A high-hardness transparent anti-fog coating and a method for preparing the same

Abstract

The application discloses a high-hardness transparent anti-fog coating and a preparation method thereof. The coating is prepared by the following steps: firstly, (3-mercaptopropyl) trimethoxysilane and aminopropyl triethoxysilane are used to carry out hydrolysis and condensation reactions under water phase conditions, a silicon-oxygen network structure is formed in situ, and an organic silicon precursor is formed; and then the obtained organic silicon precursor is compounded with a water-based epoxy resin, a coating containing an organic-inorganic hybrid structure is constructed through cooperation with an epoxy resin network, the obtained coating is coated on a substrate surface, and a high-hardness transparent anti-fog coating can be formed after heat curing. The preparation method is simple, raw materials are easy to obtain, and the system is stable. The obtained coating has good optical transparency, excellent mechanical properties and stable anti-fog performance, and has good adhesion and durability, so that the coating has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of functional coating materials technology, specifically relating to a high-hardness transparent anti-fog coating based on waterborne epoxy resin and organosilicon precursor, and its preparation method. Background Technology

[0002] Transparent functional coatings have significant applications in optical lenses, protective glass, display devices, and transparent architectural components. However, in practical use, water vapor condensation easily occurs on the surface of transparent coatings under temperature differences or high humidity environments. If the condensate adheres to the coating surface in the form of numerous tiny droplets, it will cause significant light scattering, leading to surface fogging, reduced light transmittance, and blurred vision, thus severely affecting the performance of transparent materials. Therefore, developing transparent functional coatings that combine excellent mechanical properties with good anti-fogging performance has become an important research direction in the field of surface functional materials.

[0003] Currently, transparent anti-fog coatings are mostly constructed using hydrophilic polymers, zwitterionic polymers, or inorganic nanomaterials, such as polyvinyl alcohol, polyethylene glycol, and silica. These materials can promote the spread of condensate into a uniform water film by increasing surface hydrophilicity, thereby reducing light scattering and achieving an anti-fog effect. However, existing technologies often suffer from insufficient mechanical strength, poor wear resistance, low water resistance, and poor long-term stability. To improve the mechanical properties of the coating, researchers often introduce inorganic nanoparticles for reinforcement. However, inorganic particles are prone to agglomeration in polymer systems, forming light scattering centers and reducing material transparency. Furthermore, insufficient interfacial compatibility between the inorganic and organic phases also affects the stability and overall performance of the coating. Summary of the Invention

[0004] The purpose of this invention is to provide an organic-inorganic hybrid coating that is simple to prepare, has high transparency, excellent mechanical properties, and stable anti-fogging performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A high-hardness transparent anti-fog coating is prepared by first hydrolyzing and condensing (3-mercaptopropyl)trimethoxysilane and aminopropyltriethoxysilane in an aqueous phase to form a silicon-oxygen network structure in situ and constitute an organosilicon precursor. The obtained organosilicon precursor is then compounded with an aqueous epoxy resin. Through synergy with the epoxy resin network, a coating containing an organic-inorganic hybrid structure is constructed. The obtained coating is further cured by heating to obtain the high-hardness transparent anti-fog coating.

[0006] This invention utilizes two functional silanes to achieve controlled hydrolysis-co-condensation in a pure aqueous phase, forming a highly uniform, molecularly dispersed silicon-oxygen network. This network avoids the agglomeration and phase separation problems common in traditional inorganic nanoparticle-reinforced systems, and can form interpenetrating or chemically cross-linked structures with waterborne epoxy resin networks. Simultaneously, the rigid framework of the silicon-oxygen network significantly improves the coating's hardness and mechanical stability, while the residual amino and thiol-based hydrophilic functional groups endow the coating with durable surface hydrophilicity (water contact angle as low as 9°~12°), allowing condensate to quickly spread into a continuous and uniform water film, thereby achieving a long-term stable anti-fogging effect.

[0007] The preparation method of the high-hardness transparent anti-fog coating specifically includes the following steps: (1) Mix aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane in water, add acetic acid to adjust the pH, and then stir the reaction so that the two react with water to generate silanol groups. After standing and condensing, an organosilicon precursor is formed, thereby obtaining an organosilicon precursor solution. (2) Mix the waterborne epoxy resin, triethylenetetramine and the organosilicon precursor liquid obtained in step (1) evenly, and add water to dilute to obtain the coating. (3) Apply the coating obtained in step (2) to the surface of a clean substrate and heat it to cure, thereby obtaining the high-hardness transparent anti-fog coating.

[0008] Furthermore, the molar ratio of aminopropyltriethoxysilane to (3-mercaptopropyl)trimethoxysilane used in step (1) is 10:1.

[0009] Furthermore, in step (1), acetic acid is added to adjust the pH to 7-9.

[0010] Furthermore, the stirring reaction time in step (1) is 30 min.

[0011] Furthermore, the static shrinkage time described in step (1) is 24 hours.

[0012] Furthermore, the volume concentration of the organosilicon precursor solution obtained in step (1) is 60-65%.

[0013] Furthermore, in step (2), the mass ratio of water-based epoxy resin to triethylenetetramine is 1:1.

[0014] Furthermore, in step (2), the amount of silicone precursor liquid added is 3% to 15% of the mass of the waterborne epoxy resin.

[0015] Furthermore, in step (2), the amount of water added is 10% to 90% of the mass of the waterborne epoxy resin.

[0016] Furthermore, the coating method in step (3) can be spin coating, drop coating or dip coating.

[0017] Furthermore, in step (3), the coating amount on the substrate surface is 0.02~0.10 mL / cm². 2 .

[0018] Furthermore, the heating and curing temperature in step (3) is 130°C and the time is 180 min.

[0019] This invention introduces an organosilicon precursor into an aqueous epoxy resin system and induces the hydrolysis and condensation of silane molecules in the aqueous phase to form a Si-O-Si inorganic network structure. This network, in turn, synergistically constructs an organic-inorganic hybrid structure with the epoxy resin network. This structure allows the inorganic silicon-oxygen units to be uniformly distributed at the molecular scale within the polymer matrix, thus avoiding the particle agglomeration problem that occurs in traditional inorganic nanoparticle-reinforced systems. Simultaneously, the silicon-oxygen network structure exhibits high rigidity and stability, significantly improving the hardness and wear resistance of the coating. Furthermore, this invention does not incorporate organic solvents such as ethanol, methanol, or isopropanol, achieving a relatively stable precursor solution state in a pure water system. This avoids the significant condensation and agglomeration problems that easily occur in alcohol-containing systems, facilitating subsequent lamination and film formation.

[0020] The present invention has the following advantages: (1) The present invention constructs an organic-inorganic network structure by in-situ hybridization strategy of organosilicon precursor, which avoids the light scattering problem caused by the aggregation of inorganic nanoparticles and achieves uniform dispersion at the molecular level, thereby significantly improving hardness while maintaining extremely high optical transparency (relative transmittance close to or exceeding that of bare glass).

[0021] (2) The coating obtained by the present invention has high transparency and low haze (as low as 0.31), and its contained silicon-oxygen network structure can significantly improve the hardness and mechanical stability of the coating. In addition, the coating surface has good hydrophilicity, which can achieve stable and long-lasting anti-fogging performance, and can still maintain clear transparency even in a hot water steam environment for a long time.

[0022] (3) The present invention uses pure water as the only solvent, completely avoiding the use of volatile organic solvents such as ethanol, methanol, and isopropanol, which conforms to the principles of green chemistry, reduces environmental pollution and production safety risks, and the preparation process is energy-saving and environmentally friendly, and is easy to scale up.

[0023] (4) Through the synergistic effect of organic-inorganic networks, the coating obtained by the present invention has excellent adhesion (0 grade in cross-cut test), water resistance and durability, as well as mechanical strength. It solves the dual problems of traditional hydrophilic anti-fog coatings being "soft and easy to wear" and inorganic reinforced coatings being "brittle and easy to scatter". It has a longer service life and a wider range of applications (such as optical lenses, automotive glass, building curtain walls, etc.). Attached Figure Description

[0024] Figure 1 Photographs of the appearance of organosilicon precursor solutions prepared by (3-mercaptopropyl)trimethoxysilane and aminopropyltriethoxysilane in different molar ratios (from left to right: 1:10, 1:5, 1:1, 5:1, 10:1).

[0025] Figure 2 This is a comparison chart of the UV-Vis transmittance of the coatings obtained in Example 2 and the comparative example.

[0026] Figure 3 The image shows the anti-fog performance test results of the coating obtained in Example 2.

[0027] Figure 4 The images show the tape adhesion test results of the coating obtained in Example 2. In the images, a is the cross-cut area image before tape peeling, and b is the cross-cut area image after tape peeling. Detailed Implementation

[0028] A high-hardness transparent anti-fog coating is prepared by the following steps: (1) Mix aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane in water at a molar ratio of 1:10 to 10:1, and add acetic acid to adjust the pH to 7 to 9. Then stir the reaction for 30 min, and let it stand for condensation for 24 h to obtain an organosilicon precursor solution with a volume concentration of 60 to 65%. (2) Mix waterborne epoxy resin and triethylenetetramine at a mass ratio of 1:1, and add 3% to 15% of the mass of waterborne epoxy resin in organosilicon precursor liquid and 10% to 90% of water, and mix evenly to obtain a coating. (3) Apply the coating obtained in step (2) at a concentration of 0.02~0.10 mL / cm 2 The coating is applied to a clean substrate surface, then heated to 130°C and cured for 180 minutes to obtain a high-hardness transparent anti-fog coating.

[0029] (3-Mercaptopropyl)trimethoxysilane and aminopropyltriethoxysilane were added to pure water at molar ratios of 1:10, 1:5, 1:1, 5:1, and 10:1, respectively, for hydrolysis and co-condensation. The appearance of the resulting organosilicon precursor solutions was observed, and the results are shown in the figure. Figure 1 .like Figure 1As shown, when the molar ratio of (3-mercaptopropyl)trimethoxysilane to aminopropyltriethoxysilane is 1:10, the resulting silicone precursor solution exhibits a relatively homogeneous overall state, meeting the requirements for subsequent composite with an aqueous epoxy resin / triethylenetetramine system to prepare a coating. However, with further increases in the proportion of mercaptosilane, the resulting precursor solution gradually exhibits significant agglomeration, condensation, and precipitation phenomena, indicating that the combination ratio of the two functional silanes has a significant impact on the stability of the precursor solution. When the proportion of mercaptosilane is high, the precursor solution is difficult to maintain a homogeneous and stable state, which is detrimental to the preparation of subsequent coatings. Therefore, a molar ratio of (3-mercaptopropyl)trimethoxysilane to aminopropyltriethoxysilane of 1:10 is the most suitable ratio for preparing organosilicon precursor solutions.

[0030] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0031] The manufacturers and specifications of some of the raw materials used in this embodiment are as follows: Waterborne epoxy resin: Black Horse brand, solid content 50 wt%; Triethylenetetramine: Dark Horse brand, solid content 40 wt%; Aminopropyltriethoxysilane: purchased from Maclean's, purity 97%; (3-Mercaptopropyl)trimethoxysilane: purchased from Maclean's, purity 97%; Acetic acid (glacial acetic acid): purchased from Shanghai Testing Center, purity 99%; Deionized water: homemade in the laboratory. Example 1

[0032] (1) Weigh out aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane at a molar ratio of 10:1. Then, add aminopropyltriethoxysilane to water and stir for 10 min. At this time, the solution changes from turbid to clear. Then add (3-mercaptopropyl)trimethoxysilane and add acetic acid to adjust the pH to 8. Stir the reaction for 30 min and let it stand for 24 h to obtain an organosilicon precursor solution with a volume concentration of 62.1%. (2) Mix waterborne epoxy resin and triethylenetetramine at a mass ratio of 1:1, and add 3% of the mass of waterborne epoxy resin organosilicon precursor liquid and 70% of water, mix evenly to obtain coating. (3) Apply the coating obtained in step (2) at a concentration of 0.0625 mL / cm 2 The coating is applied to a clean glass surface, then heated to 130°C and cured for 180 minutes to obtain a transparent anti-fog coating (SAS3WEP) with a thickness of approximately 5 μm. Example 2

[0033] (1) Weigh out aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane at a molar ratio of 10:1. Then, add aminopropyltriethoxysilane to water and stir for 10 min. At this time, the solution changes from turbid to clear. Then add (3-mercaptopropyl)trimethoxysilane and add acetic acid to adjust the pH to 8. Stir the reaction for 30 min and let it stand for 24 h to obtain an organosilicon precursor solution with a volume concentration of 62.1%. (2) Mix waterborne epoxy resin and triethylenetetramine at a mass ratio of 1:1, and add 7% of the waterborne epoxy resin by mass of organosilicon precursor liquid and 70% of water, and mix evenly to obtain a coating. (3) Apply the coating obtained in step (2) at a concentration of 0.0625 mL / cm 2 The coating is applied to a clean glass surface, then heated to 130°C and cured for 180 minutes to obtain a transparent anti-fog coating (SAS7WEP) with a thickness of approximately 5 μm. Example 3

[0034] (1) Weigh out aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane at a molar ratio of 10:1. Then, add aminopropyltriethoxysilane to water and stir for 10 min. At this time, the solution changes from turbid to clear. Then add (3-mercaptopropyl)trimethoxysilane and add acetic acid to adjust the pH to 8. Stir the reaction for 30 min and let it stand for 24 h to obtain an organosilicon precursor solution with a volume concentration of 62.1%. (2) Mix waterborne epoxy resin and triethylenetetramine at a mass ratio of 1:1, and add 11% of the mass of waterborne epoxy resin in organosilicon precursor liquid and 70% of water, and mix evenly to obtain a coating. (3) Apply the coating obtained in step (2) at a concentration of 0.0625 mL / cm 2 The coating is applied to a clean glass surface, then heated to 130°C and cured for 180 minutes to obtain a transparent anti-fog coating (SAS11WEP) with a thickness of approximately 5 μm.

[0035] Comparative Example (1) Mix waterborne epoxy resin and triethylenetetramine at a mass ratio of 1:1, and add water equal to 70% of the mass of waterborne epoxy resin. Mix evenly to obtain a coating. (2) Apply the coating obtained in step (1) to a clean glass surface at a coating amount of 0.02~0.10 mL / cm2, heat to 80~150℃ and cure for 10~120 min to obtain a pure water-based epoxy coating (WEP).

[0036] Apply the coating obtained in step (1) at a concentration of 0.0625 mL / cm. 2The coating is applied to a clean glass surface, then heated to 130°C and cured for 180 minutes to obtain a pure water-based epoxy coating (WEP) with a thickness of approximately 5 μm.

[0037] The coatings prepared in the examples and comparative examples were subjected to performance tests as follows, and the results are shown in Table 1: 1. Water contact angle test: The contact angle of the coating with water droplets is determined using a contact angle measuring instrument and its supporting software.

[0038] 2. Hardness test: The pencil hardness of each coating is tested according to the ASTM D3363 standard to evaluate the scratch resistance of the coating surface.

[0039] 3. Transmittance test: The transmittance of different samples was measured using a UV-Vis spectrophotometer.

[0040] 4. Haze test: Using a haze meter (China TH-110), the haze was measured at three different points on the sample surface, and the average value was taken.

[0041] Table 1. Performance test results of Examples 1-3 and the comparative examples.

[0042] As shown in Table 1, compared with the comparative example, the coating obtained in the example has higher pencil hardness and relative transmittance, lower water contact angle and haze. When the amount of silicone precursor liquid added is 7 wt% of the mass of waterborne epoxy resin, the resulting coating can obtain good hydrophilicity and optimal surface hardness, scratch resistance and optical properties.

[0043] The transmittance variation of the coating in the wavelength range of 300–800 nm was measured using a UV-Vis spectrophotometer to evaluate the optical transparency of the coating. The results are shown in [Figure number missing]. Figure 2 .like Figure 2 As shown, the coating obtained in Example 2 maintains a high transmittance in the visible light range, which is significantly higher than that of the comparative example and close to that of bare glass. This further proves that the in-situ hybridization strategy of the organosilicon precursor used in this invention can maintain its excellent transparency while improving the coating performance.

[0044] A glass sample, half coated with the coating obtained in Example 2 and the other half uncoated, was placed above a 100 °C hot water steam environment (the distance between the sample and the hot water surface was 3 cm). The fogging and changes in transparency of the sample surface over time were observed to evaluate the anti-fogging performance of the coating. The results are shown in [Figure Number]. Figure 3 .like Figure 3 As shown, after being placed in a hot water steam environment for 120 seconds, the coated glass sample still maintained good transparency, proving that the coating has excellent anti-fog performance.

[0045] The adhesion of the coating was tested using the cross-cut test according to ASTM D3359 standard. This involved using a cross-cutting tool with 1 mm spacing to create a grid pattern on the coating surface. After removing debris, adhesive tape was applied to the gridded areas and pressed firmly. The tape was then quickly removed, and the coating peeling in the gridded areas was observed. The results are shown in [Figure 1]. Figure 4 .like Figure 4 As shown, no obvious coating peeling was observed in the gridded area after the tape was peeled off, proving that the obtained coating has strong adhesion and good interfacial bonding stability with the glass substrate.

[0046] In summary, this invention provides a high-hardness organic-inorganic hybrid transparent anti-fog coating and its preparation method. By introducing an organosilicon precursor and enabling it to form a silicon-oxygen network structure in situ in an aqueous phase, this invention significantly improves the coating's hardness and imparts excellent anti-fog properties while maintaining high transparency. Furthermore, the preparation process is simple and controllable, the system is environmentally friendly, and it has broad application prospects and good value for large-scale application.

[0047] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a high-hardness transparent anti-fog coating, characterized in that, Includes the following steps: (1) Mix aminopropyltriethoxysilane and (3-mercaptopropyl)trimethoxysilane in water, add acetic acid to adjust the pH, and stir to prepare an organosilicon precursor solution; (2) Mix the waterborne epoxy resin, triethylenetetramine and the organosilicon precursor liquid obtained in step (1) evenly, and add water to dilute to obtain the coating. (3) Apply the coating obtained in step (2) to the surface of a clean substrate and heat it to cure, thereby obtaining the high-hardness transparent anti-fog coating.

2. The preparation method according to claim 1, characterized in that, The molar ratio of aminopropyltriethoxysilane to (3-mercaptopropyl)trimethoxysilane used in step (1) is 10:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), acetic acid is added to adjust the pH to 7-9.

4. The preparation method according to claim 1, characterized in that, The volume concentration of the organosilicon precursor solution obtained in step (1) is 60-65%.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of water-based epoxy resin to triethylenetetramine is 1:

1.

6. The preparation method according to claim 1, characterized in that, In step (2), the amount of silicone precursor liquid added is 3% to 15% of the mass of the waterborne epoxy resin.

7. The preparation method according to claim 1, characterized in that, In step (2), the amount of water added is 10% to 90% of the mass of the waterborne epoxy resin.

8. The preparation method according to claim 1, characterized in that, In step (3), the coating amount on the substrate surface is 0.02~0.10 mL / cm. 2 .

9. The preparation method according to claim 1, characterized in that, The heating and curing temperature in step (3) is 130°C and the time is 180 min.

10. A high-hardness transparent anti-fog coating prepared by the method described in claim 1.

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