KR20130104754A - Thermal conductive resin composites comprising carbon nano tubes and method of preparing the same - Google Patents

Abstract

The present invention relates to a thermally conductive resin composite containing carbon nanotubes and a method for manufacturing the same, and more particularly, a carbon nanotube and a silicon oxide-bonded particles are dispersed in a polymer resin, thereby containing a large amount of carbon nanotubes. Therefore, the present invention relates to a thermally conductive resin composite containing carbon nanotubes having excellent thermal conductivity, and in particular, its structure does not collapse even at high heat, and thus has excellent thermal durability.

Description

Thermal conductive resin composites comprising carbon nano tubes and Method of preparing the same

The present invention relates to a thermally conductive resin composite containing carbon nanotubes and a method for producing the same, and more particularly, to a composite having high conductivity without decomposing even at high heat and a method for producing the same.

Various devices, such as various mechanical devices and electronic products, are equipped with various types of heat exchange means for effectively dissipating heat generated therein.

As such a heat exchange means, conventionally, heat exchange means were mainly manufactured using metal materials, such as aluminum and copper, which are excellent in thermal conductivity. However, such a metal heat exchange means has a problem that the material price is expensive, it is difficult to manufacture in a very small and precise shape.

In order to improve this problem, the thermal conductivity is excellent at 6,600W / mK in the longitudinal direction at room temperature, and the carbon nanotubes having excellent tensile strength and excellent electrical conductivity and excellent moldability, and the polymer resin which is more advantageous than the metal material are combined with each other. Efforts have been made to develop a material for heat exchange means, and various efforts have been made to manufacture a carbon nanotube-containing polymer composite by dispersing carbon nanotubes in a polymer resin.

However, in the prior art, in order to solve the problem that the carbon nanotubes are cohesive with each other and are difficult to uniformly disperse in the polymer resin, a chemical method using a strong acid or a surfactant is used to increase the dispersibility of the carbon nanotubes in the polymer resin. By using this, there was a problem in that physical properties such as thermal conductivity and electrical conductivity of carbon nanotubes were significantly reduced.

In addition, even using such a chemical method, the carbon nanotube content can be dispersed within the polymer resin within 10%, in which case there is a problem that the thermal conductivity is lower than the degree of industrial use.

In order to solve this problem, Korean Patent Laid-Open Publication No. 12011-0101855 has a polymer resin filled in a predetermined thickness between individual carbon nanotubes grown after growing carbon nanotubes on a substrate in a vertical direction and in a bundle. Disclosed is a thermally conductive plastic produced. However, there is still a disadvantage in that the heat durability is insufficient in the high temperature conditions, the manufacturing method is not easy, and the direction of heat conduction is excellent only in the direction of growing the carbon nanotubes.

Therefore, there is still a need to develop a thermally conductive material having high thermal conductivity as well as high thermal conductivity by combining a large amount of carbon nanotubes with a polymer resin.

Patent Document 1: Korean Patent Publication No. 12011-0101855

An object of the present invention is to provide a resin composite having excellent thermal conductivity and a method of manufacturing the same.

In addition, an object of the present invention is to provide a resin composite and a method for producing the resin composite that can maintain its thermal conductivity and excellent thermal durability because the structure does not collapse even at high temperatures.

1. A thermally conductive resin composite in which carbon nanotubes and silicon oxide combined particles are dispersed inside a polymer resin.

2. The thermally conductive resin composite of claim 1, wherein the bond between the carbon nanotubes and the silicon oxide is a physical bond or a chemical bond.

3. The thermally conductive resin composite of claim 2, wherein the chemical bond is a bond between a silicon oxide and a reactive group formed on the surface of the acid treated carbon nanotubes.

4. The thermally conductive resin composite of claim 1, wherein the particles are included in an amount of 30 parts by weight or less based on 100 parts by weight of the thermally conductive resin composite.

5. The method according to claim 1, wherein the polymer resin is at least one selected from the group consisting of an epoxy resin, a phenol resin and a melamine resin thermosetting resin; Thermoplastic resins selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, polyvinyl chloride resins, polyamide resins, polyethylene terephthalate resins and acrylic resins; Or a thermally conductive resin composite thereof.

6. (S1) preparing a carbon nanotube dispersion; (S2) preparing a mixture of the carbon nanotube dispersion and silica sol; And (S3) filtering and drying the precipitate obtained from the mixed solution to prepare a powder of carbon nanotubes and silicon oxide combined particles; And (S4) mixing and curing the powder with a polymer resin.

7. The method of claim 6, wherein the carbon nanotube dispersion comprises a carbon nanotube, a dispersant, and a dispersion medium.

8. The method for producing a thermally conductive composite according to claim 7, wherein the carbon nanotubes are carbon nanotubes which have not been acid treated or pretreated.

9. The method according to claim 7, wherein the dispersing agent is sodium dodecyl sulfonate, sodium dodecylbenzenesulfonate or a mixture thereof.

10. The method according to claim 6, wherein the silica sol is based on 1 mol of tetraalkoxysilane compound having 1-20 carbon atoms of the alkoxy group, 2-15 mol of alcohol solvent, 2-5 mol of H ₂ O and 0.001-0.01 mol of acid catalyst. Method for producing a thermally conductive composite is formed by mixing.

11. The method according to claim 6, wherein the polymer resin is at least one selected from the group consisting of an epoxy resin, a phenol resin and a melamine resin thermosetting resin; Thermoplastic resins selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, polyvinyl chloride resins, polyamide resins, polyethylene terephthalate resins and acrylic resins; Or a mixture thereof.

12. The method for preparing a thermally conductive composite according to claim 6, wherein the curing agent is further mixed in the step (S4).

The thermally conductive resin composite of the present invention may contain a large amount of carbon nanotubes.

In addition, the thermally conductive resin composite of the present invention is excellent in thermal conductivity, and in particular, its structure does not collapse even at high temperatures, and thus is excellent in thermal durability.

The method for producing a thermally conductive resin composite of the present invention can produce a resin composite containing a large amount of carbon nanotubes.

The method for producing a thermally conductive resin composite of the present invention can produce a thermally conductive resin composite by a simple method.

According to the present invention, carbon nanotubes and silicon oxide-bonded particles are dispersed in a polymer resin, thereby containing a large amount of carbon nanotubes, and having excellent thermal conductivity. The present invention relates to a thermally conductive resin composite containing a tube and a method of manufacturing the same.

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

The thermally conductive resin composite of the present invention has a structure in which particles in which carbon nanotubes and silicon oxides are bonded are dispersed in a polymer resin.

The particles in which the carbon nanotubes and the silicon oxide dispersed in the heat conductive resin composite of the present invention are bonded are particles formed by physically or chemically bonding the carbon nanotubes and the silicon oxide. Physical bonds are structures in which carbon nanotubes and silicon oxides are simply attached, and chemical bonds are structures in which carbon nanotubes and silicon oxides are connected by chemical bonds.

In one embodiment of forming a chemical bond between the carbon nanotubes and the silicon oxide, the carbon nanotubes are acid-treated to introduce a reactive group on the surface thereof, and react with the silica sol to form a chemical bond between the carbon nanotubes and the silicon oxide. Particles can be obtained.

The thermally conductive resin composite of the present invention can disperse a large amount of carbon nanotubes in a polymer resin unlike the prior art by using particles in which carbon nanotubes are bonded to silicon oxide. For example, the particles may be included up to 30 parts by weight (less than), more preferably up to 25 parts by weight with respect to 100 parts by weight of the thermally conductive resin composite. In practice, the content exceeding this is possible, but when it exceeds 30 parts by weight, the resin composite may not be effectively formed or cured. Since the thermally conductive resin composite of the present invention is characterized by including a large amount of carbon nanotubes, the lower limit thereof is not particularly limited. For example, it may be included up to 0.5 parts by weight based on 100 parts by weight of the thermally conductive resin composite, but is not limited thereto.

In addition, the silicon oxide itself has a thermal conductivity, when combined with the carbon nanotubes according to the present invention, the thermal conductivity of the composite is significantly increased.

In the thermally conductive resin composite of the present invention, the polymer resin usable is not particularly limited. Conventional thermosetting resins, thermoplastic resins or mixtures thereof can be used. As the thermosetting resin, an epoxy resin, a phenol resin, a melamine resin, or the like may be used alone or as a mixture of two or more thereof.As the thermoplastic resin, polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, and polyamide resin may be used. , Polyethylene terephthalate resin, acrylic resin and the like can be used alone or in combination of two or more thereof.

Hereinafter will be described in detail an embodiment of a method for producing a thermally conductive resin composite of the present invention.

First, a carbon nanotube dispersion is prepared (S1).

The carbon nanotube dispersion may be prepared by including carbon nanotubes, a dispersant, and a dispersion medium.

The carbon nanotubes (CNTs) may be manufactured by a conventional method such as an arc discharge method, a laser deposition method, a plasma chemical vapor deposition method, a vapor phase synthesis method, a pyrolysis method, or the like and then heat-treated. The carbon nanotubes synthesized by the above synthesis method include carbon impurities such as amorphous carbon or crystalline graphite particles and catalyst transition metal particles. For example, when manufactured by an arc discharge method, 15-30 wt% of carbon nanotubes, 45-70 wt% of carbon impurities, and 5-25 wt% of catalyst transition metal particles are contained in 100 wt% of the product. When the impregnated carbon nanotubes are directly applied to the coating solution without purification, the dispersibility and coating properties of the coating solution are deteriorated, and unique physical properties inherent to the carbon nanotubes are hardly manifested. Therefore, in the present invention, carbon nanotubes in which impurities are removed as much as possible by heat treatment of a product produced by an arc discharge method are used. Specifically, the product prepared by the above synthesis method is made into a sheet or granule shape having an average diameter of 2-5 mm, and then put into a rotary reactor inclined at an angle of 1-5 ° downward with respect to the advancing direction (horizontal basis). Heat the rotary reactor to 350-500 ° C. while supplying an oxidizing gas at a rate of 200-500 kPa / min to 1 g of the product introduced above and heat-treating for 60-150 minutes. At this time, the inclined rotatable reactor rotates at a speed of 5-20 rpm to maximize the contact surface area while dispersing the product and automatically move in the advancing direction to maximize the contact surface area with the oxidizing gas and prevent local oxidation. Heat treatment. According to this method, the weight of the charged product is reduced by 60-85%, so that high-purity carbon nanotubes are obtained.

The carbon nanotubes contain carbon impurities in an amount of not more than 40% by weight, more preferably not more than 25% by weight, in the total 100% by weight of the carbon nanotubes in terms of dispersibility and stability as well as securing the thermal conductivity of the resin composite.

The carbon nanotubes may be single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes, which may be used alone or in combination of two or more.

The carbon nanotubes according to the present invention may be acid-treated or acid-treated before being incorporated into the dispersion. The acid-treated carbon nanotubes have a reactive group on their surface. This reactive group is the part which will form a chemical bond with silicon oxide later. Specific examples of the reactive group include a hydroxy group and a carboxy group.

The dispersant is not particularly limited as long as it is an anionic surfactant. However, it is excellent in compatibility with sodium dodecylsulfonate (SDS) or sodium dodecyl benzene sulfonate (NaDDBS) carbon nanotubes, It is preferable in terms of maximizing acidity.

As a dispersion medium, water (H ₂ O) may be generally used.

Next, a mixture of carbon nanotube dispersions and silica sol is prepared (S2).

Silica sol is mixed with 2 to 15 mol of alcohol solvent, 2 to 5 mol of H ₂ O, and 0.001 to 0.01 mol of acid catalyst with respect to 1 mol of tetraalkoxysilane compound having 1-20 carbon atoms in the alkoxy group, and then sol-gel reaction. Can be formed. When the components are mixed in the content range, the sol-gel reaction occurs well, and when mixed with the carbon nanotube dispersion, the carbon nanotubes and the silicon dioxide may be combined to produce an excellent yield.

The tetraalkoxysilane compound is a component for forming a silica sol. The alkoxy group may be linear or branched, and preferably has 1-20 carbon atoms. Especially, tetraethoxysilane, tetramethoxysilane, tetra-n-propoxysilane, these oligomers, etc. are preferable, These can be used individually or in mixture of 2 or more types.

Alcohol solvents and water are intended to affect the hydrolysis during the formation of the silica sol. The alcohol solvent is preferably a hydrophilic alcohol solvent in consideration of being used in the hydrolysis reaction. Specifically, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl -1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, etc. are mentioned, These can be used individually or in combination of 2 or more types.

The acid catalyst is for imparting an appropriate degree of crosslinking to the silica sol, and may include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, diluted hydrofluoric acid, and the like, which may be used alone or in combination of two or more thereof.

By appropriately mixing the above components, it is possible to obtain a silica sol by a sol-gel reaction. The silica sol according to the present invention is mixed with the carbon nanotube dispersion prepared separately. In this case, mixing of the carbon nanotube dispersion and the silica sol may be performed at an appropriate ratio depending on the specific concentration of the carbon nanotubes in the dispersion or the specific concentration of the alkoxysilane compound in the silica sol. Preferably, it is preferable to mix so that the weight ratio of carbon nanotube: silicon oxide is about 1:10 to 1: 1 in the combined particles of the carbon nanotube and silicon oxide which are mixed and manufactured later. In the case where the weight ratio of carbon nanotubes to silicon oxide in the bonded particles is in the above range, it is preferable in view of processability, thermal conductivity and the like.

Next, the precipitate obtained from the mixed solution is filtered and dried to prepare a powder of particles in which carbon nanotubes and silicon oxide are combined (S3).

When the prepared silica sol is sufficiently mixed with the separately prepared carbon nanotube dispersion with stirring, a precipitate is produced. At this time, the process of removing the alcohol solvent and washing with water may be further subjected to necessity.

The obtained precipitate is filtered, and if necessary, distillation under reduced pressure is carried out to remove the solvent, thereby obtaining a powder of particles in which carbon nanotubes and silicon oxide are combined. In this case, when carbon nanotubes that are not acid treated are used, particles obtained by physically combining carbon nanotubes and silicon oxides are obtained. When carbon nanotubes that are acid treated are used, carbon nanotubes and silicon oxides are chemically bonded. You get the particles.

Next, the powder is mixed with the polymer resin and cured (S4).

As described above, the polymer resin may be used without any particular limitation. After mixing a polymer resin and the said powder, it can harden by an appropriate method according to the kind of specific polymer resin, and the thermally conductive resin composite of this invention can be obtained.

After mixing the polymer resin and the obtained powder may be further subjected to the step of molding the resin composite according to the specific use. After molding according to the required shape and the curing process can be produced a resin composite of the required form.

If necessary, the curing process may be performed by further including a curing agent. Specific types of the curing agent may be used without limitation, the curing agent used in the art according to the specific type and curing conditions of the polymer resin used. For example, a hexamethylenetetramine compound using a phenol resin as a polymer resin can be used as a curing agent, and when an epoxy resin is used, an amine compound can be used as a curing agent. As a more specific example of the amine compound, a low molecular amine compound and an amine adduct may be used, and these may be used in combination. As the low molecular amine compound, there may be mentioned a low molecular compound having a primary, secondary or tertiary amino group, and the amine adduct may be a carboxylic acid compound, a sulfonic acid compound, an isocyanate compound, a urea compound or an epoxy resin compound. The compound which has an amino group obtained by making an amine compound react is meant.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but these examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims, which are within the scope and spirit of the present invention. It is apparent to those skilled in the art that various changes and modifications can be made to the present invention, and such modifications and changes belong to the appended claims.

Example  One

<Preparation of Carbon Nanotube Dispersion>

The carbon nanotubes (SA100, NanoSolution Co., Ltd.), synthesized by the arc discharge method, were rotated at a speed of 5-20 rpm, a temperature of 420 ° C., and an oxidizing gas of 250 mW / min using a rotary kiln rotary reactor having an inclination angle of 3 °. Heat treatment for 100 minutes at the feed rate was used to the carbon nanotubes with a carbon impurity content of 15%. 0.08 parts by weight of the carbon nanotube, 0.08 parts by weight of sodium dodecylbenzenesulfonate (NaDDBS) and 99.90 parts by weight of water were mixed and treated with an ultrasonic disperser for 30 minutes. The treated solution was centrifuged at 6,000 rpm for 12 minutes to prepare a carbon nanotube dispersion.

< Silica sol  Manufacturing>

20.83 g of tetraethoxysilane, 46 g of ethanol, 0.36 g of aqueous hydrochloric acid solution (0.18% aqueous solution), and 7.2 g of water (DI) were mixed for 24 hours to prepare a sol-gel reaction.

<Production of Carbon Nanotube-Silicon Oxide Bond Particles>

The prepared carbon nanotube dispersion and silica sol were mixed in a weight ratio of 10: 1, ethanol was removed using a rotary evaporator, and washed with ammonia water. After the precipitate was produced it was filtered and dried to obtain a powder of carbon nanotube-silicon oxide bonding particles.

< Thermal conductivity  Resin Composite Manufacturing>

13.9 parts by weight of the prepared powder is mixed with 100 parts by weight of epoxy resin (YD128, Kukdo Chemical) and 25 parts by weight of a curing agent (KFH-150, Kukdo Chemical), and after molding, a mold having a diameter of 25.4 mm and a thickness of 1 to 1.5 mm Injected into a 80 ℃ drier and the primary curing for 50 minutes and then subjected to secondary curing for 1 hour at 100 ℃ using a hot press to prepare a thermally conductive resin composite.

Example  2-5

A thermally conductive resin composite was prepared in the same manner as in Example 1, except that the carbon nanotube dispersion and the silica sol were prepared and mixed in the composition as shown in Table 1 below.

division Carbon Nanotube Dispersion (A)
(Unit is weight%) Silica sol (B)
(Unit is g) Mixed weight ratio of A and B
(A: B) Weight Ratio of CNT and Silicon Oxide in Bound Particles
(CNT: silicon oxide) Content of binder particles compared to 100 parts by weight of resin composite
(Parts by weight) CNT Dispersant water TEOS Water (DI) ethanol Acid catalyst Example 1 0.08 0.08 99.84 20.83 g 7.2 g 46 g 0.36 g  10: 1 1:10 10 Example 2 0.08 0.08 99.84 20.83 g 7.2 g 46 g 0.36 g 10: 1 1:10 25 Example 3 0.4 0.4 99.20 20.83 g 7.2 g 46 g 0.36 g 10: 1 1: 5 10 Example 4 0.8 0.8 98.40 20.83 g 7.2 g 46 g 0.36 g 10: 1 1: 1 10 Example 5 0.8 0.8 98.40 20.83 g 7.2 g 46 g 0.36 g 10: 1 1: 1 25 CNT: carbon nanotube heat-treated with SA100 (carbon impurity content: 15%)
Dispersant: NaDDBS
Acid catalyst: 0.18% hydrochloric acid aqueous solution

Comparative example  One

After mixing 13.9 parts by weight of carbon nanotube powder with 100 parts by weight of epoxy resin (YD128, Kukdo Chemical) and 25 parts by weight of a curing agent (KFH-150, Kukdo Chemical), a resin composite was prepared in the same manner as in Example 1.

Comparative example  2

2.5 parts by weight of carbon nanotube powder After mixing with 100 parts by weight of epoxy resin (YD128, Kukdo Chemical) and 25 parts by weight of a curing agent (KFH-150, Kukdo Chemical), a resin composite was prepared in the same manner as in Example 1.

Comparative example  3

A resin formed of an epoxy resin was prepared by mixing 100 parts by weight of an epoxy resin (YD128, Kukdo Chemical) and 25 parts by weight of a curing agent (KFH-150, Kukdo Chemical).

Experimental Example : Thermal conductivity measurement

Specimens for measuring thermal conductivity were prepared using the resin composites of the prepared examples and comparative examples. However, in Comparative Example 1, the curing of the resin did not proceed properly in the mold, and thus the specimen itself was not manufactured.

In the measurement of thermal conductivity, Inplane thermal conductivity was measured using Nanoflash (model name: NFA447) manufactured by Netzsch, Germany, and the results are shown in Table 2 below.

In Plane
(W / mK) Example 1 0.3 Example 2 0.5 Example 3 0.35 Example 4 0.7 Example 5 1.2 Comparative Example 2 0.15 Comparative Example 3 0.1

Referring to Table 2, it can be seen that the specimens of the examples are significantly superior in thermal conductivity than the comparative examples.

Specifically, it can be seen that the thermal conductivity is increased by at least 3 times and at most 12 times as compared with Comparative Example 3 without adding the carbon nanotubes.

In addition, it can be seen that the thermal conductivity is improved by at least about 2 times and at most 8 times compared to Comparative Example 2 in which the carbon nanotubes are added in the maximum content to prepare the specimen.

Claims (12)

A thermally conductive resin composite in which carbon nanotubes and silicon oxide-bonded particles are dispersed in a polymer resin.
The thermally conductive resin composite of claim 1, wherein the bond between the carbon nanotubes and the silicon oxide is a physical bond or a chemical bond.
The thermally conductive resin composite according to claim 2, wherein the chemical bond is a bond between a silicon oxide and a reactive group formed on the surface of the acid treated carbon nanotubes.
The thermally conductive resin composite of claim 1, wherein the particles are included in an amount of 30 parts by weight or less based on 100 parts by weight of the thermally conductive resin composite.
The method of claim 1, wherein the polymer resin is at least one selected from the group consisting of an epoxy resin, a phenol resin and a melamine resin thermosetting resin; Thermoplastic resins selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, polyvinyl chloride resins, polyamide resins, polyethylene terephthalate resins and acrylic resins; Or a thermally conductive resin composite thereof.
(S1) preparing a carbon nanotube dispersion;
(S2) preparing a mixture of the carbon nanotube dispersion and silica sol; And
(S3) filtering and drying the precipitate obtained from the mixed solution to prepare a powder of carbon nanotubes and silicon oxide combined particles; And
(S4) mixing and curing the powder with a polymer resin;
Method for producing a thermally conductive composite comprising a.
The method of claim 6, wherein the carbon nanotube dispersion comprises a carbon nanotube, a dispersant, and a dispersion medium.
The method of claim 7, wherein the carbon nanotubes are pre-acid treated or untreated carbon nanotubes.
The method of claim 7, wherein the dispersant is sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, or a mixture thereof.
The method of claim 6, wherein the silica sol is mixed with 2 to 15 mol of alcohol solvent, 2 to 5 mol of H ₂ O 2 and 0.001 to 0.01 mol of acid catalyst with respect to 1 mol of tetraalkoxysilane compound having 1-20 carbon atoms in the alkoxy group. Method for producing a thermally conductive composite formed.
The method of claim 6, wherein the polymer resin is at least one selected from the group consisting of an epoxy resin, a phenol resin and a melamine resin thermosetting resin; Thermoplastic resins selected from the group consisting of polyethylene resins, polypropylene resins, polystyrene resins, polyvinyl chloride resins, polyamide resins, polyethylene terephthalate resins and acrylic resins; Or a mixture thereof.
The method of manufacturing a thermally conductive composite according to claim 6, wherein the curing agent is further mixed in the step (S4).