A method for preparing self-cleaning anti-corrosion water-based coating using microcapsules and its application

Abstract

The invention belongs to the field of self-cleaning water-based coatings, and belongs to a method for preparing a self-cleaning anticorrosive water-based coating using microcapsules. The anticorrosive water-based coating is measured by mass, and the raw materials are composed of: 5-12 parts of microcapsules, 10-20 parts of titanium dioxide, 5-8 parts of calcium carbonate, 10-25 parts of quartz powder, 18-35 parts of silicone resin, 1-3 parts of auxiliary agent, and 12-45 parts of deionized water; wherein the microcapsules have a core-shell structure, and the core is one or both of titanium dioxide or graphene oxide with nanometer size, and the shell material is low-density polyethylene. After the shell material is removed after the coating is cured, these core materials can achieve low surface energy and nanostructure on the coating surface, realize hydrophobicity and self-cleaning performance, and the coating has good dispersion stability. The self-cleaning water-based coating prepared has good self-cleaning property, corrosion resistance and salt spray resistance; in addition, this coating also has the advantages of being non-toxic, free of pollutants, and having a long service life.

Description

Technical Field

[0001] The invention relates to a self-cleaning water-based paint and a preparation method thereof, which is particularly suitable for the anti-corrosion and self-cleaning of industrial equipment and civil buildings. Background Art

[0002] Building exterior cleaning is a crucial part of every urban landscape. Cleaning walls and glass requires the use of large amounts of surfactants, which can also pollute the environment. Consequently, self-cleaning coatings have garnered widespread attention in recent years. If 30% of these buildings, or approximately 3,000 buildings, were to adopt self-cleaning coatings, the resulting annual water savings would be substantial. Looking solely at the architectural self-cleaning coatings market, the economic benefits are enormous.

[0003] The self-cleaning behavior of hydrophobic coatings also imitates the nanostructure of the lotus leaf surface, achieving lower surface energy and higher water contact angle. However, nanofillers are often hydrophobic materials and are difficult to evenly distribute in aqueous solvents and resins. Even if a large amount of dispersants and surfactants are added, dispersion can only be achieved in a short period of time. After standing for a period of time, the nanofillers will agglomerate or even segregate out of the solvent and float on the surface of the coating. For example, in existing self-cleaning water-based coatings such as CN201810527659.0 A long-lasting self-cleaning water-based inorganic nanoceramic coating and its preparation method, and CN201811104595.X A self-cleaning water-based fluorocarbon architectural coating and its preparation method, resin, filler, additive, water and other ingredients are mixed. For example, the hydrophobicity of the resin or the micro-nano structure achieves a hydrophobic effect. However, a large amount of additives or the filler must be modified to ensure its uniform dispersion in the coating.

[0004] To overcome these shortcomings, the present invention discloses a self-cleaning water-based coating based on an organosilicon resin and employing microcapsules as the primary self-cleaning functional material, as well as a preparation method. This functional coating exhibits excellent self-cleaning properties and a long service life, making it widely applicable to various industrial equipment and residential building surfaces. Summary of the Invention

[0005] To address the problems outlined in the prior art, the present invention provides a self-cleaning, anti-corrosion water-based coating for building surfaces and its preparation method. The present invention utilizes a microencapsulation method to encapsulate nanoparticles. The microcapsules exhibit excellent dispersibility in a film-forming substance, thus avoiding the difficulty in dispersing the nanoparticles in the film-forming substance. After the coating is cured, the microcapsule shell is removed using infrared light, exposing the uniformly dispersed nanoparticles with excellent self-cleaning properties. This overcomes the poor dispersibility of conventional nanofillers and avoids the need for large amounts of dispersants. The resulting hydrophobic surface structure is highly stable and exhibits excellent environmental performance. The self-cleaning water-based coating prepared by the present invention exhibits excellent self-cleaning properties, corrosion resistance, and salt spray resistance. Furthermore, the coating is non-toxic, free of pollutants, and has a long service life. Nano-titanium dioxide exhibits excellent hydrophobicity and stability, does not react with other substances in the natural environment, is non-flammable, and is non-oxidizable. It also exhibits photocatalytic activity, degrading harmful substances such as benzene and formaldehyde in indoor environments under sunlight, thereby purifying the air.

[0006] A technical solution adopted by the present invention to solve its technical problem is:

[0007] 5-12 parts of microcapsules, 10-20 parts of titanium dioxide, 5-8 parts of calcium carbonate, 10-25 parts of quartz powder, 18-35 parts of silicone resin, 1-3 parts of additives, and 12-45 parts of deionized water.

[0008] The microcapsules in the self-cleaning water-based coating described herein have a core-shell structure, with the core being one or both of nano-sized titanium dioxide and graphene oxide, and the shell being low-density polyethylene. The microcapsules range in size from 25 to 40 microns. Microcapsules with titanium dioxide and graphene oxide as cores were purchased from Changzhou Kouting Nanomaterials Technology Co., Ltd.

[0009] Nano-titanium dioxide or graphene oxide is used because these core materials are nano-sized. After the coating cures and the shell material is removed, these core materials can achieve low surface energy and nanostructure on the coating surface, achieving hydrophobicity and self-cleaning properties. The shell material is made of low-density polyethylene, which has good dispersibility. After wrapping the core material, it can be evenly dispersed in the resin without affecting the performance of the coating. Because the shell material has a low melting point of around 100°C, it can be decomposed and removed by baking with an infrared lamp after the coating cures. The nano-core material inside is released, giving the coating a nanostructure and reducing surface energy.

[0010] The titanium dioxide in the self-cleaning water-based paint described herein is sized at 3000 mesh, calcium carbonate at 1000-2000 mesh, and quartz powder at 800-1000 mesh. The sizes of the three fillers are arranged in a gradient to improve their dispersion in water and emulsions. The titanium dioxide, calcium carbonate, and quartz powder were purchased from Liyang Industrial (Shanghai) Co., Ltd.

[0011] The silicone resin is polymethyl silicone resin, which has heat resistance, oxidation resistance, good adhesion and stain resistance. The silicone resin was purchased from Zhuhai Huada Haohong Chemical Co., Ltd.

[0012] Among them, the silicone resin uses polymethyl silicone resin because it has organic groups, good molecular symmetry, and the polarities cancel each other out, so that the entire molecule is non-polar, which makes it have very low surface tension after curing and makes the coating have good hydrophobic properties.

[0013] Additives include dispersants, film formers, preservatives, thickeners and leveling agents.

[0014] The preparation process of the self-cleaning water-based paint described in the present invention is as follows: first, a dispersant is added to deionized water, and the mixture is stirred for 10 to 20 minutes at a rotation speed of 800 to 1200 rpm; then, titanium dioxide, calcium carbonate and quartz powder are added, and the mixture is stirred for 30 to 50 minutes, with the rotation speed maintained at 800 to 1200 rpm; microcapsules are added, the mixture is stirred for 10 to 30 minutes, and the rotation speed is reduced to 600 to 800 rpm; organic silicone resin is added, the mixture is stirred for 20 to 40 minutes, and the rotation speed is reduced to 300 to 400 rpm; finally, a film-forming agent, a preservative, a leveling agent and a thickener are added, and the mixture is stirred for 5 to 15 minutes at a rotation speed of 300 to 400 rpm to obtain the self-cleaning water-based paint.

[0015] The invention discloses an application of a self-cleaning water-based paint: the self-cleaning water-based paint is applied to the surface of a substrate and cured. After curing, the shell material of the microcapsule is melted by irradiation with an infrared lamp to expose the core material, thereby giving the paint surface a nanostructure, reducing the surface energy and improving the self-cleaning performance.

[0016] The curing conditions are: curing at room temperature, and the curing time is 4-12 hours.

[0017] The infrared lamp irradiation heating conditions are as follows: the infrared lamp power is 300W, and the infrared lamp is turned on to directly irradiate the cured coating so that the overall temperature of the cured coating reaches 100-115°C (about 8-15 minutes) to remove the shell material of the microcapsule.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The microcapsules and powder of the present invention are distributed in the resin, exhibiting excellent dispersibility. Subsequent heating of the film-forming material after curing decomposes the microcapsule shell material, exposing the core material and enhancing hydrophobicity. After the outer shell material is removed, the inner core material is fixed within the resin, enhancing the stability and environmental friendliness of the hydrophobic surface. The resulting self-cleaning water-based coating has broad application prospects, particularly for exterior antifouling of various civil buildings and chemical equipment. The coating exhibits self-cleaning and anti-corrosion properties, has a long service life, is VOC-free, and is both human-friendly and environmentally friendly. DETAILED DESCRIPTION

[0020] The following is a detailed description of an embodiment of the present invention. This embodiment is based on the technical solution of the present invention and provides a detailed implementation method, but the protection scope of the present invention is not limited to the following embodiment.

[0021] The dispersant was Tween, the film-forming agent was propylene glycol diacetate, the preservative was isothiazolinone, the thickener was hydroxyethyl cellulose, and the leveling agent was polyacrylic acid. All additives were purchased from Shanghai Dinghe Chemical Technology Co., Ltd. In the examples, the acrylic resin was purchased from BASF. Nano-titanium dioxide was purchased from Aladdin, with a 3000 mesh size.

[0022] The core material of the microcapsules is nano-titanium dioxide with a size of 50 nm, and the shell material is low-density polyethylene. They were purchased from Changzhou Kouting Nanomaterials Technology Co., Ltd.

[0023] Example 1:

[0024] 8 grams of dispersant were added to 300 grams of deionized water and stirred at 1000 rpm for 15 minutes. Then, 120 grams of titanium dioxide, 60 grams of calcium carbonate, and 150 grams of quartz powder were added and stirred for another 40 minutes at 1000 rpm. 80 grams of microcapsules were added and stirred for 20 minutes, then the speed was reduced to 700 rpm. 250 grams of silicone resin were added and stirred for 30 minutes, then the speed was reduced to 350 rpm. Finally, 3 grams of film-forming agent, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener were added and stirred for 10 minutes at 350 rpm. The titanium dioxide size was 3000 mesh, the calcium carbonate size was 2000 mesh, the quartz powder size was 1000 mesh, and the microcapsules were 30 microns in size. The coating was applied and cured at room temperature for 12 hours. Afterwards, the microcapsule shell material was removed by heating with an infrared lamp to 110°C for 10 minutes.

[0025] The variables studied are based on the self-cleaning water-based coating in Example 1, with other conditions remaining unchanged. See Table 1 for details.

[0026] Table 1

[0027] Example variable Example a The dosage of microcapsules was changed to 45 grams Example b The dosage of microcapsules was changed to 130 grams Example c Microcapsule size changed to 50 microns Example d Change the microcapsule size to 20 microns Example e Change the size of titanium dioxide, calcium carbonate and quartz powder to 2000 mesh Example f The amount of silicone resin is changed to 160 grams Example g Silicone resin changed to 380 grams Example h Deionized water was changed to 100 g Example 1 Change deionized water to 470 grams

[0028] Comparative Example 1

[0029] Based on the self-cleaning water-based coating of Example 1, microcapsules are not used, but nano-titanium dioxide is directly added, and other conditions remain unchanged.

[0030] Comparative Example 2

[0031] Based on the self-cleaning water-based paint of Example 1, the cured paint film is not irradiated with an infrared lamp, and other conditions remain unchanged.

[0032] Comparative Example 3

[0033] In Example 1, no microcapsules are added to the self-cleaning water-based paint. The microcapsules are finally coated on the surface of the pre-cured paint substrate, and then irradiated with an infrared lamp to remove the shell material.

[0034] If the microcapsules are finally coated on the surface of the cured substrate, it will not have any effect on improving the hydrophobicity of the coating. If the shell material is then removed by infrared light, the core material will be exposed on the surface of the coating and fall off.

[0035] Example 2:

[0036] Add 8 grams of dispersant to 300 grams of deionized water and stir for 15 minutes at 1000 rpm. Then add 120 grams of titanium dioxide, 60 grams of calcium carbonate, and 150 grams of quartz powder and continue stirring for 40 minutes at 1000 rpm. Add 250 grams of silicone resin and stir for 30 minutes, then reduce the speed to 350 rpm. Finally, add 3 grams of film former, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener and stir for 10 minutes at 350 rpm. The titanium dioxide size is 3000 mesh, the calcium carbonate size is 2000 mesh, and the quartz powder size is 1000 mesh.

[0037] Example 3:

[0038] Add 8 grams of dispersant to 300 grams of deionized water and stir for 15 minutes at 1000 rpm. Then add 120 grams of titanium dioxide, 60 grams of calcium carbonate, and 150 grams of quartz powder and continue stirring for 40 minutes at 1000 rpm. Add 80 grams of microcapsules and stir for 20 minutes, then reduce the speed to 700 rpm. Add 250 grams of acrylic resin and stir for 30 minutes, then reduce the speed to 350 rpm. Finally, add 3 grams of film former, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener and stir for 10 minutes at 350 rpm. The titanium dioxide size is 3000 mesh, the calcium carbonate size is 2000 mesh, the quartz powder size is 1000 mesh, and the microcapsules are 30 microns in size. After the coating is cured, heat it with an infrared lamp to remove the microcapsule shell material.

[0039] Example 4:

[0040] 8 grams of dispersant were added to 300 grams of deionized water and stirred at 1000 rpm for 15 minutes. Then, 220 grams of titanium dioxide, 90 grams of calcium carbonate, and 260 grams of quartz powder were added and stirred for 40 minutes at 1000 rpm. 80 grams of microcapsules were added and stirred for 20 minutes, then the speed was reduced to 700 rpm. 250 grams of silicone resin were added and stirred for 30 minutes, then the speed was reduced to 350 rpm. Finally, 3 grams of film former, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener were added and stirred for 10 minutes at 350 rpm. The titanium dioxide size was 3000 mesh, the calcium carbonate size was 2000 mesh, the quartz powder size was 1000 mesh, and the microcapsules were 30 microns in size. After the coating was cured, it was heated with an infrared lamp to remove the microcapsule shell material.

[0041] Example 5:

[0042] 8 grams of dispersant were added to 300 grams of deionized water and stirred at 1000 rpm for 15 minutes. Then, 200 grams of titanium dioxide, 20 grams of calcium carbonate, and 110 grams of quartz powder were added and stirred for 40 minutes at 1000 rpm. 80 grams of microcapsules were added and stirred for 20 minutes, then the speed was reduced to 700 rpm. 250 grams of silicone resin were added and stirred for 30 minutes, then the speed was reduced to 350 rpm. Finally, 3 grams of film former, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener were added and stirred for 10 minutes at 350 rpm. The titanium dioxide size was 3000 mesh, the calcium carbonate size was 2000 mesh, the quartz powder size was 1000 mesh, and the microcapsules were 30 microns in size. After the coating was cured, it was heated with an infrared lamp to remove the microcapsule shell material.

[0043] Example 6:

[0044] 8 grams of dispersant were added to 300 grams of deionized water and stirred at 1000 rpm for 15 minutes. Then, 60 grams of titanium dioxide, 90 grams of calcium carbonate, and 180 grams of quartz powder were added and stirred for another 40 minutes at 1000 rpm. 80 grams of microcapsules were added and stirred for 20 minutes, then the speed was reduced to 700 rpm. 250 grams of silicone resin were added and stirred for 30 minutes, then the speed was reduced to 350 rpm. Finally, 3 grams of film former, 3 grams of preservative, 3 grams of leveling agent, and 3 grams of thickener were added and stirred for 10 minutes at 350 rpm. The titanium dioxide size was 3000 mesh, the calcium carbonate size was 2000 mesh, the quartz powder size was 1000 mesh, and the microcapsules were 30 microns in size. After the coating was cured, it was heated with an infrared lamp to remove the microcapsule shell material.

[0045] Table 1 Contact angle, adhesion and dispersibility of various fillers in the self-cleaning water-based coating samples prepared in each embodiment and comparative example (5 samples were prepared for each sample and the average value was taken). The contact angle test standard is: GB / T31815, the adhesion test standard is: GB / T 9286-1998, and the filler dispersibility test standard is: GB 9755-2014 coating workability standard. The state in the container was observed (no hard lumps, and a uniform state after stirring).

[0046] Table 1

[0047] sample contact angle Adhesion Filler dispersion Example 1 152° Level 0 very good Example a 107° Level 0 very good Example b 154° Level 1 very good Example c 135° Level 0 Poor Example d 140° Level 0 Poor, with a small amount of agglomeration Example e 122° Level 1 Poor, with a small amount of agglomeration Example f 139° Level 2 very good Example g 151° Level 0 very good Example h 106° Level 0 Poor, with a lot of clumping Example 1 119° Level 1 very good Comparative Example 1 --- --- Filler floats on the surface of the resin Comparative Example 2 121° Level 0 very good

[0048] As shown in the table above, when the microcapsule dosage is too low, the contact angle of the paint film decreases, and the self-cleaning performance declines. However, when the microcapsule dosage is too high, the contact angle cannot be further improved, indicating that there is an optimal microcapsule dosage to achieve a synergistic effect for the maximum contact angle. Microcapsule size also significantly affects the adhesion of the paint film and the dispersion of the filler. Excessive size affects the uniformity of the nanocore material, while too small a size causes microcapsules to agglomerate. Variations in the size of the three fillers also affect their dispersion in water and resin, causing agglomeration. Decreasing the amount of silicone resin decreases both the adhesion and hydrophobicity of the paint film. Excessive silicone resin dosage does not significantly change the contact angle of the paint film, indicating that the hydrophobicity of the silicone resin has reached its optimal value and that adding more resin cannot further improve it. This also suggests that there is a synergistic effect between the hydrophobicity of the nanocore material in the microcapsules and the hydrophobicity of the silicone resin, and that only by adding the appropriate amount can the synergistic effect on self-cleaning performance be achieved. Reducing the amount of deionized water significantly reduces filler dispersibility, while increasing the amount reduces film adhesion and weakens the coating's self-cleaning properties. Furthermore, if fillers like nano-titanium dioxide are added directly, they fail to blend with the resin and water, floating on the liquid surface and failing to bond. Finally, if the microcapsule shell material is not removed using infrared heating, the coating's hydrophobicity is compromised, reducing the contact angle.

[0049] Table 2 Contact angle, adhesion, and dispersibility of various fillers in the self-cleaning water-based coating samples prepared in each example (five samples were prepared for each sample and the average value was taken). The contact angle test standard is GB / T 31815, the adhesion test standard is GB / T 9286-1998, and the filler dispersibility test standard is GB 9755-2014, which is the coating workability standard. The state in the container was observed (no lumps, and a uniform state after stirring).

[0050] Table 2

[0051] sample contact angle Adhesion Filler dispersion Color covering power Example 1 152° Level 0 very good very good Example 2 97° Level 0 very good very good Example 3 116° Level 0 Poor very good Example 4 127° Level 0 Poor, with a small amount of agglomeration very good Example 5 150° Level 0 very good very good Example 6 149° Level 0 very good Poor

[0052] As can be seen from the table above, without the addition of microcapsules, the hydrophobicity and self-cleaning properties of the paint film decrease significantly, indicating that the self-cleaning properties of the sample mainly come from the nanofillers in the microcapsules. Replacing the silicone resin with other resins also significantly reduces the self-cleaning properties, again demonstrating that the good hydrophobicity and self-cleaning properties are a synergistic effect of the two. Increasing the filler addition will affect the filler's dispersibility while also reducing the contact angle. Furthermore, increasing the titanium dioxide addition while keeping the total filler content constant has no significant effect on the contact angle, adhesion, and dispersibility of the paint film, but it does increase the cost. Replacing part of the titanium dioxide with two other less expensive fillers will reduce the hiding power of the paint film, hindering the application of the paint.

[0053] With the above-described preferred embodiments of the present invention as inspiration, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing a self-cleaning anti-corrosion water-based coating using microcapsules, characterized in that: The coating ingredients include, by weight: 5-12 parts of microcapsules, 10-20 parts of titanium dioxide, 5-8 parts of calcium carbonate, 10-25 parts of quartz powder, 18-35 parts of silicone resin, 1-3 parts of additives, and 12-45 parts of deionized water; wherein the microcapsules have a core-shell structure, the core is one or both of nano-sized titanium dioxide or graphene oxide, and the shell material is low-density polyethylene; the above ingredients are mixed to prepare a self-cleaning and anti-corrosion water-based coating; the microcapsule size is 25-40 microns; the titanium dioxide size is 3000 mesh, the calcium carbonate size is 1000-2000 mesh, and the quartz powder size is 800-1000 mesh.

2. The method for preparing a self-cleaning anti-corrosion water-based coating using microcapsules according to claim 1, characterized in that: The organic silicone resin is polymethyl silicone resin; the auxiliary agent includes one or more of a dispersant, a film-forming agent, a preservative, a thickener and a leveling agent.

3. The method for preparing a self-cleaning anti-corrosion water-based coating using microcapsules according to claim 2, characterized in that: The preparation process of the coating is as follows: first, a dispersant is added to deionized water and stirred for 10 to 20 minutes at a speed of 800 to 1200 rpm; then titanium dioxide, calcium carbonate and quartz powder are added and stirred for 30 to 50 minutes at a speed of 800 to 1200 rpm; microcapsules are added and stirred for 10 to 30 minutes, the speed is reduced to 600 to 800 rpm; silicone resin is added and stirred for 20 to 40 minutes, the speed is reduced to 300 to 400 rpm; finally, a film-forming agent, a preservative, a leveling agent and a thickener are added and stirred for 5 to 15 minutes at a speed of 300 to 400 rpm to obtain a self-cleaning anti-corrosion water-based coating.

4. The application method of the self-cleaning anti-corrosion water-based coating prepared by the method according to any one of claims 1 to 3, characterized in that: The prepared self-cleaning anti-corrosion water-based coating is coated on the surface of the substrate for curing. After curing, it is irradiated and heated by infrared lamp to obtain a self-cleaning anti-corrosion coating; curing refers to curing at room temperature; infrared lamp irradiation and heating refers to heating to 100-115°C.