KR20130104869A - Coating composition for shielding electromagnetic wave comprising graphene - Google Patents

Abstract

PURPOSE: A coating composition for shielding electromagnetic waves is provided to improve shielding capability of electromagnetic waves, dispersibility and storage stability, to facilitate the process of spray-coating, and to prevent operational degradation induced by oxidation. CONSTITUTION: A coating composition for shielding electromagnetic waves comprises planar graphene powder, binder resin, and a solvent. The graphene powder has a width of 5 to 10 nm, lengths of 5 to 20 micron in X-axis and Y-axis respectively, and a specific surface area of 100 to 500 m^2/mg. The binder resin is water-dispersible polyurethane dispersion or water-dispersible polyurethane acrylic copolymer dispersion. The solvent is a mixture solvent of a solvent having a boiling point below 200 °C and a solvent having a boiling point above 200 °C.

Description

Coating composition for electromagnetic wave shielding including plate-shaped graphene {COATING COMPOSITION FOR SHIELDING ELECTROMAGNETIC WAVE COMPRISING GRAPHENE}

The present invention relates to a coating composition for shielding electromagnetic waves, including plate-shaped graphene, and more specifically, to a conductive material, including graphene having a nano-unit plate-like structure, electrical conductivity characteristics, adhesion to the lower substrate, coating characteristics, shielding The present invention relates to a conductive coating composition having excellent properties and the like.

Normally, electromagnetic waves refer to electric and magnetic wavelengths including electric and magnetic fields generated by the electric and electronic products used around us, and can cause various harmful effects. For example, electromagnetic waves can cause noise due to radio wave interference between transmitting and receiving devices, decrease efficiency and lifespan of internal electronics, and disturbances between electronic devices. Is being seriously discussed.

In addition, the electromagnetic wave may affect the human body, and the weak electromagnetic wave acts to stimulate the nervous system by the thermal action and the induced current in the body to increase the body temperature or the whole body part when reaching the human body. Seriously, strong electromagnetic waves can cause heart disease and chemical changes in the blood that can affect the human body.

In addition to strengthening the shielding standard against such harmful electromagnetic waves, regulations on the emission of electromagnetic interference (EMI) are being tightened, and as a result, shielding measures are emerging as an important task not only for various electronic devices and components but also for electric vehicles.

One of the methods for preventing the damage of electromagnetic waves is an electromagnetic shielding coating agent, and nickel, copper, silver and the like, which are usually metal powders, are dispersed in a binder such as acrylic, urethane, and epoxy to form a coating agent. These products are generally coated using a spray coating, and can be coated on various materials in a relatively easy process, and the conductivity can be adjusted according to the metal content.

Recently, the high performance of the electromagnetic wave shielding coating for spray is required, and in particular, it is gradually being water-based while reducing the content of the organic solvent in accordance with the tendency to environment-friendly. The spray coating method is spray coating a coating liquid containing a mixture of a high molecular weight aqueous binder and a conductive powder on a substrate, and the conductive coating film obtained by spray coating has excellent conductivity, substrate adhesion, abrasion resistance, environmental resistance, etc. It must be secured.

However, the disadvantage of spray coating is that the resistance is higher than the plating and deposition method, and the thickness of the coating film is generally about 30 μm, which may be a problem in uniformity during coating. In addition, in the case of metal powder, except for silver, a reduction in the shielding effect by oxidation has been reported for a long time, and thus there is a limitation in use.

Due to these shortcomings, the use of silver as a metal powder is generally used to solve the problem of metal oxidation and high resistance. However, as the raw material price of silver has soared recently, the market using silver as a raw material is shrinking. .

Therefore, it is necessary to develop a material that can overcome the disadvantages of the metal-based conductive shielding coating composition and take advantage of high workability, and the like, and a carbon-based material is most discussed as an alternative material.

In order to replace such metal powder, Korean Patent Laid-Open Publication No. 2009-0057726 dissolves a resin and carbon nanotubes in a solvent and sonicates, and then prepares a polymer / carbon nanotube composite using an extruder to produce a composite having excellent electromagnetic shielding efficiency. It explains how to do it. The method using carbon nanotubes can show conductivity by increasing the probability of contact between nanotubes even with a small amount due to the characteristics of carbon nanotubes.However, when orientation occurs during extrusion, the uniformity of conductivity decreases and the conductivity is as high as expected. There is a disadvantage that can not be represented.

In addition, Korean Patent Laid-Open Publication No. 10-2011-0078265 discloses a thermoplastic resin composition having electromagnetic wave shielding properties including a metal composite in which a metal is coated on a resin and fibrous carbon. Metal-coated form of the fibrous carbon has the advantage of ensuring excellent electrical conductivity and high shielding efficiency. However, the fibrous carbon has a disadvantage in that the processability is poor when the dispersion stability and spray coating is not easy to prepare a coating composition.

In order to solve the above problems, an object of the present invention is to provide a coating composition for shielding electromagnetic waves by applying a graphene material that can partially replace the metal powder and overcome the disadvantages of the existing carbon-based material.

The present invention also aims to provide an electromagnetic shielding method using the coating composition and the electromagnetic shielding article manufactured by the shielding method.

In order to achieve the above object,

a) plate-shaped graphene powder;

b) binder resin; And

c) Solvent

It provides a coating composition for electromagnetic shielding comprising a.

In another aspect, the present invention provides an electromagnetic shielding method characterized in that the coating composition is coated on a substrate.

The present invention also provides an electromagnetic shielding article manufactured by the electromagnetic shielding method.

Electromagnetic shielding coating composition comprising a plate-shaped graphene powder according to the present invention to replace the conventional metal powder-based electromagnetic shielding coating composition can bring high electromagnetic shielding efficiency, dispersibility, storage stability and spray coating processability It is excellent and can prevent the performance deterioration by oxidation in advance, and it is excellent in chemical stability and low cost, and can be applied to a wide range of applications.

Electromagnetic shielding coating composition of the present invention is characterized in that it comprises a plate-shaped graphene particles, a binder resin and a solvent.

Each component is demonstrated below.

a) graphene particles

The plate-like graphene powder used in the present invention has a plate-like structure in which the graphene sheets are layered, the thickness is 5-100 nm, and the X and Y axes are each independently 5-40 um. Also preferably, the specific surface area is 100 m 2 / mg or more, preferably 100-500 m 2 / mg. If within the above range can be satisfied at the same time electromagnetic shielding ability, dispersibility, storage stability and spray coating property when applied to the coating composition.

In the present invention, the plate-shaped graphene powder may be a commercially available graphene powder, for example, N002, N006, N008 of Angstrom (USA), C500 series of XG Science (USA), and the like. Can also be used.

In the electromagnetic wave shielding coating composition of the present invention, the content of the a) plate-shaped graphene powder may be 3-20% by weight. In the above range, it is preferable because it can satisfy all the electromagnetic wave shielding ability, dispersibility, storage stability and spray coating property.

b) binder resin

As the binder resin usable in the present invention, a binder resin usable in the electromagnetic wave autism composition may be used. Preferably, it is preferable to use a water-dispersed polyurethane dispersion or a water-dispersed polyurethane acrylate copolymer dispersion. In general, plate-like graphene has a high specific surface area and thus has a high viscosity even when a small amount is added, resulting in poor coating and dispersibility. However, when the polyurethane dispersion or the polyurethane acrylate copolymer dispersion is used, the surface of a) is a conductive material. Dispersion stability can be maintained while increasing the amount of metal plate-bound graphene powder used. As a specific example, a polyurethane or a polyurethane acrylate copolymer having a molecular weight of 1,000 to 5,000,000 may be added to a single or mixed solvent such as water, DMF (dimethylformamide), NMP (methyl pinionidinone), and IPA (isopropyl alcohol). Dispersed at 20-40% by weight can be used.

In the present invention, the amount of the binder resin is preferably used in an amount of 10 to 30% by weight of the electromagnetic shielding coating composition, and if it is within the above range can satisfy all of the electromagnetic shielding ability, dispersibility, storage stability and spray coating properties. have.

c) Solvent

In the present invention, the solvent used in the electromagnetic wave shielding composition may be used as long as it is compatible with the plate-shaped graphene powder and binder resin having a metal bonded to the surface thereof, and preferably has a boiling point of less than 200 ° C. It is preferable to use a mixture of a low boiling point solvent and a high boiling point solvent having a boiling point of 200 ° C. or higher. The mixing ratio may be arbitrarily adjusted at the time of mixing. Preferably, the low boiling point solvent: high boiling point solvent ratio is 10-90%: 90-10% by weight. If it is within the above range can be further improved adhesion to the substrate during spray coating.

Examples of the low boiling point solvent include alcohols. Examples of the high boiling point solvent include glycols and polar solvents such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, ethylene glycol monomethyl ether, and ethylene glycol mono. Ethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, glycerol, terpinol, n-methylpyrrolidone , Gamma butyrolactone, dimethyl sulfoxide, propylene carbonate, ethylene carbonate, dimethylformamide and the like can be used alone or in combination of two or more thereof.

In the electromagnetic wave shielding coating composition of the present invention, the content of the solvent is preferably used in an amount of 50 to 80% by weight, and in the above range, it may satisfy all of the electromagnetic wave shielding ability, dispersibility, storage stability, and spray coating property. .

In addition, the electromagnetic shielding coating composition of the present invention may further include a metal powder. Including a metal powder is more useful when a shielding efficiency of 50 dB or more is required, such as a mobile phone or an electric vehicle. In the present invention, the metal powder may be used in the conductive shield composition, and may be used commercially, of course, may be used as a specific example, silver, nickel or copper powder, preferably the average of the metal powder It is preferable that the particle size (D50) is 0.1-3 탆.

For example, in the case of silver powder, a commercially available one can be used or directly synthesized, and it is preferable to use one having an average particle size (D50) of less than 1 μm so as to realize low resistance even at a low temperature.

In addition, copper powder may be synthesized and used, and copper nanoparticles having an amine of 40-500 nm size adsorbed or remaining on the surface may be prepared and used. The copper nanoparticles prepared herein are copper nanoparticles prepared by reducing and then reducing copper complex compounds using limited organic amines. The copper nanoparticles can control the size of the particles by controlling the type of amine, and as the alkalinity increases, Copper nanoparticles have the advantage that the oxide film is suppressed.

In the present invention, the content of the metal powder is preferably 0.1-10% by weight, and when added in an excessive amount, the price is high and dispersion stability is lowered. In particular, in the case of copper powder, it is a cause of lowering the oxidation stability. desirable.

In addition, the electromagnetic wave shielding coating composition of the present invention may further include a flow additive (a rheology modifier) to control the viscoelasticity of the composition, for example, a modified amide and a urea oligomer may be used, in which case 0.1 to 5% by weight Preferably used in amounts.

In addition, the electromagnetic wave shielding coating composition of the present invention may further include a conventional additive that can be added to the electromagnetic wave shielding composition.

The present invention provides an electromagnetic shielding method and an electromagnetic shielding article prepared by the method, characterized in that the coating composition for electromagnetic shielding coating on a substrate, the coating method can be applied well known coating methods It is preferable to use a spray coating method.

The electromagnetic wave shielding method according to the present invention can provide an electromagnetic wave shielding conductive film having excellent coating properties, excellent electromagnetic shielding performance and excellent durability and excellent weather resistance even after coating on an electronic device.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1

6.4 g of plate-shaped graphene (Angstron, USA, N006 series) were placed in 30.4 g of isopropyl alcohol and dispersed for 10 minutes through an ultrasonic sprayer. 28 g of water-dispersed polyurethane disperse was added to the graphene dispersion solvent, followed by stirring at 1000 rpm for 30 minutes. 6 g of ethanol and 30 g of terpinol as a high boiling point solvent were added thereto, mixed at 1000 rpm for 10 minutes, and a commercially available fluid additive (BYK) was added thereto, followed by stirring at 1000 rpm for 10 minutes to prepare a coating composition.

After adjusting the viscosity of the prepared coating composition with ethanol to enable spray coating, the PET film was spray-coated to the specimen to have a dry coating thickness of 20 μm, and the coated specimen was dried in a 100 ° C. drying furnace for 15 minutes.

Example 2

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 1 except for using N008 series of Angstron, USA as plate-shaped graphene.

Example 3

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 1, except that US graph paper (XG Science Co., C500 series) was used as the plate-shaped graphene powder.

Example 4

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 1, except that a commercially available polyurethane acrylate copolymer dispersion was used instead of the water-dispersed polyurethane dispersion.

Example 5

6.2 g of commercially available graphene (Angstron, USA, N006 series) and 3 g of silver powder having an average particle size (D50) of 1 to 3 µm were placed in 29.5 g of isopropyl alcohol, Dispersed for a minute. 28 g of water-dispersed polyurethane disperse was added to the graphene dispersion solvent, followed by stirring at 1000 rpm for 30 minutes. To this, 5 g of ethanol and 25 g of terpinol were added as a high boiling point solvent, followed by mixing for 10 minutes at 1000 rpm, followed by addition of 2 g of a commercially available fluid additive (BYTI, ANTI-TERRA 203), followed by stirring at 1000 rpm for 10 minutes. To prepare a coating composition.

Except for the above description, in the same manner as in Example 1, the prepared coating composition was coated and dried on the specimen.

Example 6

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 5 except that copper powder having an average particle size (D50) of 1 to 3 μm was used as the metal powder.

Example 7

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 5, except that oxidation-resistant nano copper powder having an average particle size (D50) of less than 1 μm was used as the metal powder.

Example 8

A coating composition and a specimen coated with the composition were prepared in the same manner as in Example 5 except for using silver nano powder having an average particle size (D50) of less than 1 μm as the metal powder.

Comparative Example 1

18.4 g of silver powder having an average particle size (D50) of 1 to 3 μm was added to 29.5 g of isopropyl alcohol and dispersed for 10 minutes through an ultrasonic sprayer. 28 g of water-dispersed polyurethane disperse was added to this silver dispersion solvent and stirred at 1000 rpm for 30 minutes. To this, 5 g of ethanol and 15.8 g of terpinol were added as a high boiling point solvent, followed by mixing for 10 minutes at 1000 rpm, followed by 2 g of a commercially available fluid additive (BYTI, ANTI-TERRA 203), which was stirred at 1000 rpm for 10 minutes. To prepare a coating composition.

Except for the above description, in the same manner as in Example 1, the prepared coating composition was coated and dried on the specimen.

Comparative Example 2

A coating composition and a specimen coated with the composition were prepared in the same manner as in Comparative Example 1 except that copper powder having an average particle size (D50) of less than 1 μm was used as the metal powder.

Test Example 1

The physical properties and performance of the specimens coated with the coating compositions according to Examples 1 to 8 and Comparative Examples 1 and 2 were carried out as follows, and the results are shown in Table 1 below.

1) Resistance: The surface resistance per unit area was measured by a sheet resistance meter.

2) Hardness: Measured using a pencil hardness tester.

3) Oxidation Stability: The resistance was measured while storing the specimen for 72 hours in an oven maintained at 85 ° C./85% humidity.

4) Adhesion: Tape adhesion was evaluated according to ASTM D3359.

5) Storage stability: The precipitation of the particles was visually observed while the prepared coating composition was stored at room temperature (25 ° C.).

resistance
(Ω / ㎠) Hardness
(Pencil hardness) Oxidation stability
(80 ℃ / 85% -72 hours) Adhesion Storage stability
(3 months) Example 1 70 HB No change 100% stability Example 2 100 HB No change 100% stability Example 3 70 2H No change 100% stability Example 4 5 1H No change 100% stability Example 5 15 1H No change 100% stability Example 6 20 1H No change 100% stability Example 7 10 1H No change 100% stability Example 8 150 HB No change 100% stability Comparative Example 1 One 1H 10% increase in sheet resistance 100% Stored for 1 month or longer Comparative Example 2 20 1H 50% increase in sheet resistance 100% Stored for 1 month or longer

As shown in Table 1, the conventional metal powder-based electromagnetic shielding coating for the electromagnetic wave has a disadvantage in that the storage stability and the oxidation stability of the coating film, while the coating composition for electromagnetic shielding including the graphene according to the present invention is chemical It was confirmed that it was excellent in stability and exhibited the same physical properties as the initial stage.

Claims (13)

a) plate-shaped graphene powder;
b) binder resin; And
c) solvent
Electromagnetic shielding coating composition comprising a. The method of claim 1,
a) 3-30% by weight of plate-like graphene powder;
b) 10-30% by weight of binder resin; And
c) 50-80 wt% solvent
Electromagnetic shielding coating composition comprising a. The method of claim 1,
The graphene powder has a thickness of 5-100 nm, the size of the X-axis and Y-axis independently of the coating composition for electromagnetic shielding, characterized in that 5-20 um. The method of claim 1,
The graphene powder has a specific surface area of 100-500 m 2 / mg coating composition for electromagnetic shielding.
The method of claim 1,
B) The coating composition for electromagnetic wave shielding, wherein the binder resin is a water dispersion polyurethane dispersion or a water dispersion polyurethane acrylic copolymer dispersion. The method of claim 5,
The water-dispersed polyurethane dispersion or water-dispersed polyurethane acrylic copolymer dispersion is a polyurethane or polyurethane acrylate copolymer having a molecular weight of 1,000-5,000,000 in water, DMF (dimethylformamide), NMP (methyl pinonidinone) , IPA (isopropyl alcohol) coating composition for electromagnetic shielding, characterized in that dispersed in 20-40% by weight in a single or mixed solvent. The method of claim 1,
The solvent is a coating composition for electromagnetic shielding, characterized in that the mixed solvent of a boiling point of less than 200 ℃ low boiling point solvent and a boiling point of 200 ℃ or more high solvent. The method of claim 7, wherein
The low boiling point solvent and the high boiling point solvent is 10-90: 90-10, characterized in that the coating composition for electromagnetic shielding, characterized in that the mixture. The method of claim 1,
Electromagnetic shielding coating composition, characterized in that it further comprises a metal powder. 10. The method of claim 9,
The metal powder is silver, nickel or copper powder coating composition for electromagnetic shielding. The method of claim 1,
Electromagnetic shielding coating composition, characterized in that it further comprises a flowable additive. A method of shielding electromagnetic waves, wherein the coating composition according to any one of claims 1 to 11 is coated on a substrate. The electromagnetic wave shielding article manufactured by the electromagnetic shielding method of Claim 11.