A transparent, scratch-resistant, self-healing coating material and its preparation method

Abstract

This invention discloses a transparent, scratch-resistant, self-healing coating material and its preparation method, belonging to the field of functional coating technology. The preparation method includes the following steps: mixing an epoxy resin monomer containing siloxane segments with an alicyclic amine curing agent to obtain a coating casting solution; subjecting the coating casting solution to vacuum degassing; applying the vacuum-degassed casting solution to a protected substrate while hot, curing, and then removing and cooling to obtain a transparent, scratch-resistant, self-healing coating. This invention utilizes siloxane segments to modify the epoxy resin monomer, optimizing the flexibility and elasticity of the epoxy resin, and uses an alicyclic amine curing agent containing an asymmetric structure to regulate the room temperature viscoelastic response of the coating. By improving the intrinsic recovery ability of the polymer network, the coating is endowed with excellent scratch-resistant and self-healing properties.

Description

Technical Field

[0001] This invention belongs to the field of functional coating technology, specifically relating to a transparent, scratch-resistant, self-healing coating material and its preparation method. Background Technology

[0002] With the rapid development of intelligent electronic devices, precision instruments, and the automotive industry, the demand for transparent, scratch-resistant surface protection materials is increasing daily. Coatings are the most widely used form of surface protection material; they not only enhance the aesthetics of products but also serve as the first line of defense against various external aggressors. Intelligent electronic devices, precision instruments, and automobiles all face numerous scratches and abrasions from sharp objects during use. Damage not only affects the product's appearance but also exposes it directly to physical and chemical aggressors from the user, such as sweat, wind, sand, rain, and snow. Therefore, coating products that are transparent, scratch-resistant, and possess a certain degree of self-healing properties have a huge market demand. Their application is of significant practical importance for extending product lifespan, reducing operating costs, and improving product appearance quality.

[0003] Currently, there are two main strategies for improving the scratch and abrasion resistance of coatings. One is to add lubricants or nanofillers to the polymer, using the lubricant to form a slip layer on the coating surface, reducing the coefficient of friction. When subjected to external forces, the slip layer can absorb some energy, reducing direct damage to the coating. However, this type of coating is prone to lubricant precipitation during long-term use, affecting the coating's stability and durability. The other is to add nanofillers, mainly by increasing the coating's hardness and toughness, thereby dispersing and absorbing internal and external stresses acting on the coating surface. However, the dispersion of nanofillers in the coating is difficult to control; aggregation or uneven dispersion may adversely affect the overall performance of the coating. Regarding coating damage self-healing strategies, based on different self-healing mechanisms, there are two main categories: "external aid" self-healing and "intrinsic" self-healing. "External aid" self-healing involves adding microcapsules (microcapsules, microvessels) loaded with repair agents inside the material. When the material is damaged, the microcapsules rupture and release the repair agent at the damaged site. Under certain conditions, the repair agent solidifies in situ and repairs the material damage. However, this repair method results in a significant difference in appearance between the repaired area and the original coating, leaving noticeable repair "scars." This fails to meet the high requirements for transparency and aesthetics in applications such as smart electronic devices, precision instruments, and automotive surfaces. Furthermore, the effective number of repairs is extremely limited due to the capacity constraints of microcapacitors. Intrinsic self-healing is based on the dynamic and reversible chemical design of the material itself. However, most reversible bond breakage and recombination currently require external energy such as light or heat to trigger, which can affect the coating's intrinsic properties to some extent. The need for human intervention also limits the timeliness and convenience of repair applications. Therefore, developing transparent coatings with good scratch resistance and self-healing properties has always been a hot research topic. Summary of the Invention

[0004] This invention provides a transparent, scratch-resistant, self-healing coating material and its preparation method. The invention uses an asymmetric structure alicyclic amine to cure and regulate the siloxane chain segment-modified epoxy resin monomer to synthesize a transparent, scratch-resistant, self-healing coating, which imparts a viscoelastic response under room temperature conditions, thereby achieving a self-healing response to scratch defects in the coating.

[0005] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing a transparent, scratch-resistant, self-healing coating material includes the following steps:

[0007] (1) The epoxy resin monomer containing siloxane segments is mixed with an alicyclic amine curing agent to obtain a coating casting solution;

[0008] (2) Vacuum degassing treatment is performed on the coating casting solution;

[0009] (3) Apply the vacuum degassed casting liquid to the protected substrate while it is still hot, cure it, and then take it out and cool it to obtain a transparent scratch-resistant self-healing coating.

[0010] In step (1), the molar ratio of the epoxy resin monomer to the alicyclic amine curing agent is 1:0.5-1:1; the stirring conditions are a temperature of 25℃ and a stirring time of 1-2h.

[0011] The epoxy resin monomer is 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane, and the alicyclic amine curing agent is an alicyclic amine curing agent containing an asymmetric structure.

[0012] The alicyclic amine curing agent containing an asymmetric structure is isophorone diamine or methylcyclohexanediamine.

[0013] In step (2), the vacuum degassing conditions are: temperature 60-70℃ and degassing time 15-30min.

[0014] In step (3), the coating method is spraying, brushing, pouring or dipping; the curing temperature is 60-100°C and the curing time is 4-12h.

[0015] The present invention also provides a transparent, scratch-resistant, self-healing coating material, which is prepared by the above-described method.

[0016] The technical solution adopted in this invention is to improve the inherent scratch resistance and self-healing properties of the coating by regulating molecular motion, i.e., the bond deformation ability of the coating's molecular structure. Specifically, by regulating the chemical composition of the coating, a balance between elasticity and plastic deformation is achieved, thereby obtaining ideal viscoelastic behavior. This adjustment allows the coating to absorb and release energy through the movement of molecular chains when subjected to mechanical loads, achieving self-recovery. Regulating the movement of coating molecular chains is a cost-effective and innovative approach. It not only promotes the plastic deformation ability of the coating and enhances its self-recovery after scratches, but also retains good transparency characteristics because it does not involve the addition of any fillers or additives. However, achieving viscoelastically driven surface recovery requires finding a balance between several performance parameters, including the dynamic healing ability related to room temperature, which is affected by the glass transition temperature (T0) of the coating. g The chemical properties of the coating, especially the molecular structure of the polymer and the degree of crosslinking of the polymer network, also play a decisive role in the overall performance of the coating. Therefore, the key to constructing a scratch-self-healing transparent coating material driven solely by intrinsic mechanisms lies in maintaining the polymer's T... g Below room temperature, it enhances the migration ability of polymer chains. After the coating is scratched, low T gThe unique viscoelasticity of polymer chains can trigger chain segment migration, while inducing bond stretching, increasing the contact probability of broken bonds, and further restoring them to their original shape.

[0017] Epoxy resins possess excellent mechanical properties, adhesive properties, and chemical stability, making them the most widely used coating resins. However, traditional epoxy resin materials have a dense, cross-linked three-dimensional network, resulting in cured products that are brittle, have low impact strength, and are highly susceptible to scratches. (Silica segment T) g It has low temperature sensitivity, good weather resistance and temperature change resistance, and its segments are flexible and hydrophobic. Introducing it into epoxy resin can significantly improve the coating's flexibility, elasticity, weather resistance, and enhance its waterproof, dustproof, and flame-retardant properties. Although introducing flexible segments can reduce the coating's temperature gradient (Tg), it also provides good weather resistance and temperature change resistance. g And improves coating rigidity, but T g Excessively low viscosity can negatively impact the viscoelastic response of the coating at room temperature. To address this, introducing curing agents with specific structures into the design of silica-oxygen segment epoxy resin systems can optimize the coating's viscoelasticity to some extent. Alicyclic amine curing agents possess a saturated six-membered ring structure and exhibit characteristics similar to polyetheramines: multiple spatial conformations and good flexibility. They also share characteristics with aromatic amines: the rigidity and strength of their cyclic structures. More importantly, the steric hindrance effect introduced by asymmetric alicyclic amines can significantly improve the coating's plasticizing effect, thereby enhancing its overall performance. Through structural design, it is hoped that strength, toughness, scratch resistance, and self-healing properties can be integrated. Furthermore, most alicyclic amine curing agents are low-viscosity liquids, and the color and gloss of the cured products are superior to those of aliphatic amines and polyamides.

[0018] The technical solution provided by this invention has the following advantages compared with the prior art:

[0019] This invention utilizes siloxane segments to modify epoxy resin monomers, optimizing the flexibility and elasticity of epoxy resins. It also uses alicyclic amine curing agents with asymmetric structures to regulate the room temperature viscoelastic response of the coating. By improving the intrinsic recovery ability of the polymer network, the coating is endowed with excellent scratch resistance and self-healing properties.

[0020] This invention provides a transparent, scratch-resistant, self-healing coating material and its preparation method. The raw materials required in this invention are all commercially available products. The preparation process does not require any chemical modification steps and can be applied in various ways, making it suitable for large-scale production. Attached Figure Description

[0021] Figure 1 Infrared spectrum of siloxane-modified epoxy coating;

[0022] Figure 2 The image shows the DSC analysis results for the siloxane-modified epoxy coating.

[0023] Figure 3The scratches on the surface of the siloxane-modified epoxy coating during 100 cycles of cyclic scraping with a steel brush;

[0024] Figure 4 To show the scratches on the surface of the siloxane-modified epoxy coating after 5 cycles of cyclic scraping with a steel brush as a comparative example.

[0025] Figure 5 Thermogravimetric analysis (TGA) diagram of siloxane-modified epoxy coating;

[0026] Figure 6 The transmittance is the light transmittance of the siloxane-modified epoxy coating. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0028] This embodiment provides a method for preparing a transparent, scratch-resistant, self-healing coating material, including the following steps:

[0029] (1) 1 kg of 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane and 0.19 kg of methylcyclohexanediamine (molar ratio of the two is 1:0.5) were placed in a reaction vessel, stirred and mixed, the reaction vessel temperature was set at 25℃ and the stirring time was 1.5 h to obtain the coating casting solution;

[0030] (2) The coating casting solution was subjected to vacuum degassing treatment. The vacuum degassing conditions were: temperature 65℃ and degassing time 25min.

[0031] (3) Apply the vacuum degassed casting liquid to the protected substrate while it is still hot by spraying, brushing, pouring or dipping, then cure it in an oven at 80°C for 8 hours, and then take it out and let it cool naturally to obtain a transparent scratch-resistant self-healing coating. Example 2

[0032] This embodiment provides a method for preparing a transparent, scratch-resistant, self-healing coating material, including the following steps:

[0033] (1) 1 kg of 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane and 0.46 kg of isophorone diamine (molar ratio of the two is 1:1) were placed in a reaction vessel, stirred and mixed, the reaction vessel temperature was set to 25℃, and the stirring time was 1 h to obtain the coating casting solution.

[0034] (2) The coating casting solution was subjected to vacuum degassing treatment. The vacuum degassing conditions were: temperature 60℃ and degassing time 30min.

[0035] (3) Apply the vacuum degassed casting liquid to the protected substrate while it is still hot by spraying, brushing, pouring or dipping, then cure it in an oven at 60°C for 12 hours, and then take it out and let it cool naturally to obtain a transparent scratch-resistant self-healing coating.

[0036] Comparative Example 1

[0037] The difference between Comparative Example 1 and Example 2 is that isophorone diamine is replaced with polyetheramine, including the following steps:

[0038] (1) 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane with a molar ratio of 1:1 was stirred and mixed with polyetheramine under the following conditions: temperature 25℃ and stirring time 2h to obtain coating casting solution.

[0039] (2) The coating casting solution was subjected to vacuum degassing treatment. The vacuum degassing conditions were: temperature 70℃ and degassing time 15min.

[0040] (3) The casting liquid after vacuum degassing is applied to the protected substrate by spraying, brushing, pouring or dipping while it is still hot, and then cured at 100°C for 4 hours. After that, it is taken out and cooled to obtain the coating.

[0041] This invention utilizes a siloxane-modified epoxy resin as the coating film-forming material and an asymmetric alicyclic amine as the coating curing agent. By controlling the glass transition temperature of the coating, and thus regulating the polymer molecular chain motion, viscoelastic-driven self-repair of surface scratches is achieved. A comparison of the infrared spectra of the siloxane-modified epoxy coating and its monomer is provided. Figure 1 The figure shows 909 cm. -1 The disappearance of the characteristic vibrational bands of the epoxy groups at the coating sample indicates that the epoxy resin has completed curing. The steric hindrance effect provided by the asymmetric structure in the alicyclic amine enhances the plasticizing effect, such as... Figure 2 As shown, the glass transition temperature of the coating is 9.4 °C. This lower glass transition temperature promotes the coating's viscous response and effective elastic behavior, enhancing its self-recovery response at room temperature. Figure 3 As shown, a copper brush was used to scrape the prepared transparent coating 100 times. (a) is an optical microscope image, and (b) is a high-definition lens recording. Observation under the optical microscope revealed that the scratches on the coating surface disappeared almost instantly, leaving no scratch marks on the final coating surface, demonstrating excellent scratch resistance and self-healing performance. In contrast, the comparative example showed severe scratches after only 5 scraping cycles. Figure 4Due to the stability of the silicon-oxygen bond, the coating can withstand high temperatures without easily decomposing. The thermal decomposition temperature of the siloxane-modified epoxy coating sample was determined by thermogravimetric analysis. The decomposition temperature (T0) was determined when the sample weight loss rate was 5%. 5% ) reached 354 ℃ ( Figure 5 Furthermore, this coating system does not involve the addition of any third components such as fillers or additives, allowing the coating to retain good transparency and gloss. Figure 6 As shown, the coating exhibits a visible light transmittance greater than 90% and a gloss level (at a 60° angle) of 113.7. These excellent optical properties allow the coating to maintain the material's original color and superior gloss without affecting its appearance design. Furthermore, the scratch damage repair behavior of the coating surface in this invention requires no triggering conditions, thus offering significant advantages such as rapid and controllable response and diverse application scenarios.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a transparent, scratch-resistant, self-healing coating material, characterized in that... Includes the following steps: (1) A coating casting solution is obtained by stirring and mixing an epoxy resin monomer containing siloxane segments with an alicyclic amine curing agent; the epoxy resin monomer is 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane, and the alicyclic amine curing agent is an alicyclic amine curing agent containing an asymmetric structure; the alicyclic amine curing agent containing an asymmetric structure is isophorone diamine or methylcyclohexanediamine; (2) Vacuum degassing treatment is performed on the coating casting solution; (3) Apply the vacuum degassed casting liquid to the protected substrate while it is still hot, cure it, and then take it out and cool it to obtain a transparent scratch-resistant self-healing coating.

2. The method for preparing a transparent, scratch-resistant, self-healing coating material according to claim 1, characterized in that: In step (1), the molar ratio of the epoxy resin monomer to the alicyclic amine curing agent is 1:0.5-1:1; the stirring conditions are a temperature of 25℃ and a stirring time of 1-2h.

3. The method for preparing a transparent, scratch-resistant, self-healing coating material according to claim 1, characterized in that: In step (2), the vacuum degassing conditions are: temperature 60-70℃, degassing time 15-30min.

4. The method for preparing a transparent, scratch-resistant, self-healing coating material according to claim 1, characterized in that: In step (3), the coating method is spraying, brushing, pouring or dipping; the curing temperature is 60-100°C and the curing time is 4-12h.

5. A transparent, scratch-resistant, self-healing coating material, characterized in that... It is prepared by any one of the preparation methods of claims 1-4.

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