KR102551175B1 - Semi-spherical alumina for heat dissipation material using fluorine-based flux and manufacturing method thereof - Google Patents

Abstract

The present invention relates to semi-spherical alumina for heat dissipation materials using a fluorine-based flux and a method for producing the same, and more particularly, to a semi-spherical alumina for a heat dissipation material using aluminum hydroxide and a fluorine-based flux and a method for producing the same.
In the method for producing semi-spherical alumina according to the present invention, 0.5 to 20 parts by weight of a fluorine compound and 0.1 to 15 parts by weight of an aluminum compound are mixed with 100 parts by weight of aluminum hydroxide powder, calcined at 1,000 to 1,300 ° C, pulverized, washed, and dried. are manufactured

Description

Semi-spherical alumina for heat dissipation material using fluorine-based flux and manufacturing method thereof}

The present invention relates to semi-spherical alumina for heat dissipation materials using a fluorine-based flux and a method for producing the same, and more particularly, to a semi-spherical alumina for a heat dissipation material using aluminum hydroxide and a fluorine-based flux and a method for producing the same.

In order to dissipate heat in displays, automobile electric fields, etc., a heat dissipation sheet in which alumina particles having a low impurity content are mixed with a polymer is used.

The type of alumina (alpha alumina) used in the heat radiation sheet depends on the performance of the heat radiation sheet required. When the performance of the heat radiation sheet is less than 1 W/mK, fine alumina of less than 1 micron is used, and the heat radiation sheet required When the performance of 1 to 2 W/mK is used, a large amount of particulate alumina of less than 1 micron and a small amount of spherical alumina of 1 to 50 microns are mixed and the required performance of the heat radiation sheet is 2 to 3 W/mK , a small amount of particulate alumina of less than 1 micron and a large amount of spherical alumina of 1 to 50 micron are mixed and used.

In the case of such spherical alumina for heat dissipation sheets, it is mainly manufactured using a flame melting method capable of forming high-purity, large-diameter particles.

Recently, high-performance heat dissipation sheets. That is, as the demand for a heat dissipation sheet having a thermal conductivity of more than 3 W/mK, for example, 4 to 10 W/mK increases, while having a size in the range of 1 to 50 microns like spherical alumina, filling Demand for quasi-spherical alumina with higher heat transfer performance is growing. In the case of quasi-spherical alumina, since it is composed of polyhedron-shaped particles, it has an advantage of excellent thermal conductivity due to a wide contact area between particles during lamination.

However, quasi-spherical alumina particles for heat dissipation sheets have large, uniform, high-purity, and polyhedral shapes, such as spherical alumina produced by a flame melting method. there is.

In addition, since existing alumina manufacturing methods mainly produce particles using a precursor solution, it is difficult to grow the particles to a predetermined size, and a neutralization process using an acid is required to neutralize the base used for dissolution, and the intermediate process There arises a problem that it is difficult to pulverize the particles generated in. Due to this, the existing methods have problems in that the working environment is bad, time consuming, and efficiency is low.

Accordingly, there is a continuing demand for a new method capable of producing quasi-spherical alumina without using an alumina precursor solution.

As a way to solve this problem, Korean Patent Publication No. 10-2021-0047453 discloses a mixing process of mixing calcined alpha-alumina powder and a fluorinated compound; A firing process of drying the compound mixed through the mixing process, charging it into a crucible, and firing it in a predetermined environment; A removal step of washing the calcined compound with hot water to remove the salt of the fluorinated compound through the calcining process; and a pulverization step of pulverizing the agglomerated particles using a pulverizer.

However, this method is inefficient as a method of modifying the shape of already prepared alumina without using a precursor compound.

An object to be solved by the present invention is to provide a method for producing quasi-spherical alumina particles having a low impurity content using aluminum hydroxide.

Another problem to be solved by the present invention is to provide a method for producing quasi-spherical alumina particles having a low impurity content without using an aluminum hydroxide solution.

An object to be solved in the present invention is to prepare quasi-spherical alumina particles having a low impurity content using aluminum hydroxide, and to provide a high-performance heat dissipation sheet using the same.

Terms

'Particle diameter' and 'particle size' mean the average size of the particles.

'Fluorine compound' means 'a compound containing a fluorine atom.

'Aluminum compound' refers to a compound containing an aluminum atom and not containing a fluorine atom.

'Quasi-spherical' means a polyhedral particle having a minor/major axis ratio of 0.8 or more.

summary

In order to solve the above problems, the method according to the present invention

0.5 to 20 parts by weight of a fluorine compound and 0.1 to 15 parts by weight of an aluminum compound are mixed with 100 parts by weight of aluminum hydroxide powder and calcined at 1,000 to 1,300 ° C., then pulverized and washed, and dried to obtain semi-spherical alumina. do.

In the present invention, since the aluminum hydroxide undergoes a cleaning process after firing, there is no need to use aluminum hydroxide having a high purity of three or more, and accordingly, two nine grade aluminum hydroxide may be used.

In the practice of the present invention, the purity of the aluminum hydroxide may be 99.0 to 99.8% pure aluminum hydroxide, preferably 99.5 to 99.7% pure aluminum hydroxide. The two-nine grade aluminum hydroxide can be purchased and used commercially.

In the present invention, the aluminum hydroxide powder may have a smaller size than the quasi-spherical alumina particles produced because the particles become large during the manufacturing process of the quasi-spherical alumina. Preferably, it may have a particle size of 50 to 80% of the quasi-spherical alumina particles to be produced, and more preferably, it may have a particle size of 60 to 70%.

In the practice of the present invention, when the particle size of the quasi-spherical alumina to be produced is 5 microns, the aluminum hydroxide powder may have a particle size of 2 to 4 microns, and when the particle size of the quasi-spherical alumina to be produced is 50 microns, The aluminum hydroxide powder may have a particle size of 25 to 40 microns.

In the practice of the present invention, the aluminum hydroxide powder may be pulverized to have the required particle size. In one embodiment of the present invention, the crushing may use a jet mill crusher. The jet mill crusher can be purchased and used commercially.

In the present invention, the fluorine compound may be used to lower the melting point in the heat treatment process, preferably potassium fluoroaluminate such as KAlF ₄ , K ₂ AlF ₅ , K2AlF ₃ H ₂ 0, calcium fluoroaluminate Nate, sodium fluoroaluminate, and pentafluoroaluminate may be used, and more preferably, a fluorine compound having no metal components except for aluminum so as to further increase the purity of the resulting particles, such as pentafluoroaluminate. Fluoroaluminates may be used.

In the present invention, the fluorine compound may be used in an amount of 2 to 20 parts by weight, preferably 5 to 15 parts by weight, and more preferably 7 to 12 parts by weight, based on 100 parts by weight of aluminum hydroxide. When the content of the fluorine compound is small, a target shape cannot be obtained or particles smaller than the target size can be obtained. characteristics are adversely affected.

In the present invention, the aluminum compound may be used as a material that leads the process of forming such a semi-spherical shape, preferably aluminum chloride, aluminum phosphate, aluminum sulfate, or lithium aluminum hydride, and more preferably Aluminum chloride can be used.

In the present invention, the aluminum compound may be used in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 10 parts by weight, and more preferably 0.3 to 5 parts by weight, based on 100 parts by weight of aluminum hydroxide. If the content of the aluminum compound is small, densification of unit particles may not be sufficiently formed, resulting in a spongy phenomenon that adversely affects heat dissipation characteristics. can happen

In the present invention, the mixing of the aluminum hydroxide, the fluorine compound, and the aluminum compound may be dry mixing, and may be performed using a mixer capable of mixing powder.

In the present invention, the firing may be performed for 5 to 10 hours in the range of 1,000 to 1,300 ° C., preferably at 1,100 to 1,200 ° C., which can form shapes due to rearrangement of particles. When the temperature is less than 1,000 ° C., particles of a target size cannot be formed, and when the temperature exceeds 1,300 ° C., particles of various sizes are aggregated in a net shape, thereby deteriorating heat dissipation characteristics.

In the practice of the present invention, it is preferable to increase the temperature up to the firing temperature at a rate of less than 1 ° C. per minute in order to induce a rearrangement process between the particles to form quasi-spherical shapes, for example, 0.1 to 0.1 ° C. per minute. Rising rate in the range of 0.9°C, more preferably in the range of 0.2 to 0.8°C per minute, even more preferably in the range of 0.3 to 0.7°C per minute, most preferably in the range of 0.4 to 0.6°C per minute. temperature can be raised.

In the present invention, the pulverization is a process of pulverizing particles aggregated by surface adhesion or the like by unit particle size, and the pulverization may be performed by milling. In the practice of the present invention, a bead mill may be used for the milling, and the bead mill may be purchased and used commercially.

In the present invention, the washing is used to remove impurities to lower the impurity content of the quasi-spherical alumina, preferably using water, more preferably using hot distilled water. The cleaning may be performed one or more times, and more preferably, it may be repeatedly performed 1 to 3 times.

In the present invention, the cleaned particles may be additionally classified to classify quasi-spherical alumina by particle size. The classification may be performed using a cyclone method. The cyclone-type classification may use a multi-cyclone device, and the multi-cyclone device may be commercially purchased and used.

In the present invention, the particles classified after washing or washing can be filtered to quickly remove the water used for washing. A filter may be used for the filtration, and the filter may be commercially purchased and used.

In the present invention, the filtered particles may be dried to remove water, and the drying may be performed by forced air blowing. The forced blowing method may use a forced blower, which may be purchased and used commercially.

In the present invention, the dried particles may be surface treated to improve flowability by increasing the fluidity reduced by the angled surface. The surface treatment for improving the flowability may use fatty acids. The fatty acid may be myristoleic acid, oleic acid, linoleic acid, gadeleic acid, aracadonic acid, erucic acid, adrenoic acid, and the like, and may be purchased and used commercially.

In the present invention, the quasi-spherical alumina has at least two or more planes, preferably four or more planes, more preferably six or more planes, more preferably eight or more planes so that surface contact can be made with each other. The branch may be a polygonal particle, for example, a polyhedral particle having 10 to 50 polygons.

In the present invention, the quasi-spherical alumina may be composed of small-sized quasi-spherical alumina particles, medium-sized quasi-spherical alumina particles, and large-sized quasi-spherical alumina particles. In the practice of the present invention, the small-sized quasi-spherical alumina particles may have a particle size of about 1 micron, the medium-sized quasi-spherical alumina particles may have a particle size of about 5 microns, and the large quasi-spherical alumina particles may have a particle size of about 5 microns It may have a particle size of around 50 microns.

In the practice of the present invention, the quasi-spherical alumina particles may be composed of particles having a very narrow particle distribution, for example, particles in the average particle size ± 30% size range, preferably average particle size ± 20% size Particles in the range may be 60% or more, more preferably 70% or more, even more preferably 80% or more, and most preferably 90% or more of the total particles.

In one aspect, the present invention provides heat dissipation comprising 1 to 50% by weight of quasi-spherical alumina particles composed of small particles of about 1 micron, medium-sized particles of about 5 microns, large particles of about 50 microns, or a mixture of one or more thereof. sheet is provided.

In the present invention, the heat dissipation sheet may have a heat dissipation property of 5 to 10 W/mK.

The present invention suggests a new method for producing high-purity quasi-spherical alumina particles using aluminum hydroxide.

The method according to the present invention is difficult to control the size or shape of the particles, and high-purity quasi-spherical alumina particles with low impurity content can be produced without using a liquid aluminum hydroxide solution in which a large amount of wastewater and impurities are generated during production. . Therefore, in order to obtain homogeneous particles, the process of dissolving aluminum hydroxide with sodium hydroxide, the process of precipitating by inserting seeds into aluminum hydroxide particles, the process of neutralizing them using acid, and recrystallization It is possible to solve various environmental problems occurring in the process of using heavy metals such as copper to enlarge the size of small particles generated when heat-treating the generated particles.

In addition, the method according to the present invention, in producing high-purity quasi-spherical alumina particles, does not use high-purity aluminum hydroxide, but uses two-nine grade dry powder, so the production cost and unit price are competitive.

In addition, the high-purity quasi-spherical alumina particles produced by the method according to the present invention have a uniform particle size, so that quasi-spherical alumina particles of a required size can be prepared, and the consumer can mix and use them as needed.

1 is a flow chart showing a synthesis process according to an embodiment of the present invention.
2 is an electron micrograph of a quasi-spherical alumina particle of 5 micro particles manufactured according to an embodiment of the present invention.
3 is an electron micrograph of quasi-spherical alumina particles of 50 microns manufactured according to an embodiment of the present invention.
4 is an electron micrograph of quasi-spherical alumina particles of 1 micron produced according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail through examples. It should be noted that the following examples are not intended to limit the present invention, and are not intended to limit the present invention.

Example 1

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 3 microns. 50 g of a fluorine compound (pentafluoroaluminate) and 2 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 3 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,200 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake. The prepared quasi-spherical alumina cake was pulverized with a bead mill and then washed with heated distilled water. After washing, it was filtered using a filter and then dried to prepare quasi-spherical alpha-alumina particles having a size of 5 microns. The prepared quasi-spherical alpha-alumina particles were surface-treated with fatty acid (oleic acid) to obtain surface-treated quasi-spherical alpha-alumina particles. A photograph of the obtained quasi-spherical alumina having a size of 5 microns is shown in FIG. 2 .

Example 2

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 3 microns. 10 g of a fluorine compound (pentafluoroaluminate) and 20 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 3 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,150 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake. The prepared quasi-spherical alumina cake was pulverized with a bead mill and then washed with heated distilled water. After washing, particles having a size of 5 microns were classified using a multi-cyclone. The classified particles were filtered using a filter and then dried to prepare quasi-spherical alpha-alumina particles having a size of 5 microns. The prepared quasi-spherical alpha-alumina particles were surface-treated with fatty acid (oleic acid) to obtain surface-treated quasi-spherical alpha-alumina particles.

Example 3

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 3 microns. 75 g of a fluorine compound (pentafluoroaluminate) and 10 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 3 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,100 ° C. at a rate of 0.5 ° C. per minute to prepare a quasi-spherical alpha-alumina particle cake. The prepared quasi-spherical alumina cake was pulverized with a bead mill and then washed with heated distilled water. After washing, particles having a size of 5 microns were classified using a multi-cyclone. The classified particles were filtered using a filter and then dried to prepare quasi-spherical alpha-alumina particles having a size of 5 microns. The prepared quasi-spherical alpha-alumina particles were surface-treated with fatty acid (oleic acid) to obtain surface-treated quasi-spherical alpha-alumina particles.

Example 4

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 35 microns. 10 g of a fluorine compound (pentafluoroaluminate) and 20 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 35 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,200 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake. The prepared quasi-spherical alumina cake was pulverized with a bead mill and then washed with heated distilled water. The washed particles were filtered using a filter and then dried to prepare quasi-spherical alpha-alumina particles having a size of 50 microns. The prepared quasi-spherical alpha-alumina particles were surface-treated with fatty acid (oleic acid) to obtain surface-treated quasi-spherical alpha-alumina particles. The prepared particles were photographed to confirm the size and shape, and are shown in FIG. 3 .

Example 5

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 0.5 microns. In a powder mixer, 10 g of a fluorine compound (pentafluoroaluminate) and 20 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 0.5 microns and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,200 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake. The prepared quasi-spherical alumina cake was pulverized with a bead mill and then washed with heated distilled water. After washing, it was filtered using a filter and then dried to prepare quasi-spherical alpha-alumina particles having a size of 1 micron. The prepared quasi-spherical alpha-alumina particles were surface-treated with fatty acid (oleic acid) to obtain surface-treated quasi-spherical alpha-alumina particles. The prepared particles were photographed to confirm the size and shape, which are shown in FIG. 4 .

Comparative Example 1 (increased amount of fluorine compound)

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 35 microns. 200 g of a fluorine compound (pentafluoroaluminate) and 2 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 35 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,200 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake.

As a result, non-densified particles of various sizes were formed in an attached form, and particles with a narrow particle size distribution could not be obtained.

Comparative Example 2 (increase in aluminum compound )

500 g of aluminum hydroxide powder (98% purity) was put into a disintegrator and disintegrated to obtain particles having a size of 35 microns. 20 g of a fluorine compound (pentafluoroaluminate) and 50 g of an aluminum compound (aluminum chloride) were added to 500 g of aluminum hydroxide powder having a size of 35 microns in a powder mixer and mixed.

The mixed powder was placed in a crucible capable of withstanding high temperatures, and the temperature was raised to 1,200 °C at a rate of 0.5 °C per minute to prepare a quasi-spherical alpha-alumina particle cake.

As a result, a form in which densified net-shaped particles agglomerated occurred, forming a form that could not be disintegrated into a unit particle size.

Claims (12)

Semi-spherical alumina manufacturing method characterized by dry mixing 0.5 to 20 parts by weight of a fluorine compound and 0.1 to 15 parts by weight of an aluminum compound with 100 parts by weight of aluminum hydroxide powder, calcined at 1,000 to 1,300 C, then pulverized, washed, and dried. . According to claim 1,
The purity of the aluminum hydroxide is a semi-spherical alumina manufacturing method, characterized in that it has a purity of 99.0 ~ 99.8%. According to claim 1,
The method for producing quasi-spherical alumina, characterized in that the particle size of the aluminum hydroxide has a particle size of 50 to 80% of the quasi-spherical alumina particles to be produced. According to claim 1,
The quasi-spherical alumina manufacturing method, characterized in that having a particle size in the range of 1 to 50 microns. According to claim 1,
The fluorine compound is a quasi-spherical alumina manufacturing method, characterized in that at least one selected from the group consisting of potassium fluoroaluminate, calcium fluoroaluminate, sodium fluoroaluminate, and pentafluoroaluminate. According to claim 1,
The fluorine compound is a quasi-spherical alumina manufacturing method, characterized in that it comprises 5 to 15 parts by weight based on 100 parts by weight of aluminum hydroxide, According to claim 1,
Wherein the aluminum compound is selected from the group consisting of aluminum chloride, aluminum phosphate, aluminum sulfate, and lithium aluminum hydride. According to claim 1,
The alumina compound is a semi-spherical alumina manufacturing method, characterized in that used in the range of 0.3 to 5 parts by weight based on 100 parts by weight of aluminum hydroxide. According to claim 1,
The firing is a method for producing quasi-spherical alumina, characterized in that made in the range of 1,000 ~ 1,300 ℃. According to claim 9,
A method for producing quasi-spherical alumina, characterized in that the temperature is raised at a rate of less than 1 ℃ per minute to the firing temperature. A heat dissipation member comprising the quasi-spherical alumina particles according to any one of claims 1 to 10. The heat dissipation member of claim 11, wherein the heat dissipation member includes 1 to 50 parts by weight of quasi-spherical alumina particles based on 100 parts by weight of the polymer.

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