KR102582821B1 - Method for producing a heat dissipating coating composition using a carbon material - Google Patents

Abstract

The present invention is a method of manufacturing a heat dissipation coating composition using a carbon material, and relates to a heat dissipation sheet using a composite material manufactured by the above manufacturing method, where thermal conductivity is improved by uniformly dispersed carbon nanotubes and graphene. You can.
In addition, it is a heat dissipation sheet containing carbon nanotubes and graphene, and is a highly durable heat dissipation sheet that has excellent transparency and excellent physical properties, preventing damage from external impacts.

Description

Method for producing a heat dissipating coating composition using a carbon material}

The present invention relates to a method for manufacturing a heat dissipating coating composition using a carbon material, and more specifically, to a heat dissipating sheet using a composite material manufactured by the above manufacturing method.

Glass substrates used in electronic displays and display devices such as mobile phones, tablets, or navigation devices have many advantages such as small coefficient of linear expansion, excellent gas barrier properties, high light transmittance, low surface roughness, excellent heat resistance and chemical resistance, and high thermal conductivity. However, compared to plastic, it has the disadvantage of being weak against impact and breaking easily, and being heavy and difficult to process due to its high density.

As the electrical and electronic industries develop, interest in liquid crystal, organic light-emitting displays, flexible displays, and electronic paper is rapidly increasing, and research is being actively conducted to replace these substrates from glass to plastic.

Replacing the glass substrate with a plastic substrate consisting of a basic plastic film and a functional coating layer can lighten the overall weight of the display device, provide design flexibility, and be resistant to impact. When manufactured in a continuous process, the glass substrate can be Although it can secure economic feasibility due to its higher productivity, plastic generally has a problem in that it has a very low thermal conductivity and cannot dissipate heat quickly.

Recently, electronic displays and display devices require high power to produce high brightness, and LEDs (light emitting diodes) are mainly used as light sources. These LEDs generate a lot of heat, so they are used in electronic displays and displays. The ability to dissipate heat has become important in devices.

When transparent plastic, which emits heat, that is, has a low heat dissipation property, is used, the performance and reliability of the device are deteriorated and its lifespan is shortened.

To this end, thermally conductive polymer materials are recognized as important materials, especially polymer composites containing ceramic or metal fillers, and carbon composite materials such as graphite, carbon nanotubes, and carbon fiber. Much development is also underway regarding polymer composite materials.

Among these carbon composite materials, graphene, which has recently received a lot of attention, is a material with a thin film structure composed of carbon atoms in a honeycomb shape with a thickness of about 0.35 nm. Due to its high electrical conductivity and excellent thermal conductivity properties, much research is being conducted. In order to ensure dispersion stability within the polymer composite, it is manufactured in the form of a composite by changing the surface properties and is applied in various fields as well as thermally conductive polymer composite materials. .

In particular, it is known to have particularly excellent thermal conductivity compared to other carbon composite materials, and research has recently been actively conducted to apply it to heat dissipation materials. To solve this problem, there has been an increasing number of cases of applying heat dissipation sheets using polymer composites containing nanoparticles in recent years.

KR 10-1833561 B1

The purpose of the present invention is to provide a method for producing a heat dissipating coating composition using a carbon material.

Another object of the present invention relates to a heat dissipation sheet using a composite material manufactured by the above manufacturing method, and can provide a heat dissipation sheet with improved thermal conductivity due to uniformly dispersed carbon nanotubes and graphene.

Another object of the present invention is to provide a heat dissipation sheet containing carbon nanotubes and graphene, which has excellent transparency and excellent physical properties, so it is possible to provide a highly durable heat dissipation sheet that is not damaged by external impacts.

In order to achieve the above object, a method for producing a heat dissipating coating composition using a carbon material according to an embodiment of the present invention includes the steps of: 1) preparing a first mixture by mixing carbon nanotubes, graphene, and a dispersant in a solvent; 2) sonicating the first mixture; and 3) preparing a second mixture by mixing the first mixture with a binder and a polymer compound represented by the following formula (1):

[Formula 1]

here,

n is an integer from 8 to 20,

m is an integer from 5 to 15.

The carbon nanotubes have hydroxyl (-OH) groups formed on the surface.

The solvent is selected from the group consisting of distilled water, ethanol, phenyltrimethoxysilane, Phenethyltrimethoxysilane, N-Phenylaminopropyl trimethoxysilane, and mixtures thereof. It can be.

The binder may be selected from the group consisting of polyurethane resin, polyacrylic resin, and polyester resin.

A heat dissipating coating composition using a carbon material according to another embodiment of the present invention can be manufactured by the above manufacturing method.

A heat dissipation sheet according to another embodiment of the present invention includes a base material; It includes a carbon nanotube coating layer, and the carbon nanotube coating layer can be formed by applying a heat dissipation coating composition using the carbon material.

The carbon nanotube coating layer can be formed by applying a heat dissipation coating composition and UV irradiation.

The substrate is polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), or polyimide. It is (PI).

The present invention is a method of manufacturing a heat dissipation coating composition using a carbon material, and relates to a heat dissipation sheet using a composite material manufactured by the above manufacturing method, where thermal conductivity is improved by uniformly dispersed carbon nanotubes and graphene. You can.

In addition, it is a heat dissipation sheet containing carbon nanotubes and graphene, and is a highly durable heat dissipation sheet that has excellent transparency and excellent physical properties, preventing damage from external impacts.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement it. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

A method for producing a heat dissipating coating composition using a carbon material according to an embodiment of the present invention includes the steps of: 1) preparing a first mixture by mixing carbon nanotubes, graphene, and a dispersant in a solvent; 2) sonicating the first mixture; and 3) preparing a second mixture by mixing the first mixture with a binder and a polymer compound represented by the following formula (1):

[Formula 1]

here,

n is an integer from 8 to 20,

m is an integer from 5 to 15.

In order to manufacture a heat dissipation sheet, the composite material composition prepared above is applied to one side of the substrate, UV irradiated, and cured. By UV irradiation, the compound represented by Formula 1 may be polymerized to form a compound represented by Formula 2 below:

[Formula 2]

here,

p is an integer from 1 to 100,

n and m are as defined in Formula 1 above.

Step 2) is to uniformly disperse the graphene and carbon nanotubes, and ultrasonic treatment can be performed for 5 to 10 minutes using a bath-type ultrasonic device. After ultrasonic treatment, mix for 5 to 10 minutes using a magnetic stirrer.

When manufactured as a composite material, the polymer compound has excellent advantages such as ease of processing and diversity of shapes, but due to the nature of the polymer, heat energy transmitted through the interior is dispersed, so it has a disadvantage of low heat conduction characteristics. Therefore, if a composite material is created by appropriately mixing it with materials with excellent heat conduction properties, such as graphene and carbon nanotubes, it can be used in various fields that require heat dissipation properties without restrictions on the form.

Carbon nanotubes are microscopic molecules with a diameter of 1 nanometer (1 nanometer is 1 billionth of a meter) made up of carbon atoms connected in hexagonal rings forming a long tube. It is named so because the carbon plane, which has a honeycomb-like structure by combining three carbon atoms at a time, is rolled up to form a tube shape. It is a futuristic new material with a tensile strength 100 times stronger than steel and excellent flexibility. It is hollow, so it is light, conducts electricity as well as copper, and is known to conduct heat as well as diamond. In addition, carbon nanotubes are attracting attention as a next-generation semiconductor material as it has been discovered that they have the property of being either a conductor or a semiconductor depending on the diameter of the tube.

Expectations are high that graphene materials can be applied to various fields. Graphene, created by exfoliation of graphite, is composed of sp2 hybrid bonds of carbon with continuous chemical bonds of carbon atoms. The production price is relatively lower than that of carbon nanotubes, and mass production is easy. On the other hand, graphene has high electrical and thermal conductivity and also has high mechanical properties, so it is expected to be a representative nanomaterial that can replace carbon nanotubes.

The graphene and carbon nanotubes serve as inorganic fillers to lower the thermal expansion coefficient of the polymer compound and increase the heat dissipation characteristics of the coating film manufactured with the coating solution.

However, the graphene and carbon nanotubes have a problem of low dispersibility in polymer compounds or solvents. In other words, graphene and carbon nanotubes have excellent thermal conductivity, so they have a high possibility of being used as heat dissipation materials, but have a problem in that they do not exhibit uniform thermal conductivity due to low dispersibility in solvents, etc.

To solve this problem, a method of using a dispersant has been proposed, but the use of a small amount of the dispersant is not effective in improving the dispersibility, and if the dispersant is used in excessive amounts, graphene and carbon nano There is a problem in that it is difficult to demonstrate heat conduction properties as the content of the tube is reduced.

In order to solve the above problems, the present invention is characterized by comprising a polymer compound represented by the following formula (1):

[Formula 1]

here,

n is an integer from 8 to 20,

m is an integer from 5 to 15.

The polymer compound of the present invention is characterized in that adjacent polymers are aligned to form a polymer, and graphene and carbon nanotubes are uniformly dispersed by the polymer.

Even if the content of the dispersant is lowered, the graphene and carbon nanotubes are characterized by being uniformly dispersed by the polymer compound of the present invention.

More specifically, the polymer compound is characterized in that it is formed into a polymer by bonding as shown in the following formula (2) by UV curing:

[Formula 2]

here,

p is an integer from 1 to 100,

n and m are as defined in paragraph 1.

When a polymer is formed by alignment between polymer compounds as described above, the substituents within the polymer are aligned at regular intervals. Elements with lone pairs of electrons, such as -NH-, included in the array undergo a chemical reaction with graphene or carbon nanotubes, and as a result, they can be dispersed to a certain extent within the polymer array.

The carbon nanotubes have hydroxyl (-OH) groups formed on the surface.

The carbon nanotubes have hydroxyl groups formed on the surface through surface modification, and can be uniformly dispersed through a reaction between the hydroxyl groups formed on the surface of the carbon nanotubes and the high molecular weight polymer.

The carbon nanotubes can be modified to form hydroxyl groups on the surface using a conventional method, or carbon nanotubes with hydroxyl groups formed on the surface can be purchased and used.

Specifically, various types of carbon nanotubes can be used, such as single walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). Here, multi-walled carbon nanotubes are used. Carbon nanotubes were used. Typically, multi-walled carbon nanotubes exist in the form of a bundle due to the prominent cohesion between tubes due to van der Waals force. Therefore, for the application of multi-walled carbon nanotubes, an additional chemical treatment process to release this bundle form is required. In the present invention, multi-walled carbon nanotubes and hydrogen peroxide (H2O2) are mixed at a concentration of 100 mg/100 ml, and refluxed at a temperature of 60°C for 72 hours to form hydroxyl groups on the surface and ends of the multi-walled carbon nanotubes. group: -OH) was created to improve dispersibility during the mixing process.

The graphene may be commercially purchased graphene, or graphene manufactured through a conventional manufacturing method may be used.

Specifically, the production of graphene was performed by modifying and supplementing Hummers' method.

First, the graphite was heat treated in an argon atmosphere at 500°C to remove impurities. Next, 5 g of powdery flaky graphite and 2.5 g of sodium nitrate (NaNO3) were added to a container containing 100 ml of sulfuric acid (H2SO4), and the mixture was stirred for 20 to 40 minutes. At this time, for a safe reaction, it is best to place the container in a reaction tank at about 0°C and stir it.

While the mixed solution is stirred, 15 g of potassium permanganate (KMnO4) is added to the container. At this time, potassium permanganate is added dozens of times in small portions of about 0.1 g each. Accordingly, the temperature rise can be suppressed by rapidly reacting the mixed solution in the container with potassium permanganate.

Next, the reaction tank was removed, and when the temperature of the mixed solution reached 32°C to 38°C, it was maintained in this state for 30 minutes. At this time, after 20 minutes, the gas and bubbles generated as the mixed solution reacts are removed, producing a viscous reactant. The reactant produced in this way reaches a paste state and is gray-brown in color.

After 30 minutes, 250 ml of distilled water was added to the container containing the reactant and stirred slowly. At this time, violent boiling and a temperature increase up to 98°C are accompanied, and the reactant takes on a brown color. After stirring, the reaction was maintained for 15 minutes.

Afterwards, 700 ml of distilled water at 40°C was added to the container to dilute it, and a small amount of 3% hydrogen peroxide was added to reduce permanganate and manganese dioxide generated during the reaction. Addition of hydrogen peroxide causes the reaction to change to light yellow. The diluted reaction product was filtered using a filter with pores of 5㎛ to produce a yellow-brown cake-shaped product, that is, graphite oxide.

The resulting product was washed at least three times using 250 ml of distilled water. At this time, the washing process is completed when the pH of the waste water reaches neutral around 7. Afterwards, the graphite oxide is diluted in distilled water to a concentration of 1 g/L, and ultrasonicated for 1 to 2 hours to break the weakened interlayer bonding layer of the graphite oxide to form graphene oxide. Next, 1 ml of hydrazine hydrate was added per 100 mg of graphite oxide and refluxed for 24 hours to prepare reduced graphene. Next, the reduced graphene was washed with distilled water and methanol and then dried to prepare graphene in powder form. The method for producing graphene is not particularly limited to the method presented here, and may be produced through various methods.

The dispersants include surfactants, coupling agents, block copolymers, monomers, oligomers, vinyls, lactics, caprolactones, silicones, waxes, silanes, fluorines, ethers, alcohols, esters, and It may be selected from the group consisting of mixtures thereof. Preferably, it can be selected from the anionic surfactants SDS and NaDDBS, the cationic surfactants CTAB, nonionic TWEEN and TRITION, and the amphoteric surfactants Tego5 and SAZM Z-3-18, more preferably NaDDBS. , dispersed PVP, Tego5, SDS, and mixtures thereof.

The binder may be selected from the group consisting of polyurethane resin, polyacrylic resin, and polyester resin, and is preferably polyurethane resin, but is not limited to the above examples. The binder may be included to increase adhesion to the substrate.

The solvent may be a material that can improve the dispersion characteristics of carbon nanotubes and graphene, and in this case, a solution containing silane was used. The solution containing silane may include Phenyltrimethoxysilane, Phenethyltrimethoxysilane, and N-Phenylaminopropyl trimethoxysilane. A solution containing silane has chemical affinity with previously surface-treated carbon nanotubes and can improve the dispersion characteristics of carbon nanotubes and graphene. A solution containing such silane is, for example, mixed with 6 g of diphenyldiethoxysilane (DPDES), 4 g of tetraethyl orthosilicate (TEOS), 2 ml of distilled water, and 40 ml of ethanol and stirred for 3 hours. It can be manufactured and is in a viscous sol state.

The heat dissipating coating composition using a carbon material according to an embodiment of the present invention includes 10 to 20 parts by weight of graphene, 10 to 20 parts by weight of carbon nanotubes, 20 to 40 parts by weight of a polymer compound, and a binder, based on 100 parts by weight of the solvent. It may contain 20 to 40 parts by weight and 1 to 5 parts by weight of dispersant. When mixed and used within the above range, graphene and carbon nanotubes are uniformly dispersed in the composition, and can exhibit not only excellent thermal conductivity but also excellent adhesion to the substrate.

A heat dissipation sheet according to another embodiment of the present invention includes a base material; and a carbon nanotube coating layer, wherein the carbon nanotube coating layer is formed by applying a heat dissipating coating composition using a carbon material prepared by the above manufacturing method.

The substrate is polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), or polyimide. (PI), but is not limited to the above examples.

Manufacturing example

Preparation of heat dissipating coating composition using carbon material

A first mixture was prepared by mixing carbon nanotubes, graphene, and NaDDBS in a solvent. The solvent was prepared by mixing 6 g of diphenyldiethoxysilane (DPDES), 4 g of tetraethyl orthosilicate (TEOS), 2 ml of distilled water, and 40 ml of ethanol and stirring for 3 hours.

The first mixture was sonicated for 5 to 10 minutes using a bath-type ultrasonic device.

A second mixture was prepared by mixing ethanol, a polyurethane resin as a binder, and a polymer compound represented by the following formula (1). A heat dissipating coating composition was prepared by mixing the first mixture and the second mixture:

[Formula 1]

here,

n' is an integer of 10,

m' is an integer of 10.

The compound represented by Formula 1, carbon nanotubes with hydroxyl groups bonded to their surfaces, graphene, dispersants, and binders were all purchased and used. The specific content of the heat dissipation coating composition is shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 menstruum 100 100 100 100 100 graphene 5 10 15 20 25 carbon nanotube 5 10 15 20 25 Formula 1 10 20 30 40 50 bookbinder 10 20 30 40 50 dispersant One One One One One

(Unit weight part) Each of the heat dissipating coating compositions of Examples 1 to 5 was applied to one side of a PET substrate and then cured by UV irradiation to prepare a sheet.

Comparative Example 1

The same heat dissipation coating composition as in Example 3 was applied to a PET substrate and completely cured by heating at 100 to 110° C. for 30 minutes without UV irradiation to form a coating layer.

Experimental Example 1

Haze and transmittance measurements

Haze and transmittance were measured respectively according to ASTM D1003 standards.

The composite material compositions of Examples 1 to 5 were applied, and haze and transmittance were measured on the substrate formed with a coating layer.

Example 1 Example 2 Example 3 Example 4 Example 5 PET Haze (%) 1.8 1.5 1.2 1.0 1.8 1.9 Transmittance (%) 89 91 92 93 90 88

According to the above experimental results, the haze and transmittance were evaluated to be excellent compared to the haze and transmittance measurement results for a PET substrate without a coating layer. In particular, it was confirmed that Examples 2 to 5 showed excellent haze and transmittance measurement results.

Experimental Example 2

Physical property evaluation

Notches were made in each sample and measured at 23°C according to ASTM D256 to measure notched impact strength.

After cutting the substrate into samples each measuring 10cmХ20cm, attaching the steel to the friction resistance test device, attaching wool number #0000 and reciprocating 1000 times, visually confirming when scratches occurred on the coating surface, Friction resistance was measured.

Example 1 Example 2 Example 3 Example 4 Example 5 PET Notched impact strength
(J/ ^cm2 ) 192 220 250 260 160 190 Friction resistance Not occurred Not occurred Not occurred Not occurred generation Not occurred

As a result of the above experiments, it was confirmed that Examples 1 to 4 had excellent notched impact strength and no scratches compared to uncoated PET, and that especially Examples 2 to 4 showed excellent evaluation results.

Experimental Example 3

Evaluation of thermal conductivity properties

Vertical thermal conductivity and horizontal thermal conductivity were measured using NETZSCH LFA447 (at 25°C), and the results are listed in Table 4 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 thermal conductivity
(W/mK) horizontal thermal conductivity 85 114 120 118 109 60 vertical thermal conductivity 0.03 5.98 6.21 6.02 0.04 0.01

According to the above experimental results, it can be seen that in Examples 2 to 4, both horizontal and vertical thermal conductivities were measured to be high.

In Comparative Example 1, the coating layer was formed by heating without UV irradiation, and it was confirmed that the thermal conductivity was low. This means that graphene and carbon nanotubes are unevenly dispersed and exhibit low thermal conductivity.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. falls within the scope of rights.

Claims (8)

1) preparing a first mixture by mixing carbon nanotubes, graphene, and a dispersant in a solvent;
2) sonicating the first mixture; and
3) Comprising the step of preparing a second mixture by mixing the first mixture with a binder and a polymer compound represented by the following formula (1):
Method for producing a heat dissipating coating composition using a carbon material:
[Formula 1]

here,
n is an integer from 8 to 20,
m is an integer from 5 to 15. According to paragraph 1,
The carbon nanotubes have hydroxyl (-OH) groups formed on the surface.
Method for producing a heat dissipating coating composition using a carbon material. According to paragraph 1,
The solvent is selected from the group consisting of distilled water, ethanol, phenyltrimethoxysilane, Phenethyltrimethoxysilane, N-Phenylaminopropyl trimethoxysilane, and mixtures thereof. felled
Method for producing a heat dissipating coating composition using a carbon material. According to paragraph 1,
The binder is selected from the group consisting of polyurethane resin, polyacrylic resin, and polyester resin.
Method for producing a heat dissipating coating composition using a carbon material. Manufactured by the manufacturing method according to any one of claims 1 to 4
Heat dissipating coating composition using carbon material. write;
Contains a carbon nanotube coating layer,
The carbon nanotube coating layer is formed by applying a heat dissipation coating composition using the carbon material according to claim 5.
Heat dissipation sheet. According to clause 6,
The carbon nanotube coating layer is formed by applying a heat dissipating coating composition and irradiating it with UV.
Heat dissipation sheet. According to clause 6,
The substrate is polyethylene (PE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), or polyimide. (PI)in
Heat dissipation sheet.