Yellowing-resistant high-gloss finish paint for interior and exterior decoration of automobile and preparation method of yellowing-resistant high-gloss finish paint
By constructing a high cross-linking density network structure in automotive interior and exterior paints using benzotriazole-based silane coupling agents, cross-linking resins, and organosiloxane microspheres, the problem of synergistic optimization between high gloss and yellowing resistance was solved, achieving long-term stability and gloss retention of the coating.
Patent Information
- Application Number
- CN202512003830.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-07
AI Technical Summary
Existing automotive interior and exterior paints struggle to achieve a balance between high gloss and resistance to yellowing. Traditional methods often result in light stabilizers that are prone to migration or volatilization, film-forming resins that are susceptible to photo-oxidative aging, insufficient coating density, and inadequate interfacial stability, all of which negatively impact long-term performance.
An interface layer is formed by using a silane coupling agent containing a benzotriazole structure, and a host layer is formed by cross-linking high-hydroxyl content acrylic resin and amino-modified nano-silica. Organosiloxane microspheres are enriched on the surface to construct a three-dimensional network structure with high cross-linking density.
It achieves resistance to yellowing and long-lasting high gloss in the coating, ensuring the uniformity and stability of the paint film and meeting the durability and appearance quality requirements of automotive interior and exterior trim.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of finish technology, in particular to a yellowing-resistant high-gloss finish for automotive interior and exterior trim and a preparation method thereof. BACKGROUND
[0002] Currently, the performance improvement of automotive interior and exterior trim finish always faces the core challenge of the difficulty in the synergistic optimization of high initial gloss and long-term weather resistance, especially the yellowing resistance. Traditional technical paths often focus on the improvement of a single performance, and there are significant limitations in realizing the persistent unity of the two, which is mainly due to the inherent deficiencies in material selection and system construction. In terms of yellowing resistance, conventional methods often rely on the physical mixing of ultraviolet absorbers and other light stabilizers in the coating formula.
[0003] However, these additives may migrate or volatilize after the curing of the paint film, and their protective effect decays over time; more fundamentally, many widely used film-forming resins contain chemical structures in their molecular chains that are susceptible to ultraviolet light attack, and under long-term light exposure, they will undergo photo-oxidative aging and generate chromophoric groups, leading to irreversible yellowing and darkening of the coating. This yellowing caused by the resin itself is difficult to completely inhibit by adding external additives. In terms of achieving and maintaining high gloss, existing technologies usually obtain excellent initial surface flatness by improving the leveling property of the resin or adding additives, but they lack sufficient durability in maintaining gloss. The hardness of the paint film surface is insufficient, and the wear resistance is poor, so that fine scratches are easily generated in daily use, leading to increased light scattering and rapid decline in gloss. At the same time, if the compatibility between various components in the coating, such as resins, fillers, and additives, is poor, or if they separate during the curing process, the micro-uniformity of the paint film will be destroyed, forming light scattering points that not only affect the purity of the initial gloss, but also become a breakthrough for environmental stress, accelerating local aging and loss of gloss. In addition, the existing coating structure is often single-function, and the interface between the layers is mainly combined by physical adhesion, lacking strong chemical bonding, which leads to insufficient interface stability under environmental stresses such as heat and humidity, which may affect the reliability of the overall performance.
[0004] Therefore, it is of urgent significance to develop a finish technology that can design the molecular structure to achieve high gloss while endogenously and durably imparting yellowing resistance to the coating, and to construct a stable, dense, and synergistically acting coating system to maintain this comprehensive performance for a long time, in order to meet the dual demands of extreme aesthetics and ultra-long durability for high-end automotive interior and exterior trim. SUMMARY
[0005] The purpose of the present application is to provide a yellowing-resistant high-gloss finish for automotive interior and exterior trim and a preparation method thereof, to solve the problems existing in the prior art.
[0006] To solve the above technical problems, the present application provides the following technical solutions: a yellowing-resistant high-gloss topcoat for automotive interior and exterior trim, characterized in that the topcoat comprises an interface layer formed by a silane coupling agent containing a benzotriazole structure, which is combined with a substrate; a main resin layer located above the interface layer, which is formed by cross-linking and curing of a high-hydroxyl-content acrylic resin, amino-surface-modified nanosilica, and an aliphatic isocyanate curing agent; and a surface layer enriched on the surface of the main resin layer, which is composed of organosiloxane microspheres.
[0007] Further, a preparation method of a yellowing-resistant high-gloss topcoat for automotive interior and exterior trim comprises the following preparation steps: (1) Mix self-made silane coupling agent containing a benzotriazole structure with anhydrous ethanol at a mass ratio of 1:8-1:10, stir at 45-55°C for 25-35 min, and prepare an interface pretreatment agent for standby use; prepare the main coating slurry by adding 95-105 parts by mass of high-hydroxyl-content acrylic resin, 12-18 parts by mass of amino-modified nanosilica, 4-6 parts by mass of organosiloxane microspheres, and 0.3-0.7 parts by mass of catalyst in a reaction vessel in sequence, heat the mixed system to 75-85°C, and mix under normal pressure for 1.5-2.5 h; then cool the system to 35-45°C, and slowly add 28-32 parts by mass of curing agent under continuous stirring within 15-25 min, continue to heat and stir for 0.8-1.2 h after the addition is completed, and obtain the topcoat slurry; (2) First, clean the substrate, uniformly spray a layer of self-made interface pretreatment agent, level at room temperature for 8-12 min, and then move it into an oven at 75-85°C for drying for 15-25 min; then spray the main coating slurry, level at room temperature for 10-20 min; finally, place the workpiece in an oven at 115-125°C for baking for 25-35 min to achieve complete curing of the coating; the entire coating process should be carried out under the condition of an environmental humidity of 60%, and the topcoat is prepared by controlling the catalyst dosage to be between 0.01% and 0.5% and ensuring sufficient curing.
[0008] Further, the preparation method of the silane coupling agent containing a benzotriazole structure in step (1) is as follows: mix benzotriazole with γ-glycidyl ether oxypropyl trimethoxysilane, and perform ring-opening reaction at a temperature of 45-55°C and a stirring speed of 280-320 r / min for 2.5-3.5 h.
[0009] Further, the molar ratio of benzotriazole to γ-glycidyl ether oxypropyl trimethoxysilane is 1:1.1-1:1.3.
[0010] Furthermore, in step (1), the amino-modified nano-silica is prepared using a sol-gel process, with tetraethyl orthosilicate as the silicon source. Hydrolysis and condensation are completed under the catalysis of ammonia water with a concentration of 0.1-0.3 mol / L for 4-6 h. Subsequently, triaminopropyltriethoxysilane equivalent to 8%-12% of the mass of silica is added, and its surface is modified and grafted at 60-80 °C. Surface modification reaction is carried out at 60-80 °C for 1.5-2.5 h.
[0011] Furthermore, in step (1), the organosiloxane microspheres are prepared by co-hydrolysis and polycondensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7:3-8:2, and are prepared under the catalysis of ammonia water with a concentration of 0.1-0.3mol / L at 50-70℃.
[0012] Furthermore, the average particle size of the organosiloxane microspheres is controlled to be 1.0-5.0 μm by adjusting the reaction time.
[0013] Furthermore, the catalyst in step (1) is dibutyltin dilaurate.
[0014] Furthermore, the curing agent in step (1) is an aliphatic isocyanate.
[0015] Furthermore, in step (2), the wet film thickness of the main coating slurry is 110-130 μm.
[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention relates to a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim. Through the synergistic construction of an interfacial UV absorption layer, a highly cross-linked host layer, and a surface reinforcement layer, the topcoat simultaneously achieves significant yellowing resistance and long-lasting high gloss.
[0017] First, the substrate is pretreated with a silane coupling agent containing a benzotriazole structure. The alkoxy group at one end of the coupling agent forms a chemical bond with the substrate surface, while the benzotriazole structural unit at the other end is covalently fixed to the interface layer. This structure preferentially absorbs ultraviolet light, effectively inhibiting photo-oxidation and providing a fundamental guarantee against yellowing for the coating. High-hydroxyl-content acrylic resin is selected as the main film-forming material, combined with surface-modified nano-silica. The nanoparticles are uniformly dispersed in the resin, and their surface functional groups form a high-density cross-linked network with the hydroxyl groups of the resin during curing. This structure increases the film density and surface smoothness, laying the foundation for high-gloss performance.
[0018] Secondly, organosiloxane microspheres are introduced. During the curing process, these microspheres migrate to the coating surface, interconnect through siloxane bonds, and combine with the resin system to form a continuous surface layer. This surface layer has high surface hardness and chemical inertness, maintaining the smoothness of the paint film and ensuring long-lasting gloss. All components form an integrated three-dimensional network structure during curing through reactive groups such as vinyl, siloxane, and hydroxyl groups. This structure avoids phase separation of components, ensuring the uniformity and stability of the paint film, and fundamentally preventing gloss reduction or color change caused by localized degradation.
[0019] In summary, the coating of this invention can maintain color stability and surface gloss for a long time, meeting the requirements of automotive interior and exterior trim for durability and appearance quality. Detailed Implementation
[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0021] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The following embodiments describe the testing methods for various indicators of a high-gloss, yellowing-resistant topcoat for automotive interior and exterior trim: Yellowing resistance test: First, use a colorimeter to measure the yellowness value of the film before it has been cured under strong light and high temperature conditions as the initial value. After 6 hours of continuous high temperature (80℃) and ultraviolet light intensity (30mW / cm²), the yellowness resistance test is performed. 2 Then, a colorimeter was used to measure the yellowness value of all sample films, and the difference before and after was taken as the yellowing index.
[0022] Performance indicators are in accordance with GB / 23997-2009. Example 1
[0023] (1) The synthesis of silane coupling agents containing benzotriazole structure was carried out by reacting benzotriazole with γ-glycidoxypropyltrimethoxysilane at a molar ratio of 1:1.1 at 45℃ and a stirring speed of 280 r / min for 2.5 h; the amino-modified nano-silica was prepared by sol-gel process, using tetraethyl orthosilicate as silicon source, and the hydrolysis condensation was completed under the catalysis of 0.1 mol / L ammonia water for 4 h. Subsequently, triaminopropyltriethoxysilane, equivalent to 8% of the mass of silica, was added, and its surface was modified and grafted at 60°C. The surface modification reaction was carried out at 60°C for 1.5 h. The organosiloxane microspheres were prepared by co-hydrolysis and polycondensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7:3. The average particle size was controlled to 1.0 μm by adjusting the reaction time under the catalysis of 0.1 mol / L ammonia water at 50°C. (2) The self-made benzotriazole silane coupling agent and anhydrous ethanol were mixed at a mass ratio of 1:8 and stirred at 45°C and 280 r / min for 25 min to prepare an interface pretreatment agent for later use. The preparation of the main coating slurry was carried out by adding 95 parts by mass of high hydroxyl content acrylic resin, 12 parts by mass of amino modified nano silica, 4 parts by mass of organosiloxane microspheres and 0.3 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence. The mixture was heated to 75°C and mixed at atmospheric pressure and stirring speed of 480 r / min for 1.5 h. Then the system was cooled to 35°C and 28 parts by mass of aliphatic isocyanate curing agent were slowly added within 15 min under continuous stirring. After the addition was completed, the mixture was kept warm and stirred for 0.8 h to obtain the topcoat slurry. (3) First, clean the substrate and spray a layer of self-made interface pretreatment agent evenly. After leveling at room temperature for 8 minutes, transfer it to an oven at 75°C and dry for 15 minutes. Then, spray the main coating slurry with a wet film thickness of 110 μm and level at room temperature for 10 minutes. Finally, place the workpiece in an oven at 115°C and bake for 25 minutes to achieve complete curing of the coating. The entire coating process should be carried out under an ambient humidity of 60%. The topcoat is obtained by controlling the amount of catalyst between 0.01% and ensuring full curing. Example 2
[0024] (1) The synthesis of silane coupling agents containing benzotriazole structures involved reacting benzotriazole with γ-glycidoxypropyltrimethoxysilane at a molar ratio of 1:1.2 at 50°C and a stirring speed of 300 r / min for 3.0 h. The amino-modified nano-silica was prepared using a sol-gel process, with tetraethyl orthosilicate as the silicon source, and hydrolysis condensation was carried out under the catalysis of 0.2 mol / L ammonia for 5.0 h. Then, triaminopropyltriethoxysilane, equivalent to 10% of the mass of silica, was added, and its surface was modified and grafted at 70°C. The surface modification reaction was carried out at 70°C for 2.0 h. The organosiloxane microspheres were prepared by co-hydrolysis and condensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7.5:2.5. The average particle size was controlled to 3.0 μm by adjusting the reaction time under the catalysis of 0.2 mol / L ammonia water at 60°C. (2) The self-made benzotriazole silane coupling agent and anhydrous ethanol were mixed at a mass ratio of 1:9 and stirred at 50°C and 300r / min for 30 min to prepare an interface pretreatment agent for later use. The preparation of the main coating slurry was carried out by adding 100 parts by mass of high hydroxyl content acrylic resin, 15 parts by mass of amino-modified nano silica, 5 parts by mass of organosiloxane microspheres and 0.5 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence. The mixture was heated to 80°C and mixed at atmospheric pressure and stirring speed of 500r / min for 2.0 h. Then the system was cooled to 40°C and 30 parts by mass of aliphatic isocyanate curing agent were slowly added within 20 min under continuous stirring. After the addition was completed, the mixture was kept warm and stirred for 1.0 h to obtain the topcoat slurry. (3) First, clean the substrate and spray a layer of self-made interface pretreatment agent evenly. After leveling at room temperature for 10 minutes, transfer it to an oven at 80°C and dry for 20 minutes. Then, spray the main coating slurry with a wet film thickness of 120 μm and level at room temperature for 15 minutes. Finally, place the workpiece in an oven at 120°C and bake for 30 minutes to achieve complete curing of the coating. The entire coating process should be carried out under an ambient humidity of 60%. The topcoat is obtained by controlling the amount of catalyst between 0.26% and ensuring full curing. Example 3
[0025] (1) The synthesis of silane coupling agents containing benzotriazole structure was carried out by reacting benzotriazole with γ-glycidoxypropyltrimethoxysilane at a molar ratio of 1:1.3 at 55℃ and a stirring speed of 320 r / min for 3.5 h; the amino-modified nano-silica was prepared by sol-gel process, using tetraethyl orthosilicate as silicon source, and the hydrolysis condensation was completed under the catalysis of 0.3 mol / L ammonia water for 6 h. Subsequently, triaminopropyltriethoxysilane, equivalent to 12% of the mass of silica, was added, and its surface was modified and grafted at 80°C. The surface modification reaction was carried out at 80°C for 2.5 h. The organosiloxane microspheres were prepared by co-hydrolysis and polycondensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 8:2. The average particle size was controlled to 5.0 μm by adjusting the reaction time under the catalysis of 0.3 mol / L ammonia water at 70°C. (2) The self-made benzotriazole silane coupling agent and anhydrous ethanol were mixed at a mass ratio of 1:10 and stirred at 55℃ and 320 r / min for 35 min to prepare an interface pretreatment agent for later use. The preparation of the main coating slurry was carried out by adding 105 parts by mass of high hydroxyl content acrylic resin, 18 parts by mass of amino modified nano silica, 6 parts by mass of organosiloxane microspheres and 0.7 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence. The mixture was heated to 85℃ and mixed at atmospheric pressure and stirring speed of 520 r / min for 2.5 h. Then the system was cooled to 45℃ and 32 parts by mass of aliphatic isocyanate curing agent were slowly added within 25 min under continuous stirring. After the addition was completed, the mixture was kept warm and stirred for 1.2 h to obtain the topcoat slurry. (3) First, clean the substrate and spray a layer of self-made interface pretreatment agent evenly. After leveling at room temperature for 12 minutes, transfer it to an oven at 85°C and dry for 25 minutes. Then, spray the main coating slurry with a wet film thickness of 130 μm and level at room temperature for 20 minutes. Finally, place the workpiece in an oven at 125°C and bake for 35 minutes to achieve complete curing of the coating. The entire coating process should be carried out under an ambient humidity of 60%. The topcoat is obtained by controlling the amount of catalyst to between 0.5% and ensuring full curing.
[0026] Comparative Example 1 The difference between Comparative Example 1 and Example 2 lies in the difference between steps (1) and (2). Steps (1) and (2) are changed to: (1) The nano-silica modified with amino surface is prepared by sol-gel process, with tetraethyl orthosilicate as silicon source, hydrolysis and condensation are completed under the catalysis of ammonia water with a concentration of 0.2 mol / L, the reaction time is 5.0 h, then triaminopropyltriethoxysilane equivalent to 10% of the mass of silica is added, and its surface is modified and grafted at 70 °C, and the surface modification reaction is carried out at 70 °C for 2.0 h; organosiloxane microspheres are prepared by co-hydrolysis and condensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7.5:2.5, and the average particle size is controlled to 3.0 μm by adjusting the reaction time under the catalysis of ammonia water with a concentration of 0.2 mol / L at 60 °C; (2) Mix γ-aminopropyltriethoxysilane and anhydrous ethanol at a mass ratio of 1:9 and stir at 50°C and 300 r / min for 30 min to prepare an interface pretreatment agent for later use; the preparation of the main coating slurry is to add 100 parts by mass of high hydroxyl content acrylic resin, 15 parts by mass of amino-modified nano silica, 5 parts by mass of organosiloxane microspheres and 0.5 parts by mass of dibutyltin dilaurate catalyst in a reaction vessel in sequence, heat the mixture to 80°C and mix at atmospheric pressure and stirring speed of 500 r / min for 2.0 h; then cool the system to 40°C and slowly add 30 parts by mass of aliphatic isocyanate curing agent within 20 min under continuous stirring. After the addition is completed, continue to keep warm and stir for 1.0 h to obtain the topcoat slurry; the remaining steps are the same as in Example 2.
[0027] Comparative Example 2 The difference between Comparative Example 2 and Example 2 lies in the difference between steps (1) and (2). Steps (1) and (2) are changed to: (1) The synthesis of silane coupling agent containing benzotriazole structure is obtained by reacting benzotriazole and γ-glycidoxypropyltrimethoxysilane at a molar ratio of 1:1.2 at a temperature of 50°C and a stirring speed of 300r / min for 3.0h; organosiloxane microspheres are obtained by co-hydrolysis and polycondensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7.5:2.5, and the average particle size is controlled to 3.0μm by adjusting the reaction time under the catalysis of ammonia water with a concentration of 0.2mol / L at 60°C; (2) The self-made benzotriazole silane coupling agent and anhydrous ethanol were mixed at a mass ratio of 1:9 and stirred at 50°C and 300 r / min for 30 min to prepare an interface pretreatment agent for later use. The preparation of the main coating slurry was carried out by adding 100 parts by mass of high hydroxyl content acrylic resin, 15 parts by mass of nano silica, 5 parts by mass of organosiloxane microspheres and 0.5 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence. The mixture was heated to 80°C and mixed at atmospheric pressure and stirring speed of 500 r / min for 2.0 h. Then the system was cooled to 40°C and 30 parts by mass of aliphatic isocyanate curing agent were slowly added within 20 min under continuous stirring. After the addition was completed, the mixture was kept warm and stirred for 1.0 h to obtain the topcoat slurry. The remaining steps were the same as in Example 2.
[0028] Comparative Example 3 The difference between Comparative Example 3 and Example 2 lies in the difference between steps (1) and (2). Steps (1) and (2) are changed to: (1) The synthesis of silane coupling agent containing benzotriazole structure is obtained by reacting benzotriazole and γ-glycidoxypropyltrimethoxysilane at a molar ratio of 1:1.2 at a temperature of 50°C and a stirring speed of 300r / min for 3.0h; the nano silica modified with amino surface is prepared by sol-gel process, using tetraethyl orthosilicate as silicon source, and hydrolysis condensation is completed under the catalysis of ammonia water with a concentration of 0.2mol / L for 5.0h. Then, triaminopropyltriethoxysilane equivalent to 10% of the mass of silica is added, and its surface is modified and grafted at 70°C. The surface modification reaction is carried out at a temperature of 70°C for 2.0h. (2) The self-made benzotriazole silane coupling agent and anhydrous ethanol were mixed at a mass ratio of 1:9 and stirred at 50°C and 300 r / min for 30 min to prepare an interface pretreatment agent for later use. The preparation of the main coating slurry was carried out by adding 100 parts by mass of high hydroxyl content acrylic resin, 15 parts by mass of amino-modified nano silica, 5 parts by mass of organosiloxane microspheres and 0.5 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence. The mixture was heated to 80°C and mixed at atmospheric pressure and stirring speed of 500 r / min for 2.0 h. Then the system was cooled to 40°C and 30 parts by mass of aliphatic isocyanate curing agent were slowly added within 20 min under continuous stirring. After the addition was completed, the mixture was kept warm and stirred for 1.0 h to obtain the topcoat slurry. The remaining steps were the same as in Example 2.
[0029] Comparative Example 4 The difference between Comparative Example 4 and Example 2 lies in step (2). Step (2) is changed to: (2) Mix the self-made benzotriazole silane coupling agent with anhydrous ethanol at a mass ratio of 1:9 and stir for 30 min at 50°C and 300 r / min to prepare an interface pretreatment agent for later use; The preparation of the main coating slurry is to add 100 parts by mass of high hydroxyl content acrylic resin, 15 parts by mass of amino-modified nano silica, 5 parts by mass of organosiloxane microspheres and 0.5 parts by mass of dibutyltin dilaurate catalyst to the reaction vessel in sequence, heat the mixed system to 80°C, and mix for 2.0 h at atmospheric pressure and stirring speed of 500 r / min; Then cool the system to 40°C and slowly add 30 parts by mass of toluene diisocyanate trimer curing agent within 20 min under continuous stirring. After the addition is completed, continue to keep warm and stir for 1.0 h to obtain the topcoat slurry; The remaining steps are the same as in Example 2.
[0030] Comparative Example 5 The difference between Comparative Example 5 and Example 2 lies in step (3). Step (3) is changed to: first, clean the substrate, uniformly spray a layer of self-made interface pretreatment agent, level it at room temperature for 10 min, and then dry it in an oven at 80°C for 20 min; then spray the main coating slurry with a wet film thickness of 120 μm, level it at room temperature for 15 min; finally, place the workpiece in an oven at 120°C and bake it for 10 min to achieve complete curing of the coating; the entire coating process should be carried out under an ambient humidity of 60%, and the topcoat is obtained by controlling the amount of catalyst between 0.26% and ensuring sufficient curing; the remaining steps are the same as in Example 2.
[0031] Example of effect Table 1 below presents the performance analysis results of a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim, using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.
[0032] Table 1
[0033] A comparison of the experimental data on yellowing resistance index between the examples and comparative examples reveals that the present invention, through the use of a silane coupling agent containing a benzotriazole structure for interfacial treatment and an aliphatic isocyanate curing system, achieves a significant effect in inhibiting the photo-oxidative aging of the coating. The yellowing index of Example 2 is 1.5, while that of Comparative Example 1 and Comparative Example 4, which uses an aromatic curing agent, increases to 4.5 and 8.0, respectively. This data indicates that the UV-absorbing groups chemically bonded at the interface and the intrinsic stability of the aliphatic curing agent together constitute the basis for the coating's yellowing resistance. A comparison of the experimental data on 60° gloss level between the examples and comparative examples reveals that the present invention, by constructing a high cross-linking density matrix and introducing surface-enriched organosiloxane microspheres, achieves the effect of obtaining and maintaining extremely high surface gloss. The gloss level of Example 2 is 96, while that of Comparative Examples 2 and 3 decreases to 88 and 90, respectively. This confirms the contribution of surface-modified nano-silica to the density and smoothness of the paint film, and the key role of organosilica microspheres in forming a high-hardness surface protective layer and reducing light scattering. A comparison of the comprehensive experimental data on adhesion, pencil hardness, and flexibility of the examples and comparative examples reveals that the present invention achieves an optimized balance of mechanical properties by forming a uniform and stable three-dimensional network structure through the reactive groups of each component. All examples maintained a grade 0 adhesion, a pencil hardness of H to 2H, and a flexibility of 2 to 3 mm, while Comparative Examples 2, 4, and 5 showed a decrease in different performance indicators, demonstrating the effectiveness of the integrated network structure in preventing component phase separation and ensuring the overall durability of the coating.
[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.
Claims
1. A high-gloss, yellowing-resistant topcoat for automotive interior and exterior trim, characterized in that, The topcoat includes an interface layer bonded to the substrate, formed by a silane coupling agent containing a benzotriazole structure; The main resin layer located above the interface layer is formed by cross-linking and curing of high hydroxyl content acrylic resin, amino-surface modified nano-silica and aliphatic isocyanate curing agent; And a surface layer enriched on the surface of the main resin layer, which is composed of organosiloxane microspheres.
2. A method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim, characterized in that, The preparation steps include the following: (1) Mix the self-made benzotriazole silane coupling agent with anhydrous ethanol at a mass ratio of 1:8-1:10 and stir at 45-55℃ for 25-35 min to prepare an interface pretreatment agent for later use; the preparation of the main coating slurry is to add 95-105 parts by mass of high hydroxyl content acrylic resin, 12-18 parts by mass of amino modified nano silica, 4-6 parts by mass of organosiloxane microspheres and 0.3-0.7 parts by mass of catalyst in sequence in the reaction vessel, heat the mixture to 75-85℃ and mix at normal pressure for 1.5-2.5 h; then cool the system to 35-45℃ and slowly add 28-32 parts by mass of curing agent within 15-25 min under continuous stirring. After the addition is completed, continue to keep warm and stir for 0.8-1.2 h to obtain the topcoat slurry; (2) First clean the substrate, then spray a layer of self-made interface pretreatment agent evenly, level it at room temperature for 8-12 minutes, and then put it into an oven at 75-85℃ to dry for 15-25 minutes. Then, spray the main coating slurry and level it at room temperature for 10-20 minutes; finally, place the workpiece in an oven at 115-125℃ and bake for 25-35 minutes to achieve complete curing of the coating; the entire coating process should be carried out under an ambient humidity of 60%, and the topcoat is obtained by controlling the amount of catalyst between 0.01% and 0.5% and ensuring full curing.
3. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, The preparation method of the silane coupling agent containing the benzotriazole structure in step (1) is as follows: benzotriazole is mixed with γ-glycidyl etheroxypropyltrimethoxysilane and subjected to a ring-opening reaction at a temperature of 45-55℃ and a stirring speed of 280-320r / min for 2.5-3.5h.
4. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, The molar ratio of benzotriazole to γ-glycidoxypropyltrimethoxysilane is 1:1.1 to 1:1.
3.
5. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, In step (1), the amino-modified nano-silica is prepared by a sol-gel process, using tetraethyl orthosilicate as the silicon source. Hydrolysis and condensation are completed under the catalysis of ammonia water with a concentration of 0.1-0.3 mol / L for 4-6 h. Then, triaminopropyltriethoxysilane equivalent to 8%-12% of the mass of silica is added, and its surface is modified and grafted at 60-80 °C. Surface modification reaction is carried out at 60-80 °C for 1.5-2.5 h.
6. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, In step (1), the organosiloxane microspheres are prepared by co-hydrolysis and condensation of phenyltrimethoxysilane and dimethyldimethoxysilane at a mass ratio of 7:3-8:2, and are prepared at 50-70°C under the catalysis of ammonia water with a concentration of 0.1-0.3 mol / L.
7. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 6, characterized in that, The average particle size of the organosiloxane microspheres is controlled to be 1.0-5.0 μm by adjusting the reaction time.
8. The method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, The catalyst in step (1) is dibutyltin dilaurate.
9. A method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, The curing agent in step (1) is an aliphatic isocyanate.
10. A method for preparing a yellowing-resistant, high-gloss topcoat for automotive interior and exterior trim according to claim 2, characterized in that, The wet film thickness of the main coating slurry in step (2) is 110-130 μm.