WO2021080032A1 - Superhydrophobic surface coating method - Google Patents

Abstract

The present invention relates to a superhydrophobic surface coating method which enables superhydrophobicity to be imparted on a surface by using plasma, and which has a simple manufacturing process. In addition, an air-purifying filter having a superhydrophobic surface is capable of primarily removing foreign bodies such as dust by means of the superhydrophobic properties thereof, and thus may exhibit enhanced filter performance, and has a self-cleaning effect.

Description

Superhydrophobic surface coating method

The present invention relates to a method for coating a superhydrophobic surface of an air purification filter.

Recently, a technology capable of effectively controlling the wetting behavior of a liquid on a solid surface is attracting attention in terms of scientific and industrial applications. The wettability of the surface of the material is determined by the surface energy, or by controlling the microstructure of the surface to a micro- and nano-level complex structure, the wettability is extremely reduced, and a super water-repellent surface with a contact angle of 150° or more with water can be realized. Most of the super-water-repellent surfaces are based on the superhydrophobic surface structure existing in nature. In general, natural materials having superhydrophobicity include lotus leaves, rice leaves, and wings of butterflies or cicadas. In fact, lotus leaves exhibit superhydrophobicity with a water contact angle of 161°, and this property is due to numerous micro and nano-level microscopic protrusions formed on the surface of the lotus leaf. The fine protrusions on the surface of the lotus leaf minimize the contact area with water, and are coated with a hydrophobic material to prevent water from entering between the protrusions. Foreign matter can be removed together. This is called the lotus leaf effect or the lotus effect, and it can be applied to various fields such as window film, solar cell film, ink for transparent electrode manufacturing, functional film for display, architectural exterior material, eyeglasses, lens, camera, and so on.

In order to implement a super-water-repellent surface, low surface energy and high surface roughness are required, and for this, a method having nano- or micro-sized roughness using nano-sized organic/inorganic particles has been reported. This is largely divided into two methods, and the first is a method of creating a nanostructured surface and coating a material with low surface energy.The micro-sized single-layer structure and the nano-sized in the single-layered structure are formed on the surface of the mold by chemical etching. After forming the groove structure, heat and pressure are applied to the etched mold to transfer the polymer structure and remove the transferred polymer structure from the mold. As nanomaterials, inorganic materials such as fluorine compounds, silica and carbon materials, metals, and polymer materials such as polypropylene and polystyrene are used. In general, fluorine-based compounds or polymers with low surface energy are widely used. However, this method has the advantage of realizing super water repellency by simply treating various types of material surfaces with materials having low surface energy. It is complex, it is difficult to mass-produce, and has a problem of low contact angle. The second method is a method of directly implementing a nanostructured surface using a material with low surface energy. This has the advantage of being able to implement the super-water-repellent nanostructured surface at once without any special treatment, but there is a problem that depends entirely on the properties of the material. In addition to this, various technologies for realizing superhydrophobicity are being developed, but they are still insufficient in terms of technology and economy.

On the other hand, among the methods of improving the material surface properties, plasma surface treatment technology is a method of changing the surface properties without affecting the basic properties.This method is limited to the surface layer and uniformly occurs, so the treated surface It has a wide range of advantages of surface treatment as it can treat all materials that are stable at low temperatures while being able to stably handle.

Accordingly, the present inventors completed the present invention by implementing a superhydrophobic surface through plasma polymerization as a result of conducting a study to impart excellent superhydrophobicity through a simple manufacturing process.

Reference Korean Patent Laid-Open No. 10-2018-0031248 was used as a prior art document.

The present invention was conceived to solve the above problem, and an object of the present invention is to provide a superhydrophobic surface coating method having a simple manufacturing process, excellent coating power, and high contact angle.

In addition, an object of the present invention is to provide a filter for air purification having an improved filter function since the surface is coated by the above coating method so that the surface is superhydrophobic, and thus foreign substances such as dust can be removed primarily.

In order to solve the above problems, the present invention includes: 1) mixing trimethylsilyl methacrylate and methyl methacrylate; 2) injecting the mixture together with gas into a plasma reactor and spraying the mixture onto the substrate; And 3) plasma treatment to perform plasma polymerization coating.

After step 3), the surface of the substrate has superhydrophobicity, and in step 1), trimethylsilyl methacrylate and methyl methacrylate are mixed in a 4:1 molar ratio.

The plasma is a low-temperature plasma, the plasma treatment time is 3 to 6 minutes, and the power is 15 W.

The gas contains nitrogen gas, and the substrate is made of glass, metal, nonwoven fabric, acrylic, spandex, polymer, ceramic, paper, plastic, silicone, wool, silk, cotton, flax, jute, wood, nylon, or activated carbon fiber. Includes.

In another aspect, the present invention provides an air purification filter coated by the coating method, and the surface of the air purification filter is characterized in that it is superhydrophobic.

According to the present invention, superhydrophobicity can be imparted to the surface by polymerizing coating using plasma, and the manufacturing process is simple, and the air purification filter having a superhydrophobic surface primarily removes foreign substances such as dust due to its superhydrophobic property. It is possible to improve the performance of the filter and has a self-cleaning effect.

1 shows a result of measuring a contact angle of a coated glass substrate according to an embodiment of the present invention.

Figure 2 shows the Raman measurement results of the coated glass substrate according to an embodiment of the present invention.

3 shows an SEM image of a coated glass substrate according to an embodiment of the present invention.

4 shows an SEM image of a nonwoven filter according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail. In describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

The present invention comprises the steps of 1) mixing trimethylsilyl methacrylate and methyl methacrylate; 2) injecting the mixture together with gas into a plasma reactor and spraying the mixture onto the substrate; And 3) plasma treatment to perform plasma polymerization coating.

After step 3), the surface of the substrate has superhydrophobicity.

In the step 1), trimethylsilyl methacrylate and methyl methacrylate are preferably mixed at a molar ratio of 4:1, and when not mixed at the molar ratio, a superhydrophobic surface may not be formed or superhydrophobic performance may be deteriorated.

It is preferable that the plasma is a low-temperature plasma. The plasma treatment time is preferably 3 to 6 minutes, more preferably 4 to 5 minutes, and most preferably 5 minutes. If the plasma treatment time is less than 3 minutes, plasma polymerization may not occur properly and coating may not be performed well, and if it is longer than 6 minutes, the substrate may be damaged.

The plasma power is preferably 15 W, and the gas is preferably nitrogen gas.

The substrate may include glass, metal, nonwoven fabric, acrylic, spandex, polymer, ceramic, paper, plastic, silicone, wool, silk, cotton, flax, jute, wood, nylon, or activated carbon fiber, but is limited thereto. no.

In addition, the present invention provides a filter for air purification coated by the coating method from another aspect, and the surface of the air purification filter is preferably superhydrophobic.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example 1. Preparation of coating composition

The main monomer methyl methacrylate (hereinafter abbreviated as MMA), trifluoromethyl methacrylate (hereinafter abbreviated as TFMA) and trimethylsilyl methacrylate (hereinafter abbreviated as TSMA) were mixed at the ratios shown in Table 1 below. In addition, dimethacrylate (hereinafter abbreviated as DMA) serving as a crosslinking agent was added in an amount of 10% for comparative analysis.

Table 1 below shows the ratio of each component of Examples (1) to (24).

ingredient Molar ratio DMA content relative to ingredients Example (1) TFMA:MMA 100:0 - Example (2) 80:20 - Example (3) 60:40 - Example (4) 40:60 - Example (5) 20:80 - Example (6) 0:100 - Example (7) 100:0 10% Example (8) 80:20 10% Example (9) 60:40 10% Example (10) 40:60 10% Example (11) 20:80 10% Example (12) 0:100 10% Example (13) TSMA:MMA 100:0 - Example (14) 80:20 - Example (15) 60:40 - Example (16) 40:60 - Example (17) 20:80 - Example (18) 100:0 10% Example (19) 80:20 10% Example (20) 60:40 10% Example (21) 40:60 10% Example (22) 20:80 10% Example (23) TFMA:TSMA:MMA 80:80:20 - Example (24) 80:80:20 10%

Example 2. Glass substrate coating

After putting 5 mL of the coating composition in the syringe, the syringe pump was connected to a low-temperature AC plasma device, and nitrogen gas was injected. Plasma polymerization coating was performed on the glass substrate at 0.1 mL/sec for 10 minutes, and the voltage of the plasma apparatus was fixed at 15 W/A.

Example 3. Superhydrophobicity evaluation

In order to evaluate the superhydrophobicity of Examples (1) to (24), the contact angle and transmittance of the glass substrate coated with the coating composition were measured for comparative analysis, and uncoated glass was used as a control.

Table 2 below shows the contact angle and transmittance measurement results.

Contact angle (°) Transmittance(%) UV(365nm) IR(940nm) VL(380~700nm) Example (1) 51.0 91.0 89.1 92.3 Example (2) 56.6 91.3 88.6 92.8 Example (3) 78.2 91.4 88.7 92.8 Example (4) 40.1 93.4 89.3 92.7 Example (5) 34.7 93.0 89.1 92.5 Example (6) 42.6 91.3 88.4 90.6 Example (7) 51.0 91.0 89.1 92.3 Example (8) 80.6 91.3 88.6 92.8 Example (9) 71.0 91.4 88.7 92.8 Example (10) 70.9 93.4 89.3 92.7 Example (11) 68.0 93.0 89.1 92.5 Example (12) 55.0 91.3 88.4 90.6 Example (13) 110 58.4 87.9 84.1 Example (14) 153 77.1 90.0 85.0 Example (15) 123 69.3 88.7 88.2 Example (16) 115 55.5 89.7 84.2 Example (17) 95.0 54.4 86.9 84.1 Example (18) 110 93.0 89.1 92.5 Example (19) 101 77.1 90.0 85.0 Example (20) 117 69.3 88.7 88.2 Example (21) 114 55.5 88.7 84.2 Example (22) 56.4 91.3 89.4 89.0 Example (23) 109 88.1 90.0 88.0 Example (24) 111 94.1 92.0 91.0 Control 18.5 99.0 99.0 99.0

Referring to Table 2 and FIG. 1, it can be seen that Examples (13) to (17) in which TSMA and MMA are mixed exhibited a high contact angle of approximately 110° or more and thus have excellent hydrophobicity. Among them, Example (14) in which TSMA and MMA were mixed at a ratio of 80:20 showed a spherical shape with a contact angle of 153°, and the result was the closest to superhydrophobicity. On the other hand, when TFMA and MMA are mixed, it can be seen that the contact angle is as low as 80° or less.

When DMA was added to the mixture of TFMA and MMA, it still showed a low contact angle, and when DMA was added to TSMA:MMA, Example (20) mixed at a ratio of 60:40 showed a high contact angle close to superhydrophobicity at 117°. Indicated. In addition, Example (23) exhibited a contact angle of 109° and Example (24) of 111°, and it was confirmed that the mixing of the crosslinking agent DMA did not significantly affect the hydrophobic properties.

On the other hand, it can be seen that the uncoated glass substrate has very low hydrophobicity at 18.5°.

Example 4. Coating confirmation evaluation

1) Raman analysis

2 shows the Raman analysis results of the coated glass substrate, and it can be seen that the coating composition was coated on the glass substrate by confirming the ^{1000 cm -1 peak indicating CH bonding.}

2) Scanning electron microscope (SEM) analysis

SEM images of the front and side surfaces of the glass substrate coated with the coating composition were compared and analyzed through a scanning electron microscope (SEM). As shown in FIG. 3, it was confirmed that plasma-polymerized precursors were coated on the surface of the glass substrate. Fig. 3(a) shows an embodiment (3), Fig. 3(b) shows an embodiment (8), Fig. 3(c) shows an embodiment (20), Fig. 3(d) shows an embodiment (14), and Fig. 3 (e) is an SEM image of Example (23), and FIG. 3 (f) is an Example (24).

When comparing TFMA and TSMA, when TSMA is mixed, it can be seen that more plasma-polymerized precursors are attached to the glass substrate, and the degree of adhesion according to the presence or absence of a crosslinking agent is similar.

On the other hand, when TFMA and TSMA were mixed, more precursors were formed than when TFMA was added alone, but the amount of precursors formed decreased rather than when TSMA was added alone. When the crosslinking agent was added by mixing TFMA and TSMA, it was found that more precursors were formed than when the crosslinking agent was not added. It is judged not to give.

Example 5. Air Purification Filter Manufacturing Example and Characteristic Evaluation

A coating composition in which TSMA:MMA was mixed at 80:20 was subjected to plasma polymerization to coat the surface of the nonwoven fabric. In addition, after adding 4% of the thermal initiator AIBN to the coating composition in which TSMA:MMA was mixed at 80:20, the nonwoven filter was immersed in the solution, dried, and thermally polymerized at 70° C. for 3 minutes with a UV lamp. The coated nonwoven filter was measured by SEM to confirm the degree of coating.

4(a) is an SEM image of a non-woven filter that is not coated, and it can be seen that the non-woven fiber is not coated. 4(b) shows that a polymer was formed in an empty space between the nonwoven fibers, which was coated using UV, but it can be seen that less coating was applied to the nonwoven fiber strands. On the other hand, it was confirmed that the nonwoven fabric filter coated by plasma polymerization was evenly coated on the fibers of the nonwoven fabric filter, as shown in FIG.

Taken together, it can be seen that more precursors are coated on a surface with a high contact angle than on a surface with a low contact angle, and it can be seen that the coating power is excellent. Accordingly, it is expected that the performance of the filter will be improved by firstly removing foreign substances such as dust by imparting superhydrophobicity to the surface of the filter for air purification.

In the above, the present invention has been exemplarily described, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present specification are not intended to limit the present invention, but to explain the present invention, and the spirit and scope of the present invention are not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technologies within the scope equivalent thereto should be construed as being included in the scope of the present invention.

By using the superhydrophobic coating method according to the present invention, superhydrophobicity can be imparted to the surface through a simple process, and the performance of the filter can be improved by applying it to an air purification filter.

Claims (10)

1) mixing trimethylsilyl methacrylate and methyl methacrylate; 2) injecting the mixture prepared by step 1) into a plasma reactor together with gas and spraying the mixture onto the substrate; And 3) Plasma polymerization coating by plasma treatment in the reactor; Superhydrophobic surface coating method comprising: The method of claim 1, wherein the surface of the substrate has superhydrophobicity after step 3). The method of claim 1, wherein in step 1), trimethylsilyl methacrylate and methyl methacrylate are mixed at a molar ratio of 4:1. The method of claim 1, wherein the plasma treatment time in step 3) is 3 to 6 minutes. The method of claim 1, wherein the plasma is a low-temperature plasma. The method of claim 1, wherein the plasma treatment power is 15 W. The method of claim 1, wherein the gas contains nitrogen gas. The method of claim 1, wherein the substrate is made of glass, metal, nonwoven fabric, acrylic, spandex, polymer, ceramic, paper, plastic, silicone, wool, silk, cotton, flax, jute, wood, nylon, and activated carbon fibers. Superhydrophobic surface coating method, characterized in that any one An air purification filter coated with the coating method according to any one of claims 1 to 8 The filter of claim 9, wherein the surface of the filter is superhydrophobic.

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