KR101187653B1 - Method for manufacturing superhydrophobic surface - Google Patents
Method for manufacturing superhydrophobic surface Download PDFInfo
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- KR101187653B1 KR101187653B1 KR20100070202A KR20100070202A KR101187653B1 KR 101187653 B1 KR101187653 B1 KR 101187653B1 KR 20100070202 A KR20100070202 A KR 20100070202A KR 20100070202 A KR20100070202 A KR 20100070202A KR 101187653 B1 KR101187653 B1 KR 101187653B1
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Abstract
The present invention is to prepare a porous organic gel (organogel) using 1,3,5-alkoxybenzene and formaldehyde (formHO, HCHO) or paraformaldehyde, to produce a superhydrophobic surface and a superhydrophilic surface It is about.
In the method of preparing a superhydrophobic surface according to the present invention, a step of reacting 1,3,5-alkoxybenzene and formaldehyde under a catalyst to generate a porous organic gel, substituting the solvent of the wet gel, and the solution is based on It comprises a step of coating on.
Since the superhydrophobic surface manufacturing method according to the present invention has strong physical properties and chemical resistance, it can be usefully used in various industrial fields in which a superhydrophobic surface can be applied, such as an automatic cleaning function and an organic material separation function in an aqueous solution.
Description
The present invention relates to a method for producing a superhydrophobic surface.
In general, the contact angle is the angle at which the free surface of the liquid forms the solid plane when the liquid is in contact with the solid, and is determined by the cohesion between the liquid molecules and the adhesion between the liquid and the solid. When the contact angle between the liquid and the solid plane exceeds 90 °, the solid plane is hydrophobic, which has a low affinity with water. When the contact angle between the liquid and the solid plane is less than 90 °, the solid plane has affinity with water. It is hydrophilic in nature.
On the other hand, when the contact angle of any material with the solid plane exceeds 150˚, it is called superhydrophobic, which has a particularly low affinity with water, and when the contact angle with the solid plane is less than 10˚, It is called superhydrophilic, which has a particularly high affinity. The superhydrophobic coating has a self-cleaning property that is not easily adhered even if foreign matters such as dust and bacteria come to the surface because the contact area is very small, and is easily removed by simple cleaning even if stuck.
The hydrophobicity or hydrophilicity of a material is determined by surface roughness and surface energy. The Wenzel formula, which is the theory explaining the wettability, describes the relationship between contact angle and surface curvature as shown in Equation 1 below. define.
[Equation 1]
cos θ '= r cos θ
In the formula, r is surface curvature, θ 'is the contact angle of the curved surface, θ is the contact angle of the flat surface.
Since surface curvature r exceeds 1, when θ is smaller than 90 °, θ 'becomes smaller than θ and hydrophilicity is increased. When θ is larger than 90 °, θ' becomes larger than θ and hydrophobicity is increased.
Therefore, a prerequisite for obtaining hydrophobic and hydrophilic surfaces is that the surface curvature must be high. When low surface energy is added to a plane having high surface curvature, it becomes superhydrophobic, and high hydrophilicity is added when high surface energy is added to a plane having high surface curvature.
Surface curvature is produced by the micro or nano structure of the surface, and methods such as mechanical machining, plasma etching, and casting are used to generate the micro or nano structure.
Surface energy can be increased or decreased by chemical processes. Specific methods include plasma polymerization, wax solidification, anodic oxidation of metal, solution precipitation, Korea Publication 10-2009-0012567), chemical vapor deposition, addition of sublimation material, phase separation and the like.
However, the mechanical method of forming the surface curvature has a small area that can be generated in a single process, and it takes a lot of time and cost when the large area is produced for industrial application, and the chemical method of forming the surface energy. Can be manufactured in a single process, but it must go through a complex process using multiple chemicals, and it is highly likely that impurities will penetrate when moving from one process to another, resulting in superhydrophobic or superhydrophilic There is a problem that the uniformity of the surface is lowered.
Conventionally, the surface was hydrophobicly treated using a polymer containing fluorine or silicon having a hydrophobic functional group having a small surface energy. As a specific example, Korean Patent Application No. 2006-7022073 includes (i) a fluorine compound and (ii) an ester derivative of alpha-hydroxy acid having a melting point of 35 ° C. or less and a water solubility of 25 ° C. or less of 10% by weight or less. The present invention relates to a method of applying at room temperature without heat treatment using an aqueous composition. Korean Patent Application No. 2004-0058301 discloses forming a weakly adhesive layer on one side of a film and carbon fluoride on the other side of the film. An antistatic coating layer containing 0.001 to 0.5 g / m 2 of resin is formed to easily remove foreign substances on the surface, and a surface protection film having a water repellent function capable of preventing a decrease in the antistatic function of the film during cleaning is introduced. It is.
That is, in the prior art as described above, the water-repellent function is provided by using a fluorine compound or a fluorine-containing polymer (fluorine resin), but the fluorine resin is expensive, and the process is complicated, and there is a problem in terms of economy. As part of efforts to solve these economic problems, a method of forming protrusions on the surface of the film using fluorine-substituted spherical silica particles has been introduced. However, this method also has poor abrasion resistance on the surface of the film. There is a problem of falling durability.
In addition, there is a method for preparing the surface of the nano-pore structure using a gel prepared by sol-gel synthesis reaction by resorcinol or phenol and formaldehyde catalysis. Since it contains many hydroxy groups, it is not suitable for manufacturing a superhydrophobic surface.
On the other hand, US Patent No. 7,291,653 discloses an organic airgel obtained by reacting 1,3,5-alkoxybenzene with formaldehyde or paraformaldehyde, but the airgel prepared by the method described in this document, when dried by heat, Because pores are not retained due to shrinkage due to capillary forces, this method is not suitable for nanostructure control to have a superhydrophobic structure.
Accordingly, the present invention is to overcome the limitations of the prior art as described above, and an object of the present invention is to provide a superhydrophobic surface manufacturing method capable of appropriately controlling the micro and nanopore structure of the surface.
The present inventors have found that the micro and nanopore structures of the surface can be appropriately controlled by controlling the catalytic reaction and solvent of alkoxybenzene and formaldehyde or paraformaldehyde to complete the present invention.
Accordingly, the above object of the present invention is achieved by the following.
a) reacting alkoxybenzene with formaldehyde or paraformaldehyde in the presence of a catalyst to prepare a porous organic gel,
b) replacing the solvent of the organic gel prepared in step a), and
c) coating the solution obtained in step b) onto the substrate.
Including,
The reaction solvent in step a) is a mixture of i) one solvent selected from the group consisting of tetrahydrofuran, dimethylsulfoxide and acetonitrile, and ii) alkanols having 8 or more carbon atoms,
In step a) the catalyst is an inorganic acid or an organic acid,
In step b), the organic gel obtained in step a) is substituted with a solvent selected from the group consisting of acetone, methanol, ethanol, propanol, heptane, pentane, nucleic acid and cyclohexane, the method of producing a super hydrophobic surface.
According to the present invention a method for producing a superhydrophobic surface is provided. In the present invention, by controlling the catalytic reaction and solvent of 1,3,5-alkoxybenzene and formaldehyde or paraformaldehyde, it is possible to appropriately control the micro and nanopore structure of the surface, which is a simpler process than the conventional method. And since it is possible to manufacture a high performance superhydrophobic surface at a low cost, it is possible to improve the product competitiveness in various industrial fields that require the production of a superhydrophobic surface.
In addition, the superhydrophobic surface manufacturing method according to the present invention can be applied to various manufacturing techniques of daily life, such as oil processing agent of the paper industry, functional inorganic powder of the cosmetic industry, water-repellent agent of the textile and leather industry, which requires superhydrophobic surface treatment, In addition, it can be applied to anti-fingerprint films of electronic products, corrosion-resistant materials of metal materials, automotive exterior coating materials, precision release technology in the field of polymer processing, heat exchangers of refrigerators, and various disaster prevention facilities, thereby improving the competitiveness of the entire industry. There is a technical effect that can be made.
1 is a photograph showing the contact angle measurement results of the superhydrophobic surface prepared according to Example 1.
2 is a graph showing a change in contact angle according to the amount of decanol.
3 is a graph showing a change in contact angle according to the molar ratio of alkoxybenzene and formaldehyde.
4 shows the change in the contact angle and the forward / backward adhesion angles when alkoxybenzene is used (Example 1) and when fluorine-substituted alkoxybenzene is used (Example 10) and when pore-forming molecules are not used (Comparative Example 1). This graph shows the difference.
Hereinafter, a method of preparing a superhydrophobic surface and a substrate having a superhydrophobic surface prepared by the method will be described in detail with reference to the accompanying drawings.
The present invention relates to a method for producing a superhydrophobic surface, the method
a) reacting alkoxybenzene with formaldehyde or paraformaldehyde in the presence of a catalyst to prepare a porous organic gel,
b) replacing the solvent of the organic gel prepared in step a), and
c) coating the solution obtained in step b) onto the substrate.
It includes.
The alkoxybenzene is benzene substituted with two or more alkoxy groups, and the substitution position of the alkoxy group may be 1,3- or 1,3,5-. The alkoxy group is an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, which is unsubstituted or substituted with one or more fluorine atoms. If the number of carbon atoms of the alkoxy group exceeds 20, the reactivity of the benzene ring is reduced, which is not preferable because it forms an oligomer having a low molecular weight.
The formaldehyde or paraformaldehyde uses a stock solution having a concentration of 36 to 38% by weight. Paraformaldehyde is decomposed into formaldehyde by heat or acid and thus can be used as a good formaldehyde source.
In step a), alkoxybenzene and formaldehyde or paraformaldehyde are reacted in a molar ratio of 1: 1 to 1: 4. The degree of crosslinking and the degree of compaction vary depending on the molar ratio of the reaction, and the pore size of the gel is controlled within the range of 0.5 nm to 5 nm.
The concentration of the reactants is preferably 0.5% to 40% by weight, preferably 10% to 40% by weight relative to the total weight of the reaction solution. If the reaction is diluted too much, the molecular weight of the product becomes small, and as a result, gelation does not proceed.
In step a), i) tetrahydrofuran (THF), dimethyl sulfoxide (DMF) and acetonitrile (acetonitrile) as a reaction solvent, and ii) pore formation for nanostructure formation. Alkanol (alkanol, C n H 2n + 1 OH, 8 ≦ n ≦ 12) as a molecule is used in combination. It is preferable to use the solvent of i) and the pore-forming molecules of ii) in a weight ratio of 1: 0.01 to 0.01: 10. According to the mixing ratio, the microstructure of the polymerized nanostructure varies, and the particle size increases as the amount of pore-forming molecules increases. By adjusting the mixing ratio in the above range, the particle size is controlled in the range of 5 nm to 500 nm.
The catalyst is an inorganic acid or an organic acid. The inorganic acid is selected from hydrochloric acid, sulfuric acid and nitric acid, and the organic acid is selected from the group consisting of acetic acid, trifluoroacetic acid and p-toluenesulfonic acid. The catalyst is suitable to use 0.1 to 2% by weight based on the total weight of the reaction solution.
In step a), when the reaction mixture is reacted in an oven at 70 to 90 ° C. for 24 to 48 hours, gelation proceeds while obtaining a slightly yellow mixture. Even if it is reacted for 48 hours or more, the gelation process has little effect, so the reaction time is preferably gelated in the above time range.
In step b), the organic gel obtained in step a) is immersed in a solvent having a low surface tension and then maintained at 20 to 40 ° C. for 2 to 6 hours. If necessary, this process can be repeated three times. The solvent having a low surface tension may be one or more selected from the group consisting of acetone, methanol, ethanol, propanol, heptane, pentane, nucleic acid and cyclohexane. In this step, the water present in the organic gel obtained in step a) is replaced with a solvent having a low surface tension.
In step c), the solution obtained in step b) is sprayed on the surface of the substrate, dip coating, flow coating, spin coating and slot-die. Coating is carried out by any one method selected from slot die coating. After completion of step b), it may be ultrasonicated at 100 W for 30 minutes to obtain a high viscosity fluid which can be used for coating in step c). The coating substrate may be both an inorganic and an organic substrate, and specific examples thereof include aluminum sheets, glass sheets, polymer films, and the like.
In the present invention, after completing the coating in step c), it may further comprise step d) drying for 1 minute to 24 hours in a temperature range of 20 to 120 ℃. Drying under these conditions allows the solvent to evaporate at a uniform rate so that a homogeneous coating film is formed on the surface of the substrate.
In addition, the present invention may further include a step e) of heat-treating the sample dried in step d) at 100 to 500 ℃ in air, whereby the coating layer can be densified.
Example
Hereinafter, the present invention will be described through the following examples. However, the examples are only for illustrating the present invention in detail, and the scope of the present invention is not limited to the scope of the following examples.
Example 1
0.168 g of 1,3,5-trimethoxybenzene, 0.16 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 5 g of 1-decanol and 1 g of tetrahydrofuran were mixed and then stirred for 30 minutes. Then, it was reacted with heating in an oven at 80 ° C. for 24 hours. The gel obtained was recovered from the reaction vessel and then soaked in ethanol for 24 hours. After removing the solvent again, the same process was repeated three times with ethanol to remove water. Substitute the solvent with acetone, sonicate at 100 W for 30 minutes, and then place the resulting fluid on a glass plate. Coating by casting method.
Example 2
In the same manner as in Example 1, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.16 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 4 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 3
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.16 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 3 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 4
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.24 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 5 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 5
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.24 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 4 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 6
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.24 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 3 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 7
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.32 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 5 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 8
In the same manner as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.32 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 4 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 9
In the same manner as in Example 1, using a mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.32 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 3 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Example 10
Same method as in Example 1 above, using a mixture of 0.168 g of 1,3,5-trifluoromethoxybenzene, 0.32 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, 5 g of 1-decanol, and 1 g of tetrahydrofuran Was carried out.
Comparative Example 1
A mixture of 0.168 g of 1,3,5-trimethoxybenzene, 0.16 g of 37% formaldehyde solution, 0.118 g of concentrated hydrochloric acid, and 5 g of tetrahydrofuran was carried out in the same manner as in Example 1 above.
The contact angles of the surfaces coated in Examples 1 to 10 and Comparative Example 1 were measured and shown in Table 1 below.
[Table 1]
In Table 1, CA static represents a positive contact angle, and CA adv / rec represents a forward / reverse contact angle (dynamic contact angle).
Figure 2 is a graph showing the experimental results of Examples 1 to 3, it can be seen that as the amount of decanol decreases the porosity is smaller, the contact angle is smaller. As shown in Figure 3, in Examples 1, 4 and 7, the porosity of the surface varies according to the molar ratio of alkoxybenzene and formaldehyde, the change in contact angle is less than 5 °, but the effect is not large, the amount of formaldehyde As the porosity decreases, the contact angle decreases. Figure 4 shows the experimental results of Examples 1 and 10 by changing the type of alkoxybenzene, the forward contact angle was increased by about 1 ° when using a benzene substituted with a fluorine atom (Example 10), the advancing The reverse contact angle hysteresis is 20 ° (169 ° -149 °) in Example 10 and 32 ° (169 ° -137 °) in Example 1, with fluorine-substituted alkoxybenzene improved slightly in terms of copper contact angle. It was confirmed.
Claims (16)
b) replacing the solvent of the organic gel prepared in step a), and
c) coating the solution obtained in step b) onto the substrate.
Including,
The reaction solvent in step a) is a mixture of i) one solvent selected from the group consisting of tetrahydrofuran, dimethylsulfoxide and acetonitrile, and ii) alkanols having 8 or more carbon atoms,
In step a) the catalyst is an inorganic acid or an organic acid,
In the step b), the organic gel obtained in step a) is substituted with a solvent selected from the group consisting of acetone, methanol, ethanol, propanol, heptane, pentane, nucleic acid and cyclohexane.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7291653B2 (en) * | 2001-05-18 | 2007-11-06 | The Regents Of The University Of California | Preparation of hydrophobic organic aeorgels |
| US20080015298A1 (en) | 2006-07-17 | 2008-01-17 | Mingna Xiong | Superhydrophobic coating composition and coated articles obtained therefrom |
| WO2010002859A2 (en) | 2008-06-30 | 2010-01-07 | Stc.Unm | A superhydrophobic aerogel that does not require per-fluoro compounds or contain any fluorine |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7291653B2 (en) * | 2001-05-18 | 2007-11-06 | The Regents Of The University Of California | Preparation of hydrophobic organic aeorgels |
| US20080015298A1 (en) | 2006-07-17 | 2008-01-17 | Mingna Xiong | Superhydrophobic coating composition and coated articles obtained therefrom |
| WO2010002859A2 (en) | 2008-06-30 | 2010-01-07 | Stc.Unm | A superhydrophobic aerogel that does not require per-fluoro compounds or contain any fluorine |
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