxide compound is not made into a powder form, it is easy to work because a large amount can be heat treated at a time, and even heat can be applied to the aluminum hydroxide compound evenly. The powdered aluminum hydroxide compound is placed in a ceramic crucible and heat-treated in a normal atmosphere. When the aluminum hydroxide compound is heat-treated, the volume of the flux contained in the aluminum hydroxide compound is increased by heat treatment, so that the ceramic crucible is often damaged. The volume of increasing flux is proportional to the amount of flux added to the aluminum hydroxide compound. At this time, compared to the conventional plate-shaped alumina production process of heat treatment by adding 300 g to 700 g of flux per 100 g of aluminum hydroxide, the volume of the flux is 60 to 70% less flux is added to the plate-shaped alumina production process of the present invention. Does not increase significantly. Therefore, during the heat treatment of the aluminum hydroxide compound, damage to the heat treatment container such as a ceramic crucible can be prevented.

When the powdered aluminum hydroxide compound is heat-treated, the aluminum hydroxide compound is grown in the form of plate-shaped alumina. At this time, the heat treatment may be performed for 1 to 4 hours by dividing the temperature section into a first temperature section, a second temperature section, and a third temperature section. And each temperature section can be formed by raising the temperature by 3 ~ 5 ℃. This is because the melting temperature of each flux contained in the aluminum hydroxide compound is different from each other, so that the flux is divided by dividing the temperature section to heat the flux. Here, the first temperature section may be 200 to 300°C, the second temperature section may be 700 to 900°C, and the third temperature section may be 1100 to 1300°C. In more detail, heat treatment is performed in the first temperature section to blow out the aluminum hydroxide internal crystal water and water molecules contained in the aluminum hydroxide compound, and the temperature is raised in the first temperature section and heat-treated in the second temperature section to melt and melt the hydroxide. The flux adheres to the aluminum particles. Then, by raising the temperature in the second temperature section and heat-treating the third temperature section, the aluminum hydroxide particles are grown in the form of plate-shaped alumina by fluxing. The flux is melted at each temperature section and adheres to the aluminum hydroxide particles, thereby controlling the particle growth so that the aluminum hydroxide particles grow only in the transverse direction, so that aluminum hydroxide can grow in the form of plate-shaped alumina.

When the grown plate-shaped alumina is cooled, an agglomerated powder containing plate-shaped alumina particles is formed.

The flux and the fine particles are removed through filtration (S135).

The agglomerated plate alumina powder is separated by adding a liquid such as hot water to the agglomerated powder containing plate-shaped alumina particles. The agglomerated powder is formed by heat-treating and cooling the aluminum hydroxide compound, and the cohesive strength of the agglomerated powder containing plate-like alumina particles is proportional to the amount of the flux added to the aluminum hydroxide compound. At this time, since the amount of 60 to 70% less flux is added to the plate-shaped alumina production process of the present invention than the conventional plate-shaped alumina production process, the cohesive strength of the agglomerated powder is weakened. Therefore, the agglomerated powder of the present invention is more easily released into a liquid such as hot water, so that the agglomerated powder can be easily separated from a heat treatment vessel such as a ceramic crucible. At this time, when using hot water as a liquid, the temperature of the hot water is preferably 60 to 100°C, which can dissolve a water-soluble flux. When the plate-shaped alumina powder to which the liquid is added is stirred for 2-3 hours, it is made into a mixed liquid state in which the plate-shaped alumina particles are dispersed. The plate-shaped alumina particles include a water-soluble flux that is easily soluble in water and fine particles having a particle size of 5 μm or less, which is poor in glossiness, among the plate-shaped alumina particles. In order to remove the water-soluble flux and fine particles, the mixed solution is filtered using a filtration device. When the mixed solution is filtered with a filtration device, a cake in which water-soluble flux and fine particles are removed is produced. As one of the filtering devices, a filter press having a porosity of 1 to 5 μm can be used.

The cake is slurried, and plated alumina particles and twins aggregated in the slurry are decomposed (S140).

A little water is added to the cake and stirred to make the cake slurry. Thereafter, the slurry is put in a grinder, and the grinder decomposes a twin agglomerated and agglomerated plate alumina particles in the slurry for a predetermined time. The preset decomposition time is preferably 1 hour to 1 hour 30 minutes. This is because when the plate-shaped alumina particles of the slurry are decomposed for a predetermined time or longer, cracking of the plate-shaped alumina particles occurs, and when decomposed for a predetermined time or less, there is no improvement effect of aggregated particles and twins.

Here, twin crystal refers to a plate-shaped alumina particles that are crossed and grown. Since the twin particles give a rough feeling when used as a pigment, it is preferable to separate the plate-shaped alumina particles that are grown by crossing the twins. As a pulverizer, a wet bead mill using zirconia beads having a diameter of 0.3 to 1.0 Φ may be used. In the case of using a wet bead mill, when a slurry is put into a bead mill and decomposed, twins and some aggregated particles can be decomposed. In addition, the plate-shaped particles decomposed by a wet bead mill have very few twin crystals, and the flowability and dispersibility of the particles are remarkably good.

After decomposing the twins and agglomeration of the slurry, the slurry is dried and plate-shaped particles having a certain particle size are removed (S145).

When drying the slurry, the plate-shaped alumina particles may aggregate again because of the water contained in the slurry. To prevent this, commercially available wet and dry cake dryers may be used. A wet dryer cake dryer is used to dry the slurry at an outlet temperature of 130 to 250°C. When the slurry is dried with a wet-drying cake dryer, plate-like alumina having a constant particle size is produced. When drying the slurry, various dryers capable of preventing aggregation of the slurry can be used, so the dryer is not limited to a wet and dry cake dryer.

After drying the slurry, the resulting plate-shaped alumina is removed through a filtration device to remove fine particles of plate-shaped alumina having a particle size of 5 μm or less. A bag filter may be used as a filtering device, but is not limited thereto. After removing the fine particles by the filtration device, the fine particles of 5 μm or less and the large particles of 50 μm or more, which adversely affect the pearl gloss, are removed from the dried plate-shaped alumina product. An air flow classifier may be used to remove microparticles of 5 μm or less and large particles of 50 μm or more. The airflow classifier can collect the heavy ones by sinking the heavy ones and float the light ones by dropping air with a constant pressure. Therefore, it is possible to collect and remove fine particles of 5 μm or less and large particles of 50 μm or more, respectively. In addition, only a product having a desired particle size can be collected and used in a plate-shaped alumina product having a particle size of 5-50 μm.

Through the above-described manufacturing method, it is possible to manufacture excellent quality plate-shaped alumina having a narrow particle size distribution of 5 to 50 μm, a thickness of 0.1 to 0.5 μm, and a square ratio of 50 to 200.

<Experimental Example 1>

(1) Preparation of sodium aluminate solution

General aluminum hydroxide (Wet-Al(OH) ₃ ) 66.2g, caustic soda 50% aqueous solution 84.5g, ultrapure water 94.5ml in 500ml pressure vessel, stirred, heated to 150℃ and pressure of 5 atm for 2~3 hours To maintain. Accordingly, aluminum hydroxide was completely dissolved in caustic soda to prepare a 200 ml sodium aluminate solution having a caustic soda (Na ₂ CO ₃ ) concentration of 280 g/L and A/C 0.75.

(2) Adding SEED and depositing aluminum hydroxide

The temperature of the prepared sodium aluminate solution was lowered to 60° C. or less, and 6.62 g of aluminum hydroxide having a particle size of 0.3 μm was added, followed by stirring to precipitate for 3 days. A/C after the completion of precipitation was measured as 0.25, and as a result of particle size analysis, 1 μm of aluminum hydroxide was deposited on the sodium aluminate solution.

(3) Mixing flux and preparing neutralization solution

20 g of sodium sulfate and 15 g of sodium carbonate were added to the sodium aluminate solution where aluminum hydroxide was precipitated, and 0.5 g of sodium hexametaphosphate was added and stirred for 1 hour. As a result of checking the pH of the solution, since the pH of the solution appears to be 14, the pH is neutralized to 7 using sulfuric acid having a high concentration of 95%.

(4) neutralization liquid drying

The liquid neutralization solution prepared by mixing the flux and neutralizing the pH is put in a stainless tray and placed in a box type general dryer. And the dryer heats the liquid neutralization solution to 110°C for 48 hours. Thus, an aluminum hydroxide compound in which the liquid neutralization liquid is completely dried is produced.

(5) grinding and heat treatment

The aluminum hydroxide compound is put in a roll mill and pulverized into small powders having a diameter of 1 cm or less. Then, the aluminum hydroxide compound that has been pulverized to form a powder is placed in a 1L alumina crucible, and the alumina crucible is placed in a box-type general electric furnace. Then, the temperature was raised to 3°C/min to 250°C and maintained for 3 hours, and the temperature was raised to 5°C/min to 850°C and maintained for 2 hours, and then raised to 5°C/min to 1250°C and maintained for 4 hours, and then naturally cooled at room temperature.

(6) Obtaining plate-shaped alumina

The aluminum hydroxide compound in powder form is grown into plate-shaped alumina by heat treatment. At this time, since the plate-shaped alumina is still attached to the alumina crucible, the plate-shaped alumina is separated from the alumina crucible. Then, the separated plate-shaped alumina is dispersed by hot water at 60°C or higher, and the water-soluble flux mixed with the hot water is removed through a filter. The plated alumina from which the flux has been removed is dispersed with a 10% concentration of sulfuric acid solution to remove aggregated plated alumina particles and salts remaining on the particle surface. Subsequently, when the plate-like alumina from which the flux and salt have been removed is dried at 110°C, 47 g of plate-like alumina having an excellent squareness ratio of 50 to 200 and having good dispersibility in water is produced. The resulting plate-shaped alumina has a particle size of 5-50 μm and a thickness of 0.1-0.5 μm.

<Experimental Example 2>

(1) Adding SEED

Prepared in the same manner as in Experimental Example 1. However, unlike Experimental Example 1, Experimental Example 2 was added with the seed (SEED) changed to 25.4 g of aluminum sulfate. The plate-shaped alumina prepared by Experimental Example 2 has a square ratio of 50 to 190, and has good dispersibility in water. The plate-shaped alumina of Example 2 has a particle size of 5 to 51 μm and a thickness of 0.1 to 0.5 μm.

<Experimental Example 3>

(1) Adding SEED

Prepared in the same manner as in Experimental Example 1. However, unlike Experimental Example 1, Experimental Example 3 is changed into 20 g of aluminum ammonium sulphate GEL, which is directly prepared from seeds. Aluminum ammonium sulphate GEL is prepared by dissolving aluminum hydroxide in sulfuric acid and neutralizing it with ammonia water. The plate-shaped alumina prepared by Experimental Example 3 had a squareness ratio of 50 to 210, which was superior to Experimental Example 1 and Experimental Example 2, and showed good dispersibility in water.

<Experimental Example 4>

(1) Preparation of flux mixture and neutralization solution

Prepared in the same manner as in Experimental Example 1. However, unlike Experimental Example 1, Experimental Example 4 added 20 g of potassium carbonate and 15 g of sodium carbonate to the sodium aluminate solution in which aluminum hydroxide was precipitated, and 0.5 g of sodium hexametaphosphate was added and stirred for 1 hour. The plate-shaped alumina prepared by Experimental Example 4 had an excellent squareness ratio of 45 to 180, and showed good dispersibility in water.

<Comparative Example 1>

(1) Adding SEED

Prepared in the same manner as in Experimental Example 1. However, unlike Experimental Example 1, Comparative Example 1 was added with SEED changed to 6.62 g of 20 μm aluminum hydroxide. The plate-shaped alumina prepared by Comparative Example 1 had a thick particle thickness, so that the squareness ratio was not good at 10 to 130, and poor dispersibility was exhibited.

<Comparative Example 2>

(1) Preparation of flux mixture and neutralization solution

Prepared in the same manner as in Experimental Example 1. However, unlike Experimental Example 1, Comparative Example 2 was added with 200 g of sodium sulfate and 100 g of sodium carbonate to the sodium aluminate solution in which aluminum hydroxide was precipitated, and 0.5 g of sodium hexametaphosphate was added and stirred for 1 hour. The plate-shaped alumina prepared by Comparative Example 2 was not easily separated from the crucible due to heavy aggregation, and a large amount of twin particles and large particles of 100 μm or more were generated, resulting in poor dispersibility.

The table below shows the particle size and squareness ratio of the plate-shaped alumina prepared by each experimental example and comparative example.

Referring to the above table, as in Comparative Example 1, when aluminum oxide having a particle size of 0.1 to 1.0 μm or more is used as a seed, plate-like alumina having irregular particle size distribution and poor particles is prepared. Therefore, when adding a seed to the sodium aluminate supersaturated solution, it is preferable to use aluminum hydroxide having a size of 0.1 to 1.0 μm as a seed.

Referring to the above table, aluminum hydroxide is precipitated as in Comparative Example 2, and when the molten salt is excessively added to the mixed solution present as particles, plate-shaped alumina having irregular particle size distribution of 1 to 135 μm and poor particle size is prepared. Therefore, when aluminum hydroxide is precipitated and molten salt is added to the mixed solution present as particles, it is preferable to add 40 to 80% based on the amount of aluminum hydroxide dissolved in the sodium aluminate supersaturated solution.

2 is a view showing a scanning electron microscope observation result of the plate-shaped alumina powder according to an embodiment of the present invention, Figure 3 is a graph showing the particle size analysis results of the plate-shaped alumina powder according to an embodiment of the present invention, Figure 4 is a graph showing the results of XRD (X-Ray Diffraction) analysis of the plate-shaped alumina powder according to an embodiment of the present invention.

2 to 4, the plate-shaped alumina prepared according to an embodiment of the present invention has a particle size in the range of 5 to 50 μm, and on average, appears to have a particle size of 20 μm.

Although FIG. 1 describes that each process is executed sequentially, this is merely illustrative of the technical idea of an embodiment of the present invention. In other words, a person skilled in the art to which one embodiment of the present invention pertains may execute or change one or more of the processes described in each drawing without departing from the essential characteristics of one embodiment of the present invention. Since the process can be applied in various modifications and variations by executing in parallel, FIG. 1 is not limited to the time series order.

Meanwhile, the processes illustrated in FIG. 1 may be implemented as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data readable by a computer system is stored. That is, the computer-readable recording medium includes a storage medium such as a magnetic storage medium (eg, ROM, floppy disk, hard disk, etc.) and an optical reading medium (eg, CD-ROM, DVD, etc.). In addition, the computer-readable recording medium can be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

The above description is merely illustrative of the technical idea of the present embodiment, and those skilled in the art to which this embodiment belongs will be capable of various modifications and variations without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical spirit of the present embodiment, but to explain, and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be interpreted by the claims below, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present embodiment.

Claims (5)

In order to promote the precipitation of aluminum hydroxide particles, the process of obtaining a solution by dissolving aluminum hydroxide in caustic soda solution so that aluminum hydroxide has a weight ratio of 0.6 to 0.8 (Al ₂ O ₃ /Na ₂ CO ₃ ) based on caustic soda ;
In order to allow the dissolved aluminum hydroxide to adhere and grow into particles and precipitate, a seed is added to the solution and stirred, and the weight ratio of aluminum hydroxide based on the caustic soda (Al ₂ O ₃ /Na ₂ CO ₃ ) To obtain a mixed solution by depositing aluminum hydroxide until it becomes 0.3;
A flux mixing process in which 0.5 to 2% of the weight of aluminum hydroxide dissolved in the mixed solution is added and 40 to 80% of the weight of dissolved aluminum hydroxide is added as a flux and a flux;
After the flux mixing process, a neutralizing process to generate a neutralizing solution by adding a neutralizing agent to the mixed solution;
A drying process of drying the neutralization solution to produce an aluminum hydroxide compound;
The aluminum hydroxide compound is pulverized to a predetermined size or less to form a powder, and then heat-treated at 200 to 300°C so that the aluminum hydroxide internal crystal water and water molecules evaporate, and the flux is melted and heated to adhere to the aluminum hydroxide particles. Heat treatment to ℃, heat-up so that the receiving aluminum particles grow in the form of plate-shaped alumina by fluxing, heat-treating the aluminum hydroxide compound in powder form to 1100 to 1300 °C, and then cooling to produce a powder containing plate-shaped alumina particles process;
A filtration process in which particles having a predetermined size and flux contained in the plate-shaped alumina particles are filtered to produce a cake;
A decomposition process in which the cake is slurried and decomposed plated alumina particles aggregated in the slurry; And
Drying the slurry (Slurry), and includes a particle removal process for removing the plate-shaped alumina particles having a particle size of 5㎛ or less from the dried slurry (Slurry),
The seed is added 5 to 10% of the weight of dissolved aluminum hydroxide,
The neutralizing agent is sulfuric acid, hydrochloric acid or nitric acid. delete delete delete delete

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