Self-drying mirror back coating and preparation method thereof

Abstract

The invention discloses a self-drying mirror back coating and a preparation method thereof, and belongs to the technical field of protective coatings. The coating comprises the following components in parts by weight: 30-35 parts of acrylic acid modified alkyd resin, 8-12 parts of a solvent, 1-7 parts of an anti-settling agent, 12-15 parts of talcum powder, 3 parts of a coloring agent, 2 parts of a corrosion inhibitor, 0.5-35.5 parts of heavy calcium carbonate and 20 parts of barium sulfate. By controlling the color-base ratio in a range of 2.5-3.0, the coating can realize surface drying for 3-4 minutes and hard drying for 12 hours at 25 DEG C, the drying speed is high, and the process is stable; the anti-sagging property is obviously improved, the construction viscosity is controllable, and the leveling property is good; meanwhile, the VOC content is low, the raw material cost is controllable, and the environment-friendly property and the economical efficiency are achieved. A coating layer formed by the coating is excellent in adhesive force and lasting in protective performance, has good toughness, impact resistance and scratch resistance, and can effectively prolong the service life of a mirror back.

Description

Technical Field

[0001] This invention relates to the field of protective coating technology, specifically to a self-drying mirror-back coating and its preparation method. Background Technology

[0002] With technological advancements and improved living standards, people are increasingly demanding higher performance from everyday consumer goods. As a crucial component of home decoration, glass mirrors are receiving significant attention for their surface gloss and long-term weather resistance. A typical mirror consists of a glass substrate, a chemically deposited metallic reflective layer (such as silver or aluminum), and an outer protective coating. The metallic reflective layer is chemically reactive and easily reacts with moisture and hydrogen sulfide in the air, leading to defects such as black spots, fogging, and reduced reflectivity, severely impacting the mirror's appearance and lifespan. Especially in humid environments with frequent contact with cleaning agents (such as bathroom vanity mirrors), mirrors are more prone to coating corrosion and peeling, affecting not only the user experience but also increasing replacement and maintenance costs. Therefore, improving the protective performance of the mirror's back and developing protective coatings with excellent overall performance are of significant practical importance for extending mirror lifespan and enhancing reliability.

[0003] Most of the protective coatings for mirror backs currently available on the market are based on traditional processes and materials, and they have revealed the following major defects during long-term use: Insufficient adhesion: The coating has weak adhesion to the glass substrate or metal plating, and is prone to local or overall peeling.

[0004] Poor density: The coating has limited barrier properties and cannot effectively prevent the penetration of water vapor, oxygen and corrosive ions.

[0005] Poor mechanical properties: The coating has weak hardness, wear resistance and impact resistance, and is easily damaged during transportation, installation and daily use.

[0006] Poor weather resistance: It is prone to powdering, cracking, and aging in environments such as humid heat, hot and cold cycles, and ultraviolet radiation.

[0007] Insufficient environmental friendliness: Some coatings contain high levels of volatile organic compounds (VOCs), which may have potential impacts on the environment and human health.

[0008] These shortcomings result in limited protective effects of mirrors in harsh environments, making it difficult to meet people's demand for high-performance, long-life mirrors.

[0009] To address the shortcomings of existing protective coatings for mirror backs, future research should focus on developing a novel, multifunctional, high-performance, and environmentally friendly protective coating system. The focus should be on the following aspects: Enhanced adhesion: Improve the bonding strength between the coating and the substrate through molecular structure design or surface treatment technology.

[0010] Improved density and barrier properties: Construct a denser coating structure to effectively block the penetration of water vapor and corrosive media.

[0011] Improve mechanical properties and weather resistance: Introduce scratch-resistant and impact-resistant components, and enhance the coating's resistance to environments such as humid heat, ultraviolet radiation, and thermal cycling.

[0012] Promoting energy conservation and environmental protection: Developing low-VOC or self-drying systems aligns with the trend of energy conservation and environmental protection.

[0013] Balancing construction and economy: While ensuring performance, optimize the construction adaptability of coatings and control costs to promote their industrial application.

[0014] Therefore, there is an urgent need to develop a self-drying coating suitable for mirror back protection that has strong adhesion, excellent water and salt spray resistance, high mechanical strength, convenient construction, and low cost, so as to achieve long-term protection of the metal reflective layer and significantly extend the service life of the mirror. Summary of the Invention

[0015] Therefore, the present invention provides a self-drying mirror back coating and its preparation method to overcome the shortcomings of the prior art.

[0016] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a self-drying mirror back coating is provided, comprising, by weight, the following components: Acrylic-modified alkyd resin: 30-35 parts; Solvent: 8-12 parts; Anti-settling agent: 1-7 parts; Talc powder: 12-15 parts; Colorant: 3 parts; Corrosion inhibitor: 2 parts; Heavy calcium carbonate: 0.5-35.5 parts; Barium sulfate: 20 parts.

[0017] Furthermore, the acrylic-modified alkyd resin is obtained by graft copolymerization of short-oil alkyd resin and acrylic monomers accounting for 55 wt.% of the total mass of short-oil alkyd resin, wherein the acrylic monomers are selected from at least one of methyl methacrylate (MMA), acrylic acid (AA), butyl acrylate (BA), butyl methacrylate (BMA), hydroxyethyl methacrylate (HEMA), and hydroxyethyl acrylate (HEA). The preparation method of the acrylic-modified alkyd resin is as follows: Short-oil alkyd resin, xylene, and initiator are mixed until the system is homogeneous. The mixture is heated to 110-130℃ under nitrogen protection at a constant rate, and acrylic monomers are added dropwise at a constant rate at this temperature, with the addition time controlled within 2.5-4 hours. After the addition is completed, the reaction is kept at the temperature for 1-2 hours to ensure that the reaction is complete, and acrylic modified alkyd resin is obtained. The amount of the initiator added is 1 wt.%-3 wt.% of the total mass of acrylic monomers, the solid content of the acrylic modified alkyd resin is 55%, and the initiator includes, but is not limited to, benzoyl peroxide (BPO).

[0018] Furthermore, the anti-settling agent is selected from at least one of fumed silica, organobentonite, and polyamide wax, used to improve the thixotropy of the coating system and prevent storage sedimentation; the colorant is selected from at least one of titanium dioxide (such as titanium dioxide, to improve the board surface coverage) and zinc barium white (such as lithopone); the corrosion inhibitor is selected from at least one of phosphates (such as aluminum tripolyphosphate, zinc phosphate, etc.), quaternary phosphates, and metal oxides (such as zinc oxide, etc.).

[0019] Furthermore, the solvent is xylene, which is used to adjust the viscosity of the coating, and its rapid volatility helps to improve the natural drying performance of the coating.

[0020] Furthermore, the barium sulfate includes, but is not limited to, natural barium sulfate, used to improve the hardness, wear resistance, and durability of the coating.

[0021] According to a second aspect of the present invention, a method for preparing a self-drying mirror back coating is provided, comprising the following steps: After mixing acrylic-modified alkyd resin and a portion of solvent in a certain proportion, the mixture is stirred thoroughly until homogeneous. Then, anti-settling agent, talc, colorant, corrosion inhibitor, heavy calcium carbonate, and barium sulfate are added sequentially, and the mixture is stirred until homogeneous to obtain a mixture. The mixture is then fully dispersed under high-frequency stirring for 1-3 hours until the fineness reaches ≤25μm. After dispersion, the remaining solvent is added to adjust the viscosity. Finally, the mixture is ground and filtered to obtain a self-drying mirror back coating.

[0022] Furthermore, the viscosity is 180-220 s (Ford-4 cup, 25°C).

[0023] Furthermore, the parameters for the high-frequency stirring are: rotation speed 3000 r / min, time 1-2 h.

[0024] According to a third aspect of the present invention, a self-drying mirror back coating prepared by the aforementioned method is provided for coating the back of an aluminum mirror or a silver mirror.

[0025] According to a fourth aspect of the invention, a coating is provided, formed from the self-drying mirror-back coating.

[0026] Furthermore, its dry film thickness is 20-50 μm.

[0027] Compared with the prior art, the present invention has the following advantages: (1) Excellent process performance: By controlling the specific resin system and pigment / filler ratio, the self-drying mirror-back coating of this invention can rapidly cure into a film at room temperature (25℃). Tests show that when the pigment-to-binder ratio is controlled within the range of 2.5-3.0, the coating can stably achieve surface drying in 3-4 minutes and complete drying in 12 hours, with a drying efficiency significantly higher than traditional mirror-back coatings. Furthermore, the process is stable and suitable for automated continuous production lines. Simultaneously, when the pigment-to-binder ratio reaches 3.0 or higher, the coating's anti-sagging properties are significantly improved, the application viscosity (35s viscosity) is controllable, and the leveling properties are good, making it suitable for automated processes such as roller coating and curtain coating. Its storage stability continuously improves with increasing pigment-to-binder ratio, effectively avoiding sagging and sedimentation, facilitating actual construction and storage.

[0028] (2) Strong adhesion and long-lasting protection: Thanks to the synergistic effect of the resin system and adhesion promoter, the self-drying mirror back coating of this invention exhibits excellent adhesion to both glass substrates and metal coatings. When the pigment-to-binder ratio is controlled within the range of 2.0-2.5, the adhesion test using a cross-cut adhesion test achieves grade 0 (no peeling), significantly better than grade 1 (slight peeling at the edges) of traditional mirror back coatings. Its pull-out adhesion reaches 1.5 MPa, with a strong bond, significantly better than the 1.0 MPa of traditional mirror back coatings. Simultaneously, within this pigment-to-binder ratio range, the coating forms a dense physical barrier layer, effectively blocking the penetration of corrosive media. After 720 hours of natural aging at room temperature, the physical and mechanical properties retain >90%, with no chalking or cracking, providing reliable long-term protection for the mirror back. Notably, even when the pigment-to-binder ratio increases to 3.0, the coating still forms a dense physical barrier layer, with a salt spray resistance time >700 hours, demonstrating excellent protective durability.

[0029] (3) Excellent mechanical properties and durability: The self-drying mirror back coating of this invention achieves a pencil hardness of 3H, higher than the 2H of traditional mirror back coatings, while also possessing good toughness. This endows the coating with better impact resistance and scratch resistance, effectively protecting the mirror from physical damage during subsequent processing, transportation, and installation, thereby extending the service life of the mirror back.

[0030] (4) Outstanding environmental friendliness and economic efficiency: Under the same pigment-to-binder ratio, the VOC content of the self-drying mirror-back coating of this invention is 291-321 g·L⁻¹. -1 The levels are generally lower than those of traditional mirror back coatings (329-363 g / L). -1This makes it easier to meet stringent environmental regulations. Furthermore, the raw materials used in this coating system are widely available and cost-controllable, giving it good applicability to industrial production and market competitiveness.

[0031] Based on the comprehensive performance test results, when the pigment-to-binder ratio is controlled within the range of 2.5-3.0, the self-drying mirror-back coating of this invention achieves an excellent overall balance in key indicators such as drying performance, adhesion, salt spray resistance, hardness, application performance, and environmental friendliness, thereby effectively unifying fast drying, high adhesion, long-lasting protection, and economical application. Attached Figure Description

[0032] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0033] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0034] Figure 1 This is a schematic diagram of the coating of the self-drying mirror back coating on a standard aluminized glass specimen in Embodiment 1 of the present invention; Figure 2 The graphs show the surface drying time of the self-drying mirror-back coatings in Examples 1-7 and the conventional mirror-back coatings in Comparative Examples 1-7 at different pigment-to-binder ratios (2.0-5.0). Figure 3 The graph shows the relationship between the sedimentation rate (100g sample, 24h) and the sag value (35s viscosity) of the self-drying mirror back coatings in Examples 1-5 of the present invention at different pigment-to-binder ratios (2.0-5.0). Figure 4 The figures show the results of neutral salt spray tests on the self-drying mirror-back coatings in Examples 1-5 of this invention at different pigment-to-binder ratios (2.0-5.0). Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0036] According to a first aspect of the present invention, a self-drying mirror back coating is provided, comprising, by weight, the following components: Acrylic-modified alkyd resin: 30-35 parts; Solvent: 8-12 parts; Anti-settling agent: 1-7 parts; Talc powder: 12-15 parts; Colorant: 3 parts; Corrosion inhibitor: 2 parts; Heavy calcium carbonate: 0.5-35.5 parts; Barium sulfate: 20 parts.

[0037] Furthermore, the acrylic modified alkyd resin is obtained by graft copolymerization of short-oil alkyd resin and acrylic monomers accounting for 55 wt.% of the total mass of short-oil alkyd resin. The acrylic monomers are selected from at least one of methyl methacrylate (MMA), acrylic acid (AA), butyl acrylate (BA), butyl methacrylate (BMA), hydroxyethyl methacrylate (HEMA), and hydroxyethyl acrylate (HEA). The preparation method of acrylic-modified alkyd resin is as follows: Short-oil alkyd resin, xylene, and initiator are mixed until the system is homogeneous. The mixture is heated to 110-130℃ under nitrogen protection at a constant rate, and acrylic monomers are added dropwise at a constant rate at this temperature, with the addition time controlled within 2.5-4 hours. After the addition is completed, the reaction is kept at the temperature for 1-2 hours to ensure that the reaction is complete, and acrylic modified alkyd resin is obtained. The amount of initiator added is 1 wt.%-3 wt.% of the total mass of acrylic monomers, and the solid content of acrylic modified alkyd resin is 55%. The initiator includes, but is not limited to, benzoyl peroxide (BPO).

[0038] Furthermore, the anti-settling agent is selected from at least one of fumed silica, organobentonite, and polyamide wax, used to improve the thixotropy of the coating system and prevent storage sedimentation; the colorant is selected from at least one of titanium dioxide (such as titanium dioxide, to provide active corrosion protection) and zinc barium white (such as lithopone); the corrosion inhibitor is selected from at least one of phosphates (such as aluminum tripolyphosphate, zinc phosphate, etc.), quaternary phosphates, and metal oxides (such as zinc oxide, etc.).

[0039] Furthermore, xylene is used as the solvent to adjust the viscosity of the coating, and its rapid volatility helps to improve the natural drying performance of the coating.

[0040] Furthermore, barium sulfate, including but not limited to natural barium sulfate, is used to improve the hardness, wear resistance, and durability of coatings.

[0041] According to a second aspect of the present invention, a method for preparing a self-drying mirror back coating is provided, comprising the following steps: After mixing acrylic-modified alkyd resin and a portion of solvent in a certain proportion, the mixture is stirred thoroughly until homogeneous. Then, anti-settling agent, talc, colorant, corrosion inhibitor, heavy calcium carbonate, and barium sulfate are added sequentially, and the mixture is stirred until homogeneous to obtain a mixture. The mixture is then fully dispersed under high-frequency stirring for 1-3 hours until the fineness reaches ≤25μm. After dispersion, the remaining solvent is added to adjust the viscosity. Finally, the mixture is ground and filtered to obtain a self-drying mirror back coating.

[0042] Furthermore, the viscosity is 180-220 s (Ford-4 cup, 25°C).

[0043] Furthermore, the parameters for high-frequency stirring are: rotation speed 3000 r / min, time 1-2 h.

[0044] According to a third aspect of the present invention, a self-drying mirror back coating prepared by a method is provided for coating the back of an aluminum mirror or a silver mirror.

[0045] According to a fourth aspect of the invention, a coating is provided, formed from a self-drying mirror-back coating.

[0046] Furthermore, its dry film thickness is 20-50 μm.

[0047] Preparation example: Under stirring conditions, 100g of short-oil alkyd resin 638B (80% solid content), 88.4g of xylene, and 1.1g of BPO were added to the reactor until the system was uniformly mixed. The mixture was heated to 120℃ under nitrogen protection, and 55g of methyl methacrylate was added dropwise at a uniform rate at this temperature, with the addition time controlled to be completed within 3 hours. After the addition was completed, the reaction was kept at the temperature for 2 hours to ensure that the reaction was complete, and an acrylic modified alkyd resin with a solid content of 55% was obtained. Example 1

[0048] Preparation of self-drying mirror back coating: Self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 35g; Xylene: 12g; Organic bentonite: 1g; Talc powder: 12g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 0.5g; Natural barium sulfate: 20g; The preparation method of self-drying mirror back coating is as follows: Add 80% xylene and the acrylic-modified alkyd resin prepared in the preparation example to a stirred tank, and stir at a constant speed until the system is homogeneous; while maintaining stirring, slowly add the following components in sequence: organobentonite, titanium dioxide, talc, heavy calcium carbonate, natural barium sulfate and zinc phosphate, and stir until the system is uniformly mixed to obtain a slurry; transfer the slurry to a zirconium bead disperser and disperse at a high speed of 3000 r / min for 2 h until the fineness reaches ≤25 μm; after dispersion, add the remaining 20% ​​xylene and adjust the viscosity to 220 s (Ford cup 4, 25°C), and after grinding and filtration, obtain a self-drying mirror back coating. Example 2

[0049] The difference between Example 2 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratio: Acrylic-modified alkyd resin: 32g; Xylene: 12g; Organic bentonite: 3g; Talc powder: 13g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 2g; Natural barium sulfate: 20g. Example 3

[0050] The difference between Example 3 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 30g; Xylene: 12g; Organic bentonite: 3g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 6.5g; Natural barium sulfate: 20g. Example 4

[0051] The difference between Example 4 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 12.75g; Natural barium sulfate: 20g. Example 5

[0052] The difference between Example 5 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 21g; Natural barium sulfate: 20g. Example 6

[0053] The difference between Example 6 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 29.25g; Natural barium sulfate: 20g. Example 7

[0054] The difference between Example 7 and Example 1 is that the self-drying mirror back coating is made from the following components in the indicated weight ratios: Acrylic-modified alkyd resin: 30g; Xylene: 12g; Organic bentonite: 7g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 35.5g; Natural barium sulfate: 20g.

[0055] Comparative Example 1: Preparation of traditional mirror back coating: Traditional mirror back coatings are made from the following components in the indicated weight ratios: Short-oil alkyd resin 638B: 35g; Xylene: 12g; Organic bentonite: 1g; Talc powder: 12g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 0.5g; Natural barium sulfate: 20g; The traditional method for preparing mirror-back coatings is as follows: Add 80% xylene and short-oil alkyd resin 638B to a mixing tank and stir at a constant speed until the system is homogeneous. While maintaining stirring, slowly add the following components in sequence: organobentonite, titanium dioxide, talc, heavy calcium carbonate, natural barium sulfate, and zinc phosphate, and stir until the system is uniformly mixed to obtain a slurry. Transfer the slurry to a zirconium bead disperser and disperse at a high speed of 3000 r / min for 2 h until the fineness reaches ≤25 μm. After dispersion, add the remaining 20% ​​xylene and adjust the viscosity to 220 s (Ford cup 4, 25°C). After grinding and filtration, obtain the traditional mirror back coating.

[0056] Comparative Example 2: The difference between Comparative Example 2 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 32g; Xylene: 12g; Organic bentonite: 3g; Talc powder: 13g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 3g; Natural barium sulfate: 20g.

[0057] Comparative Example 3: The difference between Comparative Example 3 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 30g; Xylene: 12g; Organic bentonite: 3g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 6.5g; Natural barium sulfate: 20g.

[0058] Comparative Example 4: The difference between Comparative Example 4 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 12.75g; Natural barium sulfate: 20g.

[0059] Comparative Example 5: The difference between Comparative Example 5 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 21g; Natural barium sulfate: 20g.

[0060] Comparative Example 6: The difference between Comparative Example 6 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 30g; Xylene: 12g; Organic bentonite: 5g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 29.25g; Natural barium sulfate: 20g.

[0061] Comparative Example 7: The difference between Comparative Example 7 and Comparative Example 1 is that the traditional mirror back coating is made from the following components in the indicated weight ratio: Short-oil alkyd resin 638B: 30g; Xylene: 12g; Organic bentonite: 7g; Talc powder: 15g; Titanium dioxide: 3g; Zinc phosphate: 2g; Heavy calcium carbonate: 35.5g; Natural barium sulfate: 20g.

[0062] Test example: Comprehensive performance evaluation of self-drying mirror-back coatings: 1. Coating preparation: The coating was applied evenly to a standard aluminized glass specimen using a scraping method (see coating effect). Figure 1 The wet film thickness was kept consistent (30±1μm). The coated specimens were then cured at room temperature (25℃) for 24 hours to form a coating, resulting in coated specimens. Four parallel samples were set up for each group.

[0063] 2. Test Items and Result Analysis: 2.1 Drying performance and environmental friendliness: To systematically evaluate the performance of the self-drying mirror-back coating of this invention, the surface drying time and actual drying time of the self-drying mirror-back coatings in Examples 1-7 and the traditional mirror-back coatings in Comparative Examples 1-7 were tested according to GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film"; the VOC content during application was tested according to GB / T 23985-2009 "Determination of Volatile Organic Compound (VOC) Content in Paints and Varnishes - Difference Method". See Table 1 for the results. Figure 2 As shown.

[0064] Table 1 below shows the drying time test results of the self-drying mirror back coatings in Examples 1-7 and the conventional mirror back coatings in Comparative Examples 1-7: Table 1

[0065] Note: Drying time and VOC content during application are the average values ​​of 4 parallel samples; pigment-to-binder ratio = total solids / (total resin × resin solids content), and the resin solids content is 55%.

[0066] From the above table 1 and Figure 2 It can be seen that the surface drying time of both the self-drying mirror-back coating of the present invention (Examples 1-7) and the conventional mirror-back coating (Comparative Examples 1-7) is significantly shortened with the increase of the pigment-to-binder ratio, that is, the drying speed is accelerated. It is worth noting that, under the same pigment-to-binder ratio, the surface drying and complete drying times of the self-drying mirror-back coating of the present invention (Examples 1-7) are shorter than those of the conventional mirror-back coating (Comparative Examples 1-7). When the pigment-to-binder ratio is controlled within the range of 2.5-3.0, the self-drying mirror-back coating of the present invention (Examples 2 and 3) can achieve rapid surface drying in 3-4 minutes and complete drying in 12 hours, exhibiting excellent and stable drying performance.

[0067] Meanwhile, the VOC content of the self-drying mirror-back coating of this invention is 279-321 g·L⁻¹. -1 The levels were all lower than those of traditional mirror-back coatings under the same pigment-to-binder ratio conditions (329-363 g·L). -1It exhibits excellent environmental performance.

[0068] 2.2 Construction performance and salt spray resistance Based on the surface drying time test results in 2.1, the following performance tests were conducted on the self-drying mirror-back coating samples from Examples 1-5: Application performance: Tested in accordance with GB / T 9264-2012 "Evaluation of Sagging Resistance of Paints and Varnishes"; Salt spray resistance: Tested in accordance with GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes".

[0069] Depend on Figure 3 and Figure 4 It can be seen that the key performance of the self-drying mirror-back coating of the present invention is closely related to the pigment-to-binder ratio.

[0070] Figure 3 The results show that the storage stability (characterized by sedimentation rate) and anti-sagging properties of the coating system are significantly improved with the increase of pigment-to-binder ratio. When the pigment-to-binder ratio reaches 3.0, its application performance is excellent, specifically: sedimentation rate <10% in 24h and sagging value (viscosity in 35s) can reach 125μm.

[0071] Figure 4 The results show that the salt spray resistance of the coating decreases with increasing pigment-to-binder ratio. Notably, when the pigment-to-binder ratio is controlled within the range of 2.5-3.0, the coating can still form a dense physical barrier layer with a salt spray resistance time >700 hours, exhibiting excellent protective performance. However, when the pigment-to-binder ratio exceeds 3.0, its salt spray resistance decreases more significantly.

[0072] 2.3 Comparison of other key performance indicators The following performance tests were further conducted on the coatings of the self-drying mirror back coatings in Examples 1-5 and the conventional mirror back coatings in Comparative Examples 1-5: Adhesion: Cross-cut adhesion (1cm) 2 Within the specified range, the cross-cut adhesion test (100 grids) is conducted according to GB / T 9286-2021 "Cross-cut test for paints and varnishes"; the pull-out adhesion test is conducted according to GB / T 5210-2006 "Pull-off adhesion test for paints and varnishes". Pencil hardness: Tested according to GB / T 6739-2006 "Determination of Hardness of Paints and Varnishes by Pencil Method"; Weather resistance: After the coated test piece is placed in a natural environment at room temperature for 720 hours, observe whether it exhibits phenomena such as powdering or cracking, and test the retention rate of its key physical and mechanical properties (such as adhesion, hardness, etc.).

[0073] Table 2 below shows the key performance test results of the coatings on the test specimens coated with the self-drying mirror-back coatings in Examples 1-5 and the conventional mirror-back coatings in Comparative Examples 1-5: Table 2

[0074] Note: Pencil hardness is the average of 4 parallel samples; pigment-to-binder ratio = total solids / (total resin × resin solids content), resin solids content is 55%.

[0075] As shown in Table 2 above, under the same pigment-to-binder ratio, the coating formed by the self-drying mirror back coating of the present invention (Examples 1-5) performs better than that of traditional mirror back coatings (Comparative Examples 1-5) in the following aspects: Adhesion: When the pigment-to-binder ratio is controlled within the range of 2.0-2.5, the cross-cut adhesion of this coating can reach grade 0 (no peeling), which is significantly better than grade 1 (edge ​​peeling area ≤5%) of the coating formed by traditional mirror-back coatings at the same pigment-to-binder ratio. When the pigment-to-binder ratio increases to 3.0 or above, the cross-cut adhesion grade (grade 1 or 2) of this coating is still consistently higher than that of traditional coatings (grade 2 or 3). The pull-out adhesion (1.2-1.5 MPa) of the coating of this invention is also generally higher than that of traditional coatings (1.0-1.3 MPa). Weather resistance: When the pigment-to-binder ratio is between 2.0 and 2.5, the physical and mechanical properties of the coating are maintained at >90% after 720 hours of natural aging at room temperature, and there is no chalking or cracking. As the pigment-to-binder ratio increases to 3.0 and above, although the retention rate gradually decreases from >88% to >82% and slight chalking and cracking begin to appear, its performance retention and appearance integrity are still better than traditional coatings under the same conditions. Pencil hardness: When the pigment-to-binder ratio is controlled within the range of 2.0-3.5, the hardness of the coating stably reaches 3H, which is higher than the 2H of the traditional coating (comparative examples 2-5) under the same conditions; when the pigment-to-binder ratio is 4.0, the hardness of both is 2H.

[0076] 3. Conclusion: Based on the above key performance test results, the overall performance of the self-drying mirror-back coating of this invention is closely related to the pigment-to-binder ratio. When the pigment-to-binder ratio is below 2.5, the self-drying time of the coating is prolonged, the construction efficiency is low, and the production cost is increased; when the pigment-to-binder ratio is above 3.0, the salt spray resistance of the coating formed by the coating is significantly reduced, and the adhesion also tends to weaken. Therefore, controlling the pigment-to-binder ratio within the range of 2.5-3.0 is the preferred solution to achieve the optimal comprehensive balance of various key performances. Within this range, the coating can simultaneously achieve: surface drying time of 3-4 min, adhesion grade 0-1, 24h sedimentation rate <10%, excellent anti-sagging performance (sagging value can reach 125μm), and salt spray resistance time >700h, achieving an excellent and coordinated balance between drying speed, adhesion, storage stability, and construction performance.

[0077] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A self-drying mirror back coating, characterized in that, By weight, it includes the following components: Acrylic-modified alkyd resin: 30-35 parts; Solvent: 8-12 parts; Anti-settling agent: 1-7 parts; Talc powder: 12-15 parts; Colorant: 3 parts; Corrosion inhibitor: 2 parts; Heavy calcium carbonate: 0.5-35.5 parts; Barium sulfate: 20 parts.

2. The self-drying mirror back coating as described in claim 1, characterized in that, The acrylic-modified alkyd resin is obtained by graft copolymerization of short-oil alkyd resin and acrylic monomers accounting for 55 wt.% of the total mass of short-oil alkyd resin. The acrylic monomers are selected from at least one of methyl methacrylate, acrylic acid, butyl acrylate, butyl methacrylate, hydroxyethyl methacrylate, and hydroxyethyl acrylate.

3. The self-drying mirror back coating as described in claim 2, characterized in that, The anti-settling agent is selected from at least one of fumed silica, organobentonite, and polyamide wax; the colorant is selected from at least one of titanium dioxide and zinc barium white; and the corrosion inhibitor is selected from at least one of phosphate, quaternary phosphate, and metal oxide.

4. The self-drying mirror back coating as described in claim 1, characterized in that, The solvent is xylene.

5. A method for preparing a self-drying mirror back coating, used to prepare the self-drying mirror back coating as described in any one of claims 1-4, characterized in that, Includes the following steps: After mixing acrylic-modified alkyd resin and a portion of solvent in a certain proportion, the mixture is stirred thoroughly until homogeneous. Then, anti-settling agent, talc, colorant, corrosion inhibitor, heavy calcium carbonate, and barium sulfate are added sequentially, and the mixture is stirred until homogeneous to obtain a mixture. The mixture is then fully dispersed under high-frequency stirring for 1-3 hours until the fineness reaches ≤25μm. After dispersion, the remaining solvent is added to adjust the viscosity. Finally, the mixture is ground and filtered to obtain a self-drying mirror back coating.

6. The method for preparing the self-drying mirror back coating as described in claim 5, characterized in that, The viscosity is 180-220 s.

7. The method for preparing the self-drying mirror back coating as described in claim 5, characterized in that, The parameters for the high-frequency stirring are: rotation speed 3000 r / min, time 1-2 h.

8. The self-drying mirror back coating prepared by the preparation method according to any one of claims 5-7 is used for coating the back of aluminum mirrors or silver mirrors.

9. A coating, characterized in that, Formed from the self-drying mirror back coating as described in claim 8.

10. The coating as claimed in claim 9, characterized in that, Its dry film thickness is 20-50 μm.

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