KR20180077824A - A coating composition containing carbon nanotubes and a method for manufacturing the same - Google Patents

Abstract

An embodiment of the present invention provides: a coating composition which includes a solvent, water-dispersed polyurethane, and carbon nanotubes, wherein the water-dispersed polyurethane includes 30-50 wt% of polyurethane particles and the remainder of water, and the average particle size of the polyurethane particles is 1,000 nm or less; and a method for manufacturing the coating composition. The coating composition can realize the antistatic characteristics due to conductivity of the carbon nanotubes and can maintain the transparency due to the dispersing ability of the carbon nanotubes.

Description

FIELD OF THE INVENTION The present invention relates to a coating composition containing carbon nanotubes and a method for producing the coating composition.

The present invention relates to a coating composition comprising carbon nanotubes and a method of manufacturing the same.

Carbon nanotubes have geometrical characteristics of diameter of several to several tens of nanometers and high aspect ratio and consist of only sp ² bonds between carbon atoms and exhibit excellent mechanical strength, electrical conductivity, and thermal conductivity. .

Applications of carbon nanotubes can be broadly divided into strength / lightweight applications, electroconductive / thermoconductive applications, and environmental / energy applications. Examples of the strength / lightweight field include automobile parts, wind turbine blades, aluminum wheels, and airplane parts. Examples of the electric conductive / thermal conductive applications include semiconductor trays, conductive paints, transparent electrodes, A surface heating element, a tape reel, an electromagnetic wave shielding material, a tire, and the like.

Particularly, a conductive paint or coating liquid containing carbon nanotubes can be formed on a substrate by applying a carbon nanotube dispersion liquid containing, for example, carbon nanotubes, a solvent, and a dispersant onto a substrate and drying the dispersion. In order to improve the performance of such a conductive paint or coating liquid, attempts have been made to improve carbon nanotubes, dispersants and the like.

In addition, in order to use carbon nanotubes as conductive films or other various electronic devices, it is necessary to dissolve carbon nanotubes in a solution or a binder. However, carbon nanotubes have a strong van der waals force ), They tend to agglomerate in a bundle and collide with each other in the matrix. If the carbon nanotubes aggregate in the matrix, the carbon nanotubes can not exhibit their inherent properties or the uniformity of the properties of the carbon nanotubes may be lowered. In addition, due to the inherent characteristics of carbon nanotubes, there is a problem that it is difficult to obtain a dispersion in which carbon nanotubes are sufficiently dispersed only by using conventional commercial dispersants.

Japanese Patent Application Laid-Open No. 2009-163959 discloses a transparent conductive film containing an aromatic polymer as a dispersant having carbon nanotubes, hydrophilic groups, and hydrophobic groups having high affinity with carbon nanotubes. However, in order to industrially mass-produce such a transparent conductive film, industrial means such as continuously coating a large amount of carbon nanotube dispersion with a coating machine is required. In such a process, a high shear force is applied to the carbon nanotube dispersion at the time of coating, so that depending on the constitution of the carbon nanotube dispersion, aggregation occurs partially, and the aggregates are transferred to the film and defects are generated .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and it is an object of the present invention to provide an antistatic property due to conductivity of a carbon nanotube, and to provide a coating composition having transparency To provide a coating composition capable of directly exposing the color of a base material or mixing the base material with a pigment as needed to give a color to the base material, and a process for producing the same.

One aspect of the present invention relates to a water-dispersible polyurethane comprising a solvent, an aqueous dispersion polyurethane, and a carbon nanotube, wherein the water-dispersed polyurethane contains 30 to 50% by weight of polyurethane particles and water in a residual amount, 000 < / RTI >

In one embodiment, the average particle size of the polyurethane may be between 100 and 500 nm.

In one embodiment, the solvent may comprise 5-20% by weight of alcohol and the balance water.

In one embodiment, the viscosity of the water-dispersed polyurethane may be between 10 and 100 cps.

In one embodiment, the pH of the water-dispersed polyurethane may be between 7 and 9.

In one embodiment, the amount of the water-dispersed polyurethane may be 5 to 20% by weight based on the total weight of the coating composition.

In one embodiment, the content of the carbon nanotubes may be 0.01 to 0.1% by weight based on the total weight of the coating composition.

In one embodiment, the coating composition may further comprise from 0.1 to 1.0% by weight of a defoamer and from 0.01 to 0.1% by weight of a surfactant.

According to another aspect of the present invention, there is provided a method of manufacturing a carbon nanotube, comprising: (a) mixing a first solvent and a carbon nanotube to prepare a first mixture; And (b) mixing 5 to 20% by weight of the first mixed liquid, 5 to 20% by weight of an aqueous dispersion polyurethane, and a remaining amount of a second solvent, wherein the water- 50% by weight and a balance of water, and the average particle size of the polyurethane particles is 1,000 nm or less.

In one embodiment, the average particle size of the polyurethane may be between 100 and 500 nm.

In one embodiment, the first solvent may be water.

In one embodiment, the second solvent may comprise from 10 to 30% by weight of alcohol and the balance water.

In one embodiment, the viscosity of the water-dispersed polyurethane may be between 10 and 100 cps.

In one embodiment, the pH of the water-dispersed polyurethane may be between 7 and 9.

In one embodiment, 0.01 to 0.1% by weight of a surfactant may be further added based on the total weight of the first mixed solution in the step (a).

In one embodiment, 0.1 to 1.0% by weight of defoamer may be further mixed in step (b).

The coating composition according to one aspect of the present invention can provide an antistatic property to a substrate including a small amount of carbon nanotubes having excellent conductivity and is excellent in transparency to expose the color of the substrate as it is, The necessary color can be given. In addition, the coating composition is environmentally friendly because it contains water and / or a hydrophilic solvent as a dispersing medium.

In addition, the method for preparing a coating composition according to another aspect of the present invention maximizes the dispersibility of carbon nanotubes, thereby maintaining the transparency of the coating composition.

It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be deduced from the description of the invention or the composition of the invention set forth in the claims.

1 is an optical microscope image of a surface of a PET substrate coated with a coating composition according to Examples and Comparative Examples of the present invention.
2 is a photograph of a surface of a glass substrate coated with a coating composition according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Coating composition

One aspect of the present invention relates to a water-dispersible polyurethane comprising a solvent, an aqueous dispersion polyurethane, and a carbon nanotube, wherein the water-dispersed polyurethane contains 30 to 50% by weight of polyurethane particles and water in a residual amount, 000 < / RTI >

The solvent may comprise 5 to 20% by weight of alcohol and the balance water. The solvent that can be mixed with water in the coating composition may be selected from the group consisting of esters, ethers, alcohols, ketones, aromatic hydrocarbon solvents, and mixtures of two or more thereof, It can be daily, but it is not limited to this.

Examples of the ester-based solvent include, but are not limited to, ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, and 3-methoxybutyl acetate.

Examples of the ether-based solvent include, but are not limited to, methyl cellosolve, ethyl cellosolve, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether.

Examples of the alcohol-based solvent include, but are not limited to, ethanol, isopropanol, n-butanol, methyl alcohol, amyl alcohol and cyclohexanol.

Examples of the ketone-based solvent include cyclohexanone, methyl amyl ketone, diisobutyl ketone, and methyl ethyl ketone, but are not limited thereto.

Examples of the aromatic hydrocarbon-based solvent include, but are not limited to, benzene, toluene, xylene, and the like.

The average particle size of the polyurethane may be 1,000 nm or less, preferably 100 to 500 nm, and the viscosity may be 10 to 100 cps (30 ° C). The average particle size of the polyurethane is an important factor controlling the viscosity and solids content of the water-dispersed polyurethane.

If the average particle size of the polyurethane exceeds 1,000 nm, the polyurethane particles may agglomerate arbitrarily to cause an unnecessary defect, and transparency and dispersibility of the coating composition may be deteriorated by such aggregates.

As used herein, the term "water-dispersed polyurethane" refers to a composition in which polyurethane particles are dispersed in water, and "solid content" refers to polyurethane particles that are solid components contained in the water-dispersed polyurethane.

The water-dispersed polyurethane acts as a binder in the coating composition to improve the adhesion between the coating composition and the substrate. If the content of the water-dispersed polyurethane is less than 5% by weight based on the total weight of the coating composition, the adhesion of the coating composition to the substrate may be deteriorated. If the content of the water- Can be lowered.

The polyurethane is a main part of the water-dispersed polyurethane which is a component of the coating composition, and generally includes a polymer produced by the reaction of a compound having a hydroxyl group (-OH) and a compound having an isocyanate group (-NCO) In the present invention, it means a polymer obtained by an addition polymerization reaction of isocyanate and polyol.

Examples of the isocyanate include isophorone diisocyanate (IPDI), 4,4'-methylene dicyclohexyl diisocyanate (H ₁₂ MDI), 4,4'-diphenylmethane diisocyanate May be at least one selected from the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI), preferably isophorone diisocyanate Isophorone diisocyanate (IPDI) and 4,4'-methylene dicyclohexyl diisocyanate (H ₁₂ MDI) may be mixed and used.

The isophorone diisocyanate (IPDI) exhibits high egg yolk denaturation, high flexibility with excellent mechanical strength, excellent abrasion resistance, water resistance, and gloss and physical properties over time. The 4,4'-methylenedicyclohexyldiisocyanate (H ₁₂ MDI) is a structure in which hydrogen is added to MDI to convert an aromatic ring into an aliphatic ring, and is relatively good in reactivity and excellent in heat resistance.

The polyol may be at least one selected from the group consisting of polytetramethylene glycol (PTMG), polypropylene glycol (PPG), polycarbonate diol (PCD), and polyester polyol, (polyester polyol) may be a polymer obtained by polymerizing adipic acid and 1,4-butylene glycol (BG), and may preferably be polycarbonate diol (PCD) It is not.

The polycarbonate diol (PCD) are weather resistance, since the heat resistance and water resistance are excellent, and suitable for the production of coating compositions, in particular, isophorone diisocyanate (IPDI) and 4,4'-methylene di-cyclohexyl diisocyanate (H ₁₂ MDI ), It is possible to realize more excellent physical properties.

The coating composition can be used for imparting various functions in addition to the protection of the material, and the functions thereof can be remarkably reduced when an external material is penetrated or absorbed into the formed coating layer. Since various substrates differ in exposure environment and required properties, the polyol and isocyanate used in the polyurethane design can be appropriately selected so as to be suitably applied to the exposure environment of the substrate.

When the particle size of the water-dispersed polyurethane is within the above range, the viscosity of the water-dispersed polyurethane may be 10 to 100 cps (30 ° C), preferably 10 to 50 cps (30 ° C) May be 30 to 50% by weight based on the total weight of the water-dispersible polyurethane. If the viscosity and solid content of the water-dispersed polyurethane fall outside the above range, the flowability of the coating composition becomes excessively high, resulting in deterioration in workability, and thus the smoothness of the surface of the substrate coated with the coating composition is deteriorated .

The pH of the water-dispersed polyurethane may be 7 to 9, preferably 8 to 8.5. That is, the pH of the water-dispersed polyurethane may be weakly alkaline. By adjusting the pH of the water-dispersed polyurethane to the above range, the electrostatic repulsion between the carbon nanotubes, the surfactant, or between the carbon nanotubes and the surfactant increases, and stability against dispersibility and high shear force can be improved .

The pH of the water-dispersed polyurethane can be adjusted to a constant amount of an alkaline solution. Examples of the alkaline solution include ammonia, a solution of an organic amine, and the like. For example, the organic amine may be selected from the group consisting of ethanolamine, ethylamine, n-propylamine, isopropylamine, diethylamine, triethylamine, ethylenediamine, hexamethylenediamine, hydrazine, pyridine, piperidine, hydroxypiperidine And the like.

The carbon nanotubes may impart conductivity to the surface of the coating composition and the substrate coated with the coating composition to impart antistatic properties to the substrate. Since the coating composition must maintain transparency as well as conductivity, it is preferable that the carbon nanotube is provided so as not to lower the transparency of the coating composition while imparting antistatic properties.

The carbon nanotubes may be single wall carbon nanotubes, double wall carbon nanotubes, multi wall carbon nanotubes, truncated graphenes, A cup-stacked carbon nanofiber, and a mixture of two or more thereof, and preferably a small amount of conductive material and a corresponding antistatic property Lt; RTI ID = 0.0 > carbon nanotubes. ≪ / RTI >

For example, the content of the carbon nanotubes may be 0.01 to 0.1% by weight based on the total weight of the coating composition. If the content of the carbon nanotubes is less than 0.01% by weight, the conductivity may be deteriorated. If the content is more than 0.1% by weight, transparency of the coating composition may be deteriorated.

The coating composition may further comprise 0.1 to 1.0 wt% of a defoaming agent and 0.01 to 0.1 wt% of a surfactant. For example, the defoamer may be a silicone defoamer and the surfactant may be a fatty acid anionic surfactant.

The silicone defoamer generally refers to a polymer having a silicon-oxygen bond as a main chain, and can be understood as a concept including reactive silicon and non-reactive silicon in the present invention.

The silicone antifoaming agent may be included in an amount of 0.1 to 1.0 wt% based on the total weight of the coating composition. If the content of the silicone antifoaming agent is less than 0.1 wt%, it may be difficult to control the number and size of the pores in the coating layer due to the decrease of the antifoaming action. If the amount is more than 1.0 wt%, the durability and flexibility of the coating layer may be deteriorated.

The silicone defoamer may comprise 2 to 10 parts by weight of reactive silicon and 0.1 to 5 parts by weight of unreacted silicon. Particularly, when the content of the non-reactive silicone is less than 0.1 parts by weight, the long-term durability and storage stability of the coating composition may be deteriorated.

As used herein, the term "reactive silicon" refers to a silicone resin to which a reactive functional group such as an epoxy group, an amino group, or a carboxyl group is bonded to a polysiloxane main chain composed of silicon and oxygen and can be cured by heat, Or "silicone rubber ".

The reactive silicon may be used alone or in combination of two or more kinds of curable silicones having different molecular weights or may be mixed with a curable silicone having another functional group.

For example, the reactive silicon may be polymethylhydrosiloxane (PMHS), hydroxyl terminated polydimethylsiloxane (PDMS), or a mixture thereof, but is not limited thereto.

The term "non-reactive silicone" as used herein is also referred to as "non-curable silicone resin" or "silicone oil " since it is a silicone resin to which a non-reactive functional group such as a methyl group is bonded to the polysiloxane main chain.

The non-reactive silicone acts as a lubricant. When used alone, the reactive silicone tends to be worn and does not have adhesiveness. However, when used in combination with the reactive silicone, the reactive silicone compensates for abrasion resistance and adhesion lacking in the non- And the non-reactive silicon can improve the long-term durability and non-stickiness of the coating composition, thereby reducing the frictional force of the substrate surface.

For example, the non-reactive silicon may be polydimethylsiloxane (PDMS), but is not limited thereto.

Method for producing coating composition

According to another aspect of the present invention, there is provided a method of manufacturing a carbon nanotube, comprising: (a) mixing a first solvent and a carbon nanotube to prepare a first mixture; And (b) mixing 5 to 20% by weight of the first mixed liquid, 5 to 20% by weight of an aqueous dispersion polyurethane, and a remaining amount of a second solvent, wherein the water- 50% by weight and a balance of water, and the average particle size of the polyurethane particles is 1,000 nm or less.

In the step (a), the first mixture may be prepared by mixing the first solvent and the carbon nanotubes. That is, the first mixed solution may be a carbon nanotube dispersed in a solvent. The content of the carbon nanotubes in the first mixed solution may be 0.1 to 5.0 wt%, preferably 0.1 to 1.0 wt%.

The first solvent may be water, and 0.01 to 0.1% by weight of a surfactant may be further added based on the total weight of the first mixed solution to improve dispersibility of the carbon nanotubes.

The carbon nanotube mixed in the first solvent may be uniformly dispersed in the first solvent by an external factor such as ultrasonic waves, a ball mill, a bead mill, a homogenizer, or a combination thereof, Lt; / RTI >

In the step (b), a coating composition having the composition described above can be obtained by mixing 5 to 20% by weight of the first mixed solution, 5 to 20% by weight of the water-dispersed polyurethane, and a remaining amount of the second solvent. If necessary, 0.1 to 1.0 wt% of defoamer may be further mixed in the step (b). The second solvent may comprise 10 to 30% by weight of alcohol and the balance water.

The average particle size of the polyurethane, the viscosity of the water-dispersed polyurethane, the pH, the solid content, the action and effect of each component and the kind thereof are as described above.

Hereinafter, embodiments of the present invention will be described in detail.

Example  One

2 g of a fatty acid-based anionic surfactant was added to 996 g of deionized water to prepare a mixed solution. Then, 2 g of carbon nanotube powder was added, and a power output energy of 250 W (W) was measured using a horn- For 0.5 hour to prepare a suspension in which the carbon nanotube powder was uniformly dispersed.

Example  1-1 to 1-3 and Comparative Example  1-1

70 g of a solvent mixed with deionized water and ethanol at a weight ratio of 80:20, 0.5 g of silicone defoamer, 14.5 g of water-dispersed polyurethane and 15 g of the suspension obtained in Example 1 were mixed to prepare a coating solution.

Example  2

2 g of a fatty acid-based anionic surfactant was added to 996 g of deionized water to prepare a mixed solution. Then, 2 g of carbon nanotube powder was added and the mixture was treated with a bead-mill for 8 hours to uniformly disperse the carbon nanotube powder A dispersed suspension was prepared. Here, the bead embedded in the bead-mill is a zirconia ceramic material having an average particle size of 1.2 mm.

Example  2-1 to 2-3 and Comparative Example  2-1

70 g of a solvent mixed with deionized water and ethanol at a weight ratio of 80:20, 0.5 g of silicone antifoam, 14.5 g of water-dispersed polyurethane and 15 g of the suspension obtained in Example 2 were mixed to prepare a coating solution.

Example  3-1

65 g of a solvent mixed with deionized water and ethanol at a weight ratio of 80:20, 0.5 g of silicone defoamer, 14.5 g of water-dispersed polyurethane, 15 g of the suspension obtained in Example 1 and 5 g of blue pigment were mixed to prepare a coating solution.

The specifications and physical properties of the water-dispersed polyurethane used in Examples and Comparative Examples are shown in Table 1 below.

division Solids Viscosity (@ 30 ℃) pH Polyurethane
Average particle size Example 1-1 35wt% 50 cps 8.5 100 nm Examples 1-2 35wt% 50 cps 8.5 500 nm Example 1-3 35wt% 50 cps 8.5 1,000 nm Comparative Example 1-1 35wt% 50 cps 8.5 1,100 nm Example 2-1 35wt% 50 cps 8.5 100 nm Example 2-2 35wt% 50 cps 8.5 500 nm Example 2-3 35wt% 50 cps 8.5 1,000 nm Comparative Example 2-1 35wt% 50 cps 8.5 1,100 nm Example 3-1 35wt% 50 cps 8.5 100 nm

Experimental Example  One

The coating solutions prepared in Examples 1-1 to 1-3 and Comparative Example 1-1 were coated on a PET film (90% transparency) substrate and dried at 80 ° C for 30 seconds. The appearance of the surface of the PET film coated with the coating liquid was photographed by an optical microscope and is shown in Fig. The surface resistance and transparency of the PET film coated with the coating liquid were measured, and the results are shown in Table 2 below.

division Surface resistance (log Ω / sq) Transmittance (%) Example 1-1 5.6 86.81 Examples 1-2 6.1 87.44 Example 1-3 8.2 88.72 Comparative Example 1-1 9.0 89.08

Referring to FIG. 1, the smoothness of the surface of Examples 1-1 to 1-3 was better than that of Comparative Example 1-1. In Comparative Example 1-1, as the average particle size of the polyurethane exceeded 1,000 nm, these particles coalesced arbitrarily and unnecessary defects occurred.

In addition, referring to Table 2, it is expected that Examples 1-1 to 1-3 are higher in conductivity than Comparative Example 1-1 and thus have excellent antistatic properties. On the other hand, although the transparency of Examples 1-1 to 1-3 is somewhat lower than that of Comparative Example 1-1, since the transparency of Examples 1-1 to 1-3 is low enough to expose the hue on the surface of the substrate after coating, The required color can be easily implemented.

Experimental Example  2

The coating liquid prepared in Example 3-1 was coated on a glass substrate and dried at 80 DEG C for 30 seconds. A photograph of the appearance of the surface of the glass substrate coated with the coating solution is shown in Fig. The surface resistance of the PET film coated with the coating liquid was measured, and the results are shown in Table 3 below.

division Surface resistance (log Ω / sq) Example 3-1 5.6

Referring to FIG. 2 and Table 3, the coating solution of Example 1-1 had excellent transparency, so that a certain amount of pigment was added to maintain necessary conductivity while achieving required color. Therefore, the present invention can be advantageously applied not only to the case where the color of the substrate surface must be maintained, but also when the color of the substrate surface needs to be changed by coating.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (16)

A solvent, a water-dispersed polyurethane, and a carbon nanotube,
Wherein the water-dispersed polyurethane comprises 30 to 50% by weight of polyurethane particles and the balance water,
Wherein the average particle size of the polyurethane particles is 1,000 nm or less. The method according to claim 1,
Wherein the average particle size of the polyurethane is 100 to 500 nm. The method according to claim 1,
Wherein the solvent comprises from 5 to 20% by weight of alcohol and the balance water. The method according to claim 1,
Wherein the water-dispersed polyurethane has a viscosity of 10 to 100 cps. The method according to claim 1,
Wherein the pH of the water-dispersed polyurethane is 7 to 9. The method according to claim 1,
Wherein the water-dispersed polyurethane content is 5-20 wt% based on the total weight of the coating composition. The method according to claim 1,
Wherein the content of the carbon nanotubes is 0.01 to 0.1% by weight based on the total weight of the coating composition. The method according to claim 1,
Wherein the coating composition further comprises 0.1 to 1.0% by weight of a defoamer and 0.01 to 0.1% by weight of a surfactant. (a) preparing a first mixed solution by mixing a first solvent and a carbon nanotube; And
(b) 5 to 20% by weight of the first mixed solution, 5 to 20% by weight of an aqueous dispersion polyurethane, and a remaining amount of a second solvent,
Wherein the water-dispersed polyurethane comprises 30 to 50% by weight of polyurethane particles and the balance water,
Wherein the average particle size of the polyurethane particles is 1,000 nm or less. 10. The method of claim 9,
Wherein the average particle size of the polyurethane is 100 to 500 nm. 10. The method of claim 9,
Wherein the first solvent is water. 10. The method of claim 9,
Wherein the second solvent comprises 10 to 30% by weight of alcohol and the balance water. 10. The method of claim 9,
Wherein the viscosity of the water-dispersed polyurethane is 10 to 100 cps. 10. The method of claim 9,
Wherein the pH of the water-dispersed polyurethane is 7 to 9. 10. The method of claim 9,
Wherein the surfactant is further mixed with 0.01 to 0.1% by weight based on the total weight of the first mixed solution in the step (a). 10. The method of claim 9,
And 0.1 to 1.0% by weight of an antifoaming agent is further mixed in the step (b).

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