Mirror silver composite coating and method of making

Abstract

The application discloses a mirror silver composite coating and a preparation method thereof, and belongs to the technical field of inks.The mirror silver composite coating has a double-layer structure of a mirror silver bottom layer and a self-repairing surface layer.In the mirror silver bottom layer, non-floating aluminum silver paste provides high mirror reflection effect, and MXene material provides excellent light-heat conversion performance.The mirror silver bottom layer and the self-repairing surface layer have a synergistic effect, which not only ensures high mirror texture of the coating, but also realizes high light-heat response.The self-repairing surface layer can realize phase change, migration and recrosslinking of polymers under the action of infrared light or near-infrared light, and meanwhile, the mirror silver bottom layer does not soften and change phase during the light-heat warming process, so that the mirror effect of the bottom layer is avoided from being damaged while the surface layer is repaired.The layers are tightly combined, and have no defects such as delamination and pinholes.A weak solvent system is selected in the preparation process, and the preparation process is environmentally friendly and suitable for industrialized mass production.

Description

Technical Field

[0001] This invention relates to the field of ink technology, and in particular to a mirror silver composite coating and its preparation method. Background Technology

[0002] Mirror silver coatings, due to their excellent metallic luster and mirror reflection effect, are widely used for surface decoration and functional protection of various products, such as automotive parts, electronic device housings, optical components, and architectural decoration. With the continuous expansion of application scenarios, higher requirements are placed on the overall performance of mirror silver coatings, necessitating the maintenance of a consistently high mirror finish. However, traditional mirror silver coatings often achieve a mirror effect through the parallel orientation of aluminum silver flakes on the coating surface, which suffers from defects such as easy oxidation and blackening, poor weather resistance, and significant impact on the mirror effect after surface scratches, severely affecting appearance and service life. Summary of the Invention

[0003] The main objective of this invention is to develop a composite coating that adds an ultra-thin self-healing coating layer to the surface of a mirror silver coating. The coating surface scratches can be repaired by short-term irradiation with infrared or near-infrared light, thereby maintaining a high mirror effect of the coating for a long time.

[0004] To achieve the above objectives, the present invention proposes a mirror silver composite coating, comprising a mirror silver base layer and a self-healing surface layer stacked sequentially from bottom to top, wherein the mirror silver base layer is made of mirror silver base layer ink and the self-healing surface layer is made of self-healing surface layer ink; The mirror silver undercoat ink comprises the following raw materials in parts by weight: Non-floating aluminum silver paste: 5-6 parts; MXene dispersion: 25-35 parts; hydroxyl acrylic resin: 60-80 parts; blocked isocyanate curing agent: 3-6 parts; polyether-modified polysiloxane: 1-2 parts; polyamide wax anti-settling agent: 1-2 parts; dispersant: 1-2 parts; solvent: 20-30 parts; The self-healing topcoat ink comprises an aqueous polymer matrix containing dynamic reversible covalent bonds.

[0005] By adopting the above technical solution, the mirror silver composite coating of the present invention adopts a two-layer structure of "mirror silver base layer + self-healing top layer". In the mirror silver base layer, the non-floating aluminum silver paste provides a high mirror reflection effect, and the MXene dispersion provides excellent photothermal conversion performance. The two work together to ensure the high mirror texture of the coating and achieve high photothermal response. It can be rapidly heated to 50℃~60℃ to trigger the self-healing function of the self-healing top layer. The high Tg value hydroxyl acrylic resin is used as the matrix to ensure that the base layer does not undergo phase change softening during photothermal heating, firmly fixes the orientation structure of the aluminum silver paste and MXene sheets, and avoids damage to the mirror effect.

[0006] Furthermore, the preparation method of the MXene dispersion includes the following steps: MXene material was dispersed in anhydrous ethanol, stearic acid was added, the temperature was raised to 60℃~65℃, and the reaction was stirred for 12h~24h. The precipitate was collected by centrifugation and washed, and then redispersed in a weakly polar solvent to prepare a 10wt%~20wt% MXene dispersion.

[0007] It should be noted that the MXene dispersion is modified by hydrophobic stearic acid, which can effectively prevent MXene from agglomerating in the resin matrix material. At the same time, the modified MXene can synergistically align with the non-floating aluminum silver paste, further improving the mirror effect and photothermal efficiency of the coating.

[0008] Furthermore, the MXene flakes in the MXene dispersion have a diameter of 200nm to 500nm. MXene flakes within this size range can work synergistically with non-floating aluminum silver paste to achieve uniform dispersion and directional arrangement in the coating, ensuring high photothermal conversion efficiency without compromising the mirror effect due to excessively large flake diameters.

[0009] Furthermore, the Tg value of the hydroxyl acrylic resin is not lower than 60°C. Using a hydroxyl acrylic resin with a high Tg value ensures that the mirror silver substrate remains in a glassy state during photothermal heating (50°C~60°C), preventing phase transformation and softening, firmly fixing the oriented structure of the non-floating aluminum silver paste and MXene sheets, and avoiding damage to the mirror effect.

[0010] Furthermore, the solvent comprises butyl acetate and PMA in a weight ratio of (5~8):(2~3). This compounded weak solvent system has a suitable evaporation rate, which ensures that the mirror silver underlayer ink flows slowly during the coating process, allowing the non-floating aluminum silver paste and MXene flakes to be fully oriented. At the same time, it avoids defects such as pinholes and edge shrinkage caused by excessively rapid solvent evaporation. Moreover, it has good compatibility with hydroxyl acrylic resin and MXene dispersion, and does not affect the coating curing effect.

[0011] Furthermore, the self-healing surface ink comprises the following raw materials in parts by weight: Waterborne polyurethane: 60-100 parts; Polycaprolactone: 20-30 parts; Hydroxyl-terminated polydimethylsiloxane modified polyurethane: 6-12 parts; Organic solvent: 60-100 parts; The disulfide bond content in the waterborne polyurethane is 0.3 mmol / g to 0.5 mmol / g.

[0012] Waterborne polyurethane containing disulfide bonds serves as the main component of the self-healing surface layer. As a dynamic and reversible covalent bond, the disulfide bond can undergo reversible breakage and reconstruction under photothermal heating, achieving self-healing of scratches. Polycaprolactone, as a temperature-sensitive polymer, undergoes a chain segment relaxation phase transition at 45℃~50℃, reducing the viscosity of the system, assisting molecular chain slippage and leveling, and shortening the self-healing time. Hydroxyl-terminated polydimethylsiloxane-modified polyurethane can improve the flexibility of the self-healing surface layer and promote the leveling effect of the repaired surface layer, thereby giving the repaired coating a good mirror effect.

[0013] Furthermore, the dry film thickness of the mirror silver underlayer is 10μm~15μm; and / or, the dry film thickness of the self-healing surface layer is 1μm~5μm. Controlling this thickness range in the mirror silver underlayer ensures that the non-floating aluminum silver paste and MXene sheets are fully oriented to form a uniform and dense mirror reflection layer; controlling this ultra-thin thickness in the self-healing surface layer avoids affecting the mirror effect, while ensuring that photothermal heat can be quickly conducted to the surface layer to trigger the self-healing function, and also has good adhesion to the underlayer.

[0014] The present invention also provides a method for preparing the above-mentioned mirror silver composite coating, comprising the following steps: S1. Disperse non-floating aluminum silver paste in a portion of the solvent to obtain an aluminum silver paste dispersion; mix and stir hydroxy acrylic resin and the remaining solvent, slowly add a blocked isocyanate curing agent, stir, add a dispersant and a polyamide wax anti-settling agent, stir, add the aluminum silver paste dispersion, stir, add MXene dispersion and polyether-modified polysiloxane, stir, allow to stand to degas, filter, and obtain a mirror silver underlayer ink; S2. Take all the organic solvent and add it to polycaprolactone in batches, stir until completely dissolved, then slowly dissolve the water-based polyurethane, stir until completely dissolved, add hydroxyl-terminated polydimethylsiloxane-modified polyurethane dropwise, stir, let stand to degas, filter, and obtain the self-healing surface ink. S3. Using the mirror silver base layer ink obtained in step S1, a wet film is coated, and pre-curing and high-temperature curing are performed sequentially to obtain a mirror silver base layer. Then, the self-healing top layer ink is spin-coated onto the surface of the mirror silver base layer, evaporated at room temperature, and then vacuum dried to obtain a self-healing top layer, thus completing the preparation of the mirror silver composite coating.

[0015] Furthermore, in step S3, pre-curing is performed at 50℃~65℃ for 20min~30min, followed by curing at 130℃~135℃ for 20min~30min. Pre-curing allows for slow solvent evaporation, ensuring the non-floating aluminum silver paste and MXene layers are fully oriented and avoiding rapid solvent evaporation during high-temperature curing, which could damage the coating structure. High-temperature curing allows for full cross-linking of the hydroxyl acrylic resin and the blocked isocyanate curing agent, forming a dense and stable mirror silver underlayer, thus improving the coating's hardness and weather resistance.

[0016] Further, in step S3, the room temperature evaporation time is 40-50 minutes; and / or, the vacuum drying temperature is 50°C-55°C, and the vacuum drying time is 10-15 hours. Room temperature evaporation allows the organic solvents in the self-healing topcoat ink to initially evaporate, avoiding the rapid evaporation of solvents and the generation of bubbles during vacuum drying; vacuum drying can completely remove residual solvents from the topcoat, ensuring complete curing of the self-healing topcoat and improving its self-healing performance and adhesion to the substrate.

[0017] The mirror silver composite coating of this invention adopts a double-layer structure of a mirror silver base layer and a self-healing top layer. In the mirror silver base layer, non-floating aluminum silver paste provides a high mirror reflection effect, and MXene material provides excellent photothermal conversion performance. The mirror silver base layer and the self-healing top layer have a synergistic effect, which not only ensures the high mirror texture of the coating, but also achieves high photothermal response. Under the action of infrared or near-infrared light, the self-healing top layer can realize the phase change, migration and re-crosslinking of polymers. At the same time, the mirror silver base layer does not undergo phase change softening during photothermal heating, thereby repairing the top layer while avoiding damage to the mirror effect of the base layer.

[0018] The preparation method of this invention is simple and highly operable. By preparing the base layer and top layer inks in steps and strictly controlling the coating and curing parameters, it ensures that the components of the coating are uniformly dispersed and oriented, with tight interlayer bonding and no defects such as delamination or pinholes. The preparation process uses a weak solvent system, which is environmentally friendly and suitable for industrial mass production. Detailed Implementation

[0019] 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 a part of the embodiments of the present invention, and not all of the 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.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] The technical solution of the present invention will be further described below through specific embodiments.

[0023] In the following examples, all raw materials used are commercially available conventional raw materials, wherein: The non-floating aluminum silver paste used was a commercially available sheet-type non-floating aluminum silver paste with a sheet diameter of 1μm~5μm; the hydroxyl acrylic resin used was a thermosetting hydroxyl acrylic resin with a Tg value of 65℃; the dispersant used was BYK-164 low polarity dispersant; the waterborne polyurethane used was a waterborne polyurethane containing disulfide bonds (disulfide bond content 0.4mmol / g); the polycaprolactone used was polycaprolactone with Mn=1500; the hydroxyl-terminated polydimethylsiloxane modified polyurethane used was a commercially available product; the solvents used were butyl acetate and PMA (analytical grade).

[0024] Example 1 The preparation process of the MXene dispersion in Example 1 is as follows: MXene material (particle size 200~500nm) was dispersed in anhydrous ethanol, stearic acid was added, the temperature was raised to 60℃, and the reaction was stirred for 24h. The precipitate was collected by centrifugation, washed three times with anhydrous ethanol, and redispersed in butyl acetate to prepare a 10wt% MXene dispersion.

[0025] The raw materials for the mirror silver underlayer ink in Example 1 include: 5 parts of non-floating aluminum silver paste, 25 parts of MXene dispersion, 60 parts of hydroxyl acrylic resin, 3 parts of blocked isocyanate curing agent, 1 part of polyether modified polysiloxane, 1 part of polyamide wax anti-settling agent, 1 part of dispersant, and 20 parts of solvent (butyl acetate: PMA = 5:2).

[0026] The preparation process of the mirror silver underlayer ink in Example 1 is as follows: Non-floating aluminum silver paste was dispersed in 10 parts of solvent and stirred for 30 minutes to obtain an aluminum silver paste dispersion. Hydroxy acrylic resin and the remaining 10 parts of solvent were mixed and stirred for 15 minutes. Blocked isocyanate curing agent was slowly added and stirred for another 20 minutes. Dispersant and polyamide wax anti-settling agent were added and stirred for 15 minutes. Aluminum silver paste dispersion was added and stirred for 20 minutes. MXene dispersion and polyether modified polysiloxane were added and stirred at low speed for 30 minutes. The mixture was allowed to stand for degassing for 20 minutes and then filtered through a 150-mesh filter to obtain a mirror silver underlayer ink.

[0027] The raw materials for the self-healing topcoat ink in Example 1 include: The composition includes 60 parts of waterborne polyurethane, 20 parts of polycaprolactone, 6 parts of hydroxyl-terminated polydimethylsiloxane-modified polyurethane, and 60 parts of organic solvent (tetrahydrofuran).

[0028] The preparation process of the self-healing topcoat ink in Example 1 is as follows: Add all the organic solvent in batches to polycaprolactone and stir until completely dissolved. Then slowly add water-based polyurethane and stir until completely dissolved. Add hydroxyl-terminated polydimethylsiloxane-modified polyurethane dropwise, stir at low speed for 25 minutes, let stand to degas for 20 minutes, and filter with a 200-mesh filter to obtain the self-healing surface ink.

[0029] The preparation process of the mirror silver composite coating in Example 1 is as follows: The prepared mirror silver underlayer ink was diluted with solvent to a solid content of about 50 wt%, and then sprayed onto the substrate surface to form a wet film. It was pre-cured at 50°C for 30 min, and then cured at 130°C for 30 min to obtain a mirror silver underlayer with a dry film thickness of 10 μm. A self-healing toplayer ink was spin-coated onto the surface of the mirror silver underlayer, evaporated at room temperature for 40 min, and then vacuum dried at 50°C for 15 h to obtain a self-healing toplayer with a dry film thickness of 1 μm, thus completing the preparation of the composite coating.

[0030] Example 2 The MXene dispersion in Example 2 is the same as in Example 1.

[0031] The raw materials for the mirror silver underlayer ink in Example 2 include: 5.5 parts of non-floating aluminum silver paste, 30 parts of MXene dispersion, 70 parts of hydroxyl acrylic resin, 4.5 parts of blocked isocyanate curing agent, 1.5 parts of polyether modified polysiloxane, 1 part of polyamide wax anti-settling agent, 1 part of dispersant, and 20 parts of solvent (butyl acetate: PMA = 5:2).

[0032] The raw materials for the self-healing topcoat ink in Example 2 include: 80 parts of waterborne polyurethane, 20 parts of polycaprolactone, 9 parts of hydroxyl-terminated polydimethylsiloxane-modified polyurethane, and 60 parts of organic solvent (tetrahydrofuran).

[0033] The preparation process of the mirror silver base ink and the self-healing top ink in Example 2 is the same as that in Example 1.

[0034] The preparation process of the mirror silver composite coating in Example 2 is as follows: The prepared mirror silver underlayer ink was diluted with solvent to a solid content of about 50 wt%, and then sprayed onto the substrate surface to form a wet film. It was pre-cured at 50°C for 30 min, and then cured at 130°C for 30 min to obtain a mirror silver underlayer with a dry film thickness of 10 μm. A self-healing toplayer ink was spin-coated onto the surface of the mirror silver underlayer, evaporated at room temperature for 40 min, and then vacuum dried at 50°C for 15 h to obtain a self-healing toplayer with a dry film thickness of 1 μm, thus completing the preparation of the composite coating.

[0035] Example 3 The MXene dispersion in Example 3 is the same as in Example 1.

[0036] The raw materials for the mirror silver underlayer ink in Example 3 include: 6 parts of non-floating aluminum silver paste, 35 parts of MXene dispersion, 70 parts of hydroxyl acrylic resin, 4.5 parts of blocked isocyanate curing agent, 2 parts of polyether modified polysiloxane, 1 part of polyamide wax anti-settling agent, 1 part of dispersant, and 20 parts of solvent (butyl acetate: PMA = 5:2).

[0037] The raw materials for the self-healing topcoat ink in Example 3 include: 80 parts of waterborne polyurethane, 30 parts of polycaprolactone, 9 parts of hydroxyl-terminated polydimethylsiloxane-modified polyurethane, and 60 parts of organic solvent (tetrahydrofuran).

[0038] The preparation process of the mirror silver base ink and the self-healing top ink in Example 3 is the same as that in Example 1.

[0039] The preparation process of the mirror silver composite coating in Example 3 is as follows: The prepared mirror silver underlayer ink was diluted with solvent to a solid content of about 50 wt%, and then sprayed onto the substrate surface to form a wet film. It was pre-cured at 60°C for 20 min, and then cured at 135°C for 20 min to obtain a mirror silver underlayer with a dry film thickness of about 10 μm. A self-healing toplayer ink was spin-coated onto the surface of the mirror silver underlayer, evaporated at room temperature for 40 min, and then vacuum dried at 50°C for 15 h to obtain a self-healing toplayer with a dry film thickness of about 1 μm, thus completing the preparation of the composite coating.

[0040] Comparative Example 1 Comparative Example 1 is based on Example 2, except that MXene dispersion was not added to the raw materials of the mirror silver underlayer ink in Comparative Example 1.

[0041] Comparative Example 2 Comparative Example 2 is based on Example 2, except that the hydroxyl acrylic resin in the raw material of the mirror silver underlayer ink in Comparative Example 2 is replaced with a hydroxyl acrylic resin with a Tg of about 50°C.

[0042] Comparative Example 3 Comparative Example 3 is based on Example 2, except that polycaprolactone was not added to the raw materials of the self-healing topcoat ink in Comparative Example 3.

[0043] Performance testing: The performance of the mirror silver composite coatings prepared in Examples 1-3 above was tested. The test items and results are shown in Table 1. Table 1

[0044] As can be seen from the above test results, the mirror silver composite coating prepared in Examples 1 to 3 of the present invention has high mirror gloss, fast photothermal heating rate, high self-healing efficiency, excellent interlayer adhesion, and good weather resistance, which fully meets the needs of practical applications and solves the technical bottleneck of existing mirror silver coatings.

[0045] The above embodiments are compared with the comparative examples: The mirror gloss of the mirror silver composite coating in Comparative Example 1 is 95, the photothermal heating rate is 0.8℃ / min, and the self-healing efficiency of a 1μm scratch at 60℃ is only 45%, indicating that the addition of MXene dispersion can significantly improve the photothermal effect and self-healing efficiency of the coating without affecting the mirror effect.

[0046] In Comparative Example 2, the mirror silver composite coating softened under 60°C photothermal irradiation, the mirror gloss level dropped to 72, and obvious haze appeared. This indicates that the high Tg value of the hydroxyl acrylic resin can effectively prevent the phase change of the underlying layer during photothermal heating and protect the mirror structure.

[0047] The self-healing efficiency of the 1μm scratch on the mirror silver composite coating in Comparative Example 3 at 60℃ was 68%, indicating that polycaprolactone can effectively assist the self-healing process, shorten the self-healing time, and improve the self-healing efficiency.

[0048] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A mirror silver composite coating, characterized in that, The mirror silver composite coating comprises a mirror silver base layer and a self-healing surface layer stacked sequentially from bottom to top. The mirror silver base layer is made of mirror silver base layer ink, and the self-healing surface layer is made of self-healing surface layer ink. The mirror silver undercoat ink comprises the following raw materials in parts by weight: Non-floating aluminum silver paste: 5-6 parts; MXene dispersion: 25-35 parts; hydroxyl acrylic resin: 60-80 parts; blocked isocyanate curing agent: 3-6 parts; polyether-modified polysiloxane: 1-2 parts; polyamide wax anti-settling agent: 1-2 parts; dispersant: 1-2 parts; solvent: 20-30 parts; The self-healing topcoat ink comprises an aqueous polymer matrix containing dynamic reversible covalent bonds.

2. The mirror silver composite coating as described in claim 1, characterized in that, The MXene dispersion was prepared by the following steps: MXene material was dispersed in anhydrous ethanol, stearic acid was added, the temperature was raised to 60℃~65℃, and the reaction was stirred for 12h~24h. The precipitate was collected by centrifugation and washed, and then redispersed in a weakly polar solvent to prepare a 10wt%~20wt% MXene dispersion.

3. The mirror silver composite coating as described in claim 1, characterized in that, The MXene flakes in the MXene dispersion have a diameter of 200 nm to 500 nm.

4. The mirror silver composite coating as described in claim 1, characterized in that, The hydroxy acrylic resin T g The value should not be lower than 60℃.

5. The mirror silver composite coating as described in claim 1, characterized in that, The solvent comprises butyl acetate and PMA in a weight ratio of (5~8):(2~3).

6. The mirror silver composite coating as described in claim 1, characterized in that, The self-healing topcoat ink comprises the following raw materials in parts by weight: Waterborne polyurethane: 60-100 parts; Polycaprolactone: 20-30 parts; Hydroxyl-terminated polydimethylsiloxane modified polyurethane: 6 parts to 12 parts; Organic solvent: 60-100 parts; The disulfide bond content in the waterborne polyurethane is 0.3 mmol / g to 0.5 mmol / g.

7. The mirror silver composite coating as described in claim 1, characterized in that, The dry film thickness of the mirror silver substrate is 10μm~15μm; And / or, the dry film thickness of the self-healing surface layer is 1μm~5μm.

8. A method for preparing a mirror silver composite coating according to any one of claims 1 to 7, characterized in that, The preparation method of the mirror silver composite coating includes the following steps: S1. Disperse non-floating aluminum silver paste in a portion of the solvent to obtain an aluminum silver paste dispersion; mix and stir hydroxy acrylic resin and the remaining solvent, slowly add a blocked isocyanate curing agent, stir, add a dispersant and a polyamide wax anti-settling agent, stir, add the aluminum silver paste dispersion, stir, add MXene dispersion and polyether-modified polysiloxane, stir, allow to stand to degas, filter, and obtain a mirror silver underlayer ink; S2. Take all the organic solvent and add it to polycaprolactone in batches, stir until completely dissolved, then slowly dissolve the water-based polyurethane, stir until completely dissolved, add hydroxyl-terminated polydimethylsiloxane-modified polyurethane dropwise, stir, let stand to degas, filter, and obtain the self-healing surface ink. S3. Using the mirror silver base layer ink obtained in step S1, a wet film is coated, and pre-curing and high-temperature curing are performed sequentially to obtain a mirror silver base layer. Then, the self-healing top layer ink is spin-coated onto the surface of the mirror silver base layer, evaporated at room temperature, and then vacuum dried to obtain a self-healing top layer, thus completing the preparation of the mirror silver composite coating.

9. The method for preparing the mirror silver composite coating as described in claim 8, characterized in that, In step S3, the material is pre-cured at 50℃~65℃ for 20min~30min, and then cured at 130℃~135℃ for 20min~30min.

10. The method for preparing the mirror silver composite coating as described in claim 8, characterized in that, In step S3, the room temperature evaporation time is 40 min to 50 min; And / or, the vacuum drying temperature is 50℃~55℃, and the vacuum drying time is 10h~15h.

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