Self-cleaning coating and method for its preparation

Abstract

The present application relates to a kind of self-cleaning coating and its preparation method, the preparation method includes the following steps: with basic organic compound as catalyst, the average particle size of 50nm~200nm of silica is carried out ring-opening polymerization with epsilon-caprolactone, and poly-caprolactone modified silica is obtained;The poly-caprolactone modified silica is dispersed in organic solvent, and fluorosilane is added to carry out condensation reaction, and self-cleaning coating is obtained.The self-cleaning coating prepared by the preparation method of the present application can maintain good mechanical strength, structural stability, self-cleaning performance and biodegradability for a long time after being made into coating.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a self-cleaning coating and its preparation method. Background Technology

[0002] Self-cleaning coatings, with their unique properties, can effectively reduce the adhesion of dirt to material surfaces, significantly lower cleaning costs, and substantially extend the service life of materials, making them a research hotspot in the field of materials science. Among them, superhydrophobic self-cleaning coatings are an important type of self-cleaning coating. Their criteria are that the water contact angle of a water droplet on the material surface is greater than 150° and the roll-off angle is less than 10°. Based on this characteristic, water droplets easily roll on the material surface, carrying away contaminants and dust during the rolling process, thereby achieving a self-cleaning function.

[0003] However, traditional superhydrophobic self-cleaning coatings, represented by polysiloxane and nanoparticle composite systems, still have the following problems: (1) Insufficient mechanical strength, which makes them prone to damage when subjected to external forces, resulting in a decline in self-cleaning performance and difficulty in meeting the long-term use requirements in complex environments; (2) Poor structural stability, which makes the material structure prone to change during long-term use, affecting the self-cleaning effect and service life; (3) Difficult to degrade, which will cause secondary pollution to the environment after the self-cleaning coating is discarded. Summary of the Invention

[0004] Therefore, it is necessary to provide a self-cleaning coating and its preparation method to address the above problems. The self-cleaning coating prepared by the method can maintain good mechanical strength, structural stability, self-cleaning performance and biodegradability for a long time after being formed into a coating.

[0005] A method for preparing a self-cleaning coating includes the following steps:

[0006] Using an alkaline organic compound as a catalyst, silica with an average particle size of 50 nm to 200 nm was subjected to a ring-opening polymerization reaction with ε-caprolactone to obtain polycaprolactone-modified silica.

[0007] The polycaprolactone-modified silica was dispersed in an organic solvent, and fluorosilane was added to carry out a condensation reaction to obtain a self-cleaning coating.

[0008] In one embodiment, the fluorosilane has the following structural formula: Where x and y are both positive integers, and 3≤x+y≤9;

[0009] And / or, the organic solvent is an ester compound.

[0010] In one embodiment, y = 3, 4, 5, 6, or 7;

[0011] And / or, the ester compound is selected from at least one of methyl decanoate, ethyl decanoate, or propyl decanoate.

[0012] In one embodiment, the basic organic compound is selected from at least one of triphenylphosphine or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0013] In one embodiment, the mass ratio of the silica to the ε-caprolactone is 1:4 to 1:6;

[0014] And / or, the mass ratio of the silicon dioxide to the alkaline organic compound is 10:1 to 30:1.

[0015] In one embodiment, the mass ratio of the fluorosilane to the silicon dioxide is 0.7:1 to 0.9:1.

[0016] In one embodiment, the ring-opening polymerization reaction is carried out at a temperature of 130°C to 150°C for a time of 0.7 h to 1.5 h.

[0017] In one embodiment, the condensation reaction is carried out at a temperature of 65°C to 135°C for a time of 4.5h to 7.0h.

[0018] In one embodiment, the ring-opening polymerization reaction includes a first stage, a second stage, and a third stage carried out sequentially. The reaction temperature of the first stage is 65°C to 75°C, and the reaction time is 1.5h to 2.0h. The reaction temperature of the second stage is higher than the boiling point of the fluorosilane, and the reaction time is 1.5h to 2.5h. The reaction temperature of the third stage is higher than the boiling point of the organic solvent, and the reaction time is 1.5h to 2.5h.

[0019] A self-cleaning coating prepared using the above-described method for preparing self-cleaning coatings.

[0020] In this invention, polycaprolactone segments are first grafted onto the surface of silica. Then, fluorosilanes are introduced to perform a condensation reaction, capping the end groups of the polycaprolactone segments and preventing their degradation, thereby improving their stability. Simultaneously, the hydroxyl groups on the polycaprolactone-modified silica surface can also undergo grafting reactions with the fluorosilanes, forming a chemically cross-linked network structure. Furthermore, after the self-cleaning coating is formed, during service, the unreacted methoxysilane groups in the fluorosilanes can further react with hydroxyl groups in the environment, continuously improving the cross-linked network and significantly enhancing the coating's mechanical strength and structural stability. In addition, the fluorinated groups introduced by the fluorosilanes have strong hydrophobicity, which, in synergy with silica within a specific particle size range, enables the self-cleaning coating to exhibit superhydrophobic properties, achieving highly efficient self-cleaning. The polycaprolactone segments also endow the self-cleaning coating with good biodegradability.

[0021] In summary, the self-cleaning coating prepared using this invention can maintain good mechanical strength, structural stability, and self-cleaning performance for a long time in complex environments, and can gradually degrade in the natural environment, thereby significantly expanding its application scenarios and extending its service life. Detailed Implementation

[0022] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all the related listed items.

[0024] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0025] This invention provides a method for preparing a self-cleaning coating, comprising the following steps:

[0026] Using an alkaline organic compound as a catalyst, silica with an average particle size of 50 nm to 200 nm was subjected to a ring-opening polymerization reaction with ε-caprolactone to obtain polycaprolactone-modified silica.

[0027] The polycaprolactone-modified silica was dispersed in an organic solvent, and a condensation reaction was carried out with fluorosilane to obtain a self-cleaning coating. The reaction process is as follows:

[0028] .

[0029] In this invention, polycaprolactone segments are first grafted onto the surface of silica, and then fluorosilanes are introduced. A condensation reaction is performed, wherein -OMe is a methoxy group and -R... F The fluorosilane is a fluoroalkyl group, where m, n, and f are all positive integers. During the condensation reaction, the fluorosilane can cap the end groups of the polycaprolactone segments, thereby preventing degradation and improving their stability.

[0030] Meanwhile, the hydroxyl groups on the surface of polycaprolactone-modified silica can also undergo grafting reactions with fluorosilanes to form a chemical cross-linked network structure. After the self-cleaning coating is made into a coating, during service, the unreacted methoxysilane groups in the fluorosilane can further react with hydroxyl groups in the environment to continuously improve the cross-linked network, which significantly enhances the mechanical strength and structural stability of the coating.

[0031] In addition, controlling the silica at any point or range between 50nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm or 200nm can create a sufficient air cushion structure on the surface of the coating, improving hydrophobicity. Combined with the strong hydrophobic fluorinated groups introduced by fluorosilanes, the cleaning coating exhibits superhydrophobic properties, achieving highly efficient self-cleaning. The polycaprolactone segments also endow the self-cleaning coating with good biodegradability.

[0032] In summary, the self-cleaning coating prepared using this invention, once formed into a coating, can maintain good mechanical strength, structural stability, and self-cleaning performance for a long time under complex environments, and can gradually degrade in the natural environment, thereby significantly expanding its application scenarios and extending its service life. Furthermore, the preparation method of this invention does not require complex equipment or harsh process conditions, effectively reducing production costs and making it suitable for large-scale industrial production.

[0033] Optionally, the mass ratio of silica to ε-caprolactone is preferably 1:4 to 1:6, and can be selected as any ratio of 1:4, 1:45, 1:5, 1:55 or 1:6. Within this ratio range, silica can be fully dispersed in ε-caprolactone, promoting the full polymerization of ε-caprolactone on the silica surface, and obtaining polycaprolactone-modified silica with a more thorough grafting degree.

[0034] To promote the effective progress of the polymerization reaction, the mass ratio of the silica to the alkaline organic compound is preferably 10:1 to 30:1, and can be selected from any ratio of 10:1, 15:1, 20:1, 25:1 or 30:1.

[0035] Optionally, the basic organic compound is selected from at least one of triphenylphosphine or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0036] To ensure a more complete ring-opening reaction, the preferred reaction temperature for the ring-opening polymerization is 130℃~150℃, which can be any value among 130℃, 135℃, 140℃, 145℃ or 150℃ or any range between two values; the preferred reaction time is 0.7h~1.5h, which can be any value among 0.7h, 0.9h, 1.1h, 1.3h or 1.5h or any range between two values.

[0037] To improve the purity of polycaprolactone-modified silica, an organic dispersant can be added to the resulting reaction solution after the ring-opening polymerization reaction. The organic dispersant is preferably a dispersant that can dissolve basic organic compounds and ε-caprolactone. Subsequently, the insoluble matter is collected by separation methods such as centrifugation, which yields high-purity polycaprolactone-modified silica.

[0038] Understandably, to avoid the adverse effects of moisture on the ring-opening polymerization reaction, protective gases such as nitrogen or argon can be continuously introduced during the reaction. Furthermore, the silica can be calcined before the ring-opening polymerization reaction. The specific steps are as follows: weigh a measured amount of silica, place it in a nitrogen-protected tube furnace, heat it to a preset calcination temperature, and maintain this temperature for a period of time to effectively remove water molecules adsorbed on its surface.

[0039] Optionally, the preferred structural formula of the fluorosilane is... Where x and y are both positive integers, and 3≤x+y≤9, preferably x=0, 1, or 2, and correspondingly y=3, 4, 5, 6, or 7. When x=0, it is a perfluorinated substitution structure, in which case the fluorine content of the fluorosilane is the highest and the hydrophobicity is optimal. When x=1 or 2, although the fluorine content decreases slightly, the reactivity of the fluorosilane is significantly improved. The overall fluorine content can be increased by grafting more fluorosilane molecules, so that the self-cleaning coating can still achieve the ideal hydrophobic effect. More preferably, y=5, 6, or 7. Within this range, the hydrophobic performance can be better avoided due to insufficient fluorine content, and the condensation reaction activity between fluorosilane and polycaprolactone-modified silica can be reduced due to excessive fluorine content.

[0040] To promote the condensation reaction, an organic solvent with good compatibility with polycaprolactone-modified silica is preferred, for example, an ester compound. To facilitate the removal of unreacted fluorosilanes after the condensation reaction, the boiling point of the ester compound is preferably higher than that of the fluorosilane. The ester compound is selected from at least one of methyl decanoate, ethyl decanoate, or propyl decanoate.

[0041] In order to ensure that the hydroxyl groups on the surface of silica and the hydroxyl groups at the end of polycaprolactone in polycaprolactone-modified silica react fully with fluorosilane and to reduce waste caused by adding excessive fluorosilane, the mass ratio of fluorosilane to silica is preferably 0.7:1 to 0.9:1, and can be selected as any ratio of 0.7:1, 0.8:1 or 0.9:1.

[0042] Optionally, the condensation reaction temperature is preferably 4.5h to 7.0h, selectable from any one of 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, or 7.0h, or any range between two values; the condensation reaction time is preferably 65℃ to 135℃, selectable from any one of 65℃, 75℃, 85℃, 95℃, 105℃, 115℃, 125℃, or 135℃, or any range between two values. Within this reaction temperature and time range, the fluorosilane can undergo a more thorough condensation reaction with polycaprolactone-modified silica, achieving end-capping of polycaprolactone segments, formation of a cross-linked network, and increasing the fluorine content of the self-cleaning coating.

[0043] To simultaneously recover and utilize byproducts and unreacted raw materials during the condensation reaction, the ring-opening polymerization reaction may include multiple stages with sequentially increasing temperatures, such as two, three, or four stages. Preferably, the ring-opening polymerization reaction includes a first stage, a second stage, and a third stage performed sequentially. The first stage is atmospheric distillation, with a preferred reaction temperature of 65°C to 75°C and a preferred reaction time of 1.5 to 2.0 hours. This stage can remove methanol byproducts generated from the methoxy group cleavage of fluorosilanes. The reaction temperature of the second stage is higher than the boiling point of the fluorosilane. For example, the second stage... The first stage is vacuum distillation, with a pressure of 500 Pa to 700 Pa, a preferred reaction temperature of 100°C to 120°C, and a preferred reaction time of 1.5 h to 2.5 h. This stage can remove unreacted fluorosilanes. The third stage is above the boiling point of the organic solvent. For example, the third stage is vacuum distillation, with a pressure of 500 Pa to 700 Pa, a preferred reaction temperature of 125°C to 135°C, and a preferred reaction time of 1.5 h to 2.5 h. This stage can remove most of the organic solvent. The stirring speed for the condensation reaction can be 400 rpm to 600 rpm.

[0044] This invention also provides a self-cleaning coating prepared using the aforementioned method. The self-cleaning coating of this invention, once formed into a coating, exhibits superhydrophobicity. Water forms approximately spherical droplets on its surface with a contact angle greater than or equal to 150°, effectively preventing water from wetting the surface. Simultaneously, the roll-off angle is less than or equal to 10°, allowing the droplets to easily roll and carry away dust, stains, and other impurities during the rolling process, thus achieving a self-cleaning function. During the coating's service life, unreacted methoxysilane groups in the fluorosilane can further react with hydroxyl groups in the environment, continuously improving the cross-linked network structure of the coating and forming a stable framework system. This structure can effectively disperse and withstand external forces, significantly improving the mechanical strength of the coating and making it less susceptible to damage from external forces. This ensures long-term good integrity and self-cleaning performance, meeting the long-term use requirements in complex environments. Furthermore, the coating made from the self-cleaning coating of this invention also has good biodegradability. After the coating's service life ends, it can gradually degrade in the natural environment without causing secondary pollution.

[0045] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0046] Example 1

[0047] Commercially available silica with an average particle size of 100 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0048] Weigh 20g of calcined silica and transfer it to a dry single-necked flask. Under continuous nitrogen protection, add 103g of ε-caprolactone and then ultrasonically disperse at 300W for 1h to form a uniform suspension. Subsequently, add 1.0g of triphenylphosphine catalyst and stir at 800rpm. Heat the reaction system to 150℃ and react at this temperature for 1h. After the reaction is complete, allow the reaction solution to cool naturally to room temperature. Add 100mL of methyl decanoate dispersant to the single-necked flask and then transfer it to a high-speed centrifuge tube. Centrifuge at 15000rpm for 10min, remove the supernatant, and repeat the centrifugation operation three times to obtain polycaprolactone-modified silica.

[0049] 200 mL of methyl decanoate solvent was added to polycaprolactone-modified silica, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Then, 15 g of tridecafluorooctyltrimethoxysilane was added, and the mixture was stirred at 500 rpm while the temperature was slowly raised to 70 °C and held at that temperature for 2 h. Methanol was removed by atmospheric distillation. Then, the temperature was raised to 100 °C and the mixture was distilled under reduced pressure at 600 Pa for 2 h to remove unreacted tridecafluorooctyltrimethoxysilane. Finally, the temperature was raised to 130 °C and the mixture was distilled under reduced pressure at 600 Pa for 2 h to remove most of the methyl decanoate, yielding 82.7 g of self-cleaning coating containing a small amount of solvent.

[0050] Example 2

[0051] The only difference between Example 2 and Example 1 is that commercially available silicon dioxide with an average particle size of 50 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0052] Example 3

[0053] The only difference between Example 3 and Example 1 is that commercially available silicon dioxide with an average particle size of 150 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0054] Example 4

[0055] The only difference between Example 4 and Example 1 is that commercially available silicon dioxide with an average particle size of 200 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0056] Example 5

[0057] The difference between Example 5 and Example 1 is that 20g of calcined silica was weighed and transferred to a dry single-necked flask. Under continuous nitrogen protection, 103g of ε-caprolactone was added, and the mixture was ultrasonically dispersed at 300W for 1h to form a uniform suspension. Then, 1.0g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst was added, and the mixture was stirred at 800rpm. The reaction system was heated to 140℃ and reacted at a constant temperature for 1h. After the reaction was completed, the reaction solution was allowed to cool naturally to room temperature. 100mL of methyl decanoate was added to the single-necked flask, and then transferred to a high-speed centrifuge tube. The mixture was centrifuged at 15000rpm for 10min, and the supernatant was removed. The centrifugation operation was repeated 3 times to obtain polycaprolactone-modified silica.

[0058] Example 6

[0059] The only difference between Example 6 and Example 1 is that methyl decanoate is replaced with ethyl decanoate.

[0060] Example 7

[0061] The difference between Example 7 and Example 1 is that 200 mL of methyl decanoate solvent was added to polycaprolactone-modified silica, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Then, 15 g of perfluorooctyltrimethoxysilane was added, and the mixture was stirred at 500 rpm while the temperature was slowly raised to 70 °C and held at that temperature for 2 h. Methanol was removed by atmospheric distillation. Then, the temperature was raised to 100 °C and vacuum distilled at 600 Pa for 2 h to remove unreacted perfluorooctyltrimethoxysilane. Finally, the temperature was raised to 130 °C and vacuum distilled at 600 Pa for 2 h to remove most of the methyl decanoate, yielding 82.7 g of self-cleaning coating containing a small amount of solvent.

[0062] Example 8

[0063] The difference between Example 8 and Example 1 is that 200 mL of methyl decanoate solvent was added to polycaprolactone-modified silica, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Then, 15 g of perfluorohexyltrimethoxysilane was added and stirred at 500 rpm while the temperature was slowly raised to 70 °C and held at that temperature for 2 h. Methanol was removed by atmospheric distillation. Then, the temperature was raised to 100 °C and vacuum distilled at 600 Pa for 2 h to remove unreacted perfluorohexyltrimethoxysilane. Finally, the temperature was raised to 130 °C and vacuum distilled at 600 Pa for 2 h to remove most of the methyl decanoate, yielding 82.7 g of self-cleaning coating containing a small amount of solvent.

[0064] Comparative Example 1

[0065] The only difference between Comparative Example 1 and Example 1 is that commercially available silicon dioxide with an average particle size of 20 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0066] Comparative Example 2

[0067] The only difference between Comparative Example 2 and Example 1 is that commercially available silicon dioxide with an average particle size of 250 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0068] Comparative Example 3

[0069] Commercially available silica with an average particle size of 100 nm was placed in a tube furnace and heated to 450 °C at a heating rate of 5 °C / min under a nitrogen protective atmosphere, and calcined at a constant temperature for 4 hours.

[0070] Weigh 20g of calcined silica and transfer it to a dry single-necked flask. Under continuous nitrogen protection, add 200mL of methyl decanoate and then ultrasonically disperse at 300W for 1h to form a uniform suspension. Add 50g of polycaprolactone (average molecular weight 1000Da) and 15g of tridecafluorooctyltrimethoxysilane and stir at 500rpm while slowly raising the temperature to 70℃ and holding at that temperature for 2h. Remove methanol by atmospheric distillation. Then raise the temperature to 100℃ and distill under reduced pressure at 600Pa for 2h to remove unreacted tridecafluorooctyltrimethoxysilane. Finally, raise the temperature to 130℃ and distill under reduced pressure at 600Pa for 2h to remove most of the methyl decanoate, yielding 78.5g of self-cleaning coating containing a small amount of solvent.

[0071] Comparative Example 4

[0072] The only difference between Comparative Example 4 and Example 1 is that 200 mL of methyl decanoate solvent was added to polycaprolactone-modified silica, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Then, 15 g of perfluorohexylethyl alcohol was added and stirred at 500 rpm while the temperature was slowly raised to 70 °C and held at that temperature for 2 h. Methanol was removed by atmospheric distillation. Then, the temperature was raised to 100 °C and vacuum distilled at 600 Pa for 2 h to remove unreacted perfluorohexylethyl alcohol. Finally, the temperature was raised to 130 °C and vacuum distilled at 600 Pa for 2 h to remove most of the methyl decanoate, yielding 82.7 g of self-cleaning coating containing a small amount of solvent.

[0073] Comparative Example 5

[0074] The only difference between Comparative Example 5 and Example 1 is that 200 mL of methyl decanoate solvent was added to 20 g of calcined silica, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Then, 15 g of tridecafluorooctyltrimethoxysilane was added, and the mixture was stirred at 500 rpm while the temperature was slowly raised to 70 °C and held at that temperature for 2 h. Methanol was removed by atmospheric distillation. Then, the temperature was raised to 100 °C and vacuum distilled at 600 Pa for 2 h to remove unreacted tridecafluorooctyltrimethoxysilane. Finally, the temperature was raised to 130 °C and vacuum distilled at 600 Pa for 2 h to remove most of the methyl decanoate, yielding fluorosilane-modified silica.

[0075] Fluorosilane-modified silica was transferred to a dry single-necked flask. Under continuous nitrogen protection, 103 g of ε-caprolactone was added, and the mixture was ultrasonically dispersed at 300 W for 1 h to form a uniform suspension. Subsequently, 1.0 g of triphenylphosphine catalyst was added, and the mixture was stirred at 800 rpm. The reaction system was heated to 150 °C and reacted at this temperature for 1 h. After the reaction was completed, the reaction solution was allowed to cool naturally to room temperature. 100 mL of methyl decanoate dispersant was added to the single-necked flask, and then the mixture was transferred to a high-speed centrifuge tube and centrifuged at 15000 rpm for 10 min. The supernatant was removed, and the centrifugation operation was repeated three times to obtain a self-cleaning coating containing a small amount of solvent.

[0076] The self-cleaning coatings containing a small amount of solvent prepared in the above examples and comparative examples were applied to glass using a four-sided coater. After curing at room temperature for 2 hours, they were placed in a vacuum oven and aged at 50°C for 2 days to obtain the coating. The contact angle and sliding angle were tested using water, and the results are shown in Table 1.

[0077] Table 1

[0078]

[0079] The analysis in Table 1 is as follows: As can be seen from Examples 1, 7 and 8, when the fluorosilane satisfies a specific structure, that is, when 5≤x+y≤7 in the fluorosilane and y=5, 6 or 7, the self-cleaning coating prepared has the best superhydrophobic effect and excellent self-cleaning performance.

[0080] The data from Examples 1-4 and Comparative Examples 1-2 show that when the average particle size of the nanomaterial is in the range of 50nm-200nm, the coating has a high water contact angle and a low roll-off angle, indicating that the self-cleaning coating prepared by this invention has excellent self-cleaning performance. This is because when the particle size of silica is too small, the material surface cannot form a sufficient air cushion structure. The air cushion structure can reduce the actual contact area between the droplet and the material surface, thereby increasing the water contact angle. Therefore, when the silica particle size is too small, the air cushion is difficult to form, resulting in a limited increase in the contact angle, which in turn affects the self-cleaning performance. When the silica particle size is too large, the material surface is closer to the micron-level roughness. Although the micron-level roughness can increase the water contact angle of the material itself to a certain extent, it cannot meet the microstructure requirements required for the superhydrophobic effect. Superhydrophobic surfaces usually require micro- and nano-level multi-level roughness structures to achieve the best air cushion formation and droplet roll-off effect. Therefore, when the silica particle size is too large, the superhydrophobic structural conditions cannot be met, and the self-cleaning performance is affected.

[0081] The data from Comparative Examples 3 and 5 show that changing the order of grafted polycaprolactone and fluorosilane results in a poor self-cleaning effect of the prepared self-cleaning coating after it has been coated.

[0082] The self-cleaning coatings prepared in the above examples and comparative examples were made into coatings and subjected to thermo-oxidative aging tests. The test method is as follows: the coatings were placed in a hot air circulating oven at 125°C and heat-treated for 72 hours. The water contact angle and tensile strength were then tested to test the mechanical strength and structural stability of the coatings during long-term high-temperature service. The results are shown in Table 2.

[0083] Table 2

[0084]

[0085] After the self-cleaning coatings prepared in Examples 1, 5, and 6 were made into coatings, their abrasion resistance was tested. The test method was as follows: the coating was placed on 1000-grit sandpaper, and a 100g weight was used to press down on the coating. The coating was pulled at a constant speed of 1cm / s to 2cm / s to move it horizontally for 20cm. Then the coating was rotated 90° and moved horizontally for 20cm again. This was considered one cycle. The water contact angle was tested every 5 cycles to characterize the abrasion resistance of the coating. The test data are shown in Table 3.

[0086] Table 3

[0087]

[0088] As can be seen from the data in Table 3, the water contact angle of the coating can still be maintained above 150° after 160 friction cycles. This indicates that the coating still maintains good self-cleaning performance during the friction process and its hydrophobic self-cleaning ability is not significantly reduced due to friction. In other words, the self-cleaning coating exhibits good wear resistance.

[0089] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a self-cleaning coating, characterized in that, Includes the following steps: Using an alkaline organic compound as a catalyst, silica with an average particle size of 50 nm to 200 nm was subjected to a ring-opening polymerization reaction with ε-caprolactone to obtain polycaprolactone-modified silica. The polycaprolactone-modified silica was dispersed in an organic solvent, and fluorosilane was added to carry out a condensation reaction to obtain a self-cleaning coating. The structural formula of the fluorosilane is as follows: x = 0 or 2, y is a positive integer, and 3 ≤ x + y ≤ 9.

2. The method for preparing the self-cleaning coating according to claim 1, characterized in that, The organic solvent is an ester compound.

3. The method for preparing the self-cleaning coating according to claim 2, characterized in that, y = 3, 4, 5, 6 or 7.

4. The method for preparing the self-cleaning coating according to claim 1, characterized in that, The basic organic compound is selected from at least one of triphenylphosphine or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

5. The method for preparing the self-cleaning coating according to claim 1, characterized in that, The mass ratio of silicon dioxide to ε-caprolactone is 1:4 to 1:

6.

6. The method for preparing the self-cleaning coating according to claim 1, characterized in that, The mass ratio of silicon dioxide to the alkaline organic compound is 10:1 to 30:

1.

7. The method for preparing the self-cleaning coating according to claim 1, characterized in that, The mass ratio of the fluorosilane to the silicon dioxide is 0.7:1 to 0.9:

1.

8. The method for preparing the self-cleaning coating according to any one of claims 1 to 7, characterized in that, The ring-opening polymerization reaction is carried out at a temperature of 130℃~150℃ for a time of 0.7h~1.5h.

9. The method for preparing the self-cleaning coating according to any one of claims 1 to 7, characterized in that, The condensation reaction is carried out at a temperature of 65℃ to 135℃ for a time of 4.5h to 7.0h.

10. The method for preparing the self-cleaning coating according to claim 9, characterized in that, The condensation reaction includes a first stage, a second stage, and a third stage, which are carried out sequentially. The reaction temperature of the first stage is 65℃~75℃ and the reaction time is 1.5h~2.0h. The reaction temperature of the second stage is higher than the boiling point of the fluorosilane and the reaction time is 1.5h~2.5h. The reaction temperature of the third stage is higher than the boiling point of the organic solvent and the reaction time is 1.5h~2.5h.

11. A self-cleaning coating prepared using the method for preparing a self-cleaning coating as described in any one of claims 1 to 10.

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