KR20230081601A - Device for manufacturing magnesium oxide - Google Patents

Abstract

The present application relates to an apparatus for producing magnesium oxide, a method for producing magnesium oxide using the same, magnesium oxide produced using the same, and uses of magnesium oxide. According to the apparatus for producing magnesium oxide, the method for producing magnesium oxide using the same, and the magnesium oxide produced using the same, magnesium oxide may have high thermal conductivity at a low price, a small spherical particle size, and a dense structure. The magnesium oxide can be used as a heat dissipation filler.

Description

Magnesium oxide manufacturing device {DEVICE FOR MANUFACTURING MAGNESIUM OXIDE}

The present application relates to a magnesium oxide manufacturing apparatus, a magnesium oxide manufacturing method using the same, magnesium oxide manufactured using the same, and a use of the magnesium oxide.

Magnesium oxide (MgO) has thermal conductivity about 2 to 3 times higher than that of aluminum oxide (Al ₂ O ₃ ), Compared to expensive high thermal conductivity materials such as silicon carbide (SiC) and boron nitride (BN), it has a very good thermal conductivity performance compared to the price.

Accordingly, attempts have been made to replace aluminum oxide, which is used as a filler for heat dissipating materials, with magnesium oxide. The most important conditions that a heat dissipation filler must have are not only economically low price and high thermal conductivity, but also dense spherical particles with a particle diameter of about 150 μm or less to be densely packed in a polymer resin. A spray drying process is well known as the most economical process for producing large quantities of spherical particles having a diameter of 150 μm or less in a typical ceramic manufacturing process. In the spray drying process, after preparing a suspension in which ceramic powder particles are evenly dispersed in a liquid, the suspension is continuously formed into spherical suspension droplets having a diameter of several tens to hundreds of μm through a droplet generator called an atomizer. It refers to a process of manufacturing spherical solid powder masses, that is, granules, with a diameter of tens to hundreds of μm by causing evaporation of liquid components from the droplets by blowing high-temperature gas into the container in which the droplets are sprayed. Therefore, it is judged that the most economical and mass-producing process for producing magnesium oxide, which is promising as a heat dissipating filler, into spherical particles of about 150 μm or less is possible by adopting this spray drying process.

However, when magnesium oxide comes into contact with moisture or water, there is a problem in which a hydration reaction of MgO + H ₂ O = Mg(OH) ₂ occurs, so water, which is most often used as a solvent for preparing a suspension in a conventional ceramic spray drying process, is used. There is a problem that cannot be

In order to overcome this problem, conventionally, a non-aqueous spray drying method using an alcohol-based solvent instead of water as a solvent for preparing a suspension has been adopted. However, in the non-aqueous spray drying process using an organic solvent, an explosion-proof spray dryer is used to prevent explosion of a suspension made of a flammable organic solvent for safety. Such explosion-proof spray dryers are expensive compared to spray dryers used in water-based spray drying processes using water. In addition, the price of high-purity organic solvents consumed in large quantities in mass production is also very expensive compared to distilled water in water-based processes. Moreover, organic solvents have a degree of toxicity depending on the type, but most of them are harmful, so if possible, an aqueous process is more preferable than a non-aqueous process. Therefore, there is a need for a magnesium oxide manufacturing apparatus to compensate for these disadvantages.

The present application provides an apparatus for producing magnesium oxide capable of producing dense magnesium oxide having high thermal conductivity and a small spherical diameter at a low price, a method for producing magnesium oxide using the same, magnesium oxide manufactured using the same, and the magnesium oxide is to provide the use of

In order to solve the above problems, the apparatus for producing magnesium oxide of the present application includes a mixing unit for preparing a suspension by mixing distilled water, magnesium oxide precursor powder, and additives; a spray drying unit for preparing granules by spraying and drying the suspension mixed in the mixing unit; and a heat treatment unit for forming magnesium oxide by heat-treating the granules prepared in the spray drying unit.

The magnesium oxide precursor powder may be magnesium hydroxide (Mg(OH) ₂ ) powder.

In addition, the magnesium oxide precursor powder may be included in 25 parts by weight to 70 parts by weight based on 100 parts by weight of the suspension.

In addition, the additive may include at least one selected from a dispersant, a sintering aid, and a thermal property improving agent.

In addition, the dispersant may be included in an amount of 0.1 part by weight to 10 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder.

In addition, the sintering aid may be included in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder.

In addition, the thermal property improver may be included in an amount of 0.05 parts by weight to 0.45 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder.

In addition, the additive may not include at least one selected from a binder and a plasticizer.

In addition, the suspension may have a solid content of 15 vol% to 50 vol%.

In addition, the spray drying unit may simultaneously spray and dry the suspension.

In addition, the droplets sprayed from the spray drying unit may have a spherical shape with a diameter of 10 μm to 200 μm.

In addition, the spray drying unit includes an inlet through which hot air is introduced and an outlet through which hot air is discharged, the temperature of the hot air introduced into the spray drying unit is 120° C. to 180° C., and the hot air discharged to the outside of the spray drying unit is The temperature may be 50 °C to 100 °C.

In addition, the heat treatment may be performed at 1300 ° C to 1450 ° C for 5 minutes to 120 minutes.

In addition, the magnesium oxide formed through the heat treatment may have a relative density of 95% or more.

In addition, the magnesium oxide formed by the heat treatment may have a spherical particle diameter of 5 μm to 150 μm.

In addition, the magnesium oxide formed by the heat treatment may have a thermal conductivity of 40 W/m·K to 65 W/m·K.

In addition, the magnesium oxide manufacturing apparatus may further include a particle size adjusting unit for adjusting the size of the aggregate when the granules heat-treated in the heat treatment unit are aggregated between the granules to form aggregates.

In addition, the method for producing magnesium oxide of the present application relates to a method for producing magnesium oxide using the magnesium oxide producing apparatus, comprising a mixing step of preparing a suspension by mixing distilled water, a magnesium oxide precursor powder, and an additive; a spray drying step of spraying and drying the suspension mixed in the mixing step to prepare granules; and a heat treatment step of heat-treating the granules prepared in the spray drying step to form magnesium oxide.

In addition, in the spray drying step, spraying and drying of the suspension may be performed simultaneously.

In addition, the method for preparing magnesium oxide may further include a particle size control step of adjusting the size of the agglomerates when the heat-treated granules are aggregated between the granules in the heat treatment step to form agglomerates.

In addition, the magnesium oxide of the present application is manufactured using the magnesium oxide manufacturing apparatus.

In addition, the heat dissipating filler of the present application includes the magnesium oxide.

According to the magnesium oxide manufacturing apparatus of the present application, the magnesium oxide manufacturing method using the same, and the magnesium oxide manufactured using the same, it has high thermal conductivity at a low price, has a small spherical diameter, and can have a dense structure. This magnesium oxide can be used as a heat radiation filler.

1 is a diagram exemplarily shown to explain a process for manufacturing magnesium oxide using a magnesium oxide manufacturing apparatus according to an embodiment of the present application.
FIG. 2 is a photograph of the magnesium hydroxide granules of Example 1 taken with a scanning electron microscope and magnified 500 times.
FIG. 3 is a photograph of the magnesium hydroxide granules of Example 1 taken with a scanning electron microscope and magnified 1500 times.
4 is a photograph magnified 100 times by taking magnesium hydroxide granules of Comparative Example 1 with a scanning electron microscope.
5 is a photograph magnified 1000 times by taking magnesium hydroxide granules of Comparative Example 1 with a scanning electron microscope.
6 is a photograph of magnesium oxide particles of Example 1 taken with a scanning electron microscope and magnified 500 times.
7 is a photograph magnified 1500 times by taking the magnesium oxide particles of Example 1 with a scanning electron microscope.
8 is a photograph of magnesium oxide particles of Example 2 taken with a scanning electron microscope and magnified 500 times.
9 is a photograph magnified 1500 times by taking the magnesium oxide particles of Example 2 with a scanning electron microscope.
10 is a photograph of magnesium oxide particles of Comparative Example 2 taken with a scanning electron microscope and magnified 200 times.
FIG. 11 is a photograph magnified 500 times, taken with a scanning electron microscope, in order to analyze the primary granulation defects of the magnesium oxide particles of Example 2. FIG.
12 is a photograph magnified 1500 times, taken with a scanning electron microscope, in order to analyze the primary granulation defects of the magnesium oxide particles of Example 2.
FIG. 13 is a photograph magnified 500 times, taken with a scanning electron microscope, to analyze primary granulation defects of magnesium oxide particles before sieving in Example 3. FIG.
14 is a photograph magnified 1500 times, taken with a scanning electron microscope, to analyze primary granulation defects of magnesium oxide particles before sieving in Example 3.
15 is a photograph magnified 500 times by scanning electron microscopy to analyze primary granulation defects of magnesium oxide particles after sieving in Example 3;
16 is a photograph magnified 1500 times by scanning electron microscopy to analyze primary granulation defects of magnesium oxide particles after sieving in Example 3;
17 is a photograph magnified 500 times, taken with a scanning electron microscope, in order to analyze secondary granule defects of the magnesium oxide particles of Example 2;
18 is a photograph magnified 1500 times, taken with a scanning electron microscope, in order to analyze secondary granule defects of the magnesium oxide particles of Example 2.
19 is a photograph magnified 500 times, taken with a scanning electron microscope, in order to analyze secondary granule defects of the magnesium oxide particles of Comparative Example 1.
20 is a photograph magnified 2000 times, taken with a scanning electron microscope, in order to analyze the secondary granulation defects of the magnesium oxide particles of Comparative Example 1.
21 is a photograph magnified 200 times, taken with a scanning electron microscope, in order to analyze secondary granule defects of the magnesium oxide particles of Comparative Example 2;

Hereinafter, the magnesium oxide manufacturing apparatus of the present application will be described with reference to the accompanying drawings, and the accompanying drawings are exemplary, and the magnesium oxide manufacturing apparatus of the present application is not limited to the accompanying drawings.

1 is a diagram exemplarily shown to explain a process for manufacturing magnesium oxide using a magnesium oxide manufacturing apparatus according to an embodiment of the present application. As shown in FIG. 1 , the apparatus for producing magnesium oxide includes a mixing unit 10 , a spray drying unit 20 and a heat treatment unit 30 . According to the magnesium oxide manufacturing apparatus of the present application, it can have high thermal conductivity at a low price, have a small spherical diameter, and have a dense structure.

The mixing part is a part for preparing a suspension, and is performed by mixing distilled water, magnesium oxide precursor powder, and additives. Specifically, the mixing may be performed by first mixing the distilled water and additives in a container, and then secondarily mixing by adding magnesium oxide precursor powder to the mixture. For example, as the mixing method, various grinding and mixing methods commonly used in ceramic processes may be used, and further examples include stirring, ultrasonication, ball milling, and attrition. Attrition-milling, bead-milling, vibratory milling, or planetary milling may be used.

In one embodiment, the mixing is performed using ball milling, for 12 to 24 hours using a ball having a diameter of 5 to 10 mm, for example, a zirconia ball, for sufficient reduction in size and uniform mixing of the magnesium oxide precursor powder. This can be done through ball milling.

The magnesium oxide precursor powder may be magnesium hydroxide (Mg(OH) ₂ ) powder. By using the above-described powder as the magnesium oxide precursor powder, a water-based spray drying process can be used because a hydration reaction does not occur even when in contact with the distilled water.

The magnesium oxide precursor powder may be included in 25 parts by weight to 70 parts by weight based on 100 parts by weight of the suspension. Specifically, the magnesium oxide precursor powder is 30 parts by weight to 68 parts by weight, 35 parts by weight to 66 parts by weight, 40 parts by weight to 64 parts by weight, 45 parts by weight to 62 parts by weight, 50 parts by weight to 100 parts by weight of the suspension It may be included in 60 parts by weight or 55 parts by weight to 60 parts by weight. Since the magnesium oxide precursor powder is included in the above-mentioned amount in the suspension, a good spray drying process can be performed, and the production yield of granules having an appropriate diameter can be improved. On the other hand, when the content of the magnesium oxide precursor powder is less than the above range, the diameter of the prepared granules may decrease as well as the yield of the granules may decrease. In addition, when the content of the magnesium oxide precursor powder exceeds the aforementioned range, the viscosity of the suspension increases, making spray drying impossible.

In addition, the additive may include at least one selected from a dispersant, a sintering aid, and a thermal property improving agent.

Specifically, as the dispersant, it is possible to use various water-based dispersants commonly used in preparing an aqueous ceramic suspension. For example, ammonium salt of polycarboxylic acid (Sannopco 5468CF), ammonia water (NH ₄ OH), Polyoxyethylene nonylphenyl ether, Branched phosphate (Solvay Rhodafac RE-610), DISPERBYK-194 or DISPERBYK-6230 may be used.

The content of the dispersant may be 0.1 to 10 parts by weight, 1 to 9 parts by weight, 3 to 8 parts by weight, or 5 to 7 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. By including the dispersant in the above-mentioned content, the dispersibility of the magnesium hydroxide powder particles distributed in the suspension can be improved and the viscosity can be reduced accordingly, thereby preparing a high-concentration, low-viscosity suspension.

As the sintering aid, it is possible to use any material known to promote sintering of magnesium oxide, for example, titanium oxide (TiO ₂ ), niobium (Nb ₂ O ₅ ), zirconia (ZrO ₂ ), oxide Gallium (Ga ₂ O ₃ ), dimanganese trioxide (Mn ₂ O ₃ ), vanadium pentoxide (V ₂ O ₅ ), tantalum pentoxide (Ta ₂ O _5- ), antimony pentoxide (Sb ₂ O ₅ ), yttrium oxide (Y ₂ O ₃ ), Europium Oxide (Eu ₂ O ₃ ), Abium Oxide (Er ₂ O ₃ ), Boron Trioxide (B ₂ O ₃ ), Iron Oxide (Fe ₂ O ₃ ), Tin Oxide (SnO ₂ ) , manganese dioxide (MnO ₂ ), silicon dioxide (SiO ₂ ) or alumina (Al ₂ O ₃ ) may be used.

The content of the sintering aid may be 0.1 to 0.5 parts by weight or 0.2 to 0.4 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. By including the sintering aid in the above-mentioned content, it is possible to promote the densification of magnesium oxide.

As the thermal property improver, it is possible to use any material known to improve the thermal conductivity of magnesium oxide. For example, niobium (Nb ₂ O ₅ ), which simultaneously serves as a sintering aid and improves thermal properties, Titanium oxide (TiO ₂ ), zirconia (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), abium oxide (Er ₂ O ₃ ) or alumina (Al ₂ O ₃ ) can be used. can

The amount of the thermal properties improver may be 0.05 parts by weight to 0.45 parts by weight, 0.1 parts by weight to 0.4 parts by weight, 0.15 parts by weight to 0.35 parts by weight, or 0.2 parts by weight to 0.3 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. It may be advantageous in terms of increasing the thermal conductivity of magnesium oxide by including the thermal properties improving agent in the above-described content.

In one example, the additive may not include at least one selected from a binder and a plasticizer. Specifically, in order to ensure that the molded body produced when granules normally manufactured by spray drying are molded by a method such as press molding during the manufacture of ceramic suspension is not damaged and can sufficiently withstand stress and deformation during subsequent processes. Organic additives such as binders and plasticizers may be additionally added. However, as in the present application, when a molded article manufacturing process is not required, additives other than the above additives, for example, at least one organic additive selected from a binder and a plasticizer do not need to be additionally added.

The suspension may have a solid content of 15 vol% to 50 vol%. Specifically, the solid content of the suspension may be 20 vol% to 45 vol%, 25 vol% to 40 vol%, or 30 vol% to 40 vol%. Since the suspension has the above-described solid content, it may be advantageous to manufacture granules in the spray drying unit. On the other hand, when the suspension has a solid content less than the above-mentioned, a problem in that the diameter of the granules produced after spray drying in the spray drying unit becomes small may occur. In addition, when the suspension has a solid content higher than the above-mentioned content, the viscosity of the suspension becomes too high, and spraying of liquid droplets becomes difficult.

The spray drying unit is a part for preparing granules, and is performed by spraying and drying the suspension mixed in the mixing unit. In the present specification, granules refer to secondary particles made by weakly binding very fine primary particles. For example, the primary particles may have a diameter of 1 μm or less, and the secondary particles may have a diameter of greater than 1 μm to less than 1000 μm.

For example, the spraying may be performed using a nozzle type sprayer or a rotating disk type sprayer. At this time, when the spray drying unit includes a nozzle-type sprayer, the spray pressure of the nozzle, the supply speed of the suspension to the spray drying unit, the temperature of the hot air entering the spray drying unit and the temperature of the hot air exiting the outside, and the supply speed of the hot air are controlled. Thus, the droplet and granule diameter, yield, and shape defect generation rate can be controlled. In addition, when the spray drying unit includes a disc-shaped atomizer, the rotational speed and diameter of the disc, the supply speed of the suspension to the spray drying unit, the temperature of the hot air entering the spray drying unit and the temperature of the hot air exiting the outside, and the supply speed of the hot air It is possible to control the droplet and granule diameter, yield, and shape defect occurrence rate by adjusting.

In one example, the spray drying unit may simultaneously spray and dry the suspension. Specifically, the suspension may be sprayed and dried simultaneously through a spray drying unit. The spray drying unit simultaneously sprays and dries the suspension, thereby drying and granulating the suspension in the form of droplets within a very short time, for example, within 1 second, thereby enabling economical mass production of granules. .

Droplets sprayed from the spray drying unit may have a spherical shape with a diameter of 10 μm to 200 μm. Specifically, the droplets sprayed from the spray drying unit may have a spherical shape with a diameter of 15 μm to 190 μm, 20 μm to 180 μm, or 25 μm to 170 μm. At this time, the droplets may be in a state of a sprayed suspension before being dried in the spray drying unit. Since the droplets sprayed from the spray drying unit have a spherical shape with the aforementioned diameter, the size of granules formed after drying the droplets may have a size of 5 μm to 150 μm. Due to this, the granules have good fluidity, and thus, a phenomenon in which the granules agglomerate with each other during the subsequent process can be minimized. In this specification, the term "diameter" may mean the size of a spherical particle.

The spray drying unit may include an inlet (not shown) through which hot air is introduced and an outlet (not shown) through which hot air is discharged in order to dry the suspension. For example, the temperature of the hot air introduced into the spray drying unit is 120 ° C to 180 ° C, 130 ° C to 170 ° C, or 140 ° C to 160 ° C, and the temperature of the hot air discharged to the outside of the spray drying unit is 50 ° C to 160 ° C. 100 °C, 60 °C to 90 °C or 70 °C to 80 °C. By performing the drying under the above conditions, the yield of granules having a good spherical shape and diameter can be improved.

The heat treatment unit sinters magnesium hydroxide granules to form magnesium oxide, and is performed by heat-treating the granules prepared in the spray drying unit. In this specification, magnesium oxide formed by heat treatment may also be referred to as sintered granules.

In one example, the heat treatment may be performed at 1300 °C to 1450 °C for 5 minutes to 120 minutes. Specifically, the heat treatment may be performed at 1400 °C to 1450 °C for 30 minutes to 90 minutes. The granules may be thermally decomposed and densified by being heat-treated under the conditions described above in the heat treatment unit.

The magnesium oxide formed through the heat treatment may have a relative density of 95% or more. Magnesium oxide formed through the heat treatment may achieve densification by having the above-described relative density.

In addition, the magnesium oxide formed by the heat treatment may have a spherical shape with a diameter of 5 μm to 150 μm. Specifically, the diameter of the spherical magnesium oxide particles formed by the heat treatment may be 10 μm to 120 μm, 20 μm to 90 μm, or 30 μm to 60 μm. The magnesium oxide formed through the heat treatment has a spherical shape having the aforementioned diameter, so that it may be used as a heat dissipation filler.

In addition, the magnesium oxide formed through the heat treatment may have a thermal conductivity of 40 W/m·K to 65 W/m·K. Specifically, the thermal conductivity of the magnesium oxide formed through the heat treatment may be 45 W/m·K to 60 W/m·K. The magnesium oxide formed through the heat treatment has the above-described thermal conductivity, and thus may be used as various heat dissipation fillers.

In one example, the magnesium oxide manufacturing apparatus may further include a particle size control unit (not shown). The particle size control part is a part that controls the size of the aggregate when the granules heat-treated in the heat treatment unit are aggregated between the granules to form aggregates. Specifically, in the process of heat-treating the granules in the heat treatment unit, densification occurs simultaneously in the contact surface between the granules as well as the densification inside the granules, and agglomerates may be formed by the necking phenomenon to form magnesium oxide particles having a desired diameter. To manufacture, the size of the particles can be controlled. For example, in the particle size control unit, the size of the particles, that is, the diameter, can be controlled by gently pulverizing the agglomerates using a mortar or the like and sieving them.

This application also relates to a method for preparing magnesium oxide. An exemplary method for producing magnesium oxide relates to a method for producing magnesium oxide using the above-described apparatus for producing magnesium oxide. Therefore, since the details of the magnesium oxide manufacturing method to be described below can be equally applied to the contents described in the magnesium oxide manufacturing apparatus, they will be omitted.

The magnesium oxide manufacturing method includes a mixing step, a spray drying step and a heat treatment step. According to the method for producing magnesium oxide, magnesium oxide having high thermal conductivity, small diameter, and high density can be produced at a low cost.

The mixing step is a step of preparing a suspension, and is performed by mixing distilled water, magnesium oxide precursor powder, and additives. Since the detailed description of the mixing step is the same as that described in the mixing section, it will be omitted.

The spray drying step is a step for preparing granules, and is performed by spraying and drying the suspension mixed in the mixing step. Since the specific description of the spray drying step is the same as that described in the spray drying unit, it will be omitted.

In one example, in the spray drying step, spraying and drying of the suspension may be performed simultaneously. In the spray drying step, a detailed description of simultaneous spraying and drying is the same as that described in the spray drying unit, so it will be omitted.

The heat treatment step is a part of forming magnesium oxide, and is performed by heat-treating the granules prepared in the spray drying step. Since a detailed description of the heat treatment step is the same as that described in the heat treatment section, it will be omitted.

In one example, the method for producing magnesium oxide may further include a particle size control step. The particle size control step is a step of adjusting the size of the agglomerates when aggregates are formed by aggregation between granules subjected to heat treatment in the heat treatment step. Since the detailed description of the particle size control step is the same as that described in the particle size control unit, it will be omitted.

This application also relates to magnesium oxide. Exemplary magnesium oxide is magnesium oxide produced using the magnesium oxide manufacturing apparatus described above. Therefore, since the details of magnesium oxide to be described below can be equally applied to the contents described in the magnesium oxide manufacturing apparatus, they will be omitted.

The magnesium oxide is produced using the above-described magnesium oxide manufacturing apparatus. Magnesium oxide prepared through this has high thermal conductivity, has a small diameter, and can achieve densification. In addition, this magnesium oxide can be used as a heat dissipation filler.

The present application also relates to the use of said magnesium oxide. Exemplary magnesium oxide may be used as the heat dissipating filler containing the aforementioned magnesium oxide. Therefore, since the details of magnesium oxide to be described below can be equally applied to the contents described in the magnesium oxide manufacturing apparatus, they will be omitted.

The heat dissipating filler includes the magnesium oxide. The heat dissipating filler may have high thermal conductivity, have a small diameter, and achieve densification by including the aforementioned magnesium oxide.

The contents described above will be described in more detail through examples and comparative examples below, but the scope of the present application is not limited by the contents presented below.

Example 1

magnesium oxide manufacturing

Magnesium oxide was prepared using the apparatus of FIG. 1 . Specifically, as a mixing unit, about half of ZrO ₂ balls having a diameter of 10 mm were filled in a polyethylene container having a volume of 500 ml, and 70 g (35.9 wt%) of high-purity distilled water and a dispersant (APCA 32.5% solution) were mixed for uniform mixing. ) 8 g (4.1 wt%) was added, and ball milling was performed for about 3 minutes. Thereafter, 0.24 g (0.1 wt%) of rutile titanium oxide powder (TiO ₂ ) and niobium oxide powder (Nb ₂ O ₅ , Kojundo Chem. Lab. Co., Ltd.) After adding 0.21 g (0.1 wt%), ball milling was performed for about 5 minutes. Thereafter, 116.06 g (59.5 wt%) of magnesium hydroxide powder (Mg(OH) ₂ , Daejung Chemical Gold Co., Ltd.) was additionally added into the polyethylene container, and then ball milling was performed for about 24 hours. Thereafter, 0.58 g (0.3 wt%) of a dispersant (APCA 32.5% solution) was additionally added into the polyethylene container, ball milling was performed for 1 minute, and then poured into a beaker, followed by continuous stirring to prepare a suspension for spray drying. At this time, the suspension had a solid content of 39.6 vol%.

Thereafter, the suspension was put into a spray drying unit and spray drying was performed under the conditions shown in Table 1 below to prepare granules.

value Inlet temperature (℃) 150 Exhaust temperature (℃) 80 Hot air flow rate (m ³ /min) 0.53 Spray dryer spray pressure (kPa) 100 Spray Dryer Spray Pumping Rate (ml/h) 600

Thereafter, the granules were placed in a crucible made of alumina (Al ₂ O ₃ ) as a heat treatment unit, and heat treatment was performed for 1 hour at a temperature of 1450° C. in an electric furnace. At this time, the temperature increase rate was set to 5°C/min. During the heating process, thermal decomposition of magnesium hydroxide occurs from about 300 ° C, and the magnesium hydroxide particles in the granules change into magnesium oxide particles, and from about 1100 ° C, the converted magnesium oxide particles begin to be densified, producing magnesium oxide with a diameter of 35 μm. It became. Since the granules were used in a laboratory scale spray drying system, they were found to be generally smaller in diameter than granules produced by a general production spray drying system. However, it was found that the particle size can be easily controlled up to 150 μm using a production spray drying system. In addition, particles in the form of fine powder may adhere to the surface of the granule, but this phenomenon rarely occurs in the spray dryer for mass production because a separate fine particle collecting device is installed.

Example 2

magnesium oxide manufacturing

The solid content was changed to 34.6 vol%, the dispersant was changed to a solution made by mixing Sannopco's SN5468CF and ammonia water (28%) in a ratio of 3: 5, and the heat treatment temperature was changed to 1400 ° C. Except that, Magnesium oxide having a diameter of 35 μm was prepared in the same manner as in Example 1 using the magnesium oxide manufacturing apparatus of Example 1.

Example 3

magnesium oxide manufacturing

When the magnesium oxide prepared in Example 2 is agglomerated, after mixing the magnesium oxide prepared in Example 2 with alcohol, ball milling is performed at a low rotational speed for 30 minutes using a small ZrO ₂ ball having a diameter of 3 mm did After pouring the ball-milled magnesium oxide slurry onto a No. 635 sieve (grid size: 20 μm), sieving was performed while generating ultrasonic vibration to prepare magnesium oxide having a diameter of 40 μm.

Comparative Example 1

magnesium oxide manufacturing

Instead of using magnesium hydroxide (Mg(OH) ₂ ) as the raw material powder, magnesium oxide (MgO) is used, iso-propyl alcohol (Daejeong Chemical Gold Co., Ltd.) as a solvent, and BYK-145 as a dispersant MgO powder Using 1.5 parts by weight compared to 100 parts by weight, changing the solid content to 32.5 vol%, and changing the heat treatment temperature to 1400 ° C, the magnesium oxide manufacturing apparatus of Example 1 was used in the same manner as in Example 1. This 80 μm magnesium oxide was prepared.

Comparative Example 2

magnesium oxide manufacturing

A suspension was prepared in the same manner as in Example 1 using the mixing unit of Example 1, except that the solid content was changed to 25.5 vol%.

Thereafter, the suspension is placed in a beaker containing a magnetic bar for stirring, and stirred with a hot-plate at 95 ° C to 115 ° C until the suspension completely loses fluidity, Drying evaporated the liquid components in the suspension. Thereafter, for complete drying, the beaker containing the suspension was placed in an oven at 90 ° C., dried for 12 hours, and then the dried powder cake was pulverized in an alumina mortar and sieved using # 50 sieve to obtain magnesium hydroxide Granules were prepared. At this time, the reason for grinding and sieving is to prepare magnesium hydroxide granules having a size of several tens to hundreds of μm.

Thereafter, the magnesium hydroxide granules were heat treated in the same manner as in Example 1 using the heat treatment unit of Example 1 to prepare magnesium oxide having a particle size of about 100 μm. At this time, the size of the particle means the average size of the length of the major axis and the minor axis.

Experimental Example 1. Shape analysis

The shapes of the magnesium hydroxide granules and the magnesium oxide particles prepared in Examples and Comparative Examples were photographed with a scanning electron microscope and analyzed.

As a result, as shown in FIGS. 2 and 3, it was confirmed that the magnesium hydroxide granules of Example 1 had a spherical shape with a diameter of 15 μm to 60 μm. However, as shown in FIGS. 4 and 5 , it was confirmed that the magnesium hydroxide granules of Comparative Example 1 had a hollow or donut shape with a hollow inside and a particle size of 20 μm to 100 μm.

In addition, as shown in FIGS. 6 and 7 , it was confirmed that the magnesium oxide particles of Example 1 exhibited a dense spherical shape with a diameter of 10 μm to 50 μm. In addition, as shown in FIGS. 8 and 9 , it was confirmed that the magnesium oxide particles of Example 2 exhibited a dense spherical shape with a diameter of 5 μm to 40 μm.

On the other hand, as shown in FIG. 10, it was confirmed that the magnesium oxide particles of Comparative Example 2 exhibited a kind of blocky shape having an irregular shape rather than a spherical shape. This is because the method of directly drying the suspension was chosen without going through the spraying process of spraying the suspension to form spherical droplets by surface tension, as in the spray drying of the examples. Therefore, it was confirmed that it was very difficult to prepare spherical magnesium oxide sintered granules having a good spherical shape in the method for producing magnesium oxide particles of Comparative Example 2.

Experimental Example 2. Primary granule defect analysis

In order to confirm defects (hollow or dimple) of the magnesium hydroxide granules prepared in Examples and Comparative Examples, the magnesium oxide particles prepared in Examples and Comparative Examples were slightly impacted with a trigger bar in a mortar. After allowing some of the particles to break, they were observed under a scanning electron microscope.

As a result, as shown in FIGS. 11 and 12, it was confirmed that the MgO particles prepared in Example 2 were filled with MgO without any empty space inside. At this time, when observed with a scanning electron microscope, some magnesium oxide particles destroyed by the trigger rod are included, so some magnesium oxide particles do not appear to have a spherical shape, but in fact, the magnesium oxide particles are originally spherical. It was confirmed that the particles were properly shaped.

In addition, compared to the magnesium oxide particles before sieving prepared in Example 3 shown in FIGS. 13 and 14, the magnesium oxide particles after sieving prepared in Example 3 shown in FIGS. 15 and 16 had a diameter of 40 μm or less. It was confirmed that it had, and it was confirmed that it was possible to conveniently classify between the magnesium oxide particles.

Experimental Example 3. Secondary granule defect analysis

In order to more clearly confirm the defects of the magnesium hydroxide granules prepared in Examples and Comparative Examples, after filling a small amount of magnesium oxide particles prepared in Examples and Comparative Examples into a pipette tip (Precision Pipette Tips, PCR-200), Room-temperature curable epoxy resin (Epoxy Mount Resin and its Hardener, Allied) is filled here to impregnate and harden, and then, the tip is cut, and the cross section is cut using No. 1200 sandpaper and 1 ㎛ and 6 ㎛ diamond abrasives. After polishing, it was observed with a scanning electron microscope.

As shown in FIGS. 17 and 18, it can be seen that almost all of the magnesium oxide particles prepared in Example 2 have a spherical shape, and their insides are also filled without any hollow or dimple defects. could

In contrast, as shown in FIGS. 19 and 20 , it was confirmed that the magnesium oxide particles prepared in Comparative Example 1 had a horseshoe shape with an empty inside.

In addition, as shown in FIG. 21, it was found that the inside of the magnesium oxide particles prepared in Comparative Example 2 was relatively well densified, but the cross-sectional shape of the particles was irregular rather than spherical. Therefore, it was confirmed that it was very difficult to prepare sintered magnesium oxide granules having a good spherical shape in the method for producing magnesium oxide particles of Comparative Example 2.

10: mixing section
20: spray drying unit
30: heat treatment part

Claims (22)

A mixing unit for preparing a suspension by mixing distilled water, magnesium oxide precursor powder and additives;
a spray drying unit for preparing granules by spraying and drying the suspension mixed in the mixing unit; and
Magnesium oxide manufacturing apparatus comprising a heat treatment unit for forming magnesium oxide by heat treatment of the granules prepared in the spray drying unit. The apparatus of claim 1, wherein the magnesium oxide precursor powder is magnesium hydroxide (Mg(OH) ₂ ) powder. The apparatus for preparing magnesium oxide according to claim 1, wherein the magnesium oxide precursor powder is included in an amount of 25 parts by weight to 70 parts by weight based on 100 parts by weight of the suspension. The apparatus for preparing magnesium oxide according to claim 1, wherein the additive includes at least one selected from a dispersant, a sintering aid, and a thermal property improver. The apparatus of claim 4, wherein the dispersant is included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. The apparatus of claim 4, wherein the sintering aid is included in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. The apparatus of claim 4, wherein the thermal property improving agent is included in an amount of 0.05 to 0.45 parts by weight based on 100 parts by weight of the magnesium oxide precursor powder. The apparatus for producing magnesium oxide according to claim 1, wherein the additive does not contain at least one selected from a binder and a plasticizer. The apparatus for producing magnesium oxide according to claim 1, wherein the suspension has a solid content of 15 vol% to 50 vol%. The apparatus for producing magnesium oxide according to claim 1, wherein the spray drying unit simultaneously sprays and dries the suspension. The apparatus for producing magnesium oxide according to claim 1, wherein the droplets sprayed from the spray drying unit have a spherical shape with a diameter of 10 μm to 200 μm. The method of claim 1, wherein the spray drying unit includes an inlet through which the hot air is introduced and an outlet through which the hot air is discharged, and the temperature of the hot air introduced into the spray drying unit is 120° C. to 180° C., and is directed outside the spray drying unit. A magnesium oxide manufacturing apparatus in which the temperature of the discharged hot air is 50 ° C to 100 ° C. The apparatus for producing magnesium oxide according to claim 1, wherein the heat treatment is performed at 1300° C. to 1450° C. for 5 minutes to 120 minutes. 5. The apparatus for producing magnesium oxide according to claim 4, wherein the magnesium oxide formed through the heat treatment has a relative density of 95% or more. The apparatus for producing magnesium oxide according to claim 1, wherein the magnesium oxide formed by the heat treatment has a spherical shape with a diameter of 5 μm to 150 μm. The apparatus for producing magnesium oxide according to claim 1, wherein the magnesium oxide formed by the heat treatment has a thermal conductivity of 40 W/m·K to 65 W/m·K. The apparatus for producing magnesium oxide according to claim 1, further comprising a particle size control unit for adjusting the size of the aggregate when the granules heat-treated in the heat treatment unit are aggregated between the granules to form aggregates. It relates to a method for producing magnesium oxide using the magnesium oxide manufacturing apparatus according to claim 1,
A mixing step of preparing a suspension by mixing distilled water, magnesium oxide precursor powder, and additives;
a spray drying step of spraying and drying the suspension mixed in the mixing step to prepare granules; and
A method for producing magnesium oxide comprising a heat treatment step of forming magnesium oxide by heat treatment of the granules prepared in the spray drying step. 19. The method of claim 18, wherein in the spray drying step, spraying and drying of the suspension are performed simultaneously. [Claim 19] The method of claim 18, further comprising a particle size control step of adjusting the size of the agglomerates when the heat-treated granules are agglomerated between the granules in the heat treatment step to form agglomerates. Magnesium oxide produced using the magnesium oxide manufacturing apparatus according to claim 1. A heat dissipating filler comprising the magnesium oxide according to claim 21.

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