Self-cleaning waterproof coating and preparation method thereof

Abstract

The invention discloses a self-cleaning waterproof coating and a preparation method thereof, and relates to the technical field of waterproof coatings. Wherein the waterproof coating is prepared from organic silicon modified acrylic resin emulsion, a photocatalyst nano composite material, hydrophobic modified silicon dioxide aerogel powder, a nanofiber reinforced material, a dispersing agent, a coalescing agent, a thickening agent, a defoaming agent and deionized water; through the compatibility design of the core-shell structure photocatalyst and the super-hydrophobic silicon dioxide aerogel, multiple self-cleaning of adsorption, degradation and scouring is achieved, the durability and reliability of self-cleaning are remarkably improved, surface modified nanofibers are adopted as a reinforcing material, a three-dimensional network structure is formed in a coating film, and the self-cleaning performance is improved. And the flexibility of the organic silicon modified acrylic resin is synergistically complemented, so that the tensile strength and the deformation resistance of the coating are improved, the brittleness problem of rigid particles is avoided, and the durability of the coating is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waterproof coating, in particular to a self-cleaning waterproof coating and a preparation method thereof. BACKGROUND

[0002] Coating is a continuous film formed by firmly adhering to the surface of the object to be protected or decorated, usually with resin, or oil, or emulsion as the main, adding or not adding pigments, fillers, adding appropriate additives, with organic solvents or water.

[0003] Waterproof coating is a solvent type, water emulsion type or powder type coating made of synthetic polymer, polymer and asphalt, polymer and cement as the main film forming material, adding various additives, modified materials, filling materials, etc.

[0004] The waterproof coating is brushed on the base surface of the building roof, basement, bathroom, bathroom and outer wall which needs waterproof treatment, and can form a continuous, integral and certain thickness waterproof coating layer under normal temperature conditions.

[0005] The self-cleaning function of the existing waterproof coating product depends on a single technology (such as a pure super-hydrophobic surface or a single photocatalytic coating), which is easy to cause performance degradation due to surface pollution or photocatalytic component deactivation, and the traditional waterproof coating is often added with rigid nanoparticles (such as silicon dioxide and titanium dioxide) to increase the brittleness of the coating, which is easy to fail due to substrate cracking, in addition, the traditional waterproof coating also has the problems of easy agglomeration of nano-filler and poor compatibility of organic components and inorganic functional components, therefore, the present application proposes a self-cleaning waterproof coating and a preparation method thereof to solve the problems in the prior art. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a self-cleaning waterproof coating and a preparation method thereof, which solves the problems of easy performance degradation due to surface pollution or photocatalytic component deactivation, easy failure due to substrate cracking, easy agglomeration of nano-filler and poor compatibility of organic components and inorganic functional components in the existing waterproof coating product.

[0007] In order to achieve the purpose of the present application, the present application realizes the following technical scheme: a self-cleaning waterproof coating, comprising the following raw materials by weight: 30-50 parts of silicone modified acrylic resin emulsion, 3-8 parts of photocatalyst nano-composite material, 5-12 parts of hydrophobic modified silica aerogel powder, 2-5 parts of nano-fiber reinforced material, 0.5-1.5 parts of dispersing agent, 1-3 parts of film-forming aid, 0.2-1.0 parts of thickening agent, 0.1-0.5 parts of defoaming agent and 20-35 parts of deionized water.

[0008] The photocatalyst nanocomposite is a core-shell structure, the inner core is nano titanium dioxide, and the outer shell is a porous silica layer.

[0009] The nano titanium dioxide is modified by co-doping of rare earth elements lanthanum and cerium.

[0010] The nanofiber reinforcing material is one of cellulose nanofibers or polyvinyl alcohol nanofibers which are surface modified by silane coupling agent KH-550.

[0011] Further improvement lies in that the film-forming aid is a mixture of dodecanol ester and propylene glycol phenyl ether with a mass ratio of 2:1, the dispersant is a polyacrylic acid sodium salt dispersant, the thickening agent is a hydrophobically modified alkali-swellable thickening agent, and the defoaming agent is an organic silicon-based defoaming agent.

[0012] Further improvement lies in that the specific preparation method of the photocatalyst nanocomposite is as follows: titanium source, lanthanum source and cerium source are mixed in a molar ratio of 100-x-y:x:y, wherein x=0.5-2 and y=0.5-2, deionized water and a surfactant are then added to the mixture, the mixture, deionized water and surfactant are mixed in a mass ratio of 100:300-600:0.5-2, a precursor sol is generated through hydrolysis and polycondensation reaction, a porous silica layer is coated on the surface through a sol-gel method, and a core-shell structure is formed after calcination.

[0013] Further improvement lies in that the specific preparation method of the hydrophobically modified silica aerogel powder is as follows: silica aerogel particles and fluorine-containing silane are mixed in a molar mass ratio of 100:1-5, ultrasonic dispersion is performed in an ethanol-water mixed solvent, and the hydrophobically modified silica aerogel powder is prepared after drying.

[0014] Further improvement lies in that the surface modification method of the nanofiber reinforcing material is as follows: cellulose nanofibers or polyvinyl alcohol nanofibers are dispersed in an ethanol-water mixed solution, silane coupling agent KH-550 is added, ultrasonic dispersion is performed, the temperature is increased to 60-80℃ for stirring, and the nanofiber reinforcing material is prepared after centrifugation and drying.

[0015] A preparation method of a self-cleaning waterproof coating, comprising the following steps:

[0016] Step one: prepare each raw material in advance, add 40%-50% deionized water, a dispersant, 50% defoaming agent into a high-speed disperser under light-proof conditions, and continue to stir and disperse to obtain slurry A after adding hydrophobically modified silica aerogel powder and photocatalyst nanocomposite;

[0017] Step two: add nanofiber reinforcing material into the remaining deionized water, perform ultrasonic treatment first, and then perform mechanical stirring to obtain nanofiber suspension B;

[0018] Step three: add the silicone modified acrylic resin emulsion into the low-speed stirring kettle, slowly add slurry A, film forming aid, thickening agent and the remaining defoaming agent in sequence, continuously stir until mixed evenly, and obtain mixture C;

[0019] Step four: add the nanofiber suspension B into mixture C and stir, adjust the pH to 8.0-9.0 with ammonia water, and then transfer into a sealed container, and mature under light-proof conditions to obtain the final self-cleaning waterproof coating.

[0020] Further improvement lies in that, in step one, the light-proof condition is realized by wrapping the glass reaction kettle with aluminum foil, and the stirring shaft of the high-speed disperser is made of anti-ultraviolet material.

[0021] Further improvement lies in that, in step four, the mixing system is stirred at a low speed every 4 hours during the maturing process, the stirring speed is 100 rpm, and the stirring time is 5 minutes.

[0022] The self-cleaning waterproof coating has the advantages that: by the compatible design of the core-shell structure photocatalyst and the super-hydrophobic silica aerogel, the multiple self-cleaning of adsorption-degradation-flushing is realized: the porous silica shell enhances the pollutant adsorption sites, and the rare earth co-doping broadens the light response range of titanium dioxide, so that the pollutants can be efficiently degraded under visible light; and the super-hydrophobic aerogel surface greatly reduces the probability of liquid pollutant adhesion, the un-adhered pollutants can be washed away by rain, and the adhered pollutants are also decomposed by photocatalysis, so that the durability and reliability of self-cleaning are significantly improved.

[0023] And the surface modified nanofiber is used as the reinforcing material, which forms a three-dimensional network structure in the coating film, and the flexibility of the silicone modified acrylic resin is complementary, so that the tensile strength and deformation resistance of the coating are improved, and the brittleness problem of the rigid particles is avoided, the structure design makes the coating still maintain integrity when the substrate cracks, so that the service life of the waterproof layer is greatly prolonged, especially in the complex environment with large temperature difference and long-term stress.

[0024] In addition, by the synergistic effect of the dispersant and the thickening agent, and by the polarity matching design of the hydrophobic modified aerogel and the silicone resin, the dispersion and agglomeration of the nanoparticles are effectively reduced; at the same time, the light-proof dispersion, low-speed mixing and sealed maturing process are adopted in the preparation process, so that the photocatalyst is prevented from being consumed in advance and the organic components are prevented from volatilizing, and the storage stability of the coating is ensured; in addition, the weather resistance and ultraviolet resistance of the silicone resin are complementary to the three-dimensional network structure of the nanofiber, so that the coating can still maintain good waterproof performance and appearance integrity after long-term exposure to humid and polluted environment, and the comprehensive durability is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1It is a preparation method flowchart of the self-cleaning waterproof coating of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0027] Coating refers to a liquid or powder material that can provide protection, decoration or special functions (such as waterproof, fireproof, conductive, etc.) by forming a continuous film on the surface of an object, and its core components are film-forming substances, functional components and media. The film-forming substances mainly include resins / polymers and cement-based materials, the functional components mainly include pigments, fillers and additives, and the media mainly include water-based coatings and solvent-based coatings. Coatings can be divided into waterproof coatings, fireproof coatings, anticorrosive coatings and permeable crystalline coatings according to their functional types.

[0028] Waterproof coating refers to a functional coating material that forms a continuous waterproof film on the surface of a building to prevent water penetration. It is mainly made of synthetic high molecular polymer, high molecular polymer and asphalt, high molecular polymer and cement as the main film-forming material, and various additives, modified materials and filling materials. The coating is solvent-based, water-based or powder-based, and is applied to the surface of the base layer of the building roof, basement, bathroom, bathroom and outer wall that needs waterproof treatment. It can form a continuous, integral and certain thickness of coating waterproof layer under normal temperature conditions.

[0029] It should be noted that the technical means not described in detail in the embodiments of the present application can be realized by conventional means, which is not the key point of the invention, and will not be described here.

[0030] Embodiment 1

[0031] The present embodiment provides a kind of self-cleaning waterproof coating, including the following weight parts raw materials:

[0032] 30 parts of silicone-modified acrylic resin emulsion, solid content is 45%, and the total weight of siloxane chain segment is 8%;

[0033] 3 parts of photocatalyst nano composite material, adopts core-shell structure, the inner core is nano titanium dioxide (TiO2), the shell is porous silicon dioxide (SiO2) layer, the thickness is 5nm, and the coating rate is greater than 95%, wherein the nano titanium dioxide is modified by co-doping rare earth elements lanthanum (La) and cerium (Ce), the doping molar ratio of La and Ce is all 0.5%, and the molar ratio of La and Ce is 1:1;

[0034] hydrophobically modified silica aerogel powder 5 parts, particle size 5 μm, porosity > 90%, specific surface area 600 m 2 / g, water contact angle > 150°;

[0035] nanofiber reinforcing material 2 parts, cellulose nanofiber or polyvinyl alcohol nanofiber surface modified with silane coupling agent KH-550, diameter 50 nm, length 10 μm;

[0036] dispersant 0.5 parts, sodium polyacrylate dispersant, 2% aqueous solution pH 7;

[0037] film-forming aid 1 part, mixture of dodecanol ester and propylene glycol phenyl ether at a mass ratio of 2:1;

[0038] thickening agent 0.2 parts, hydrophobically modified alkali-swellable thickening agent (HASE), viscosity 5000 mPa·s at 25 °C;

[0039] antifoaming agent 0.1 parts, organosilicon antifoaming agent, active ingredient polyether-modified polydimethylsiloxane, solid content 30%;

[0040] deionized water 20 parts.

[0041] In this embodiment, the preparation method of the photocatalyst nanocomposite includes the following steps:

[0042] The titanium source (tetrabutyl titanate) and the lanthanum source (lanthanum nitrate) and the cerium source (cerium nitrate) are mixed in a molar ratio (100-x-y):x:y (x=0.5, y=0.5, x:y=1:1) to obtain a mixture;

[0043] Deionized water and a surfactant (polyethylene glycol) are added to the mixture, and the mixture, deionized water and surfactant are mixed in a mass ratio of 100:300:0.5, and a precursor sol is generated by hydrolysis and polycondensation reaction;

[0044] A porous silica layer (silicon source is tetraethyl orthosilicate) is coated on the surface of the precursor sol by sol-gel method, and a core-shell structure is formed after calcination (400 °C, 2 h).

[0045] In this embodiment, the preparation method of the hydrophobically modified silica aerogel powder includes the following steps:

[0046] Silica aerogel particles and fluorine-containing silane (1H, 1H, 2H, 2H- perfluorooctyltrimethoxysilane) are mixed in a molar mass ratio (based on SiO2) of 100:1;

[0047] The hydrophobic angle of the obtained nanofiber-reinforced material was greater than 150°, as measured by a contact angle measuring instrument (water droplet volume 5 μL, ambient humidity 40%).

[0048] The hydrophobic angle of the obtained nanofiber-reinforced material was greater than 150°, as measured by a contact angle measuring instrument (water droplet volume 5 μL, ambient humidity 40%).

[0049] In this embodiment, the surface modification method of the nanofiber-reinforced material comprises the following steps:

[0050] The cellulose nanofiber or polyvinyl alcohol nanofiber was dispersed in an ethanol-water mixed solution (volume ratio 7:3), and silane coupling agent KH-550 (mass fraction 0.5%) was added. After ultrasonic dispersion (200 W, 15 min) and heating to 60°C stirring (1000 rpm, 2 h), centrifugation (5000 rpm, 10 min) and drying (50°C, 12 h), the nanofiber-reinforced material was obtained.

[0051] Referring to Figure 1 The present embodiment also provides a preparation method of the self-cleaning waterproof coating, comprising the following steps:

[0052] Step one, pre-dispersion

[0053] Under light shielding conditions (light shielding conditions were achieved by wrapping the glass reaction kettle with aluminum foil, light shielding rate > 99%), deionized water (40% of the total amount), dispersant, and 50% defoaming agent were added into a high-speed disperser (the stirring shaft of the disperser was coated with a polytetrafluoroethylene coating as an ultraviolet-resistant material), and stirred at 500 rpm for 5 min (temperature control: circulating water cooling, material temperature ≤ 40°C). Then, hydrophobically modified silica aerogel powder and photocatalyst nanocomposite were slowly added (addition time 10 min), and the rotation speed was increased to 1500 rpm for 20 min of dispersion to obtain uniform slurry A.

[0054] Step two, nanofiber dispersion

[0055] The nanofiber-reinforced material was added into the remaining deionized water (60% of the total amount), and then subjected to ultrasonic treatment (power 300 W, 15 min) and mechanical stirring at 1000 rpm for 30 min to obtain nanofiber suspension B (solid content 1%);

[0056] Step three, emulsion mixing

[0057] The silicone-modified acrylic resin emulsion was added into a low-speed stirring kettle (stirring paddle diameter to kettle diameter ratio 1:3), and slurry A (addition time 15 min), film-forming aid, thickening agent, and the remaining defoaming agent (addition time 10 min) were slowly added in sequence at a rotation speed of 200 rpm. The stirring was continued for 15 min to obtain mixture C.

[0058] Step four, final mixing and maturation

[0059] The nanofiber suspension B was added into the mixture C prepared in step three at a speed of 300 rpm, stirred for 20 min (scraping the wall every 5 min), the pH was adjusted to 8.0 with ammonia water (25%), and then transferred to a sealed container for maturation at 20℃ in the dark for 24 h. During the maturation process, the mixture was stirred at a low speed (100 rpm) for 5 min every 4 h to prevent the nanofiber from settling. After maturation, the final self-cleaning waterproof coating was obtained.

[0060] Example 2

[0061] The present example provides a self-cleaning waterproof coating, which comprises the following raw materials by weight:

[0062] The silicone-modified acrylic resin emulsion is 50 parts, with a solid content of 50%, and the siloxane segment accounts for 15% of the total weight of the resin;

[0063] The photocatalyst nanocomposite is 8 parts, which adopts a core-shell structure, with a nanometer titanium dioxide (TiO2) core and a porous silica (SiO2) shell with a thickness of 20 nm and a coating rate of more than 95%. The nanometer titanium dioxide is modified by co-doping with rare earth elements lanthanum (La) and cerium (Ce), with a doping molar ratio of 2% for both La and Ce, and a molar ratio of La to Ce of 1:2;

[0064] The hydrophobically modified silica aerogel powder is 12 parts, with a particle size of 25 μm, a porosity of >90%, and a specific surface area of 800 m 2 / g, and a water contact angle of >150°;

[0065] The nanofiber reinforcing material is 5 parts, which is cellulose nanofiber or polyvinyl alcohol nanofiber surface-modified by silane coupling agent KH-550, with a diameter of 200 nm and a length of 50 μm;

[0066] The dispersant is 1.5 parts, which is a polyacrylic acid sodium salt dispersant with a 2% aqueous solution pH of 9;

[0067] The film-forming aid is 3 parts, which is a mixture of dodecanol ester and propylene glycol phenyl ether with a mass ratio of 2:1;

[0068] The thickening agent is 1.0 part, which is a hydrophobically modified alkali-swellable thickening agent (HASE) with a viscosity of 10000 mPa·s at 25℃;

[0069] The defoaming agent is 0.5 parts, which is a silicone-based defoaming agent with an effective ingredient of polyether-modified polydimethylsiloxane and a solid content of 50%;

[0070] The deionized water is 35 parts.

[0071] In this embodiment, the preparation method of the photocatalyst nanocomposite includes the following steps:

[0072] The titanium source (titanium isopropoxide) is mixed with the lanthanum source (lanthanum nitrate) and the cerium source (cerium nitrate) according to the molar ratio (100-x-y):x:y (x=1, y=2, x:y=1:2) to obtain a mixture;

[0073] Deionized water and a surfactant (polyethylene glycol) are added to the mixture, and the mixed mass ratio of the mixture, deionized water and surfactant is 50:300:1, and a precursor sol is generated through hydrolysis and polycondensation reaction;

[0074] A porous silica layer (silicon source is tetraethyl orthosilicate) is coated on the surface of the precursor sol by sol-gel method, and a core-shell structure is formed after calcination (600°C, 4h).

[0075] In this embodiment, the preparation method of the hydrophobically modified silica aerogel powder includes the following steps:

[0076] The silica aerogel particles are mixed with fluorine-containing silane (1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane) according to the molar mass ratio (based on SiO2) 20:1;

[0077] Ultrasonic dispersion (power 300W, time 60min) is carried out in an ethanol-water mixed solvent (ethanol volume fraction 80%), and the product is obtained after drying (80°C, vacuum degree < -0.09MPa).

[0078] The hydrophobic angle is tested by a contact angle measuring instrument (water droplet volume 5μL, environmental humidity 60%) >150°.

[0079] In this embodiment, the surface modification method of the nanofiber reinforced material includes the following steps:

[0080] The cellulose nanofiber or polyvinyl alcohol nanofiber is dispersed in an ethanol-water mixed solution (volume ratio 7:3), and silane coupling agent KH-550 (mass fraction 2%) is added, ultrasonic dispersion (200W, 15min) is carried out, and then the temperature is raised to 80°C for stirring (1000rpm, 2h), and the product is obtained after centrifugation (5000rpm, 10min) and drying (50°C, 12h).

[0081] Referring to Figure 1 , the present embodiment also provides a preparation method of a self-cleaning waterproof coating, including the following steps:

[0082] Step one, pre-dispersion

[0083] Under the light shielding condition (the light shielding condition is realized by wrapping the glass reaction kettle with aluminum foil, the light shielding rate > 99%), the deionized water (50% of the total amount), the dispersing agent, 50% of the defoaming agent are added into a high-speed dispersing machine (the stirring shaft surface of the dispersing machine is coated with a polytetrafluoroethylene coating as an ultraviolet resistant material), and stirred at 800 rpm for 5 min (temperature control: circulating water cooling, material temperature ≤ 40℃), then the hydrophobic modified silica aerogel powder and the photocatalyst nano composite are slowly added (the feeding time is 15 min), the rotating speed is increased to 2000 rpm, and is dispersed for 40 min to obtain a uniform slurry A;

[0084] Step two, nanofiber dispersion

[0085] The nanofiber reinforced material is added into the remaining deionized water (50% of the total amount), is first treated by ultrasonic (power 300 W, 15 min), and then is mechanically stirred at 1200 rpm for 30 min to obtain a nanofiber suspension B (solid content 3%);

[0086] Step three, emulsion mixing

[0087] The silicone modified acrylic resin emulsion is added into a low-speed stirring kettle (the ratio of the stirring paddle diameter to the kettle diameter is 1:3), and the slurry A (the feeding time is 20 min), the film forming aid, the thickening agent and the remaining defoaming agent (the feeding time is 15 min) are slowly added in sequence at a rotating speed of 400 rpm, and the stirring is continuously performed for 15 min to obtain a mixture C;

[0088] Step four, final mixing and aging

[0089] The nanofiber suspension B is added into the mixture C obtained in step three at a rotating speed of 500 rpm, and is stirred for 20 min (the wall is scraped every 5 min during the stirring), ammonia water (28%) is used to adjust the pH to 9.0, then the mixture is transferred into a sealed container, and is aged at 30℃ under the light shielding condition for 24 h, during the aging process, the mixture is subjected to low-speed stirring (100 rpm, 5 min) every 4 h to prevent the nanofiber from settling, and finally the self-cleaning waterproof coating is obtained.

[0090] The performances of the self-cleaning waterproof coatings prepared in example 1 and example 2 of the application all meet the following requirements:

[0091] Super-hydrophobic performance: the static contact angle with water ≥ 155°, and the rolling angle ≤ 5° (test method: GB / T 30447-2013);

[0092] Self-cleaning performance: the visible light (λ ≥ 420 nm) irradiation degradation efficiency of the simulated methyl blue pollutants (concentration 0.1 g / L, solution volume 50 mL) is ≥ 90% within 24 h (test method: the absorbance is measured by an ultraviolet-visible spectrophotometer, and the degradation rate is calculated);

[0093] Mechanical property: elongation at break ≥ 450% according to GB / T 528-2009;

[0094] Tensile strength ≥ 3.5 MPa; tensile strength retention rate (after 1000 cycles) ≥ 80% according to GB / T 16777-2008;

[0095] Aging resistance: after 1000 hours of artificial accelerated aging, the coating film has no powdering, blistering, cracking, the light loss rate is ≤ 10%, and the anti-fouling retention rate (comparing the initial contact angle reduction) is ≥ 85% according to GB / T 9755-2014.

[0096] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A self-cleaning water repellent coating, characterized by, The preparation method comprises the following steps: mixing the following raw materials: 30-50 parts of silicone-modified acrylic resin emulsion, 3-8 parts of photocatalyst nanocomposite, 5-12 parts of hydrophobic modified silica aerogel powder, 2-5 parts of nanofiber reinforced material, 0.5-1.5 parts of dispersant, 1-3 parts of film-forming aid, 0.2-1.0 parts of thickening agent, 0.1-0.5 parts of defoaming agent and 20-35 parts of deionized water. The photocatalyst nanocomposite is of a core-shell structure, wherein the inner core is nanometer titanium dioxide and the outer shell is a porous silica layer. The nanometer titanium dioxide is modified by co-doping of rare earth elements lanthanum and cerium. The nanofiber reinforced material is one of cellulose nanofiber or polyvinyl alcohol nanofiber which is surface-modified by silane coupling agent KH-550.

2. The self-cleaning water repellent coating according to claim 1, wherein: The film-forming aid is a mixture of dodecanol ester and propylene glycol phenyl ether with a mass ratio of 2:1, the dispersant is polyacrylic acid sodium salt dispersant, the thickening agent is hydrophobically modified alkali-swellable thickening agent, and the defoaming agent is silicone-based defoaming agent.

3. The self-cleaning water repellent coating according to claim 1, wherein: The specific preparation method of the photocatalyst nanocomposite is as follows: mixing a titanium source with a lanthanum source and a cerium source according to a molar ratio of 100-x-y:x:y, wherein x=0.5-2 and y=0.5-2, then adding deionized water and a surfactant to the mixture, and mixing the mixture, the deionized water and the surfactant according to a mixing mass ratio of 100:300-600:0.5-2, to generate a precursor sol through hydrolysis and polycondensation reaction, then coating a porous silica layer on the surface through a sol-gel method, and forming a core-shell structure after calcination.

4. The self-cleaning water repellent coating according to claim 1, wherein: The specific preparation method of the hydrophobically modified silica aerogel powder is as follows: mixing silica aerogel particles with fluorine-containing silane according to a molar mass ratio of 100:1-5, ultrasonic dispersion in an ethanol-water mixed solvent, and drying to obtain the hydrophobically modified silica aerogel powder.

5. The self-cleaning water repellent coating according to claim 1, wherein: The surface modification method of the nanofiber reinforced material is as follows: dispersing cellulose nanofiber or polyvinyl alcohol nanofiber in an ethanol-water mixed solution, adding silane coupling agent KH-550, ultrasonic dispersion, heating to 60-80 DEG C and stirring, centrifugation and drying to obtain the nanofiber reinforced material.

6. A method for the preparation of a self-cleaning water repellent coating according to any one of claims 1 to 5, characterized in that, The preparation method comprises the following steps: Step one: preparing each raw material in advance, adding 40-50% of deionized water, a dispersant, 50% of a defoaming agent into a high-speed disperser under light-proof conditions, and stirring, then adding hydrophobically modified silica aerogel powder and photocatalyst nanocomposite, and continuously stirring and dispersing to obtain slurry A; Step two: adding nanofiber reinforced material into the remaining deionized water, first ultrasonic treatment, then mechanical stirring to obtain nanofiber suspension B; Step three: adding silicone-modified acrylic resin emulsion into a low-speed stirring kettle, slowly adding slurry A, film-forming aid, thickening agent and the remaining defoaming agent in sequence, continuously stirring until the mixture is uniformly mixed to obtain mixture C; Step four: adding nanofiber suspension B into mixture C, stirring, adjusting pH to 8.0-9.0 with ammonia water, and then transferring into a sealed container, aging under light-proof conditions to obtain the final self-cleaning waterproof coating.

7. A process for the preparation of a self-cleaning water repellent coating as claimed in claim 6, wherein: In step one, the light-proof condition is realized by a glass reaction kettle wrapped with aluminum foil, and the stirring shaft of the high-speed disperser is made of anti-ultraviolet material.

8. A method of preparing a self-cleaning water repellent coating as claimed in claim 6, wherein: In the fourth step, the mixed system is stirred at a low speed every 4 h during the maturation process, the stirring speed is 100 rpm, and the stirring time is 5 min. In the fourth step, the mixed system is stirred at a low speed every 4 h during the maturation process, the stirring speed is 100 rpm, and the stirring time is 5 min.

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