KR20150125300A - Methods for preparing thermally conductive carbon fillers - Google Patents

Abstract

The present invention relates to a method for producing a thermally conductive carbon-based filler. More specifically, the method comprises the steps of: producing a catalyst composition by adding organic acid, metal precursor, and a promoter in distilled water; producing a carbon-based compound dispersed liquid by adding and dispersing a surfactant and a carbon-based compound in distilled water; mixing the catalyst composition and the dispersed liquid; forming a metal catalyst by plasticizing the mixed solution, and adhering the metal catalyst on the carbon-based compound; and growing a carbon nanotube on a surface of the metal catalyst through chemical vapor deposition (CVD). The thermally conductive carbon-based filler has excellent thermal conductivity, and a carbon nanotube can be easily grown without using a separate carrier.

Description

METHODS FOR PREPARING THERMALLY CONDUCTIVE CARBON FILLERS [0002]

The present invention relates to a method for producing a thermally conductive carbon-based filler.

Carbon nanotubes exhibit a cylindrical shape with a graphite surface, and are excellent in thermal and electrical properties. In recent years, research and development activities of composites using carbon nanotubes have been progressing actively, and they have been widely applied to devices such as thermally conductive members, electron emission devices, electronic devices, sensors, and the like. And is widely used.

Since such carbon nanotubes are generally expensive, it is required to synthesize carbon nanotubes in a large amount at low cost in order to be useful in various fields. However, in order to obtain a desired thermal conductivity and electrical conductivity with a small amount of carbon nanotubes, the carbon nanotubes themselves are greatly affected by not only the characteristics of the resin and the processing conditions but also the properties of the carbon nanotubes themselves. Therefore, carbon nanotubes with high purity and high productivity are required, and development of catalysts for these is very important.

Methods for synthesizing carbon nanotubes generally include electric discharge, laser deposition, high pressure vapor deposition, and atmospheric pressure thermochemical vapor deposition. Among them, the electric discharge method and the laser evaporation method are simple and easy to apply, but they contain a lot of impurities in synthesis and are not suitable for mass production. On the other hand, thermochemical synthesis is the most suitable method for synthesizing high purity carbon nanotubes in large quantities at low cost.

When synthesizing nanotubes through thermochemical synthesis, the catalyst plays a very important role. For example, the growth of carbon nanotubes varies depending on the type and composition ratio of the transition metal and the size of the metal particles. As the transition metal, Fe, Co, Ni or the like is used and supported on a carrier to synthesize the transition metal. As a specific synthesis method, a coprecipitation method in which a catalyst material is uniformly dissolved in an aqueous solution and is carried on a carrier through adjustment of the pH, or the dissolved solution is dried, then polished for uniformly carrying the metal catalyst again, And an impregnation method in which synthesis is performed by calcination at a high temperature of 700 ° C to 900 ° C for 6 to 10 hours for a long time.

Carbon nanotubes grown by the method using a carrier include a carrier in the final product. However, the carrier itself does not have an excellent heat conduction efficiency and thus has a problem of deteriorating the efficiency of the carbon nanotubes. That is, the improvement of the heat conduction efficiency and the ease of growth of the carbon nanotubes are both unsatisfactory.

Korean Patent No. 1094454 discloses a catalyst for synthesizing carbon nanotubes and carbon nanotubes synthesized thereby, but fails to satisfy the required properties.

Korean Patent No. 1094454

An object of the present invention is to provide a method for producing a carbon-based filler excellent in thermal conductivity.

It is an object of the present invention to provide a method for producing a carbon-based filler in which carbon nanotubes can be easily grown without using a separate carrier.

Another object of the present invention is to provide a thermally conductive carbon-based filler produced by the above production method.

Another object of the present invention is to provide a thermally conductive member comprising the thermally conductive carbon-based filler.

1. preparing a catalyst composition by adding an organic acid, a metal precursor and a cocatalyst to distilled water;

Adding a surfactant and a carbon-based compound to distilled water and dispersing the dispersion to prepare a carbon-based compound dispersion;

Mixing the catalyst composition and the dispersion;

Firing the mixed solution to form a metal catalyst and attaching the metal catalyst to the carbon-based compound; And

Growing carbon nanotubes on the surface of the metal catalyst by chemical vapor deposition (CVD);

Based filler.

2. The method for producing a thermally conductive carbon-based filler according to 1 above, wherein the organic acid is citric acid, isocitric acid or a mixture thereof.

3. The method of 1 above, wherein the metal precursor is _{Fe (NO 3) 3 · 9H} 2 O, Ni (NO 3) 2 · 6H 2 O, CoSO 4 · 7H 2 O and _{Cu (NO 3) 2 · 3H} 2 O Wherein at least one of the thermally conductive carbon-based fillers is at least one selected from the group consisting of silicon carbide and silicon carbide.

4. The method for producing a thermally conductive carbon-based filler according to 1 above, wherein the co-catalyst is (NH ₄ ) ₂ MoO ₄ .4H ₂ O, (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O, .

5. The process for producing a thermally conductive carbon-based filler according to 1 above, wherein the catalyst composition comprises 70 to 95% by weight of an organic acid, 1 to 15% by weight of a metal precursor and 1 to 15% .

6. The method of producing a thermally conductive carbon-based filler according to item 1 above, wherein the carbon-based compound is carbon nano-flake, expanded graphite, expanded graphite or a mixture thereof.

7. The process for producing a thermally conductive carbon-based filler according to item 1, wherein the surfactant is at least one selected from the group consisting of sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, triton exabback and polyvinylpyrrole. Way.

8. The method for producing a thermally conductive carbon-based filler according to 1 above, wherein the carbon-based compound contained in the carbon-based compound dispersion is contained in an amount of 50 to 90% by weight based on the total weight of the solid content of the dispersion.

9. A thermally conductive carbon-based filler produced according to any one of claims 1 to 8 above.

10. A thermally conductive member comprising the thermally conductive carbon-based filler of claim 9 and a polymer matrix in which the filler is dispersed.

11. The polymer of claim 10, wherein the polymer is at least one selected from the group consisting of an epoxy resin, an unsaturated polyester resin, a polycarbonate resin, a polyethylene resin, a polystyrene resin, a polyethylene terephthalate resin, a polyvinyl chloride resin and a polyvinylidene chloride resin Wherein the thermally conductive carbon-based filler is one of the thermally conductive carbon-based fillers.

The present invention can produce a carbon-based filler having excellent thermal conductivity.

Further, the present invention can easily grow carbon nanotubes without using a carrier.

The present invention relates to a process for preparing a catalyst composition, which comprises preparing a catalyst composition by adding an organic acid, a metal precursor and a cocatalyst to distilled water; Adding a surfactant and a carbon-based compound to distilled water and dispersing the dispersion to prepare a carbon-based compound dispersion; Mixing the catalyst composition and the dispersion; Firing the mixed solution to form a metal catalyst and attaching the metal catalyst to the carbon-based compound; And growing the carbon nanotubes on the surface of the metal catalyst by chemical vapor deposition (CVD). Thus, the carbon nanotube can be easily grown without using a separate carrier, And a method for producing the carbon-based filler.

Hereinafter, the present invention will be described in detail.

< Thermal conductivity  Carbon-based Filler  Manufacturing method>

Preparation of catalyst composition

First, an organic acid, a metal precursor and a cocatalyst are sequentially added to distilled water to prepare a catalyst composition.

Organic acid

The organic acid used in the present invention is a component that assists in dissolving the metal precursor and cocatalyst and prevents the precipitation of the composition by controlling pH and improves the stability of the composition.

The kind of the organic acid used in the present invention is not particularly limited as long as it is within the range of its function, and examples thereof include citric acid and isocitric acid. These organic acids may be used singly or in combination of two or more.

The content of the organic acid is not particularly limited and may be, for example, 70 to 95% by weight, and preferably 80 to 93% by weight based on the total weight of the solid content of the catalyst composition. When the above-mentioned range is satisfied, the components of the catalyst composition are dissolved well and the precipitate does not occur and can be stably maintained.

Metal precursor

The metal precursor used in the present invention is a component that functions as a metal catalyst to help grow carbon nanotubes.

Type of metal precursor used in the present invention is not limited in particular if the range of the capabilities, for _{example, Fe (NO 3) 3 ·} 9H 2 O, Ni (NO 3) 2 · 6H 2 O, CoSO 4 · 7H ₂ O, Cu (NO ₃ ) ₂ · 3H ₂ O, etc. These may be used alone or in combination of two or more.

The content of the metal precursor is not particularly limited, but may be, for example, 1 to 15% by weight, preferably 0.5 to 10% by weight based on the total weight of the solid content of the composition. When the above range is satisfied, the carbon nanotube growth can be effectively controlled, and the metal precursor can be uniformly distributed in the composition to exhibit uniform physical properties (thermal conductivity).

Co-catalyst

The co-catalyst used in the present invention is a component that controls the diameter and yield of carbon nanotubes by controlling the activity of the catalyst.

The co-catalyst used in the present invention is not particularly limited as long as its function is within the range of its function. For example, the co-catalyst includes (NH ₄ ) ₂ MoO ₄ .4H ₂ O, (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O, etc. These may be used alone or in combination of two or more.

The content of the cocatalyst is not particularly limited, but may be, for example, 1 to 15% by weight, preferably 0.5 to 10% by weight, based on the total weight of the solid content of the composition. When the above range is satisfied, the diameter and the yield of the carbon nanotubes can be maintained in an appropriate range.

The catalyst composition used in the present invention may further contain additives as needed in addition to the above components, provided that the scope of the present invention does not depart from the scope of the present invention.

The temperature for carrying out the step of preparing the catalyst composition is not particularly limited, but may be from 30 to 100 ° C, preferably from 45 to 80 ° C, from the viewpoint of improving the solubility of the components contained in the catalyst composition.

In addition, the time for carrying out the step of preparing the catalyst composition is not particularly limited, but may be, for example, 10 to 60 minutes.

Carbon-based compound dispersion preparation step

Distilled water is put in a separate container, and a surfactant and a carbon-based compound are added and dispersed to prepare a carbon-based compound dispersion.

Surfactants

The surfactant used in the present invention is a component that effectively disperses the respective components in the composition, increasing the stability of the metal precursor ions and preventing agglomeration of the catalyst so that the carbon-based compound can be evenly adhered between the metal catalysts. Also, the specific surface area of the catalyst in which the carbon nanotubes are grown is increased. The carbon nanotubes can be effectively grown even when no separate carrier is used.

The kind of the surfactant to be used in the present invention is not particularly limited as long as the function of the surfactant is within the range of its function. For example, sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, These may be used alone or in combination of two or more. Specific examples of commercially available surfactants according to the present invention include a Triton X-bag.

The content of the surfactant is not particularly limited and may be, for example, 10 to 50% by weight, and preferably 30 to 40% by weight based on the total weight of the solid matter of the dispersion. If the content of the surfactant is less than 10%, the dispersion stability of the carbon-based compound may be deteriorated. If the content of the surfactant is more than 50%, the thermal conductivity may be deteriorated due to residues remaining at the time of firing.

The dispersion method is not particularly limited, but can be carried out, for example, for 1 minute to 1 hour in an ultrasonic apparatus (Sonic bath).

Carbon-based compound

The carbon-based compound used in the present invention is added to further improve the thermal conductivity of the filler, and improves the thermal conductivity of the filler together with the carbon nanotubes grown on the surface of the catalyst in combination with the metal catalyst.

The carbon-based compound used in the present invention may be carbon nano-flake, expanded graphite, expanded graphite, or a mixture thereof, and the carbon nanoflake may include graphene, oxide graphene, and the like.

The content of the carbon-based compound is not particularly limited and may be, for example, 50 to 90% by weight, and preferably 60 to 70% by weight based on the total weight of the solid matter of the dispersion. When the above range is satisfied, the thermal conductivity of the filler formation can be further improved by being evenly dispersed in the composition. However, if it exceeds 90%, dispersion is difficult and the composition becomes inhomogeneous and physical properties such as thermal conductivity may be lowered somewhat.

Mixing of the catalyst composition and dispersion

Thereafter, a step of mixing the prepared catalyst composition and the carbon-based compound dispersion is carried out.

Through the mixing step, the metal precursor can be adjacent to the surface of the carbon-based compound in which the surfactant is dispersed in the dispersion. Thereafter, the metal catalyst can be adhered to the surface of the carbon- do.

The mixing ratio of the mixing step is not particularly limited and may be, for example, from 180 to 250 parts by weight, preferably from 200 to 220 parts by weight, based on 100 parts by weight of the catalyst composition. When the above range is satisfied, the thermal conductivity can be further improved by keeping the growth density of the synthesized carbon nanotube in a proper range.

Metal catalyst formation and adhesion with carbon-based compounds

The present invention includes a step of firing a mixed solution of the catalyst composition and the carbon-based compound to form a metal catalyst, and attaching the metal catalyst to the carbon-based compound.

In the above step, the metal precursors are crystallized in the composition as a metal catalyst and the metal catalyst is adhered to the surface of the carbon-based compound at a proper ratio through the firing process, thereby preventing the metal catalyst from lowering the thermal conductivity by itself . In addition, since the carbon nanotubes grow between the interface of the carbon-based compound and the metal catalyst to function as a linking ring, the thermal conductivity of the prepared filler can be remarkably improved.

On the other hand, the distilled water in the composition during the calcination process does not evaporate and remain in the final formed composite.

The firing temperature is 300 to 500 ° C, preferably 400 to 450 ° C. When the firing temperature satisfies the above range, damage due to oxidation of the carbon-based compound can be prevented.

The present invention may further include drying the composite subjected to the calcination process, and may further include a step of grinding the powdery composite by using a blender after the drying step.

Carbon nanotube growth stage

The present invention includes a step of growing carbon nanotubes on the surface of the metal catalyst by chemical vapor deposition (CVD).

In this step, carbon nanotubes are formed on the surface of the metal catalyst. Since the metal catalyst is attached to the carbon-based compound, carbon nanotubes can be grown on the surface of the carbon-based compound.

The chemical vapor deposition (CVD) in the above step is a conventional method used for growing carbon nanotubes. The carbon atom source used in the above process is a hydrocarbon gas such as methane, ethylene, acetylene, LPG, But is not limited thereto.

< Thermal conductivity  Absence>

The present invention also relates to a thermally conductive member comprising the thermally conductive filler produced according to the production method of the present invention and the polymer matrix in which the filler is dispersed.

The polymer used in the present invention is not particularly limited as long as the thermally conductive filler can be easily dispersed. Examples of the polymer include epoxy resin, unsaturated polyester resin, polycarbonate resin, polyethylene resin, polystyrene resin, polyethylene terephthalate Resins, polyvinyl chloride resins, polyvinylidene chloride resins, and the like, and it is preferable to use an epoxy resin in terms of improving the thermal conductivity.

The thermally conductive member of the present invention can be applied to a heat dissipation member of an electronic device, a battery case, an electronic device case, a heat sink, and the like, but is not limited thereto.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example  And Comparative Example

Example  One

800 ml of distilled water was placed in a 2 L beaker, and the mixture was heated to 50 캜. Then, 6.061 g of citric acid, 0.258 g of Fe (NO ₃ ) ₃ .9H ₂ O and 0.438 g of (NH ₄ ) ₂ MoO ₄ .4H ₂ O And the mixture was stirred for 20 minutes to dissolve to prepare a catalyst composition.

Thereafter, 400 ml of distilled water was added to a separate 1-liter beaker, and the mixture was heated to 50 ° C, 10 g of sodium dodecylsulfonate was added to the beaker, stirred for about 10 minutes until completely dissolved, Was added and dispersed in a bath sonic for 10 minutes.

Thereafter, the catalyst composition and dispersion were mixed and stirred for 15 minutes.

The mixed solution was charged into an electric furnace, and the temperature of the electric furnace was set to 450 DEG C, followed by combustion at 450 DEG C for 1 hour. After one hour, the contents inside the electric furnace were poured into an iron boat and dried at room temperature to obtain a powdery catalyst.

The powdery catalyst was put in a chemical vapor chamber and heated to 900 ° C. Then, a mixed gas of hydrogen and methane was injected into the chamber to grow carbon nanotubes on the surface of the metal catalyst to produce a carbon-based filler.

4.5 g of the carbon-based filler prepared above was added to 5.5 g of an epoxy resin (trade name: KFR-120, a hardener (KFH-150), and a mixing ratio (subject: hardener = 4 g: 1.5 g, After dispersing for 1 hour using a mixer, it was put into molds for the preparation of specimens with diameters of 25 mm and 1.5 mm. The molds were semi-cured at 70 ° C under a pressure of 80 ° C for 15 minutes using a hot press, , And completely cured at 70 atmospheric pressure for 1 hour to prepare a thermal conductivity measurement specimen (In-Plane).

Example  2

A specimen for thermal conductivity measurement was prepared in the same manner as in Example 1, except that cetyltrimethylammonium bromide was used instead of sodium dodecylsulfonate as a surfactant.

Example  3

A specimen for thermal conductivity measurement was prepared in the same manner as in Example 1, except that expanded graphite was used instead of graphene nanoflake as the carbon-based compound.

Comparative Example  One

4.5 g of graphene nanoflakes was added to 5.5 g of epoxy resin [trade name: KFR-120 (trade name), hardener (KFH-150), mixing ratio (subject: hardener = 4 g: 1.5 g, After the mixture was dispersed for 1 hour, it was put into molds for the preparation of specimens of 25 mm and 1.5 mm in diameter. The molds were semi-cured at 70 ° C under a pressure of 70 at 80 ° C for 15 minutes. (In-Plane) for thermal conductivity measurement was prepared by fully curing at atmospheric pressure for 1 hour.

Comparative Example  2

Specimens for thermal conductivity measurement were prepared in the same manner as in Comparative Example 1 except that expanded graphite was used instead of graphene nanoflake.

Test Methods

Thermal conductivity  Evaluation test

Thermal conductivity (W / mK) was measured using Netzsch LFA 457 specimens for thermal conductivity measurement prepared in Examples and Comparative Examples, and the results are shown in Table 1 below.

division Thermal conductivity Example 1 35.2 Example 2 32.3 Example 3 25.1 Comparative Example 1 17.5 Comparative Example 2 10.6

With reference to Table 1, using the surfactant (Examples 1 to 3) prepared according to the present invention, the carbon nanotubes were easily grown on the surface of the carbon-based compound and the catalyst without a separate carrier, It was confirmed that it represents the city.

On the other hand, in the case of Comparative Examples 1 and 2 using only the carbon-based compound, it was confirmed that the thermal conductivity was significantly lowered compared with the examples

Claims (11)

Adding an organic acid, a metal precursor and a cocatalyst to distilled water to prepare a catalyst composition;
Adding a surfactant and a carbon-based compound to distilled water and dispersing the dispersion to prepare a carbon-based compound dispersion;
Mixing the catalyst composition and the dispersion;
Firing the mixed solution to form a metal catalyst and attaching the metal catalyst to the carbon-based compound; And
Growing carbon nanotubes on the surface of the metal catalyst by chemical vapor deposition (CVD);
Based filler.
The method of producing a thermally conductive carbon-based filler according to claim 1, wherein the organic acid is citric acid, isocitric acid, or a mixture thereof.
The method according to claim 1, wherein the metal precursor is composed of _{Fe (NO 3) 3 · 9H} 2 O, Ni (NO 3) 2 · 6H 2 O, CoSO 4 · 7H 2 O and _{Cu (NO 3) 2 · 3H} 2 O Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt;
The method of producing a thermally conductive carbon-based filler according to claim 1, wherein the co-catalyst is (NH ₄ ) ₂ MoO ₄ .4H ₂ O, (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O, or a mixture thereof.
The method of producing a thermally conductive carbon-based filler according to claim 1, comprising 70 to 95% by weight of an organic acid, 1 to 15% by weight of a metal precursor, and 1 to 15% by weight of a cocatalyst, based on the total weight of the solid content of the catalyst composition.
The method of manufacturing a thermally conductive carbon-based filler according to claim 1, wherein the carbon-based compound is carbon nano-flake, expanded graphite, expanded graphite, or a mixture thereof.
The method of producing a thermally conductive carbon-based filler according to claim 1, wherein the surfactant is at least one selected from the group consisting of sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, Triton X-bag and polyvinylpyrrole.
The method of producing a thermally conductive carbon-based filler according to claim 1, wherein the carbon-based compound contained in the carbon-based compound dispersion is contained in an amount of 50 to 90% by weight based on the total weight of the solid content of the dispersion.
A thermally conductive carbon-based filler produced according to any one of claims 1 to 8.
A thermally conductive member comprising the thermally conductive carbon-based filler of claim 9 and a polymer matrix in which the filler is dispersed.
[Claim 11] The method of claim 10, wherein the polymer is at least one selected from the group consisting of an epoxy resin, an unsaturated polyester resin, a polycarbonate resin, a polyethylene resin, a polystyrene resin, a polyethylene terephthalate resin, a polyvinyl chloride resin and a polyvinylidene chloride resin , A method for producing a thermally conductive carbon-based filler.