KR102280275B1 - Heat sink material using carbon composite and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a carbon composite heat dissipation material and a method for manufacturing the same.
The present invention can provide a carbon composite heat dissipation material extruded simply and easily through a mixing process of carbon-based powder and aluminum powder in which carbon nanotubes and graphite are blended in a polymer resin, and the carbon composite material is a conventional aluminum It is lightweight compared to die-casting heat sinks, has significantly improved thermal conductivity compared to conventional thermally conductive plastics, and can be used as an injection molding material that can realize diversity in product molding, and can be used as heat sinks used in various industrial fields.

Description

Carbon composite heat dissipation material and its manufacturing method {HEAT SINK MATERIAL USING CARBON COMPOSITE AND MANUFACTURING METHOD THEREOF}

The present invention relates to a carbon composite heat dissipation material and a method for manufacturing the same, and more particularly, through a mixing process of carbon-based powder and metal or non-metal powder with improved thermal conductivity and dispersibility by mixing carbon nanotubes and graphite in a polymer resin. To provide a simple and easily extruded carbon composite material, the carbon composite material is lighter than the conventional aluminum die-casting heat sink, and the thermal conductivity is significantly improved compared to the conventional thermally conductive plastic. As a heat radiation material used in the industrial field It relates to a useful carbon composite heat dissipation material and a method for manufacturing the same.

In general, a heat dissipating material such as a heat sink is used in electronic products and automobile parts to dissipate heat generated during use.

Heat dissipation materials with heat dissipation characteristics are widely used in electric and electronic parts such as LED lighting fixtures, industrial inverters, electric vehicles, robot devices, and photovoltaic power generation.

In particular, with the recent development of electronic product technology, as the amount of heat generated by the electronic product itself increases due to high directivity, high density, and high performance of electronic products, a material with high thermal conductivity is required to effectively dissipate the increased amount of heat. there is. In addition, the heat dissipation material has a smaller space for dissipating heat due to the pursuit of miniaturization, weight reduction, minimum space, and portability of electronic products. In this regard, the importance of heat-dissipating materials is increasing.

On the other hand, in the related art, a heat dissipating material made of a metal such as copper and aluminum having high thermal conductivity is mainly used. However, when it is made of metal, it is difficult to implement various shapes and it is difficult to reduce the weight due to a lot of weight.

For example, aluminum die-casting material is a representative heat dissipation material currently in use, and its demand is dependent on foreign imports.

Aluminum die-casting heat dissipation material has excellent thermal conductivity, but it is heavy, difficult to form, and has processing conditions that are harmful to the environment, such as insulation coating.

In order to compensate for the above disadvantages, by manufacturing a heat sink using a thermally conductive composite plastic, a heat sink that is lightweight while being free to implement various shapes compared to the case of using a metal has been manufactured. Such a conventional thermally conductive composite plastic is made by using a filler excellent in thermal conductivity, and aluminum nitride, boron nitride, silicon nitride, etc. are used as fillers for high thermal conductivity [Patent Document 1].

However, since these materials are expensive and almost always depend on imports, there is another problem in that the manufacturing cost increases when using them to produce a heat dissipation material. On the other hand, in order to improve this problem, Patent Document 2 As a heat sink of a thermally conductive plastic material for a battery or electronic device, a composition including expanded graphite in an amount of at least 20% by weight based on the total weight of the thermally conductive plastic material is disclosed. Patent Document 2 has a problem in that the graphite is not properly dispersed in the polymer, and a relatively small amount of expanded graphite is included, making it somewhat difficult to obtain a desired thermal conductivity.

In addition, in order to secure sufficient thermal conductivity, other thermally conductive fillers and thermally conductive components such as thermally conductive fibers are included in addition to graphite. In order to increase thermal conductivity, the more the filler is filled, the more the viscosity rises due to poor flowability, There are problems in that it is difficult to produce a product due to a decrease in processability, and the appearance and physical properties of the final product are deteriorated.

Therefore, a heat dissipation material in the form of a master batch (intermediate material) has been developed by dispersing carbon-based fillers based on various polymer resins at present, but for reasons such as insulation and price competitiveness, it is not possible to completely replace the aluminum die-casting heat dissipation material.

Accordingly, the present inventors have tried to solve the conventional problems and to obtain an injection moldable carbon composite material with high thermal conductivity and versatility. As a result, carbon nanotubes and graphite are blended in an optimal amount in a polymer resin to improve thermal conductivity and dispersibility. To provide a carbon composite material extruded after mixing the improved carbon-based powder and metal or non-metal powder, the carbon composite material is lighter than the conventional aluminum die-casting heat sink, and the thermal conductivity is significantly improved compared to the conventional thermally conductive plastic, The present invention was completed by confirming that the variety of product molding can be realized.

Republic of Korea Patent Publication No. 2019-0120421 (published on October 23, 2019) Republic of Korea Patent Publication No. 2010-0126415 (published on Dec. 1, 2010)

An object of the present invention is to provide a carbon composite heat dissipation material having high thermal conductivity and light weight.

Another object of the present invention is to provide a method for manufacturing a carbon composite heat dissipation material.

In order to achieve the above object, the present invention is a metal or non-metal powder in 35 to 50% by weight, carbon-based powder is dispersed in 50 to 65% by weight of the resin base, wherein the carbon-based powder is carbon nanotubes and graphite 1 It provides a carbon composite heat dissipation material contained in a weight ratio of :3 to 1:7.

The carbon composite heat dissipation material of the present invention has a thermal conductivity of 15 to 20 W/mK and a weight reduction of 32 to 50%.

The present invention also provides a method for manufacturing a carbon composite heat dissipation material. Specifically,

1) A resin base is prepared by uniformly dispersing carbon-based powder made of carbon nanotubes and graphite in a polymer resin,

2) mixing metal or non-metal powder with the dispersed resin base,

3) The mixed resin base is extruded at an extrusion temperature of 170 to 250 ° C and an extrusion speed of 250 to 350 rpm to be palletized,

4) dehumidifying the extrusion-molded pallet,

5) It consists of vacuum packaging the dehumidified and dried pallet.

In this case, in step 1), the carbon-based powder is a mixture of carbon nanotubes and graphite, and preferably contains carbon nanotubes and graphite in a weight ratio of 1:3 to 1:7.

In addition, during extrusion in step 3), flowability (MI) of 8 to 9 and discharge amount of 30 to 50 kg/h are maintained.

It is preferable that the moisture content of the dehumidified and dried pallet in step 4) is 0.004 to 0.04%.

According to the present invention, it is possible to provide a carbon composite material extruded simply and easily through a mixing process of carbon-based powder and aluminum powder in which carbon nanotubes and graphite are blended in a polymer resin.

The carbon composite material of the present invention is lighter than the conventional aluminum die-casting heat sink, and the thermal conductivity is significantly improved compared to the conventional thermally conductive plastic, and the variety of product molding can be realized. As an injection molding material with improved functional properties, it can be used as a heat sink used in various industrial fields.

In addition, the present invention contains a resin base in which carbon nanotubes and graphite are mixed and dispersed, so that it is possible to provide a heat dissipation material having a price competitiveness while being comparable in heat dissipation efficiency to a conventional aluminum die-casting heat dissipation material.

Specifically, the heat dissipation material having heat dissipation characteristics may be used in electric and electronic components such as LED lighting fixtures, industrial inverters, electric vehicles, robot devices, and solar power generation.

In addition, the present invention provides a carbon composite heat dissipation material with significantly improved thermal conductivity by mixing and using a graphite material that is relatively inexpensive compared to carbon nanotubes by optimizing the ratio of carbon-based powder. It is possible to reduce dependence on imports and provide a high thermal conductivity multifunctional carbon composite material suitable for various needs of customers.

Furthermore, the carbon composite heat dissipation material of the present invention supplements the low formability and high weight of the metal material, thereby realizing various shapes and reducing weight.

Hereinafter, the present invention will be described in detail.

Prior to the description of the present invention, the following specific structural or functional descriptions are only exemplified for the purpose of describing embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms, It should not be construed as limited to the embodiments described herein.

In addition, since the embodiment according to the concept of the present invention may have various changes and may have various forms, specific embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments according to the concept of the present invention to specific disclosed forms, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. Alternatively, 35 to 50% by weight of the non-metal powder, 50 to 65% by weight of the resin base in which the carbon-based powder is dispersed, and carbon containing the carbon-based powder in a weight ratio of 1:3 to 1:7 by weight of carbon nanotubes and graphite Composite heat dissipation material is provided.

That is, the present invention is composed of an extruded product in which a metal material having high thermal conductivity and electrical conductivity properties is mixed with a resin base having flexibility and mechanical properties to be injected, thereby securing easy moldability and increasing productivity. To provide a carbon composite heat dissipation material capable of high heat dissipation, excellent price competitiveness, and remarkably improved thermal conductivity, which enables heat dissipation characteristics and weight reduction. In this case, the carbon-based powder is a mixture of carbon nanotubes and graphite.

In the above, carbon nanotube (CNT) is a material having high thermal conductivity and excellent electrical conductivity, and a hexagonal honeycomb graphene sheet is rolled up to a size of several nanometers in diameter to form a tube. have different properties.

These carbon nanotubes are classified into Sing Walled CNT (SWCNT), Double Walled CNT (DWCNT), Multi Walled CNT (MWCNT), Nanotube Rope, and the like according to the number of outer walls.

However, since carbon nanotubes are easily agglomerated due to their very low dispersion properties, the desired properties cannot be obtained during simple addition.

Therefore, in the present invention, while the dispersion and cohesive force can be improved, relatively inexpensive MWCNTs are used. At this time, since thermal conductivity, emissivity, weight reduction, etc. vary depending on the degree of dispersion of MWCNTs, the degree of dispersion of MWCNTs is an important factor.

In the present invention, in consideration of such dispersibility and cost economy, the present invention preferably includes a carbon-based powder in which graphite is mixed with carbon nanotubes (MWCNT).

Since the graphite is a carbon-based material and has high thermal conductivity and is well compounded with resins, when used in combination with carbon nanotubes, it is possible to achieve excellent heat dissipation properties by improving dispersibility.

Therefore, it is preferable that the carbon-based powder of the present invention contains carbon nanotubes and graphite in a weight ratio of 1:3 to 1:7, and at this time, when the graphite to carbon nanotubes is blended in a weight ratio of less than 1:3, the effect of improving thermal conductivity is It is insignificant, and if it exceeds 1:7 by weight, it becomes too stiff when powder is mixed and cannot be applied to the extrusion process.

The carbon composite heat dissipation material of the present invention that satisfies the above requirements has excellent heat dissipation properties by realizing thermal conductivity of 15 to 20 W/mK, and weight reduction of 32 to 50% compared to conventional weight is achieved.

The present invention is a method for manufacturing the small composite heat dissipation material,

1) A resin base is prepared by uniformly dispersing carbon-based powder made of carbon nanotubes and graphite in a polymer resin,

2) mixing metal or non-metal powder with the dispersed resin base,

3) The mixed resin base is extruded at an extrusion temperature of 170 to 250 ° C and an extrusion speed of 250 to 350 rpm to be palletized,

4) dehumidifying the extrusion-molded pallet,

5) provides a manufacturing method consisting of vacuum packaging the dehumidified and dried pallet.

In the manufacturing method of the present invention, step 1) can lower the metal or non-metal powder content by blending the metal or non-metal powder with 35 to 50 wt % and the carbon-based powder dispersed resin base at 50 to 65 wt %, at this time It is important to smoothly disperse the carbon-based powder having high thermal conductivity in the polymer resin. In order to achieve this, it is preferable to mix the carbon-based powder containing carbon nanotubes and graphite in a weight ratio of 1:3 to 1:7.

In addition, in the embodiment of the present invention, the carbon-based powder blended with the carbon nanotubes and graphite has a particle size of 325 mesh to increase the dispersion effect while obtaining light weight and high emissivity characteristics, and 325 in the case of metal or non-metal powder. A mesh particle size is used, but not limited thereto, and the particle size range may be selected from 250 to 350 mesh particle size. In particular, by making the particle shape have a flake type, it should be closely mixed between the polymer resins to obtain heat conduction properties and a smooth dispersion effect. The polymer resin used in step 1) is PP (polypropylene), PA6 (Polyamide6), PET. (Polyethylene terephthalate), PBT (poly-butylene-terephthalate), PA66 (Polyamide66), etc., and can be applied to ABS, PC, and PA. In addition, in the case of metal or non-metal powder in step 2), aluminum , copper, nickel, silver, gold, ceramic, magnesium, tungsten, and the like, but the most preferred example will be exemplified by aluminum powder. In step 2), 35 to 50 wt% of metal or non-metal powder and carbon Since the resin base in which the powder-based powder is dispersed contains 50 to 65% by weight, it is possible to reduce the metal-based content, which is advantageous for weight reduction and provides flexibility of the resin base. Additives such as slip agents, lubricants, and antioxidants may be mixed in an amount of less than 1% by weight within a range that does not affect the physical properties of the composition.

35 to 50% by weight of the metal or non-metal powder and 50 to 65% by weight of the resin base in which the carbon-based powder is dispersed are mixed at high speed in a high-speed supermixer. The reason for using mixing at such a high speed is for smooth mixing between components, and more preferably, by raising the mixer temperature to about 80 to 110 ° C, the resin base in which the carbon-based powder is dispersed and the metal or Make sure that the non-metallic powder is agglomerated with each other so that it is uniformly and completely mixed. At this time, if uniform mixing is not achieved, when extruded through the twin extruder, a constant pressure and temperature are received through the extrusion screw inside the twin extruder, and the surface state after extrusion is uneven, which may impair thermal conductivity and emissivity characteristics.

In the manufacturing method of the present invention, step 3) is pelletized by extrusion molding the resin base mixed in step 2) under the extrusion conditions shown in Table 1 below. At this time, the extrusion molding is performed under the conditions of a temperature of 170 to 250° C. and 250 to 350 rpm, and the extrusion-molded pallet maintains a flowability (MI) of 8 to 9 and a discharge amount of 30 to 50 kg/h during extrusion.

Thereafter, in step 4), the moisture content is increased by absorbing moisture while waiting for packaging after the extrusion, so the extruded pallet is dehumidified and dried. At this time, since the polymer resin absorbs moisture as the heat cools after extrusion, if the moisture increases, the properties during injection molding may be deteriorated.

Dehumidification is carried out at 80°C for 4 hours, and dehumidification drying is performed in a chamber having a honeycomb structure to increase dehumidification efficiency. This maximizes dehumidification efficiency and provides stable dehumidification drying because the cross-sectional area is 5 times or more compared to a small space. is possible, and the target moisture content at the initial moisture content of 0.2% is 0.04%, and more preferably 0.004 to 0.04%.

In addition, step 5) is a step of vacuum packaging after the dehumidification and drying, and it is preferable to put it in a wrapping paper made of an aluminum endothelium and vacuum-pack it.

In addition, the packaging is vacuum-packed by measuring in units of 25 kg through an automatic weighing machine.

Hereinafter, the present invention will be described in more detail through examples.

These examples are for explaining the present invention in more detail, and the scope of the present invention is not limited to these examples.

<Example 1>

A resin base was prepared by mixing 25% by weight of nylon 6, which is a polymer resin, 5% by weight of MWCNT, and 20% by weight of graphite, followed by uniform dispersion treatment. Dispersion efficiency? In order to maintain uniformity, MWCNTs were mixed at the monomer level, and graphite was used by selecting a particle size of 325 mesh.

50% by weight of the resin base and aluminum powder prepared above were put in a high-speed super mixer and mixed at a high speed for 10 minutes at a speed of 300 to 500 rpm. The mixture was extruded under the extrusion conditions shown in Table 1 below, cooled in the air phase, and molded into a pallet shape.

After extrusion, it was dehumidified at 80° C. for 4 hours, and the initial moisture content of 0.2% of the pallet was repeated until the target moisture content was 0.04%. After the dehumidification and drying, it was placed in a paper bag made of an aluminum lining, and measured in 25 kg units through an automatic weighing machine, and vacuum-packed.

<Examples 2-3>

Except for changing the contents of aluminum powder, polymer resin, MWCNT and graphite shown in Table 2 below, the same procedure as in Example 1 was performed.

<Comparative Examples 1-3>

Except for changing the contents of aluminum powder, polymer resin, MWCNT and graphite shown in Table 2 below, the same procedure as in Example 1 was performed.

<Experimental Example 1> Physical property evaluation of carbon composite material

The thermal conductivity, specific gravity, and weight reduction of the pallet-shaped carbon composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated.

The results are shown in Table 2 below.

From the results of Table 2, compared to Comparative Example 1 prepared by using MWCNT alone in the polymer resin, Examples 1 to 3 using a resin base dispersed in a mixed form of MWCNT and graphite showed significantly higher thermal conductivity of 15W/Mk or more and weight reduction was also achieved.

In addition, it was confirmed that even when dispersed in a mixed form of MWCNT and graphite in the polymer resin, the thermal conductivity and weight reduction of the carbon composite material were greatly affected according to the mixing ratio of MWCNT and graphite.

<Experimental Example 2> Extrusion state of carbon composite material

For the carbon composite material of the pallet shape prepared in Examples 1 to 3 and Comparative Example 1, flowability (MI) evaluation at 170 to 250 ° C. extrusion conditions, pallet density, palletizing degree, and discharge amount were evaluated and the following Table 3 shows.

The density of the pallet is a ratio of weight per 10 g when palletized at the same speed and size, that is, based on the density of distributed particles when the cut surface of the pallet is observed through the naked eye and a microscope.

As confirmed above, compared to the conventional aluminum die-casting, the carbon composite heat dissipating material according to the present invention has significantly increased thermal conductivity, and comparing the differences in characteristics and effects between heat dissipating products is shown in Table 4 below.

In the above, the present invention has been described in detail only with respect to the described embodiments, but it is obvious to those skilled in the art that various modifications and variations are possible within the scope of the technical spirit of the present invention, and it is natural that such variations and modifications belong to the appended claims.

Claims (6)

35 to 50% by weight of the metal or non-metal powder, and 50 to 65% by weight of the resin base in which the carbon-based powder is dispersed,
The carbon-based powder is a mixture of carbon nanotubes and graphite, and the mixing ratio is 1:3 to 1:7 by weight,
A carbon composite heat dissipation material, characterized in that the metal or non-metal powder and the resin base in which the carbon-based powder is dispersed are mixed at 80 to 110° C. and palletized through extrusion molding. According to claim 1, wherein the carbon composite heat dissipation material
Carbon composite heat dissipation material, characterized in that thermal conductivity of 15 to 20 W/mK and weight reduction of 32 to 50% compared to conventional specific gravity is realized. A resin base is prepared by uniformly dispersing carbon-based powder made of carbon nanotubes and graphite in a polymer resin,
Metal or non-metal powder is mixed with the dispersed resin base at 80 to 110 ° C., and the mixed resin base is extruded under the conditions of an extrusion temperature of 170 to 250 ° C and an extrusion speed of 250 to 350 rpm to palletize,
Dehumidifying and drying the extruded pallet,
The dehumidified and dried pallets are vacuum-packed,
The method for producing a carbon composite heat dissipation material, characterized in that the carbon-based powder is contained in a weight ratio of carbon nanotubes and graphite 1:3 to 1:7. delete [Claim 4] The method for manufacturing a carbon composite heat dissipation material according to claim 3, wherein flowability (MI) of 8 to 9 and a discharge amount of 30 to 50 kg/h are maintained during the extrusion molding. The method of claim 3, wherein the moisture content of the dehumidified and dried pallet is 0.004 to 0.04%.