Transparent fluorine-free self-cleaning protective coating and method for its preparation

Abstract

The application discloses a transparent fluorine-free self-cleaning protective coating and a preparation method thereof. The coating is formed by hydrolytic polycondensation and crosslinking of a single-component organic silicon prepolymer. Copolymerized monomers for preparing the prepolymer include 30-50 parts by weight of alicyclic (methyl) acrylate monomers, 5-20 parts by weight of alkoxysilane-containing olefin monomers, 5-20 parts by weight of organic silicon monomers or prepolymers containing polymerizable double bonds, and 2-10 parts by weight of cage polysilsesquioxane containing polymerizable double bonds. By introducing molecular POSS as inorganic nanomaterials, the application replaces traditional inorganic nanoparticles which are prone to agglomeration. Under the premise of maintaining high light transmittance, the mechanical wear resistance of the coating is improved. Combined with the anti-aging performance of the alicyclic skeleton and the characteristics of the organic silicon segment spontaneously enriching on the surface, the coating can be cured at room temperature to obtain a transparent fluorine-free self-cleaning protective coating, which can provide long-acting fluorine-free hydrophobic and oil-repellent and self-cleaning protection for various electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering and optical material protection technology, specifically relating to a transparent fluorine-free self-cleaning protective coating and its preparation method. Background Technology

[0002] Electronic devices are inevitably exposed to humid and dusty environments during daily use, frequently coming into contact with liquids such as sweat and rainwater, as well as dust contaminants, which continuously threaten the reliability and lifespan of the devices. Liquid intrusion can easily cause short circuits, metal corrosion, and functional failures, while contaminant adhesion can reduce the imaging quality of optical components, interfere with sensor accuracy, and damage the product's appearance. Therefore, providing efficient surface protection for electronic device casings, screens, internal circuits, and optical lenses has become a core technological requirement for improving product durability and quality.

[0003] Currently, protective technologies widely used in consumer electronics still heavily rely on fluorinated chemical coatings. These materials can significantly reduce the surface energy of substrates and form transparent films with both hydrophobic and oleophobic properties through spraying or vapor deposition, providing excellent liquid repellency and antifouling performance. However, fluorinated solutions face serious sustainability challenges, as their environmental residues and bioaccumulation pose potential risks to ecosystems and public health.

[0004] Inspired by the self-cleaning effect of lotus leaves, existing technologies often introduce inorganic nanoparticles (such as silica) to construct rough structures, achieving fluorine-free superhydrophobic protection and providing a new path to replace fluorine-containing coatings. However, according to Rayleigh and Mie scattering theory, good light transmittance requires a surface roughness smaller than the wavelength of light. When the roughness exceeds 100 nm, the light scattering effect is significantly enhanced, and micron-scale rough structures struggle to simultaneously achieve high transparency and superhydrophobic properties, necessitating a balance between optical performance and hydrophobic effectiveness. Furthermore, the insufficient mechanical strength of micro / nano structures severely restricts their commercial application. These structures are inherently fragile and have poor adhesion to the substrate, easily breaking or detaching under external forces such as friction and scratching, leading to rapid failure of the protective function. In addition, many precision optical components and photovoltaic modules are extremely sensitive to heat and cannot withstand the high-temperature baking and curing processes required by traditional coatings. Therefore, a novel protective coating that balances high transmittance, high wear resistance, and gentle curing is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the inherent technical defects of existing fluorine-free protective coatings and provide a transparent fluorine-free self-cleaning protective coating and its preparation method that combines high light transmittance, high wear resistance, and extreme weather resistance, while also being capable of low-temperature curing. This solution not only eliminates the light scattering problem caused by added inorganic nanoparticles from a physical source, but also completely avoids thermal damage to devices caused by high-temperature curing processes.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution: A transparent, fluorine-free, self-cleaning protective coating, wherein the coating is formed by hydrolysis, polycondensation, and crosslinking of an organosilicon prepolymer; The organosilicon prepolymer is a copolymer with alkoxysilane side chains, comprising, by weight parts of the raw materials used to prepare the copolymer: Monomer I: 30-50 parts of alicyclic (meth)acrylate monomers; Monomer II: 5-20 parts of alkoxysilyl-containing alkene monomers; Monomer III: 5-20 parts of organosilicon monomers or prepolymers containing polymerizable double bonds; Monomer IV: 2-10 parts of cage-like polysilsesquioxane POSS containing polymerizable double bonds.

[0007] Furthermore, monomer I is selected from one or more of isobornyl methacrylate, isobornyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tetrahydrofurfuryl methacrylate, adamantyl methacrylate, and adamantyl acrylate.

[0008] Furthermore, the monomer II is selected from one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane.

[0009] Furthermore, the monomer III is selected from one or more of the following: mono-terminated (meth)acryloyloxy-terminated polydimethylsiloxane prepolymer, tris(trimethylsiloxy)silylpropyl methacrylate, methylbis(trimethylsiloxy)silylpropyl methacrylate, triisopropylsilyl methacrylate, 3-[tris(1-methylethoxy)silyl]propyl methacrylate, triethylsilyl methacrylate, tributylsilyl methacrylate, and 2-methyl-2-acrylic acid (1,1-dimethylethyl)dimethylsilyl methacrylate.

[0010] Furthermore, the monomer IV is selected from one or more of the following: acryloyloxypropyl heptaisobutyl cage polysilsesquioxane, methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, acryloyloxypropyl heptacyclopentyl cage polysilsesquioxane, octa(methacryloyloxypropyl) cage polysilsesquioxane, octa(acryloyloxypropyl) cage polysilsesquioxane, and octavinyl cage polysilsesquioxane.

[0011] Furthermore, the raw materials for preparation also include a polymerization solvent and a free radical initiator: The polymerization solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, glycerol, acetone, methyl ethyl ketone, 4-methyl-2-pentanone, diethyl ether, dibutyl ether, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, N,N-dimethylformamide, dimethylformamide, acetonitrile, dimethyl sulfoxide, and tetrahydrofuran, and its amount is 50%-200% of the total weight of the monomers.

[0012] The free radical initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, dilauryl peroxide, tert-butyl hydroperoxide, and ammonium persulfate, and its amount is 0.1% to 5% of the total mass of the monomer.

[0013] This invention also provides a method for preparing the above-mentioned transparent fluorine-free self-cleaning protective coating, comprising the following steps: a) Preparation of organosilicon prepolymer solution: Dissolve the above monomers in the polymerization solvent according to the weight parts, add free radical initiator under inert gas protection, and carry out solution copolymerization reaction at 50℃~90℃ for 4~12 hours. After cooling, organosilicon prepolymer solution containing alkoxysilane side chains is obtained. b) Coating and in-situ crosslinking: The organosilicon prepolymer solution obtained in step a is coated onto the substrate surface and cured for 2 to 24 hours at a temperature of 20℃ to 80℃ and a relative humidity of 30% to 80%. During the curing process, the alkoxysilane in the prepolymer spontaneously undergoes de-alcoholization condensation under the action of ambient moisture to form a dense Si-O-Si inorganic crosslinking network, thereby obtaining a transparent fluorine-free self-cleaning protective coating.

[0014] Furthermore, the coating method described in step b) is spin coating, spray coating, scraping coating, or dip coating.

[0015] Furthermore, the substrate is made of glass, polycarbonate, metal, or ceramic.

[0016] The application of the aforementioned transparent fluorine-free self-cleaning protective coating in the preparation of self-cleaning coatings for photovoltaic panels, electronic device housings, display screens, and optical components.

[0017] Compared with existing technologies, this invention uses organic-inorganic hybrid nanoparticles (POSS) as molecular-level rigid crosslinking nodes embedded in the copolymer network. Because their molecular size (approximately 1.5 nm) is much smaller than the wavelength of visible light, light scattering effects are avoided from a physical structure perspective, thus improving the coating's resistance to wind and sand abrasion while ensuring high optical transmittance.

[0018] Beneficial effects: The coating described in this invention is an organic-inorganic hybrid cross-linked network, which is formed by the spontaneous condensation of a single-component organosilicon prepolymer containing multiple specific functional side chains under room temperature and humid conditions. The system is internally supported by a rigid inorganic core (POSS) and a polymer backbone, and relies on the spontaneous enrichment of flexible organosilicon chains towards the air interface to construct a low surface energy antifouling layer. This fundamentally overcomes the technical bottleneck of traditional protective coatings, which struggle to simultaneously achieve extremely high light transmittance, excellent mechanical abrasion resistance, and a non-destructive curing process.

[0019] Monomer I: Serves as the main framework of the coating, providing the polymer with physical hardness and excellent resistance to UV aging, i.e., resistance to yellowing.

[0020] Monomer II: Serves as a crosslinking and anchoring hub, providing moisture curing sites at room temperature and forming strong siloxane Si-O-Si covalent bonds within the coating network and between the coating and substrate interfaces.

[0021] Monomer III: As a surface functional modifier, it reduces the surface energy of the coating by directional enrichment at the air interface, thereby providing durable hydrophobic, oleophobic and self-cleaning properties.

[0022] Monomer IV: As a molecular-level inorganic reinforcing node, it significantly improves the overall mechanical strength and abrasion resistance of the crosslinked network without sacrificing optical transparency.

[0023] The selection of fluorine-free raw materials avoids the severe sustainability challenges faced by fluorine-containing solutions and prevents the environmental residues and bioaccumulation of fluorine-containing solutions from posing potential risks to ecosystems and public health. Attached Figure Description

[0024] Figure 1 The visible light transmittance curve of the coating prepared in Example 1 of this invention is shown.

[0025] Figure 2 This is a comparison chart showing the application effects of the coating prepared in Example 1 of the present invention in terms of anti-fingerprint, anti-graffiti and self-cleaning. Detailed Implementation

[0026] The present invention will be further illustrated by the following embodiments. These embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope of the present invention.

[0027] Example 1: In a reaction flask equipped with a mechanical stirrer, condenser, and thermometer, 40 g of isobornyl methacrylate, 15 g of 3-(methacryloyloxy)propyltrimethoxysilane, 15 g of mono-(meth)acryloyloxy-terminated polydimethylsiloxane prepolymer, and 5 g of acryloyloxypropylheptaisobutyl cage-type polysilsesquioxane were added sequentially. Then, 75 g of solvent, consisting of ethyl acetate and isopropanol mixed in a 1:1 mass ratio, was added to the reaction flask. Under nitrogen protection and stirring, the system was slowly heated to 75°C, and 0.5 g of azobisisobutyronitrile (AIBN) was added as a free radical initiator. After maintaining the reaction at a constant temperature for 6 hours, heating was stopped, and the mixture was allowed to cool naturally to room temperature. A clear, transparent solution of organosilicon prepolymer containing alkoxysilane side chains was collected.

[0028] Glass was used as a substrate, ultrasonically cleaned with anhydrous ethanol, and then dried. The prepolymer solution prepared above was then uniformly coated onto the glass surface using a spraying method. Subsequently, the coated glass sample was left to stand at room temperature for 12 hours. The alkoxysilanes in the prepolymer spontaneously hydrolyzed and underwent de-alcoholization condensation crosslinking, ultimately forming a transparent, fluorine-free, self-cleaning protective coating on the glass surface, such as... Figure 1 and Figure 2 This embodiment includes a visible light transmittance test curve and a comparison chart of its application effects in anti-fingerprint, anti-graffiti, and self-cleaning properties. Figure 2 The upper image shows the effect of blank glass in preventing fingerprints, graffiti, and self-cleaning. The lower image shows the effect of coated glass in Example 1 in preventing fingerprints, graffiti, and self-cleaning. It can be seen that the coating in this example has a significant effect on preventing fingerprints, graffiti, and self-cleaning compared to blank glass.

[0029] Example 2: In a reaction flask equipped with a mechanical stirrer, condenser, and thermometer, 40 g of isobornyl methacrylate, 15 g of 3-(methacryloyloxy)propyltrimethoxysilane, 15 g of tris(trimethylsiloxy)silylpropyl methacrylate, and 5 g of acryloyloxypropylheptaisobutyl cage-like polysilsesquioxane were added sequentially. Then, 75 g of solvent, a mixture of ethyl acetate and isopropanol in a 1:1 mass ratio, was added to the reaction flask. Under nitrogen protection and with stirring, the system was slowly heated to 75°C, and 0.5 g of azobisisobutyronitrile was added as a free radical initiator. After maintaining the reaction at a constant temperature for 6 hours, heating was stopped, and the mixture was allowed to cool naturally to room temperature. A clear, transparent solution of organosilicon prepolymer containing alkoxysilane side chains was collected.

[0030] Glass was used as a substrate, ultrasonically cleaned with anhydrous ethanol, and then dried. The prepolymer solution prepared above was then uniformly coated onto the glass surface using a spraying method. Subsequently, the coated glass sample was placed at room temperature for 12 hours, ultimately forming a transparent, fluorine-free, self-cleaning protective coating on the glass surface.

[0031] Example 3: In a reaction flask equipped with a mechanical stirrer, condenser, and thermometer, 40 g of isobornyl methacrylate, 15 g of 3-(methacryloyloxy)propyltrimethoxysilane, 15 g of tris(trimethylsiloxy)silylpropyl methacrylate, and 5 g of acryloyloxypropylheptaisobutyl cage-like polysilsesquioxane were added sequentially. Then, 75 g of solvent, a mixture of ethyl acetate and isopropanol in a 1:1 mass ratio, was added to the reaction flask. Under nitrogen protection and with stirring, the system was slowly heated to 75°C, and 0.5 g of azobisisobutyronitrile was added as a free radical initiator. After maintaining the reaction at a constant temperature for 6 hours, heating was stopped, and the mixture was allowed to cool naturally to room temperature. A clear, transparent solution of organosilicon prepolymer containing alkoxysilane side chains was collected.

[0032] Glass was used as a substrate, ultrasonically cleaned with anhydrous ethanol, and then dried. The prepolymer solution prepared above was uniformly coated onto the glass surface using a spraying method. Subsequently, the coated glass sample was placed at room temperature for 6 hours, ultimately forming a transparent, fluorine-free, self-cleaning protective coating on the glass surface.

[0033] Comparative Example 1: This comparative example does not contain POSS, but is blended with silica nanoparticles.

[0034] In a reaction flask equipped with a mechanical stirrer, condenser, and thermometer, 40 g of isobornyl methacrylate, 15 g of 3-(methacryloyloxy)propyltrimethoxysilane, and 15 g of mono-(meth)acryloyloxy-terminated polydimethylsiloxane prepolymer were added sequentially. Then, 75 g of solvent, a mixture of ethyl acetate and isopropanol in a 1:1 mass ratio, was added to the reaction flask. Under nitrogen protection and stirring, the system was slowly heated to 75°C, and 0.5 g of azobisisobutyronitrile (AIBN) was added as a free radical initiator. After maintaining the reaction at a constant temperature for 6 hours, heating was stopped, and the mixture was allowed to cool naturally to room temperature. A clear, transparent solution of organosilicon prepolymer containing alkoxysilane side chains was collected. Subsequently, 5 g of silica nanoparticles (average particle size 20 nm) pretreated with a silane coupling agent were added to the system, and the mixture was ultrasonically dispersed for 1 hour. A physically blended organosilicon dispersion was collected.

[0035] Glass was used as a substrate, and ultrasonically cleaned and dried with anhydrous ethanol. The prepared organosilicon dispersion was then uniformly coated onto the glass surface using a spraying method. Subsequently, the coated glass sample was placed at room temperature for 12 hours, ultimately forming a protective coating containing added nano-silica on the glass surface.

[0036] Comparative Example 2: This comparative example does not contain monomer III.

[0037] In a reaction flask equipped with a mechanical stirrer, condenser, and thermometer, 55 g of isobornyl methacrylate, 15 g of 3-(methacryloyloxy)propyltrimethoxysilane, and 5 g of acryloyloxypropylheptaisobutyl cage-like polysilsesquioxane were added sequentially. Then, 75 g of solvent, a mixture of ethyl acetate and isopropanol in a 1:1 mass ratio, was added to the reaction flask. Under nitrogen protection and with stirring, the system was slowly heated to 75°C, and 0.5 g of azobisisobutyronitrile was added as a free radical initiator. After maintaining the reaction at a constant temperature for 6 hours, heating was stopped, and the mixture was allowed to cool naturally to room temperature. A clear, transparent solution of organosilicon prepolymer containing alkoxysilane side chains was collected.

[0038] Glass was used as a substrate, ultrasonically cleaned with anhydrous ethanol, and then dried. The prepolymer solution prepared above was uniformly coated onto the glass surface using a spraying method. Subsequently, the coated glass sample was placed at room temperature for 12 hours, eventually forming a transparent coating on the glass surface.

[0039] Table 1 Performance test results of the embodiments As can be seen from the test results in the table above, the transparent fluorine-free protective coating prepared by this invention exhibits excellent synergistic effects in terms of optical transparency, anti-fouling and self-cleaning properties, and mechanical wear resistance. The coatings prepared in Examples 1-3 have high initial transmittance, all greater than 90.5%, and at the same time endow the surface with excellent hydrophobic and oleophobic properties, with a water contact angle of up to 115° and a hexadecane contact angle of 72°. Moreover, the transmittance decay after 500 rub tests is minimal, as low as 1.1%.

[0040] The formulation of Example 3 was the same as that of Example 2, but the curing time was shortened from 12 hours to 6 hours. The results showed that the shorter curing time resulted in insufficient cross-linking density of the siloxane network, and its abrasion resistance, i.e., light transmittance, decreased by 3.2%, which was significantly weaker than the 1.3% decrease in Example 2 after full curing.

[0041] Comparative Example 1 used conventional physically blended silica nanoparticles. Due to the aggregation of nanoparticles and Rayleigh scattering effect, its initial transmittance dropped significantly to 86.4%, and its wear resistance was poor (transmittance decreased by 4.6%). In contrast, the POSS introduced in this embodiment of the invention, as a molecular-level inorganic material, eliminates light scattering at its source, achieving a balance between high transmittance and mechanical strength.

[0042] In Comparative Example 2, the low-surface-energy organosilicon prepolymer / monomer containing polymerizable double bonds was removed from the formulation. Test results showed that the water contact angle plummeted to 74°, and the hexadecane contact angle dropped even further to 22°. This demonstrates the role of monomer III in enriching and constructing a low-surface-energy matrix at the air interface.

[0043] The examples described above are merely illustrative, used to explain some features of the methods described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are merely illustrative of selected implementations based on combinations of all possible embodiments. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A transparent, fluorine-free, self-cleaning protective coating, characterized in that, The raw materials prepared include the following parts by weight: Monomer I: 30-50 parts of alicyclic (meth)acrylate monomers; Monomer II: 5-20 parts of alkoxysilyl-containing alkene monomers; Monomer III: 5-20 parts of organosilicon monomers or prepolymers containing polymerizable double bonds; Monomer IV: 2-10 parts of cage-like polysilsesquioxane POSS containing polymerizable double bonds.

2. The transparent fluorine-free self-cleaning protective coating according to claim 1, characterized in that: The monomer I is selected from one or more of isobornyl methacrylate, isobornyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tetrahydrofurfuryl methacrylate, adamantyl methacrylate, and adamantyl acrylate. The monomer II is selected from one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-(methacryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane; The monomer III is selected from one or more of the following: mono-terminated (meth)acryloyloxy-terminated polydimethylsiloxane prepolymer, tris(trimethylsiloxy)silylpropyl methacrylate, methylbis(trimethylsiloxy)silylpropyl methacrylate, triisopropylsilyl methacrylate, 3-[tris(1-methylethoxy)silyl]propyl methacrylate, triethylsilyl methacrylate, tributylsilyl methacrylate, and 2-methyl-2-acrylate (1,1-dimethylethyl)dimethylsilyl methacrylate; The monomer IV is selected from one or more of the following: acryloyloxypropyl heptaisobutyl cage polysilsesquioxane, methacryloyloxypropyl heptaisobutyl cage polysilsesquioxane, acryloyloxypropyl heptacyclopentyl cage polysilsesquioxane, octa(methacryloyloxypropyl) cage polysilsesquioxane, octa(acryloyloxypropyl) cage polysilsesquioxane, and octavinyl cage polysilsesquioxane.

3. The transparent fluorine-free self-cleaning protective coating according to claim 1, characterized in that, The raw materials used in the preparation also include a polymerization solvent and a free radical initiator: The polymerization solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, glycerol, acetone, methyl ethyl ketone, 4-methyl-2-pentanone, diethyl ether, dibutyl ether, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, N,N-dimethylformamide, dimethylformamide, acetonitrile, dimethyl sulfoxide, and tetrahydrofuran, and its amount is 50%-200% of the total weight of the monomers. The free radical initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, dilauryl peroxide, tert-butyl hydroperoxide, and ammonium persulfate, and its amount is 0.1% to 5% of the total weight of the monomer.

4. A method for preparing a transparent, fluorine-free, self-cleaning protective coating as described in any one of claims 1-3, characterized in that, Includes the following steps: a) Preparation of organosilicon prepolymer: Dissolve all monomers in the polymerization solvent according to the weight parts, add free radical initiator under inert gas protection, and carry out solution copolymerization reaction at 50℃~90℃ for 4~12 hours. After cooling, organosilicon prepolymer solution containing alkoxysilane side chains is obtained. b) Coating and in-situ crosslinking: The organosilicon prepolymer solution obtained in step a is coated onto the substrate surface and cured for 2 to 24 hours at a temperature of 20℃ to 80℃ and a relative humidity of 30% to 80%. During the curing process, the alkoxysilane in the prepolymer spontaneously undergoes de-alcoholization condensation under the action of ambient moisture to form a dense Si-O-Si inorganic crosslinking network, thereby obtaining a transparent fluorine-free self-cleaning protective coating.

5. The preparation method according to claim 4, characterized in that, The coating method described in step b) is spin coating, spray coating, scraping coating, or dip coating.

6. The preparation method according to claim 4, characterized in that, The substrate is made of glass, polycarbonate, metal or ceramic.

7. The application of a transparent fluorine-free self-cleaning protective coating as described in any one of claims 1-3 in the preparation of self-cleaning coatings for photovoltaic panels, electronic device housings, display screens, and optical components.

Images